Amateur-built Backcountry Supercub N59BK accident near Casper, Wyoming

Probable cause

The seizure of two bearings in the reduction gearbox, resulting in the total loss of engine power. Contributing to the accident was a high descent rate which resulted in a hard landing.

NTSB analysis

The commercial pilot was flight testing the airplane to evaluate an experimental diesel engine reduction gearbox. During the takeoff, as the airplane climbed above 500 ft above ground level, the pilot increased engine power, but a total loss of engine power occurred shortly afterward. The pilot initiated a left descending turn to return to the runway. During the landing sequence, the airplane had a high descent rate. The airplane touched down hard, resulting in the separation of the left main landing gear axle and substantial damage to the left wing lift strut.

Postaccident examination of the engine reduction gearbox found that two propeller shaft bearings inside the reduction gearbox seized, causing the total loss of engine power.

Text from the NTSB. Open the NTSB docket for WPR19LA029 for the full record.