Incident Summary
A helicopter that had departed from a fishing vessel experienced a partial loss of engine power. The pilot reported hearing a noise from the engine that sounded like a compressor stall. After regaining power, the pilot attempted to return to the ship. However, during the short final approach, the helicopter lost power again and was ditched in the Pacific Ocean.
Investigation Findings
Examination of the engine compressor section revealed that the plastic coating on the compressor case was cracked, with sections of the plastic missing, including the plastic between all of the fifth stage stator vanes. According to the engine manufacturer, the loss of plastic can have an adverse effect on compressor performance. The manufacturer also indicated that corrosion is the most common cause of loss of the plastic coating. The missing plastic exceeded the quantity necessary to replace the compressor.
Because the helicopter was immersed in salt water, it was not possible to determine the extent of corrosion on the compressor before the accident. The engine manufacturer specifies that inspection of the compressor case should be made as necessary by the operating environment, but not to exceed every 300 hours.