Accident Overview
On 17 January 1992, a Piper PA-18-180M aircraft, registration HB-ORZ, was involved in an accident at the mountain landing strip of Croix-de-Coeur, in the commune of Riddes, Switzerland. The aircraft, operated by Flugsportgruppe Zürich-Oberland, was conducting a training flight for mountain landing endorsement. The crew consisted of a flight instructor and a student pilot. The accident occurred during the takeoff phase and resulted in substantial damage to the aircraft. No persons were injured.
Flight Sequence
The flight originated from Speck-Fehraltorf airfield. The student and instructor first flew to the Tsanfleuron glacier, where the student performed two landings under dual control and then seven solo landings. Afterwards, the instructor rejoined the student, and they flew to Croix-de-Coeur. Before landing, they conducted two reconnaissance passes, observing that the snow-covered runway had been compacted by a snow vehicle. After a normal landing, the instructor exited the aircraft. The student prepared for takeoff and noted that the aircraft had left no tracks in the hard snow during landing. The takeoff was initiated from the upper flat part of the strip, but the student deviated slightly to the right of the main axis, following tracks left by the snow vehicle. Realizing the error, the student attempted to correct, but the aircraft's speed was too low to avoid a depression and a bump in the terrain at the edge of the prepared area. The left landing gear struck the bump and collapsed, causing the aircraft to lift briefly, then crash down hard, rotating 90 degrees and coming to rest.
Investigation Findings
- The student held a valid private pilot license and had begun glacier training on 11 April 1991, with 86 dual and 32 solo glacier landings prior to the accident. This was his first landing at Croix-de-Coeur.
- The instructor held a valid restricted professional pilot license and a glacier instructor endorsement.
- No evidence suggested the student was unfit to fly at the time of the accident.
- The aircraft had valid airworthiness certificates and was normally maintained; its mass and center of gravity were within limits.
- Weather at the time was fine with visibility over 20 km, wind 180°/2 kts.
- The entire landing area had been packed by snow vehicles in the direction of the slope; in the upper part, the tracks were angled relative to the takeoff axis.
- Examination of the wreckage revealed the left and right landing gear folded upward, the left wing bent down at the root, broken propeller blades, and various sheet metal deformations.
Cause
The accident was due to an erroneous assessment of the takeoff axis, resulting in part from the condition of the runway surface and the lack of landmarks, as well as the fact that the student did not perform a circuit under dual control.