Incident Overview
On 3 January 2020, a Cessna 172S, registration LN-AZA, operated by OSM Aviation Academy AB, was conducting an IFR training flight. The aircraft departed Kristiansand Airport Kjevik at 0946 local time, flew near the coast to Stavanger Airport Sola, and landed there at 1150. After a lunch break, the crew planned to continue to Haugesund Airport Karmøy and Stord Airport Sørstokken before returning to Arendal Airport Gulknapp. However, due to deteriorating weather, they cancelled the remaining legs and decided to fly directly back to Arendal over mountainous terrain.
Flight Details
The aircraft was a Cessna 172S, certified for instrument meteorological conditions (IMC) but not for flight in icing conditions. The crew consisted of an instructor and a student pilot. The student had planned the route using official weather sources and the Windy.com application. Before departure, they performed a Threat and Error Management (TEM) assessment, noting convective activity but no forecast icing outside CB cells. They aimed to remain in visual meteorological conditions (VMC) as much as possible.
Icing Encounter
While en route from the Stavanger area to Arendal, the crew entered IMC and icing conditions at flight levels FL100–FL110. Significant ice accumulation occurred. The crew observed sluggish flight controls and vibrations. The aircraft remained in IMC and icing conditions for 17 minutes. With assistance from air traffic services, the crew altered their route and descended to a lower altitude, where the ice shed. The aircraft landed normally at Stavanger Airport Sola. Neither the instructor nor the student was injured.
Aftermath and Safety Measures
Following the incident, OSM Aviation Academy revised its procedures for planning longer IFR flights. The main measure introduced was to avoid flying in IMC when the forecast 0°C isotherm is below the Minimum Safe Altitude. The accident investigation board noted that similar precautions should be considered by all operators flying IFR aircraft not certified for icing conditions.