What happened
On 04 November 2003, an Air Canada Jazz de Havilland DHC-8-102, registration C-GONJ, was prepared for a scheduled service from Ottawa to Montréal. Prior to departure, the aircraft had been exposed to freezing rain and ice pellets while parked on the ground. Although the aircraft underwent de-icing with Type I fluid, the crew initiated the take-off run at 1412 EST.
During the rotation phase, the pilot flying experienced a noticeable restriction in the movement of the pitch controls. This prompted an immediate rejected take-off. After clearing the runway, the crew performed control checks and found the elevators to be moving freely without any detectable resistance. The aircraft returned to the gate, where maintenance inspections also found the controls operating normally. No large ice accumulations were found, though some residual de-icing fluid and freezing rain droplets were present on the horizontal stabilizer and elevator surfaces.
The investigation
Investigators examined the mechanical systems of the aircraft, specifically the spring-tab assisted elevator controls. Flight data recorder (FDR) analysis revealed that during the initial take-off roll, a discrepancy in movement developed between the left and right elevators. Specifically, as the aircraft accelerated, the left elevator failed to move in unison with the right, reaching a maximum split of 8 degrees at 107 KIAS.
Technical analysis focused on the narrow clearance—between 0.15 and 0.25 inches—between the elevator leading edge and the stabilizer shroud. The investigation looked into whether contaminants could have entered this gap during the de-icing process or subsequent taxiing.
Findings
- A remnant of clear ice most likely migrated into the gap between the nose of the left-hand elevator and the stabilizer shroud when the elevator was moved to the trailing edge up position during control checks, causing the movement restriction during rotation.
- Existing de-icing procedures cannot entirely prevent the presence of undetected clear ice on critical surfaces that remain wet with de-icing fluid.
- Transport Canada guidance documents provided incomplete information regarding flight in freezing rain, potentially leading to differing understandings of hazards between ground and flight crews.