SR-71 Disintegrates Around Pilot During Flight Test
From Aviation Week & Space Technology
By Bill Weaver
Among professional aviators, there's a well-worn saying: Flying is
simply hours of boredom punctuated by moments of stark terror. And
yet, I don't recall too many periods of boredom during my 30-year
career with Lockheed, most of which was spent as a test pilot.
By far, the most memorable flight occurred on Jan. 25, 1966. Jim
Zwayer, a Lockheed flight test reconnaissance and navigation systems
specialist, and I were evaluating those systems on an SR-71 Blackbird
test from Edwards AFB, Calif. We also were investigating procedures
designed to reduce trim drag and improve high-Mach cruise
performance. The latter involved flying with the center-of-gravity
(CG) located further aft than normal, which reduced the Blackbird's
longitudinal stability.
We took off from Edwards at 11:20 a.m. and completed the mission's
first leg without incident. After refueling from a KC-135 tanker, we
turned eastbound, accelerated to a Mach 3.2-cruise speed and climbed
to 78,000 ft., our initial cruise-climb altitude.
Several minutes into cruise, the right engine inlet's automatic
control system malfunctioned, requiring a switch to manual control.
The SR-71's inlet configuration was automatically adjusted during
supersonic flight to decelerate air flow in the duct, slowing it to
subsonic speed before reaching the engine's face. This was
accomplished by the inlet's center-body spike translating aft, and by
modulating the inlet's forward bypass doors. Normally, these actions
were scheduled automatically as a function of Mach number,
positioning the normal shock wave (where air flow becomes subsonic)
inside the inlet to ensure optimum engine performance.
Without proper scheduling, disturbances inside the inlet could result
in the shock wave being expelled forward--a phenomenon known as an
"inlet unstart." That causes an instantaneous loss of engine thrust,
explosive banging noises and violent yawing of the aircraft--like
being in a train wreck. Unstarts were not uncommon at that time in
the SR-71's development, but a properly functioning system would
recapture the shock wave and restore normal operation.
On the planned test profile, we entered a programmed 35-deg. bank
turn to the right. An immediate unstart occurred on the right engine,
forcing the aircraft to roll further right and start to pitch up. I
jammed the control stick as far left and forward as it would go. No
response. I instantly knew we were in for a wild ride.
I attempted to tell Jim what was happening and to stay with the
airplane until we reached a lower speed and altitude. I didn't think
the chances of surviving an ejection at Mach 3.18 and 78,800 ft. were
very good. However, g-forces built up so rapidly that my words came
out garbled and unintelligible, as confirmed later by the cockpit
voice recorder.
The cumulative effects of system malfunctions, reduced longitudinal
stability, increased angle-of-attack in the turn, supersonic speed,
high altitude and other factors imposed forces on the airframe that
exceeded flight control authority and the Stability Augmentation
System's ability to restore control.
Everything seemed to unfold in slow motion. I learned later the time
from event onset to catastrophic departure from controlled flight was
only 2-3 sec. Still trying to communicate with Jim, I blacked out,
succumbing to extremely high g-forces. The SR-71 then literally
disintegrated around us.
From that point, I was just along for the ride.
My next recollection was a hazy thought that I was having a bad
dream. Maybe I'll wake up and get out of this mess, I mused.
Gradually regaining consciousness, I realized this was no dream; it
had really happened. That also was disturbing, because I could not
have survived what had just happened. Therefore, I must be dead.
Since I didn't feel bad--just a detached sense of euphoria--I decided
being dead wasn't so bad after all.
AS FULL AWARENESS took hold, I realized I was not dead, but had
somehow separated from the airplane. I had no idea how this could
have happened; I hadn't initiated an ejection. The sound of rushing
air and what sounded like straps flapping in the wind confirmed I was
falling, but I couldn't see anything. My pressure suit's face plate
had frozen over and I was staring at a layer of ice.
The pressure suit was inflated, so I knew an emergency oxygen
cylinder in the seat kit attached to my parachute harness was
functioning. It not only supplied breathing oxygen, but also
pressurized the suit, preventing my blood from boiling at extremely
high altitudes. I didn't appreciate it at the time, but the suit's
pressurization had also provided physical protection from intense
buffeting and g-forces. That inflated suit had become my own escape
capsule.
My next concern was about stability and tumbling. Air density at high
altitude is insufficient to resist a body's tumbling motions, and
centrifugal forces high enough to cause physical injury could develop
quickly. For that reason, the SR-71's parachute system was designed
to automatically deploy a small-diameter stabilizing chute shortly
after ejection and seat separation. Since I had not intentionally
activated the ejection system--and assuming all automatic functions
depended on a proper ejection sequence--it occurred to me the
stabilizing chute may not have deployed.
However, I quickly determined I was falling vertically and not
tumbling. The little chute must have deployed and was doing its job.
Next concern: the main parachute, which was designed to open
automatically at 15,000 ft. Again, I had no assurance the
automatic-opening function would work.
I couldn't ascertain my altitude because I still couldn't see through
the iced-up face plate. There was no way to know how long I had been
blacked-out, or how far I had fallen. I felt for the
manual-activation D-ring on my chute harness, but with the suit
inflated and my hands numbed by cold, I couldn't locate it. I decided
I'd better open the face plate, try to estimate my height above the
ground, then locate that "D" ring. Just as I reached for the face
plate, I felt the reassuring sudden deceleration of main-chute
deployment.
I raised the frozen face plate and discovered its uplatch was broken.
Using one hand to hold that plate up, I saw I was descending through
a clear, winter sky with unlimited visibility. I was greatly relieved
to see Jim's parachute coming down about a quarter of a mile away. I
didn't think either of us could have survived the aircraft's breakup,
so seeing Jim had also escaped lifted my spirits incredibly.
I could also see burning wreckage on the ground a few miles from
where we would land. The terrain didn't look at all inviting--a
desolate, high plateau dotted with patches of snow and no signs of
habitation.
I tried to rotate the parachute and look in other directions. But
with one hand devoted to keeping the face plate up and both hands
numb from high-altitude, subfreezing temperatures, I couldn't
manipulate the risers enough to turn. Before the breakup, we'd
started a turn in the New Mexico-Colorado-Oklahoma-Texas border
region. The SR-71 had a turning radius of about 100 mi. at that speed
and altitude, so I wasn't even sure what state we were going to land
in. But, because it was about 3:00 p.m., I was certain we would be
spending the night out here.
At about 300 ft. above the ground, I yanked the seat kit's release
handle and made sure it was still tied to me by a long lanyard.
Releasing the hea vy kit ensured I wouldn't land with it attached to
my derriere, which could break a leg or cause other injuries. I then
tried to recall what survival items were in that kit, as well as
techniques I had been taught in survival training.
Looking down, I was startled to see a fairly large animal--perhaps an
antelope--directly under me. Evidently, it was just as startled as I
was because it literally took off in a cloud of dust.
My first-ever parachute landing was pretty smooth. I landed on fairly
soft ground, managing to avoid rocks, cacti and antelopes. My chute
was still billowing in the wind, though. I struggled to collapse it
with one hand, holding the still-frozen face plate up with the other.
"Can I help you?" a voice said.
Was I hearing things? I must be hallucinating. Then I looked up and
saw a guy walking toward me, wearing a cowboy hat. A helicopter was
idling a short distance behind him. If I had been at Edwards and told
the search-and-rescue unit that I was going to bail out over the
Rogers Dry Lake at a particular time of day, a crew couldn't have
gotten to me as fast as that cowboy-pilot had.
The gentleman was Albert Mitchell, Jr., owner of a huge cattle ranch
in northeastern New Mexico. I had landed about 1.5 mi. from his ranch
house--and from a hangar for his two-place Hughes helicopter. Amazed
to see him, I replied I was having a little trouble with my chute. He
walked over and collapsed the canopy, anchoring it with several
rocks. He had seen Jim and me floating down and had radioed the New
Mexico Highway Patrol, the Air Force and the nearest hospital.
Extracting myself from the parachute harness, I discovered the source
of those flapping-strap noises heard on the way down. My seat belt
and shoulder harness were still draped around me, attached and
latched. The lap belt had been shredded on each side of my hips,
where the straps had fed through knurled adjustment rollers. The
shoulder harness had shredded in a similar manner across my back. The
ejection seat had never left the airplane; I had been ripped out of
it by the extreme forces, seat belt and shoulder harness still
fastened.
I also noted that one of the two lines that supplied oxygen to my
pressure suit had come loose, and the other was barely hanging on. If
that second line had become detached at high altitude, the deflated
pressure suit wouldn't have provided any protection. I knew an oxygen
supply was critical for breathing and suit-pressurization, but didn't
appreciate how much physical protection an inflated pressure suit
could provide. That the suit could withstand forces sufficient to
disintegrate an airplane and shred heavy nylon seat belts, yet leave
me with only a few bruises and minor whiplash was impressive. I truly
appreciated having my own little escape capsule.
After helping me with the chute, Mitchell said he'd check on Jim. He
climbed into his helicopter, flew a short distance away and returned
about 10 min. later with devastating news: Jim was dead. Apparently,
he had suffered a broken neck during the aircraft's disintegration
and was killed instantly. Mitchell said his ranch foreman would soon
arrive to watch over Jim's body until the authorities arrived.
I asked to see Jim and, after verifying there was nothing more that
could be done, agreed to let Mitchell fly me to the Tucumcari
hospital, about 60 mi. to the south.
I have vivid memories of that helicopter flight, as well. I didn't
know much about rotorcraft, but I knew a lot about "red lines," and
Mitchell kept the airspeed at or above red line all the way. The
little helicopter vibrated and shook a lot more than I thought it
should have. I tried to reassure the cowboy-pilot I was feeling OK;
there was no need to rush. But since he'd notified the hospital staff
that we were inbound, he insisted we get there as soon as possible. I
couldn't help but think how ironic it would be to have survived one
disaster only to be done in by the helicopter that had come to my
rescue.
However, we made it to the hospital safely--and quickly. Soon, I was
able to contact Lockheed's flight test office at Edwards. The test
team there had been notified initially about the loss of radio and
radar contact, then told the aircraft had been lost. They also knew
what our flight conditions had been at the time, and assumed no one
could have survived. I briefly explained what had happened,
describing in fairly accurate detail the flight conditions prior to
breakup.
The next day, our flight profile was duplicated on the SR-71 flight
simulator at Beale AFB, Calif. The outcome was identical. Steps were
immediately taken to prevent a recurrence of our accident. Testing at
a CG aft of normal limits was discontinued, and trim-drag issues were
subsequently resolved via aerodynamic means. The inlet control system
was continuously improved and, with subsequent development of the
Digital Automatic Flight and Inlet Control System, inlet unstarts
became rare.
Investigation of our accident revealed that the nose section of the
aircraft had broken off aft of the rear cockpit and crashed about 10
mi. from the main wreckage. Parts were scattered over an area
approximately 15 mi. long and 10 mi. wide. Extremely high air loads
and g-forces, both positive and negative, had literally ripped Jim
and me from the airplane. Unbelievably good luck is the only
explanation for my escaping relatively unscathed from that
disintegrating aircraft
Two weeks after the accident, I was back in an SR-71, flying the
first sortie on a brand-new bird at Lockheed's Palmdale, Calif.,
assembly and test facility. It was my first flight since the
accident, so a flight test engineer in the back seat was probably a
little apprehensive about my state of mind and confidence. As we
roared down the runway and lifted off, I heard an anxious voice over
the intercom.
"Bill! Bill! Are you there?"
"Yeah, George. What's the matter?"
"Thank God! I thought you might have left." The rear cockpit of the
SR-71 has no forward visibility--only a small window on each
side--and George couldn't see me. A big red light on the
master-warning panel in the rear cockpit had illuminated just as we
rotated, stating, "Pilot Ejected." Fortunately, the cause was a
misadjusted microswitch, not my departure.
Bill Weaver flight tested all models of the Mach-2 F-104 Starfighter
and the entire family of Mach 3+ Blackbirds--the A-12, YF-12 and
SR-71. He subsequently was assigned to Lockheed's L-1011 project as
an engineering test pilot, became the company's chief pilot and
retired as Division Manager of Commercial Flying Operations. He still
flies Orbital Sciences Corp.'s L-1011, which has been modified to
carry a Pegasus satellite-launch vehicle (AW&ST Aug. 25, 2003, p.
56). An FAA Designated Engineering Representative Flight Test Pilot,
he's also involved in various aircraft-modification projects,
conducting certification flight tests.