Accident Sequence
On a flight to Skien, Norway, an aircraft carrying a crew of two and 11 passengers encountered ice accumulation on its wings during the flight. The crew assessed the ice as too thin to require removal based on the company's standard operating procedures. During the descent toward runway 19 at Geiteryggen Airport (Skien), the ground proximity warning system (GPWS) activated three times. The aircraft was in clouds, and the crew did not have visual contact with the ground. The combination of GPWS warnings and poor crew coordination led the crew to forget to activate the wing de-icing system.
The landing at 1828 hours was unusually hard, with several passengers perceiving that the aircraft dropped the last few meters onto the runway. The impact caused permanent deformation of the left wing, displacing the left landing gear and causing the left propeller to contact the runway. The crew lost directional control, and the aircraft veered left, departing the runway and striking a gravel bank 371 meters from the touchdown point. The collision injured the crew and several passengers, and the aircraft was a total loss. Weather conditions at Geiteryggen at the time were dark, with light rain and a temperature of 4 °C. The wind was reported as 120° at 10 knots.
Investigation Findings
The Accident Investigation Board of Norway (AIBN) determined that ice on the wings was the probable initiating factor for the accident. The investigation examined crew composition and training, as well as organizational aspects of the company. The company was found to have largely based its operations on minimum standards, resulting in weaknesses in organization, procedures, and quality assurance. These conditions indirectly led to the operation of the route with a crew that, at times, did not maintain the standard expected for scheduled passenger flights. The investigation also noted that procedures for de-icing aircraft wings could be improved.
Specific significant findings included: a) The decision to wait to remove ice because, according to the SOP, removal was required only if ice reached "typically half an inch on the leading edge"; this postponement contributed to forgetting the ice. b) During the approach, the relationship between the flight crew members was tense, leading to a breakdown in crew coordination. c) The GPWS warnings resulted in a very high workload for the crew, which, combined with defective crew coordination, contributed to forgetting the ice on the wings. d) It is probable that the aircraft hit the runway with great force because the wings were contaminated with ice; the AIBN did not form a final opinion on whether the wings stalled, the aircraft developed a high sink rate due to ice accretion, or a combination of both. e) The company could only provide documentary evidence that the commander had attended an absolute minimum of training after employment; parts of mandatory training were self-study without formal verification. f) The company's operation was largely based on minimum solutions, reducing safety margins. g) The company's quality system contributed little to ensuring safe operational practices. h) Authority inspection of the company was deficient.
Official Conclusions
The AIBN's official probable cause statement is that ice on the wings was the initiating factor. The investigation highlighted the decision to postpone ice removal due to ambiguous SOP wording, tense crew coordination, high workload from GPWS warnings, and underlying organizational deficiencies including minimal training and weak quality assurance.