What happened
On January 29, 2010, a Robinson R44 Raven I helicopter was conducting a flight from Sömmerda with the intended destination of Krefeld. During the flight, the pilot was unable to locate the target airfield and performed an unplanned landing on a snow-covered field to seek directions from a local resident. A passenger then joined the flight to assist with navigation toward the Altena-Hegenscheid airfield.
As the helicopter approached the airfield, the pilot attempted to land along runway 24 near the control tower. Shortly before reaching the tower, the pilot activated the cockpit heating system. This action caused the interior of the windshields to fog up abruptly, severely obscuring visibility. In an attempt to clear the windows, the pilot instructed the passengers to open the doors. Seconds later, at approximately 17:20 local time, the helicopter collided with the control tower and an adjacent garage. The aircraft came to rest in the snow on its left side. The three persons on board were able to exit the wreckage independently, though the aircraft sustained heavy damage and there were injuries, including one person seriously injured and two persons lightly injured.
The investigation
The BFU investigation examined the pilot's experience, the aircraft's maintenance history, and the meteorological conditions. The investigation noted that the pilot had relatively low total flight experience, with approximately 183 hours on the R44 type. The weather conditions at the time of the accident involved low visibility, light snowfall, and a closed airfield covered in approximately 30 cm of snow. The investigators also looked into the sudden fogging of the cockpit windows, consulting with the manufacturer and other operators of the same aircraft type.