Report: BAe ATP control problems following anti-icing

The Swedish Accident Investigation Board published the final report of their investigation into a serious incident involving a BAe ATP turboprop that suffered control problems following application of anti-icing fluid. The investigation revealed several similar incidents.

On January 11, 2010 a BAe ATP cargo aircraft was scheduled to fly from Helsinki (HEL), Finland to Copenhagen (CPH), Denmark. Owing to the prevailing weather conditions, the aircraft had undergone a two-step deicing prior to departure. In the two-step deicing procedure, hot water was mixed with glycol (Type I fluid) to remove ice, frost and snow from critical surfaces on the aircraft; after this, a fluid containing thickening agent (Type II/IV) was applied, to prevent ice from reforming.
At takeoff, the control column could not be pulled back when the rotation speed was reached, and the pilot felt that the elevator movement was restricted. Takeoff was aborted and the aircraft taxied back to the apron.
It was discovered that several similar incidents involving the same type of aircraft and similar conditions had occurred. The application of Type II/IV, combined with too narrow a gap between the stabiliser and elevator, were determining factors in the incidents.
The investigations also showed that the process for drawing up specifications and requirements for deicing fluids is, to a certain extent, controlled by trade organisations. The investigation found, too, that at present no monitoring or specific inspection activities relating to these fluids are carried out by any pan European aviation safety body. Neither is there any authorisation process, or any set certification rules, with regard to the types of aircraft which can/may use different types of deicing fluids.
The incidents involving elevator restrictions were caused by a phenomenon which, for unknown reasons, occurs following the use of anti-icing fluids containing thickening agents, on individual aircraft where the stabiliser and elevator are too close together. One contributory factor was the fact that there were shortcomings in that part of the aircraft’s type certification exercises that
concerned anti-icing.

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