Aircraft Crash at Hummelfjell Due to Heavy Icing (LN-SUR)

Flight Details and Initial Conditions The aircraft departed Vaernes Airport, Trondheim, at 0830 local time on a scheduled flight to Oslo, carrying a crew of two and ten passengers. Shortly after takeoff, the aircraft entered clouds at 2,500 feet and lost visual contact with the ground. During the climb between Vaernes and Tolga, the copilot noted that the indicated airspeed was 20 knots below normal after normal cruise power was set at cruising altitude. The aircraft reported passing the Tolga radio beacon at 8,000 feet at 0912 hours, noting light icing. This was the last radio contact with the aircraft. From this point, icing increased rapidly, and the aircraft began losing altitude despite the use of the de-icing system for the wing and tail planes. At 0925 hours, a decision was made to return to Vaernes Airport. The aircraft, approximately abeam Tolga and to the east, altered its course 25 to 30 degrees northeast. This maneuver, carried out by the captain, was interpreted by the copilot as a decision to divert to Rhos. The copilot took over the controls while the captain continued attempting to establish radio contact on frequency 126.7 mc/s, but no signals were received. At approximately 0950 hours, the aircraft struck Hummelfjell at a height of approximately 1,350 meters. At the time of the crash, the aircraft was in heavy fog, and the cockpit window was covered with ice, drastically reducing the crew's visibility. The impact force was somewhat reduced as the aircraft touched down in a bowl in the terrain and made two bounces on the snow, which covered the mountain to a depth of 40 cm, before settling down. The captain and one passenger died instantly.