SEA08FA036 · Cessna 177

The pilot and passenger had been on a local area personal flight that had lasted about 1.8 hours, and were returning to the departure airport. The airplane entered the traffic pattern and as it was on the base leg, the airspeed slowed, and witnesses indicated that it appeared to be at a high angle of attack. The airplane stalled, rolled into a spin, and collided with trees and terrain. No evidence of any preimpact mechanical anomalies was discovered. Serious carburetor icing conditions at glide power existed at the time of the accident; however, whether or not the pilot encountered carburetor icing could not be determined with the available evidence. The pilot had limited experience operating at the airport, and in the accident airplane make and model. The toxicological tests were positive for brompheniramine and diphenhydramine. Brompheniramine and diphenhydramine are sedating antihistamines with adverse effects on performance, and often used to treat allergy symptoms. Although the toxicological test result levels were different between the Federal Aviation Administration laboratory and the local toxicological testing, both results were consistent with recent ingestion of a medication containing brompheniramine, which most likely impaired the pilot's judgment and performance of complex cognitive and motor tasks during the flight.

Verbatim NTSB analysis and probable cause from the NTSB dataset