What happened
On December 19, 1982, a private Maule M-5-235C aircraft with registration HB-EVY departed from Sitterdorf airfield for glacier landing training. The pilot and one passenger flew to the Claridenfirn glacier in the canton of Glarus. After flying over the landing site twice, the pilot decided to land on the eastern part of the glacier without stopping, intending to take off again after a 90-degree left turn.
During the approach, a gust of wind caused the aircraft to touch down approximately 100 meters later than planned. Immediately after touchdown, the pilot initiated a tight 90-degree left turn and began the takeoff roll without stopping. After traveling about 50 meters along the runway, the pilot spotted an open crevasse on the left side and attempted to avoid it by turning right.
As the aircraft continued its takeoff run, it had not yet reached sufficient lift speed. Approximately 150 meters into the takeoff phase, the aircraft crossed another open crevasse approximately 7 meters wide. The impact tore off the right main landing gear. The aircraft came to a sudden stop in a snow-filled crevasse about 15 meters later.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined the accident circumstances and found that the pilot held a valid commercial pilot license with appropriate ratings. The pilot had accumulated 1,171 total flight hours, including 450 hours in the Maule model, with recent activity of 4 hours and 28 minutes in the preceding 90 days.
The aircraft was certified for VFR operations, and no pre-existing technical defects were found. The weight and center of gravity were within prescribed limits. Weather conditions at the time included scattered clouds, unlimited visibility, and winds from the north to east sector at 5-10 knots. Temperature was -12°C with new snow depth of 1-1.5 meters and snowdrifts up to 40 cm high at the accident site.
Findings
The primary cause of the accident was an unfavorable initial situation for takeoff near open crevasses. The landing occurred too late due to a gust, and the subsequent 90-degree left turn was executed too close to hazardous terrain features. This combination placed the takeoff phase directly into the area of open crevasses on the glacier.
The aircraft lost its right main landing gear when crossing a 7-meter wide open crevasse while still at insufficient flight speed. The accident resulted in one passenger being seriously injured, while the pilot sustained no injuries. The aircraft was destroyed.
Safety action
This report highlights the dangers of performing takeoff maneuvers on glacier surfaces with hidden or visible crevasses, particularly when wind conditions affect landing distance and subsequent maneuvering space.