Flight History
On the evening of 18 November 1999, the pilot departed Lyon-Bron, France, at 1731 local time on an IFR flight to Grenchen, Switzerland. The aircraft, a Piper PA-46 Malibu (registration HB-PLD), carried the pilot and two passengers. The flight proceeded without incident until reaching the Willisau VOR (WIL), where the approach to Grenchen begins. The pilot was informed that Grenchen was experiencing heavy snowfall and that the runway was not cleared. Although visibility and cloud base were marginally above limits, the pilot decided to attempt an approach while obtaining clearance to divert to Bern if a missed approach was executed, as conditions there were deemed suitable. The approach to Grenchen resulted in a missed approach, during which the clearance was modified due to traffic in the Bern holding pattern. The pilot flew the standard missed approach procedure back to the WIL VOR. Meanwhile, weather at Bern had deteriorated, and HB-PLD was instructed to hold at the 'BIRKI' holding point, along with four other aircraft.
At approximately 1910, the air traffic controller informed the holding aircraft that snow removal operations had been suspended because heavy snowfall was immediately covering cleared surfaces. After a PA-34 Seneca was authorized to use the uncleared runway at its own risk, the pilot of HB-PLD also decided to attempt a landing under the same conditions. Radar vectors positioned the aircraft for an ILS approach to runway 14. The pilot reported that the approach itself was normal, but upon breaking out, the view through the windshield was severely impaired by snow accumulation. The aircraft touched down on the left side of the runway and, after a short rollout, skidded off the left edge of the pavement. During the excursion, the nose wheel collapsed, causing damage to the nose gear, propeller, engine mount, and engine. The aircraft came to a sudden stop, and the occupants evacuated the cabin unharmed.
Findings
- The pilot held a valid Private Pilot License (A) issued by the Federal Office of Civil Aviation (BAZL).
- The aircraft's mass and center of gravity were within permissible limits.
- The aircraft was certified for IFR operations (Category I).
- According to the pilot, the fuel reserve at landing allowed for an additional 3 hours 45 minutes of flight.
Meteorological Conditions
MeteoSwiss reported the following conditions at the time and location of the accident:
- General weather: A low-pressure system over central Europe, with a subsidiary low over France bringing moist air to the Alps.
- Clouds: 3–5/8 coverage with base at approximately 2100 ft MSL, 5–7/8 coverage at approximately 2700 ft MSL, and 8/8 coverage at 3700 ft MSL; moderate snowfall.
- Visibility: 800–1000 meters.
- Wind: Variable, 0–3 knots.
- Temperature/dew point: 0°C/0°C.
- QNH: 1000 hPa.
- Hazards: Poor visibility conditions.
Aircraft Systems and Condition
The electrical de-icing elements were activated throughout the flight. The pneumatic de-icing boots on the wing leading edges were not operated after leaving the holding pattern. The pilot did not observe ice accretion on the leading edges before starting the approach. After landing, hard-packed snow was found on the wing leading edges. The pilot stated that snow on the windshield made visibility nearly impossible, and even through the heated window panel, visibility was significantly impaired.
Runway Status
Runway 14 was closed by the airport authority due to snow cover. The pilot of HB-PLD was authorized to land at his own risk.
Cause
The runway excursion was due to loss of directional control during landing on a snow-covered runway in heavy snowfall with poor visibility.