On December 4, 2000, a Hughes 269C (registration N1097N) operated by Civic Helicopter was involved in an aviation accident near Carlsbad, CA. Investigators recorded the probable cause as: The CFI's inadequate supervision and failure to maintain control of the helicopter during a practice autorotation. A contributing factor was the student's improper in-flight planning/decision. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During an instructional flight for autorotation evaluation, the second pilot allowed main rotor rpm to decay on approach, resulting in a hard touchdown and subsequent tail boom separation by a rotor blade.
Flight Details
The flight was conducted to allow a certified flight instructor (CFI) to evaluate the skill level of another pilot and provide instruction as needed. The CFI assigned the second pilot the task of performing an autorotation to a landing. An autorotation is a maneuver used to land a helicopter safely in the event of engine failure, relying on the main rotor's inertia and airflow to maintain rpm during descent.
Accident Sequence
During the approach phase of the autorotation, the second pilot, who was manipulating the flight controls, was slightly short of the intended touchdown mark. The pilot permitted the main rotor rpm to decrease. As a result, the helicopter made a hard touchdown.
Damage
During the hard touchdown, a rotor blade chopped off the tail boom, resulting in separation of the tail boom from the helicopter.