What happened
A chartered flight carrying the pilot, four passengers, and unsecured cargo departed for a fishing lodge without incident. Approximately 45 minutes into the flight, while cruising at an altitude of 1,700 feet over a river and rugged landscape, the aircraft experienced a loss of engine power. In response to the power loss, the pilot attempted to perform an emergency landing in a small lake situated roughly one mile west of the river, which measured approximately 1,200 feet in length.
During the approach to the lake, the aircraft type stalled and struck the swampy ground at the edge of the water in a steep, nose-down position. The accident resulted in 5 fatalities.
Findings
Investigation of the wreckage identified that the failure originated in the number one engine. Specifically, the engine's exhaust pushrod failed due to fatigue just below the top valve ball end. Analysis of the component indicated that material had been displaced from the rod during the installation of the ball end. It is believed that a fatigue crack may have started from a score mark created during this installation process. The investigation noted that surface scratches can decrease the operational lifespan of a pushrod. Furthermore, the overhaul manual provided insufficient data regarding the necessary inspection intervals or the expected service life for such pushrods.