Occurrence
On 04 November 2003, Air Canada Jazz Flight 8946, a de Havilland DHC-8-102 (registration C-GONJ, serial number 095), was scheduled to fly from Ottawa/Macdonald-Cartier International Airport, Ontario, to Montréal International Airport (Dorval), Quebec. The aircraft carried 19 passengers and a crew of three.
Pre-Flight and De-Icing
The aircraft had been in Ottawa overnight and had operated a round-trip to Toronto City Centre Airport earlier that day. The return flight landed at Ottawa at approximately 1053 eastern standard time. Freezing rain was encountered below 5000 feet on the approach, and some ice accumulated. The aircraft remained parked outside for about 2 hours 30 minutes, during which light and moderate ice pellets, light freezing rain, and light rain fell.
Before boarding Flight 8946, the crew observed ice on critical surfaces, the nose, propellers, and icicles on the trailing edges of wings and the horizontal tail. Light ice pellets and light freezing rain were falling. Before engine start, the propellers were de-iced with Type I freezing point depressant fluid. Engines started at 1318, and the aircraft taxied to the de-icing ramp at 1324. Due to an aircraft ahead and a shift change, de-icing was delayed about 30 minutes.
De-icing with Type I fluid occurred between 1353 and 1408. The aircraft was parked on a heading of 140 degrees magnetic. During de-icing, a crosswind from the left was present: 070 at 15 knots, gusts to 20 knots. Two trucks were used: initially positioned on either side of the fuselage behind the wings and in front of the tail. The left-side truck de-iced the left wing; the right-side truck de-iced the right wing. The left truck then moved to the nose to remove ice from the previous flight, while the right truck remained and de-iced both sides of the horizontal stabilizer and elevators. Upon completion, de-icing personnel saw no ice on any aircraft surfaces. No precipitation fell during de-icing or taxi.
Rejected Take-Off
After de-icing, the crew left the pad at approximately 1408 and taxied to Runway 07. Normal pre-take-off checks were performed, including a control check by the pilot not flying (PNF). The take-off run began at 1412. When attempting to rotate, the pilot flying (PF) felt a restriction to aft movement of the control yoke and rejected the take-off. After clearing the runway, a control check revealed no restriction.
Post-Event Inspection
The aircraft returned to the ramp. A 30-minute delay occurred before a gate assignment, during which freezing rain resumed. A maintenance technician verified elevator controls were free and moving correctly, then inspected the top surface of the horizontal stabilizer. Freezing rain drops and residual de-icing fluid were found, but no large pieces of ice. The aircraft was de-iced again and proceeded to Montréal.
Weather and De-Icing Details
Ottawa airport weather reports indicated light ice pellets, rain, and freezing rain during the ground period. No precipitation was recorded between 1339 and 1453, then light freezing rain resumed. At the time of the rejected take-off, wind was 070°T at 15 knots gusting to 20 knots, temperature −2°C, no precipitation.
De-icing was performed by Air Canada using two Global model 2110TE-EC-AP trucks. Each truck had a driver and boom operator, overseen by a de-icing lead. Manning, qualifications, training, and procedures followed the Air Canada Jazz Ground Icing Program manual and the company operations manual. A total of 503 litres of Type I fluid was used, reportedly more than average but not inconsistent with exposure.
Flight Crew and Aircraft
Both pilots held airline transport pilot licences, were appropriately qualified, and had received surface contamination training. They had adequate rest. The aircraft was maintained per regulations with no outstanding issues. It was equipped with a cockpit voice recorder (CVR) and flight data recorder (FDR). The CVR was overwritten on the subsequent flight and unavailable.
FDR Data
FDR data (one sample per second) indicated: during the control check after the rejected take-off, the elevators moved from fully trailing edge down to near fully trailing edge up and back to neutral in less than three seconds. Full elevator travel is 20° down to 20° up. A split of approximately 4° developed between left and right elevators during lateral control checks and remained until returned to full down.
At the start of the take-off run, both elevators moved to about 7.5° down at 45 KIAS. As speed increased, a split developed: the left elevator essentially did not move while the right elevator moved up to 2.2° up. The maximum split was 8° at 107 KIAS. After rejection, as the aircraft decelerated through 65 KIAS, the right elevator went full down while the left hung at about 10° down for 10 seconds. At 50 KIAS, both elevators moved abruptly to about 15° up and back to full down, consistent with the PNF locking controls per rejected take-off procedures.
During the subsequent take-off (no elevator restriction), both elevators moved progressively to about 1.5° down at 45 KIAS and to 1.5° up by 65 KIAS, remaining until rotation at 98 KIAS when both moved to over 10° up.
Aircraft Systems and Regulations
Dash 8 pitch control uses manually operated, spring-tab assisted elevators attached behind the horizontal stabilizer with a clearance of 0.15 to 0.25 inches. Left and right elevators have independent mechanical circuits interconnected at the control columns, with a disconnect system. Control inputs are transmitted through cables, pulleys, bellcranks, push rods, torque tubes, and torsion springs. No cockpit indication of elevator position or split exists.
The aircraft is certified under FAR 25.1419 for flight in icing conditions when operated per the Aircraft Flight Manual (AFM). The AFM contains warnings about severe icing and provides recognition and procedure guidance. A manufacturer service letter notes the need for clean critical surfaces and the possibility that dehydrated anti-icing fluid residue can accumulate in the gap between control surface and shroud, potentially causing jams if rehydrated and frozen.
Canadian Aviation Regulation (CAR) 602.11 prohibits take-off with frost, ice, or snow on critical surfaces. Air Canada Jazz complies through its ground icing program in the COM and Ground Icing Program manual.