What happened
On January 19, 2002, a Piper PA-28-181 Archer II, registration HB-PGS, was conducting a private VFR pleasure flight through the Swiss Alps. The flight originated from Sion, with a planned route intended to traverse the Grande Dixence dam, the Pas de Chèvre, and various landmarks including the Otemma Glacier, eventually returning to Sion.
While flying at approximately 10,000 feet, the aircraft entered the Tsijiore Nouve glacier area. During a left-hand turn, the aircraft's right wheel made initial contact with the glacier surface, followed by a second hard impact. The aircraft then struck a rocky outcrop and came to rest upside down, balanced atop a crevasse. The impact resulted in four injuries, with the pilot sustaining serious injuries.
The investigation
Investigators examined the wreckage located in a highly rugged and crevassed area, which required a helicopter rescue operation to reach the occupants. The investigation focused on the aircraft's performance, the environmental conditions, and the pilot's flight path.
Technical analysis confirmed the aircraft was within its weight and balance limits and that the engine was functioning normally at the time of the accident, with the throttle found in the full-power position. The investigation also looked into the meteorological conditions, noting a "white day" effect where high-altitude clouds and a sun position that obscured depth perception and contrast made the terrain difficult to interpret.
Findings
- The primary cause of the accident was the collision of the aircraft with uneven, dirty firn (snow/ice) terrain, likely resulting from a navigational error.
- The pilot likely entered the Tsiji 0re Nouve glacier by mistake, intending to fly over the nearby Glacier de Pièce, which shares a similar orientation and appearance.
- Environmental factors, specifically the lack of visual contrast due to the "white day" conditions and the sun's position, hindered the pilot's ability to recognize the error.
- The aircraft was operating at a high mass, which reduced its climb performance and energy reserves during the maneuvering required in the narrow glacier valley.
- The pilot's previous experience with mountain landings in higher-performance aircraft may have led to an overestimation of the available maneuvering margins in the Piper PA-28-181 Archer II.