Pilot Debrief

Robinson R44 near Sardis, GA — 2019-09-17

Final reportERA19LA273
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Date
2019-09-17
Location
Sardis, GA, USA
Aircraft
Robinson R44
Registration
N827JE
Category
Helicopter
Highest injury
Serious
Fatalities
0
Phase of flight
Cruise

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 narrative

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.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Engine maintenance not performed within recommended overhaul time limits.

NTSB coding

Evidence available

  • Photos
  • 7 docket documents
View NTSB final reportView NTSB docket

Docket documents7

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