How does a man live to be torn pop out of an airplane at 78,000 feet? This was the dark secret in early SR-71 testing: because the Blackbird was known to be fast and high, the margins were frequently expressed in seconds. On January 25, 1966, Lockheed test pilot Bill Weaver and reconnaissance-and-navigation systems specialist Jim Zwayer were conducting a profile intended to shave the drag at high Mach by moving the center of gravity to the rear- an operation that decreased longitudinal stability. The plane entered a medium-level, high-speed cruise, the type that had made the SR-71 a legend, until something went wrong with the inlet control system, and left the cockpit looking like a physics experiment.
Weaver later defined the shift between manageable flight to disintegration as ruthless brief. “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.”
In order to see why one failure can be irreparable, it is better to consider the inlet of the Blackbird. The inlet at Mach 3 was not a passive opening but a tightly scheduled system so that the shock waves were positioned in such a way that the engine regarded subsonic airflow. The loss of that scheduling might cause disturbances to cause the shock to jump forward- an Inlet Duct Unstart- violently yawing, rolling, and suddenly imbalanced thrust. Since, as one SR-71 pilot put it, the Mach3 inlet which was “started” supplied most of the force on that side, losing it acted rather as an engine hiccup than more like a lateral collision on the airplane. The airplane might have no choice left almost immediately in a bank, where the control authority is reduced at high level.
What came to Weaver was not, like any ejection-seat textbook-approach to escape. He never pulled levers, never parted the seat, and never took the initiative of any type whatsoever. The breakup loads and the airflow ripped him out of the cockpit and the restraints fell apart, with him in freefall at an altitude where the human body can hardly withstand without protection.
“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 suit was as much as a parachute. The pressure at such heights is so low it starts boiling the body fluids; the inflated suit that Weaver wore kept the air flowing in and out and the pressure up, which in effect served as a personal capsule giving time enough to leave the automatic sequence to its task. His stabilizing chute was thrown out, so that he tumbled but slightly in the thin air, and the main canopy was thrown open at 15,000 feet. The descent began to seem like something survivable only then.
Weaver landed on the winter landscape in the New Mexico-Colorado-Oklahoma-Texas border. He saw the parachute of Zwayer dropping down in his neighborhood, but he did not come alive he found out later Zwayer broke his neck. One of the local ranchers, Albert Mitchell, spotted the parachutes and flew a helicopter to Weaver, and took him to a hospital in Tucumcari a homemade rescue that bridged the difference between life and death.
The technical post of the accident was as fateful as the drama. Aft center-of-gravity testing was stopped, trim-drag work was shifted to aerodynamic fixes, and the inlet control system was further developed to the point of unstarts becoming a rarity with the aid of digital control. Even the SR-71 itself was more of a machine consisting of materials and heat than of speed; over 85 percent of the airframe was made of titanium alloys to withstand skin temperatures of over 500degF during continuous operation at Mach 3. However, in the situation of Weaver, titanium rescued him, but a pressurized suit, and a sequence of automatic processes that continued to operate when the airplane ceased to be an airplane saved Weaver.