Hughes 369 N765KV accident near Dennis, West Virginia

Probable cause

The unporting of fuel due to the helicopter's nose-up attitude during long line operations, which resulted in fuel starvation and a total loss of engine power.

NTSB analysis

The commercial pilot was conducting long line operations in the helicopter, and he was flying it in an aft or left attitude with a higher nose-up attitude than normal flight to compensate for the load's drag. He then transitioned the helicopter to a 100-ft hover over a landing zone, and shortly thereafter, the helicopter experienced a total loss of engine power. Subsequently, the pilot initiated an autorotation, and during the landing, a main rotor blade contacted and severed the tailboom.

Postaccident wreckage examination, which included a successful test-run of the engine, did not reveal evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. However, when the helicopter was positioned nose up with the remaining fuel onboard (about 7 gallons in each tank), the low fuel light illuminated. The two fuel tanks were connected by an interconnect passage, and each tank had an internal baffle. The fuel pickup was located in the right front portion of the left fuel tank. Given that the low fuel light illuminated when the helicopter was positioned nose up, it is likely that the helicopter's nose-up attitude during the long line operation led to the unporting of the remaining fuel, which resulted in fuel starvation.

The operator's risk assessment form required that pilots land the helicopter with at least about 14.7 gallons of fuel remaining for long line operations. After the accident, the operator amended its risk assessment form to require the same fuel requirement as side pull operations (about 37 gallons of fuel remaining upon landing) for long line operations.

Text from the NTSB. Open the NTSB docket for ERA17LA209 for the full record.