NTSB Investigation of an Icing-Related Aerodynamic Stall Incident and Pilot Response

摘要

On September 5, 2012, Era Aviation (doing business as Era Alaska) Flight 874 experienced an uncommanded left roll and uncontrolled descent during climb at about 12,000 feet. The flight crew of the Bombardier DHC-8-103 regained control of the airplane at about 7,000 feet and returned to Ted Stevens Anchorage International Airport in Anchorage, Alaska. Analysis of the data collected by the Flight Data Recorder showed that the aircraft experienced an aerodynamic stall during climb at a higher airspeed than predicted by the aircraft's flight manual. During the climb, the pilot and copilot did not monitor airspeed and thought that the pre-stall buffet of the aircraft was due to ice shedding off the propellers. Pilot reports and drag calculations support the presence of ice which can raise an aircraft's stall airspeed (or lower its stall angle of attack) causing the aircraft to stall unexpectedly. The crew responded by pulling back on the column and reducing engine power. The current stall-recovery guidance is to lower the aircraft's nose and increase engine power so that airflow can reattach and lift be restored. Company stall-recovery procedures were consistent with official guidance, but pilot recognition of an aerodynamic stall event is crucial to both stall avoidance and stall recovery.