What happened
While performing a climbout, the aircraft type encountered freezing rain, which caused rapid ice accumulation on the airframe. This accumulation resulted in a significant loss of the ability to maintain altitude. In response to the deteriorating conditions, the pilot notified air traffic control of the inability to hold altitude and requested a return to the departure airport, Great Falls.
Radar tracking indicated that the aircraft entered a right-hand turn while flying over mountainous terrain. At the time of the final radar contact, the aircraft was descending at approximately 400 feet per minute. The aircraft was positioned at an altitude between 8,400 and 8,500 feet, passing within half a mile of a mountain summit that reaches 8,309 feet. Shortly after losing radar contact, the aircraft struck the southwest side of the 8,309-foot peak, approximately half a mile south of its last known position.
Analysis of the wreckage and impact patterns suggested that the aircraft struck the terrain in an inverted position at a steep angle and relatively low speed during a downhill descent.
Findings
- The primary factor in the loss of climb performance was rapid airframe ice accretion caused by freezing rain.
- There was no evidence of mechanical failure or malfunctions within the aircraft systems prior to the impact.