What happened
The pilot performed an unplanned stop at the airport to attend to a sick passenger. Approximately 30 minutes later, the flight departed again. Following takeoff, the aircraft was observed entering a right crosswind turn, at which point it abruptly rolled and pitched downward. The aircraft reportedly maintained a nose-down attitude until it collided with terrain, resulting in fatalities.
At the time of the event, the density altitude at the airport was computed to be 6572 feet. The NOAA Airport/Facility Directory noted that unusual air currents could exist in the vicinity of the airport. Additionally, runway 05-23 featured a variable gradient, with terrain at the departure end of runway 05 dropping and then rising.
The investigation
Investigators found no evidence of preimpact mechanical failure. However, the aircraft had undergone several modifications: the original fabric covering had been replaced with metal, the engine had been derated from 160 to 150 horsepower, and the propeller had been repitched. Due to impact and ground fire damage, the specific blade pitch angles could not be measured.
Determinations regarding the takeoff gross weight were not possible, and it was not determined if the pilot had leaned the mixture for takeoff in the high density altitude conditions.