WPR12LA408

The pilot reported that, during a maintenance release flight, he entered a simulated autorotation to check the main rotor rpm. When the pilot retarded the throttle, the engine lost power. The pilot subsequently conducted an off-airport landing. During the landing, the main rotor blade struck the tailboom, which then separated from the airframe. During postaccident engine test runs in both the airframe and a test cell, the engine ran normally. Postaccident engine examinations revealed no anomalies that would have precluded normal operation. The reason for the loss of engine power could not be determined.

On September 9, 2012, at 1152 mountain standard time (MST), a Bell 206L-1, N5745Y, made a forced autorotation following a loss of engine power near Grand Canyon, Arizona. Papillon Grand Canyon Helicopters was operating the helicopter under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The commercial pilot and passenger were not injured. The helicopter sustained substantial damage to the tail boom when it was struck by one of the main rotor blades. The local flight departed Grand Canyon at 1131. Visual meteorological conditions prevailed, and a company flight plan had been filed. The pilot reported that during a maintenance release flight, he attempted to enter a simulated autorotation to check the main rotor rpm. The pilot stated that when he retarded the throttle the engine quit. During the off airport landing, a main rotor blade impacted the tail boom causing it to depart the airframe. The helicopter had just completed a scheduled 100-hour maintenance inspection. Following the event, the aircraft was recovered to Papillon's facility at Grand Canyon Airport. During the examination, the aircraft fuel system was inspected. There was no reported evidence of oil or fuel leakage. The airframe fuel filter was removed with clean fuel noted and what was identified as normal quantity. The aircraft fuel gage showed 300 lbs. During the post accident inspection the torque of all of the fuel lines using a torque wrench was performed. A rigging check was conducted in accordance with the Overhaul & Maintenance manual with no observed deviations. The engine was then motored, and a fuel flow (bucket) check was conducted with what was considered a normal flow rate and pattern from the engine fuel nozzle. The engine was then started, and a 30-minute ground run was conducted in an unloaded configuration (with engine-to-transmission and No. 1 tail rotor driveshaft disconnected). The engine was removed from the airframe and shipped to Aeromaritime in Mesa, Arizona, for further testing. The engine was placed into a test cell, and the engine was run twice with only minor anomalies noted. The cursory inspection of the engine and engine exterior did not reveal any evidence of mechanical failure or anomaly. The engine testing showed all test points to be within new overhaul limits for steady state, transient, governor droop and anti-ice. The engine performance results showed the engine to be approximately four percent below new overhaul engine specifications. The complete engine examination report is attached to the accident docket. The operator noted that the normal operation after maintenance would be to conduct a maintenance release flight as the accident flight was performed. The operator has modified the post maintenance procedures to include the requirement that all flights requiring a throttle manipulation shall be conducted to facilitate the availability of a hard landing surface in the event of a loss of power.