American Aviation AA-1A N12YT accident near Blythe, California

Probable cause

The excessive wear of one magneto’s wiring harness, which resulted in a loss of engine power during takeoff. Contributing to the accident was the pilot’s failure to maintain airspeed following the loss of engine power, which resulted in exceedance of the critical angle of attack and a subsequent aerodynamic stall.

NTSB analysis

The pilot was departing for a personal cross-county flight. Shortly after takeoff and about 50 ft above ground level, the engine lost partial power, and the airspeed decayed. Despite the pilot attempts to gain airspeed by confirming that the throttle and mixture levers were full forward, he did not lower the airplane’s nose at the first indication of an engine power loss to maintain airspeed. As a result, the airplane’s critical angle of attack was exceeded, and the airplane subsequently stalled and struck terrain.

Review of performance data in the pilot’s operating manual for the airplane indicated that given the accident conditions, the airplane should have had the performance to adequately climb. A weather study revealed no significant weather in the immediate vicinity of the airport.

Postaccident examination of the engine revealed that the left magneto’s wiring harness had excessive wear from being twisted and zip-tied near the distributor cap. All four wires were noted to have exposed center conductors that contacted their shielding. When tested, the wires intermittently failed to conduct current and sporadically arced, which likely resulted in the loss of engine power after takeoff.

Text from the NTSB. Open the NTSB docket for WPR20LA148 for the full record.