What happened
On April 6, 2015, a Piper PA-18 (registration HB-PMN) was performing a series of takeoffs and landings on the Rosablanche Glacier. Following several successful maneuvers, the pilot attempted to land on a steep section of the slope. During the second landing attempt, the aircraft failed to reach the top of the track, and the pilot attempted a turn too late, leaving the aircraft nose-facing the slope. To reposition, the pilot shut down the engine and manually rotated the aircraft 90 degrees so the nose was roughly perpendicular to the slope. During this repositioning, the rear ski became misaligned and was not corrected.
After a brief pause, the pilot and passenger re-entered the cockpit and restarted the engine. As the pilot applied full throttle, they applied left rudder to quickly align the aircraft with the slope. While the aircraft initially moved forward from its stationary position, the pilot attempted to correct the trajectory with right rudder but was unable to stop the leftward rotation. The pilot subsequently cut the throttle, but the leftward turn continued, causing the right ski to dig into the snow. This led to the failure of the right landing gear and the right wing striking the snow. The aircraft decelerated sharply before the nose buried into the snow, coming to rest at an angle of approximately 60 degrees from the horizontal.
The investigation
The investigation established that the pilot and one passenger were uninjured during the incident. Following the impact, the occupants were unable to contact emergency services via GSM due to a lack of network coverage. The pilot managed to contact another aircraft via radio to request a helicopter for extraction. The pilot was able to notify REGA (Swiss Air-Rescue) only after being transported to Sion by helicopter.
Findings
- The primary cause of the accident was the inability to stop a leftward rotation during the takeoff roll.
- The aircraft's rear ski was improperly aligned following a manual repositioning maneuver prior to the final takeoff attempt.
- The use of left rudder at full throttle, followed by an unsuccessful attempt to correct the heading with right rudder, resulted in the right ski digging into the snow and the subsequent structural failure of the landing gear.