LAX00TA030 · Bell OH-58A

Following a loss of engine power, the helicopter slid forward on the ground and the main rotor blades severed a power pole during an autorotation to a city street. While in cruise flight at 100 knots and 600 feet above ground level, the N1 engine speed began to bleed off. The pilot modulated the throttle and attempted other corrective action. However, the N1 and N2 speeds continued to bleed off and the pilot began a right turn for a 180-degree autorotation. A vehicle moved onto the road where he planned to land. The pilot attempted to land on a traffic island, but the helicopter continued on into the power pole. Following a temporary loss of power in August, maintenance technicians had removed and replaced the fuel pump and fuel control units. The helicopter accumulated about 50 hours between this maintenance and the accident. A 50-hour inspection was completed just before this flight. All connections for the pneumatic, oil supply, and scavenge lines were secure. The oil screen was clean. Fuel was present in all the fuel lines and a vacuum check on the fuel system revealed no discrepancies. The fuel spray nozzle was sooty but clear. The electric fuel pump discharged over 1 gallon of fuel in 1 minute, and investigators pumped out a total of 30 gallons of fuel from the helicopter's fuel tank. The engine driven fuel pump filter was absent of contaminants. The airframe external fuel filter contained visible contaminants, but not enough to prevent normal engine operation. The engine and transmission chip detectors were clean. The compressor, N1 turbine, and N2 turbine turned freely when manually rotated. There were no leaks in the PG governor pressure lines. The engine was run in a test cell and tested satisfactorily through accelerations, decelerations, and horsepower checks in all parameters in accordance with the Allison overhaul manual.

Verbatim NTSB analysis and probable cause from the NTSB dataset