Updated: Apr 10, 2022
A Swearingen SA227-AC Metro III was operating a scheduled passenger flight between Ørland Airport and Oslo-Gardermoen Airport, both in Norway. Onboard a crew of two and nine passengers for the ~215 nm / 400 km flight.
Recovery of the aircraft in progress. (Source; Statens havarik kommisjon for transport)
After an uneventful flight the aircraft was approaching Oslo, the weather was far from CAVOK temperature minus 7ºC, with no wind and freezing fog. The approach and touchdown to Runway 19R were all normal, the speed over the threshold was 107 knots and the aircraft touched down in the touchdown zone of the runway. When the speed reached 60 knots, as per company procedure the co-pilot (who ha been the pilot flying) handed over the control of the aircraft to the captain. The captain retarded the power levers to idle and called for the speed levers to be pulled to the "LOW" setting. This would, amongst others, activate the nosewheel steering. As soon as the nosewheel steering activated, when the speed levers were placed in the "LOW" position, there was an uncommanded turn to the right that could not be corrected by the crew. The nosewheel steering had activated and in an attempt to correct it the captain gave full opposite rudder pedal input (control input for the nosewheel steering) This had no effect on the aircraft direction and with the crew unable to correct the turn to the right the aircraft left the runway at a speed of approximately 30-40 knots and came to a stop in a one-meter deep snowbank that consisted of hard-packed snow. The crew shut the engines down, initiated the shutdown checklist and initiated an evacuation of the aircraft.
The aircraft after the evacuation, stuck in the snowbank (Source; Statens havarik kommisjon for transport)
Due to the fog, ATC only had the ground radar to monitor the aircraft's position on the airfield, when the ATC controller observed the aircraft at the runway edge, he queried the crew, who informed him of the situation after which he alerted the emergency services. There were no injuries to the occupants the aircraft was damaged beyond repair. An investigation into the accident was performed by the Statens Havarikommisjon for Transport (Norwegian Transportation Safety Board). Their report (in Norwegian) is available by clicking here.
Basic Schematic for the nosewheel steering system (Source; Statens havarik kommisjon for transport)
They identified the following causes and contributing factors (a summary in English of the possible cause is available on page 18 in the report mentioned above);
An extensive examination of the nosewheel steering system uncovered no single cause.
Signs of unsatisfactory maintenance were found
Issues with the nosewheel steering system could have caused a temporary fault, especially when issues would get combined.
A similar fault had occurred six days before, however, the crew had deactivated the nosewheel steering quickly enough to regain control.
Subsequent maintenance action had not been able to reproduce the fault, and the aircraft was released to service.