Event Description
During cruise flight, the airplane experienced an in-flight loss of control. The pilot initially reported encountering turbulence at 9,500 feet and observed damage on the upper surface of both wings. However, data downloaded from the flight displays after the event indicated a different sequence of events. The airplane climbed to 15,400 feet above mean sea level (msl), which corresponded to a density altitude of nearly 17,500 feet—the maximum operating altitude for the airplane. Subsequently, the airplane slowed, stalled, and began a rapid descent, losing approximately 13,000 feet of altitude in about 40 seconds before recovery.
Analysis of Pilot Actions
During the recovery, the airplane experienced an average vertical loading of more than 4 Gs for over 20 seconds. Such loading would likely have resulted in G-induced loss of consciousness (G-LOC) or near-loss of consciousness. The pilot did not recall a significant loss of altitude or loss of control; his apparent failure to accurately recall the events is likely a result of confusion associated with hypoxia, followed by the confusion and amnesia associated with G-LOC or near G-LOC. The pilot confirmed that neither he nor his passengers used supplemental oxygen during the flight. It remains unclear why the pilot chose to increase his altitude beyond 12,500 feet msl, above which oxygen use would have been required after 30 minutes. Regardless, he continued climbing above 14,000 feet msl, an altitude at which oxygen use would have been required by the pilot regardless of time spent at that altitude, and subsequently above 15,000 feet, where oxygen use would have been required by all occupants.
Aircraft Examination
Examination of the airplane found no evidence of mechanical failure or malfunctions that would have prevented normal operation.