Bell 206L-3 N32041 accident near GM

Probable cause

The loss of engine power due to an engine compressor stall as a result of ingesting methane gas during takeoff.

NTSB analysis

After the helicopter was refueled with the engine running, the pilot departed from an offshore oil platform. The pilot and the two passengers reported a loud bang just after the turboshaft-powered helicopter lifted off. The pilot immediately lowered the helicopter’s nose and entered an autorotation to the water below; as the helicopter descended, the pilot activated the helicopter’s float system. The floats inflated; however, the helicopter impacted the water and rolled inverted. Examination of the helicopter’s engine found no preaccident mechanical malfunctions or failures that would have precluded normal operation. A review of data downloaded from the engine’s data monitoring system revealed a “spike” in the engine’s turbine outlet temperature and torque readings. The oil platform was venting un-ignited methane gas at the time the helicopter departed the platform. It is likely that the helicopter’s engine experienced a compressor stall due to ingesting the methane gas, and the pilot immediately reacted by initiating an autorotation.

Text from the NTSB. Open the NTSB docket for CEN11LA252 for the full record.