NTSB Identification: SEA06LA096.
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Accident occurred Monday, May 15, 2006 in Boise, ID
Probable Cause Approval Date: 10/03/2006
Aircraft: Schweizer 269C, registration: N2096W
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

During an instructional flight, in which a practice autorotation was to be demonstrated, the instructor pilot instructed the student to reduce the throttle to idle to simulate an engine failure at altitude. During the course of the maneuver and after the throttle had been reduced to idle the instructor became aware that the engine had failed. An autorotation was completed to the ground into the wind to a grass field with a slight up slope, which resulted in the helicopter sliding backwards approximately 15 feet before the tail boom, which flexed up was impacted by the main rotor. The helicopter suffered damage to the tail boom, all three main rotor blades, and the tail rotor drive shaft. A subsequent engine run, which was overseen by two FAA inspectors, revealed no anomalies which would have precluded normal operations. The inspectors did note that while the idle rpm and idle mixture were adjusted poorly for altitude and temperature, this did not result in the loss of engine power; the instructor pilot's failure to follow the cautions in the helicopter's flight manual did result in the loss of power.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The reduction of the throttle to idle at a high density altitude during a practice autorotation, which resulted in the engine stoppage. Factors contributing to the accident included the instructor pilot's improper planning by not adhering to the flight manual's warning to avoid reducing the throttle to the idle position at high density altitudes, and the uneven terrain.

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