Robinson R22 N209KR accident near Kailua-Kona, Hawaii

Probable cause

A loss of engine power while maneuvering for reasons that could not be determined because postaccident examination of the engine did not reveal any anomalies that would have precluded normal operation.

NTSB analysis

While the student pilot was maneuvering for a practice off-field landing, the flight instructor observed that it was starting to drizzle, so he instructed the student to apply carburetor heat, which he did. As the student was continuing to maneuver for the approach to landing, the instructor detected a loss of engine power. The flight instructor immediately took control of the helicopter, rolled the throttle off and on to recover the loss of rotor rpm, and subsequently instructed the student to try to restart the engine while he set up an emergency landing. The student attempted three engine restarts, each of which was unsuccessful. The flight instructor then performed an emergency autorotation to upsloping terrain, which resulted in a hard landing and substantial damage to the helicopter. The instructor stated that the engine was running at idle after the landing. A postaccident examination of the engine and a subsequent engine run revealed no operational difficulties that would have precluded normal operation. The reason for the loss of engine power could not be determined.

Text from the NTSB. Open the NTSB docket for WPR12LA195 for the full record.