On 31 January 2005, a Cessna 208 stalled and crashed on take off from Helsinki-Vantaa following failure to properly de-ice the aircraft.
The following is an extract from the Summary within the official Investigation Report published by the Accident Investigation Board Finland (AIBF):
"…A Swedish Cessna 208B aircraft registered SE-KYH, owned by Nord-Flyg AB and transporting air freight to Sweden, crashed into the ground within the air-side after takeoff. The pilot suffered minor injuries. The aircraft was completely destroyed.
The aircraft arrived from Sweden …landing at Helsinki-Vantaa airport around 02:47. According to standard company policy, Nord-Flyg AB operates with a two person crew. However, on the day in question the co-pilot had taken ill and the flight was flown without a co-pilot. The pilot checked in for duty at the airport at around 14:30 to prepare for the return leg. It had been snowing at the airport until 09:20 and the temperature was hovering at around zero degrees Celsius. After having arrived at the airport, the pilot began to brush the accumulated snow and frozen snow melt off the upper surfaces of the aircraft. As per his account, there was a great deal of snow and ice on the aircraft. He did not, however, manage to brush all of the impurities off of the surfaces of the aircraft. …He took off from runway 22L. All went well until he reached the height of 800-1000 ft (250-300 m) and retracted the trailing edge flaps. Immediately after flap retraction, the pilot lost control of the aircraft, which began turning to the right. The pilot attempted to fly the aircraft to the end section of runway 22R to make an emergency landing but the aircraft crashed into the terrain between the runways.
Investigation revealed that the pilot did not succeed in brushing the snow and ice off of the upper surfaces of the wings, fuselage and stabilizers. When the wreckage was examined, it was estimated that the coat of snow, frozen slush and ice on the upper surface of the wings and on the sides of the fuselage varied between 0.5-1.5 cm in thickness. As the pilot retracted the flaps from the take-off setting, the compacted snow and ice on the upper surface of the wing disturbed the lift enough to induce a stall. The aircraft rolled to the right and lost altitude. The pilot was unable to recover and the aircraft hit the ground at a shallow dive angle and was destroyed. At the time of impact the trailing edge flaps were in the clean configuration.
The primary cause of the accident was that the pilot executed a take-off with an aircraft whose aerodynamic properties were fundamentally degraded due to the accumulated ice and snow on the upper surface of the wing. During the initial climb and immediately after flap retraction, airflow separated from the surface of the wing and the pilot did not manage to regain control of the aircraft. The pilot did not recognize the stall and did not act in the manner required to recover from one or, it might be that he had not received sufficient training for such situations."
For further information see the full accident report published by the AIB Finland.