Bell 206B accident near Warrenton, Virginia, August 7, 2007

The NTSB's narrative final · quoted from the NTSB record

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 complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.