What happened
On 28 November 2005, a Dornier 328-110, registration D-CPRW, was preparing for a passenger flight from Isle of Man (Ronaldsway) Airport. Prior to departure, the aircraft surfaces were covered in hoar frost, necessitating a de-icing and anti-icing procedure. A ground handler applied a heated mixture of Type II+ fluid and water to the wings and tail surfaces.
During the takeoff roll on Runway 26, the aircraft reached its calculated rotation speed of 109 kt. Upon the commander applying aft control column input, the aircraft failed to respond with the expected pitch. Realising the lack of elevator effectiveness, the commander immediately retarded the power levers to idle and applied heavy braking, successfully bringing the Dorn and 328-110 to a stop on the runway. There were no injuries to the 16 passengers or 3 crew members, and no damage was sustained by the aircraft.
The investigation
The AAIB investigation examined the flight data, cockpit voice recordings, and the de-icing process. Analysis of the flight data recorder revealed that the aircraft was rotated significantly before the prescribed rotation speed. While the elevator movement was checked and found to be free and unobstructed during subsequent taxi checks, the investigation focused on the aerodynamic state of the tail surfaces.
Investigators noted that the de-icing fluid residue on the horizontal tailplane suggested that the leading edge of the lower surface had not been adequately covered. This was attributed to the application method, where the fluid was sprayed from the trailing edge toward the leading edge, rather than the recommended direction.
Findings
- The crew selected a V1/VR speed of 109 kt, which was the standard speed for non-icing conditions.
- Because the aircraft had been treated with thickened Type II+ fluid, the correct takeoff speeds should have been those designated for icing conditions, which would have been 128 kt.
- The incorrect V1/VR speed was selected.
- Contamination of the leading edge of the lower horizontal tailplane surface, likely consisting of either ice or thickened de-icing fluid, prevented the aircraft from rotating.
- The application of de-icing fluid from the trailing edge toward the leading edge likely left the critical lower leading edge of the tailplane unprotected.