Eurocopter AS 350 BA N141MK accident near Honolulu, Hawaii

Probable cause

The partial loss of engine power during landing for an undetermined reason.

NTSB analysis

The purpose of the flight was to transport a worker to an antenna located on a ridge top at an elevation of about 2,400 feet. The pilot reported that the flight to the location was uneventful and that he completed his prelanding checklist and noted nothing abnormal. Just prior to landing, there was a loss of engine power. According to the pilot, “the engine felt and sounded like it was winding down and rotor RPM was starting to bleed off.” At this point the helicopter was less than 10 feet from the landing site and was not holding altitude. The pilot maneuvered the helicopter so that it touched down and rolled over onto its right side, which prevented the helicopter from falling down the steep slope of the ridge. After the helicopter came to rest, the pilot shut down the engine. Examination of the helicopter revealed no discrepancies with the fuel system. Engine continuity was established. A pneumatic leak check was performed and leaks were identified at the temperature compensator and at the PX acceleration bellows. A test cell run of the engine was completed without tightening any of the pneumatic fittings. During the test cell run, the engine achieved maximum continuous, takeoff, and thermodynamic shaft horsepower. The engine did not surge during transient deceleration and acceleration runs, and was responsive to commanded throttle inputs. No preexisting condition was identified on the engine that would have interfered with normal operation or explain the reported loss of engine power.

Text from the NTSB. Open the NTSB docket for WPR09FA072 for the full record.