What happened
During an instrument flight rules departure from Québec/Jean Lesage International Airport, a Dash 8-102, registration C-FHRC, experienced a flight control failure during its climb. While ascending, the first officer noticed increased resistance in the elevator controls. Upon taking command, the pilot-in-command confirmed that the elevators were jammed, noting that the elevator trim was positioned at the nose-down limit.
The crew attempted several recovery procedures, including using the pitch disconnect handle and attempting to engage the autopilot, but the controls remained immobile. The flight crew declared an emergency and requested a return to Jean Lesage Airport. To maintain the aircraft's attitude and vertical speed, the pilots relied on engine power adjustments and elevator trim. During the descent through 6,000 feet, the aircraft's nose suddenly pitched upward, requiring immediate correction via power and trim. The aircraft landed safely without further incident, and subsequent checks showed the controls were functioning normally.
The investigation
Technical inspections of the aircraft's control surfaces following the landing revealed that the leading edges of both the left and right elevators contained large, rough-textured paint drips. These irregularities, which had been present since a previous painting, reduced the clearance between the elevator leading edges and the stabilizer trailing edge to as little as 0.125 inch. This reduced gap, combined with the porous texture of the paint, created an environment where moisture could easily accumulate and freeze.
Investigators also reviewed the weather conditions at the time of departure. The aircraft had been on the ground in Québec amidst light snow, rain, and fog, with temperatures near freezing. Although the pilot-in-command had performed walk-around inspections shortly before takeoff and found no snow, the atmospheric conditions met the criteria for icing conditions as defined by the manufacturer and regulatory bodies. No de-icing or anti-icing fluids had been applied to the aircraft prior to takeoff.
Findings
- Accumulated ice on the control surfaces caused the elevators to jam.
- The leading edges of the elevators featured surface-finish irregularities and paint drips that exceeded manufacturer standards, facilitating ice adhesion.
- The aircraft was operated in atmospheric conditions favorable to surface contamination, yet no de-icing or anti-icing fluids were applied.
- The pilot-in-command's pre-flight inspections failed to detect the presence of wet snow within the narrow gap between the stabilizer and the elevators.
Safety action
Following the investigation, the aircraft manufacturer, Bombardier, issued a Safety of Flight Supplement to all Dash 8 operators. This supplement clarified that the elevator trim lacks the authority to overcome a frozen or jammed elevator and cautioned crews against using full nose-up or nose-down trim settings during such an event, as it could lead to uncontrollable pitch excursions if the controls suddenly become free.