LONDON – The report of the incident involving a SAS ATR-72 (OY-JZC) on a domestic route in Norway has been published by Statens Havarikomisjon (SHK), the Norwegian accident investigation board. The icing-incident made the airline terminate Norway’s domestic- routes with the aircraft.
Flight SK4144 was operated by the Danish airline Jet Time AS on behalf of SAS, on November 14, 2016, en route from Bergen to Ålesund, west of Førde Airport Bringeland, when control of the aircraft was temporarily lost in severe icing.
It banked uncontrollably and lost considerable altitude. The crew regained control of the aircraft and left the area where the icing had occurred.
“This and two other serious icing incidents involving the ATR 72-212A illustrate the importance of monitoring airspeed and climb in order to operate the aircraft within its defined performance limitations,” writes SHK in the report.
Moderate icing had been forecasted along the route. As SAS4144 climbed through FL137, south of Sognefjord, the crew observed that they had encountered “severe icing.”
The Crew’s Response
Just before the loss of control, the airplane climb performance had decreased significantly. The crew, therefore, decided to divert towards the coast in order to avoid icing conditions and the mountainous terrain inside the coastline.
However, their decision proved to be too late. The control loss occurred during the turn towards the coast. It appeared suddenly to the crew, whose initial reaction was not optimal.
“AIBN is of the opinion that the crew became startled as they did not disengage the autopilot.”
The crew have later expressed that they were expecting to exit the icing conditions sooner by climbing above the clouds. The clouds containing icing conditions did, however, go much higher than they realized. As AIBN sees it, this could explain why the decision to divert was made too late to avoid the control loss.
The inquiry says the loss of control resulted from “insufficient planning” and “inappropriate decisions” en route, particularly the attempt to climb with degraded aircraft performance.
It states that the pilots “did not make optimal use” of the 10min spent in icing conditions before the upset, believing they would climb out of the icing above 14,000ft. That they chose to level off at 15,000ft but not change course indicates that they “still did not fully understand how serious the situation had, in fact, become.”
None of the 40 occupants was injured and the aircraft was undamaged.
Wet Lease Focus
The accident board has also reviewed the incident involving SAS4144 with a focus on possible contributing factors that may be directly related to wet lease, foreign operators unfamiliar with Norwegian conditions.
You can read the full report here.
Featured image: SAS Jet Time ATR-72. Photo: Wiki Commons