Bell 47D1 N202CH accident near Myerstown, Pennsylvania

Probable cause

A total loss of engine power for reasons that could not be determined because examination of the engine revealed no mechanical anomalies that would have precluded normal operation.

NTSB analysis

The flight instructor reported that she was providing a flight review to the pilot and was demonstrating an autorotation that would terminate with power. She entered the maneuver about 1,500 ft above ground level (agl) by reducing the throttle to idle and lowering the collective to the "full-down" position. The carburetor heat was off. The instructor stabilized the approach at 45 mph but noted that the engine's idle speed was about 100 rpm higher than normal. The instructor was not satisfied with the needle split between the engine and rotor rpm, so she advanced the throttle to the "full-open" position. However, the engine did not respond. The instructor entered a flare about 50 ft agl, and the helicopter impacted the ground with little-to-no forward speed, bounced, and then rolled over to the left. The pilot confirmed that the throttle was full open and that there was no engine power.

Postaccident examination of the helicopter and engine revealed no preimpact mechanical anomalies that would have precluded normal operation. Weather conditions at the time of the accident were not conducive to the accumulation of carburetor icing. The reason for the loss of engine power could not be determined.

Text from the NTSB. Open the NTSB docket for ERA16LA167 for the full record.