Accident Overview
While conducting a night visual flight rules (VFR) approach, the pilot visually identified his home base airport and initiated a descent. The airplane subsequently struck the top of a ridgeline at an elevation of 2,834 feet. The pilot was en route from a trip between two airports that he frequently traveled.
Flight History
The pilot had been receiving VFR flight following services from Air Route Traffic Control Center (ARTCC) and cancelled that service after reporting the airport in sight. Recorded radar data indicated that the airplane descended from its cruise altitude in a straight line toward the airport and the accident site.
Accident Site Examination
Investigators identified two marks along the ridgeline that were similar in dimension to the distance between the main landing gear on the airplane.
Aircraft Examination
Examination of the airframe and engine revealed no preimpact anomalies that would have precluded normal operation.
Toxicological Findings
Toxicological tests of the pilot's specimens detected two drug substances: diphenhydramine and cetirizine. The diphenhydramine level indicated usage within the past 8 hours of the accident flight. Cetirizine was found in the urine but not the blood, suggesting that the pilot more than likely ingested the drug within the previous 48 hours but not within the previous 12 hours of the accident.
Pharmacological Effects
Diphenhydramine can result in drowsiness and has measurable effects on performance of cognitive and motor tasks. Studies have shown that individuals' performance of tasks can be degraded even though they feel normal after ingesting the drug; however, in this case the extent to which the pilot may have been sedated and/or impaired is unclear. Studies of individuals taking cetirizine have not found any significant impairment from the medication.