Amateur-built GLASAIR III N655DB accident near Byron, California

Probable cause

The pilot's failure to maintain control of the airplane while maneuvering, which resulted in a stall and subsequent spin.

NTSB analysis

The two pilots, one of whom owned the airplane, departed for a personal flight. The airplane was equipped with dual flight controls; however, it could not be determined which pilot was manipulating the controls at the time of the accident. Witnesses located adjacent to the accident site reported that they heard a loud noise and then saw the airplane slow down and begin to spin left in a slight nose-low attitude. The witnesses further reported that the airplane continued to spin until it impacted terrain. Postaccident examination of the engine and airframe revealed no evidence of any preexisting mechanical anomalies that would have precluded normal operation. Wreckage and impact signatures were consistent with a flat-spin, slightly nose-low impact with terrain.

Postmortem toxicology tests for the left seat pilot/owner were positive for doxylamine (an antihistamine used in over-the-counter sleep aids and cough medicines) and methamphetamine (a central nervous system stimulant). Because the amount of doxylamine in his system at the time of the crash was below the therapeutic limit, its direct effects on the left-seat pilot's performance at the time of the crash could not be determined. Although methamphetamine was present in the left-seat pilot's blood, the amount was below the calibration limit of the toxicology tests. However, both methamphetamine and its metabolite (amphetamine) were present in his urine. Regardless, no direct correlation exists between the concentration of drug in the blood and the user's symptoms. Although it is unlikely that the left-seat pilot was actively euphoric at the time of the flight, he was likely in the late phase of symptoms or in the withdrawal phase(during which concentrations of the drug may be undetectable), which would have been impairing. However, as noted, it could not be determined which pilot was manipulating the controls at the time of the accident; therefore, the impact of the left-seat pilot's drug impairment on the flight could also not be determined.

Text from the NTSB. Open the NTSB docket for WPR13FA022 for the full record.