WPR11FA426 · Enstrom 280FX

The operator was selling helicopter rides at a fly-in. After one such ride, a pilot, who was acting as a ground crewmember, measured the fuel level in the tanks with a calibrated wooden stick while the engine was running and the rotor blades were turning. He determined that about 8 gallons of fuel remained, which was sufficient for the next ride. About 9 minutes after takeoff, the engine lost power. Witnesses reported seeing the helicopter flying low when they heard the engine “sputter” or “pop.” The pilot reported that he performed an autorotation to a field; the helicopter landed hard on sloping terrain and rolled over onto its right side. Examination of the wreckage revealed that the engine lost power as a result of fuel exhaustion. Postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have prevented normal operation.

The helicopter manufacturer provided a wooden stick for pilots to dip a fuel tank during preflight to determine the total quantity of fuel available for flight. A representative of the helicopter manufacturer stated that caution must be exercised when measuring fuel quantity with a stick, because the irregular shape of each fuel tank can make it difficult to interpret the actual fuel quantity at lower levels. It is likely that the pilot who checked the fuel level before the accident flight did not accurately determine the amount of fuel in the tanks. The helicopter was equipped with a fuel gauge mounted on the instrument panel in the cockpit that would have provided the accident pilot with a direct reading of the helicopter’s fuel quantity.

The helicopter was being flown with the two cabin doors removed, an approved operation according to the rotorcraft flight manual. The helicopter left the factory with individual seat belts and shoulder restraints for three occupants. The passenger reported that someone buckled her and her son into the same lap belt; no shoulder strap was used. During postaccident examination, it was noted that the buckle half of the lap belt for the center seat had been removed. The center seat single-strap shoulder harness was found attached to the buckle half of the right seat lap belt. The right seat Y-type shoulder harness was found stowed behind the right seat back cushion. The first responders found the right seat occupant under the helicopter with his legs still in the cabin. Both passengers sustained serious injuries. It is likely that the lack of separate lap belt/shoulder harness assemblies for the two passengers increased the severity of their injuries.

Verbatim NTSB analysis and probable cause from the NTSB dataset