Cessna A185F N185KB accident near White Mountain, Alaska

Probable cause

A partial loss of engine power for reasons that could not be determined because postaccident examination of the engine revealed no mechanical malfunctions or failures that would have precluded normal operation.

NTSB analysis

The private pilot was conducting a cross-country flight when he demonstrated a momentary zero-G maneuver, shortly after which the engine lost partial power. The pilot was unable to restore engine power and subsequently conducted a forced landing to tundra covered terrain, during which the airplane nosed over, resulting in substantial damage.

Postaccident examination of the airframe and engine revealed no anomalies that would have precluded normal operation; however, one engine exhaust valve exhibited signatures consistent with uneven excessive heat exposure, but no mechanical failure of the valve, therefore would not have resulted in a loss of power. It is unlikely that a momentary zero G maneuver would result in a partial power loss that could not be restored.

Text from the NTSB. Open the NTSB docket for ANC18LA059 for the full record.