NTSB Identification: CHI06CA168.
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Accident occurred Friday, June 16, 2006 in Grand Forks, ND
Probable Cause Approval Date: 10/03/2006
Aircraft: Schweizer 269C, registration: N1675U
Injuries: 2 Uninjured.
NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.
The helicopter was substantially damaged when the tail rotor struck the taxiway during recovery from an intentional autorotation. The flight instructor and commercial pilot (dual student) were not injured. The flight instructor stated that the instructional flight included 180-degree autorotations, which were terminated into a hover with the addition of engine power. He reported that on the first autorotation the dual student flared high and during the recovery the rotor speed decayed requiring a landing on the taxiway. He noted that the dual student was subsequently instructed to increase engine power as collective was increased during the recovery in order to maintain rotor speed. On the second autorotation, he stated that the dual student flared lower and a "little more aggressively." He noted that as the dual student increased the collective, the rotor speed again decayed. The flight instructor stated that "as the collective continued upward the engine and rotor [speed] decreased." He "intervened on the controls and continued to increase the collective and throttle and level the aircraft, [when] the tail struck the taxiway." The flight instructor subsequently landed the helicopter after noting an airframe vibration. The flight instructor reported no malfunctions or failures prior to the accident.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The dual student's failure to maintain rotor speed during the recovery from the intentional autorotation and the flight instructor's delayed remedial action. Contributing factors were the flight crew's intentional autorotation and dual student's misjudged flare. Full narrative available
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