What happened
The aircraft was engaged in transporting mountain climbers from a glacier. During the takeoff phase from the glacier surface, the right landing gear strut experienced a catastrophic failure at the axle point. This mechanical separation caused the wheel or ski assembly to dangle freely without structural support.
Following the initial failure, the pilot executed an emergency landing on a nearby gravel runway. To mitigate damage and maintain control, the pilot held off the right side of the aircraft for as long as possible during the approach. When the unsupported right strut finally touched down on the gravel surface, it dug into the ground and subsequently collapsed.
The investigation
A thorough examination of the failed component revealed significant structural degradation. A fatigue crack was found extending through approximately 65% of the cross-section of the strut, identified by part number 0741001-8. This damage was located where two bolt holes had been drilled, approximately 1 1/2 inches from the lower end of the component.
Further analysis determined that the crack originated at the bottom of corrosion pits, specifically rust formations. These pits were situated at the inboard side of the upper aft spindle attachment bolt hole, indicating that environmental factors contributed to the initiation of the fatigue failure.