Ayres S2R-G6 N70WY accident near Riverton, Wyoming

Probable cause

An engine overspeed shortly after takeoff for reasons that could not be determined because postaccident examination revealed no mechanical malfunctions or failures that would have precluded normal operation.

NTSB analysis

The pilot reported that, shortly after departure, he observed the torque and temperature gauges move to extremely high values. The engine did not respond to speed or power lever inputs; however, the pilot reported that the linkage and amount of travel of the controls felt normal. The pilot diverted to a nearby airport and, when the airplane was lined up for landing on the runway, he shut down the engine. The pilot reported that, during the final descent, the airplane encountered a downdraft and collided with a light. Subsequently, the pilot was unable to maintain the airplane on an adequate descent glidepath, and it touched down in the dirt short of the runway.

Postaccident examination of the engine revealed no mechanical anomalies that would have precluded normal operation. Examination of the fuel control unit revealed several anomalies within the unit; however, none of those anomalies would have resulted in the reported engine overspeed condition.

Text from the NTSB. Open the NTSB docket for WPR12LA256 for the full record.