Background
The pilot was observed taking medication within two hours prior to departure. A witness identified one pill as Darvocet-N 100, since she took the same medication. The pilot's doctor had prescribed Talwin and Darvocet-N 100 for back pain.
Preflight and Taxi
When the pilot started the engine, it accelerated to a very high RPM, as if the throttle was too far open. During taxi for takeoff, the aircraft nearly hit a parked aircraft, exited the taxiway, and came alarmingly close to a tractor.
Flight and Communications
The flight was a local trip to a nearby airport at night. During the flight, the pilot's speech was slurred and erratic, and he could not find the destination airport. Tower personnel at the destination airport identified the aircraft using their bright radar and could clearly see the aircraft's lights. They attempted to vector the aircraft to the airport, but the pilot did not follow directions.
Accident Sequence
The aircraft impacted the ground near the edge of a flooded field while descending with the landing gear extended, approximately five miles southwest of the airport.
Post-Accident Examination
An unidentified barbiturate was found in the pilot's gastric contents. According to the source, the medicine could have caused disorientation and drowsiness. Toxicological examination of the pilot's blood was negative for drugs, alcohol, and carbon monoxide. There was insufficient urine for drug testing.