Incident Overview
On August 21, 2021, at approximately 1325 Alaska daylight time, a float-equipped de Havilland DHC-3 Otter airplane, registration N560TR, was substantially damaged during a forced landing near Bettles, Alaska. The aircraft was operating as a Title 14 Code of Federal Regulations Part 135 commercial flight with a pilot and two passengers aboard. None of the occupants were injured.
Sequence of Events
While on the base leg approach for a landing at a remote lake, the pilot reported hearing a loud bang. The engine then experienced a total loss of power. Realizing the airplane would be unable to reach its intended destination, the pilot turned the aircraft into the wind and executed a forced landing onto tundra-covered terrain. The landing resulted in substantial damage to the fuselage.
Postaccident Examination
A review of the airplane’s maintenance records showed no anomalies, and no evidence of regulatory noncompliance was found. During postaccident disassembly and examination of the engine, investigators discovered that the engine had seized. The propeller spline was fractured into two pieces, and a substantial amount of metal fragmentation was present in the oil screen. Further examination using a lighted borescope revealed fragments of broken internal engine components, which prevented the removal of the aft accessory wall.