What happened
An airline transport pilot was operating an on-demand charter flight in a wheel/ski-equipped airplane carrying three passengers and climbing gear. The flight was traveling toward a mountain climbing base camp located on a glacier at 7,200 feet MSL. During the westbound transit, the aircraft struck snow-covered terrain at the 8,200-foot level of a remote mountain pass. The wreckage was discovered by a passing airplane. At the time of impact, the aircraft was in a near horizontal position with wings level and approximately 5 degrees nose down. The nose of the aircraft was oriented in the opposite direction of the intended westbound flight path.
The investigation
The investigation included documentation of all passenger, pilot, and cargo positions. Following recovery, the weights of the occupants and climbing gear were recorded. At the time of the accident, the gross weight of the aircraft was estimated to be 20 pounds over the maximum gross weight limit of 3,350 pounds. Because there are no center of gravity (CG) limits for weights exceeding the maximum gross weight, the estimated CG of 154.1 inches was compared to the limits at maximum gross weight (140 to 156 inches), placing the aircraft near the aft limit. No pre-accident mechanical anomalies were identified. The engine was tested on a stand and operated at various power settings for an extended period, during which it produced its maximum rated RPM.