sonic booms created by aircraft flying
faster than the speed of sound certainly
aren't known for being faint but rather
for their loud make you jump effect but
sonic booms also have a quieter side
pretty simple but it wasn't always this
way 50 years ago he was flying a very
different airplane a small rocket plane
he was just hoping to get through what
was then called the sound barrier the
problem he was facing was called
compressibility a strange behavior of
airflow as its velocity approached the
speed of sound it had been encountered
by fighter pilots during the recent war
pushing over into steep dives it found
themselves at speeds of 500 miles per
hour roughly 75% of the speed of sound
and into the lower limits of the unknown
region of transonic flight with the
effects of compressibility loss of
control and structurally devastating
aerodynamic loads began to take over and
often deadly consequences
aerodynamicists knew that as aircraft
entered the transonic region the region
between 0.7 and 1.3 Mach they were
passing into an area of unpredictable
airflow conditions even at subsonic
speeds the airflow over the wings could
be supersonic and this caused shockwaves
which violently disrupted the airflow
and drastically altered an airplane's
controllability furthermore many of them
theorized that as an aircraft approached
the speed of sound or Mach 1 the virtual
wall of air were built up in front of it
which would be impenetrable
man who more than anybody else was
responsible for the airplane which
disproved the myth of a sound barrier
was major
Ezra Kocher of the engineering division
at Wright Field as early as 1939 still a
civilian teaching at the Air Corps
engineering school he was aware that
Windows was choked and transonic
velocities would never solve the problem
thus he proposed that the Air Corps
should build an experimental airplane
which would have to be powered by some
form of unconventional propulsion
perhaps a rocket engine the leadership
of the new US Army Air Forces turned a
deaf ear on his proposal until the
advent of turbojet technology made it
clear that the means were now at hand
propel aircraft level flight to speeds
well above those that conventional
piston engine fighters could attain only
and steep dives meanwhile John stack a
research scientist for the National
Advisory Committee for Aeronautics or
NACA
had arrived at the same conclusion and
it convinced the NACA to pursue with the
military's assistance the development of
a transonic research airplane stackin
Kotter disagreed however over both means
and ends John stack wanted a
conventional turbojet powered aircraft
to acquire data at speeds approaching
Mach 1 he got his airplane but it was
acquired for the NACA by the Navy first
flown in 1947 the Douglas d558 sky
screen would exceed Mach 1 only once
while in a steep dive late September
1948 Kocher on the other hand from the
very outset insisted on a rocket powered
airplane capable of attaining speeds in
excess of Mach 1
and by early 1944 he'd come up with a
preliminary design for an aircraft which
would be built around a 6,000 pound
thrust liquid fuel rocket engine this
served as a starting point for the Bell
Aircraft Corporation when in December
1944
Kocher negotiated a contract to design
and build an airplane capable of speeds
in excess of 800 miles per hour because
they knew 50 caliber bullets were stable
at supersonic speeds bell engineers
shaped the fuselage accordingly because
no one knew what they did encounter at
the speed of sound the airframe was
stressed withstand more than 18 G's and
while John stack was none too optimistic
about the prospects for a rocket plane
especially one which would have to be
air launched the NACA
made major inputs to the design process
based on evidence that thin wings
retained more effective lift in the
transonic region the agency recommended
that the airplane be configured with
what for the day were extremely thin air
fluids equally important the NACA
insisted that the elevator should be
placed on an all moving horizontal tail
which could if necessary the employed to
maintain control of the airplane at
extremely high speeds after overcoming a
host of unknowns and design problems
Bell completed the first x1 in December
of 1945 because development of its
reaction motors XLR 11 rocket engine and
lagged it was transported to Pine Castle
Army Airfield in Florida for a series of
unpowered glider aimed at demonstrating
the feasibility of air launch operations
as well as the basic flying qualities of
the x1
bells chief test pilot Jack Williams was
selected as project pilot for the x1
program and on January 25th 1946 he
dropped away from the b-29 launch
aircraft for the first time a skilled
and experienced test pilot Willems
thoroughly enjoyed the flight and
reported that of all the aircraft he'd
flown the x1 was in his words the most
delightful one to fly of them all he
completed a total of 10 glide flights at
fine castle but weather problems in a
series of landing mishaps had delayed
the program and convinced the Air Force
that the powered flights should be
conducted elsewhere Jack Williams was
scheduled to make those flights in
August however he was tragically killed
while flying a souped-up p39 in
preparation for the 1946 Thompson Trophy
air race the x1 would fly at another
location and with another pilot in the
cockpit that location was Muroc Army Air
Field on California's high desert it's
clear skies isolation and the tremendous
margin of safety afforded by its immense
dry lakebed which served as a natural
landing field in at the ideal place to
test an exotic ultra-high performance
airplanes such as the x1 vales new pilot
was 23 year old Chalmers H slick Goodley
under the terms of the acceptance
program Bell was only obligated to
demonstrate the X one's air worthiness
up to a speed of point eight Mach
but if the airplane held together the
chances were slick Goodman would have
the opportunity to make the assault on
Mach 1
but first preparations had to be
completed for Belle's acceptance program
the 6000 pound thrust XLR 11 rocket
engine for example underwent exhausted
ground tests pressurized by nitrogen gas
and employing liquid oxygen and water
alcohol as propellants each of its four
chambers provided 1,500 pounds of thrust
by means of a switch on the control yoke
in the cockpit the pilot could ignite or
shut down each chamber individually so
he could operate at 25 50 75 or 100
percent power the purpose of the program
was of course to acquire information
about the transonic flight machine
walter C Williams headed up an NACA
contingent of engineers and technicians
who were responsible for instrumenting
the x1 and then acquiring reducing and
analyzing the data though primitives by
latter day standards the x1 is the most
thoroughly instrumented airplane of its
day carrying roughly 500 pounds of
onboard acquisition and recording
instruments to obtain data on stability
control and arrows in addition radar the
technology new to flight test would be
employed to track the x1 in flight the
powered flight program got underway at
Muroc on December 9th 1946 as the b-29
mothership cleared the runway and
commenced its long slow climb to
altitude
the moment of truth finally occurred at
27,000 feet as the launch count end and
the x1 dropped away from the bomb bay
into the b-29
while this program was proceeding a
tortuous deliberation process was
underway concerning who would fly the
accelerated program for the assault on
Mach 1 the NACA
or Bell by any definition those flights
would be research flights and the NACA
had the Charter for flight research but
it hadn't shown any eagerness to risk
the hazards of flying the rocket plane
the one advantage that I had probably in
in doing research flying was I had been
very disciplined in combat meaning if
you have no control over the outcome
forget it
Duty is paramount that's duty do you fly
and when you fly combat you know that a
lot of people going to kill you just
hope since you have no control over it
and if you get killed you don't know
anything about anyway so so you you wipe
it out of your mind and you're able to
ignore it completely and concentrate on
what you're doing so it was real easy to
me for me to transition into research
flying and test work because I could
concentrate on what I was doing probably
without worrying about the outcome
Boyd chose another extraordinarily
gifted pilot first lieutenant Bob Hoover
as Yeager's backup and chase planner the
assigned yet another test pilot captain
Jackie L Ridley led a master's degree in
aeronautical engineering from Cal Tech
as the engineer in charge or Jack C
Hoover and I were definitely not that
flight test engineers we could fly
airplanes and we had a an instinct you
know for aerodynamics but Jack Ridley
was a brain Jack Ridley knew everything
there was to know about aerodynamics and
he was practical and that's exactly and
besides that he was a good pilot
and he fit in with us finally Boyd
selected one of his best multi engine
test pilots major Robert L Bob Cardenas
to fly the b-29 launch aircraft as the
ranking officer had also served as the
officer in charge of the x1 test unit at
Murad
when the team arrived at Muroc in late
July 1947 Jaeger Hoover and Ridley were
provided training on the x1 and all of
its systems by Richard H dick frost
frost who'd been bells chief flight test
engineer on the airplane was on loan to
the Air Force to provide technical
guidance and to fly low chase on all of
Yeager's missions dick knew the x1
intimately he knew all the mechanics of
it and he it was his his job to teach us
everything that a pilot could do you
know to the x1 from the cockpit so he
didn't have much of a technical
background Jaeger proved to be a quick
study
or as Ridley observed he never studied
engineering but he blots the stuff up as
fast as it's poured after four days of
schooling Yeager was ready for the first
of three unpowered familiar ization
flights August 6th he dropped away from
the b-29 at 26,000 feet and to
everyone's surprise almost immediately
performed a series of slow rolls
that's a fighter pilot that's me you
know that's where I was trained and
upside down and I said I'm making
difference a fighter pilot that's that's
where you live you know and I just want
to see what the airplanes roll like if
it was beautiful god what a neat
airplane to fly during his third flight
he actually engaged Bob Hoover in a mock
dogfight well Bob is always doing
something to keep you alert as he puts
it and it you know he's mischievous in
an airplane you got to watch yourself
around
he's always jumping and after to glide
flights and setting out there letting
and making passes at me
then I went broke into him when he made
it past that man and we got this left
bear on the way down and well I don't
have any power and he's got he's got
power but the ax went pretty neat
airplane too pretty light and pretty
turns pretty good I could I could stay
with him till you know we looked down
and I said man I
roll this thing out and start thinking
about landing members of the NACA
contingent were dismayed and more than a
little impressed by such annex test
pilot herb louver reported this guy
Yeager's pretty much of a wild one but
believe he'll be good on first drop he
did a couple of rolls right after
leaving the b-29 on third flight he did
a to turn spin but still believe you'll
be good he's given us a good story of
his three flights on the morning of 29
August Yeager crawled back into the bomb
bay of the b-29 and descended to the
cockpit of the x1 fired with his first
powered flight
this was also supposed to be a
familiarization flight and Colonel Boyd
had issued strict orders he was not to
exceed 0.8 to Mach the speed already
cleared by Bell
following launch at 21,000 feet he
followed the flight plan as he ignited
and then shut down each of the rocket
chambers in sequence he then climbed
upward 0.7 Mach until he leveled off at
45,000 feet then all of a sudden the
fighter jock once more took over and
Jaeger douve toward the base he was my
understanding you know at least I felt
that if I can I'll fly the airplane fast
as I think it feels good though
you know that maybe that's right maybe
there isn't but anyway when I came down
across the field and fired off all four
chambers pull the airplane up and did a
roll man that thing was really smoking
out when I got up 85 mock them well it
felt good going through a 3/8 for it 85
and that's where where I raked it off
and two raked the Rockets off and came
on down afterwards little boy fired a
rocket of his own well the old man
bounced right back at us with a pretty
hot letter you reply by endorsement as
to why you exceeded 80 to Mach number
well really and I sat down and he he
wouldn't help me answer it he said you
flew it you answered and that's okay and
I just try to Slough it over that I
thought the airplane felt good enough to
go to 85 and that was the end if the old
man never said anything yet but there'd
be no more breaches of test discipline
on his very next flight Yeager
accelerated all the way out to point
eight nine Mach and began to encounter
buffeting accompanied by a nose down
trim change and right wing heaviness two
flights later at point nine mark the x1
began to nose up and the buffeting
became severe he was now flying in a
region where no man and flow
before in early October
yet 0.94 mom most flight data analysis
revealed that aircraft trim had once
again reverse nose-down this had Walt
Williams and the NACA engineers worried
the urge caution as Yeager approached
higher speeds because the x1 by well
depart and controlled flight at this
point however he remained confident Jack
and I talked about this I thought I
could handle it here but I'd never
worried me one bit and Jack I said if
this thing you know begin I can fly
that's the way I felt and they didn't
bother us but it bothered the NACA guys
quite a bit his confidence plummeted
however during his eight powered flight
on 10 October when as his Mach meter
indicated the speed of 0.94 Mach at
40,000 feet got tried turned the
airplane and nothing happened controls
became very sloppy and I didn't
understand really what was happening
because it's a strange feeling when
nothing responds to what you're doing
and so I react off the the rockets and
jettison fuel and came on down and and
got the jacket I said man we got a
serious problem when they reviewed the
data they realized what had happened
we saw the shockwave which had formed on
the fixed part of the horizontal
stabilizer as well as on the wing at
about 88 when we got back to 9 for the
shockwave was laying down and moving
back on the air fall and was at the
hinge point of the elevator and when
this occurred behind that shockwave the
elevator had no effectiveness and we
lost the effectiveness and that's where
then Ridley's brain came in Ridley's got
figured out you know we've got a
capability of moving the horizontal
stabilizer and if we can get this thing
to working we've never used it before
you think you're good enough to fly with
with a crude method like it's trimmable
horizontal stabilizer he said I think
you can control this airplane to more
you
you
you
you
what were your feelings on that
particular day at that time you know
after the after on the way down when I
jettisoned the rest of fuel and and
spilled the domes I really and I knew
we'd gotten above Mach 1 I think my
feeling was that this program is
finished I get on with the rest of them
that's that's it was one of many you
know and it didn't mean anything as as
people said later on in life I didn't
realize what it meant to the Air Force
all I know is is that I had a feeling of
accomplishment that I'd done what
you
you
