NTSB Identification: LAX97LA120.
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Accident occurred Tuesday, March 11, 1997 in PACIFIC OCEAN
Probable Cause Approval Date: 10/14/1997
Aircraft: McDonnell Douglas MD 369HS, registration: N95MS
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The helicopter departed from a fishing vessel and lost partial engine power. The pilot stated he heard noise from the engine sounding like a compressor stall. The pilot regained power and attempted to return to the ship. On short final approach the helicopter lost power again and the pilot ditched the aircraft in the Pacific Ocean. The engine compressor section was examined and the compressor case plastic coating was found cracked with sections of the plastic missing, including the plastic sections between all of the fifth stage stator vanes. According to the engine manufacturer, loss of plastic can have an adverse effect on compressor performance. The engine manufacturer further indicated that corrosion was the most common cause of loss of the plastic coating. The missing plastic exceeded the quantity necessary to replace the compressor. The helicopter was immersed in salt water and it was not possible to determine the extent of corrosion on the compressor before the accident. The engine manufacturer specifies inspection of the compressor case should be made as necessary by the operating environment, but not to exceed every 300 hours.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

A loss of engine power due to a deteriorated compressor air seal, which resulted from inadequate maintenance inspection of the helicopter to detect corrosion in the compressor case while being operated in a marine environment.

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