What happened
On April 27, 2000, a Piper PA28-180, registration HB-OQP, departed from Bern for a private VFR flight to Calvi, Corsica, carrying the pilot and three passengers. The flight initially proceeded through the Gemmi Pass and the Sion restricted area under favorable visibility. However, the region was experiencing a South Föhn weather pattern.
As the aircraft approached the Fenêtre de Durand at approximately 10:15 AM, it was struck by a massive downdraft. The pilot attempted to regain altitude by maneuvering toward the south flank of the Pointe d’Otemma. Despite a brief period of climbing, the aircraft was again caught in intense turbulence and strong downdrafts while attempting a turning maneuver away from the slope.
Unable to maintain altitude, the pilot attempted an emergency landing on the Otemma Glacier. Due to overcast skies and diffuse lighting, the glacier's surface was difficult to discern. The aircraft struck the snow hard, causing the right wing to separate. The aircraft then overturned, coming to rest on its back with the left wing also detached. The impact resulted in one fatality and two serious injuries among the occupants.
The investigation
The investigation established that the aircraft was properly registered and that no pre-existing mechanical defects were found. However, the investigation noted that the aircraft's center of gravity was at the rear limit of the permitted envelope and that the aircraft was heavily loaded.
Furthermore, the Emergency Locator Transmitter (ELT) was found to be non-functional because the antenna cable was unplugged and the device was not switched on. The search for the wreckage was initiated after the aircraft failed to arrive at its destination, with the crash site eventually located by a search helicopter later that evening.
Findings
- The primary cause of the accident was the decision to continue the flight despite adverse wind conditions.
- The South Föhn weather pattern created significant turbulence and downdrafts on the northern side of the Alps.
- The pilot's attempt to regain altitude by flying toward the ridge, rather than retreating north, indicated a lack of awareness regarding the risks posed by the weather and the aircraft's performance limits.
- The heavy load and rearward center of gravity contributed to the difficulty of controlling the aircraft in turbulent conditions.