NTSB Identification: ANC11IA059
Nonscheduled 14 CFR Part 135: Air Taxi & Commuter
Incident occurred Monday, July 04, 2011 in McGrath, AK
Probable Cause Approval Date: 06/28/2012
Aircraft: HUGHES 500D, registration: N315SH
Injuries: 3 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
The pilot reported that during a descent, the helicopter's engine sound changed abruptly and was immediately followed by the engine-out audio horn, and a red engine-out annunciator light. She entered an emergency autorotation, and then selected a mostly open area that contained some trees as an emergency landing site. During the emergency landing, the main rotor blades struck several small trees as the helicopter touched down on the uneven, tundra-covered terrain. A postincident inspection revealed a fatigue fracture in the engine Pc line that provided compressed air to operate the engine governor and fuel control units. The Pc line met the metallurgical material specifications, but there was a bend in a normally straight portion of the line, which would have placed stress on the Pc line when installed. The additional stress likely resulted in the eventual fatigue failure of the line. It could not be determined how or when the bend occurred.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: A fatigue fracture of the governor-to-fuel control Pc line, which resulted in a partial loss of engine power. Full narrative available
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