Accident Details
A private pilot, who owned the airplane, and a flight instructor were conducting a recurrent training flight. Radar data indicated that after takeoff, the airplane climbed to approximately 5,000 feet above ground level. About five minutes into the flight, the airplane performed a left 360° turn followed by a right 360° turn, then continued in level flight for about two minutes while slowing to a groundspeed of approximately 90 knots. This pattern was suggestive of airwork leading to slow flight or stall maneuvers. Subsequently, the airplane entered a steep bank and struck the ground in a nose-low attitude.
Investigation Findings
Postaccident examination revealed that both engines and propellers showed evidence of operation at the time of impact. No mechanical anomalies were found that would have precluded normal operation of the airframe or engines. The investigation was unable to identify any mechanical cause for the loss of control.
Toxicology Results
The flight instructor had a history of obstructive sleep apnea; however, the investigation could not determine how well this condition was controlled, whether he experienced symptoms, or if it contributed to the accident. Toxicology testing detected low levels of ethanol in specimens from both pilots, but it is likely that some or all of the ethanol resulted from postmortem production, and alcohol impairment was unlikely to have contributed. Testing also detected tetrahydrocannabinol (THC), the primary psychoactive compound of marijuana, and its metabolite THCCOOH in specimens from comingled remains. The investigation could not reliably determine which pilot had used the impairing illicit drug, and it is not possible to assess impairment from tissue specimens. Therefore, the investigation could not determine whether THC impaired either pilot or if it may have contributed to the accident.
Probable Cause
The official probable cause of the accident was a loss of control while maneuvering for reasons that could not be determined because postaccident examination did not reveal any mechanical malfunctions or anomalies with the airplane.