AIRBUS/EUROCOPTER AS 350 B3 near Anchorage, AK — 2014-06-11
- Date
- 2014-06-11
- Location
- Anchorage, AK, USA
- Airport
- MRI
- Aircraft
- AIRBUS/EUROCOPTER AS 350 B3
- Registration
- N356EV
- Category
- Helicopter
- Highest injury
- None
- Fatalities
- 0
- Phase of flight
- Ground
Probable cause
The pilot’s improper engine start procedure, which resulted in an overspeed of the engine and main rotor drive system.
NTSB narrative
The pilot had been hired to ferry the recently-purchased turbine-powered helicopter to the new owner’s facility and to provide the second pilot, the new owner, with transition flight training while en route. Unable to start the helicopter, despite believing he was following the correct procedures, the first pilot enlisted help from another pilot and eventually started the helicopters engine. While the helicopter was operating at flight-idle, the yellow "TWT.GRIP" light illuminated on the annunciator panel, and the first pilot instructed the second pilot to slowly advance the collective-mounted throttle twist grip to the open position until the light went out. As the second pilot advanced the throttle, the engine speed immediately increased to a high rpm and the helicopter began to shake violently. It subsequently rotated about 240° to the left, sustaining substantial damage to the tail boom and main rotor drive system. Examination of the engine and full authority digital engine control (FADEC) systems revealed no preaccident mechanical failures or malfunctions with the helicopter that would have precluded normal operation. The accident pilot reported that he had extensive experience in helicopters that had two-channel FADEC systems, but did not recall how much time he had in helicopters with single-channel FADEC systems. The accident helicopter was equipped with a single-channel FADEC system, which required a different starting procedure than an engine with a two-channel FADEC. Given the absence of mechanical anomalies and the pilot’s unfamiliarity with the single-channel FADEC system, it is likely that he used the incorrect start and run-up procedure, which resulted in an inadvertent overspeed of the helicopter's engine and main rotor drive system.
Analysis
- Primary failure mode
- Human factors
- First missed decision gate
- Pilot could have verified experience with AS350 B3 before attempting to start the helicopter.
NTSB coding
Evidence available
- Photos
- 6 docket documents