Bell Helicopter Textron 206L-1 N2018R accident near Payson, Arizona

Probable cause

A partial loss of engine power due to an overtemperature event that thermally damaged the turbine blades and vanes, which resulted in a hard landing.

NTSB analysis

The pilot reported that the engine lost power while the helicopter was in cruise flight about 1,500 ft above ground level. He subsequently entered an autorotation and performed an emergency off-airport landing. During the descent, he maneuvered the helicopter to avoid obstacles; the helicopter subsequently landed hard, and the tailboom separated.

Examination of the engine revealed that the outer portion of the engine's first-stage turbine blades and three vanes from the first-stage nozzle were thermally damaged. The turbine blades' microstructure exhibited signatures consistent with an engine overtemperature event; however, it could not be determined when the overtemperature damage occurred. The postaccident examination of the airframe and engine revealed no additional evidence of a mechanical malfunction that would have precluded normal operation.

Weight and balance calculations revealed that, when the helicopter departed, it was over its allowable gross takeoff weight but that it was under its allowable gross operational weight at the time of the engine power loss.

Text from the NTSB. Open the NTSB docket for WPR13LA390 for the full record.