Bell 47G N9526 accident near St Marys, Pennsylvania

Probable cause

The student pilot's inadequate prefight planning and en route fuel management, which resulted in fuel exhaustion and a total loss of engine power.

NTSB analysis

The student pilot stated that he departed in the helicopter with 37 to 42 gallons of fuel on board; however, he had only used an average fuel burn for his endurance estimates and did not make adjustments for pressure, temperature, or other performance metrics. He indicated that, about 2 hours into the flight, the helicopter "ran out of fuel." He performed an autorotation to a grassy lot and the helicopter landed hard, which resulted in structural damage. Examination of the wreckage revealed that the fuel system was intact, that both fuel tanks were undamaged, and that each tank contained about 1 gallon or less of fuel, which was consistent with the unusable fuel quantity for each tank. The student pilot reported that there were no preimpact mechanical malfunctions or failures that would have precluded normal operation of the helicopter. Thus, because the student did not account for the pressure, temperature, and other performance metrics for his preflight calculations or in-flight fuel monitoring, he did not have sufficient fuel on board to complete the flight.

Text from the NTSB. Open the NTSB docket for ERA17LA285 for the full record.