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Summary

Summary

The pilot was conducting a flight to land three passengers onto the top of Mount Sonder. Prior to making an approach to the cleared area he carried out an engine power check which confirmed that the engine was developing sufficient power to accomplish a landing at the high altitude. The pilot then carried out an inspection of the landing area, and completed all four legs of the circuit. While turning onto final approach for landing he noticed a rapid reduction of the manifold pressure indication from 26"hg to 20"hg, accompanied by a loss of engine power. The pilot was unable to continue to the intended landing area, and was committed to a landing on the sloping, rocky mountain side. As the pilot reduced the helicopter's forward speed prior to landing the tail rotor struck a rock, causing a yaw. The pilot immediately closed the throttle and the helicopter came to a stop facing up the slope suffering substantial damage to the landing skids, and separation of the tail rotor blades. No faults or malfunctions were found with the engine which may have contributed to the loss of power. An inspection of the turbocharger revealed slight scuffing of the turbine wheel, but the assembly spun freely. The density controller and wastegate were removed for overhaul, obvious problems with these units being difficult to detect. The reason for the loss of engine power could not be determined.
 
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