What happened
While en route to Skien, an aircraft carrying two crew members and 11 passengers encountered ice accumulation on the wings. Although the ice was noted as being thin, the crew did not activate the de-icing system. During the descent toward runway 1s at Geiteryggen, the ground proximity warning system (GPWS) triggered three separate times. At the time, the aircraft was flying through clouds, preventing the crew from maintaining visual contact with the terrain.
Due to a combination of the GPWS alerts and ineffective crew coordination, the de-icing procedures were neglected. The aircraft touched down at 18:28 hrs with an unusually high sink rate, causing a landing so forceful that passengers reported the sensation of the plane dropping onto the runway. This impact caused permanent deformation to the left wing, which displaced the left landing gear and caused the left propeller to strike the runway surface. Consequently, the crew lost directional control, causing the aircraft to veer left and exit the runway. The aircraft eventually struck a gravel bank 371 metres from the touchdown point. The impact resulted in several injuries and the total loss of the aircraft. At the time of the accident, conditions were dark with light rain and a temperature of 4 °C.
Findings
Investigators determined that ice on the wings was the likely initiating factor in the accident. While it remains unclear if the ice caused a high sink rate following a reduction in engine power or if a stall occurred prior to touchdown, the investigation highlighted significant organizational issues. The AIBN found that the operator's reliance on minimum operational standards led to weaknesses in quality assurance and procedures. Furthermore, the investigation noted that the crew composition on the Skien–Bergen route occasionally fell below the expected standard for scheduled passenger services, and identified a need for improved de-icing protocols.