NTSB Identification: SEA99LA082.
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Accident occurred Tuesday, June 08, 1999 in SOUTHBEND, WA
Probable Cause Approval Date: 11/30/2000
Aircraft: Hughes 369D, registration: N8306F
Injuries: 1 Minor.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
Just after releasing his external load, the pilot applied power in order to climb away from the release area. As he applied power, a puff of smoke came from the engine, followed immediately by a complete loss of power. The helicopter then began spinning to the left and descending rapidly. The pilot attempted an autorotation in a confined area, and the aircraft impacted the ground sufficiently hard to result in substantial damage. A teardown inspection of the engine determined that a three-inch section of the compressor impeller disc had separated, leading to total failure of the engine. Metallurgical examination of the impeller revealed that the disc failed due to the propagation of fatigue cracks that initiated in corrosion pits on the aft face of the disc. According to the metallurgist, the corrosion was due to exposure to environmental elements, and not due to repetitive cyclic operation.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The complete loss of power, due to a failure of the compressor impeller disk. Factors include the low altitude of the helicopter at the time of the power loss, and the need to autorotate in a confined area. Full narrative available
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