What happened
On November 14, 2016, an ATR 72-212A, registration OY-JZC, operated by Jet Time AS, was performing a scheduled flight from Bergen to Ålesund. While en route through the airspace west of Førde Airport, the aircraft encountered severe icing conditions that led to a temporary loss of control.
As the crew climbed through various flight levels, ice began to accumulate on the airframe. The aircraft's performance monitoring system issued alerts for degraded performance and a requirement to increase speed. In an attempt to escape the intensifying icing, the crew decided to descend from FL160 back toward FL150 and change course further west toward the sea. During this maneuver, the aircraft experienced a sudden sharp bank and a nose-down pitch.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined flight data from the Flight Data Recorder, interviews with the crew and passengers, and meteorological reports. The investigation focused on the sequence of events leading to the loss of control, the crew's decision-making process regarding altitude and airspeed, and the effectiveness of the aircraft's ice protection systems.
Findings
- The primary cause of the loss of control was a combination of insufficient planning and inappropriate decisions during the encounter, specifically the attempt to climb through icing conditions despite declining aircraft performance.
- The crew utilized the autopilot incorrectly during the descent, which contributed to the instability.
- The commander experienced a "startle effect" when the stick shaker activated and the autopilot disconnected, leading to an initial improper response of pulling the control wheel back.
- During the recovery, the crew failed to perform two critical memory items from the stall checklist: deploying flaps and increasing engine power.
- The investigation noted that while the icing was severe, the decision-making regarding altitude changes and speed management was a significant factor in the incident.