NTSB Identification: NYC07LA188
14 CFR Part 91: General Aviation
Accident occurred Tuesday, August 07, 2007 in Warrenton, VA
Probable Cause Approval Date: 05/12/2009
Aircraft: BELL 206B, registration: N3202D
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 a training flight in a Bell 206B helicopter, the certified flight instructor was demonstrating a rapid deceleration maneuver to a grass area at the airport. The helicopter touched down hard, buckling the tail boom downward. The subsequent misalignment fractured the tail rotor drive shaft into several sections, and deflected the tail boom to the right. Examination of the fractured tail boom and tail rotor segments revealed overload fractures consistent with a hard, vertical landing, near 70 percent main rotor rpm. Even though the pilots were not performing an autorotation, the conditions at touchdown were similar to procedures outlined in the Bell 206 Rotorcraft Flight Manual, which instructed pilots to adjust collective pitch during an autorotation maneuver as required to maintain 90 to 107 percent rpm. It was also recommended that a level touchdown be made prior to passing through 70 percent rotor rpm. The manufacturer had warned operators that the tail boom and aft fuselage could be damaged if during an autorotation landing the main rotor rpm was allowed to decay below 70 percent rpm.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The flight instructor's failure to maintain adequate rotor rpm during touchdown. Full narrative available
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