de Havilland DH-114 Heron LN-SUR, named ‘Lars’, took off from Trondheim at 08:30 for a domestic flight to Oslo. The flight climbed to a cruising altitude of 8000 feet, reaching Tolga radio beacon at 09:12. Light icing was experienced, which increased rapidly. The Heron started to lose altitude despite of the full use of the de-icing system. The captain elected to return to Trondheim. At 09:50 the aircraft struck Hommelfjell mountain at a height of about 1350 m, bounced in the snow and settled. Parts of the aircraft were used to rebuild Heron LN-NPI, which was damaged on January 26, 1957. PROBABLE CAUSE: “Unusually heavy icing which the aircraft encountered. Severe downdraft immediately prior to the crash may have been a contributing factor.”