N9526Bell 47G-2A · 1954

On August 20, 2017, at 1200 eastern daylight time, a Bell 47G-2A, N9526, was substantially damaged during a hard landing at St Marys, Pennsylvania. The student pilot was not injured. The helicopter was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91 as a local, solo-instructional flight. Day, visual meteorological conditions prevailed at the time, and no flight plan was filed. The flight originated at St Marys Municipal Airport (OYM), St Marys, Pennsylvania about 1000.The pilot reported that he arrived at OYM and performed his preflight inspection. He determined that the fuel tanks contained between 25 and 30 gallons of fuel, and then he added 12 gallons before the flight. He departed the airport and flew for about 2 hours when the helicopter "ran out of fuel." He performed an autorotation to a level, grassy lot and the helicopter landed hard. He exited the helicopter and was met by first responders. The pilot reported there were no preimpact mechanical malfunctions or anomalies that would have precluded normal operation of the helicopter.

An inspector with the Federal Aviation Administration reported that the helicopter came to rest upright in a grassy lot, about 2.6 miles west of OYM. The fuselage was structurally damaged. The landing gear skids were spread and forced up, against the fuselage. The main rotor blades were bent. There was no fire.

The inspector examined the fuel system and determined that both fuel tanks were intact and undamaged. The fuel lines remained in place and there were no fuel leaks. He estimated that both fuel tanks contained 1 gallon or less of fuel, which was the unusable fuel quantity for each tank.

The pilot also reported that he used an average fuel burn for estimating his fuel status, with no adjustment for pressure, temperature, or other performance metrics.

The pilot topped off the fuel tanks prior to takeoff. Approximately two hours later, a loss of engine power was experienced. The pilot performed an autorotation to a field, however, the tail rotor contacted a 4x4 wooden post during the landing. This resulted in substantial damage to the tail boom. Inspection of the helicopter revealed the left fuel tank was empty and the right fuel tank was full. Inspection of the fuel system revealed the right tank fuel vent was completely blocked by mud dauber debris along with the remains of two mud daubers. The left fuel tank vent was partially blocked by mud dauber debris. Both tanks feed to a central line which provides fuel to the engine. In addition, the nut on the T-fitting from the left tank fuel line was found finger tight.