A Lockheed Martin test pilot died in an F-22 Raptor crash on 25 March because he lost control of the aircraft while struggling to maintain consciousness after performing a high-g maneouvre, the US Air Force announced on 31 July.
The pilot, 49-year-old David Cooley, was killed instantly when he ejected at 1,188m (3,900ft), or only 1.49 seconds before the Lockheed-made jet struck the ground digging a 6.1m crater, according to the accident investigation board's (AIB) report.
Cooley ejected with the Raptor still in a steep dive at Mach 1.3. At that speed, the F-22 exceeded the survivable limit by about 165kts for the advanced concept ejection seat (ACES) II, the report said.
While gathering data for a captive carriage test of an undisclosed weapon, Cooley performed the same high-g maneouvre three times in a row. Upon the third manoeuvre, Cooley experienced a physiological reaction known as "almost g-induced loss of consciousness" or A-LOC.
Cooley appeared to remain conscious throughout the flight, but during four critical seconds he lost the ability pull out of a high-g dive.
By the time Cooley recovered from A-LOC, the aircraft was in an extremely steep, supersonic dive and at 4,267m mean sea level.
"Within seconds, he found himself in an unrecoverable aircraft attitude," wrote Maj Gen David Eidsaune, the AIB president.
The USAF investigation also determined that the F-22 and all of its systems had been maintained properly and were not factors in the crash.