Bell OH-58A N283MP accident near Jefferson City, Missouri

Probable cause

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

NTSB analysis

The pilot receiving instruction reported that the purpose of the flight was to remain in the airport traffic pattern while practicing autorotation landings. He stated that, after about 45 minutes of flight training, the engine began to fluctuate between full and half power while the helicopter was climbing on a downwind leg. The helicopter also experienced an uncommanded yaw with each engine power fluctuation. The flight instructor took control of the helicopter and entered a straight-in autorotation toward a nearby field. The helicopter touched down with a slight forward ground run, during which the left skid dug into the soft soil, which caused the helicopter to rotate 180 degrees before it stopped. The main rotor blades severed the tail boom from the fuselage during the forced landing.

A postaccident examination revealed no airframe anomalies that would have prevented normal operation of the helicopter. During a test run, the accident engine demonstrated normal operation at all power settings and was capable of producing maximum takeoff horsepower. Uncontaminated fuel was found onboard the helicopter. The reason for the reported loss of engine power could not be determined.

Text from the NTSB. Open the NTSB docket for CEN14TA020 for the full record.