Event Overview
On September 9, 2012, at 1152 mountain standard time, a Bell 206L-1 helicopter (registration N5745Y) operated by Papillon Grand Canyon Helicopters made a forced autorotation after a loss of engine power near Grand Canyon, Arizona. The flight was conducted under 14 Code of Federal Regulations 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 had departed Grand Canyon at 1131. Visual meteorological conditions prevailed, and a company flight plan had been filed.
Pilot Report
The pilot reported that during a maintenance release flight, he attempted to enter a simulated autorotation to check the main rotor rpm. When he retarded the throttle, the engine quit. During the subsequent off-airport landing, a main rotor blade impacted the tail boom, causing it to separate from the airframe.
Maintenance History
The helicopter had just completed a scheduled 100-hour maintenance inspection.
Post-Accident Examination
Following the event, the aircraft was recovered to Papillon's facility at Grand Canyon Airport. The fuel system was inspected; there was no reported evidence of oil or fuel leakage. The airframe fuel filter was removed, revealing clean fuel and what was identified as a normal quantity. The aircraft fuel gauge showed 300 pounds. A torque check of all fuel lines was performed using a torque wrench, and 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, showing a normal flow rate and pattern from the engine fuel nozzle. The engine was started and a 30-minute ground run was conducted in an unloaded configuration (with engine-to-transmission and No. 1 tail rotor driveshaft disconnected).
Engine Testing
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 run twice, with only minor anomalies noted. Cursory inspection of the engine and its exterior did not reveal any evidence of mechanical failure or anomaly. 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.
Operator Procedural Change
The operator noted that the normal operation after maintenance would be to conduct a maintenance release flight, as the accident flight was performed. Following the event, the operator modified post-maintenance procedures to include the requirement that all flights requiring throttle manipulation be conducted to facilitate the availability of a hard landing surface in the event of a loss of power.