What happened
On February 15, 1995, a Piper PA-28R-201T D-ELUC departed Courchevel, France, bound for Leutkirch, Germany. The pilot initially planned a route via Fribourg and Willisau but altered course due to poor weather over Lake Geneva. Instead, the aircraft flew eastward through Chamonix and Martigny toward the Furka Pass. Over Sion, the plane was at 6,500 feet with cloud bases around 8,000 feet. As it climbed toward the pass in the Upper Valais, the pilot reached approximately 10,000 feet.
Near the Rhône Glacier and the Belvédère Hotel, the aircraft began an uncommanded descent. The pilot attempted to compensate by increasing engine power but observed a sharp drop in manifold pressure. An intermittent stall warning activated, prompting the pilot to abort a right turn toward the Valais. Activating the alternate air source provided only a brief, ineffective change in engine RPM. With visibility deteriorating and altitude continuing to fall, the pilot spotted a flat snowfield at the bottom of a valley near Realp, about 2 km south-southeast of the Furka Pass. At 12:45 local time, an emergency landing was attempted with the landing gear retracted.
The aircraft collided with a rock band during the approach, sustaining significant damage. The pilot emerged uninjured, while the passenger suffered minor injuries. The pilot later communicated his position via another aircraft in the A9 IFR corridor.
The investigation
SUST examined the flight record, weather data, and the wreckage. The pilot held a valid commercial license with substantial recent experience. The aircraft was properly maintained, with its last 100-hour inspection completed in September 1994, which included checks of the intake air lines for damage and loose clamps.
Weather conditions at the accident site featured overcast skies (8/8 coverage) with cloud bases between 2,800 and 3,000 meters. Visibility outside clouds was good, but diffuse conditions prevailed within the mountainous terrain. The pilot had received forecasts indicating moderate to strong turbulence and icing risks.
Examination of the recovered aircraft revealed that the turbocharger’s central housing contained heavy oil carbon deposits due to shaft leaks and high exhaust temperatures, though this did not significantly affect performance. Crucially, the hose connection between the first and second pipes after the turbocharger had detached, allowing charged air to escape. The first pipe segment showed stress fractures likely caused by operational loads. The pilot reported similar issues with the intake line occurring twice previously.
Findings
The accident resulted from a loss of engine power due to a probable malfunction in the intake air system, specifically the detachment of a hose connection after the turbocharger. Contributing factors included:
- Inappropriate flight tactics in mountainous terrain under deteriorating weather conditions.
- Diffuse visibility and cloud bases that limited situational awareness near the Furka Pass.
- Mechanical failure of the intake system, likely exacerbated by prior stress on the first pipe segment.
- Emergency landing with retracted gear, which led to a collision with a rock band, causing significant aircraft damage.
The pilot’s decision to land on the snowfield was deemed correct given the circumstances, but the mechanical failure prevented recovery of altitude or power.
Safety action
No specific safety recommendations were issued in this report. However, the investigation highlighted the importance of regular inspection of intake air line connections and clamps, particularly on aircraft with reported prior issues in these components.