Accident Details
A commercial pilot and a passenger departed on a local flight in a twin-engine airplane from a private grass runway. According to a witness, the pilot took off and departed the area for about 10 minutes before returning to the airport. The pilot then performed a low pass over the runway, entered a steep climb followed by a roll. The airplane subsequently entered a nose-low descent, briefly leveled off in an upright attitude, then disappeared behind trees and impacted terrain.
Toxicological Findings
Toxicology testing of the pilot revealed the presence of ethanol: 0.185 gm/dl in urine and 0.210 gm/dl in cavity blood. Federal Aviation Administration regulations prohibit any person from acting as a crewmember with 0.040 gm/dl or more ethanol in the blood. While the identified ethanol may have come from sources other than ingestion, such as postmortem production, the possibility that some ethanol came from ingestion and that the pilot was impaired by ethanol during the accident flight could not be ruled out.
Toxicology also identified diphenhydramine in cavity blood at 0.122 µg/ml, which is within or above the therapeutic range of 0.0250 to 0.1120 µg/ml. Diphenhydramine is a sedating antihistamine that causes more sedation than other antihistamines; it is used as a sleep aid. The pilot had been diagnosed with memory loss about 8 months before the accident, and it appeared he had some degree of mild cognitive impairment.
Probable Cause
The probable cause of the accident was the pilot's decision to attempt a low-altitude aerobatic maneuver in a non-aerobatic airplane, and his subsequent failure to maintain control of the airplane during the maneuver. Contributing to the accident was the pilot's impairment by the effects of diphenhydramine use and his underlying mild cognitive impairment.