What happened
On May 15, 1997, a Piper PA 28RT-201T, registration D-EKUS, departed Würzburg-Schenkenturm, Germany, for Cannes-Mandelieu, France. The flight was conducted under Visual Flight Rules (VFR) with three occupants on board, including the pilot and two passengers.
Initially, the aircraft followed its planned route through Swiss airspace. During communications with Geneva controllers, the pilot requested a change in strategy, opting to fly direct toward Chamonix rather than following the original flight plan. As the aircraft continued its climb, radar tracking indicated a continuous increase in altitude accompanied by several changes in heading. During the final phase of the flight, the aircraft performed a 180-degree turn. At 10:54 UTC, the aircraft was recorded at flight level 154 before it suffered an in-flight breakup. The wreckage was subsequently located in a steep, mountainous area near Saint Chaffered, specifically at the Col de l'Oule.
The investigation
The investigation focused on the aircraft's structural failure and the environmental conditions at the time of the accident. Investigators examined the wreckage, which was found widely dispersed, and analyzed radar tracks and radio transcripts from Geneva and Marseille air traffic services.
Technical examinations revealed that the aircraft's vacuum pump was functioning prior to impact and that the aircraft was within its weight and balance limits. However, the investigation noted that the aircraft was not equipped with an oxygen system or any anti-icing/de-icing equipment. Meteorological analysis confirmed that the aircraft was flying through an unstable air mass characterized by convective development, turbulence, and heavy icing conditions.
Findings
- The aircraft broke up in flight due to a loss of control that subjected the airframe to excessive positive load factors.
- The pilot encountered severe weather, including heavy icing and turbulence, while flying through clouds that obscured visual references.
- The presence of significant moisture and freezing temperatures (isotherms at 0°C and -10°C) likely contributed to heavy icing on the airframe.
- The crew was likely affected by hypoxia, as the aircraft lacked an oxygen supply and was climbing into altitudes where the air was thin.
- Contributing factors included a lack of thorough flight preparation, which led to the decision to overfly the Alps despite forecasted poor weather, and pilot fatigue following a long flight duration.