What happened
On January 7, 2010, a Piper PA-31 Navajo was performing a positioning flight from Stadtlohn-Vreden to Nordhorn-Lingen following a 100-hour inspection. The flight, which lasted approximately 26 minutes, proceeded without incident at altitudes between 1,500 and 2,000 ft MSL.
As the pilot approached the airfield, the air traffic controller informed the crew that runway 24 was covered in snow and had not been cleared. To assist with visual identification in the featureless, white environment, the controller activated the airfield's night lighting. The pilot, flying a northeast course, initiated a left-hand pattern.
Despite the active lighting, the pilot did not visually identify the runway markings and instead maneuvered into what he believed was the final approach for runway 24. It was only during the touchdown process that the pilot noticed the runway lights to his right. Consequently, the aircraft landed on the snow-covered grass strip to the left of the asphalt runway. The nose gear collapsed upon impact, and the aircraft slid approximately 60 meters before coming to a stop with a slight rightward rotation. There were no injuries to the pilot, though the aircraft sustained heavy damage.
The investigation
The BFU investigation examined the airfield conditions and the visibility of the runway environment. Investigators noted that the snow-covered runway was visually indistinguishable from the surrounding terrain. While the runway edge lights were visible, the bases and structures of the light units were obscured by the snow. The investigation also confirmed that the runway surface showed no previous tire marks from other aircraft, and the ground visibility at the time of the accident was approximately 3 km in light haze, with a temperature of 0 °C.