Dehavilland DHC-2T N535KT accident near Petersville, Alaska

Probable cause

An in-flight loss of thrust due to an uncommanded feathering of the propeller for reasons that could not be determined.

NTSB analysis

The pilot was conducting an air tour flight when the airplane’s propeller rpm decreased and the propeller subsequently stopped producing noticeable thrust. The pilot cycled the propeller but the propeller rpm continued to decrease.. The pilot performed a forced landing, which resulted in substantial damage to the fuselage and wings.

The pilot reported no mechanical issues with the airplane other than the loss of propeller pitch control and subsequent loss of thrust.

Postaccident examination and testing of the propeller and overspeed governors revealed that they performed within their respective manufacturer’s specifications, and no abnormalities were observed that would have prevented normal operation. The engine was completely disassembled and all damage noted was consistent with impact. The cause of the propeller rpm becoming uncontrollable could not be determined.

Text from the NTSB. Open the NTSB docket for ANC24LA064 for the full record.