On 25 January 1966, SR-71A (61-7952) was scheduled for a mission to test reconnaissance systems sensor performance and evaluate use of the navigation system as a controller for integrated sensor and aircraft management. The flight crew included Lockheed test pilot William A. Weaver and flight test reconnaissance and navigation systems specialist James T. Zwayer. The mission callsign was DUTCH 54.
Weaver and Zwayer also planned to investigate procedures designed to reduce trim drag and improve high-Mach cruise performance as a function of center-of-gravity (c.g.) position. The latter involved flying with the c.g. located further aft than normal, thus reducing the Blackbird's longitudinal stability.
Preparations began early in the morning at Edwards Air Force Base, but DUTCH 54 didn't depart until 11:20. Takeoff, climb and acceleration were normal. The aircraft configuration required excessive nose-up trim in cruise and, as a result, the Auto-Nav overshot its 35-degree bank angle during a turn. The pilot noted insufficient manual trim during subsequent turns as well.
Descent to rendezvous with the KC-135Q tanker (FATE 53) and subsequent refueling near Beatty, Nevada, were normal. DUTCH 54 then turned eastbound to begin a climb to altitude. Acceleration toward Dalhart, Texas, was uneventful until at approximately Mach 2.9 the SR-71, while in Auto-Nav, rolled into a 10-to-15-degree right bank because the right forward bypass door had opened. Weaver closed it manually and the Auto-Nav rolled the airplane back on course. Weaver continued to accelerate to Mach 3.2, at which point he noticed the compressor inlet temperature limit was being exceeded and reduced speed accordingly.
The SR-71's inlet configuration was designed to automatically adjust during supersonic flight to decelerate airflow in the duct, slowing it to subsonic speed before reaching the engine's compressor face. To accomplish this, the inlet's cone-shaped spike moved forward or aft, as required, and the inlet bypass doors opened and closed to control airflow around the engine. Normally, these actions were scheduled automatically as a function of Mach number, positioning the shock wave 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 inlet unstart that caused instantaneous loss of engine thrust, explosive banging noises and violent yawing motion.
As the airplane approached Albert, New Mexico, Weaver boosted engine fuel flow to minimize loss of altitude during the turn. While traveling at Mach 3.17 at an altitude of nearly 78,000 feet, Weaver guided the Blackbird through a 35-degree bank turn to the right.
Suddenly, a loud bang signaled an unstart on the right engine and the airplane rolled into a 60-degree right bank and pitched up. Weaver jammed the control stick to the left and as far forward as it would go, but got no response. He knew instantly that he and Zwayer would have to eject, but didn't think it would be survivable at that speed and altitude. He attempted to advise Zwayer by intercom to stay with the aircraft until they reached a lower speed and altitude, but his transmission was garbled due to the high g-forces he was experiencing.
The cumulative effects of system malfunctions, reduced longitudinal stability, increased angle-of-attack, supersonic speed and other factors imposed forces on the airframe that exceeded the Stability Augmentation System's ability to restore control, and stressed the airframe to failure. The crew was also subjected to high levels of physical stress. Several seconds after the unstart, the aircraft suddenly disintegrated and Weaver blacked out.
The airframe had failed at the main joint connecting the forward fuselage to the aft fuselage, just ahead of the wings. As the airplane's forebody rotated, the now open end behind the crew compartments faced into the Mach 3 airstream. Titanium skin panels ripped away and composite chine sections shattered. Canopies were torn from their mountings and the crew blasted out of their seats. The aft fuselage, wings, tails and engine nacelles also broke apart and debris rained down on rural New Mexico.
Weaver gradually came to a hazy awareness and thought he was having a bad dream. His next thought was that he must be dead and that it wasn't so bad. He saw only a hazy white light and felt like he was floating. Weaver soon realized he wasn't dead and that he was no longer in his airplane, but he knew he hadn't initiated the ejection sequence.
He became aware of the sounds of rushing air and straps flapping in the wind, but he still couldn't see anything because his helmet faceplate had frosted over. Weaver's pressure suit was inflated, so he knew the emergency oxygen cylinder attached to his parachute harness was functioning. It not only supplied breathing oxygen, but also pressurized the suit, preventing his blood from boiling at extremely high altitude. The suit had also provided physical protection from intense buffeting and g-forces as he had been expelled from the disintegrating Blackbird.
Although Weaver had not executed a proper ejection, a small stabilizing parachute to prevent the pilot from tumbling had apparently deployed, thus preventing injury from centrifugal forces that could build up quickly in the low-density air at high altitude. The main parachute was supposed to open automatically at 15,000 feet, but Weaver didn't know if it would. Still blinded by the frost on his faceplate, he couldn't guess his altitude. He didn't know how long he had been unconscious or how long he had been falling. He fumbled for the manual-activation D-ring on his parachute harness, but with the suit inflated and his hands numbed by cold, he couldn't locate it. In an attempt to estimate his height above the ground, Weaver reached to open his faceplate. At that instant, he felt his main parachute open. The automatic system had worked!
Weaver raised his frozen faceplate and saw he was descending through a clear sky with unlimited visibility. Spread out below were miles of open country patched with snow and sparsely populated. He was greatly relieved to see Zwayer's parachute descending about a quarter mile away.
Weaver struggled to steer the chute while using one hand to hold up his faceplate as the uplatch had apparently broken. His hands were cold and numb and he couldn't manipulate the risers enough to turn. About 300 feet above the ground, he released his survival kit. He landed on level ground and struggled to collapse his parachute with one hand while still holding the helmet faceplate up with the other.
Meanwhile, air traffic controllers who had been tracking DUTCH 54 realized that something was wrong. Radio chatter from airline pilots flying routes across eastern New Mexico provided the first clues.
"Albuquerque Center, this is American 85. Do you have anything on radar off to our right? Uh,.looks like some kind of a missile or something,.uh.airplane (unintelligible)."
"American 85, affirmative. I do have a radar-identified target."
"Uh, what was it, some kind of missile?"
"American 85, I'm afraid I can't say."
"What do you mean? It's a secret deal of some kind?"
"American 85, you're free to draw your own conclusions, sir."
"That's alright, American. TWA 12, we can't see it either."
"Well, we could see it. It's real clear out here."
"Well we can, too. I was just being facetious."
Soon, Albuquerque Center realized that their radar target was missing and DUTCH 54 wasn't responding to radio calls. The citizens of Buyeros and Albert, New Mexico, were the first to learn the fate of DUTCH 54.
Albert J. Mitchell Jr. and several ranch hands were branding colts at his ranch when they heard a noise and saw parachutes descending from the sky several minutes later. Mitchell immediately took off in his helicopter, heading for the nearest chute.
It was Weaver. Mitchell helped him collapse his chute and free him from the harness. While extracting himself from the parachute harness, Weaver discovered the source of the flapping-strap noises he heard during his descent. His shredded seatbelt and shoulder harness were draped around him, still latched. His ejection seat had never left the airplane! The extreme forces had simply ripped him out of the cockpit.
Mitchell got back in his helicopter and went to check on the other crewman. He returned about 10 minutes later with the devastating news that Zwayer was dead.
He then flew Weaver 60 miles to the hospital in Tucumcari. From there, Weaver contacted Lockheed's flight test office at Edwards and briefly explained what had happened. Air Force security personnel and accident response teams were dispatched to the crash site to begin the arduous task of clean-up and investigation.
The first security personnel arrived from Clovis Air Force Base and military aircraft began transporting personnel to Tucumcari Airport, the closest sizable airfield to the crash scene. Their three main goals were to secure the crash site, recover as much of the wreckage as possible and determine the cause of the accident.
The investigators faced a real challenge because the debris field was 15 miles long by 10 miles wide. Eventually, all major components were transported to Edwards for analysis except the drag chute and the tape from the Mission Recorder System, which were not found. For many months afterward, local ranchers collected any pieces they found on their land and stored them until they could be picked up by the Air Force. Following the investigation, the wreckage was buried at Edwards.