Pilot Debrief

BELL 206 L4 near Dewey, AZ — 2015-06-02

Final reportWPR15LA177
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Date
2015-06-02
Location
Dewey, AZ, USA
Aircraft
BELL 206 L4
Registration
N73AW
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
Cruise

Probable cause

A total loss of engine power due to the failure of the No. 2 bearing, which resulted from a fractured separator.

NTSB narrative

The commercial pilot was conducting a cross-country ferry flight. He reported that the engine chip detector caution light briefly illuminated while the helicopter was in cruise flight about 750 ft above ground level. The pilot chose to make a precautionary landing and initiated a descent. During the descent, the detector light illuminated again, followed shortly thereafter by a "loud bang" and the engine losing power. The pilot initiated an autorotation emergency landing. During the landing sequence, the main rotor blades struck the tailboom. Examination of the engine revealed that the No. 2 bearing separator had fractured through both rails at the forward and aft sides of the bearing. The ball bearings were retained in the separator; however, half of them exhibited damage consistent with smearing and material transfer between the raceway and balls, which resulted in the failure of the No. 2 bearing and the subsequent engine power loss.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have opted to land after first caution light illumination.

NTSB coding

Evidence available

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

Docket documents8

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