 
2018 US Combat Aeroplane Accident Compilation

By Chuan HE

Copyright 2020 Chuan HE

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Chapter 1. Introduction

Combat aeroplanes are complicated piece of engineering in modern technologies. But due to the system complexity, challenging maneuver and weather situations, extreme performance dynamics and complexity of maintenance, there are enormous accidents across the whole history of combat aeroplanes of all countries. The history of combat aeroplane accidents were of mixture of different causes, including design insufficiency, manufacturing problems, maintenance mistakes, human factors, whether challenges, and machine breakdowns, and in some cases a mixture of several factors. The accidents themselves are tragedies and in most cases are expensive, but the analysis following the accidents provides deeper understanding on the aeroplane engineering design, sub-system interaction under fault, human factor impact and protocol effectiveness, thus providing lesson learns to nowadays engineering and manufacturing, with fruitful outcomes with theories of reliability, diagnostic, maintenance, etc., bringing considerations for engineering activities during design and validation phases. Thus the accident reports are valuable piece of work, shedding lights for scientists and engineers in different fields and expertise for the aim to achieve safer and better engineering products of different kinds.

In this compilation, we pick open and public reports from US Air Force official website for aeroplane accidents during 2018, including accidents from man occupied flights and remotely controlled UAVs, selected the most valuable chapters and compiled them together. The reports are arranged in accident date order. Hope anyone who is interested in this topic could benefit from the materials.

Chapter 2. F-16CM Misawa 2018.02.20

F-16CM, T/N 92-3883

MISAWA AIR BASE, JAPAN

LOCATION: MISAWA AIR BASE, JAPAN

DATE OF ACCIDENT: 20 FEBRUARY 2018

On 20 February 2018, at 0838L, an F-16CM, tail number (T/N) 92-3883, during departure at Misawa Air Base (AB), Japan, experienced an engine fire on takeoff during a routine training sortie, necessitating an immediate landing back at Misawa AB. The mishap aircraft (MA) was based at Misawa AB, Japan, and assigned to the 13th Fighter Squadron, of the 35th Fighter Wing. The MA sustained engine damage and loss of external fuel tanks with an estimated governmental loss of $987,545.57.

The mishap flight (MF) consisted of two F-16CM aircraft. The mishap flight's pre-flight, start, and taxi were uneventful until the departure phase of flight. The mishap pilot (MP) departed runway (RWY) 28, fifteen seconds after the mishap lead pilot (MLP). Shortly after the afterburner takeoff, Misawa air traffic controllers informed the MP and the mishap lead pilot (MLP) that the MP had a large flame coming from the aft section of the MP's aircraft. The MLP also contacted the MP regarding the fire. During the MP's ascent, he noticed an unexpected decay in his airspeed and climb rate. The MP took a right turn back towards RWY 28, and when unable to maintain airspeed or altitude, the MP jettisoned his stores (external fuel tanks) in accordance with F-16CM critical actions procedures. Following the jettison, the MA regained some airspeed and achieved a better climb rate to get into a position to land. The MP landed on RWY 28, and accomplished the emergency engine shutdown and emergency ground egress critical action procedures. There were no injuries resulting from the mishap. The MP's actions during the mishap sequence were focused, precise, and appropriate; his actions did not contribute to the mishap. A review of maintenance procedures revealed several past actions that were causal to the accident.

The AIB President found by a preponderance of the evidence that the cause of the accident was an obsolete part that fractured, causing the engine to overheat. In 2012, maintenance personnel ordered and installed an obsolete part, a turbine frame forward fairing, years after it was replaced by a forward fairing made of stronger material and design. The logistics system then delivered the obsolete forward fairing. Maintenance personnel installed the obsolete forward fairing on the mishap engine (ME) using the updated version of the bracket hardware. The obsolete forward fairing's weaker material, along with wear from the mismatched hardware, ultimately caused the forward fairing to fracture during takeoff. Once fractured, a piece of the forward fairing lifted and blocked the cooling flow of air around the engine, causing the area near the blockage to overheat and catch fire. The AIB President further found by a preponderance of the evidence that maintenance practices during the 2012-2015 timeframe substantially contributed to the mishap.

Chapter 2.1. ACCIDENT SUMMARY

The mishap aircraft (MA), an F-16CM, T/N 92-3883, assigned to the 13th Fighter Squadron located at Misawa AB, Japan, flown by the mishap pilot (MP), departed and landed at Misawa AB on 20 February 2018. The MP experienced an engine fire on takeoff during a routine training sortie, necessitating an immediate landing. The MP jettisoned his fuel tanks in accordance with the F-16 flight crew checklist.

There were no injuries; the mishap engine (ME) was impounded. Damage to the MA totaled $987,545.57.

Chapter 2.2. SEQUENCE OF EVENTS

a. Mission

The mishap mission (MM) was planned and briefed without incident and had a valid flight authorization. The MM involved two F-16CM aircraft.

b. Planning

Flight products for the MM were produced the day of the flight by the MP before the mass briefing. Prior to the MM, all flight members attended a mass briefing conducted by the squadron operations supervisor. The mass briefing adequately covered forecasted weather conditions, notices to airmen (NOTAMs), and other routine items. The mishap lead pilot (MLP), the pilot in charge of the formation, also conducted a coordination brief and a tactical brief for the MM.

c. Preflight

After the flight briefings, the personnel involved in the MM assembled at the 13 FS operations desk and received an update from the operations supervisor prior to proceeding to their assigned aircraft. During this brief, the operations supervisor provided updated information on items pertinent to flying that day and assigned them their aircraft. The MP noted no discrepancies upon inspection of his aircrew flight equipment. The MP's preflight inspection, engine start procedures, and ground operations were uneventful.

Mishap Flight Summary:

The MP reported no issues during taxi. The MP took off at 0838L in afterburner, fifteen seconds behind the MLP. Shortly after the MP became airborne, the tower controllers and the supervisor of flying noticed a large twenty to thirty-foot flame coming from the engine at the back of the MP's aircraft.

Upon seeing the flames, the tower controllers informed the MP of the fire. The MP did not hear this radio call, but the MLP did. Upon hearing the radio call, the MLP made a right turn to rejoin with the MP and visually confirm the fire. The MLP then informed the MP of the fire and told the MP to make a right turn to a position where the MP could reach the runway and land if the engine failed, known as a key position. At this point, the MP acknowledged the MLP's statements and began to ascend to a key position. During the ascent, the MP was only able to gain a fraction of the airspeed that he typically could have gained.

In trying to reach a key position, the MP started a right turn back towards the runway, and was able to achieve the minimum controlled ejection altitude of two-thousand feet above ground level. During this turn, the MP, unable to retain his airspeed or gain sufficient altitude, decided he needed to emergency jettison his external fuel tanks. Before jettisoning his fuel tanks, the MP checked the area below to ensure it was uninhabited. After confirming he was over an uninhabited area, the MP jettisoned his fuel tanks, which impacted Lake Ogawara. This jettison was in accordance with the F-16 fire-in-flight critical action procedures and local area procedures. Jettisoning the external fuel tanks made the MA lighter, allowing the MP to gain airspeed and altitude, and require less distance for landing. The MLP observed the fuel tank jettison and electronically marked the point where the fuel tanks fell.

After jettisoning his fuel tanks, the MP asked the MLP if there was still a fire. The MLP replied that he still saw smoke trailing the MA. The MP then tested the fire/overheat light in the MA, ensuring that it was functioning properly.

The MP then scanned his engine instruments and noticed the engine nozzle reading was incorrect for his power setting. The MP communicated his nozzle reading to the MLP and asked the MLP if there was still a fire. The MLP stated that there were puffs of smoke still trailing the MA. At this point, the MP assessed that he was no longer on fire. The MP reached a key position and accomplished a safe landing. He then stopped on the runway and accomplished the critical action procedures for both emergency shutdown and emergency ground egress.

Mishap Engine Summary:

The Mishap Engine (ME) is a General Electric (GE) F110129 with serial number GE0E538133 (538133).

The cause of the mishap was an uncontained engine fire. This fire was directly caused by the installation of an obsolete turbine frame forward fairing that was known to be susceptible to failure. Specifically, in August 2007, safety Time Compliance Technical Order 2J-F110129-682 (TCTO-682) dictated replacement across the fleet by August 2010 of this susceptible fairing, along with its attaching hardware. The susceptible fairing then became obsolete, as it was replaced with an updated fairing of improved material and design. The fairing was made up of three titanium segments that connect, creating a ring that lines the forward outer section of the turbine frame. While the redesign was still comprised of the three segments, wear brackets and sacrificial wear strips were added onto the fairing. The redesign also included the use of a more durable material for the existing wear pads on the top and bottom of the fairing.

The ME had the updated fairing properly installed in accordance with TCTO-682 on 03 June 2010. However, the updated fairing was later re-replaced with an obsolete fairing during engine maintenance in 2012. The updated wear brackets exacerbated wear into the fairing, ultimately leading the fairing to fracture during takeoff of the MA. Portions of the fractured fairing then lifted into the cooling airstream of the engine, blocking essential cooling air to the exhaust nozzle liner and other downstream components. Without the exhaust liner to contain the hot gases from the exhaust, the heat burned through the exhaust duct to the exterior of the engine causing a fire. This fire caused extensive damage to the engine's rear components.

Removal of the forward fairing from the ME revealed wear from the updated mounting brackets that were installed underneath the turbine frame fairing. In several locations, these brackets had worn completely through the fairing. Both fractures emanate from areas where the wear brackets had worn completely through the fairings.

The absence of the wear strips on the obsolete fairing created a material mismatch between the relatively soft titanium fairing and the hardened composite material wear brackets. This exacerbated the wear on the fairing and, in many areas, caused a complete wear-through at these contact points. The exhaust duct liner and the exhaust duct were burned completely through at the 4:30 position as a result of the fire. In normal engine operation, a film of cooling air exists between the exhaust nozzle duct and the exhaust nozzle liner. This air lowers the metal temperature of the exhaust duct liner during engine operation. Without proper cooling air, the liner cannot withstand the temperatures of the hot engine gases from the exhaust.

The fire also caused the A8 actuator supply line at the 4:30 position to rupture and leak hydraulic oil. The A8 actuators control the diameter of the nozzle during normal flight operations. Decreasing the diameter of the nozzle allows the engine to produce thrust. With the A8 actuators' hydraulic line ruptured, the MP was unable to decrease the diameter of the nozzle, creating a noticeable decrease in engine thrust.

e. Impact

Not applicable.

f. Egress and Aircrew Flight Equipment (AFE)

The MP ground egressed without incident on the runway. AFE was not used during ground egress.

g. Search and Rescue (SAR)

Not applicable.

h. Recovery of Remains

Not Applicable.

Chapter 2.3. MAINTENANCE

a. Forms Documentation

Air Force Technical Order (AFTO) Form 781 collectively documents maintenance actions, inspections, servicing, configuration, status, and flight activities for the aircraft. Integrated Maintenance Data System (IMDS) is a comprehensive database used to track maintenance actions, flight activity, and schedule future maintenance. Comprehensive Engine Management Systems (CEMS) is a comprehensive database used to track engine parts, maintenance, and inspections.

A review of Air Force Technical Order (AFTO) Form 781 revealed no discrepancies indicating any noticed mechanical or flight control anomalies, or any structural or electrical failure on the MA. IMDS historical records were reviewed 10 years prior to the MM and CEMS records were reviewed for the 8 years prior to the MM. A review of the historical records also confirmed that no TCTO were overdue at the time of the MS.

b. Inspections

The MA had 7,192.1 total flight hours at the time of the mishap. The GE F-110129 engine, serial number GE0E538133, installed in the MA had 4,976.6 Flying Hours (FHR) total.

Technical Order (TO) 1F-16CJ-6-11 mandates an 800 Engine Flight Hour (EFH) Exhaust Nozzle Inspection which requires a borescope camera be used to get a detailed view of the forward fairing. This inspection requires the use of a borescope camera that has digital measurement capability. The inspector is required to check the full circumference of the forward fairing to look for cracks, loose/missing hardware, and wear on the forward end of the fairing. In the inspection, maintainers must ensure the fairing has a thickness of at least .040 millimeters; if not, maintainers must replace the fairing. Historical evidence has shown that the wear on the fairing gets worse with time and generally fails at .010 and .020 millimeters. The borescope inspection was last performed on the ME and the mishap forward fairings on 06 July 2016, when the mishap forward fairing had been on the ME for 373 flight hours. The historical data indicates the forward fairings were cracking after the fairings had endured approximately 700 to 900 hours, so it is unsurprising that the 06 July 2016 borescope inspection did not indicate a potential problem with the mishap forward fairings.

In addition to the 800 EFH inspection, TO 1F-16CJ-6-11 requires a naked eye inspection of the aircraft and its forward fairing, each time an aircraft takes off and lands. The Preflight (PR) inspection is conducted before takeoff and the Basic Post flight (BPO) is conducted when the aircraft lands. Among other potential issues, these inspections are designed to find major damage to the fairing, such as liberated pieces that have lifted into the air stream. Maintenance personnel accomplish these inspections by crawling inside of the exhaust nozzle and using a bright light to look at the forward fairing, among other areas. Given the inward position of the forward fairing, it is highly unlikely that this inspection would reveal minuscule wear on the fairing, as the viewer is unable to get physically closer than 18 to 24 inches from the fairing. The most recent of these inspections on the MA were PR/BPO completed at 1335L on 16 February 2018, PR completed at 1600L on 17 February 2018, and a WAI completed at 0100L on 20 February 2018.

The reviewed maintenance documentation confirmed that maintenance personnel accomplished all required scheduled inspections in accordance with applicable directives and that improper inspections did not contribute to the mishap.

c. Maintenance Procedures

Maintenance procedures are described in applicable Technical Orders (TO), Air Force Instructions (AFI), and local procedures.

Maintenance procedures were properly followed on the ME when complying with TCTO-682 on 3 June 2010, indicating that the updated fairing and hardware were installed correctly at that time. This is indicated by the fact that the parts required to complete TCTO-682 were issued as a complete kit and that the correct attaching hardware for that TCTO was found to be installed on the date of the mishap. However, inspection of the ME after the mishap revealed that all three segments of the fairing were the obsolete versions.

The only events that would drive removal or replacement of the forward fairing is if the fairing was damaged (discovered during inspection), if a turbine frame assembly required removal, or if a low pressure turbine (LPT) assembly required removal. The following timeline details the only recorded events after 3 June 2010 when the forward fairing would have been removed or exposed for close visual inspection:

1. 23 November 2010 - 07 January 2011: LPT Rotor Assembly Removed/Reinstalled

2. 03 March 2012: ME removed from A/C 91-0411 for turbine nozzle damage and TCTO 2J-F110129-659 mandates a Structural Life Extension Program (SLEP). On 12 March 2012, the LPT Rotor Assembly was removed from the engine. The pre-TCTO forward fairings were ordered on 16 March 2012. On 24 September 2012, the LPT Rotor Assembly was reinstalled, and on 02 October 2012, the SLEP was completed.

3. 12 -13 February 2013: Augmenter/Exhaust Assembly Removed/Reinstalled.

While the augmenter/exhaust assembly was replaced on 12 February 2013, there is no mention in CEMS that the fairing was removed during that action. Therefore, the last recorded maintenance activity where the forward fairing and its respective brackets and hardware were installed would have been on 24 September 2012 during installation of the LPT Rotor Assembly during the SLEP upgrade of the engine. A SLEP is a major engine overhaul that includes the complete teardown of the engine.

During the SLEP, on 16 March 2012, the 35 MXS Propulsion Flight ordered three obsolete segments that comprise the forward fairing. The signatures on the issuing forms for these three segments, which would have shown who specifically received the obsolete parts, are illegible. The Propulsion Flight's Jet Engine Intermediate Maintenance (JEIM) section then installed three obsolete segments comprising the forward fairing onto the ME using the updated brackets and hardware. In accordance with standard procedures, this installation and the corresponding records were reviewed by at least one supervising technician that failed to catch the error.

During the 2012-2015 timeframe, the JEIM section had poor enforcement of standard maintenance protocols. This created an environment that tolerated: improper completion of paperwork to ensure parts accountability, severe disorganization at the shop, and the improper handling of parts, including a failure to separate serviceable and unserviceable parts, and failure to follow proper procedures for cannibalization (CANN) actions.

Witness testimony indicates that the work section was significantly disorganized during that period. The shop possessed substandard accountability and tracking of engine parts during extensive engine teardowns and rebuilds. A Report of Survey (ROS) provides insight into the flight's environment in 2012. Witness testimony and maintenance documentation from ROS #15-033 indicates the Propulsion Flight failed to properly document maintenance actions, with one example showing they entered information into a tracking system to indicate a particular Airman removed a part, while also entering information into a separate tracking system indicating that a different Airman removed the same part. This ROS also indicates that a part worth $3K was likely misidentified and turned in for scrap. A second ROS detailing practices from 2013 to 2015 further supports that this Propulsion Flight had a history during 2012 of poor paperwork and accountability as it discussed a search for $322K worth of parts, most of which eventually turned up on aircraft across the world without any documentation to show how it left the Propulsion Flight. This ROS also discussed parts that had likely been misidentified and turned in as scrap, or sent to headquarters for repair or redistribution.

In 2015, the propulsion shop was in disarray, as there were no parts shelves, excess parts and boxes were left in the work area, there were old bins of material, and there was "stuff everywhere" without much organization. This deviates from standard protocols since building a motor takes "details, parts, and room." It was "mix and match," with no standardization of where things went. There was no designated area to put a turbine frame. The shop had their own "method of the madness". Given these departures from standard protocols, the propulsion shop received a half million dollars to revamp the shop, in order to get the shop back up to standards.

According to the 35 MXS Commander from 2013-2015, the shop was known to have disorganized accountability practices where serviceable and non-serviceable parts were stored in the same area. Additionally, protocols regarding cannibalization (CANN), when maintenance personnel could take a serviceable part off one piece of equipment to use on another, were not enforced. This led to CANN procedures in 2012 that were not precise or were happening below the authorized authority level. The documentation for these actions was also not completed properly. Certain flights had little or no supervision involved in their processes. A part that should have been carefully tracked, was likely misidentified and turned in as scrap metal. A similar report, for different parts, found that several parts were removed and installed on other engines without proper documentation or authorization.

35 MXS Propulsion Flight procedures have since been corrected and continuously improved upon by supervision and personnel. Supervision and personnel are currently operating within guidelines set forth by the AFIs, TOs, and local procedures.

d. Maintenance Personnel and Supervision

AFI 36-2650, Maintenance Training, 20 May 2014, Chapter 3, provides the requirements for documenting maintenance training, and a review of the records of personnel who serviced or maintained the systems of the MA indicated proper training and full qualifications on all tasks accomplished. As such, there is no evidence to suggest that personnel qualifications were a factor in the mishap.

However, inadequate supervision was a factor in the mishap. While personnel and training records did not reveal inadequate supervision, witness testimony and other documentation of the Propulsion Flight's environment from 2012-2015 did indicate poor enforcement of standard maintenance protocols that was a substantially contributing factor to the order and installation of the obsolete forward fairing.

e. Fuel, Hydraulic, Oil, and Oxygen Inspection Analysis

Laboratory tests determined that Jet Propellant-8 (JP-8) aviation turbine fuel, hydraulic fluid, and aircraft engine oil samples taken post-accident from servicing equipment were within limits and free of contamination.

f. Unscheduled Maintenance

A review of the MA's performance for the 90-day period prior to the MS, revealed 48 of 53 sorties flown landed either Code I (fully mission capable) or Code II (with minor discrepancies, partially mission capable) and zero repeats or recurs. According to AFI 21-101, Aircraft and Equipment Maintenance Management, 21 May 2015, a repeat discrepancy is defined as a discrepancy that occurs on the next sortie or attempted sortie after corrective action has been taken and the system or sub-system indicates the same malfunction when operated. A recurring discrepancy is one that occurs on the second through fourth sortie or attempted sortie after corrective action is taken and the system or sub-system indicates the same malfunction when operated.

The MA flew 53 sorties in the 90 days prior to the MS and received five Code III discrepancies that rendered the aircraft non-mission capable. These discrepancies did not involve any systems pertaining to the MS, and are not significant to this investigation.

g. Time Compliance Technical Orders (TCTO)

TCTOs are the authorized method of directing and providing instructions for modifying military systems and end items or performing one-time inspections. Historical records showed that all required TCTOs had been accomplished on the ME in accordance with applicable guidelines.

The primary TCTO at issue here, TCTO-682, was driven by the fact that during the early to mid-2000 timeframe, both the U.S. Air Force and foreign military operators of the F110129 engine began experiencing excessive wear, cracking and, in a few cases, failure of the turbine frame forward fairing. Most of these fairings were found to be wearing on the front end where they would become thin, crack, and sometimes fail.

Chapter 2.4. AIRFRAME, MISSILE, OR SPACE VEHICLE SYSTEMS

a. Flight Controls

The flight controls operated normally during the mishap.

b. Avionics/Communications

Maintenance fault lists (MFLs) and pilot fault lists (PFLs) are indications of aircraft discrepancies displayed in the cockpit. The MA had no grounding MFLs or PFLs prior to the MS. The MA had the following PFLs during the MS: 18 (Augmenter Inhibit), 19 (Hybrid Mode), and 43 (A8 Hydraulic Pump). All three PFLs were directly related to the augmenter burn through.

c. Hydraulic System

The hydraulic system operated normally during the mishap.

d. Fuel System

The fuel system operated normally during the mishap.

e. Electrical System

The electrical system operated normally during the mishap.

f. Life Support and Egress

The life support and egress systems operated normally during the mishap.

g. Oil System

The engine was operating upon landing and the Joint Oil Analysis Program (JOAP) sample came back within the acceptable range to indicate no problems with the engine bearings. The oil was drained and it was determined that an adequate amount was present even with oil loss during the MS.

h. Engine

The Mishap Engine (ME) E538133 received TCTO-682 (Turbine Frame Outer Fairings Upgrade) on 03 June 2010 at Spangdahlem AB, Germany, with 3550.6 hours of inflight time (IFT) recorded from the engine. A major engine overhaul event, known as Service Life Extension Program (SLEP), was conducted at Misawa AB, Japan from 03 March 2012 to 02 October 2012, with 3788.3 IFT. It was during this overhaul that the ME was completely disassembled, inspected, had parts replaced or reinstalled, and was tested while it was uninstalled on an aircraft at a test facility.

i. Landing Gear

The landing gear operated normally during the mishap.

Chapter 2.5. WEATHER

a. Forecast Weather

The weather forecast for the MS predicted few clouds at 2,000 feet and scattered clouds at 3,000 feet. The term "few" refers to cloud layers that cover up to 25% of the sky and the term "scattered" refers to cloud layers that cover less than 50% of the sky. The visibility was forecast to be seven statute miles. The wind was forecast to be 270 degrees at eight knots.

The weather in the mission airspace was forecast to have a scattered to broken cloud layer from 3,000 to 8,000 feet. The term "broken" refers to cloud layers that cover more than 50% of the sky.

b. Observed Weather

The weather at Misawa AB at 0900L, twenty-one minutes after the mishap, was reported as unlimited visibility with winds from 260 degrees at twelve knots.

c. Space Environment

Not applicable.

d. Operations

The MS was conducted in accordance with all applicable operational weather regulations.

e. Conclusion

There is no evidence to suggest weather was a factor in the mishap.

Chapter 2.6. HUMAN FACTORS ANALYSIS

a. Introduction

The board evaluated human factors relevant to the mishap using the analysis and classification system model established by the Department of Defense (DoD) Human Factors Analysis and Classification System (HFACS) guide, Version 7.0, implemented by Air Force Instruction AFI 91-204, USAF Safety Investigations and Reports, dated 19 January 2018. Human factors describe how our interaction with tools, tasks, working environments, and other people influence human performance. The DoD created a model to engage in a systematic, multidimensional approach to error analysis and mishap prevention.

The framework is divided into four main categories: Organizational Influences, Supervision, Preconditions, and Acts. Each category is further divided into related human factor categories which are further divided into subcategories. The main categories allow for a complete analysis of all levels of human error and how they may interact together to contribute to a mishap. This framework allows for evaluation of any unsafe acts that are directly related to the mishap by considering the indirect preconditions, supervision, or organizational influences that may have led to the mishap. The relevant factors to this mishap are discussed below.

b. Human Factors

Organizational Influences: Organizational influences are defined as factors in a mishap if the communications, actions, omissions, or policies of upper-level management directly or indirectly affect supervisory practices, conditions, or actions of the operator(s) and result in system failure, human error, or an unsafe situation. Following review of all testimonies and mishap data, the AIB found some organizational influences that were contributory to the mishap.

Resource Problems (OR000): are factors when processes or polices influence the safety system, resulting in inadequate error management or creating an unsafe situation. Following review of all testimonies and mishap data, the AIB found some resource problems that were significant to the mishap. Below is a discussion and analysis of resource problems that the board felt were significant to the mishap.

Failure to Remove Inadequate/Worn-Out Equipment in a Timely Manner (OR005): is a factor when the process through which equipment is removed from service is inadequate. As discussed in Section 5 of this report, the Air Force released TCTO-682 mandating that all forward fairings on the F110129 engine be replaced with updated forward fairings, after it determined that the forward fairing was showing excessive wear and cracking. The TCTO directed that the replacements must occur by 07 August 2010, and that the removed fairings be disposed. However, when the ME underwent a SLEP upgrade in 2012, Propulsion Flight personnel were still able to order at least one segment of the obsolete forward fairing through the supply system, even though the Air Force had officially rescinded that part almost two years prior. Ultimately, the re-installation of the obsolete forward fairing and the wear caused by the updated hardware, was the direct cause of the mishap.

Supervision: Supervision is defined as a factor in the mishap if the methods, decisions, or policies of the supervisory chain of command directly affect practices, conditions, or actions of the individual and result in human error or an unsafe situation.

Supervisory Violations (SV000): are factors when supervisors willfully disregard instructions or policies. Following a review of witness testimonies and mishap data, the AIB determined that failed supervisory influences substantially contributed to the mishap. Below is a discussion and analysis of supervisory violations significant to the mishap.

Failure to Enforce Existing Rules –Supervisor Act of Omission (SV001): is a factor when unit (organizational) and operating rules have not been enforced by a supervisor.

Maintenance supervision failed to enforce several operating rules during the timeframe associated with the order and installation of the obsolete forward fairing. The first rule supervision failed to enforce was the proper completion of paperwork to ensure parts accountability, resulting in $322K in unaccounted parts. Second, supervision failed to enforce and ensure a physically-organized work environment. Third, supervision failed to enforce proper parts handling, to include maintaining serviceable and unserviceable parts separate, and ensuring those allowing cannibalization (CANN) actions have the proper authority to do so and are properly documenting those actions. This failure to enforce operating rules created an environment of unenforced rules and protocols, in a squadron that must be fastidious when following technical orders, as a failure to do so can result in the ordering of an obsolete part. Supervision's failure to enforce existing rules was a contributing factor to the mishap.

Preconditions (Environment): The environment surrounding a mishap is the physical or technological factors that affect practices, conditions, and actions of individual(s) and result in human error or an unsafe condition. Following a review of witness testimonies and mishap data, the AIB determined environment was significant to the mishap.

Technological Environment (PE200): are factors when automation or the design of the workspace affect the actions of an individual(s). A review of witness testimonies and mishap data revealed some haphazard environmental preconditions that were contributory to the mishap. Below is a discussion and analysis of environmental preconditions that the board felt were significant to the mishap.

Workspace Incompatible with Operation (PE206): is a factor when the workspace is incompatible with the task requirements and safety for an individual. During the 2012 timeframe when the obsolete forward fairing was ordered and installed, the Propulsion Flight was severely disorganized. There were no part shelves, there were excess parts and boxes in the work area, old bins, and "stuff everywhere." While the shop had its "method of the madness," there was not a lot of organization. An engine takes "details, parts, and room." The Propulsion Flight did not have that. Additionally, each engine dock station was mixed and matched, with no standardization between dock stations for where items should go. This haphazard maintenance environment contributed to the mishap.

Acts: The environment surrounding a mishap is the physical or technological factors that affect practices, conditions, and actions of individual(s) and result in human error or an unsafe condition. Following a review of witness testimonies and mishap data, the AIB determined failure to follow procedures were casual to the mishap.

Procedure Not Followed Correctly (AE103): is a factor when a procedure is performed incorrectly or accomplished in the wrong sequence. When Propulsion Flight personnel ordered and installed the obsolete forward fairing in 2012, the current TO clearly indicated, right next to the part number for the forward fairing, that a TCTO had rescinded the previous part number. The updated part number for the updated forward fairing was listed along with the rescission information. If the maintenance personnel had properly referenced the TO or used the part number from the part the maintenance personnel was removing, the correct part would have been ordered. There are two alternatives to explain how the obsolete fairing was ordered: 1) maintenance personnel referenced the TO and they unreasonably did not see the note indicating the part had been replaced, or 2) maintenance personnel used a unit-created Quick Reference List (QRL) to look up the part number and the QRL had not been updated since 2010 to reflect the new part number. Either of these alternatives indicate that maintenance personnel were not following proper procedures when ordering the replacement forward fairing during the 2012 SLEP upgrade. This failure to follow procedures contributed to the mishap.

Chapter 2.7. STATEMENT OF OPINION

1. OPINION SUMMARY

I find by a preponderance of the evidence that the mishap aircraft (MA) experienced an engine fire shortly after take-off from runway (RWY) 28 at Misawa Air Base (AB), Japan because an obsolete turbine frame forward fairing on the mishap engine (ME) failed during takeoff. Evidence collected from the Crash Survivable Flight Data Recorder (CSFDR) and the ME, to include the augmenter/exhaust nozzle assembly, indicate the turbine frame forward fairings failed. During the mishap pilot's (MPs) takeoff, the installed turbine forward fairing segment fractured, causing portions of the fairing to lift into the cooling airflow between the exhaust liner and the flame produced by the afterburner. Without the cooling air, the exhaust liner and the downstream components were exposed to temperatures beyond their heat tolerance, resulting in a fire.

The obsolete forward fairings had previously been called to be replaced by Time Compliance Technical Order 2J-F110129-682 in 2007. TCTO-682 required that all obsolete forward fairings be replaced with fairings made of a stronger composite material and updated design which included wear strips. TCTO-682 required all titanium forward fairings be replaced by 07 August 2010. Although the ME had its obsolete fairings properly replaced in 2010, the updated fairings were later erroneously re-replaced with the obsolete fairings during an engine Service Life Extension Program (SLEP) in 2012. The obsolete fairing had been on the ME for approximately 760 flight hours when it failed.

The Heads Up display (HUD) video, Crash Survivable Flight Data Recorder (CSFDR), tower transcripts, and a review of the Supervisor of Flight (SOF), mishap lead pilot (MLP), and MP's testimony, confirms the MP flew and landed the MA in accordance with flight manual and critical action procedures. The MP emergency jettisoned his fuel stores in accordance with the F-16CM fire-in-flight critical actions procedures. The MP's actions during the mishap flight were focused, precise, and appropriate; his actions did not contribute to the mishap.

The MA sustained engine damage and loss of external stores, which contained fuel. While not the cause, I find by a preponderance of the evidence that the haphazard practices by the maintenance Propulsion Flight during 2012 were a substantially contributing factor to the mishap.

I developed my opinion by analyzing factual data from historical records, guidance and directives, engineering analysis, witness testimony, and information provided by technical experts.

2. CAUSE

The cause of the 20 February 2018 engine fire was due to the installation of obsolete forward fairings which were susceptible to failure. TCTO-682 was released in 2007 requiring titanium forward fairings that had been failing to be replaced with stronger redesigned forward fairings. TCTO-682 required replacement of all titanium forward fairings with enhanced forward fairings by 07 August 2010. It also required the installation of improved brackets as well. Both required maintenance items were completed on the ME on 03 June 2010. I believe the TCTO was actually completed in June 2010 because of proper documentation in the maintenance paperwork, the fact that the updated parts were issued as a complete kit, and that the correct attaching hardware for that TCTO was installed on the date of the mishap.

During a SLEP upgrade of the ME at Misawa AB, Japan, between March and October 2012, 35th Maintenance Squadron (35 MXS), Propulsion Flight, Jet Engine Intermediate Maintenance (JEIM) personnel, erroneously ordered the obsolete titanium forward fairing, instead of the updated enhanced forward fairing. The logistics supply system allowed at least one segment of the obsolete forward fairing to be ordered and delivered, despite the obsolete status of the part. A DD Form 1348-1A Issue and Release document shows the Propulsion Flight ordered the obsolete segments on 16 March 2012. The names of the maintainers that received the parts are illegible.

Once received, JEIM personnel installed the obsolete titanium fairing with the improved brackets. Over time, the post-TCTO brackets exacerbated wear into the fairing, causing it to fracture during the MA's afterburner takeoff on 20 February 2018. During takeoff, the failed forward fairing remained attached on one end, which caused the fractured portion to lift into the cooling airstream of the engine, disrupting essential cooling air to the exhaust nozzle liner and other downstream components. The exhaust liner, in turn, failed, allowing the afterburner flame to burn through the exhaust duct to the outside of the engine. The resulting fire was observable from the ground and caused extensive damage to the downstream exterior engine components. Since the obsolete titanium fairings were new at the time of installation, they would have accumulated 760 flying hours on the day of the mishap.

The only events that would drive removal of the turbine frame forward fairings would be if the fairing was damaged (discovered during inspection), if a turbine frame assembly required removal, or if a low pressure turbine (LPT) assembly required removal. The following details the only recorded events after TCTO-682 was completed when the forward fairing would have been either exposed or been removed/reinstalled:

1. 23 November 2010 - 07 January 2011: LPT Rotor Assembly Removed/Reinstalled

2. 03 March 2012: ME removed from A/C 91-0411 for turbine nozzle damage and TCTO 2J-F110129-659 mandates a Structural Life Extension Program (SLEP). On 12 March 2012, the LPT Rotor Assembly was removed from the engine. The pre-TCTO forward fairings were ordered on 16 March 2012. On 24 September 2012, the LPT Rotor Assembly was reinstalled, and on 02 October 2012, the SLEP was completed.

3. 12 -13 February 2013: Augmenter/Exhaust Assembly Removed/Reinstalled.

While the augmenter/exhaust assembly was replaced on 12 February 2013, there is no mention in the Comprehensive Engine Management System (CEMS) that the fairing was removed during that action. Therefore, the last recorded maintenance activity where the forward fairing and its respective brackets and hardware were installed, would have been on 24 September 2012 during installation of the LPT Rotor Assembly during the SLEP upgrade of the engine. The obsolete forward fairing has been on the ME since this time, and has not been removed since.

After an in-depth review of the inspection process, I find that the routine inspections conducted on the engine would not have revealed that the incorrect forward fairing was installed or that excessive wear was occurring. The only inspection that was required to be conducted that could have caught the excessive wear was the 800-hour borescope inspection. However, the last 800 hour borescope inspection occurred when the forward fairing had only endured 376 flight hours, a point at which the forward fairing was unlikely to show signs of excessive wear.

3. SUBSTANTIALLY CONTRIBUTING FACTOR: MAINTENANCE PRACTICES

A preponderance of the evidence shows that during the 2012 timeframe, when the obsolete fairing was installed, there was poor enforcement of standard maintenance protocols, which was a substantially contributing factor to the mishap. Poor enforcement of standard protocols led to a failure to follow protocols when ordering and installing the obsolete forward fairing. Specifically, poor enforcement of standard maintenance protocols created an environment that tolerated improper completion of paperwork to ensure parts accountability, severe disorganization at the shop, the improper handling of parts--including a failure to separate serviceable and unserviceable parts, and failure to follow proper procedures for cannibalization (CANN) actions. Given these significant departures from standard protocols, I find that the shop had an environment conducive to failing to follow protocols when ordering and replacing parts.

The Propulsion Flight's poor enforcement of standard maintenance paperwork and accountability protocols is highlighted in one of its Reports of Survey (ROS) that discusses the flight's environment in 2012. During this period, through personal interviews and witness testimony, the Propulsion Flight demonstrated haphazard documentation and parts accountability. The ROS indicates the flight failed to properly document maintenance actions, with one example showing they entered information into a tracking system to indicate a particular Airman removed a part, while also entering information into a separate tracking system indicating that a different Airman removed the same part. This ROS also indicates that a part worth $3K was likely misidentified and turned in for scrap. A second ROS detailing practices from 2013 to 2015 further supports that this Propulsion Flight had a history during 2012 of poor paperwork and accountability, as it discusses a search for $322K worth of parts, most of which eventually turned up on aircraft across the world, without any documentation to show how it left the Propulsion Flight. This ROS also discusses parts that had likely been misidentified and turned in as scrap or sent to headquarters for repair or redistribution. While the second ROS concerns the timeframe immediately following the incorrect ordering and installation of the obsolete fairing, it is reasonable to conclude the same haphazard maintenance procedures that were occurring during this timeframe were holdovers from 2012, based on the similarity of the personnel involved and the descriptions of the Propulsion Flight's environment.

Multiple witnesses detailed the Propulsion Flight's poor enforcement of standard maintenance organization. When one Senior Noncommissioned Officer arrived in 2015, he found the propulsion shop was in disarray, as there were no part shelves, excess parts and boxes were left in the work area, there were old bins of material, and that there were items everywhere without much organization. This deviates from standard protocols since building an engine takes details, parts, and space; and the Propulsion Flight did not have that. It was mix and match, with no standardization of where things went. The shop had their own "method of the madness." Given these departures from standard protocols, the propulsion shop received a half million dollars to revamp the shop, in order to get the shop back up to standards.

The Propulsion Flight's poor enforcement of standard maintenance protocols resulted in improper handling of parts including a failure to separate serviceable and unserviceable parts, and failure to follow proper procedures for cannibalization (CANN) actions. According to the 35 MXS Commander from 2013-2015, the shop was known to have disorganized accountability practices where serviceable and non-serviceable parts were stored in the same area. Additionally, protocols regarding when maintenance personnel can take a serviceable part off of one piece of equipment to use it on another, known as cannibalization (CANN), were not enforced, so CANN procedures were not precise or were happening below the authorized authority level (SNCO) in 2012. The documentation for these actions was also not completed properly. This failure to enforce procedures likely resulted from certain flights having little or no supervision involved in their processes. Further, a report that investigated unaccounted-for parts indicates that a part that should have been carefully tracked was likely misidentified and turned in as scrap metal. A similar report for different items, found that several items were removed and installed on other engines without proper documentation or authorization.

While there is not direct documentation of other incorrectly ordered parts during this time period, the general disarray of the shop, poor parts accountability, the intermingling of serviceable and unserviceable parts, and failure to follow standard protocols (CANN), indicate an environment of poor enforcement of standard maintenance protocols in 2012. Given the strict protocols governing how parts are ordered and installed, a preponderance of the evidence shows the poor enforcement of standard maintenance protocols in 2012 created an environment within the Propulsion Flight that was a substantially contributing factor to the order and installation of the obsolete forward fairing that caused the fire.

4. CONCLUSION

I find by a preponderance of the evidence that the primary cause of the accident was the mishap engine (ME) had an obsolete forward fairing which failed, resulting in an engine fire shortly after takeoff. I further find by preponderance of the evidence that the haphazard maintenance practices in the Propulsion Flight during the 2012 period substantially contributed to the mishap where rescinded forward fairing parts were ordered by the Propulsion Flight's (JEIM) section and installed on the ME.

Chapter 3. HH60G Centcom 2018.03.15

HH-60G, T/N 92-6466

USCENTCOM AOR

LOCATION: USCENTCOM AOR

DATE OF ACCIDENT: 15 March 2018

On 15 March 2018, at approximately 1840 Zulu time (Z), 2140 Local time (L), the mishap aircraft (MA), an HH-60G, Tail number (T/N) 92-6466, assigned to the 332nd Air Expeditionary Wing (AEW), and operating within the USCENTCOM AOR, crashed in an uninhabited desert area. Four MA flight crew members and three members of the Guardian Angel team were fatally injured in the mishap. The MA was destroyed upon impact, there were no other injuries or fatalities, and there was no damage to private property.

The mishap formation (MF) consisted of two HH-60G helicopters, with the MA operating as the lead aircraft and the mishap wingman as the trail aircraft. The assigned mission was to pre-position the MF to a helicopter landing zone (HLZ) closer to the vicinity of ground operations. The flight plan for the pre-position mission was a near direct path from the base of departure to the intended HLZ with an air refueling control point between the origin and destination points. A more extensive route of flight was loaded to the navigation system for potential follow on mission taskings, but it was not to be utilized on this mission. The loaded navigation route continued north to points beyond the intended HLZ. Night illumination for the flight was low.

The MF departed the base at approximately1800Z. The flight up to air refueling was uneventful, but refueling operations concluded later than planned. While conducting normal crew duties, the MF erroneously overflew the intended HLZ and descended to low altitude. As the mishap co-pilot turned left to avoid a tower, a blade on the MA's main rotor assembly struck the second of four 3/8 inch galvanized steel cables horizontally spanning two 341-foot towers. The cable tangled around the main rotor assembly resulting in catastrophic damage, rendering the aircraft un-flyable. The MA impacted the ground at approximately 1840Z. An extensive rescue operation was immediately conducted.

The Accident Investigation Board (AIB) president found by a preponderance of evidence the cause of the mishap was the result of: the mishap pilot misinterpreting aircraft navigation displays, causing the MF to descend into an unplanned location and strike a 3/8 inch diameter galvanized steel cable strung horizontally between two 341 foot high towers. The AIB president also found by a preponderance of evidence that three factors substantially contributed to the mishap: (1) mission planning created a route of flight enabling navigation beyond the intended HLZ; (2) a breakdown in crew resource management within the MC and between the MF failed to sufficiently detect and effectively communicate the navigation error; and (3) low illumination conditions present rendered night vision goggles insufficient to detect the cables.

Chapter 3.1. ACCIDENT SUMMARY

On 15 March 2018, at approximately1840 Zulu time (Z), 2140 Local time (L), the mishap aircraft (MA), an HH-60G, T/N 92-6466, assigned to the 332d Air Expeditionary Wing (AEW), and operating within the USCENTCOM AOR, struck a galvanized steel cable and subsequently impacted an uninhabited desert area.

Four MA flight crewmembers and three members of the Guardian Angel (GA) team were fatally injured in the mishap. The MA was destroyed upon impact, there were no other injuries or fatalities, and there was no damage to private property.

Chapter 3.2. SEQUENCE OF EVENTS

a. Mission

The MA was the lead helicopter in a formation of two HH-60Gs during a combat pre-position mission departing from its base at night on 15 March 2018. The MA was followed by the mishap wingman (MW) aircraft for the duration of the flight. The MA and MW comprised the mishap formation (MF). The MA contained a seven member mishap crew (MC): the mishap pilot (MP); the mishap co-pilot (MCP); the right special mission aviator (SMA), known as the mishap flight engineer (MFE); the left SMA, known as the mishap aerial gunner (MAG); and three pararescue (PJ) team members, comprised of the mishap Combat Rescue Officer (MCRO), mishap PJ 1 (MPJ1) and mishap PJ 2 (MPJ2). The MW aircraft contained two pilots, two SMAs, and two PJs, collectively known as the mishap wingman crew (MWC).

The purpose of the mission was to pre-position the MF to a helicopter landing zone (HLZ) closer to the location of an upcoming operation in order to expedite the recovery of any potential personnel or assets in need of rescue. The mission involved a nighttime departure from the base, en route helicopter air-to-air refueling (HAAR) with an HC-130, and a descent to low-level (less than 500 feet above ground level (AGL)) prior to landing at the HLZ. Once at the HLZ, the MF would remain on ground alert during the upcoming operation, and then return to the base once the operation was completed.

b. Planning and Crew Mission Briefing

Planning for the mission started at approximately 0930Z on the morning of 15 March 2018 based upon notification from the Joint Personnel Recovery Center (JPRC). Due to crew rest considerations, preliminary planning was conducted by Blue flight members of the 46th Expeditionary Rescue Squadron (ERQS) prior to the MC and MWC starting their duty day. Once the MC and MWC started their normal duty day, they took over primary responsibility of the mission planning process.

HAAR was coordinated with the supporting HC-130 unit and continuous coordination with the JPRC was conducted throughout the planning process as updates became available.

The planned timeline for the MF was an 1800Z take-off, en route HAAR at 1817Z, and landing at the HLZ immediately thereafter. Upon departure from the base, the MF planned to climb above low -level in order to conduct HAAR, then descend to low-level for the ingress and final approach to the HLZ.

The navigation route that the mishap crew planned for the mission contained seven navigational waypoints. This route provided navigation to the HLZ for the pre-position and then continued beyond the HLZ to a location that the MF would use for holding airborne alert if needed. Only the first three waypoints (waypoints 1, 32, and 25) were planned to be used for the pre-position mission to the HLZ. The remaining waypoints (waypoint 33 and on) were to be flown at higher altitudes and used for holding airborne alert in the event the MF had to launch from the HLZ for a rescue mission(s) later that night.

The MP gave the flight brief in the rescue operations center (ROC) at 1630Z. All members of the MF were present as well as the crew of the supporting HC -130, 46 ERQS Director of Operations, and the ROC "Battle Captain". The flight brief was approximately 30 to 45 minutes and covered all required areas to include weather, sequence of events, route of flight, flight altitudes, hazards, threats, HAAR plan, approach and parking plan at the HLZ, alert posture, mission notification and launch procedures, operational risk management (ORM), contingencies, and an intelligence update. During the flight brief, JPRC called the ROC to give confirmation that the planned pre-position mission to the HLZ was officially approved for execution. ORM was assessed as low for this mission.

The mission planning and briefing complied with 46 ERQS requirements, alert standards, and Air Force requirements, to include AFI 11-2HH-60, Volume 3, Flying Operations, 5 January 2011.

c. Preflight

Planned time to be in seats at the aircraft was 15 minutes prior to departure. Just prior to stepping to the aircraft, JPRC directed the MF to bring additional aircrew flight equipment based on additional mission requirements. Because the requirement to bring the extra equipment affected the aircraft weight and balance and max gross weight margin, the SMAs and PJs were required to reconfigure the aircraft and gear.

A formal aircrew preflight of the MA was not required on the day of the mishap. In accordance with normal alert procedures, the MA was preflighted on 14 March 2018 and placed on alert.

d. Summary of Accident

Engine start, taxi, takeoff, departure, and HAAR of the MF were uneventful. The rendezvous with the HC-130 for HAAR occurred approximately 10 minutes late and northwest of the planned Air Refueling Control Point (ARCP). The MF refueled uneventfully and cleared the HC -130 to depart to the south. Until this time, the MP had been flying the MA. Following the completion of HAAR for the MA, the MP turned control of the MA over to the MCP. The MF was a couple of miles north of their planned HAAR track and approximately five minutes east of the destination HLZ.

Once clear of the HC-130, the MF began navigating directly to the next waypoint in their flight plan, waypoint 25, which was the intended HLZ. Over the next four and a half minutes, the MF proceeded to this waypoint while simultaneously starting a shallow descent from refueling altitude. During this same period, the MP was interrupted multiple times during his navigation duties including communications with the MW regarding landing zone plan changes and MC requests for pre-landing power calculations and JTAC information requests. The JTAC at the HLZ initiated contact with the MF and discussed with the MP that they were still expecting the MF to approach from south to north and that the JTAC was able to employ a signaling device to point out the HLZ's location if required. The JTAC also reiterated that there were some towers located in the immediate area surrounding the HLZ. By the end of this dialogue with the JTAC, the MF was slightly to the northeast of the HLZ, and subsequently made a right turn to the north towards waypoint 33, a waypoint intended only for a follow on mission.

During the turn north, the MF overflew the HLZ, and began a descent to low-level. As the MA descended through approximately 900 feet AGL, the MC began to identify and avoid a set of power lines and four towers. Two of the towers were to the left side (Tower Set A) and two were on the right side (Tower Set B) of the MA's flight path. Immediately after the MC called out these obstacles, the MCP decided to level off at 300 feet AGL.

Seconds before contact with the cable, the MCP turned the MA left to avoid the north tower of "Tower Set C" at the MA's one o'clock position while at the same time announcing the presence of towers to the MW. Following the left turn away from the north tower, the MA struck a cable located second from the top in a series of four cables strung horizontally between two 341 foot towers spaced an estimated 1,000 yards apart. Each of the four cables were spaced approximately 20 vertical feet apart. No member of the MC or MWC verbally announced seeing the other tower the cables were connected to or any of the four cables between the towers. At the time of impact with the cable, the MA was traveling an estimated 125 knots indicated airspeed at an altitude between 250 and 270 feet AGL. Immediately following cable impact, the MP and MCP swiftly and calmly switch control of the MA. The MCP also made the near simultaneous and directive call to land. Immediately after the "land" call, the aircraft suffered catastrophic structural failures and was completely uncontrollable prior to impact with the ground.

The main rotor blade(s) of the MA were the first components to make contact with the cable. Post-crash analysis determined the cable broke free from the tower to the left of the MA.

The cable which remained attached to the right tower was pulled in the direction of the MA's flight path. As the cable wrapped around the main rotor and associated components, it also struck the tail rotor driveshaft and tail rotor blade(s) leaving behind transfer marks. With the main rotor turning at 258 rotations per minute, the loops of cable recovered took about five seconds to wrap and tighten around the main rotor hub and slow the rotor system. With torque still being applied to the rotor system from the engines, the main rotor hub experienced severe misalignment and mass imbalance, thus bending the main rotor shaft causing catastrophic failure of the shaft and liberation of the main rotor hub. As main rotor blades were lost, the imbalance caused vibrations throughout the aircraft that are incapacitating to the occupants, eventually causing complete failure of the transmission mount structure, which is evident by the main transmission module being completely torn from the aircraft while in the air. Failure of the tail rotor pylon was secondary to the failure of the main rotor system. The liberating of parts, vibrations, and severe right yaw as the rotor slowed caused separation of the upper section of the tail pylon. Based on their damage and location in the debris field, it appears that the aircraft main rotor blades, main rotor head, main transmission gearbox, tail rotor system, and tail pylon separated prior to the fuselage impacting the ground. The length of the debris field containing the fuselage parts indicates a significant forward velocity at impact with the ground, prior to most of the fuselage being consumed in a post-crash fire. Based on the estimated impact acceleration forces, the crash was not survivable.

The HH-60G is equipped with a wire strike protection system (WSPS); however, post-crash analysis determined that it was not effective because it does not appear that the cable had the opportunity to be pulled through any of the WSPS wire cutters. Post-crash material transfer analysis indicates that the leading edge of a main rotor blade was the only component to come in contact with the upper WSPS assembly. It is unknown whether the WSPS would have been effective in cutting the heavy gauge cable, had it been pulled directly into the WSPS cutters.

e. Impact

The aircraft impacted the ground at approximately 1840Z. At the time it struck the cable, the MA was traveling an estimated 125 knots indicated airspeed, at an altitude between 250 and 270 feet AGL. The aircraft main rotor blades, main rotor head, main transmission gearbox, tail rotor system, and tail pylon separated prior to the fuselage impacting the ground.

f. Egress and Aircrew Flight Equipment (AFE)

No evaluation of occupant protection equipment was conducted as it had all been consumed in the resulting fire.

g. Search and Rescue (SAR)

The MW was in a position to observe the impact of the MA. Within approximately 10 to 20 minutes of the crash, the MW observed vehicles responding to the crash location. At the time of the MA's impact with the cable, the MW was just under a half-mile away and had the MA slightly lower at their ten o'clock position. Near simultaneously to when the MA contacted the cable the MW turned right to avoid a tower (South Tower of Set B) only a few hundred meters off the nose of their aircraft. While the MW was in a right turn away from that tower, light generated from the MA's crash illuminated another tower and associated cables in front of the MW (North Tower of Set B), enabling the MWC to see and climb to avoid the hazards. This is the first and only time leading up to the mishap any members of the MF were able to see the cables strung between the different sets of towers.

As the MW continued its right turn and began to climb, they quickly realized that the bright flash was caused by the MA crash. Once safely above the hazards in the area, the MWC began coordinating to have a Quick Reaction Force (QRF) dispatched to secure the site, then notified command of the incident. A third HH-60G and additional PJs were also scrambled to the crash site while they continued working to identify a safe approach path and landing zone near the crash site. Hindering the MW's ability to land near the crash site were the extensive amount of towers and cables in the vicinity (only now visible due to the illumination from the crash) and severity of the fire from the crash, which was also obstructing their vision through NVGs. The fire was also causing the ammunition that was onboard the MA to ignite, causing an additional hazard and risk to the MW. About 20 minutes before the MW was able to land, coalition ground forces arrived and ensured security of the crash site.

Approximately 40 minutes after the crash, the MW was able to land roughly 700 meters from the site and inserted their two PJs to begin recovery operations. With them, the PJs had more than 300 pounds of extrication equipment to include hydraulic jaws and generator, shovels, pry tools, medical rucks/backpacks, fire extinguishers from the MW aircraft, and two air packs for protection from smoke and debris inhalation. Due to gross weight and power restrictions of the HH-60G, PJs split up their equipment between the two aircraft in formation. As a result, the extrication equipment was located on the MW, but the aircraft fire suppression equipment was on the MA and therefore not available for recovery operations. As the two PJs from the MWC were making their way via foot to the crash site, the third HH-60G arrived and inserted their two PJs and one Combat Rescue Officer (CRO) to assist the rescue effort. The CRO and four PJs then met with the coalition forces on-scene commander and were briefed on the situation at the crash site.

h. Recovery of Remains

Once at the site, the CRO and PJs worked with coalition forces and performed a comprehensive search to locate and recover the bodies of all seven of the fallen MC. Throughout the recovery, the team utilized fire extinguishers from the two other helicopters and ground vehicles to continuously battle the ongoing fire at the crash site. Once the MC members were recovered, they were driven back to the HLZ in coalition QRF ground vehicles. From the HLZ, United States Army Medical Evacuation helicopters transported the MC back to the base from which they departed.

Below is a countdown timeline beginning at takeoff and ending shortly after the MA's impact with the cable.

Summary of Mishap Timeline

Time Until Cable Strike (Min:Sec), Summary of Mishap Timeline

40:00 Approximate MF Takeoff

12:22 Rendezvous with HC-130 for HAAR

06:40 HAAR complete

01:47 MF passes Northeast of HLZ and turns North

01:35 MF begins descent to low-level

00:30 MA descends through 900' AGL

00:24 MC visually acquires towers at 11 o'clock

00:10 MFE visually acquires towers at two o'clock

00:08 MA levels off at ~300' AGL

00:05 MCP turns left to avoid tower at one o'clock

00:03 MCP announces towers to MW

00:00 MA Strikes Cable

-00:05 Inflight Structural Failure of MA

Chapter 3.3. MAINTENANCE

a. Forms Documentation

Each individual Air Force aircraft has its own set of written and electronic maintenance records used to record all flight discrepancies, capture all maintenance performed, and inspection histories in the form of Air Force Technical Order (AFTO) Form 781s and the Integrated Maintenance Data System (IMDS) respectively. The AFTO Form 781 is a series of records documenting status of an aircraft to include aircraft condition and repairs.

The hard copy AFTO 781 forms found on the Mishap Aircraft (MA) at the time of the mishap were severely damaged. Two photos of AFTO 781A pages showing the last maintenance actions on the aircraft prior to flight were available via a non-standard photo taken by maintenance personnel. All remaining existing aircraft AFTO 781 series forms to include Time Compliance Technical order (TCTO) status, MA Jacket File, and 73 days of archived electronic IMDS were reviewed for accuracy and completeness. This review indicated that the aircraft was properly maintained and ready for the mission. At the time of the mishap, the MA total airframe time was 6,769.8 hours. The MA flew a total of 6.4 hours on the three previous missions. The review of archived electronic aircraft forms, also known as IMDS, revealed no maintenance discrepancies that would have prevented the MA from being airworthy or unable to perform the mission and no evidence suggests that maintenance or forms documentation was a factor in the mishap.

b. Inspections

All scheduled maintenance inspections were current and accurately documented prior to the mishap. The last scheduled inspection was a 50-hour inspection accomplished on 12 February 2018.

In addition to the last scheduled inspection, the MA received a preflight maintenance inspection. This type of inspection is accomplished prior to first flight of the flying period and is valid for a period of 72 hours. This preflight inspection was accomplished on 14 March 2018 at 1300Z and had approximately 42 hours of validity remaining at the time of the mishap. The maintenance documentation confirmed that all inspections and maintenance actions were accomplished and documented in accordance with applicable maintenance directives, and there is no evidence to suggest that an inspection was a factor in the mishap.

c. Maintenance Procedures

The most recent physical archived forms from the aircraft jacket file and current IMDS were reviewed, revealing insignificant documentation discrepancies; however none of the discrepancies were a factor in the mishap. The review of active and historical MA AFTO 781 series aircraft forms revealed no discrepancies in maintenance procedures, practices or actions that deviated from established directives on the MA. A comprehensive review of all available maintenance data from 1 January 2018 up to the day of the mishap indicate that maintenance was not a factor during this mishap.

d. Maintenance Personnel and Supervision

Individual military training records for all maintenance personnel who performed a preflight inspection on the MA were thoroughly reviewed. All maintenance members were fully qualified and performed proper maintenance actions.

e. Fuel, Hydraulic and Oil Analysis

Three fuel samples were provided for testing to the Air Force Petroleum Office (AFPET) Laboratory from different sources that provided fuel to the MA. All three samples showed no evidence of contamination or deficiency. There is no evidence to indicate fuel was a factor in this mishap. Hydraulic and Oil samples from the MA aircraft could not be recovered for processing and testing because they were consumed when the fuselage was destroyed by the post-crash fire. Cockpit oil pressure indications were within normal operating limits.

f. Unscheduled Maintenance

A review of all maintenance activities on the MA from 1 January 2018 to the day of the mishap revealed no discrepancies or recurring maintenance issues. There is no evidence to suggest that unscheduled maintenance was a factor in the mishap.

Chapter 3.4. AIRFRAME, MISSILE, OR SPACE VEHICLE SYSTEMS

a. Structures and Systems

At the time of the incident, all relevant MA systems were operating properly. Damage and Crash Analysis was provided by the Air Force Safety Center, and material and failure analysis was provided by the Materials Integrity Branch, Wright-Patterson Air Force Base.

(1) Airframe

The main fuselage with the lower portion of tail pylon and stabilator were still attached. Most of the fuselage was destroyed in a post-crash fire. The length of the debris field containing fuselage parts indicates significant forward velocity at impact. The MA main rotor blades, main rotor head, main transmission gearbox, tail rotor system and tail pylon all appear to have separated in flight, based on their damage and location in the debris field, prior to the fuselage impacting the ground.

(2) Rotor System

A main rotor blade recovered showed scraping along the leading edge and an impact mark on the upper airfoil surface that is similar to the surface of the tower cable. The impact mark begins 2–3 feet inboard of the rotor blade tip, indicating that the aircraft struck the cable with a main rotor blade first. Damage to the tip of the blade is from impact with the ground from the rear direction, indicating it was not turning at the time of impact. The root end is broken free close to the hub. Scrape marks from the ground are present in the span wise direction, indicating it slid along the ground after impact.

The main rotor head and rotating swash plate are completely broken free from the transmission drive shaft, with a short portion of the shaft still contained in the main rotor head. The drive shaft failure appears to be from torsional overload, with smearing from interaction between the shaft and hub. Three of the four pitch control rods are broken with some portions missing. Three of the main rotor blade roots are present, with the blade spars broken and or separated just outboard of the root. One blade root is missing, broken where the blade shaft attaches at the elastomeric bearing. The significant damage to the rotor head and drive shaft indicates it suffered catastrophic damage under power.

(3) Wire Strike Protection System (WSPS)

The WSPS is a simple, light-weight system without motorized or pyrotechnic components which is used to cut, break or deflect wires that may strike the helicopter in the frontal area between the tires and the fuselage and between the fuselage and the main rotor in level flight. Protection is provided against horizontal strung wire at 60-90 degrees to the flight path by cutting or deflecting the wire without exceeding the structural criteria, by cutting or deflecting, as applicable, a wire up to 3/8 inch diameter, 1x7 strand steel cable having an ultimate strength of up to 11,000 pounds. The WSPS was not effective because it does not appear that the wire was pulled into any of the WSPS cutters or deflectors.

The upper WSPS showed no contact damage along the length of the cutter with the cable. Paint was intact and undisturbed after it was wiped clean. Areas of missing paint and contact damage were observed on the support structure for the upper WSPS. Both support arms were bent and the connection bolt fractured; however, titanium transferred onto the upper WSPS support arm, which suggests the leading edge of a blade was the source of the support arm scrape and not a cable.

A piece of the lower WSPS cutter that is fuselage mounted by the aircraft landing gear was bent with paint missing on the convex tension side. Contact damage was observed in an area where the cutter blade attached. A fractured surface also observed at the curved end of the piece. The fractured surface exhibited material rubbed along with fine, elongated dimples indicative of shear ductile overload. Since only a portion of the lower WSPS assembly was recovered without any of the cutter, it is unknown if this assembly caught the cable, which led to the observed failure. However, the directionality of the dimples on the lower WSPS piece does not support this scenario.

b. Evaluation and Analysis

(1) Cable Segment

The cable wires were galvanized steel of a right hand lay, seven wire strand design. Measurements using a machinist's microscope indicated the cable diameter to be between 0.35 and 0.36 inches and the average individual wire diameter was 0.115. The cable tensile strength was tested and the max load achieved was 14,929 lbs. before wire failure occurred.

(2) Integrated Vehicle Health Monitoring Systems (IVHMS) Data

IVHMS provides monitoring and diagnostic capabilities that include exceedance monitoring, engine and drive train health monitoring. The IVHMS analysis indicated the engines, drive train, flight controls, and associated parametric data were all within expected operating ranges. Data examined from both engines indicated normal operations and expected power was available. Aircraft flight data indicated that the MA was responding normally to flight control inputs. All monitored MA systems functioned properly until after contact with the cable.

Chapter 3.5. WEATHER

a. Forecast Weather

The forecasted weather at the departure base was a broken ceiling at 15,000 feet mean sea level (MSL) and 20,000 feet MSL, visibility greater than 9,000 meters, and winds from 320 degrees at 6 knots. The forecast surface temperature was 18 degrees Celsius, with light rime icing from 10,000 feet MSL to 20,000 feet MSL. The forecasted altimeter setting was 29.90 inches of mercury, and pressure altitude was 585 feet MSL with a density altitude of 1,065 feet MSL. Lunar illumination was forecast to be seven percent with moonrise at 0212Z and moon set at 1320Z. The forecasted weather for the HLZ was the same.

b. Observed Weather

The mishap sortie began at 1800Z, well after the moon had set, resulting in very low lunar illumination for the entirety of the flight. Conditions during the flight and subsequent search and rescue were reported as clear skies, low illumination, no moon, with dust and haze reducing visibility to three or four miles.

c. Space Environment

Not applicable.

d. Operations

Flight operations were conducted within the prescribed operational weather limitations for the aircraft systems and in accordance with regulatory guidance.

Chapter 3.6. HUMAN FACTORS ANALYSIS

The Department of Defense Human Factors Analysis and Classification System version 7.0 (DoD HFACS 7.0) lists potential human factors that can play a role in aircraft mishaps. Human factors describe how a person's interaction with tools, tasks, working environments, and other people influence human performance. All human factors as prescribed in the Department of Defense Human Factors Analysis and Classification System 7.0 were considered (DoD HFACS 7.0).

Four human factors were identified as being relevant to the mishap: (1) Misinterpreted/Misread Instrument; (2) Interference/Interruption; (3) Inaccurate Expectation; (4) Environmental Conditions Affecting Vision.

a. PC505 Misinterpreted/Misread Instrument

Misinterpreted/Misread Instrument is a factor when the individual is presented with a correct instrument reading but its significance is not recognized, it is misread or is misinterpreted.

The MF pilots developed and were familiar with the flight plan route. There were no reported navigation system or equipment problems. After completing HAAR, the MP navigated the MF toward the HLZ and then erroneously navigated to a waypoint beyond their intended destination. Although the MCP made a correct estimated arrival time to the HLZ, the MP misinterpreted the time to be arrival at a waypoint prior to the intended HLZ. No route corrections were made by anyone in the MF. The MWC had accurate navigation data and also failed to recognize instrument indicators directing the MF to the HLZ.

b. PC108 Interference/Interruption

Interference/Interruption is a factor when an individual is performing a highly automated/learned task and is distracted by another cue/event that results in the interruption and subsequent failure to complete the original task or results in skipping steps in the original task.

The MP had multiple duties in addition to navigation of the MF. In the time after completing HAAR and leading up to time of mishap, the MP received multiple interrupting requests for information. The MP coordinated with the MW regarding landing zone plan changes, MC requests for pre-landing power calculations and JTAC information requests. These non-navigation related tasks consumed the vast majority of the MP and MF's time following HAAR, and reduced their time available to identify their navigation error.

Crew Resource Management (CRM) is the effective use of all available resources--people, weapon systems, facilities, and equipment, and environment -- by individuals or crews to safely and efficiently accomplish an assigned mission or task. The MF lacked effective CRM in the performance of their duties to aviate, navigate and communicate, which resulted in their failure to verify navigation information being provided by MP.

c. PC110 Inaccurate Expectation

Inaccurate expectation is a factor when the individual expects to perceive a certain reality and those expectations are strong enough to create a false perception of the expectation.

The MF had the perceived reality that the MF was south of the intended destination. Based on their route study, the MF also expected a south to north approach to the HLZ. Therefore, even the turn to the north, while in error, supported the MF's perception of an approach to the HLZ. And when the MF's navigation equipment indicated an overflight of the HLZ, the perception of the MF was strong enough to create the perception that the MF was on track to the HLZ. The MF understood the approach to the HLZ would be safe and did not expect hazards on their planned approach .

d. PE101 Environmental Conditions Affecting Vision

Environmental Conditions Affecting Vision is a factor that includes obscured windows; weather, fog, haze, darkness, smoke, etc.; brownout/whiteout (dust, snow, water, ash or other particulates); or when exposure to windblast affects the individual's ability to perform required duties.

Night navigation involves inherent challenges such as darkness affecting visual acuity and includes hazards due to vision illusions. The aircrew members of the MC had battery-powered AN/AVS-9G night vision goggles (NVGs) mounted to their helmets as their primary means of maintaining night vision. NVGs enable aircrew to operate in a night environment, but when compared to the human eye under daylight conditions, vision under NVGs is limited. This results in a decreased level of situational awareness, amplified by certain human factors and environmental limitations. NVGs have a more reduced field of view compared to the human eye, particularly in peripheral vision, requiring an active and aggressive scan on the part of the NVG user in order to compensate appropriately during flight. Current NVGs have a resolution capability of 20/25 to 20/40 Snellen visual acuity, less than "normal day vision," which is 20/20. Of note, this visual acuity of 20/25 to 20/40 is the best that aircrew can expect to attain under optimal conditions. When flying with NVGs "detection ranges decrease and recognition of objects, terrain and targets can be severely limited". Current HH-60G Tactics, Techniques, and Procedures contains a warning stating, "electric power lines, unlit towers, poles, antennas, dead trees, and all types of wires are extremely difficult to see while conducting NVG operations".

Factors such as low or zero lunar illumination present on the night of the mishap degraded visual acuity and significantly limited the MF's ability to see obstacles until at close range. This also negatively impacted the MF's ability to use visual geographic references to improve their situational awareness of their actual location.

Chapter 3.7. STATEMENT OF OPINION

1. OPINION SUMMARY

On 15 March 2018, at approximately 1840 Zulu time, 2140 Local time, the mishap aircraft (MA), an HH-60G, tail number (T/N) 92-6466, assigned to the 332d Air Expeditionary Wing and operating in the USCENTCOM AOR crashed in an uninhabited desert area fatally wounding all seven Airmen on board.

I find by a preponderance of evidence that the cause of the mishap was the result of the mishap pilot misinterpreting aircraft navigation displays, causing the mishap formation (MF) to descend into an unplanned location and strike a 3/8 inch diameter galvanized steel cable strung horizontally between two 341 foot high towers. In addition, I found by a preponderance of evidence that three factors substantially contributed to the mishap: (1) mission planning created a route of flight that enabled navigation beyond the intended helicopter landing zone (HLZ); (2) a breakdown in crew resource management (CRM) within the mishap crew (MC) and between the mishap formation (MF) failed to sufficiently detect and effectively communicate the navigation error; and (3) low illumination conditions present during the mission rendered night vision goggles (NVGs) insufficient to detect the cables.

I developed my opinion by analyzing factual data from historical records, Air Force directives and guidance, engineering analysis, witness testimony, flight recorded data, animated simulations and information provided by technical experts.

2. CAUSE

I find by a preponderance of evidence that the cause of the mishap was the mishap pilot misinterpreting aircraft navigation displays resulting in the MF descending into an unplanned location and striking a 3/8 inch diameter galvanized steel cable strung horizontally between two 341 foot high towers. There were no reported navigation system or equipment problems. The MC was familiar with the planned route and intended to land at the HLZ. Following helicopter air-to-air refueling (HAAR), the MP initially directed the MF to the intended HLZ, but the MP subsequently directed a turn to the north, away from the HLZ. This route of flight indicates either a selection by the MP of the next navigation waypoint as the MF's destination and/or a misinterpretation of the HLZ as a turn-point prior to the HLZ. The Mishap Co-Pilot (MCP) took evasive action to avoid striking a tower at the MA's one o'clock position by turning left. This left turn resulted in the MA striking the second from the top of four galvanized steel cables. It is determined that the MC never visually acquired the cables or the other tower connecting the cables. The cable quickly entangled in the main rotor assembly resulting in catastrophic damage and an unflyable aircraft condition.

3. SUBSTANTIALLY CONTRIBUTING FACTORS

a. Mission planning created a route of flight that continued beyond the intended HLZ.

I find by a preponderance of evidence that mission planning created a route of flight with additional waypoints beyond the intended HLZ, which substantially contributed to the mishap. This additional route symbology and numerology displayed on the navigation display enabled a waypoint beyond the HLZ to be selected in error or an interpretation of the HLZ as a turnpoint prior to the HLZ. Had the route terminated at the intended HLZ, it is unlikely the MF would have flown past the HLZ.

b. A breakdown in CRM within the MC and between the MF failed to sufficiently detect and effectively communicate the navigation error.

I find by a preponderance of evidence CRM was not effectively used or accepted, which substantially contributed to the mishap. During MC communications regarding landing time, the MCP correctly identified distance and time to the HLZ, but was erroneously corrected by the MP as the distance and time relative to the waypoint. Further, the Mishap Wingman (MW) failed to adequately provide the proper navigation support of overflying the intended HLZ. This lack of CRM by the MF failed to identify the error, first by failing to correct the MA's erroneous communication and second, during overflight of the intended HLZ, the MF proceeded north despite the indication that navigation instruments properly depicted the overflight.

c. Low illumination conditions present on the evening of the mishap rendered the NVGs insufficient to detect the cables.

I find by a preponderance of evidence that low illumination conditions rendered night vision goggles insufficient to detect the cables which substantially contributed to the mishap. No member of the MF visually identified the cables while using NVGs as the primary equipment to see and avoid unexpected hazards, prior to the MA making contact with them. Low illumination and subsequent NVG visual acuity limitations severely restricted the MC's ability to identify and recognize the field of towers and cables they flew into. Further, the MA was not equipped with any sensors enabling them to identify cables strung between towers. The result was delayed obstacle detection on a very low illumination night as experienced by the MF. This accounted for the late visual acquisition of towers and not being able to detect the cables by the MF.

5. CONCLUSION

I find by a preponderance of evidence that the cause of the mishap was the MP misinterpreting aircraft navigation displays resulting in the MF descending into an unplanned location and striking a 3/8 inch diameter galvanized steel cable strung horizontally between two 341 foot high towers. In addition, I found by a preponderance of evidence that three factors substantially contributed to the mishap: (1) mission planning created a route of flight which enabled navigation beyond the intended HLZ; (2) a breakdown in CRM within the MC and between the MF failed to sufficiently detect and effectively communicate the navigation error; and (3) the low illumination conditions present during the mission rendered NVGs insufficient to detect the cables.

Chapter 4. F-16CM Creech 2018.04.04

F-16CM, T/N 91-0413

Nellis Air Force Base, Nevada

LOCATION: Nevada Test and Training Range

DATE OF ACCIDENT: 4 April 2018

On 4 April 2018, the mishap pilot (MP), flying a F-16CM, tail number (T/N) 91-0413, assigned to the United States Air Force Air Demonstration Squadron, the "Thunderbirds," 57th Wing, Nellis Air Force Base (AFB), Nevada (NV), engaged in a routine aerial demonstration training flight at the Nevada Test and Training Range (NTTR) near Creech AFB, NV. During the training flight, at approximately 1029 local time, the mishap aircraft (MA) impacted the ground and fatally injured the MP, without an ejection attempt.

The mishap mission was planned and authorized as a practice of a Thunderbirds aerial demonstration in the south part of the NTTR. The mishap flight was a formation of six F-16CMs (Thunderbirds #1-6), the standard Thunderbirds aerial demonstration flight. Thunderbird #4 was the MA/MP. During the High Bomb Burst Rejoin, an aerial maneuver near the scheduled end of the aerial demonstration training flight, the MP flew the MA for approximately 22 seconds in inverted flight between 5,500 and 5,700 feet above ground level. During this time, the MP experienced a change in force due to acceleration measured in multiples of the acceleration of gravity felt at the earth's surface (G), between -0.5 to -2.06 G's. While experiencing -2.06 G's in inverted flight, the MP initiated a descending half-loop maneuver (Split-S). After five seconds in the Split-S, the MP attained a maximum +8.56 G's. The MP experienced G-induced loss of consciousness (G-LOC) and absolute incapacitation at the end of that five-second period.

For approximately the next five seconds, the MP remained in a state of absolute incapacitation and made no deliberate flight control inputs as the MA accelerated toward the ground. Approximately one second prior to ground impact, the MP began deliberate flight control inputs as he transitioned from absolute to relative incapacitation. The MA impacted the ground at 57 degrees nose low with 89 degrees of left bank and the MP was fatally injured on impact, without an ejection attempt.

The Accident Investigation Board (AIB) President found by a preponderance of evidence the cause of the mishap was the MP's G-LOC during the Split-S portion of the High Bomb Burst Rejoin maneuver. Additionally, the AIB President found by a preponderance of evidence two factors substantially contributed to the mishap: (a) the MP's diminished tolerance to +G's induced by the physiology of the MP's exposure to –G's ("Push-Pull Effect") and (b) an associated decrease in the effectiveness of the MP's Anti-G straining maneuver under those conditions.

Chapter 4.1. ACCIDENT SUMMARY

On 4 April 2018, the mishap pilot (MP), flying a F-16CM, tail number (T/N) 91-0413, assigned to the United States Air Force Air Demonstration Squadron (USAFADS), "the Thunderbirds," 57th Wing, Nellis AFB, NV, engaged in a routine aerial demonstration training flight at the NTTR near Creech AFB, NV. During the training flight, at approximately 1029 local time (L), the mishap aircraft (MA) impacted the ground and fatally injured the MP, without an ejection attempt.

There were no other injuries or fatalities, and there was no damage to private property.

Chapter 4.2. SEQUENCE OF EVENTS

a. Mission

The mishap flight (MF) was a formation of six F-16CMs, the standard Thunderbirds aerial demonstration flight. The Thunderbirds "Diamond Formation" consisted of Thunderbird #1 (TB1), Thunderbird #2 (TB2), Thunderbird #3 (TB3) and Thunderbird #4 (TB4) as depicted in. TB4, also known as the "Slot" pilot or position, was the MP/MA. The solos, the aircraft flying independently of the Diamond Formation in the aerial demonstration, consisted of Thunderbird #5 (TB5) and Thunderbird #6 (TB6) and comprised the rest of the MF.

The planned mission was to conduct a Thunderbirds practice aerial demonstration. Planned mission tasks included practice aerial demonstration maneuvers on takeoff from Nellis AFB, a departure to a south area of the NTTR, and a practice of the "High Show" version of the Thunderbirds aerial demonstration. In the High Show, the Thunderbirds perform a series of aerial demonstration maneuvers requiring cloud ceilings higher than 8,000 feet above the ground level (AGL) and visibility greater than five miles. The planned mission culmination was a return to Nellis AFB for landing. The Thunderbirds operations officer authorized the mission on an Aviation Resource Management System (ARMS) Fighter Flight Authorization Form.

b. Planning

TB1 conducted the preflight brief at approximately 0800L. The brief was conducted IAW USAFADS standards and AFI 11-2F-16V3, F-16 Operations Procedures (13 Jul 2016). The brief covered mission objectives, operational risk management (ORM), current and forecasted weather, notices to airmen (NOTAMS), emergency procedures (EPs), special interest items (SIIs), and the lineup card mission materials. TB6 was in charge of collecting the ORM data for the mission and collecting any personal safety factors for the flight. The overall ORM for the mission was briefed as "Green". The MP gathered and briefed the weather, NOTAMS, and made the lineup card for the MF during the MF brief. This included writing the applicable timing data such as takeoff and landing and the airspace times. The weather and NOTAMS supported the planned mission for that day. The brief was conducted in a timely manner, IAW squadron standards, with approximately 20 minutes until the MF pilots were to go out ("step") to the flight line and their aircraft.

c. Preflight

The MP "stepped" to the MA with the other pilots of the MF, at approximately 0905L, where the MP donned his CSU-22/P Advanced Technology Anti-G Suit (ATAGS). The ATAGS is a pant-like garment consisting of bladders that fill with air from the aircraft to put pressure on the abdomen, thighs, and calves during an increase in +G's to increase a pilot's tolerance to +G's and help prevent G-induced loss of consciousness (G-LOC). Once the MP was in the cockpit, the Dedicated Crew Chief (DCC) assisted the MP with connecting his ejection seat harness and ATAGS to the aircraft. The MP appeared in good spirits, and correctly zipped his ATAGS. TB1 then directed the MF to complete preflight checks prior to taking off. During these checks, the pilots tested their ATAGS system via a button in the cockpit.

d. Summary of Accident

The MF departed Nellis AFB at approximately 0950L. The Diamond Formation coordinated with Nellis Tower for a Diamond Loop on takeoff while TB5 and TB6 took off as single ship aircraft. The Diamond Loop is an aerial demonstration maneuver where the Diamond Formation performs a loop immediately after takeoff and was executed IAW the 57 WG Supplement to Air Combat Command Instruction (ACCI) 11-USAFADS Volume 3, Operational Procedures-Thunderbirds, 3 January 2018. The MF then proceeded toward the northwest and entered the NTTR (approximately 12 miles north of Creech AFB) at approximately 0956L.

The Range Safety Officer (RSO), equipped with a UHF/VHF radio, primarily served as a safety monitor and supervised the recording of the practice with video equipment for debriefing purposes. Three enlisted personnel from the Thunderbirds accompanied the RSO to the NTTR to film the practice, record the timing, and provide communications expertise. These personnel were located in a tower on the practice range to observe the practice demonstration. Upon reaching the area, the RSO radioed the MF the weather and the status of Creech AFB runways. The RSO reported the winds calm, with few clouds at 16,000 feet AGL and scattered clouds at 19,000 feet AGL, with an altimeter setting of 30.06 inches of mercury. The MF then setup to practice the High Show version of the Thunderbirds aerial demonstration.

The practice area in the NTTR provides a similar appearance to an airfield typically used in aerial demonstrations, with a visible marker on the ground for show center (SC). The first aerial demonstration maneuver the MF executed on the NTTR was the Diamond Cloverloop Opener to begin the High Show practice. During this maneuver, the Diamond Formation accomplished their G-Exercise (G-Ex) to assess ATAGS operation and personal tolerance for +G's. Because of the nature of the public demonstration, the Thunderbirds are not required to execute a stand-alone G-Ex, as authorized by an ACC waiver permitting deviation from AFI 11-2F-16V3. This deviation permitted pilots to conserve fuel for the demonstration and maintain flight safety. The Data Acquisition System (DAS) also recorded three separate instances where the MP was previously greater than +4 G's on the date of the mishap, with one instance as high as +7.9 G's. Based on witness testimony and Heads Up Display (HUD) audio recordings, the MP did not announce problems with his ATAGS inflation or personal tolerance for +G's prior to the mishap.

The practice aerial demonstration was uneventful, with only minor deviations up until and including the High Bomb Burst Cross near the planned end of the sortie. After the High Bomb Burst Cross at 1028:18L, the Diamond Formation maneuvered to join back together in the High Bomb Burst Rejoin. The objective of the High Bomb Burst Rejoin, an aerial demonstration maneuver performed by the Thunderbirds in the F-16 for the past 35 years, was to have the entire Diamond Formation together by SC. Just after the High Bomb Burst Cross, the MP was traveling on a heading of 175 degress, 414 knots calibrated airspeed (KCAS, the airspeed measurement available to the pilot in the cockpit) and 3,284 feet mean sea level (MSL, the altitude measured above sea level available to the pilot in the cockpit). This MSL equates to approximately 300 feet AGL, based on the varying terrain elevation.

After the diamond formation passed each other IAW, TB1 made the prescribed radio call to initiate the High Bomb Burst Rejoin at 1028:24L. The MP then executed an ascending half-loop, also known as an Immelmann, by selecting engine power at maximum afterburner and pulling back on the control stick, achieving +7.9 G's in the pull. The MP arrived at the top of the Immelmann at 1028:38L, inverted, heading north, 312 KCAS, and 8,616 feet MSL.

At 1028:44, TB1 made the prescribed radio call to signal that he was beginning his 5/8 of a loop before rolling to wings level (Half Cuban Eight) to point south towards SC. At this point TB2 and TB3 made the prescribed radio calls indicating they were visual with TB1 before they initated their rejoins. IAW the 57 WG Supplement to ACCI 11-USAFADS Volume 3, the MP followed with his prescribed radio call to announce he was visual with TB1 and provide his altitude and airspeed parameters: "4's Gotcha, 4's on top 85 [8,500 feet MSL], 400 [400 KCAS]". This altitude and airspeed met the minimum requirements for the MP to safely perform the descending half loop (Split-S) to rejoin with TB1.

At 1028:56L, TB1 made the prescribed radio call as he reached his maximum altitude during his Half Cuban Eight. Two seconds later at 1028:58L, the MP selected idle engine power and pushed forward on the control stick to attain -2.06 G's, with a resulting 2,250 feet per minute climb at five degrees nose high. One second later, the MP began his Split-S maneuver by pulling the nose of the MA down towards TB1. The MP continued this manuever and achieved a maximum of +8.56 G's at 1029:03L.

Based on the DAS data, the MP stopped providing deliberate flight control inputs at 1029:04L. This left the aircraft 68 degrees nose low, 30 degrees left bank, accelerating through 356 KCAS, and rapidly descending through 6,556 feet MSL, with a 38,500 feet per minute descent rate. This descent continued until 1029:08L, when the MP began to increase engine power and pulled back on the control stick at 1029:09L. At that point, the MA was at 415 KCAS, 3,452 feet MSL (406 feet AGL), 60 degrees nose low, and 65 degrees left bank. Based on F-16 dive recovery procedures, once the aircraft descended below 2,300 feet AGL at that dive angle, a safe recovery above the ground was not possible.

e. Impact

At 1029:10L, the MA impacted the ground at 419 KCAS, 57 degrees nose low, 89 degrees left bank, and a descent rate of 39,750 feet per minute with maximum control stick input and high engine power setting. The RSO made the radio call "4, recover " just as the MA impacted the ground. Both the RSO and TB6 called "Knock it off " on the radio to cease demonstration maneuvers. The MA impact resulted in the MP's fatal injuries.

The MA carried no weapons, external fuel tanks, or stores. The terrain of the practice area is flat with low shrubs and some rising terrain surrounding the practice "runway". The MA debris field was south-southeast of the impact site.

f. Egress and Aircrew Flight Equipment (AFE)

Based on recorded audio and analysis of the canopy on impact, the MP did not attempt ejection. The impact destroyed the ejection seat and only fragments were recovered so no inspection was possible. There were no overdue inspections for any of the MP's flight equipment. The MP was current and qualified in the Aircrew Flight Equipment (AFE) continuation training, to include 120-day fit check, Egress, and Hanging Harness. All AFE personnel were qualified on the equipment. After completion of the Diamond Loop on Takeoff, the MP completed a Foreign Object Damage (FOD) check to ensure he was properly strapped in and to ensure no debris impeded aircraft operations during inverted flight. The MP did not mention any issues over the radio when he performed his FOD check.

g. Search and Rescue (SAR)

At 1029L, the RSO and TB6 made the "Knock-It-Off" call to stop the maneuvering for the practice aerial demonstration. TB5 immediately climbed to a safe altitude over the impact site to search for a parachute. At that time, the RSO called Creech Tower to inform them of the mishap and to send emergency services. Approximately one minute after the impact, TB1 cleared TB5 and TB6 to return to Nellis AFB, due to being low on fuel. Shortly after that, TB1 cleared TB2 and TB3 to return to Nellis AFB while TB1 continued to orbit over the impact site and assumed duties as the on-scene commander.

At 1033L, Nellis-Creech Fire Dispatch Center received notification via primary crash phone of an aircraft accident. Fire Department crews immediately dispatched to the flight line and Thunderbirds practice area. After determining that no aircraft were landing at Creech AFB, the crash recovery team traveled to the range and arrived at the crash scene at 1108L. The team included the Fire Chief, four different fire trucks, an ambulance, a rescue vehicle and associated personnel. The initial response time to the impact site was 35 minutes, with travel over approximately 14 miles on improved and unimproved surfaces. After arrival at the crash site, the Fire Chief notified his crew to don personal protective equipment, including self-contained breathing apparatus, and search the impact site for an ejection seat, parachute and/or signs of life. After ensuring the site was safe for follow on recovery actions and determining the MP had not survived the mishap, the crash recovery team suspended activities due to darkness at 1956L and left the mishap site under guard by Security Force. The crash recovery team did not report any difficulties as a result of weather, time of day, topography, or civilians at the crash site.

h. Recovery of Remains

A team of experts from Nellis-Creech Fire Emergency Services recommenced recovery efforts at 0845L on 5 April 2018. At 1430L, recovery teams departed the mishap site with the MP's remains and arrived at the Nellis AFB Medical Center by 1630L.

Chapter 4.3. MAINTENANCE

a. Forms Documentation

The Air Force Technical Order (AFTO) 781 series of forms collectively document maintenance actions, inspections, servicing, configurations, status, and flight activities. The AFTO 781 forms in conjunction with the Integrated Maintenance Data System (IMDS) provide a comprehensive database used to track and record maintenance actions and flight activity, and to schedule future maintenance.

A comprehensive review of the active AFTO 781 forms and IMDS revealed no discrepancies, overdue inspections, or overdue Time Compliance Technical Orders (TCTOs) that would ground the MA from flight operations. A thorough review of the active AFTO 781 forms and IMDS historical records for the 40 days preceding the mishap revealed no recurring maintenance problems. Additionally, the MA was operating as designed, and there was no indication of mechanical, structural, or electrical failure that would have contributed to the mishap.

b. Inspections

The Pre-Flight (PR) Inspection and Basic Post-Flight (BPO) Inspection include visually examining the aerospace vehicle and operationally checking certain systems and components "to ensure no serious defects or malfunctions" exist. Phase inspections are a thorough inspection of the entire aerospace vehicle. Walk-Around Inspections (WAI) are an abbreviated PR Inspection and are completed as required prior to launch IAW the applicable Technical Orders (TOs).

The total airframe operating time of the MA at takeoff of the mishap sortie (MS) was 6661.0 hours. Since its last phase inspection on 26 June 2017, the MA flew 262.4 hours. The last PR/BPO inspection occurred on 3 April 2018 at 1530L with no discrepancies noted. A WAI occurred on 4 April 2018 at 0730L with no discrepancies noted. Prior to the mishap, the MA had no relevant reportable maintenance issues and all inspections were satisfactorily completed.

c. Maintenance Procedures

A review of the MA's active and historical AFTO 781 series forms and IMDS revealed all maintenance actions complied with standard approved maintenance procedures and TOs.

d. Maintenance Personnel and Supervision

The USAFADS Maintenance Team performed all required inspections, documentations, and servicing for the MA prior to flight. A detailed review of maintenance activities and documentation revealed no errors. Personnel involved with the MA's preparation for flight had proper and adequate training, experience, expertise, and supervision to perform their assigned tasks.

e. Fuel, Hydraulic, Oil, and Oxygen Inspection Analyses

Due to the nature of impact, all fluid samples were destroyed and not testable. DAS data obtained from the MA indicated that the fuel system, hydraulic system and engine were all operating and responding to the MP's inputs at the time of impact. The samples from the oil and hydraulic fluid recovered from the servicing carts were not analyzed, based on information from a technical report and DAS data indicating that all systems were operating normally.

f. Unscheduled Maintenance

Unscheduled maintenance is any maintenance action taken that is not the result of a scheduled inspection and normally is the result of a pilot-reported discrepancy (PRD) during flight operations or a condition discovered by ground personnel during ground operations. There were no unscheduled maintenance actions since the last scheduled inspection.

Chapter 4.4. AIRFRAME, MISSILE, OR SPACE VEHICLE SYSTEMS

a. Structures and Systems

The MA impacted the ground at 57 degrees nose low and 89 degrees left bank into a dry desert with sparse vegetation. The majority of the MA was broken into pieces ranging in size from a few inches to a few feet. The largest debris recovered was part of the right wing. The impact crater measured 33 feet wide, 19 feet long and 3 feet deep. The debris field was mainly southeast of the impact crater, measuring 1,750 feet by 2,250 feet.

b. Evaluation and Analysis

(1) MA Data Acquisition System (DAS)

The DAS includes the Enhanced Crash Survivable Memory Unit (ECSMU), which contains non-volatile memory. The ECSMU contains 320MB of flash memory protected by an armored housing assembly for crash protection. The ECSMU contains flight data such as analog inputs, discrete inputs, and message/warning data. The DAS operated as expected until impact of the MA.

(2) MA Flight Control Surfaces

All the primary and secondary flight controls liberated from the MA at impact. Both wings and one horizontal tail were partially intact. One rotary actuator that controls leading edge flap movement was still connected to the wing structure. The DAS data and the position of the leading edge flap rotary actuator confirm the flight controls were responding appropriately to the MP's inputs at the time of the mishap.

(3) MA Engine

The engine was completely broken up on impact.

(4) Hydraulic System

The hydraulic system supplies hydraulic pressure at 3,000 pounds per square inch (psi), +/ - 50 psi. There are two systems, Systems A and B, that generate pressure from two engine driven hydraulic pumps. The two systems operate simultaneously and independently to supply pressure to the primary and secondary flight controls should one system fail. Both flight control accumulators were recovered from the mishap site. Upon disassembly, there were witness marks left by the pistons in both accumulators, indicating there was hydraulic fluid and pressure on the piston. The witness marks indicate the position the piston was in at the time of impact. Based on the DAS data and the physical evidence of the accumulators, both hydraulic systems were pressurized and providing hydraulic power at the time of impact.

(5) Electrical System

After a thorough search, neither the generator nor any electrical bus components were located in order to perform a physical analysis. The DAS data showed that the electrical system was supplying power to the aircraft systems and functioning at the time of impact.

(6) Escape System

The MA is equipped with an ejection seat actuated by the pilot pulling the ejection handle located on the forward part of the seat. Once this occurs, the canopy liberates from the aircraft and the ejection seat leaves the aircraft milliseconds later. The largest piece of the canopy was recovered several hundred feet away from the impact site, in line with the debris field. It had an accordion crush pattern indicating the canopy was secure to the MA at impact. The ejection seat was destroyed and only fragments were discovered. The DAS data did not record a "canopy open" in-flight warning. The MP did not initiate ejection within the period of recorded data.

Chapter 4.5. WEATHER

a. Forecast Weather

On 4 April 2018, forecast for NTTR South had winds out of the south at nine knots and a broken ceiling at 20,000 feet AGL, with good visibility. The forecast weather did not include precipitation.

b. Observed Weather

The RSO provided an updated weather status once the MF flew into the range airspace. The RSO reported calm winds, greater than 10 miles of visibility, a few clouds at 14,000 feet AGL, a broken ceiling at 19,000 feet AGL, and an altimeter setting of 30.07 inches of mercury, which was substantially similar to the actual recorded weather at Creech AFB. The RSO did not observe or report any precipitation.

c. Space Environment

Not Applicable.

d. Operations

The MF was operating within prescribed weather requirements for the High Show and pilot weather minimums.

Chapter 4.6. HUMAN FACTORS ANALYSIS

Loss of Consciousness (Sudden or prolonged onset)

The AIB considered all human factors as prescribed in the Department of Defense Human Factors Analysis and Classification System 7.0 (DoD HFACS 7.0) and found this mishap involved a Loss of Consciousness (Sudden or prolonged onset). This human factor falls under the "physical and mental state"/physical problem (PC300) area of DoD HFACS 7.0, and refers to the mental and physical states of individuals that can result in unsafe situations. Specifically, PC304, Loss of Consciousness, is a factor when the individual has a loss of functional capacity or consciousness due to G-induced loss of consciousness (G-LOC), seizure, trauma, or any other cause.

a. Effects of Acceleration on the Human Body

The acceleration due to gravity on earth is a constant designated as "g," and it is equivalent to 9.81 meters/second squared. "G," on the other hand, is the force experienced by a person due to acceleration measured in multiples of the acceleration of gravity felt at the earth's surface. A person standing on their feet on earth therefore experiences a force of +1 G. The opposite of +1 G is -1 G, the equivalent to a person standing on their head.

Sustained acceleration in the +G direction occurs very often during advanced aerobatic maneuvers, and it has received a great deal of research and attention. When a pilot experiences +G acceleration, blood flow in the body will tend to pool in the abdomen and lower extremities, leading to cerebral hypoxia, or lack of oxygen in the brain. The eyes and brain are very susceptible to low oxygen levels, and as cerebral blood pressure drops, visual, and then neurologic symptoms develop, which can lead to G-LOC.

b. G-LOC Physiology

G-LOC occurs when cerebral blood pressure and oxygen delivery to the brain are insufficient to maintain consciousness. Brain tissue has a 4-6 second oxygen reserve and G-LOC may occur if the brain does not receive oxygenated blood before its oxygen reserve is completely consumed. G-LOC is divided into two periods: absolute and relative incapacitation. Absolute incapacitation lasts anywhere from 2-38 seconds and is defined by unconsciousness. Convulsive flailing of the arms and legs can occur in up to 70% of subjects towards the end of absolute incapacitation. As G-LOC occurs, aircrew rapidly or over a few seconds unloads to +1 G due to a lack of deliberate flight control inputs during the period of absolute incapacitation, and remain there until the beginning of relative incapacitation. Relative incapacitation lasts anywhere from 2-97 seconds and is the period when the pilot regains consciousness "at which point the aircrew may initiate aggressive control inputs in an attempt to recover the aircraft".

c. Protective Measures against +G's

Physiological stresses due to +G's are well known by pilots and there are multiple training tools used to help pilots overcome the effects of +G's, including education on G-protection, proper wear of the ATAGS, performing an Anti-G Straining Maneuver (AGSM), and executing a G-Ex prior to high +G's flight.

The AGSM includes forcefully exhaling against a closed glottis (back of the throat) while simultaneously tensing leg, arm, and abdominal muscles. The purpose of the AGSM is to increase cerebral blood pressure, thereby preventing G- LOC. A properly executed AGSM will give pilots the greatest protection against +G's, conferring about +3 G's of extra protection.

A properly fitted ATAGS confers about +2 to +2.5 G's of additional protection for pilots and aircrew who are fitted or re-fitted every 120 days to maintain optimum performance. Physical conditioning is also a key point of +G's protection, given that the muscle tensing phase of the AGSM is very fatiguing, and pilots need to have optimum physical conditioning, especially in the lower extremities, in order to maintain G-endurance. Pilots are also taught to maintain optimum cardiovascular and aerobic fitness to optimize G-tolerance.

Executing a G-Ex prior to high +G flight is intended to test personal +G tolerance and assess ATAGS inflation, while also conferring additional physiological protection in the form of a cardiovascular reflex (also known as a baroreceptor reflex). When the body is subjected to greater than +1 G, a drop in cranial blood pressure results. Pressure receptors in the carotid arteries and aorta sense this drop in blood pressure and send signals to the brain to increase heart rate, contractility, and total peripheral vascular resistance to compensate. This cardiovascular reflex takes approximately 10-15 seconds to manifest itself, and lasts for about 10-15 minutes. The resultant increase in blood pressure gives the pilot approximately an additional +1 G of tolerance.

d. Human Response to –G's

–G is relatively defined as any G less than +1 G, including zero G. During any –G maneuver, blood flows rapidly headward, increasing cerebral blood pressure. The carotid and aortic baroreceptors sense this increase and rapidly respond by reducing the heart rate and widening the blood vessels in the periphery of the body. This response is scaled based on the intensity of the –G's experienced, meaning higher –G's result in lower heart rates. Symptoms of –G exposure include congestion in the head and face, headache, and reddening of vision. Humans are less tolerant to –G's than +G's, and significant cerebral impairment and damage can occur with sustained –G's, especially more than –3 G's. Apart from avoiding –G's, there are no known countermeasures to counter the resulting physiological effects. Some aerobatic pilots report the only way to compensate for sustained –G's is to relax during the maneuver to avoid further cerebral blood pressure increases. If a pilot attempted an AGSM in the –G regime, the result would be a further increase in cerebral blood pressure and a magnification of the symptoms.

e. The "Push-Pull Effect"

Pilots experience negative impacts when a period of –G flight precedes a pull to the +G regime, known as the "Push-Pull Effect". Because of the peripheral (lower body) widening of blood vessels and accompanying lowered blood pressure that occurs during –G's, a pilot's +G tolerance after sustained –G's will be greatly reduced). Whereas pilots confer an extra +1 G of protection through the cardiovascular reflex following a +G pull (as during the G-Ex), this protection is cancelled out if the pilot sustains –G's for several seconds. When a pilot rapidly transitions from sustained –G flight to +G flight within several seconds, the body is still in a low blood pressure and low heart rate regime, resulting in a rapid drop in cerebral blood pressure. The carotid and aortic baroreceptors will eventually respond to the lowered cerebral blood pressure caused by the initial +G pull, but this response takes about eight to ten seconds. This eight to ten second period is approximately two to six seconds longer than the cerebral oxygen reserves.

f. MP Exposure to –G's, "Push-Pull Effect"

During the High Bomb Burst Rejoin, the MP experienced a sustained 22 second –G regime, with an increase in –G's to a maximum of –2.06 G's in the last two seconds of that period further intensifying the physiological effects of –G flight. The MP then transitioned to a +G regime within one second and took approximately five seconds to achieve +8.56 G's. The DAS data shows a reduction in control stick pull and a lack of deliberate flight control inputs following the attainment of +8.56 G's. The five-second duration of increasing +G to a max of +8.56 G's put the MP into the G-LOC regime due to reduced blood flow to the brain. With the lack of deliberate flight control inputs, the MA rapidly unloaded to a +1 G flight regime, as expected during a period of absolute incapacitation. Five seconds later, a pull back on the control stick with simultaneous throttle advancement was recorded approximately one second prior to impact, providing evidence of a transition from absolute to relative incapacitation. The pertinent mishap times are listed below:

a. 1028:22L: Beginning of Immelmann (Max +7.9 G's)

b. 1028:36L: Beginning of inverted flight (with 22 sec duration neg G's)

c. 1028:56L: -0.90 G's recorded

d. 1028:58L: Maximum –G's: -2.06 G's

e. 1028:59L: +3.61 G's (5.67 G's/sec)

f. 1029:00L: +6.23 G's (2.62 G's/sec)

g. 1029:01L: +7.75 G's (1.52 G's/sec)

h. 1029:02L: +8.34 G's (0.58 G's/sec)

i. 1029:03L: Max +G's: +8.56 G's (0.21 G's/sec)

j. 1029:04L: Beginning of period of no deliberate flight control inputs

k. 1029:09L: Beginning of renewed flight control inputs

l. 1029:10L: Impact

g. MP AGSM Effectiveness, Previous Split-S Rejoins, Physical conditioning, ATAGS

A properly executed AGSM confers about +3 G's of additional +G tolerance. The MP underwent USAF standard centrifuge training, in 2009, IAW AFI 11-404, Attachment 3, and was graded as average on both his initial and +9.0 G's qualifications. The MP's centrifuge video recordings from those qualifications contained average AGSM performance. The MP's physiological records were current at the time of the mishap. The MP was trained to begin muscle tensing prior to pulling the aircraft into high –G maneuvers. Given the –G flight dynamics prior to the mishap maneuver, a properly executed AGSM would have increased the MP's cerebral blood pressure while under –G's, and it would have exacerbated the negative physiological effects of that condition. The MA impact destroyed the HUD tape, making a review of the AGSM used during the mishap maneuver impossible.

The AIB obtained 39 HUD tapes recorded during the January-March 2018 training season, including 29 High Bomb-Burst Rejoin maneuvers, 17 of which included audio from the intercom of the MP during flight. The audio recordings of the MP's AGSM were average with a slightly fast AGSM breath exchange (approximately every 1-2 seconds vs. recommended 3 seconds). The MP underwent a routine HUD tape review by the Thunderbirds Flight Surgeon on 24 March 2018, which noted an adequate AGSM.

During the mishap maneuver, the level of the –G's recorded in the 1-2 seconds prior to the pull for the Split-S and the maximum +G's attained during the pull for the Split-S was higher than any previously recorded and available Split-S maneuvers, predisposing the MP to reduced +G tolerance due to the "Push-Pull Effect". Furthermore, the mishap Split-S did not have any recorded lessening of the –G's prior to the control stick pull to +G for the Split-S, as previously recorded Split-S maneuvers did.

The MP had a reputation for exceptional fitness and had executed many successful high +G maneuvers in the weeks leading up to the mishap. Physical fitness is not protective against the physiological effects of –G's.

The MP's ATAGS inspections were current. His ATAGS was a size Large-Long, but based on TO 14P3-6-141, paragraph 4.1, the Table 4-1 sizing chart and the MP's waist circumference and height, the MP should have been in a size Medium-Long ATAGS. However, the above TO also states that a pilot may change to the next higher or lower ATAGS size based on individual fit. Given this information, the MP was within TO guidance regarding ATAGS fit and therefore no evidence suggests the larger size ATAGS was a factor in the mishap.

On the day of the mishap, the MP's DCC remembers the MP donning his ATAGS properly (to include engaging the comfort zippers). The DCC also testified to connecting the ATAGS to the port on the left console in the MA as the MP strapped in and checked all other straps, connections, and switches. The MF accomplished G system tests prior to takeoff. The MP also attained +7.9 G's in the Immelmann just prior to the mishap rejoin, with deliberate flight control inputs thereafter, making it likely the MA's G system was working properly during the mishap rejoin.

Chapter 4.7. STATEMENT OF OPINION

1. OPINION SUMMARY

On 4 April 2018, the mishap pilot (MP), flying F-16CM tail number (T/N) 91-0413, assigned to the United States Air Force Air Demonstration Squadron, known as the "Thunderbirds," 57th Wing, Nellis Air Force Base (AFB), Nevada (NV), engaged in a routine aerial demonstration training flight at the Nevada Test and Training Range (NTTR) near Creech AFB, NV. During the training flight, at approximately 1029 local (L) time, the mishap aircraft (MA) impacted the ground and fatally injured the MP, without an ejection attempt.

The mishap mission was planned and authorized as a practice of the "High Show" version of the Thunderbirds aerial demonstration and was flown in the Thunderbirds practice area in the south part of the NTTR. The mishap flight (MF) was a formation of six F-16CMs (Thunderbirds #1-6), the standard Thunderbirds aerial demonstration flight. Thunderbird #4 was the MA/MP. The mishap occurred after the "High Bomb Burst Cross" and during the "High Bomb Burst Rejoin," an aerial demonstration maneuver performed by the Thunderbirds in the F-16 for the past 35 years. During this maneuver, Thunderbird #1, the lead pilot/aircraft (TB1), executed 5/8 of a loop before rolling to wings level (Half Cuban Eight) as the MP flew the MA above TB1 in the opposite direction in inverted flight at no lower than the prescribed altitude of 5,500 feet above ground level (AGL). As TB1 completed the Half Cuban Eight and continued a descent, the MP initiated a descending half-loop (Split-S) to "rejoin" with TB1 into the Slot position (directly behind TB1) as Thunderbird #2, the left wing pilot, and Thunderbird #3, the right wing pilot, affected their own rejoins from their respective sides of the formation. The MP's execution of the Split-S subjected him to a significant force due to acceleration measured in multiples of the acceleration of gravity felt at the earth's surface, abbreviated as "G" or G-Force. The MA impacted the ground during the Split-S portion of the High Bomb Burst Rejoin and fatally injured the MP, without an ejection attempt. The two diagrams on the next page illustrate the MF's transition from the High Bomb Burst Cross to the High Bomb Burst Rejoin.

I find by a preponderance of evidence the cause of the mishap was the MP's G-induced loss of consciousness (G-LOC) during the Split-S portion of the High Bomb Burst Rejoin. Additionally, I find by a preponderance of evidence two factors substantially contributed to the mishap: (a) the MP's diminished tolerance to +G's induced by the physiology of exposure to –G's ("Push-Pull Effect") and (b) an associated decrease in the effectiveness of the MP's Anti-G straining maneuver (AGSM) under those conditions.

I developed my opinion by carefully considering the standard of proof for the preponderance of evidence and the requirements for causes and substantially contributing factors as I analyzed available flight data, the Lockheed Martin crash report, the mishap animation created from the Data Acquisition System (DAS), witness testimony, engineering analysis, and other information provided by technical experts. I further studied academic research on human factors relevant to the mishap and reviewed Air Force technical orders, regulations, and guidance.

2. CAUSE

I find by a preponderance of evidence the cause of the mishap was the MP's G-LOC and associated states of absolute and relative incapacitation. During these states, the MP was unable to apply appropriate flight control inputs to avoid the MA's impact with the ground or attempt an ejection.

a. Loss of Consciousness

As he initiated the Split-S at 1028:59L, the MP selected idle power on the engine throttle and pulled back on the control stick to drop the nose of the MA toward TB1 to affect the rejoin. This operation took the MA from -2.06 G's in inverted flight to a maximum of +8.56 G's at 1029:03L. Approximately one second later at 1029:04L, the MP experienced a G-LOC and stopped providing deliberate flight control inputs with the MA at 68 degrees nose low. The MP began a period of absolute incapacitation with the MA accelerating through 356 knots calibrated airspeed (KCAS) and rapidly descending through 6,556 feet mean sea level (approximately 3,510 feet AGL).

For approximately the next five seconds, the MP remained in a state of absolute incapacitation and made no deliberate flight control inputs with the MA accelerating through 415 KCAS at 60 degrees nose low and 406 feet AGL. At 1029:09L, the MP began deliberate flight control inputs as he transitioned from absolute to relative incapacitation. The MA impacted the ground at 1029:10L with the MA at 57 degrees nose low with 89 degrees of left bank at 419 KCAS, fatally injuring the MP.

The five seconds of consciousness the MP experienced after initiating the pull for the Split-S corresponds with the four to six second reserve of oxygen in the brain. The physiological impact of the pull to +8.56 G's drained the blood away from the MP's brain, causing the G-LOC to occur. The MP then stopped flying the aircraft as he entered a state of absolute incapacitation. During this state, he was unable to maneuver the aircraft as he had in all of the other times he successfully completed the maneuver. The transition to a period of relative incapacitation one second prior to ground impact enabled the MP to begin deliberate flight control inputs but his condition still included considerable confusion based on the known physiology of G-LOCs. In this short period of relative incapacitation, the MP was unable to attempt an ejection.

3. SUBSTANTIALLY CONTRIBUTING FACTORS

I find by a preponderance of evidence two factors substantially contributed to the mishap: (a) the MP's diminished tolerance to +G's induced by the physiology of exposure to –G's ("Push-Pull Effect") and (b) an associated decrease in the effectiveness of the MP's AGSM under those conditions.

a. "Push-Pull Effect"

The "Push-Pull Effect" results from a relaxed subject's exposure to –G's, the "push," prior to the onset of +G's, the "pull." Under –G conditions, the subject experiences a decrease in blood pressure, widening of the blood vessels, and a lowered heart rate. These three factors reduce the subject's resting +G tolerance in an amount directly related to the magnitude and duration of the preceding –G's.

Prior to initiating the pull for the Split-S, the MP spent approximately 22 seconds between -0.5 G's and -2.06 G's during inverted flight. In the last two seconds of the 22 second period, the –G's increased from -0.90 G's to -2.06 G's before a rapid transition to a maximum of +8.56 G's during a five-second pull on the control stick. These actions left the MP physiologically disadvantaged for the rapid onset of +G's in two specific ways. First, the effects of the sustained –G's resulted in lowered blood pressure, widened blood vessels, and lowered heart rate, negatively affecting the MP's resting +G tolerance. Second, the increasing –G's in the two seconds prior to the +G pull further slowed the MP's heart rate, magnifying the negative effect on his resting +G tolerance. The resulting outcome was more vascular space created by the widened blood vessels for the blood to flow away from the brain at the onset of the +G's and a lowered heart rate and blood pressure making it more difficult for the body to counter that dynamic.

b. AGSM

In preparation for the onset of +G's during flight, aerospace physiology instructors teach pilots to "get ahead of the +G's" by starting the AGSM before the onset of +G's. The AGSM involves squeezing the muscles of the lower body along with an inhalation of air to prepare for a forced exhalation against the back of the throat before pulling back on the control stick for rapid onset +G's. These actions result in an increase in blood flow to the brain, inflation of the lungs, and increased chest pressure. A timely and well-executed AGSM places the pilot in a better position to tolerate the physical effects caused by the increase in +G's and can add up to +3.0 G's to a pilot's resting +G tolerance. The effects of the AGSM along with the effects of an additional +2.0 to +2.5 G's protection provided by the CSU-22/P Advanced Technology Anti-G Suit (ATAGS) worn by the Thunderbirds pilots provides coverage up to the maximum +G capability of the F-16.

Although the cockpit video tape was destroyed in the mishap, I deduced from available evidence that the MP's execution of the AGSM did not provide adequate coverage for the rapid onset of +8.56 G's for two specific reasons. First, the physiological effects of the –G's experienced in the two seconds prior to the pull left the MP unable to get ahead of the rapid onset of the +8.56 G's. Timely execution of the AGSM would have created more pressure in the MP's head at the same time his body fought to lessen that pressure and would have increased the negative physiological effects of flight in the –G regime. Second, the combination of a delayed AGSM and the decrease in the MP's resting +G tolerance from the "Push-Pull Effect" lessened the overall additive +G coverage factor to compensate for the +8.56 G's the MP experienced in the pull.

I studied 29 recorded cockpit videos of the MP's successful execution of the Split-S portion of the High Bomb Burst Rejoin. In these other instances, the MP countered the physiological effects of the "Push-Pull Effect" and the +G's of the Split -S through a combination of two techniques. First, he decreased the –G's in the two seconds prior to the pull for the Split-S, causing his heart rate to increase before the pull. The decrease in –G's also provided an opportunity to "get ahead of the +G's" with a timely AGSM. Second, the MP generally flew the maneuver with a lower attained maximum +G than he experienced during the mishap. His average maximum +G in the 29 recorded cockpit video instances was +7.1 G's. In the five other recorded instances where he met or exceeded +8.0 G's in the pull (none greater than the +8.56 G's he experienced in the mishap), a decreased –G in the two seconds prior to the pull left him better positioned for a timely and effective AGSM.

4. CONCLUSION

I find by a preponderance of evidence the cause of the mishap was the MP's G-LOC during the Split-S portion of the High Bomb Burst Rejoin. Additionally, I find by a preponderance of evidence two factors substantially contributed to the mishap: (a) the MP's diminished tolerance to +G's induced by the physiology of exposure to –G's ("Push-Pull Effect") and (b) an associated decrease in the effectiveness of the MP's AGSM under those conditions.

Chapter 5. F-22A Nevada 2018.04.13

F-22A, T/N 07-4146

Joint Base Elmendorf-Richardson, Alaska

LOCATION: NAVAL AIR STATION FALLON, NEVADA

DATE OF ACCIDENT: 13 APRIL 2018

On 13 April 2018 at approximately 1745 Zulu (Z), 1045 Local (L) time, an F-22A Raptor, T/N 07-4146, assigned to the 90th Fighter Squadron, 3rd Wing, Joint Base Elmendorf-Richardson, Alaska, took off from runway 31 Left (31L) at Naval Air Station (NAS) Fallon, Nevada. The mishap pilot (MP) initiated a military power (MIL) takeoff and rotated at 120 knots calibrated airspeed (KCAS). As the MP recognized his visual cues for the mishap aircraft (MA) becoming airborne, he raised the landing gear handle (LGH) to retract the landing gear (LG). Immediately after main landing gear (MLG) retraction, the MA settled back on the runway with the MLG doors fully closed and the nose landing gear (NLG) doors in transit. The MA impacted the runway on its underside and slid approximately 6514 feet (ft) until it came to rest 9,419 ft from the runway threshold. Once the MA came to a complete stop, the MP safely egressed the aircraft. There were no injuries, fatalities, or damage to civilian property.

The Accident Investigation Board (AIB) President found by a preponderance of the evidence that the causes of the mishap were two procedural errors by the MP. First, the MP had incorrect Takeoff and Landing Data (TOLD) for the conditions at NAS Fallon on the day of the mishap, and more importantly, he failed to apply any corrections to the incorrect TOLD. Second, the MP prematurely retracted the LG at an airspeed that was insufficient for the MA to maintain flight. Additionally, the AIB President found by the preponderance of the evidence that four additional factors substantially contributed to the mishap: inadequate flight brief, organizational acceptance of an incorrect technique, formal training, and organizational overconfidence in equipment.

Chapter 5.1. ACCIDENT SUMMARY

At approximately 1745 Zulu (Z), 1045 Local (L) time, on 13 April 2018, the mishap pilot (MP), flying the mishap aircraft (MA), an F-22A Raptor, T/N 07-4146, took off from runway 31 Left (31L) at NAS Fallon, Nevada for a TOPGUN graduation exercise. The MP initiated a military power (MIL) takeoff and rotated at 120 knots calibrated airspeed (KCAS). Rotation occurs when the pilot initiates back stick pressure to lift the nose of the aircraft off the ground and set the takeoff pitch attitude. Once the MP recognized his visual cues for takeoff, he raised the landing gear handle (LGH) to retract the landing gear (LG). After main landing gear (MLG) retraction, the MA impacted the runway with all but the nose landing gear (NLG) doors fully closed.

The MA impacted approximately 2,905 ft from the runway threshold on the centerline and slid approximately 6,514 ft until it came to rest 9,419 ft from runway threshold. While the MA was sliding down the runway, the MP shut off both engines. Once the plane was at a complete stop, the MP safely egressed the MA. There were no injuries, fatalities, or damage to civilian property.

Chapter 5.2. SEQUENCE OF EVENTS

a. Mission

The mission was scheduled and briefed as a TOPGUN graduation exercise sortie. The mission was to take off from NAS Fallon and fly to a predesignated point in the assigned airspace in order to fight BFM against a Navy F-18 Hornet, piloted by a TOPGUN student. This mission would include advanced maneuvering, including aggressive gravitational forces imposed on each pilot during the fight. The MP's callsign was TOPGUN65, and he was flying as a single-ship for the departure with the intent to join with his opponent in the airspace.

b. Planning and Preflight

The MP's duty day began with a mass brief at 0800L, given by a local Navy pilot. All participants in the exercise were briefed on local operating procedures, as well as the weather, Notices to Airmen (NOTAMS), and Special Interest Items (SIIs). Participants planned to fly a Visual Flight Rules (VFR) departure in accordance with (IAW) the brief and their specific lineup card. The brief focused on the unfamiliar airspace, the VFR departure, and collision avoidance with other aircraft, both on the departure and during the fight. No applicable NOTAMS were active for the airfield. None of the 90 FS pilots interviewed noted anything abnormal about the brief.

The four 90 FS pilots conducted a flight brief after the mass brief and discussed hydration, high-G maneuvering, airspace deconfliction, entry and exit procedures, as well as normal risks and how to mitigate them in accordance with the SIIs. An Operational Risk Management (ORM) sheet was not filled out due to being TDY. Takeoff and Landing Data (TOLD) was not computed IAW applicable technical order data (TOD) for the conditions at NAS Fallon on the day of the mishap, and the TOLD displayed on the MP's lineup card was incorrect.

Following the flight brief, the MP and Pilot Member 3 (PM3) had about 45 minutes prior to stepping to the aircraft. The MP and PM3 went to get some water and food before returning to the hangar. During this time, the two pilots discussed the upcoming mission and PM3 noted that the MP seemed prepared and comfortable with the mission. The MP then donned his flight gear and stepped to the aircraft. The MA's preflight was accomplished IAW all applicable technical order procedures, and no deficiencies were noted. Ground and taxi operations for the sortie were uneventful.

c. Summary of Accident and Impact

The MP started engines at 1024L. At 1036L, the MP was cleared to taxi to runway 31L and proceeded to taxi without incident. The MP was subsequently cleared for takeoff and then advanced the throttles to MIL to begin his takeoff sequence. All actions up to this point were uneventful.

The MP accelerated down the runway until reaching a speed of 120 KCAS, at which point he began his rotation sequence by applying slight aft stick pressure to pull the nose to a 10-degree pitch attitude. The aircraft continued to accelerate and at 135 KCAS the weight-on-wheels switch indicated that the aircraft was lifting off of the ground. As the MA accelerated to 142 KCAS, the MP recognized his visual cues for takeoff and retracted the LG. The LGH was raised 1.0 second after the weight-on-wheels switch indicated "off". As the LG retracted, the aircraft reached a maximum speed of 148 KCAS. At approximately this time, and at 2,905 ft from the runway threshold, the aft section of the aircraft made contact with the runway and the nose of the aircraft began to drop down. Approximately one second later the MA's belly had completely made contact with the runway surface.

As the MA contacted the runway, the MP selected maximum afterburner (AB) thrust for one second then reduced the throttles to idle as the MA fully abutted the runway. Both throttles were reduced so quickly that neither engine actually initiated AB. At 4,877 ft from the runway threshold, the MP lowered the tail hook IAW abort procedures. As the MA slid down the runway, the MP shut off both engines. The tail hook continued to intermittently impact the runway surface until the aircraft came to a complete stop 9,419 ft from the runway threshold and offset several feet to the right of the runway centerline.

d. Egress and Aircrew Flight Equipment (AFE)

The MA stopped on the runway 9,419 ft from the runway threshold. The MP then raised the canopy and safely egressed the aircraft. Emergency crews responded and the scene was contained without any indication of fire and without injury to the MP.

The MP's aircrew flight equipment (AFE) inspections were current and deemed serviceable by the 3rd Operations Support Squadron (OSS) AFE personnel. The MP wore all required flight equipment for the mission and there were no indications of any malfunctions with the equipment during the mishap.

e. Search and Rescue (SAR)

This section is N/A for this mishap.

f. Recovery of Remains

This section is N/A for this mishap.

Chapter 5.3. MAINTENANCE

a. Forms Documentation

The F-22A features a digital forms documentation process located on the Integrated Maintenance Information System (IMIS). Data on IMIS is input directly onto portable maintenance aid laptops by personnel who utilize an aircraft forms drive as they perform each task. The data is then uploaded to a master IMIS server. The Integrated Maintenance Database System (IMDS) is an additional management information system used by the USAF which contains F-22 data transferred from IMIS. After the mishap, the Safety Investigation Board (SIB) secured the MA's forms drive. A comprehensive 30-day review on the MA's IMIS and IMDS records showed that the aircraft was deemed mission capable and airworthy on the day of the mishap.

b. Inspections

In the 24 hours prior to the mishap, the following maintenance tasks were performed: A 50-hour scheduled inspection on the aircraft refueling door latch, an auxiliary power unit bay hydraulic clamp inspection, and a left and right engine oil servicing door latch inspection. Upon arrival at NAS Fallon, JBER maintenance personnel performed a basic post-flight/pre-flight inspection. Specifically, they completed a pre-flight walk around of the entire aircraft, engine oil sampling and servicing, and left and right engine inlet/exhaust inspections. A fuel top-off to 17.4K pounds (lbs) was performed utilizing a NAS Fallon fuel truck IAW applicable TOD. Servicing checks were accomplished on the stored energy system, MLG tire pressure, system one and two hydraulic fluid levels, fuel quantity, automatic breathing oxygen system, and weapons stations. Of the items checked, only the stored energy system, the #2 engine oil level, and the station nine Advanced Medium Range Air to Air Missile (AMRAAM) Vertical Ejection Launcher (AVEL) required servicing. On the morning of the mishap, servicing checks were re-accomplished with no changes noted. All aerospace ground equipment (AGE) used to service safety of flight systems was evaluated and verified to be in good working order.

c. Maintenance Procedures

Preflight inspections were accomplished IAW applicable TOD.

d. Maintenance Personnel and Supervision

No maintenance personnel or supervision issues were identified.

e. Fuel, Hydraulic, Oil, and Oxygen Inspection Analyses

Post-mishap samples of engine oil and hydraulic fluid were pulled from the MA for analysis at the Air Force Petroleum Lab at Wright-Patterson Air Force Base (WPAFB), Ohio. Testing of the samples did not reveal any abnormal findings for in-use fluids. Samples of JET-A from the Tyndall AFB and NAS Fallon fuel trucks that serviced the MA on the day prior to the mishap were tested, and all were within normal limits. There are no records of fuel samples being taken from the MA. There are also no records of fuel samples from the fuel trucks used at the two intermediate stops, Sheppard AFB and Colorado Springs Municipal Airport.

Sensors in multiple locations monitor the oxygen system of the F-22A. On 23 February 2018, a scheduled 90-day breathing system test was performed on the MA's oxygen system indicating zero abnormalities. On the day of the mishap, the MA detected no oxygen system faults during the sortie. While oxygen and air pressure sensors actively monitor the system's performance, they are located outside of the Breathing Regulator/Anti-G (BRAG) valve. To further rule out any mechanical factors related to the breathing system, the BRAG valve and pilot breathing hose were removed for evaluation. There is no indication that these parts contributed to the mishap.

f. Unscheduled Maintenance

In the 96 hours prior to the mishap, four unscheduled maintenance tasks were accomplished. One involved troubleshooting an Electronic Warfare Software anomaly on 10 April 2018, which required no physical maintenance actions and cleared with a reset of the system. Additionally, Low Observable (LO) coating evaluations were accomplished after flights on 9 April 2018 and 10 April 2018 and were deemed unrelated to safety of flight. On 9 April 2018, the MA landed with a "seat not armed" indication, which was repaired by replacing the "seat not armed" light switch.

Chapter 5.4. AIRFRAME, MISSILE, OR SPACE VEHICLE SYSTEMS

a. Structures and Systems

Data Transfer Cartridge & Crash-Survivable Memory Unit:

The F-22A contains a fault reporting and health monitoring system in which data is captured and ultimately recorded on the Data Transfer Cartridge (DTC). The DTC records raw performance data from aircraft subsystems collected throughout the sortie and is utilized for post-mission troubleshooting. Similar to the DTC, the Crash Survivable Memory Unit (CSMU) onboard the aircraft collects approximately two hours of data on aircraft performance and is used to determine the events leading up to the crash of an aircraft. On 12 April 2018, the DTC on the MA malfunctioned and was unable to record data for the cross-country sorties from Tyndall AFB to NAS Fallon. However, the MA had a functioning DTC during the mishap sortie on 13 April 2018. The CSMU functioned normally and recorded data for the sortie from Colorado Springs to NAS Fallon and for the mishap sortie

The LG system on the F-22 consists of a single NLG and two MLG assemblies. Each MLG provides inputs to a system in the aircraft through two weight -on-wheels switches designed to sense when the aircraft becomes airborne. Sensors on the strut unlock the LGH to allow LG retraction when weight off wheels is detected. The associated brake system is controlled electronically through rudder pedal inputs utilizing hydraulic pressure. Both MLG shock struts were last serviced on 13 January 2018. During the mishap sortie the MLG and MLG doors were fully retracted and closed before the MA impacted the runway with the only damage sustained from sliding down the runway. The NLG was fully retracted, but the NLG doors contacted the runway while closing.

The F-22 is powered by two Pratt & Whitney F-119-PW-100 turbofan engines. The engines provide thrust levels sufficient to sustain supersonic flight without the use of AB. The MA's DTC indicated that both throttles were set at MIL for the takeoff sequence, with revolutions per minute (RPM) parameters reading normal through engine start, taxi, and takeoff. Performance data retrieved from the MA indicated the engines were performing normally from engine start through shutdown. The AIB Maintenance Recovery Team (MRT) accomplished full borescopes of the left and right engines and no abnormalities were discovered.

A visual disparity between the left and right engine nozzle positions was noted after the mishap. During a typical engine shut down with a positive weight-on-wheels indication, the nozzles are commanded to a full open and locked position. During flight, the nozzles are commanded by one of the aircraft's systems based on current flight conditions. With an in-flight engine shutdown, the nozzles will "float" as opposed to being locked in the full open position as during a ground shutdown. During the mishap, the MA transitioned to an in-flight state when the LG retracted. Therefore, when the engines were subsequently shut off while the MA was sliding down the runway, the engines responded IAW an in-flight shutdown and allowed the nozzles to float. Rather than being commanded to the fully open and locked position as prescribed during a normal ground shutdown, in this situation, both nozzles remained dynamic and continued to move until the aircraft came to a complete stop.

b. Evaluation and Analysis

An AIB MRT provided additional support in evaluating the MA at NAS Fallon. The team identified a right alpha probe transducer with multiple small nicks within the first two inches. It is unclear whether the damage occurred before, during, or after the mishap. IAW TOD, this is a non-airworthy condition and would cause an aircraft to be grounded. The alpha probe is used by the F-22 to calculate speed, angle of attack, and angle of sideslip. The right alpha probe was removed for non-destructive evaluation with no significant findings.

Additional analysis was performed on the following components to rule out causality in relation to the mishap. Further evaluation of these items has not highlighted any issues of significant concern in relation to the root cause of the mishap:

-Side Stick Controller Assembly

-BRAG Valve

-Pilot Breathing Hose

Chapter 5.5. WEATHER

a. Forecasted and Observed Weather

The NAS Fallon forecasted weather at the scheduled takeoff time for the mishap was: calm winds, visibility of 10 statute miles (SM), few clouds at 8000 ft above ground level (AGL), no weather hazards, and an altimeter setting of 30.45 inches of mercury (in Hg). The forecasted temperature was 8 degrees Celsius (C) and the dew point temperature was -6 degrees C, which set the condition of the airfield as normal on the Index of Thermal Stress (ITS).

b. Space Environment

This section is N/A for this mishap.

c. Operations

This section is N/A for this mishap.

Chapter 5.6. HUMAN FACTORS ANALYSIS

a. Introduction

Human factors contributing to this mishap were evaluated using the Department of Defense Human Factors Analysis and Classification System, 01 October 2015 (DoD-HFACS). This guide is designed for use as a comprehensive event/mishap, human error investigation, data identification, analysis and classification tool. It is designed for use by all members of an investigation board in order to accurately capture and recreate the complex layers of human error in context with the individual, environment, team and mishap or event. The following human factors were relevant to the mishap:

b. AE103 Procedure Not Followed Correctly:

Procedure Not Followed Correctly is a factor when a procedure is performed incorrectly or accomplished in the wrong sequence.

(1) Incorrect Application of TOLD

A normal F-22 takeoff sequence begins with the pilot advancing the throttles and accelerating to the computed rotation speed. The pilot then applies slight aft stick pressure to raise the nose to 10-12 degrees pitch attitude. While holding this pitch attitude, the aircraft will become airborne at the computed takeoff speed. The computed rotation and takeoff speeds vary based on weight of the aircraft and pressure altitude and are calculated prior to takeoff. For the MA on the day of the mishap, the rotation speed and takeoff speed should have been 143 KCAS and 164 KCAS respectively. However, the MP rotated at 120 KCAS, and the MA first registered weight off wheels at 135 KCAS. The MA momentarily became airborne, but there was insufficient lift for the MA to maintain flight.

(2) Prematurely Raised Landing Gear Handle

A normal F-22 takeoff ends when the pilot ensures that a positive rate of climb is established and retracts the LG. Common indicators of a positive rate of climb in the F-22 include visual cues, the climb dive marker (CDM) above the horizon, and an increasing vertical velocity indicator (VVI). Takeoff should occur at calculated takeoff speed, and LG should be retracted after the airplane is safely airborne. Therefore, LG retraction should not occur prior to takeoff speed.

During the mishap sortie, after rotation and achieving weight off wheels, the MP described using peripheral vision, and the surroundings getting smaller to determine he was airborne. The MP quickly retracted the LG upon recognizing those visual cues. He did not utilize the CDM or VVI to verify a positive rate of climb. While the MP sensed that the MA was airborne and raised the LGH 1.0 second after weight off wheels, the MA's speed was 22 knots below takeoff speed. The lift being generated at this point was insufficient to maintain flight, which resulted in the MA settling back to the runway on its belly.

(3) Damage to Alpha Probe

Per TOD, before every flight, one qualified crew chief is required to inspect the left and right alpha probes for damage or obstruction. Damage is defined by "noticeable to the touch by rubbing hand or thumb nail over suspected damage area". If either probe is damaged, the jet is considered to be non-mission capable and the jet is to be grounded pending further maintenance action. On the day of the mishap, the MA was inspected, but no damage was noted. The AIB MRT identified a right alpha probe transducer with multiple small nicks within the first two inches. It is unclear, however, when this damage occurred.

c. PC109 Distraction

Distraction is a factor when the individual has an interruption of attention or inappropriate redirection of attention by an environmental cue or mental process. During previous sorties flown, the MP had consistent timing of LG retraction. During five sorties flown over a five-month period prior to the mishap, the MP's LG retraction timing was comparable to his peers; his rates averaged 5.6 seconds after initiating rotation and 2.1 seconds after weight-off-wheels indication. For each sortie flown from a sea level airfield, the MP retracted the LG after the aircraft had achieved takeoff speed. During the mishap sortie, the MP retracted the LG twice as fast as his usual timing after weight off wheels. During the interview of the MP, he did not indicate any stressors or distractions in the cockpit during the mishap takeoff sequence. He noted some fatigue, but not excessive fatigue that would affect safety of flight. The MP also stated that there were no aircraft systems issues on the day of the mishap, and ground operations prior to takeoff were normal. No abnormal radio calls were made during his taxi or takeoff sequence. Although the MP did not remember any specific distractions, it is worth noting that the timing of his LG retraction was faster than his previous sorties.

d. PP109 Task or Mission Planning or Briefing Inadequate

Task or Mission Planning or Briefing Inadequate is a factor when an individual, crew or team fails to complete all preparatory tasks associated with planning or briefing the task or mission.

(1) Incorrect TOLD

Most mission planning for the Fallon TDY was completed earlier in the week while the 90 FS was TDY to Tyndall AFB for WSEP. During mission planning, PM1 created line-up cards for each of the three cross-country sorties and the sortie at NAS Fallon. The TOLD on all four cards was based on an 80 degrees Fahrenheit (F) day and was not re-calculated for each airfield during the cross-country trip. The TOLD on the cards was computed using a 90 FS Excel spreadsheet tool that assumes JBER conditions including sea level elevation and a 10,000 foot runway length. The 90 FS tool was created to increase mission planning efficiency as it allows the user to skip manually calculating TOLD for each mission. However, at NAS Fallon, the field elevation is 3,934 feet and the runway length is 13,961 feet. Additionally, PM1 used a temperature of 80 degrees F whereas the temperature on the day of the mishap was 46 degrees F. Therefore, the TOLD on the MP's line-up card was incorrect for the mishap sortie at NAS Fallon.

(2) Inadequate Flight Briefs

IAW AFI 11-2F-22v3 paragraph 2.4.1, flight leads are responsible for presenting a logical briefing that will promote safe, effective mission accomplishment. This AFI also specifically states that a briefing will "review takeoff data, and ensure every member of the flight understands it". A briefing was conducted on each leg of the cross-country, but did not cover the specific TOLD considerations for the mission airfields.

On the day of the mishap, a mass brief was conducted from 0800-0820L for all TOPGUN graduation exercise participants during which the local operating procedures, weather, NOTAMS, and SIIs were covered. There was not a formal brief among the four 90 FS pilots, though they did have informal discussions at breakfast and prior to entering their respective jets. During that time, they discussed hydration, procedures to get to the airspace, airspace deconfliction, and high-G maneuvering However, at no point did the pilots discuss TOLD considerations.

e. SI007 Failed to Identify Unsafe Practices

Failed to Identify Unsafe Practices is a factor when a supervisor fails to identify unsafe tendencies and fails to institute remedial actions. This includes hazardous practices, conditions or guidance.

(1) Improper Rotation Technique

The MP stated, "There is a technique that I heard from somewhere (I don't know where, whether it was at the B-Course or the 90th) to initiate [rotation] – if you have a 136 [rotation speed], kind of standard below 2,000 feet – that you initiate aft stick pressure at 120 so that the nose is up at that rotation speed, and that has been my habit pattern". Data from five sorties flown over a five-month period prior to the mishap clearly shows that the MP initiated rotation at 120±5 KCAS.

This technique of rotating early does not appear to be limited to the MP. The data shows that in

64.3% of sorties, rotation was initiated greater than 5 knots prior to the calculated rotation speed; in 52.1%, rotation occurs at 120±5 KCAS. In 80.4% of these sorties, takeoff was accomplished greater than 5 knots prior to takeoff speed. All pilots who were interviewed noted that they check their TOLD before takeoff. After the mishap, at a pilot meeting attended by 20 to 30 F-22 pilots, about half noted that they consistently use an early rotation technique. There is a clear trend of rotating early among a significant number of F-22 pilots, including the MP, despite being aware of computed TOLD.

Rotating early has two major negative effects on TOLD. First, by rotating early you are increasing your induced drag at a premature point, thus slowing down the jet's acceleration and extending your takeoff roll. This invalidates the abort speeds that are calculated by the applicable technical order. More importantly in the case of this mishap, early rotation usually leads to getting airborne prematurely in ground effect, which is the effect of additional buoyancy produced by a cushion of air below a vehicle moving close to the ground. The AIB discovered that 80.4% of all pilots sampled became airborne greater than 5 knots before achieving their takeoff speed. At sea level, this technique doesn't "hurt" the pilot substantially because of the acceleration and power of the F-22; however, it builds a bad habit which can be compounded when flying at high elevation airfields. This technique has further consequences when the pilot retracts the LG too early. Becoming airborne in ground effect can have similar visual signals to becoming airborne at the correct takeoff speed, resulting in the pilot initiating LG retraction. The technique of rotating early has led to 26.8% of sampled pilots retracting their LGH prior to achieving takeoff speed, and 10.7% of those pilots retracting their LGH over 10 knots slower than their takeoff speed. This technique can create a situation where the LG is retracted prior to their aircraft achieving a safe, flyable airspeed.

Because every F-22 base (except Nellis) is at sea level, F-22 pilots do not have much experience taking off at high elevation airfields. It should be noted that while taking off at a high elevation airfield such as Colorado Springs (KCOS), Sheppard AFB (KSPS), and NAS Fallon, there are no observed changes to any of the sampled pilots' rotation speeds or takeoff speeds. Every pilot continued to fly the aircraft as if he were taking off at his home airfield, with many still using the incorrect technique of rotating at 120 knots regardless of TOLD. This caused 91% of the aircraft to become airborne ≥5 knots prior to achieving takeoff speed, with 54.5% of them becoming airborne at least 20 knots early. By focusing only on these cross-country sorties, we see that 81.8% of the pilots retracted their gear prior to achieving takeoff speed at these high elevation airfields. This data suggests that pilots are not referencing their airspeed prior to retracting the gear, but instead relying on a visual sensation of the aircraft leaving the ground, as well as having an "internal clock" which tells them when to retract the gear based off of "experience". Because acceleration is slower at high elevation airfields, it takes noticeably longer to accelerate to the required takeoff speed. Specifically, during the mishap, the MA's military thrust was approximately 87% what it would have been at sea level. It should be noted that in 72.7% of these cases, the pilots retracted their gear prior to even achieving a takeoff speed that would have been normal at sea level, which continues to suggest that they are not referencing airspeed data even while flying at sea level. This has put many pilots and aircraft at an unnecessary risk.

f. OP004 Formal Training

Formal Training is a factor when one-time or initial training programs, upgrade programs, transition programs or other training that is conducted outside the local unit results in undesirable outcomes. The F-22 B-Course teaches pilots the fundamentals of flying the F-22. Data from multiple sorties from two recent B-Course classes was analyzed by the AIB. This sample set showed that 64.3% of the students rotated greater than 5 knots below the computed rotation speed and 44.0% rotated at 120±5 KCAS. The data shows that 100% of the students retracted their LG after achieving takeoff speed. There is a clear trend of rotating early among a significant number of F-22 student pilots at the B-Course.

g. OC003 Organizational Overconfidence in Equipment

Organizational Overconfidence in Equipment is a factor when there is organizational overconfidence in an aircraft, vehicle, device, system, or any other equipment. The F-22 engines produce more thrust than any other current fighter engine. Most pilots acknowledged that the high thrust of the aircraft provides confidence that the jet will easily get airborne. One pilot commented that the F-22 community "takes it for granted that we have a lot of power and that this jet will generally take off from any runway that you want it to take off from". Another commented, "I can't think of a time where I've been concerned with TOLD. .. based on the thrust available". Multiple pilots, including the MP, noted that the TOLD is emphasized more in the T-38 community than the F-22. Due to the lower thrust to weight ratio of the T-38, adherence to TOLD is more critical for safety of flight. There is a clear perception among F-22 pilots that the aircraft has sufficient thrust and braking capability to overcome deviations from TOLD. This perception has led to a decreased emphasis on TOLD.

Chapter 5.7. STATEMENT OF OPINION

1. OPINION SUMMARY

On 13 April 2018 at approximately 1745 Zulu (Z), 1045 Local time (L), an F-22A Raptor, T/N 07-4146, assigned to the 90th Fighter Squadron, 3rd Wing, Joint Base Elmendorf-Richardson, Alaska, took off from runway 31 Left (31L) at Naval Air Station (NAS) Fallon, Nevada. The mishap pilot (MP) initiated a military power (MIL) takeoff and rotated at 120 knots calibrated airspeed (KCAS). As the MP recognized his visual cues for the MA becoming airborne, he raised the landing gear handle (LGH) to retract the landing gear (LG). Immediately after main landing gear (MLG) retraction, the mishap aircraft (MA) settled back on the runway and with the MLG doors fully closed and the nose landing gear (NLG) doors in transit. The MA impacted the runway on its underside and slid approximately 6514 feet (ft) until it came to rest 9,419 ft from the runway threshold. Once the MA came to a complete stop, the MP safely egressed the aircraft. There were no injuries, fatalities, or damage to civilian property.

The mishap occurred on the MP's only scheduled sortie for the day. This mission was scheduled and briefed as a TOPGUN graduation exercise sortie. The MP's mission was to take off from NAS Fallon and fly to a predetermined point in the assigned airspace in order to fight Basic Fighter Maneuvers (BFM) against a Navy F-18 Hornet. The MP was flying as a single-ship for the departure with the intent to meet his opponent in the airspace. The day was uneventful up to the point when the MP initiated takeoff.

I find by a preponderance of the evidence that the causes of the mishap were two procedural errors by the MP. First, the MP had incorrect Takeoff and Landing Data (TOLD) for the conditions at NAS Fallon on the day of the mishap, and more importantly, he failed to apply any corrections to the TOLD during his takeoff sequence. Second, the MP prematurely retracted the LG at an airspeed that was insufficient for the MA to maintain flight.

I find by a preponderance of the evidence that four additional factors substantially contributed to the mishap: inadequate flight brief, organizational acceptance of an incorrect technique, formal training, and organizational overconfidence in equipment.

2. CAUSE

a. Incorrect Application of TOLD

During mission planning for the cross-country flights, including the sortie at NAS Fallon, all of the lineup cards produced for the formation listed TOLD for a military power (MIL) takeoff at 80 degrees Fahrenheit (F) using a 10,000 ft runway at sea level. The elevation of NAS Fallon is 3,934 ft, runway 31L is 13,961 ft long, and the temperature on the morning of the mishap was 46 degrees F.

The rotation and takeoff speeds listed on the lineup card were 136 KCAS and 163 KCAS respectively. The calculated rotation and takeoff speeds for the conditions at NAS Fallon on the day of the mishap are 143 KCAS and 164 KCAS respectively.

In addition to having incorrect TOLD, the MP failed to apply any corrections to the TOLD. The MP stated that he understands the effects increased density altitude will have on TOLD (increased airspeeds and distances), but he still performed his normal technique of rotating at 120 KCAS. Not applying any corrections to the TOLD allowed the MA to get to a position where the MP sensed his visual cues for becoming airborne, but the MA had not accelerated to a sufficient speed to maintain flight.

b. Prematurely Retracted the Landing Gear

Takeoff should occur at calculated takeoff speed and the LG should be retracted after the aircraft is safely airborne and the pilot ensures a positive rate of climb is established. Therefore, LG retraction should not occur prior to takeoff speed. While the MP observed his visual cues, he did not confirm a positive rate of climb by crosschecking the climb dive marker or the vertical velocity indicator. The MP raised the LGH 1.0 second after weight off wheels at an airspeed of 142 KCAS; 22 knots below the correct takeoff speed. The MA was not at an appropriate flying airspeed and the aircraft settled back on the runway as the LG retracted.

3. SUBSTANTIALLY CONTRIBUTING FACTORS

a. Substantially Contributing Factor 1: Inadequate Flight Brief

Flight leads are responsible for presenting a logical and thorough brief to promote a safe and effective mission. Among other required items, flight leads will brief TOLD and ensure each member of the flight understands it. During each of the cross-country sorties, including the sorties at NAS Fallon, an abbreviated flight brief was conducted, but the designated flight lead never briefed or discussed TOLD for any of the airfields. All four pilots involved in the cross-country were flight lead qualified. Although they all stated that they understand the effects of increased density altitude on TOLD and aircraft performance, none of them recalculated TOLD or discussed TOLD considerations for the high elevation airfields at Colorado Springs and NAS Fallon.

b. Substantially Contributing Factor 2: Organizational Acceptance of an Incorrect Technique

The improper technique to rotate 10-15 knots prior to the calculated rotation speed appears to be common among F-22 pilots. Given that all F-22 bases but one are at sea level, the TOLD does not vary much between each base and a calculated rotation speed of 136 KCAS is common. Data for 56 sorties from the 90th Fighter Squadron (90 FS) was analyzed and 52% of the pilots rotated at 120±5 KCAS. However, every pilot interviewed stated that they review the TOLD prior to takeoff. The early rotation starts a sequence of events that can lead to early takeoff and early LG retraction.

c. Substantially Contributing Factor 3: Formal Training

The MP stated that he does not remember where he learned the technique to rotate early, either during the B-Course at Tyndall AFB, Florida or in the 90 FS. Therefore, a sample of 28 sorties from the two previous B-Course classes was analyzed. The analysis showed that 44% of the students rotated at 120±5 KCAS. Consequently, it is likely that this technique is being taught at the B-Course.

d. Substantially Contributing Factor 4: Organizational Overconfidence in Equipment

The F-22 produces a significant amount of thrust and most pilots acknowledged that the high thrust provides confidence that the jet will easily get airborne. It is clear that TOLD is not emphasized as much in the F-22 as in lower thrust-to-weight ratio aircraft, and the main considerations in the F-22 are for the abort speed and the landing data. There is a definite perception among F-22 pilots that the aircraft has sufficient thrust and braking capability to overcome deviations from TOLD. This perception has led to a decreased emphasis on the takeoff data.

4. CONCLUSION

By the preponderance of evidence, I find the cause of the mishap was pilot error. The MP failed to ensure that he was operating the aircraft IAW valid TOLD and then prematurely retracted the LG. If the MP had performed his takeoff sequence IAW the correct TOLD or if he delayed his LG retraction until the MA had accelerated to the correct takeoff speed, this mishap would not have occurred. I also find by the preponderance of evidence that four additional factors substantially contributed to the mishap: inadequate flight brief, organizational acceptance of an incorrect technique, formal training, and organizational overconfidence in equipment.

Although this mishap occurred due to the specific procedural errors of the MP, the organization factors contributing to this mishap were significant in influencing and shaping the MP's actions. The technique of rotating early will not by itself cause this type of accident. However, rotating early starts a sequence of events that can lead to an early takeoff and early gear retraction. This situation is magnified when an aircraft is operating at a high elevation airfield where aircraft performance is decreased.

Chapter 6. F-15C Kadena 2018.06.11

F-15C, T/N 84-0008

KADENA AIR BASE, JAPAN

LOCATION: NEAR KADENA AIR BASE, JAPAN

DATE OF ACCIDENT: 11 JUNE 2018

On 11 June 2018, at approximately 0617 hours local time (L), the Mishap Aircraft (MA), an F-15C, T/N 84-0008, assigned to the 44th Fighter Squadron (44 FS), 18th Wing (18 WG), Kadena AB, Japan, crashed into the Pacific Ocean approximately 70 miles south of Kadena Air Base. The MA broke apart upon impact with a loss valued at $42,360,014.00. The Mishap Pilot (MP) ejected from the MA and sustained serious injuries. Japan Air Self Defense Force (JASDF) rescue forces flying a UH-60J helicopter, from Naha International Airport, rescued and transported the MP to a military hospital at Camp Foster, Japan. There were no fatalities or damage to civilian property. There was media interest as reported by local, national, and international agencies.

The MP was flying as lead of a two-ship formation during a dissimilar basic fighter maneuver (BFM) sortie with an F-22A, assigned to the 525th Fighter Squadron. While maneuvering defensively in relationship to the Mishap Wingman (MW), at approximately 5,400 feet mean sea level (MSL) and 180 knots indicated airspeed (KIAS), the MP initiated a vertical climb to 65 degrees nose high, 20 degrees of right bank, 39 degrees Angle-of-Attack (AOA), and 1.2 Gs, which apexed near 6,300 feet MSL and 105 KIAS, before a significant nose drop occurred. The MP perceived the MA was not tracking as desired and initiated an unload of approximately one fist-width's forward stick with full right rudder. The nose pitched down and to the right to 65 degrees nose low, 110 degrees of right bank, -26 degrees AOA and G forces decreasing from 1.2 to -0.3 Gs. With right rudder still commanded, the MA experienced a negative G departure from controlled flight with a snap roll entry to the left that transitioned to an inverted, negative G spin. The MP received no indications of hydraulic, electrical, fuel, engine, structural, or flight control system malfunctions. The MP was unable to recover the MA and ejected at approximately 1,100 feet MSL.

The Accident Investigation Board (AIB) President found, by a preponderance of the evidence, the cause of the mishap was the MP's improper application of forward stick with full right rudder, which resulted in a negative G departure from controlled flight due to the coupling of aerodynamic forces of yaw and roll.

Additionally, the AIB President found by a preponderance of the evidence that spatial disorientation, lack of emergency procedure training for negative G departures from controlled flight, and limited time to analyze the situation and recover substantially contributed to the mishap.

Chapter 6.1. ACCIDENT SUMMARY

On 11 June 2018, at approximately 0617 hours local time (L), the Mishap Aircraft (MA), an F-15C, T/N 84-0008, assigned to the 44th Fighter Squadron (44 FS), 18th Wing (18 WG), Kadena AB, Japan, crashed into the Pacific Ocean approximately 70 miles south of Kadena AB.

The MA broke apart upon impact with a loss valued at $42,360,014.00. The Mishap Pilot (MP) ejected from the MA and sustained serious injuries. Japan Air Self Defense Force rescue forces flying a UH-60J helicopter, from Naha International Airport, rescued and transported the MP to a military hospital at Camp Foster, Japan. There were no fatalities or damage to civilian property. There was media interest as reported by local, national, and international agencies.

Chapter 6.2. SEQUENCE OF EVENTS

a. Mission

The mission on 11 June 2018 was planned with the flexibility to be flown as either a two aircraft BFM sortie or a three aircraft Air Combat Maneuvers (ACM) sortie, pairing F-15Cs from the 44 FS and F-22As from the 525 FS, as part of a two squadron surge. The mission was the first of three sorties the MP was scheduled to fly that day. The operations supervisors in the respective squadrons properly authorized the flights. The MP's mishap aircraft (MA) was an F-15C, T/N 84-0008.

b. Planning

The mission was properly planned and the mass briefing covered the required topics, to include high aspect BFM (HABFM) setups. HABFM typically starts between 18,000 feet and 20,000 feet Mean Sea Level (MSL) and at 400 to 440 knots indicated airspeed (KIAS), tactical formation, line abreast. A fight floor of 5,000 feet above MSL was briefed for HABFM. Weather and Notices to Airmen (NOTAM) were reviewed, and the briefing lasted approximately 15-20 minutes.

An F-15C flight lead, MB, gave the mass briefing. All F-22A and F-15C pilots flying that morning were in the mass briefing with the ability to pair as two or three aircraft formations during any of the three planned sorties. The 44 FS Commander and the 525 FS Director of Operations were scheduled to fly that morning and attended the mass briefing.

c. Preflight

The MP had an appropriate 15-20 minutes between the mass brief and step brief. The MP reported nothing abnormal with the MP's flight gear and signed the Aircrew Flight Equipment (AFE) log for accomplishing the AFE preflight. The assigned Operations Supervisor, PW5, gave the step brief by recapping highlights from the mass briefing, covering airfield status, Operational Risk Management (ORM) and assigned aircraft for each pilot. PW5 addressed the increased stress/challenges at home on the MP's ORM worksheet. The MP woke up once during the night to care for MP's young daughter. The MP had adequate pilot rest with six to seven hours of sleep and the overall risk on the ORM worksheet was still Low. The MP arrived at the MA and performed a normal preflight; there were no discrepancies in the aircraft forms that would hinder a BFM mission. The MP accomplished a full visual inspection of the aircraft and did not find any cracks or loose bolts. The MA was in a clean configuration with no external wing tanks, one captive carry inert AIM-9X on the left wing pylon and one Kadena Instrumentation Training System (KITS) pod on the right wing pylon.

The MP performed a normal engine start and pre-taxi procedures. The MA passed all flight control checks by utilizing mirrors and the crew chief. After taxiing to the end of runway area, the PW5 paired MP with MW, a current and qualified F-22A instructor pilot (IP) flying an F-22A.

d. Summary of Accident

Evidence for accident reconstruction was limited to the KITS data, MP and MW testimony. The Removable Memory Module, which contains video and audio from the MA cockpit, was not recovered. The Flight Data Recorder with the Crash Survivable Memory Unit was recovered, but contained only manufacturer test data and no data from the actual MA due to faulty wiring during installation. Aircraft trajectory acquired from KITS was further analyzed by Boeing engineers to estimate rates and accelerations. The KITS data for this mishap originated from the other KITS pods airborne at the time and not the KITS pod recovered from the MA. When airborne, each KITS pod transmits data on the KITS data link and records all received data from other airborne pods. The master mission file had no gaps during the pertinent time of flight.

The MP and MW executed an instrument trail departure from Runway 23R at 0603L and proceeded to enter Lion airspace, Surge Sector 6. Both pilots accomplished a fence-in and force of gravity (G) awareness exercise in accordance with Air Force flight manuals. The MP achieved approximately 3-4 Gs in the first turn and 7 Gs in the second turn of the G awareness exercise. The MP performed operational checks after the G-awareness exercise and recalled approximately 11,000 lbs. of fuel with no fuel imbalances.

The MP and MW proceeded to set up their first HABFM engagement. The MP made the weather call of "unlimited, clear of clouds, 5,000 feet MSL floor, altimeter 29.51". For this mission, the MP directed a cooperative first merge at 17,000 feet MSL, which allowed for only small variations in altitude between the MP and MW prior to the first merge.

At 0614L the MP and MW achieved a slant range of approximately five nautical miles (NM) and began the engagement with the MP making the radio call "MW, turn in, fights on". The first merge was a left-to-left pass between 17,000 feet and 18,000 feet MSL. The MP and MW both executed a two circle left turning, descending fight with multiple merges, during which the MP took several simulated missile shots at the MW's aircraft.

At approximately 7,000 feet MSL, the MP and MW again merged left-to-left. The MW began to gain an offensive advantage by tightening the turn and bringing the nose of MW's aircraft towards the MA as the MA continued in a left hand turn. As the MW attempted to establish lead pursuit for simulated air-to -air weapons employment, the MW observed the MA execute a level reversal from left to right in a defensive maneuver.

The MP recalled an airspeed of approximately 220 to 230 KIAS and 5,900 feet MSL during this maneuver. The MP used right rudder and pro right yaw differential throttles; left engine in maximum afterburner and right engine in minimum afterburner to reverse the turn direction to the right. The MP assessed the MW would remain offensive and not significantly overshoot and attempted to continue the defensive turn to the right by slicing out of the MW's plane of motion with approximately 200 KIAS and 60 to 90 degrees right angle of bank. In response, the MW executed a reposition by pulling the nose of MW's aircraft away from the MA into a climb above and slightly aft of the MA. KITS data confirmed this portion of the MP and MW's accounts, showing the MP initially turned with 60 to 80 degrees of right bank, then to 110 degrees right bank, pulling for five seconds across (parallel to) the horizon, with 5 to 10 degrees of nose low pitch and 180 KIAS.

The MP recalled continuing a right, descending turn with 900 feet of altitude remaining above the fight floor of 5,000 feet MSL, with right rudder, differential throttles and the stick three quarters aft and centered. However, KITS data, supported by MW testimony, revealed that the MA's lift vector had shifted from tracking across the horizon (60-90 degrees of bank) to nearly straight up in the vertical, eventually settling at 20 degrees of right bank angle. KITS data showed the MA pitched up initially to 40 degrees nose high, and after a pause, to 65 degrees nose high.

The MA's airspeed decreased to 145 KIAS, then to 105 KIAS while altitude increased from approximately 5400 feet MSL to 6300 feet MSL and G forces decreased from +1.2 to +0.5 Gs with maximum angle-of-attack (AOA) of 39 degrees. AOA is the angle between an aircraft wing's mean aerodynamic chord and the relative wind. As the MW rotated the nose down toward the MA, the MA's lift vector was on MW's aircraft with planform increasing.

The MW assessed increasing closure and decreasing range to the MA and executed a second nose high, climbing reposition. The MP did not recall the change in flight path to the vertical, placing the MA lift vector onto the MW, nor pulling the nose of the MA to a high pitch attitude above the horizon and slowing to 105 KIAS. Rather, the MP perceived that the MA's turn rate had decreased (because the nose was not tracking across the horizon at the high AOA) and executed a fist width unload (forward stick) to break the AOA and get the nose tracking faster during the perceived right turn. This action is consistent with executing a turn with rudder at high AOA, however, KITS data and MW testimony showed the MA in a nose high condition and no longer in right hand turn. From this steep pitch attitude, KITS data showed the MA began a right yawing nose drop from 65 degrees nose high and 20 degrees right bank to 65 degrees nose low and 110 degrees right bank. As the MA dropped below the MW's canopy line of sight during this reposition, the MW witnessed the MA's nose had begun to rotate down and to the right.

While actual timing of the forward stick unload executed by the MP could not be determined, KITS data showed the MA entered a region of low to neutral pitch stability for the F-15C (0 to -10 AOA) as the MA's nose fell through the horizon. When the F-15C obtains an excessively nose-high pitch attitude, there is a possibility of a sudden nose-down pitch leading to a negative G excursion. Once the MA's nose was falling, the F-15C's lower pitch stability, assisted by gravity, explains the rapid nose down pitch rate that forced the MA into a negative AOA, negative G condition.

Rudder inputs at negative AOA (between 0 and -0.5 G) result in extreme sideslip angles causing the aircraft to fly sideways, resulting in high cockpit lateral G loads. The KITS data showed the MA at -0.3 Gs during the nose drop. The MP recalled having a full application of right rudder and pro right yaw differential throttles throughout the perceived right turn and during the forward stick unload. When reducing Gs, rudder inputs produce more and more yaw induced sideslip. Due to the stable dihedral effect of the F-15C design, the aerodynamic response to the left sideslip angles (developed as the MA pitched down with right yaw inducing flight control inputs) was a snap roll to the left .

KITS data confirmed a six-second nose drop followed by a negative AOA snap roll to the left. Parameters according to KITS data at the start of the snap roll were 145 KIAS, 65 degrees nose low, 110 degrees of right bank, 26 degrees AOA and -0.3 Gs.

The MP described it as an abrupt, uncommanded nose low maneuver in the opposite (to the left) direction of MP's flight control inputs (to the right) accompanied by departure warning tones. An uncommanded, abrupt flight path change is the definition of a departure from controlled flight. According to the MP and analysis of the KITS data, the MA experienced a departure at this time.

Engineering analysis of the MA's flight trajectory concluded this departure was a negative G departure from controlled flight, with a snap roll to the left that transitioned to an inverted, negative spin. From the initial departure until MP's ejection (approximately 15 seconds), the MA exhibited 30 to 50 degrees per second range of right yaw, 100 degrees per second of left roll, decreasing but oscillating nose down pitch, -20 to -30 degrees AOA and -0.5 to -1.5 Gs.

Multiple simulations were performed to determine possible flight control inputs and/or aircraft malfunctions that could have resulted in a similar nose drop and subsequent departure of the MA. Two scenarios resulted in a similar nose drop, pitch decrease and right yaw as experienced by the MA: (1) a rapid aft stick application that spiked the AOA followed by a forward stick unload with full right rudder, or (2) a significant and sustained forward stick unload with full right rudder. Neither scenario required an induced aircraft malfunction. Engineering analysis confirmed that only two inches of longitudinal stick travel forward of center was required to generate the large spike in negative AOA. Simulator replication with two inches of forward stick and full right rudder exhibited a similar condition of 40 degrees per second right yaw, 10 to 120 degrees per second left roll, decreasing but oscillating nose-down pitch, -20 to -40 degrees AOA, and -0.5 to -2.0 Gs.

The MP recognized the MA's departure from controlled flight and attempted the initial steps of the Out of Control/Departure Recovery Procedure. The rapid MA motion to the left pinned the MP to the right side of the cockpit and forced MP to remove MP's hands from the throttles and flight controls. The MP utilized MP's right hand to push off the right side of the canopy and placed MP's left hand on top of the stick. The MP initially applied right rudder to counter perceived left roll and yaw. The MP did not recall seeing the Spin Recovery Display (SRD), which was consistent with simulator replications and system requirements of higher yaw rates to initiate the display.

At load factors more negative than - 0.5 G, rudder input causes a roll in the opposite direction and is accompanied by high pitch rate and pitch angle changes. This condition is extremely disorienting due to the combined effect of negative and lateral Gs and severe pitch and roll oscillations. The MP did not recognize the negative G condition and did not execute the Flight Manual's associated warning to "counter any negative G with aft stick" to break the negative G condition.

The MP reapplied full or nearly full right rudder to counter MP's perceived roll and yaw to the left. Still under negative G, the commanded right rudder sustained the aerodynamic coupling that generated roll in the opposite direction (to the left). Additionally, MP did not retard the throttles out of AB. The MP did not observe any caution or warning lights or other system malfunction indications.

Without aft stick to counter the negative G condition and split throttles still in AB, the initial steps of the checklist were not fully executed. The application of right rudder was in accordance with the checklist step to "apply rudder smoothly opposite roll/yaw". However, this step in the Flight Manual was written for a positive G auto roll. The checklist does not account for a negative G situation where rudder input causes roll in the opposite direction.

According to MP testimony and KITS data, the MA was below the Flight Manual's Minimum Uncontrolled Ejection Altitude (6,000 feet AGL) in less than two seconds from the moment of departure. Approximately eight seconds later, at 3,500 feet MSL with the ground rush of the low cloud layer, the MP focused on ejecting from the MA. Although unable to complete the Flight Manual recovery procedures, given the initial low altitude at the beginning of the event, F- 15 System Program Office engineers assessed it was unlikely the MA could have recovered before hitting the water.

The MP proceeded to checklist step nine and the associated warning: If spin recovery is not indicated by minimum recommended ejection altitude (6,000 feet AGL), eject.

Due to the forces pinning the MP to the right side of the cockpit, MP's first attempt at ejection was unsuccessful because MP gripped and pulled the emergency manual chute handle. The emergency manual chute handle is for use after ejection to manually force pilot separation from the seat. With the seat in the rails, the emergency manual chute handle is locked and cannot be pulled from its stowed position. This error resulted in further loss of altitude prior to the MP's ejection.

On the second attempt, the MP successfully pulled the ejection handles and initiated ejection at an altitude no lower than 1,100 feet AGL according to acceleration data and timing extrapolated from the ejection seat Digital Recovery Sequencer (DRS). The MP stated having full right rudder application and throttles in a split condition at the time of ejection. The MP was unable to achieve the proper body position for ejection due to lateral and negative G forces generated by the out of control MA.

According to KITS data, the MA started to recover after the MP's ejection exhibiting smaller pitch oscillations, decreasing yaw rate, increasing airspeed and AOA, and G forces increasing to positive. The last KITS data showed the MA in a left rolling motion, -90 degrees nose low pitch, 260 KIAS, and 15 degrees positive AOA.

e. Impact

The MA impacted the Pacific Ocean at 0617L on 11 June 2018, 70 miles south of Kadena AB. The MA broke apart on impact and sank to the ocean floor at a depth of approximately 15,000 feet to 16,000 feet below sea level. The US Navy led an eight-day salvage recovery mission from a US commercial vessel. An underwater remotely operated vehicle submersed to a depth of 15,000 feet to 16,000 feet and recovered, inventoried and photographed minimal MA wreckage.

f. Egress and Aircrew Flight Equipment (AFE)

According to acceleration data and timing extrapolated from the ejection seat DRS, the MP ejected from the MA at 1,100 feet AGL, within the F-15's ejection envelope. This value was estimated based on the ejection seat being airborne for approximately 3.8 seconds prior to impact with the water. The ejection seat deployed the drogue which selected Mode II based on the MA airspeed and altitude. Given the scope of the MP's injuries following MP's rescue from the water, the data analysis demonstrates the MA ejection was complicated when compared to other Mode II ejection scenarios.

The MP's seat was decelerating backwards rather than the optimal orientation of forward. Further, correction performed by the seat to re-orient to a forward facing position at 306 milliseconds was unsuccessful as X-accelerations produced 17 Gs, allowing the seat to maintain a backwards position. Simultaneously, Y -axis accelerations (i.e.- lateral aerodynamic forces), were acting to produce instability of the seat. As a result, the previously mentioned X and Y accelerations resulted in a scenario that is referred to as slow or fouled drogue. In this case, the drogue became slow or fouled secondary to its backwards orientation and the instability of the seat due to the out of control aircraft motion. The lack of seat deceleration reduced the altitude for a safe recovery, with insufficient time for full recovery parachute inflation allowing the MP to impact the water at an unsafe speed.

The MP's post-mishap injuries are consistent with a low altitude ejection and injuries resulting from rapid deceleration when MP impacted the water. These injuries indicate the MP impacted the water feet first at an angle causing damage along the right side of the MP's body, with the decelerating forces being transferred from the feet upwards at the time of impact.

The MP stated the survival equipment performed as designed with the exception of the life raft, which did not inflate when it contacted the water. The MP attempted to manually inflate the life raft and was able to mostly inflate the outer ring. However, due to MP's injuries, the MP was unable to climb out of the water up into the life raft. The MP waited in the water with life preserver units (LPUs) inflated and hung on the side of the partially inflated life raft until the rescue team arrived.

The AN/URT-44 Personnel Locator Beacon (PLB) failed to transmit in this mishap, however, the MW visually found the MP approximately four minutes after ejection. A voltage measurement conducted on the mishap PLB battery indicated depletion of all battery charge. Additional testing showed an excessive leakage current from the battery with the mishap PLB in the OFF position.

All inspections were current for the Aircrew Flight Equipment (AFE). After recovery, the MP's AFE exhibited damage indicative of high loading (cracks/chips on helmet exterior, bent oxygen mask right hand bayonet fitting, bent PLB rocker switch bracket). The chipped and scratched damage regions are consistent with impact from other hard bodies, but there was no material transfer so the impacting bodies could not be determined conclusively. The areas of global damage are consistent with high velocity water impact. The parachute, parachute container, risers and drogue parachute were not recovered. The ejection seat showed damage from asymmetric motion of the aircraft including three of the six rollers missing and two of the remaining rollers with flat spots from sliding or binding instead of rolling .

g. Search and Rescue (SAR)

The MW lost sight of the MA during reposition and continued to climb to avoid any potential mid-air collision. After initially suspecting a loss of radio communications with the MP, the MW called PW10, an airborne F-22A, on the radio and relayed that MW could not find the flight lead. The MW turned back toward the last known location of the MA and used aircraft sensors and visual scan to search for the MA. After descending below the scattered cloud deck, the MW visually acquired the crash site and the MP in the water. The MW called "knock it off" on the airspace common frequency and established a RESCAP over the MP as the initial on-scene commander .

At 0621L, the MW established radio contact with PW2, flying an F-15C, who was at a higher altitude to execute radio relay to the Kadena Supervisor of Flying (SOF) in the Kadena Tower. PW2 passed MP's coordinates to the SOF. The SOF initiated the Downed Aircraft checklist and coordinated by telephone with PW5, 18 WG Command Post, Japanese Air Self Defense Force (JASDF) rescue coordinator at Naha, and the 33rd Rescue Squadron (33 RQS) at Kadena AB. The JASDF rescue coordinator is primary for daytime SAR operations with a UH-60J and U-125 on alert. The 33 RQS is primary for Kadena AB night operations. For this mishap, the JASDF rescue assets scrambled and the 33 RQS, while not on alert, still launched an HH-60.

Multiple pilots performed on-scene commander and radio relay duties throughout the rescue effort. Airborne on-scene commanders established intermittent radio contact with the MP on Guard who reported having a broken leg and hand.

At 0702L, a JASDF UH-60J rescue helicopter took off from Naha airport. A 33 RQS HH-60 took off from Kadena AB at 0713L.

A U-125 (Hawker 750) JASDF SAR aircraft was the first SAR aircraft on scene at 0722L and reported a visual on the MP. At 0731L, U-125 reported UH-60J was approaching for pickup. At 0746L, U-125 reported the MP rescue complete and departed for U.S. Naval Hospital Okinawa Camp Foster. The UH-60J landed at 0819L and the MP was transported to the hospital.

h. Recovery of Remains

Not Applicable.

Chapter 6.3. MAINTENANCE

a. Forms Documentation

The Air Force Technical Order (AFTO) 781 series forms documents maintenance actions, inspections, servicing, configuration, status, and flight activities. Additionally, the Integrated Maintenance Data System (IMDS) is a central database to track maintenance tasks, engines, line replaceable units, scheduled maintenance, time-change requirements, and Time Compliance Technical Order (TCTO).

The 18th Aircraft Maintenance Squadron (18 AMXS) personnel prepared the MA for its

11 June 2018 flight. According to the active AFTO 781 forms, maintenance personnel completed the preflight (PR) inspection, power-on checks, servicing, weapons post-load inspection, installed chaff and flare, loaded communication codes, and completed the aircraft exceptional release for the MA on 10 and 11 June 2018.

A review of the active AFTO 781 forms and IMDS revealed the MA had four open discrepancies. Specifically, the discrepancies documented related to cockpit interior lighting, secure voice system, communication system, and a scheduled inspection for the Identification, Friend or Foe system. Additionally, the MA had 14 open TCTOs, two overdue time-change items (TCI), and no overdue inspections. The two overdue TCIs were part of the F-15C's escape system and were on a temporary shelf/service life extension, which was approved by the Air Force Life Cycle Management Center's Cartridge Actuated Devices/Propellant Actuated Devices (CAD/PAD) Manager. The post-mishap evaluation of the F-15C escape system did not reveal abnormalities with the CAD/PAD sub-system. None of the overdue TCIs, TCTOs, or other open discrepancies affected the aircraft's serviceability.

The active AFTO 781K revealed an erroneous TCI for the Universal Water Activated Release System (UWARS). This UWARS is a sub-assembly for the recovery parachute, which Egress replaced on 12 January 2018. This TCI did not apply to the UWARS installed on the MA, which was serviceable at the time of the mishap.

In the miscellaneous tab of the active AFTO 781 forms, there was a propulsion waiver for the number one engine and a waiver for a displacement block in the wing. The number one engine was allowed to fly with a recurring nuisance fault code, and the MA was allowed to fly without the block. The performance history of the MA's number one engine did not indicate any type of negative trends, and there is no indication either engine malfunctioned at the time of the incident.

Additionally, in the miscellaneous tab of the active AFTO 781 forms, there was an erroneous discrepancy sheet for the radome. On 17 November 14, a defect was identified on the top left six inches aft of the nose cap. According to historical records, the radome was repaired on 2 December 2014. Furthermore, the repaired radome from 2 December 2014 had been replaced several times since then, with the most recent replacement occurring on 19 October 2017 during cannibalization (CANN) rebuild. Historical records did not reveal any discrepancies with the radome installed on the MA. Additionally, pilot simulations ruled out radome malfunctions.

Historical records showed the MA had a history of automatic flight control discrepancies from 14 November 2017 to 28 February 2018, which caused the MA to be impounded five separate times. Specifically, the control augmentation system (CAS) falling offline inflight caused the MA to be impounded four times. Additionally, a missing bearing in the mixing assembly impounded the MA. Maintenance personnel conducted a thorough search of the MA, to include a non-destructive inspection (NDI) of the air inlet ramps, and determined the bearing was not in the MA.

The MA failed two operational check flights (OCF) on 6 December 2017 and 18 December 2017, and failed two functional check flights (FCF) on 14 January 2018 and 14 February 2018. Maintenance personnel worked with engineers to troubleshoot the MA, and on 26 February 2018, identified and corrected an improperly installed rate sensor assembly (RSA), which corrected the CAS discrepancy.

Maintenance personnel cleared the CAS discrepancy, releasing the MA from its fifth impound on 27 February 2018. On 28 February 2018, the MA passed a FCF returning the MA to service.

The MA flew from 28 February 2018 to 6 June 2018 with no further CAS discrepancies, and MP did not recall any CAS malfunctions during the mishap sequence.

b. Inspections

A Preflight (PR) inspection is a physical inspection of the aircraft, and operationally checking certain systems and components to ensure no defects of malfunctions exist. A Basic Postflight (BPO) inspection is a more thorough inspection than the PR inspection. A combined Preflight/Basic Postflight (PR/BPO) inspection is a combination of both the PR and BPO into one inspection. The Pre-launch Inspection (PLI) is an abbreviated PR inspection. The Hourly Postflight (HPO) inspection checks on certain components, areas and systems. Program Depot Maintenance (PDM), is an inspection requiring certain skills, equipment, and facilities. PDM is a thorough inspection of individual areas, systems, and components.

The last PDM inspection occurred at Gimhae, South Korea from 30 December 2016 to 24 May 2017 with 8,267.2 airframe hours. Additionally, the 1,200 HPO inspection was completed in conjunction with the PDM. PDM personnel completed majority of the 1,200 HPO inspections, but due to the configuration of the MA at depot, PDM personnel were not able to complete some of the 1,200 HPO inspections. PDM personnel were not able to accomplish the following inspections: integrated guidance and flight control (system 57000); fire control system; electronic countermeasure system; radio navigation systems; and power plant work cards. 18 AMXS personnel completed these remaining 1,200 HPO inspections and work cards when the MA returned to Kadena AB.

PDM personnel replaced the following items: left and right (L/R) rudder servo cylinder, right aileron servo cylinder, AOA indicator, standby airspeed indicator, standby altimeter, airspeed Mach indicator, L/R AOA transmitter, left stab actuator, L/R 1st air intake ramp assembly, L/R 3rd air intake ramp assembly, L/R diffuser ramp assembly, and L/R vertical stabilizer assemblies.

PDM personnel removed and reinstalled the following items: L/R ailerons, L/R rudders, L/R horizontal stabilizers, L/R flaps, and L/R wings.

Airman First Class (A1C) MXW5 completed the PR/BPO inspection after the MA's previous flight on 6 June 2018 at 1730L. Additionally, Staff Sergeant (SSgt) MXW2 and Senior Airman (SrA) MXW4, completed the PR for the MA on 10 June 2018 at 1730L. All three maintenance personnel testified that there were no discrepancies during any portions of their inspections.

MSgt MXW1 performed an external inspection of the MA, reviewed the aircraft forms, reviewed IMDS to ensure there were no discrepancies preventing the MA from flying, and signed the exceptional release before the MA's sortie.

SrA MXW3 launched out the MA on 11 June 2018, and testified that the launch was normal. SrA MXW3 did not notice any discrepancies during the launch procedure, and verified that the MA passed all flight control checks.

The total airframe hours of the MA for the mishap sortie was 8420.8 hours. The MA had flown 153.6 hours since the last HPO, and PDM. The MA number one engine had 85.5 hours remaining, and the number two engine had 78.2 hours remaining on their 200 engine flight hour inspection.

c. Maintenance Procedures

The MA was in CANN status from 11 September 2017 to 22 October 2017. During this time, the following items were removed. The CAS control panel and Air Inlet Controller (AIC) were removed to facilitate other maintenance (FOM). The RSA and miscellaneous relay panel numbers 1, 4, and 8 were removed to assist in troubleshooting other aircraft. The Pitch Roll Channel Assembly (PRCA) and radome were CANN to other aircraft. Additionally, during the CANN rebuild phase, the PRCA's mode select assembly was replaced for leaking out of limits.

After maintenance personnel installed all removed parts, the following operational checks were performed satisfactorily:

(1) Flap system operational check

(2) Speed brake system operational check

(3) Automatic flight control system operational check

(4) Roll ratio controller and emergency mode procedure of lateral control system operational check

(5) Pitch trim compensator, pitch ratio controller, and emergency mode procedures of longitudinal control system operational check

(6) Aileron rudder interconnect operational check

(7) Maintenance flight control operational check

d. Maintenance Personnel and Supervision

SSgt MXW2, SrA MXW4, and A1C MXW5 were all qualified to perform the PR and PR/BPO inspections on the MA. SrA MXW3 was qualified to perform the aircraft launch procedure. MSgt MXW1 was certified to sign the aircraft exceptional release. Additionally, all maintenance members who signed off any major discrepancies in the active AFTO 781A forms were certified to sign off their respective major discrepancies.

e. Fuel, Hydraulic, Oil, and Oxygen Inspection Analyses

On 11 June 2018, the 18th Logistics Readiness Squadron's Fuels Management Flight (LRS/FMF) personnel obtained fuel samples from refueling trucks 05L-21 and 06L-645, Seido fill stand number three, and Seido tank number four for testing at Air Force Petroleum Office (AFPET) Laboratory, Kadena AB, Japan. All fuel samples met the specification requirements.

Liquid oxygen (LOX) cart LC58 was used to service the MA on 10 June 2018. The LRS/FMF personnel were not able to obtain a sample from LOX cart LC58, because the LOX cart was depleted. This is not unusual since the LOX cart was used to service multiple aircraft that day, but prevented the board from verifying any discrepancy unique to LOX cart LC58. The LRS/FMF personnel were able to obtain a LOX sample from LOX storage tank number 7, which was the last tank to service LOX cart LC58. The sample met TO requirements, and there was no evidence that the servicing equipment was contaminated.

On 12 and 13 June 2018, oil and hydraulic fluid samples were obtained from five hydraulic servicing carts, one hydraulic test stand, and three oil servicing carts. The nine samples were submitted for analysis at the AFPET Laboratory, Warner-Robins Air Force Base (AFB). All oil and hydraulic samples came back consistent with the appropriate type of fluids.

According to the MA active/historical AFTO 781 files and NDI records, there was no indication that either of the two engines had signs of oil contamination, oil consumption, or negative trends.

Since the MA was not recovered, the 18th Wing personnel were prevented from conducting the post-mishap collection and analysis of fluids.

f. Unscheduled Maintenance

The last four flights flown by the MA prior to the mishap sortie occurred on 5 June 2018 and 6 June 2018.

On 5 June 2018, the MA landed code 3 (a major discrepancy, and not a flyable condition) for the Inertial Navigation System (INS), and code 2 (a minor discrepancy, but a flyable condition) for the environmental control system (ECS) and Joint Helmet Mounted Cueing System (JHMCS) discrepancies. The INS and the JHMCS discrepancies were corrected, and the ECS discrepancy was on a three-flight watch, which was cleared on 6 June 2018.

On 6 June 2018, the MA landed code 2 for ECS, radio navigation, electronic countermeasure, and a radio 3 no transmit discrepancy. Maintenance personnel corrected all of the code 2 conditions except for the radio 3 discrepancy. The radio 3 discrepancy was still open in the active aircraft forms, which was a flyable condition.

Captain PW2 flew the MA in a BFM sortie on 6 June 2018, and testified there was an uncommanded roll during the 3,000 feet engagement. Captain PW2 quickly recovered the MA and continued the mission with no further flight control abnormalities. After landing, because the Flight Manual does not classify an auto roll as a departure, Captain PW2 did not report this event to maintenance personnel. On that same day, Major PW8 flew a BFM sortie in the MA after Captain PW2. Major PW8 testified the MA flew normal.

If events such as "uncommanded roll" or "departure from controlled flight" are reported, maintenance personnel utilize TO F-15A-6 and/or 1F-15C-2-27FI-00-1 to troubleshoot. For an uncommanded roll, the aircraft is due an automatic flight control system operational checks, and possibly the directional control system operational test. For a departure situation, the TO states to impound the aircraft, debrief aircrew, complete the aircraft departure checklist, and perform a FCF, and possibly an OCF. There is no history of uncommanded rolls, and the last time the MA had a departure condition documented in the historical records was on 30 July 13.

The following unscheduled maintenance actions were performed between 24 May 2017 to 11 June 2018:

(1)30 August 2017 - Removed and replaced dynamic pressure sensor

(2)2 November 2017 - Removed and replaced the Air Data Computer (ADC)

(3)9 November 2017 - Removed and replaced the ADC

(4)13 November 2017 - Removed and replaced the pitch computer

(5)14 November 2017- Removed and replaced the Inertial Navigation Unit (INU)

(6)16 November 2017 - Removed and replaced the pitch computer

(7)22 November 2017- Removed and replaced the Stick Force Sensor (SFS)

(8)27 November 2017 - Removed and replaced the ADC

(9)30 November 2017 - Removed and replaced the pitch computer

(10)1 December 2017 - Removed and replaced the roll/yaw computer, Accelerometer Sensor Assembly (ASA), and RSA

(11)6 December 2017 - Removed and replaced the ASA, RSA, pitch computer, roll/yaw computer, and AOA probe

(12)7 December 2017 - Removed and replaced the pitch trim controller

(13)14 December 2017 - Removed and replaced the PRCA and mode select assembly

(14)29 December 2017 - Removed and replaced the AIC

(15)10 January 2018 - Removed and replaced the ASA and SFS

(16)7 February 2018 - Removed and replaced the L/R stab actuators

(17)9 February 2018 - Removed and replaced the roll/yaw computer

(18)26 February 2018 - Removed and replaced the RSA

(19)26 March 2018 - Removed and replaced the stick grip

(20)5 June 2018 - Removed and replaced the INU

Chapter 6.4. AIRFRAME, MISSILE, OR SPACE VEHICLE SYSTEMS

a. Structures and Systems

The MA crashed into the Pacific Ocean and the majority of the wreckage remains on the ocean floor inaccessible. No flight control parts or flight control surfaces were retrieved during the MA recovery efforts. The crash survivable memory unit was recovered, but no flight data was recorded because of improper installation.

b. Evaluation and Analysis

There was no engineering analysis completed for the flight control system, because there were no flight control parts recovered.

Without recovery of the MA, the possibility of an aircraft malfunction could not be ruled out with absolute certainty; however, engineering assessments (by the F-15 System Program Office (SPO) and manufacturer's subject matter experts (SME) analyzing the KITS data), MP testimony, and the Pilot Member simulator trials assessed that the MA trajectory can be explained by MP flight control inputs without an aircraft malfunction.

Chapter 6.5. WEATHER

a. Forecast Weather

The weather forecast in Lion Airspace described sky conditions with multiple scattered layers from 2,000 feet to 6,000 feet and few clouds scattered from 7,000 feet to Flight Level (FL) 210 and few clouds from FL250 to FL320 layered. Forecast visibilities were seven miles visibility out of clouds and four miles visibility in clouds. Forecast winds aloft were from south/southwest/west at 5-15 knots from 5,000 feet to 25,000 feet. The sea state was forecast to be 6 to 8 feet with a temperature of 79 degrees Fahrenheit and a drift of west to northwest. There was no forecast hazardous weather to and from or within Lion Airspace. From 30 to 60 miles southwest of the operating area there was a forecast for few (3-15%) thunderstorms with maximum tops of 55,000 feet.

b. Observed Weather

Video data observations from aircraft in the same airspace and at the same time as the mishap showed a broken cirrus layer at approximately 25,000 feet to 27,000 feet MSL and a broken cumulus layer between approximately 1,000 feet and 3,000 feet MSL with visual meteorological conditions (VMC) in between layers. There were additional cirrus layers and cumulus clouds in the distance, more to the south than the north, but not in the localized airspace where fighter engagements were occurring. Visibility was greater than five NM. Post-mishap, the MW reported scattered clouds below 5,000 feet MSL.

c. Space Environment - Not applicable.

d. Operations

Weather Requirements for VMC Operations are to maintain 2,000 feet vertical and one NM horizontal cloud clearance with five NM visibility and a discernible horizon. Based on observed weather at the engagement start altitude of 17,000 feet to 18,000 feet MSL, these requirements were met. At lower altitudes and easterly headings, the ability to discern a clear horizon was obscured.

Chapter 6.6. HUMAN FACTORS ANALYSIS

a. Introduction

A human factor is any environmental factor or psychological factor a human being experiences that contributes to or influences performance during a task.

Department of Defense Human Factors Analysis and Classification System (HFACS), Version 7.0, establishes several potential human factors for assessment during a mishap investigation. The following human factors were relevant to the mishap:

b. PC508 Spatial Disorientation (SD)

This is a factor when an individual fails to correctly sense a position, motion, or attitude of the aircraft/vehicle/vessel or of oneself.

Contributing factors to spatial disorientation in this mishap were: workload (fixation), weather, misperception of the changing environment, and slowed instrument cross check, which led to the perception that the MP was turning parallel to the horizon.

SD occurred: (1) as the nose pitched up, (2) during the nose drop, and (3) during the roll and subsequent inverted, negative G spin of the MA.

In aviation, there are three distinct types of SD. Type I is unrecognized disorientation; the pilot is unaware that anything is wrong, and controls the aircraft in response to the false sensations of attitude and motion. Type II is recognized disorientation; the pilot is aware that something is wrong but may not realize that the source of the problem is SD. Type III is incapacitating disorientation; the pilot knows something is wrong, but the physiological or emotional responses to the disorientation are so great that the pilot is unable to recover the aircraft .

The MP was maneuvering defensively, in a high AOA turn. At some point after the level reversal to the right and attempting to continue in a right descending turn, the MP lost awareness of orientation to the horizon. Specifically the MP testified that MP was in 80-90 degrees right bank (pulling across the horizon) in a parallel orientation when, in fact, the KITS data, MW flight data, and MW testimony confirmed that the MP reoriented to a 65 degrees nose-high climb perpendicular to the horizon. In the events leading up to out of control flight, the MP most likely experienced Type I, unrecognized SD. The MP was "unaware" of high pitch and slow airspeed.

Causes of SD can be attributed to workload and phase of flight such as air-to-air maneuvering associated with Aerial Combat Maneuvering (ACM) and/or BFM. Because of the nature of an air-to-air mission, the pilot's attention is directed outside the aircraft, which increases the potential for channelized attention and slows effective instrument cross check. During the defensive posturing, the pilot was looking back over the shoulder to the belly of the MW. Simultaneously, utilization of a good crosscheck is required to avoid entering an unusual attitude. The MP was on a northeasterly heading at this time, where ragged clouds and sun glare obscured the horizon. It is possible that this environmental factor could result in an incorrect assessment of pitch and roll relative to the horizon.

Prior to the MP departing controlled flight, the MA went 65 degrees nose low with 110 degrees right bank (inverted). The MP had no recollection of the MA shifting from 65 degrees nose high to 65 degrees nose low, but only sensed the nose stopped tracking. The MP's lack of awareness that the MA was reversing from nose high to nose low was likely due to the observed weather conditions stated above, coupled with the MP's focus on maintaining sight with the MW.

Furthermore, once in a negative G situation, the MP thought the MA was in an upright position and was unable to assess the negative AOA and negative G. The severe pitch and roll oscillations combined with negative and lateral Gs likely contributed to the SD.

As the above examples illustrate, unrecognized SD had a significant impact on the MP, which contributed to the out of control flight and ejection from the MA. Some of the following sections will discuss the additional factors that contributed to the MP's SD: misperception of the changing environment, fixation, wrong choice of action, and external force or object impeded an individual's movement.

c. PC507 Misperception of the Changing Environment

This is a factor when an individual misperceives or misjudges altitude, separation, speed, closure, rate, and aircraft location within the performance envelope or other operational conditions. Misperception of an object, threat, or situation results in degraded sensory inputs. When present in an aircrew member, this can negatively affect situational awareness conditions.

Situational awareness (SA) is defined as an aircrew member's continuous perception of self and aircraft in relation to the dynamic environment of flight, threats, and mission, and the ability to forecast then execute tasks based on that perception.

While the MP did not recall any forecast weather related issues, the observed weather was significant for cloud cover both above and below the fight, in addition to the sun being displayed low on the horizon. Added to this, the MP was flying in a vertical fight with reference to the other aircraft (i.e. the MW). These conditions can result in disorientation and could have contributed to the MP's misperception of the MA's position relative to the horizon.

The following sequence of events illustrate how the misperception of the changing environment by the MP lead to loss of SA of the MA's position relative to the horizon (i.e., the ground or in this case the ocean) along with the MA's energy state, pitch angle, and attitude.

The MP did not recall the MA's nose high position and perceived the MA was in a steep right hand turn. However, the MP had oriented and maintained a lift vector on the MW resulting in a nose high attitude relative to the horizon and a subsequent decrease in airspeed. Further, the MP misperceived that the MA had decreased tracking during a right hand turn due to excessive AOA when KITS data showed that the MA was nose high for approximately 15 seconds. At this point, the MA likely either stalled due to an excessive AOA spike as demonstrated in the simulator or the MP excessively unloaded and over a span of six seconds, the nose dropped from 65 degrees nose high to 65 degrees nose low.

Then at some point during this nose high to nose low transition, the MP pushed the stick forward with full right rudder still engaged resulting in the snaproll. Abrupt forward stick inputs combined with a high roll or yaw rate may induce an auto roll/spin or cause a departure. The forward stick inputs when applied in this negative G situation caused the out of control flight. If the MP had recognized the negative G scenario and acted to use aft stick, this would have aided in recovery of the MA before it transitioned to a sustained departure situation.

d. PC102 Fixation

This occurs when the individual is focusing all conscious attention on a limited number of environmental cues to the exclusion of others.

During the sequence of events, the MP performed the necessary defensive BFM to remain engaged with the MW. This type of maneuvering requires the defensive player (i.e., the MP) to be looking outside of the aircraft over the shoulder through the top of the canopy. The MP was most likely channelized or fixated on the MW aircraft position, attitude, angle-off, and closure. The combination of the cloud cover both above and below the fight, in addition to the sun located low on the horizon presented conditions where visual illusions in regards to the horizon were most likely to occur resulting in the loss of SA and misperception of the MA's positional relationship to the horizon.

e. AE206 Wrong Choice of Action During Operation

This a factor when the individual, through faulty logic or erroneous expectations, selects the wrong course of action.

When there is a misperception of the current situation, the pilot cannot accurately predict the future status, which negatively affects decisions and subsequent actions. This misperception results in wrong choice of action. In the case of the MP, these wrong choices of action were the following: (1) unload of the stick with high AOA and full rudder, (2) not using aft stick to counter the negative Gs, and (3) maintaining full right rudder, which under negative G was a pro-left rolling input. Where the first action led to the MA departure, the second and third actions sustained the MA departure condition (inverted, negative G spin) with negative AOA and negative Gs.

In the events leading up to the first wrong choice of action, the MP stated the MA was tracking relatively parallel across the horizon, when KITS data showed the MA had transitioned to flying well above and perpendicular to the horizon. The MP did not recall this change in flight path.

Further, the MP did not recall executing a tree (vertical) maneuver when engaged in defensive BFM with the MW. The MP misperceived the situation compared with the MW testimony and KITS data. Since the MP was unaware of the MA's high pitch attitude and resultant low airspeed, the MP failed to recognize the nose was falling down and to the right.

The MP thought excessive AOA was causing the MA to not track across the horizon. This is consistent with the MP being unaware of the MA's high pitch attitude and decreasing airspeed. The MP assessed that by unloading pressure off the stick, it would help the MA's tracking. While the exact moment the MP initiated the unload cannot be determined, once the MA's nose started falling it continued over a span of six seconds dropping from 65 degrees nose high to 65 degrees nose low.

At some point during this nose high to nose low transition, the MP executed the second wrong choice of action when continuing to apply full right rudder resulting in the snaproll. The MP recognized the MA's departure and executed the first two steps of the Out of Control/Departure Recovery Procedure; Smoothly Neutralize and Release Controls and Apply Rudder Smoothly and Opposite Roll/Yaw.

The MP recalled feeling light in the seat, a sensation of "eyeballs out," with a more significant force that pushed the MP to the right side of the cockpit. The MP sensed the forces as mostly yaw due to a perceived spin and was unaware of the negative G situation. When the MP reapplied right rudder in the negative G condition it sustained the right yaw and left roll coupling of the MA rather than countering it. The MP, likely due to disorientation caused by the combined negative and lateral G forces, did not recognize the negative G condition and was unable to execute the last sentence of Step 2's warning to "counter any negative G with aft stick.

Wrong choice of action is affected by numerous factors. One concept in particular, temporal or time distortion is worthy of discussion in this section as it refers to the MP. Temporal or time distortion occurs when our attentional capacities are highly taxed. Any high stress situation has the potential to create an environment that is conducive to temporal distortion. Due to the low ejection at the time of departure, the MP stated the time available to assess the situation was approximately three seconds.

Unlike the other HFACs, temporal/time distortion occurred at a point in the sequence of events where the MP reacted in a "fight or flight" response. In this case, fight would be defined as continuing to troubleshoot the issues with the MA and attempts to recover the aircraft through identification of the correct checklist with the immediate threat, given the low altitude, being both loss of life and the aircraft. Flight would be defined as ejecting from the aircraft because of the survival instinct.

The MP was aware that the altitude at the time of aircraft departure was below the minimum uncontrolled ejection altitude of 6,000 feet AGL. After application of right rudder failed to recover the aircraft to controlled flight, the MP focused on getting out of the aircraft. Analysis of the KITS altitude data reveals that approximately 9-10 seconds expired while the MP assessed the situation and executed the out-of-control/departure recovery checklist prior to deciding to eject from the MA. The MP recalled the challenges faced during this compressed time interval including both lateral and negative G forces pinning the MP to the right of the cockpit.

KITS data showed the MP had two seconds after the MA departure before falling below the 6,000 feet AGL ejection minimum. The additional eight seconds spent fighting the MA (attempting to recover, giving it "the old college try,") likely contributed to an extremely low altitude ejection (1,100 feet AGL). The ejection was further delayed by an unsuccessful first attempt as the MP's right hand gripped and pulled the emergency manual chute handle. Furthermore, as the negative G situation progressed, the "ground rush" of the cloud deck at 1,000 feet to 3,000 feet MSL and seeing 3,000 feet to 3,500 feet MSL on the altimeter, the MP decided to eject.

f. PE108 External Force or Object Impeded an Individual's Movement

This is a factor when acceleration forces greater than one second cause injury or prevent/interfere with the performance of normal duties.

Negative G flight characteristics are extremely disorienting. As described above, the MP was lifted out of the seat and pinned to the right side of the cockpit due to lateral and negative G forces. Based on KITS data, the MP experienced negative longitudinal G forces ranging from -0.5 to -1.5 Gs for approximately 15 seconds. This contributed to the MPs inability to fly the MA with hands on stick and throttles as the MP had to brace with the right hand against the canopy and controlled the MA with left hand, which is not normal or expected operations.

These gravitational forces delayed the ejection by impeding the MP's ability to actuate the handles correctly. Specifically, during the first ejection attempt the MP inadvertently grabbed the emergency manual chute handle with the right hand and applied insufficient force with the left hand to activate the ejection seat. Recognizing the error, the MP visually confirmed hands on the correct handles and ejected successfully by pulling both ejection handles.

g. OP004 Organizational (Formal) Training is Inadequate or Unavailable

This is a factor when initial training programs, upgrade programs, transition programs or other training conducted outside the local unit is inadequate or unavailable.

The MP experienced a negative G departure from controlled flight with a snap roll entry to the left that transitioned to an inverted, negative G spin condition. During F-15C initial qualification at the formal training unit (FTU), negative G scenarios are taught academically and briefed on every BFM sortie, but there is no practical hands-on simulator training specifically for negative G auto rolls or inverted spins. Positive G auto rolls/spins are taught but in only one simulator training flight in the initial qualification training (IQT) course. A review of MP's training records at the FTU revealed auto rolls/spins were only taught hands-on during one simulator training sortie each.

Through interviews with instructor pilots (IPs)/leadership from the 44 FS at Kadena AB, the board learned there is no requirement nor tracking mechanism during continuation training to ensure F-15 pilots are proficient to recover from a negative G auto roll or inverted, negative G spin.

Specifically, negative G spins and negative G auto rolls are not tracked as individual required maneuvers in EP or tactical simulators. Pilots testified they did not remember doing a negative G out of control departures recovery. Additionally, actual accomplishments are not tracked in EP simulators, and monthly SEPT or BFM sortie briefs typically only cover positive G auto roll/spin situations and recoveries. Pilots also testified the simulator is a poor replicator of the forces experienced.

In this scenario the MP did not recognize the negative G aspect of the departure and therefore applied right rudder to counter the auto roll rather than left rudder (in the direction of the roll) as recommended in the Flight Manual to speed the recovery. Additionally, the MP did not counter the negative G with aft stick as recommended by the Flight Manual.

h. OP003 Provided Inadequate Procedural Guidance or Publications

This is a factor when written direction, checklists, graphic depictions, tables, charts or other published guidance is inadequate, misleading or inappropriate.

Negative G flight characteristics, negative G auto rolls/spins, and recovery of the aircraft in negative G situations are included in the T.O. series for the F-15C. However, the steps in the Out of Control/Departure Recovery checklist are written for a positive G auto roll or spin. In the handheld checklist, only a single warning mentions countering negative G with aft stick. There is no mention of negative G auto roll recovery considerations in the checklist.

Chapter 6.7. STATEMENT OF OPINION

On 11 June 2018, the Mishap Pilot (MP) was flying the Mishap Aircraft (MA), an F-15C, Tail Number 84-0008, assigned to the 44th Fighter Squadron (44 FS), 18th Wing (18 WG), Kadena Air Base (AB), Japan. The MP was flying as lead of a two-ship formation during a dissimilar basic fighter maneuver (BFM) sortie with an F-22A, assigned to the 525th Fighter Squadron, 3rd Wing (3 WG), Joint Base Elmendorf-Richardson, Alaska. While maneuvering defensively in relationship to the Mishap Wingman (MW), at approximately 5,400 feet mean sea level (MSL) and 180 knots indicated airspeed (KIAS), the MP initiated a vertical maneuver climbing to 65 degrees nose high, 20 degrees of right bank, 39 degrees Angle-of-Attack (AOA), 1.2 Gs, and to approximately 6,300 feet MSL and 105 KIAS, before a significant nose drop occurred. The MP perceived the MA was not tracking as desired and initiated an unload of approximately one fist-width's forward stick with full right rudder. The nose pitched down and to the right to 65 degrees nose low, 110 degrees of right bank, -26 degrees AOA and G forces decreasing from 1.2 to -0.3 Gs. With right rudder still commanded, the MA experienced a negative G departure from controlled flight with a snap roll entry to the left that transitioned into an inverted, negative G spin. The MP received no indications of hydraulic, electrical, fuel, engine, structural, or flight control system malfunctions. The MP immediately experienced significant longitudinal and lateral G forces, high roll rates and pitch oscillations, and was below the F-15C Flight Manual's Uncontrolled Minimum Ejection Altitude of 6,000 feet above ground level. Unable to recover the MA, the MP ejected 15 seconds after the departure from controlled flight at approximately 1,100 feet MSL and sustained serious injuries. At approximately 0617 hours local time, 14 minutes after takeoff, the MA crashed into the Pacific Ocean approximately 70 miles south of Kadena AB. The MA broke apart upon impact with a loss valued at $42,360,014.00. There were no fatalities or damage to civilian property.

Chapter 7. T6 Randolph 2018.09.18

T-6A, T/N 05-6209

JOINT BASE SAN ANTONIO (JBSA)-RANDOLPH, TEXAS

LOCATION: 4.8 MILES NW OF JBSA-RANDOLPH, TEXAS

DATE OF ACCIDENT: 18 SEPTEMBER 2018

On 18 September 2018, at 15:40:41 hours, local (L) time, a T-6A Texan II, tail number 05-6209, crashed 4.8 miles northwest of JBSA-Randolph, TX, completely destroying the aircraft. The mishap aircrew (MC) consisted of a mishap instructor pilot (MIP), occupying the front seat, who was supervising the mishap pilot (MP). The MP was conducting an instructor qualification sortie in the Pilot Instructor Training (PIT) course from the rear seat. The MC successfully ejected and sustained minor injuries. The MC and mishap aircraft (MA) were assigned to the 559th Flying Training Squadron, 12th Flying Training Wing (FTW), JBSA-Randolph, TX. During the mishap sortie (MS), the MA crashed while returning to base for local take-off and landing practice. The destroyed aircraft is valued at approximately $5.7 million with minimal damage to civilian property and no casualties.

While being vectored for the approach to runway 15R at Randolph Air Force Base (AFB), at approximately 15:35:00L, the MC noticed the high fuel flow reading, and subsequently decided to continue the approach to a full stop. Slightly over four minutes later, at 15:39:16L, while slowing and configuring to land, the MA's engine failed. At the time of the engine failure, the MA was below the energy profile required to glide to a suitable landing surface. The MIP transmitted the MC's intent to eject over the radio and they did so seconds later.

The Accident Investigation Board (AIB) President, by a preponderance of evidence, determined the cause of the mishap to be a fuel transfer tube locking plate that was improperly installed during the contracted 4500 hour engine overhaul. This resulted in engine failure where the aircraft was not in a position to land safely.

Chapter 7.1. ACCIDENT SUMMARY

On 18 September 2018, at 15:40:41 hours, local (L) time, a T-6A Texan II, tail number 05-6209, crashed 4.8 miles northwest of JBSA-Randolph, TX, completely destroying the aircraft. The mishap aircrew (MC) consisted of a mishap instructor pilot (MIP), occupying the front seat, who was supervising the mishap pilot (MP). The MP was conducting an instructor qualification sortie in the Pilot Instructor Training (PIT) course from the rear seat. The MC and mishap aircraft (MA) were assigned to the 559th Flying Training Squadron (FTS), 12th Flying Training Wing (FTW), JBSA-Randolph, TX. While on approach, the MC recognized abnormally high fuel flow readings and elected to conduct a full stop landing to Randolph Air Force Base. Minutes later, while slowing to configure for landing, the MA experienced engine failure and crashed.

The MC ejected safely from the aircraft sustaining minor injuries. The destroyed aircraft is valued at approximately $5.7 million with no loss of civilian property or casualties.

Chapter 7.2. SEQUENCE OF EVENTS

a. Pre-Mission Maintenance

On 11 December 2017, Standard Aero Ltd overhauled the Mishap Engine (ME), serial number PWV-RA0325. During the overhaul, the fuel manifold set and the fuel flow divider unit were removed, overhauled separately, and reinstalled. The ME was stored until 7 August 2018 when it was returned to, and accepted by, the Contractor Operated and Maintained Base Supply (COMBS) facility at JBSA-Randolph, TX. On 8 August 2018, COMBS personnel completed and signed off the installation of the Quick Engine Change (QEC) kit.

On 20 July 2018, the Maintenance Support Unit (MSU) inducted the Mishap Aircraft (MA) to accomplish a 150 Hourly Post Flight Inspection (HPO). During this inspection, on 24 July 2018, mechanics discovered the lower right oil filler cap stud was damaged on the installed engine, serial number PWV-RA0161, rendering it unserviceable. Work cards A through 6-004 were accomplished prior to identifying damage on that engine. It was subsequently removed from the MA.

On 13 August 2018, MSU mechanics accepted the ME and installed into the MA. Work cards 6-005 through 6-013 were accomplished on the ME and MA. Remaining maintenance and performance runs were conducted on the MA between 13 and 21 August 2018.

On 30 August 2018, a Functional Check Flight (FCF) was accomplished with no discrepancies noted, thereby releasing the aircraft back to flying status. The MA then flew 17 sorties between 30 August and 17 September 2018.

b. Mission

The 559 FTS scheduled and authorized the MC's mission sequence. On Tuesday, 18 September 2018, the MP was to fly a day, single-ship, front-cockpit sortie as part of the Pilot Instructor Training (PIT) program. The MIP, scheduled as the Instructor Pilot (IP) and pilot in command of the mission, was tasked with conducting the required training for the MP on the sortie. The MS was the fourth scheduled mission in the MP's syllabus. The MP previously completed three sorties in the PIT syllabus. The MP had also flown two "incomplete" sorties, in the preceding 30 days, which did not count towards his syllabus progression. The planned profile for the sortie included a departure to the Military Operating Area (MOA) for basic air work followed by an approach into Kelly Field, TX and finished with a visual flight rules (VFR) recovery to Randolph Air Force Base (AFB) for patterns.

c. Planning

On 18 September 2018, the MIP reported for work at 08:30L followed by the MP at 12:30L. The MIP met with the MP at approximately 13:40L to brief the sortie in accordance with Air Force Instruction (AFI) 11-2T-6v3, Air Force Manual (AFMAN) 11-248, and Squadron Standards, along with Notices to Airmen (NOTAMs), forecast weather, and planned flying events. Per normal procedures, no squadron supervisory personnel attended the brief. The MP also completed an Operational Risk Management (ORM) assessment. The ORM form is a checklist of risk factors, designed to codify all identifiable risks associated with the planned mission. Each factor, such as weather, briefing time, or lack of sleep, has an associated point value. The MP compiled the total of all identified risks. The following scale quantifies the sortie risk: Low (0-5 points), Moderate (6-12 points), High (13-15 points), Severe (16+ points). The missions quantifiable risk assessment was 6 points, equating to a planned moderate-risk mission. Both the MIP and MP checked the NOTAMs and weather. The MP planned the sortie to conduct a takeoff and departure towards the Tweet MOA west of the field. Once in the MOA the MP planned to accomplish a unit -of-gravity (G) exercise, traffic-pattern stalls, power-on stalls, slow-flight, aerobatics, and multiple out of controlled flight (OCF) recoveries. Following the maneuvers in the MOA, the MP planned to fly an instrument landing system (ILS) approach into Kelly Field, TX. Finally, the plan was then to return to Randolph AFB under VFR and conduct traffic-pattern training.

d. Preflight

At approximately 1405L, the MIP and MP travelled to Aircrew Flight Equipment (AFE) to don their flight gear. At approximately 1410L, the MIP and MP travelled from AFE to the T-6 Operations Supervisor's desk for the step-brief and aircraft assignment. The step-brief included an updated weather forecast, NOTAMs, and an airfield status update. The T-6 Operations Supervisor, SWIT 42, reviewed the MC's ORM sheet and approved the mission's risk assessment. At approximately 1415L, the MIP and MP walked to the MA. The MIP and MP reviewed the forms, followed by the MIP completing the walk-around inspection of the MA. Neither the MIP nor MP discovered any abnormalities prior to operating the MA. The MIP noted no abnormalities during engine start or preflight operations.

e. Summary of Accident

The MIP taxied out of parking at 14:36:30L and then to the end of runway (EOR) area. While in the EOR, the MIP conducted the over-speed governor check along with all other items listed in the checklist. Neither the MIP nor MP noted any anomalies. Take-off occurred at 14:43:20L.

The MA reached the MOA at approximately 14:48:00L and remained in the MOA until requesting vectors for the approach at Kelly Field at 15:28:40L. After the MC made the approach request, the Houston Air Traffic Control Center informed them that it would be roughly a 15-minute wait before it could clear them for the approach due to other air traffic. The MC opted to forego the approach at Kelly Field and return directly to Randolph AFB for the ILS and traffic-pattern work.

At approximately 15:35:30L, while being vectored for the approach, the MP noticed a slight and momentary, un-commanded increase in torque. This drew the MPs attention to the fuel flow display, which indicated a roughly 735 pounds per hour (pph) flow. Parametric data indicates that the torque anomaly occurred concurrently with displacement of the fuel transfer tubes and excessive fuel flow rates. The MP brought the increased fuel flow to the attention of the MIP. The MP did not communicate, nor was the MIP ever made aware of, the torque anomaly. The MIP acknowledged the fuel flow anomaly but did not take control of the aircraft to analyze further until 30 seconds later at roughly 15:36:30L.

At 15:37:30L, San Antonio Approach instructed the MC to contact the JBSA-Randolph Tower. At approximately the same time, the MIP returned control of the MA to the MP in order to complete the approach. The MC, upon confirming the abnormal fuel flow indications, elected to make this landing a full-stop and forego any further traffic-pattern work.The MP intercepted the final-approach course and lined up with runway 15R at 15:37:55L.

Approximately a minute later, at 15:38:36L, the MP reports having reached the final-approach -fix (FAF) configured for landing. This, however, was not the case, as the MP had not yet configured the aircraft for landing. The aircraft was 10 knots above maximum configuration speed. The MIP took control of the MA to slow down and properly configure the aircraft for the approach and landing.

The MIP initiated a descent from the FAF at 15:39:06L and was cleared to land 6 seconds later.

At 15:39:15L, the MIP moved the power control lever (PCL) to the idle position to expedite slowing the aircraft below 150 knots in order to lower the gear and flaps. Upon selecting idle, engine operation immediately fell to a sub-idle state that was no longer capable of producing useable thrust.

15 seconds later, the MIP lowered the gear and flaps for the approach. Upon pushing up the PCL to maintain airspeed following aircraft configuration, the MC recognized the engine failure. The MIP pushes the PCL back and forth several times in an attempt to confirm loss of useable thrust.

20 seconds after the MIP lowered the gear and flaps, both the gear and flap handles are raised to the UP positon.

At 15:40:02L, the MIP moved the PCL to the cut -off position. Parametric data shows the engine shut down and the propeller feathered.

At 15:40:18L, the MIP makes the radio transmission: "Fangs 99, ejecting on short final".

Three seconds later, the MIP makes a slight left turn to align the aircraft with the impact field and avoid a school directly ahead.

At 15:40:30L, the MIP initiates the ejection. The MC ejected successfully. At the time of ejection, the MA was wings level, 5.5 nautical miles from the runway surface, 700' above ground level (AGL), 105 knots, and descending at 400 feet per minute.

f. Impact

The MA crashed 4.8 miles north-northwest of Randolph AFB, TX at N 29.5997436, W 98.3290342, at 750 feet MSL. The crash site was a flat, lightly corrugated field with grass coverage. The MA impacted the ground in an estimated 20 degree nose low, 10 degree left bank attitude, at 140 knots. Aircraft ground scarring was consistent with the aircraft hitting at a shallow angle and tumbling.

The majority of the wreckage was located within a few hundred feet of the where the fuselage came to rest. The wings and empennage separated from the fuselage shortly after impact, stopping about 40 yards northwest of the fuselage section.

The MC landed in a small grove of trees about 3,500 feet northwest of the impact site.

g. Egress and Aircrew Flight Equipment

(1) Egress

The MC ejected successfully, sustaining minor injuries. Both ejection seats were recovered about 2,000 feet northwest of the impact site in an adjacent field.

(2) AFE

All personal and survival equipment had current inspections and worked as designed.

h. Search and Rescue (SAR)

(1) Air SAR

The ejections radio call was garbled, causing slight confusion in the control tower. The tower requested another T-6 in the pattern proceed to the straight-in ground track to see if they could see a crash site. The T-6 reported that they did not see anything and were subsequently directed to land.

(2) Ground SAR

At approximately 15:47:00L, the 902nd CES/CEF, SWIT 18, was notified of an inflight emergency heading to runway 15R. The tower relayed to SWIT 18 that the aircraft might have gone down a few miles short of the field, but it did not see any smoke. A few minutes later, the tower received word that the MC had ejected successfully and was located near 17253 Nacogdoches Road. The fire department responded with four fire/emergency response vehicles. One of the vehicles experienced mechanical issues enroute and returned to base. The remaining three vehicles arrived on scene at roughly 16:10:00L, following a roughly 20 minute drive from base. The fire department ensured the MA was safe to approach and completed all necessary checklists. The MC was transported to the JBSA-Randolph clinic and subsequently discharged with minor injuries. All fire department members were clear of the scene at 20:05:00L.

(3) Recovery of Remains

Not applicable.

Chapter 7.3. MAINTENANCE

a. Forms Documentation

(1) Summary

The AIB presumes the ME was sent to Standard Aero Ltd. for a scheduled 4500 hour major overhaul in October 2017. The evidence does not have an exact date, but it does reference maintenance actions throughout the month of October 2017. During that overhaul, the Fuel Manifold Set and the Fuel Flow Divider Unit were removed, overhauled separately and reinstalled. On 7 August 2018, the ME was then shipped to COMBS at JBSA-Randolph, TX. On 20 July 2018, the MA was inducted for a scheduled 150 HPO inspection. During this inspection, on 24 July 2018, mechanics discovered the lower right oil filler cap stud was damaged on engine PWV-RA0161 rendering it unserviceable. This drove an unscheduled engine change that occurred on 13 August 2018.

After the ME was installed on the MA, the MA flew 17 sorties for a total of 31.9 hours. On the mishap day, prior to the MS, the MA flew two training sorties for a total 3.1 hours. Active Air Force Technical Order (AFTO) Forms 781A series and historical record AFTO Forms 781A for the period of 90 days prior to the MS did not indicate any MA or ME anomalies.

(2) Major Maintenance

Major maintenance is any maintenance action that requires the aircraft be removed from flying status to be checked for potential failures, to have major components (such as flight control surfaces, engines, etc.) removed, or to accomplish special inspections.

In October 2017, the ME was sent to Standard Aero Ltd. for a scheduled 4500 hour major overhaul. During that overhaul, the Fuel Manifold Set and the Fuel Flow Divider Unit were removed, overhauled separately and reinstalled. It was returned to COMBS at JBSA-Randolph, TX on 7 August 2018. COMBS received the ME, configured it with the required QEC Kit and then issued it to the MSU. The QEC Kit change does not involve maintenance on the fuel manifold hardware. COMBS performed no other maintenance or inspections on the ME.

On 20 July 2018, the MA was inducted in for a scheduled 150 HPO inspection. The engine portion of the Technical Order (T.O.) 1T-6A-6WC-1, 150 HPO inspection work cards A through 6-004 were accomplished and signed off and remained signed off in the AFTO 781A forms for engine SN: PWV-RA0161. Work card 6-004, item 10 addresses the inspection of fuel nozzles and fuel flow divider for leaks and security. The locking plates are an integral part of the fuel manifold system because they secure the fuel transfer tubes and manifold adapter, which houses the fuel nozzles. During the HPO inspection, engine serial number PWV-RA0161 was removed because it was found to be unserviceable. This resulted in an unscheduled engine change that occurred on 13 August 2018. The MSU completed only the remaining work cards on the MA and ME. These work cards do not address the fuel manifold or associated components. MSU did not accomplish any additional maintenance on the fuel manifold or associated components.

(3) Recurring Maintenance

In accordance with (IAW) T.O 00-20-1_AETCSUP, Paragraph 2.2.1, recurring maintenance occurs when issues reappear after two to four flown sorties. AFTO 781 series forms showed no evidence of or requirement for recurring maintenance on the ME or the MA associated with the fuel system IAW the definition in AFI 21-101.

(4) Unscheduled Maintenance

T.O 00-20-1_AETCSUP, Paragraph 2.2.3 describes unscheduled maintenance as any maintenance action that is not the result of a scheduled inspection. On 20 July 2018, the MA was inducted in for a scheduled 150 HPO inspection. That inspection resulted in an unscheduled engine change due to discrepancies identified with engine serial number PWV-RA0161. MSU mechanics replaced it with the ME on 13 August 2018. The MA had no other unscheduled maintenance accomplished that contributed to the mishap. The ME had no other unscheduled maintenance after installation.

(5) AFTO Form 781A

The AFTO forms are used to document maintenance actions taken on an aircraft. The MA active AFTO Form 781A had a start date of 17 August 2018, with no grounding discrepancies at the time of the mishap. AFTO Forms 781A historical hard copy documents identify the accomplishment of the 150 HPO inspection and all associated maintenance tasks to include the unscheduled engine change. There is no record of maintenance on the ME fuel manifold section of the engine in the AFTO 781A forms.

(6) Pre-Flight Operational Checks

AFTO Form 781H provides the current flight condition of the aircraft, current flight hours, and current fuel status. In accordance with T.O. 00-20-1, when a period of 72-hours has elapsed with no maintenance or flight activity, an aircraft requires an updated 72-hour combined pre-flight/basic post-flight (BPO/PR) inspection before it is released for flight. There is also a combined BPO/PR daily inspection requirement that should be accomplished after the last flight of a flying period. This inspection consists of checking the aircraft to determine if it is suitable for another flight by performing visual examination of certain components, areas, or systems to ensure no defects exist which would be detrimental to flight. The MA AFTO Forms 781H dated 17 August 2018, indicate the appropriate maintenance personnel completed a combined basic BPO/PR inspection on 17 August 2018. The BPO/PR does not inspect the fuel manifold section of the engine.

b. Inspections

(1) MISHAP AIRCRAFT

On 17 September 2018 at 18:03L, the aircraft maintainer/crew chief performed a combined BPO/PR inspection of the MA at the end of the flying day. On 18 September 2018, the expeditor signed the Exceptional Release (ER) verifying the 72-hour inspection was completed and that the MA was airworthy. The ER serves as a certification that the expeditor reviewed all active forms, acknowledging that the aircraft inspections are complete, and that the aircraft was safe for flight IAW T.O 00-20-1_AETCSUP, paragraph 5.13.1.2.7.3. Two sorties were flown with accompanying thruflight inspections accomplished prior to the MS with no discrepancies noted. The thruflight turnaround inspection requirements will be accomplished in lieu of a combined BPO/PR daily inspection where multiple missions are flown during the same flying period IAW 1T-6ABD-6WC-1, card i-002 and i-003 (Inspection Definitions). The inspection is a visual examination of the aircraft to discover defects or malfunctions, which, if not corrected, would impair safety of flight. Maintenance Records show all inspections required prior to the MS were performed IAW T.O. guidance and with the exception of non-contributing AFTO 781J inconsistencies, no anomalies/discrepancies were observed. The thruflight does not inspect the fuel manifold section of the engine.

(2) MISHAP ENGINE

The ME was sent to Standard Aero Ltd for a scheduled 4500 hour major overhaul in October 2017. On 7 August 2018, Standard Aero Ltd, shipped the ME to COMBS at JBSA-Randolph TX.COMBS received the ME on 8 August 2018 and configured it with the required Quick Engine Change (QEC) Kit. The MSU installed it in the MA on 13 August 2018. 17 sorties totaling 27.8 hours were flown prior to MS.

(a) Maintenance Procedures:

Maintenance Records show all maintenance procedures the night prior and the day of the MS were performed IAW T.O. guidance and only non-contributory anomalies were found.

(b) Maintenance Personnel and Supervision:

Training records of the involved maintenance members showed they were qualified to complete their assigned tasks.

(c) Fuel, Hydraulic and oil inspection Analyses:

Prior to the MS, the MA was serviced with fuel twice on 18 September 2018 and received the appropriate amount of fuel after the previous missions. The ME did not require oil servicing prior to the MS.

Chapter 7.4. AIRFRAME, MISSILE, OR SPACE VEHICLE SYSTEMS

Structure and System

(1) Engine

The MA was equipped with one PT6A-68 Turbo Prop Engine. On 13 August 2018, ME S/N: PWV-RA0325 was installed on the MA. Following the installation of the ME, the MA was flown 17 sorties, totaling 31.9 hours. In addition, on the day of the mishap, 18 September 2018, the MA was flown two times with no Pilot Discrepancy Reports (PDR) prior to the mishap.

The ME was recovered and analyzed by Pratt & Whitney Canada, which provided a complete report of the engine. The report stated that circumferential marks on the compressor turbine disc/blades and the bending of all the propeller blades indicate that the engine was rotating slowly at impact.

Significant ME disassembly observations were made by the Pratt & Whitney Canada technicians. "The engine was removed from the shipping container and placed in a stand. The fuel management unit (FMU) was removed from the fuel pump. An adapter with a fitting to apply shop air to the fuel line was installed on the fuel line at the FMU fitting. One hundred PSI of shop air was applied into the fuel line. A leak was noted on one primary fuel transfer tube between the No. 9 & 10 fuel nozzles. The transfer tube bracket [fuel transfer tube locking plate] on the No. 9 fuel nozzle was out of position. The bracket was removed and the primary fuel transfer tube was found to be out of its respective position between the two fuel nozzles. The secondary transfer tube also appears to be partially displaced toward the No. 9 fuel nozzle. During the attempt to re-engage the transfer tube into the No. 10 nozzle the packing was damaged. The packing was changed and tube was re-installed. Air pressure was applied an audible noise was heard indicating the air was being transferred through the fuel nozzles and no external leaks were detected. The No. 9 fuel nozzle transfer tube retention bracket was bent adjacent to the retention points". The lead Pratt & Whitney Canada investigator, WIT 9, testified that the fuel transfer tube locking plate displacement could not have occurred during ground impact.

(2) Fuel, Oil, and Hydraulic

The MA received the appropriate amount of fuel after the previous mission. Additionally, the Air Force Petroleum Office (AFPET/PTPLA) conducted several tests on the Jet A aviation turbine fuel, hydraulic fluid, and oil samples taken post-accident from the aircraft and servicing equipment. AFPET/PTLA concluded that they were within limits and free of contamination.

(3) Egress System

The T-6A has two Martin Baker MKUS16LA Ejection Seats and two independently fractured canopies that provide emergency escape from the aircraft. This aircraft incorporates a three-mode, inter-seat sequencing (ISS) selector valve, a Canopy Fracturing Initiation System (CFIS), and a Canopy Fracturing Explosive System (CFES). The CFIS and the CFES, combined, make up the Canopy Fracturing System (CFS). The ISS selector valve position, as set by the rear seat pilot, determines the initiation and sequencing of the pilots for ejection.

Review of AFTO Forms 781K maintenance documents and integrated maintenance data system (IMDS) for the MA revealed that egress system maintenance was up to date. A Time Change Technical Order (TCTO) was pending on the canopy fracture initiation system with a required compliance date of 3 August 2022.

Air Force Life Cycle Management Center (AFLCMC/EBHJ) conducted a complete pose-mishap assessment of the egress system. Both the forward and aft aircraft transparencies were fractured by the CFS and spread across the ejection location. Both seats were recovered. The live/unfired aft seat manual override cartridge was removed in the field by egress personnel during the initial response to the mishap.

The position of the ISS selector valve was found in the "BOTH" position, consistent with flight guidance for this type of sortie (dual rated personnel and aircraft having completed TCTO 13A5-69-518. Both seats were recovered with their manual ejection handles in the up "fired" position. Video evidence of the ejection events recovered from a distant security camera indicates that the interval between aft and forward ejections was consistent with ISS timing. The emergency escape system and all of its subcomponents appeared to have operated as intended.

Chapter 7.5. WEATHER

a. Forecast Weather

Randolph AFB (KRND) weather brief (forecast) for the time of the MA takeoff was scattered clouds at 4,000 feet above ground level (AGL), broken clouds at 25,000 feet AGL with winds out of the South at 9 knots gusting to 15 knots. No turbulence or icing conditions were forecast. Isolated area thunderstorms were forecast with maximum tops estimated at 48,000 feet.

At 12:00L, the forecast was updated to scattered clouds at 2,000 feet AGL and broken clouds at 15,000 feet AGL with winds out of the South at 6 knots.

MOA weather forecast was reported as scattered cloud layers from 4,000 to feet, 7,000 feet AGL and between 13,000 feet and 16,000 feet AGL.

b. Observed Weather

On 18 September, 2018 at 14:56L (approximately 45 minutes prior to mishap events), the observed weather was as follows:

Weather at takeoff at Randolph AFB, TX (KRND) according to a meteorological aviation report (METAR) was 10 miles of visibility and few clouds at 3,900 feet and 18,000 feet AGL. The observed winds from the automated weather report were from 170 degrees (South) at 6 knots.

Another METAR issued at 15:48L, as a response to the mishap, observed the weather as 10 miles of visibility and clear skies.

At the time of the mishap, the environmental conditions were full daylight with a fully discernible horizon and no impediment to visibility.

c. Space Environment

Not applicable.

d. Operations

Review of the applicable weather data did not disclose any weather phenomena that met or exceeded any operational limitation for the MA.

Chapter 7.6. HUMAN FACTORS ANALYSIS

n/a

Chapter 7.7. STATEMENT OF OPINION

1. OPINION SUMMARY

On 18 September 2018, at 15:40:41 local (L), a T-6A Texan II, tail number 05-6209, crashed approximately 4.8 miles northwest of Joint Base San Antonio (JBSA)-Randolph, TX, completely destroying the aircraft. The mishap aircrew (MC) consisted of a mishap instructor pilot (MIP), occupying the front seat, who was supervising the mishap pilot (MP). The MP was conducting an instructor upgrade sortie in the Pilot Instructor Training (PIT) course from the rear seat. The MC successfully ejected and sustained minor injuries. The MC and mishap aircraft (MA) were assigned to the 559th Flying Training Squadron, 12th Flying Training Wing, JBSA-Randolph, TX. During the mishap sortie (MS), the MA crashed while returning to base for local take-off and landing practice. The destroyed aircraft is valued at approximately $5.7 million with minor damage to civilian property and no casualties. Environmental remediation was accomplished at the crash site.

I find, by a preponderance of evidence, the cause of the mishap to be a fuel transfer tube locking plate that was improperly installed during a contracted 4500 hour engine overhaul. This resulted in engine failure while the aircraft was not in a position to land safely.

2. CAUSE

The MS was planned to include maneuvers in the nearby Tweet military operating area (MOA), followed by an approach into Kelly Field, and finally, a visual flight rules (VFR) recovery to Randolph for pattern practice. Due to air traffic congestion at Kelly Field, the MC elected to return directly to Randolph for an approach and patterns after departing the MOA. While being vectored for the approach to runway 15R at Randolph, at approximately 15:35:00L, the MC first noticed a high fuel flow reading, and thus decided to continue the approach to a full stop. Slightly over four minutes later, at 15:39:16L, while slowing and configuring to land, the ME failed. At the time of the engine failure, the MA was below the energy profile required to glide to a suitable landing surface.

Post-mishap analysis by the Pratt & Whitney Engineering Department showed that the fuel nozzle transfer tubes between nozzles 9 and 10 were out of position. The transfer tubes transfer fuel between each of the 14 fuel injection nozzles. The transfer tube locking plate, which holds the transfer tubes in the proper position, was improperly installed, thereby allowing the transfer tubes to move. The transfer tubes being out of position resulted in fuel leaking out of the system prior to injection into the engine. Ultimately, despite increased fuel flow, the volume actually reaching the engine was not enough to sustain normal operation, resulting in unrecoverable engine failure.

The Aircraft Accident Investigation Board (AIB) found that neither the Contractor Operated and Maintained Base Supply (COMBS) nor the Maintenance Support Unit (MSU) at JBSA-Randolph, TX inspected or performed any maintenance on the fuel manifold system of the mishap engine (ME). Additionally, the lead Pratt & Whitney Canada investigator testified that the bracket displacement did not occur during ground impact. The preponderance of evidence indicates that the ME arrived from Standard Aero Ltd. with the fuel transfer tube locking plate installed incorrectly during a 4500 hour scheduled engine overhaul.

The incorrectly installed locking plate allowed the fuel transfer tubes to migrate out of position during operation, resulting in a substantial fuel leak. The engine subsequently failed due to loss of adequate fuel supply to sustain operation. Upon recognition of engine failure, the MA was at an airspeed and altitude that made ejection the only viable option.

High fuel flow and "dashed" fuel flow gauge readings alone did not indicate impending engine failure to the MIP and thus, did not require a climb to an altitude from which the MA could glide to land. For that reason, the MIP elected to continue the approach to a full-stop landing, truncating further training. At the point where the MC assessed engine failure/loss of effective thrust, the aircraft was at 1,950 feet above ground level (AGL), 120 knots, and 6.8 nautical miles from the runway surface. T-6A Flight Manual data and simulator re-creations show that an altitude of roughly 3,100' AGL, 800' above the final approach altitude, would have been required to successfully glide to the runway. As the MA was below the required altitude to safely land, the MC was forced to eject.

I find, by a preponderance of evidence, the cause of the mishap to be a fuel transfer tube locking plate that was improperly installed during a contracted 4500 hour engine overhaul. The improperly installed transfer tube locking plate allowed the fuel transfer tubes to migrate out of position during operation. This resulted in a loss of adequate fuel supply to the engine and engine failure at a point when the MA was not in, nor able to reach, a position to land safely.

3. CONCLUSION

I find, by a preponderance of evidence, the cause of the mishap to be a fuel transfer tube locking plate that was improperly installed during a contracted 4500 hour engine overhaul. This resulted in engine failure while the aircraft was not in a position to land safely.

Chapter 8. T-38C Laughlin 2018.11.13

T-38C, T/N 68-8152

LAUGHLIN AIR FORCE BASE, TEXAS

LOCATION: Laughlin AFB, Texas

DATE OF ACCIDENT: 13 November 2018

On the night of 13 November 2018, mishap instructor pilot 1 (MIP1) and mishap instructor pilot 2 (MIP2), flying T-38C tail number (T/N) 68-8152, assigned to 87th Flying Training Squadron, 47th Flying Training Wing, Laughlin Air Force Base (AFB), Texas (TX), conducted a routine training sortie at Laughlin AFB with MIP1 as the pilot in command. During the sortie, at approximately 1924 local time, the mishap aircraft (MA) impacted the ground and MIP1 was fatally injured during an ejection attempt.

The mishap mission was planned and authorized as an instructor development sortie to regain rear cockpit night landing currency for MIP2. During the takeoff portion of MIP2's fifth practice touch-and-go landing at Laughlin AFB, as MIP2 advanced the throttles for takeoff, the mishap crew (MC) heard a loud buzz later determined to indicate a compressor stall in the right engine. MIP1, the aircraft commander, took control of the aircraft and continued the takeoff. MIP1 did not select maximum afterburner as the MA rolled, yawed, and drifted to the right of the runway, failing to accelerate appreciably. While continuing the takeoff, MIP1 failed to recognize aural and visual aerodynamic stall warnings and lost situational awareness regarding the MA's ground track and low height above the ground. MIP1 regained awareness when the MA was close enough to the terrain to illuminate the ground approximately one second before the MA touched down off the runway surface. MIP1 initiated a climb approximately three seconds later and commanded ejection. The MC initiated ejection at approximately 147 knots indicated airspeed, 45 degrees of right bank, with approximately 500 feet per minute descent rate. The MA impacted the ground approximately 350 feet right of the paved runway surface. MIP2 successfully completed the ejection with minor injuries. MIP1 was fatally injured when the MA impacted the ground before MIP1's ejection seat completed the ejection sequence.

The Accident Investigation Board (AIB) President found by a preponderance of evidence the cause of the mishap was the combination of: (a) an engine compressor stall during a critical phase of flight and (b) MIP1's failure to apply necessary throttle and flight control inputs following a loss of thrust on takeoff. Additionally, the AIB President found by a preponderance of evidence that each of the following factors substantially contributed to the mishap: (a) the low illumination the night of the mishap and (b) MIP1's misperception of the rapidly evolving emergency after taking control of the MA.

Chapter 8.1. ACCIDENT SUMMARY

On the night of 13 November 2018, mishap instructor pilot one (MIP1) and mishap instructor pilot two (MIP2) flew a local training mission in a T-38C, tail number (T/N) 68-8152, assigned to the 87th Flying Training Squadron (FTS), 47th Flying Training Wing (FTW), Laughlin AFB, TX. Shortly after touchdown on a touch-and-go, the aircrew heard a noise. The mishap aircraft (MA) then experienced a four degree pitch up and a four degree right heading change followed by increasing angle of attack, right bank, and continuing right heading change. The MA remained airborne for a short time, and then touched down in the grass approximately 55 feet from the edge of the runway, approximately 195 feet from runway centerline in an approximate heading of 13 degrees to the right of the centerline. The right wheel touched down followed by the left wheel approximately 175 feet later. The aircraft remained on the ground for an additional approximate 350 feet, approximately 525 feet total, before again becoming airborne over a shallow depression in the ground. The MA impacted the ground approximately 605 feet later in an approximate 45 degree right bank angle. The Mishap Crew (MC) initiated ejection.

MIP2 ejected successfully and received only minor injuries. MIP1's sequenced ejection, however, was interrupted when the aircraft impacted the ground, and MIP1 was fatally injured.

Chapter 8.2. SEQUENCE OF EVENTS

a. Mission

On Tuesday, 13 November 2018, the MC was scheduled to fly a night, single-ship sortie. MIP1 was the aircraft commander. The flight was a T-38C instructor development sortie to obtain recurrency for MIP2 on rear cockpit nighttime landings. The 87 FTS Operations Supervisor authorized the flight.

b. Planning

MIP1 and MIP2 each flew one previous sortie on 13 November 2018 prior to the mishap sortie (MS). MIP1, the aircraft commander, briefed the sortie according to normal procedures. The mission was planned and briefed as a night rear cockpit recurrency sortie with two instrument approaches followed by visual patterns until MIP2 felt comfortable with rear-cockpit landings. The MC completed an operational risk management (ORM) matrix designed to identify risks for the MS and dictate varying approval authority. MIP2 assessed their risk being low with one point for less than seven hours of sleep and three points for nighttime.

c. Preflight

The Operations Supervisor briefed the pilots to use appropriate procedures for the weather conditions that night. The MC obtained takeoff data and MIP1 signed the flight authorization and filed a flight plan. Engine start was normal with the minor exception that the crew chief had to reset the diverter valve. Such a diverter valve reset is a relatively routine start-up action.

d. Summary of Accident

MIP1 taxied at 18:39, checked the flight controls, then transferred aircraft control to MIP2 to check the flight controls. After being cleared for takeoff at 18:49, MIP2 positioned the aircraft on the runway, checked the engines, then selected afterburner as brakes were released for takeoff at 18:50. MIP2 performed an Instrument Landing System (ILS) approach to a touch-and- go landing. MIP1 demonstrated a visual pattern to a touch-and-go landing, followed by five more visual patterns with three touch-and-go landings by MIP2 and another visual pattern by MIP1. MIP2 then assumed control of the aircraft at 19:21 and performed a visual pattern for MIP2's fifth touch-and-go and mishap crew's ninth approach.

At 19:23:48, the airplane touched down during a touch-and-go landing. The touch-and-go landing was routine with no indications of operational problems. MIP2 advanced the throttles to military (MIL) power. MIL is the power setting used for touch-and-go landings and corresponds to 100% rotational speed of the engine, referred to as revolutions per minute (RPM). Maximum (MAX) power is the power setting that adds afterburner when the engine is already at 100% rotational speed, creating approximately 40% additional thrust. MAX is used for initial takeoff and any time additional thrust is needed.

As the engines were approaching MIL power at 19:23:52, the MC noted a loud noise and queried, "What's that?" with no verbal response identifying the sound. This buzz lasted approximately one to one and a half seconds while the right engine rotational speed decreased from 97% to 66% and the Exhaust Gas Temperature (EGT) began to increase, indicative of a compressor stall and resulting in a loss of most of the thrust being provided by that engine. As this was happening, at 19:23:53, the MA became airborne. MIP2's initial reaction was that the MA experienced a tire failure. MIP2 momentarily reduced power at 19:23:54, then began to increase power towards MIL. The airplane yawed to the right four degrees and began to roll to the right, which led MIP2 to recognize this as a compressor stall. MIP1, the pilot in command, took control of the aircraft at 19:23:54.5 and continued to advance power to MIL power. The left engine operated normally until impact. The right engine never stabilized and continued to oscillate between 65% and 93% RPM with three momentary over temperature indications.

At 19:23:55.1, MIP2 noted a right bank and moved the stick to the left, but MIP1 reiterated that he had control of the aircraft. At 19:23:56, aural, head-up display (HUD), and multi-function display (MFD) stall indications began and continued for the next four seconds as the aircraft continued to roll to the right. According to the Global Positioning System (GPS), at 19:23:57.9, the MA drifted over the edge of the runway with approximately 20 degrees angle of bank and 13 degrees off runway heading. The landing light illuminated the grass at approximately 19:23:58.9, which coincides with MIP1 exclaiming "Dude" and making a small correction to bring the bank angle of the aircraft back to 8 degrees, but the MA returned to 12 degrees of bank to the right. Throughout this time, the MA failed to accelerate appreciably, the aerodynamic stall warning continued, and the maximum height reached was less than 10 feet above ground level (AGL).

At 19:24:00, the aircraft touched down on the grass approximately 55 feet from the runway surface, with the right tire first, followed by the left tire approximately 175 feet later, which leveled the wings, travelling approximately 13 degrees off runway heading. The MA's high pitch and the landing light's downward angle when airborne limited the illumination of the ground until sufficient bank and proximity allowed the MC to see the grass. The MA traveled approximately 350 feet more during which time the aerodynamic stall warning subsided as MIP1 relaxed aft stick pressure. At 19:24:01.5, MIP1 pitched up the nose, and the left engine went to MAX power at 19:24:02.0. This was the first selection of MAX power on either engine since the compressor stall. The MA became airborne at 19:24:02.5.

At 19:24:03.2, as the aircraft reached its maximum pitch, MIP1 commanded ejection. Simultaneously, the MA reached full aerodynamic stall and rolled to the right as the nose dropped. The MA angle of attack indicates that MIP1 released the stick as he finished commanding ejection approximately one second later. The parameters of the aircraft at 19:24:04.9, immediately prior to ejection and impact, with a slightly nose low attitude, 45 degrees of right bank, a descent rate of 500 feet per minute, and an airspeed of 147 knots. The MC initiated ejection. MIP2 successfully ejected and sustained minor injuries. However, impact interrupted MIP1's ejection sequence after the canopy departed but before the forward seat ejected.

e. Impact

At approximately 19:24:05, with the approximate parameters of seven degree nose low at 145 knots with 45 degrees of right bank and approximately 350 feet right of the runway surface (approximately 500 feet from runway centerline), the aircraft's right wing impacted a relatively level grassy field, immediately followed by the right tire, separating the wing assembly, and rolling the fuselage.

f. Egress and Aircrew Flight Equipment (AFE)

The MC set the MA's Inter-seat Sequencing System (ISS) in the BOTH position. When the ISS is in the BOTH position, the ejection sequence will follow these steps under normal circumstances: 1) either pilot pulls the ejection handle, 2) the rear cockpit canopy jettisons, 3) the rear seat catapult fires 0.4 seconds later, 4) the front canopy jettisons at 0.85 seconds after ejection is initiated, 5) the front seat catapult fires 0.4 seconds later, and 6) the front seat leaves the aircraft. The ejection sequence is the same regardless of which pilot initiates ejection. The entire sequence lasts 1.3 seconds from initiation of the ejection to the front seat leaving the aircraft.

MIP2 pulled the rear cockpit (RCP) ejection handle, but engineering analysis was unable to ascertain whether MIP1 also pulled the front cockpit (FCP) ejection handle or if impact dislodged the handle. Specialists analyzed the ejection and determined that the rear cockpit (MIP2) ejected normally. Further analysis showed the front seat ejection sequence (MIP1) was also normal until after the front cockpit canopy departed, but before the front seat catapult fired 0.4 seconds later. Analysis revealed the front seat catapult would have functioned properly; however, impact with the ground interrupted the remaining ejection sequence.

The MA was not within the parameters required for successful completion of the ejection sequence due to the descent rate and bank angle at the time of ejection.

MIP1 and MIP2's AFE performed adequately and did not contribute to any injuries.

At the time of the mishap, all AFE inspections were current.

MIP1 and MIP2 each had a Personnel Locator Beacon (PLB), which transmits an Emergency Locator Transmitter (ELT) signal when it functions properly. Two aviators, who were airborne at the time of the mishap, reported an ELT signal. The air traffic control (ATC) tower did not hear an ELT signal. MIP1's PLB activation lanyard was broken, which prevented MIP1's PLB from transmitting an ELT signal. Post-mishap engineering analysis did not include determination of whether the lanyard was broken before or during the mishap sequence. MIP2's PLB passed all tests post-mishap.

g. Search and Rescue (SAR)

A pilot in the ATC tower witnessed the mishap and immediately informed the ATC tower supervisor. One of the air traffic controllers immediately initiated a conference call to inform other base agencies. Airfield Management answered, followed by the Laughlin Fire Department. The controller informed all parties available at 19:26 that a T-38C had slid off Runway 31R with two persons on board. The Fire Department dispatched units at 19:28 with units proceeding at 19:29. Due to the dark conditions, Fire Department personnel had difficulty finding the MA. The Fire Department found the MA approximately seven minutes after dispatch and found MIP2. MIP2 was transported and treated at the local hospital for minor injuries. At 19:46, the Incident Safety Officer found MIP1, recognized fatal injuries, and reported MIP1 was deceased.

h. Recovery of Remains

At 19:46, MIP1 was found near the crash site at Laughlin AFB. Laughlin AFB Security Forces personnel secured the area. At approximately 20:39, the responding flight surgeon identified MIP1 as deceased. Later that evening, the Val Verde County Precinct Three Justice of the Peace responded to the scene because Laughlin AFB is not a federal jurisdiction. The Justice of the Peace inspected MIP1 and pronounced MIP1's death.

Chapter 8.3. MAINTENANCE

a. Forms Documentation

There are two discrepancies between the active AFTO Form 781H and the historical AFTO Form 781H. The first discrepancy is the active AFTO Form 781H, Block 1 "FROM" should match the date in the historical AFTO Form 781H, Block 2 "TO," but the dates do not match. The second discrepancy is an incorrectly formatted "CARRY FORWARD" in Block 5 "ACCOMPLISHED BY" of the historical AFTO Form 781H. There is no evidence to suggest that these minor transcription errors were factors in this mishap.

The historical records do not reveal any recurring maintenance problems in the 90 days prior to the mishap.

b. Inspections

The maintenance crew chief completed scheduled thruflight inspections on 13 November 2018, prior to the MS, in accordance with (IAW) AF TO 1T-38C-6WC-1, Thruflight Workcards, with no discrepancies noted.

A qualified crew chief collected 20-hour Joint Oil Analysis Program (JOAP) samples on 13 November 2018, prior to the MS. A non-destructive inspection (NDI) noted no discrepancies in the samples. At the time of the JOAP inspections, the MA had 16,743.4 total flight hours. All scheduled inspections were completed according to standards and documented IAW applicable technical data.

c. Maintenance Procedures

There is no evidence to suggest that maintenance procedures were a factor in this mishap. The historical records do not reveal any recurring maintenance problems in the 90 says prior to the mishap.

d. Maintenance Personnel and Supervision

There is no evidence to suggest that maintenance personnel or supervision were factors in this mishap. All personnel who performed maintenance on the MA in the 90 days prior to the mishap were qualified to perform their duties.

e. Fuel, Hydraulic, Oil, and Oxygen Inspection Analyses

Fuel, hydraulic, oil, and oxygen inspection analyses from the MA revealed no abnormalities relevant to this mishap.

f. Unscheduled Maintenance

The T-38C requires external pneumatic pressure to start the engines on the ground. Although considered a relatively routine start-up action and not maintenance, during engine start for the MS, a maintenance professional manually reset the diverter valve. The diverter valve is attached to the left engine and only functions to direct the pneumatic pressure during initial engine start on the ground. The diverter valve directs external pneumatic pressure to start the right engine. The maintainer then manually rotates the diverter valve to direct pneumatic pressure to start the left engine. Once the engines have started and the external air hose is removed from the aircraft, the diverter valve has no further function during engine operation. There is no evidence to suggest this was a factor in the mishap.

Chapter 8.4. AIRFRAME, MISSILE, OR SPACE VEHICLE SYSTEMS

a. Structures and Systems

A post -accident engineering analysis indicated the right engine encountered an anomaly that caused the engine speed to drop and exhaust gas temperature (EGT) to rise. The buzz, drop in speed, and rise in EGT are all indicative of a compressor stall.

An engine compressor stall is a disruption of air flow through the compressor section of the engine. In the course of this mishap, the right engine experienced a decrease in RPM from 97% to 66%, which corresponds to a loss of thrust. Compressor stalls are more common in high performance aircraft like the T-38C with axial flow engines which balances maximum performance with an acceptable compressor stall margin. The following factors decrease the compressor stall margin and may lead to a compressor stall:

F. Engine structural failure

G. Foreign object damage (FOD)

H. Incorrect fuel flow trim

I. Engine nozzle mis-scheduling

J. High aircraft angles of attack at low airspeeds

K. Low compressor inlet temperatures

L. Maneuvering flight

M. Unusual flight attitudes

N. Atmospheric variations

O. Jet wash

P. Temperature and pressure distortion

Some of these potential causes can be ruled out as the cause of the compressor stall in this mishap. There were no skid marks or damage to the runway and no obvious signs of large FOD hazards. A post-mishap engineering engine analysis stated there was no indication of structural disk failure, no indication of FOD, and all damage appeared to be caused by the impact. Although engine tear down and analysis could not determine the exact cause of the compressor stall, there is no evidence that a mechanical issue caused the compressor stall in this mishap.

Although evidence does not point to a single factor, there were a number of factors which would have decreased the stall margin and when combined could have resulted in a compressor stall. The aircraft was at a moderate angle of attack with a low airspeed. The temperature that evening was mildly cold and decreased the temperature at the compressor inlet. Additionally, there may have been any combination of atmospheric variations, jet wash, and temperature or pressure distortions. Although not definitive, each of these possible factors may have combined to lower the stall sensitivity past the critical point for compressor stall.

Below Table shows those factors that have no evidence to suggest they contributed and those factors, which were present and could have contributed to a compressor, stall:

Factors which can reduce the stall margin and contribute to compressor stalls:

Engine structural failure: No evidence to suggest contributed

Foreign object damage (FOD): No evidence to suggest contributed

Incorrect fuel flow trim: No evidence to suggest contributed

Engine nozzle mis-scheduling: No evidence to suggest contributed

High aircraft angles of attack at low airspeeds: Possibly contributed

Low compressor inlet temperatures: Possibly contributed

Maneuvering flight: No evidence to suggest contributed

Unusual flight attitudes: No evidence to suggest contributed

Atmospheric variations: Possibly contributed

Jet wash: Possibly contributed

Temperature and pressure distortion: Possibly contributed

With the exception of the compressor stall, there is no evidence to suggest that other structures and systems were factors in this mishap.

b. Evaluation and Analysis

There is no evidence to suggest that any data retrieved from evaluation and analysis were factors in the mishap.

c. Simulator Replication

The AIB conducted multiple events simulating the touch-and-go landing, subsequent compressor stall, and different courses of action in the T -38 Operational Flight Trainer (OFT). The aircraft was fully recoverable every time the AIB applied MAX power and raised the flaps to 60% in accordance with the first two steps of the single- engine go-around checklist. At no time was the takeoff recoverable in the simulator without using MAX thrust. However, leveling the wings with aileron only while using MIL thrust did provide more time for the MC to analyze the situation before the aircraft impacted rising terrain to the right of the runway. The aircraft was recovered on multiple attempts when the board selected MAX (afterburner) and rolled wings level at the same time stall indications were experienced by MIP1 after taking the MA. Each of these attempts was performed with only the left engine in afterburner and full flaps remaining down throughout the stall recovery.

Chapter 8.5. WEATHER

a. Forecast Weather

On 13 November 2018, forecast weather for the time of the MS was clear skies, unrestricted visibility, winds out of the north at eight knots, temperature 6 degrees Celsius, density altitude of negative 387 feet, with no precipitation. A waxing crescent moon was projected to provide 33% lunar illumination.

b. Observed Weather

Observed weather near the time of the accident was clear skies, unrestricted visibility, winds out of the north-west at seven knots, 5 degrees Celsius (41 degrees Fahrenheit), with an altimeter setting of 30.53 inches of mercury. Witnesses noted that it was very dark that evening. MIP2 testified that there was no visible horizon when the runway lights were not in view and described approaching the runway as a "black hole".

c. Space Environment

Not Applicable

d. Operations

The MA was operating within prescribed weather requirements. However, low compressor inlet temperatures and/or high angles of attack at low airspeeds can increase stall sensitivity and decrease the compressor stall margin.

Chapter 8.6. HUMAN FACTORS ANALYSIS

a. Introduction

Human factors describe how our interaction with tools, tasks, working environments, and other people influence human performance. Human factors are the leading cause of Department of Defense (DoD) mishaps. The DoD Human Factors Analysis and Classification System (DoD HFACS) Version 7.0 identifies human factors using HFACS codes and provides a template that organizes the human factors identified in a mishap investigation.

b. AE102 Checklist Not Followed Correctly

HFACS Code AE102, Checklist Not Followed Correctly, is a factor when the individual, either through an act of commission or omission, makes a checklist error or fails to run an appropriate checklist.

Maintaining aircraft control is the most important part of any emergency. TO 1T-38C-1 states:

When an emergency occurs, three basic rules are established that apply to most emergencies while airborne. They should be remembered by each aircrew member.

1. Maintain aircraft control.

2. Analyze the situation and take proper action.

3. Land as soon as practical.

If an engine operates abnormally or fails during flight, TO 1T-38C-1 advises pilots to reduce drag to a minimum and maintain airspeed and directional control while investigating to determine the cause. Single-engine directional control can normally be maintained at all speeds above stall. After the MA's right engine experienced a compressor stall, the MA rolled and yawed to the right. MIP1 did not apply throttle or stick and rudder inputs sufficient to maintain control of the MA, and at 19:23:57, the MA over-flew the side of the prepared surface.

The flight manual directs the single-engine go-around checklist any time thrust is questionable on takeoff and a decision is made to continue takeoff. The first two actions of the SINGLE -ENGINE GO-AROUND checklist are: 1. THROTTLE(S)-MAX, 2. FLAPS-60%. Pilots are warned that continuing a takeoff on a single engine should be attempted only at maximum thrust. Pilots are warned that, with other than 60% flaps, single-engine capability is impaired to such an extent that the combination of temperature, pressure altitude, and gross weight may make takeoff impossible. MIP1 did not move throttles to MAX until 19:24:02, 10 seconds after hearing a noise and one second before commanding ejection. The MC did not raise flaps to 60% at any point during the emergency.

After the MA took off following the compressor stall, a blinking boxed STALL indication on the HUD and MFD plus a modulated aural tone indicated that the MA was approaching an aerodynamic stall. In this situation, pilots are trained to execute a traffic pattern stall recovery. Stalls can be terminated by simultaneously moving throttles to MAX, relaxing backstick pressure, and rolling wings level. MIP1 did not move throttles to MAX or roll wings level as the stall indications continued.

c. PC504 Misperception of Changing Environment

HFACS Code PC504, Misperception of Changing Environment, is a factor when an individual misperceives or misjudges altitude, separation, speed, closure rate, road/sea conditions, aircraft/vehicle location within the performance envelope or other operational conditions.

While both MIP1 and MIP2 had practiced emergency procedures for compressor stall scenarios, neither had previously experienced an actual compressor stall. The flight manual describes compressor stall indications at low altitude and high airspeed as follows: Pop, bang, or buzz with rapid engine rotational speed drop or high EGT. During a post-mishap interview, MIP2 noted that the sound he heard in the aircraft was not similar to the sound associated with compressor stalls during emergency procedure simulator training. MIP2 stated that he initially identified the emergency as a blown tire rather than a compressor stall or engine problem.

Touch-and-go landings are the only time the T-38C flight manual refers to a critical phase of flight. The slow airspeed, close proximity to the ground, and multiple tasks that must be accomplished during a touch-and-go landing increase the complexity of emergencies and limit the time available for applying critical procedures.

TO 1T-38C-1 advises that ejection is preferable to landing on an unprepared surface. The MA overflew the right side of the prepared surface at 19:23:57 and touched down in the grass at 19:24:00. The MA landing light illuminated the grass in the field to the right of the runway approximately one second before the MA touched down. This is the first time there is any indication that MIP1 or MIP2 knew they were no longer over the runway surface and were so close to the ground. The MA remained on the ground until 19:24:02. Neither crewmember commanded ejection until 19:24:03, six seconds after departing the runway and three seconds after touching down off the prepared surface.

d. PE101 Environmental Conditions Affecting Vision

HFACS Code PE101, Environmental Conditions Affecting Vision, is a factor that includes obscured windows; weather, fog, haze, darkness; smoke, etc.; brownout/whiteout (dust, snow, water, ash or other particulates); or when exposure to windblast affects the individual's ability to perform required duties.

Darkness limits pilots' ability to accurately perceive the external environment, contributing to visual illusions that can interfere with safe flight. Altitude and rate of descent are more difficult to judge close to the ground. Sloping or featureless terrain, sloping runways, varying runway widths, runway lighting intensity, and (or) weather phenomena can cause visual illusions at night. One well-known hazard occurs during take-off on dark, moonless or overcast nights where the terrain off the runway is devoid of ground lights and no horizon is discernable. As an aircraft lifts off into such a "black hole", pilots relying on external visual cues may fail to accurately assess their climb angle and proximity to terrain. During flight operations that rely upon external cues for guidance, misperception of the environment is more likely at night than during the day. Visual references and depth perception change with night operations.

Multiple times during the MS, the MC commented on the darkness of the airfield environment, both while taxiing with the landing light on and while airborne.

18:44:26 MIP1: "Me as well... I'm just here... It is [...] dark out here dude."

18:44:36 MIP2: "I was gonna say dude, I'm not getting a ton of lume right now out of this, this thin quarter moon or whatever."

18:44:42 MIP1: "I-I've got this landing light out in front of me and I got [...] nothing dude. I can't see [...]."

18:46:49 MIP2: "Yea, It's dark."

18:46:52 MIP1: "It's really dark dude."

19:00:48 MIP2: "Ooh buddy, man, that is, that is it is darker than usual."

19:00:50 MIP1: "I'm fine, I'm fine. It's freaking dark dude, it is really dark. It is mad dark, dude."

19:05:12 MIP1: "That's pretty late, dude...The uh, I don't see the light on top of that

shack to be honest with you. That's what I was looking for."

19:05:22 MIP2: "Uh, I can't. Yea I can't really see anything out here."

19:05:23 MIP1: "That's true, dude."

19:05:25 MIP2: "But uh, oh well. I can't. I can't really see anything out here."

During a post mishap interview, MIP2 described the appearance of the runway environment on approach stating, "It's a black hole. It is – it is either way you slice it but off the perch you perch into a black hole". He also described the environment where the emergency occurred explaining that "once the nose points away from the runway there's no horizon out off [runway] 31". The MA's high pitch angle and its landing light's downward angle when airborne further limited the illumination of the ground until sufficient bank and proximity allowed the MC to see the grass.

Chapter 8.7. STATEMENT OF OPINION

1. OPINION SUMMARY

On the night of 13 November 2018, mishap instructor pilot 1 (MIP1) and mishap instructor pilot 2 (MIP2), flying T-38C tail number (T/N) 68-8152, assigned to Laughlin Air Force Base (AFB), Texas (TX), engaged in a routine training sortie at Laughlin AFB with MIP1 as the pilot in command. During the sortie, at approximately 19:24 local time, the mishap aircraft (MA) impacted the ground and MIP1 was fatally injured during an ejection attempt.

The mishap mission was planned and authorized as an instructor development sortie to regain rear cockpit night landing currency for MIP2. During the takeoff portion of MIP2's fifth touch-and-go landing (mishap crew's (MC) ninth approach) at Laughlin AFB, the MA experienced a compressor stall in the right engine. The MA initially experienced a four degree pitch up and a four degree right heading change, followed by continuing heading change. The MA remained airborne for a short time and then touched down approximately 55 feet from the runway surface (approximately 195 feet from runway centerline) in an approximate heading of 13 degrees to the right of the original runway heading. The MA remained on the ground for approximately 525 feet before again becoming airborne over a shallow depression in the ground. The MA impacted the ground approximately 605 feet later (350 feet right of the runway surface and 500 feet from runway centerline), seven degrees nose low, and at a 45 degree right bank angle.

During the takeoff portion of the touch-and-go, the mishap crew heard a loud buzz corresponding to the compressor stall. MIP2 momentarily reduced the power after the sound but then elected to continue to takeoff and increased the throttles toward military (MIL), non-afterburner power, corresponding to the power setting used for the takeoff portion of touch-and- go landings. MIP1 then took command of the aircraft and continued the takeoff without selecting maximum (MAX) afterburner, corresponding to maximum engine thrust, as the MA rolled and yawed to the right, drifted right of the runway, and failed to accelerate appreciably. As MIP1 continued the takeoff, MIP1 failed to recognize aural and visual aerodynamic stall warnings and lost situational awareness regarding MA ground track and low height above the ground. This loss of situational awareness lasted for approximately four seconds and was exacerbated by the low illumination that night. MIP1 regained awareness when the MA landing light illuminated the ground approximately one second before the MA touched down to the right of the runway surface. Approximately three seconds later, MIP1 commanded ejection and the MC initiated ejection at approximately 147 knots indicated airspeed as the MA rolled into approximately 45 degrees of right bank with approximately 500 feet per minute descent rate. MIP2 successfully completed the ejection with minor injuries. MIP1 was fatally injured when the MA impacted the ground before MIP1's ejection seat completed the ejection sequence.

I find by a preponderance of evidence the cause of the mishap was the combination of: (a) an engine compressor stall during a critical phase of flight and (b) MIP1's failure to apply necessary throttle and flight control inputs following a loss of thrust on takeoff. Additionally, I find by a preponderance of evidence that each of the following factors substantially contributed to the mishap: (a) the low illumination the night of the mishap and (b) MIP1's misperception of the rapidly evolving emergency after taking control of the MA.

2. CAUSE

I find by a preponderance of evidence the cause of the mishap was the combination of: (a) an engine compressor stall during a critical phase of flight and (b) MIP1's failure to apply necessary throttle and flight control inputs following a loss of thrust on takeoff. The subsequent chain of events led to MIP1 and MIP2 initiating ejection too late for MIP1's ejection seat to complete the ejection sequence before the MA impacted the ground.

a. Engine Compressor Stall

The flight manual describes compressor stall indications at low altitude and high airspeed as follows: Pop, bang, or buzz with rapid engine rotational speed drop or high exhaust gas temperature (EGT). During multiple touch-and-go landings simulated in the T-38 Operational Flight Trainer (OFT), compressor stall indications showed a definite decrease in engine speed, clear and consistent over temperature in EGT, and made sounds that were not similar to the buzz sound in the mishap.

The aircraft began takeoff when at approximately 19:23:52, a loud buzz lasting approximately one to one and a half seconds was heard by the MC. The aircraft yawed to the right and began to roll to the right. At the time of the buzz the right engine rotational speed started dropping from 97% to 66% and then oscillated between 65% and 93%. The left engine continued to operate normally. Post-accident engineering analysis indicated the right engine encountered an anomaly that caused the engine speed to drop and exhaust gas temperature (EGT) to rise. I determined that these engine indications, the buzz, and eyewitness testimony indicate the MA right engine experienced a compressor stall.

I could not determine the cause of the compressor stall. Subsequent engine teardown and analysis was not able to determine the cause of this compressor stall. I was able to rule out the following as causes of the compressor stall: engine structural failure, Foreign Object Damage, incorrect fuel flow trim, engine nozzle mis-scheduling, maneuvering flight, and unusual flight attitudes.

Touch-and-go landings are the only time the T-38C flight manual refers to a critical phase of flight. The slow airspeed, close proximity to the ground, and multiple tasks required that must be accomplished during a touch-and-go landing increase the complexity of emergencies, limit the time available for considering and applying critical procedures, and lower the reaction time to recover the airplane in the event of a malfunction.

The compressor stall caused the MA to experience a loss of thrust and directional control challenges during a critical phase of flight, which caused the mishap.

(3) MIP1's Failure to Apply the Necessary Throttle and Flight Control Inputs Following a Loss of Thrust on Takeoff

The touch-and- go landing was routine with no indications of operational problems. The decrease in thrust on the right side of the aircraft corresponded with the right yaw and roll and subsequent aircraft travel to the right of the runway. MIP1 took control of the MA at 19:23:54.5 and continued the takeoff in MIL. Aural, head-up display (HUD), and multi-function display (MFD) stall indications began at 19:23:56.9. During the approximately five seconds after MIP1 took control of the aircraft, with the exception of one brief input by MIP2 to level the wings at 19:23:55.6, the MA continued to track to the right of the runway, never climbed higher than 10 feet above the ground, did not appreciably accelerate, and continued to roll to the right until reaching approximately 20 degrees of right bank. The aerodynamic stall warning continued during this entire time. When I studied the HUD video and post-mishap engineering analysis, I observed no apparent attempt made by MIP1 to roll wings level or increase the throttles toward MAX power until commanding ejection.

There are three flight manual checklists that, had MIP1 followed one of them correctly, may have prevented the mishap: (1) Maintain aircraft control is the first step in any emergency situation and would have required MIP1 to level the MA wings, maintain runway alignment, and select MAX power due to proximity to the ground and lack of acceleration. (2) The flight manual directs the single-engine go-around checklist any time thrust is questionable on takeoff and a decision is made to continue takeoff; the first two steps in this critical action procedure are to select MAX on one or both throttles and raise the flaps to 60%. (3) The steps required to recover from a traffic pattern stall, recognized by aircraft buffet, HUD, MFD, or aural tone, is to simultaneously apply MAX power, roll wings level, and relax back stick pressure to stop the stall.

The AIB conducted multiple events simulating the touch-and-go landing, subsequent compressor stall, and different courses of action in the T-38 Operational Flight Trainer (OFT). At no time was the takeoff recoverable in the simulator without using MAX thrust. However, leveling the wings while using MIL thrust did provide more time for the MC to analyze the situation, regardless of rudder inputs, before the aircraft impacted rising terrain to the right of the runway. The aircraft was recovered on multiple attempts when the board selected afterburner and rolled wings level at the same time stall indications were experienced by MIP1 after taking the MA. Each of these attempts was performed with only the left engine in afterburner and full flaps remaining down throughout the stall recovery. The aircraft was fully recoverable every time the AIB applied MAX power and raised the flaps to 60% in accordance with the first two steps of the single-engine go-around checklist.

Based on the other evidence and the above OFT events, MIP1's failure to apply necessary throttle and flight control inputs following a loss of thrust on takeoff caused the mishap.

3. SUBSTANTIALLY CONTRIBUTING FACTORS

I find by a preponderance of evidence that each of the following factors substantially contributed to the mishap: (a) the low illumination the night of the mishap and (b) MIP1's misperception of the rapidly evolving emergency after taking control of the MA.

a. Night Conditions Affecting Vision

Flight operations relying upon external visual cues for guidance are known to be riskier at night than during the day. Darkness limits pilots' ability to accurately perceive the external environment, contributing to visual illusions that can interfere with safe flight. One well-known hazard occurs during take-off on dark, moonless, or overcast nights where the terrain off the runway is devoid of ground lights and no horizon is discernable. As an aircraft lifts off into this "black hole," pilots relying on external visual cues may fail to accurately assess their climb angle and proximity to terrain.

As I reviewed the HUD video, I observed MIP1 and MIP2 commenting during the MS that it was very dark that night. Testimony from multiple witnesses confirmed the same. The MA was airborne for approximately six seconds between the compressor stall and touching down 55 feet right of the runway. The MA's high pitch during this time, combined with the landing light's angle when airborne, created the effect that the ground was not illuminated until sufficient bank and closer proximity allowed pilots to see the grass. Inferring from MIP1's control of the MA and a statement of surprise on the HUD video, the first indication that MIP1 was aware he was right of the runway surface and descending to the ground was when the MA landing light illuminated the grass approximately one second before touching down. Had this mishap occurred during daylight hours, daytime conditions with adequate view of the horizon would have provided peripheral vision cues to alert MIP1 that the MA was drifting away from the runway, continuing to roll to the right, and subsequently descending to the grass. The lack of these cues exacerbated MIP1's inability to perceive the changing environment or recognize the need for increased power. The darkness also prevented the MC from recognizing the need to initiate ejection until it was too late for MIP1's ejection seat to complete the ejection sequence before the MA impacted the ground.

b. Misperception of the Rapidly Evolving Emergency

The MC had accomplished eight routine instrument and visual patterns at Laughlin AFB prior to the final touch-and-go. Upon hearing the compressor stall, a member of the MC stated, "What's that?" and there was no verbal response, indicating the MC failed to immediately recognize the sound as a compressor stall. MIP2 initially considered discontinuing the takeoff and reduced the throttles before reconsidering this action because of a possible tire failure on takeoff. At no point in the remainder of the flight did MIP1 indicate recognition of a compressor stall or other engine malfunction. Neither MIP had experienced an actual compressor stall in the T-38C.

During the approximately four seconds after MIP1 took control of the MA and before it touched down 55 feet right of the runway, the MA continued to roll and drift to the right and failed to accelerate appreciably. I was unable to determine what specific actions MIP1 was taking during this time, but engineering analysis of engine indications throughout the mishap sequence showed no attempt to select MAX power on either engine until 19:24:02.0, approximately one second before MIP1 commanded ejection. HUD video revealed there was no apparent attempt made by MIP1 to roll wings level prior to the landing light illuminating the grass. MIP2 testified that after MIP1 took control of the aircraft, MIP2 intervened to attempt to level the wings by pushing the stick to the left, which indicated to me that MIP1 was unaware that the MA was rolling to the right.

There was a loud and unfamiliar sound, unexpected change in aircraft control, engine indications that did not clearly indicate a compressor stall or significant engine anomaly, and an engine malfunction neither MIP had experienced in an actual T-38C. These combined to create the effect that MIP1 did not perceive that the MA was drifting right of the runway surface at a very low altitude, nor did he react appropriately to the aural, HUD, or MFD stall indications. MIP1's failure to recognize the rapidly developing situation until the landing light illuminated the grass and subsequent decision to attempt to climb the MA after touching down led to the MC's ejection attempt being too late for MIP1's ejection seat to complete the ejection sequence before the MA impacted the ground.

4. CONCLUSION

I find by a preponderance of evidence the cause of the mishap was the combination of: (a) an engine compressor stall during a critical phase of flight and (b) MIP1's failure to apply necessary throttle and flight control inputs following a loss of thrust on takeoff. Additionally, I find by a preponderance of evidence that each of the following factors substantially contributed to the mishap: (a) the low illumination the night of the mishap and (b) MIP1's misperception of the rapidly evolving emergency after taking control of the MA.

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