Robinson R44 N827JE accident near Sardis, Georgia

Probable cause

Fatigue failure of the fasteners on the engine crankshaft, which resulted in a partial loss of engine power and a subsequent forced landing.

NTSB analysis

The helicopter was about 100 ft above ground level during an aerial application fight when the engine experienced a partial loss of power. The pilot performed an autorotation and the helicopter impacted trees and terrain.

Postaccident examination of the engine revealed that the crankshaft idler gear flange, which should have been secured to the left half of the crankcase by a bolt and stud, had separated from its mounting location. Worn fragments of the bolt and stud were recovered from the oil sump. Metallurgical examination of the fasteners revealed that they failed due to rotating bending fatigue, which allowed the crankshaft idler gear to disengage and resulted in a loss of engine power. A review of maintenance records revealed that the engine had been in service for about 20 years and 1,900 operating hours since its last major overhaul, which is 8 years and 400 hours beyond the manufacturer recommended time between overhauls.

Text from the NTSB. Open the NTSB docket for ERA19LA273 for the full record.