Piper PA 14 N91449 accident near Susanville, California

Probable cause

The pilot’s decision to conduct a steep departure at a high-density altitude and the exceedance of the airplane’s critical angle of attack during a climb, which resulted in an accelerated stall and subsequent loss of control. Contributing to the accident was the installation of a high pitch angle propeller that was not designed for the installed engine which likely degraded the airplane’s performance.

NTSB analysis

The accident airplane’s takeoff run from a dirt runway was not observed. However, while taxiing his airplane toward the airport’s only asphalt runway, a friend of the accident pilot and pilot-rated passenger observed the accident airplane in a steep left turn about 350 ft above the runway. The airplane then transitioned into a nose-down dive, consistent with a loss of control following an accelerated stall, which resulted in impact with terrain.

Examination of the wreckage revealed no preimpact mechanical anomalies with the engine or airframe that could have precluded normal operation. An experimental propeller that was designed for a more powerful engine was attached to the engine at the time of the accident. The propeller’s blade angle was excessive for the engine-propeller configuration, which would have slowed the propeller. This, in turn, would have led to an overall decrease in performance, further degrading the airplane’s ability to climb as the density altitude was nearly double the field elevation of the departure airport when the accident occurred. Additionally, the airplane may have been over its gross weight; however, this could not be determined as the fuel quantities at the time of departure were unknown. The airplane had vortex generators installed, which may have slightly reduced the airplane’s stall speed, but this performance improvement was not guaranteed as stated by the manufacturer.

The investigation was unable to determine whether the pilot performed any preflight performance computations, which would have showed that the airplane required 3,750 ft of runway surface to clear a 50 ft obstacle given the temperature and density altitude. Although there was no need to clear a 50 ft obstacle that day, and this performance information was for a lower performance engine than the one he had installed, a conscientious pilot would have exercised caution during the takeoff attempt after reviewing this performance data. However, the witness observation of the airplane altitude is consistent with the pilot performing a high rate of climb departure after takeoff.

The pilot’s toxicology testing demonstrated previous use of cocaine, but no active cocaine in his system at the time of the event. The investigation was unable to determine if he had any impairment from cocaine withdrawal at or near the time of the accident and whether his cocaine use contributed to the accident circumstances due to a lack of available evidence.

Text from the NTSB. Open the NTSB docket for WPR20LA270 for the full record.