DH8A, Ottawa Canada, 2003
DH8A, Ottawa Canada, 2003
On 04 November 2003, the crew of a de Havilland DHC-8-100 which had been de/anti iced detected a pitch control restriction as rotation was attempted during take off from Ottawa and successfully rejected the take off from above V1. The Investigation concluded that the restriction was likely to have been the result of a remnant of clear ice migrating into the gap between one of the elevators and its shroud when the elevator was moved trailing edge up during control checks and observed that detection of such clear ice remnants on a critical surface wet with de-icing fluid was difficult.
On 04 November 2003, a de Havilland DHC-8-100, operated by Air Canada Jazz, was on a scheduled flight from Ottawa/Macdonald-Cartier International Airport, Ontario, to Montréal International Airport (Dorval), Quebec, with 19 passengers and a crew of three. After deicing, the aircraft taxied to Runway 07 and was cleared for take-off. The crew carried out normal pre-take-off checks and commenced the take-off run. On rotation, the pilot felt a restriction to movement of the pitch controls and, as a result, the pilot rejected the take-off.
Upon returning to ramp, the crew moved the elevator controls through their full range of movement and found them free of restriction. The aircraft returned to the gate where maintenance inspected the aircraft and found the controls operating properly and free of restriction. Some freezing rain drops and residual de-icing fluid were found on the horizontal stabilizer and the elevator surfaces, but there were no large pieces of ice. The aircraft was de-iced again and proceeded to Montréal.
The investigation led by TSB Canada concluded that the data, provided by the Flight Data Recorder (FDR), indicated that something had physically interfered with movement of the left elevator -developing an elevator split during the take-off: “At the beginning of the take-off run, both elevators moved in unison to approximately 7.5° trailing edge down at 45 kts indicated airspeed (KIAS). As the aircraft accelerated, a split developed, the left elevator essentially not moving while the right elevator continued to move trailing edge up to a maximum of 2.2° up. The maximum split was 8° at 107 KIAS.”
In the absence of a mechanical problem or other foreign object in the flight control system, the investigation focused on icing. Ottawa airport weather reports indicated that precipitation, in the form of light ice pellets, rain, and freezing rain, fell during the period that the aircraft was on the ground. The weather recorded at the time of the rejected take-off was as follows: wind 070° at 15 knots with gusts to 20 knots; temperature -2°C, and no precipitation.
The investigation came to the following finding as to causes and contributing factors:
“A remnant of clear ice most likely migrated into the gap between the nose of the left-hand elevator and the shroud at the rear of the stabilizer when the elevator was moved trailing edge up during control checks and interfered with movement of the elevator when the pilot attempted to rotate for take-off.”
A finding, related to risk, was also outlined:
“Existing defences cannot preclude the presence of undetected remnants of clear ice on an aircraft critical surface that is wet with de-icing fluid after de-icing. This ice may interfere with control movement during take-off and result in the pilot rejecting the take-off in aircraft without power controls; resulting in risk of severe injury or major damage for operations where decision speed (V1) is less than rotation speed (Vr) and the aircraft cannot stop on the remaining runway.”
No Safety Recommendations were made in the report.
- Transportation Safety Board of Canada - Report A03O0302