Commercial and Business Aviation Advisory Circulars

Ground De-Icing/Anti-Icing Of Aircraft With The Main Engines Running

PURPOSE

This Air Carrier Advisory Circular is intended to encourage air carriers to allow their aircraft to be de-iced/anti-iced with the main engines running, where technically feasible; to describe, as part of their Ground Icing Operations Program, the procedures to be followed for each aircraft type; and to train their operational personnel in the proper use of these procedures.

BACKGROUND

In order to improve the speed and efficiency of de-icing/anti-icing operations, to reduce departure delays during adverse weather, and to maximize the use of hold-over times, the Commission of Inquiry into the Air Ontario Crash at Dryden, Ontario, made the following recommendation in MCR 80:

"Transport Canada encourage air carriers to adjust their operational procedures and policies, where technically feasible, to permit the de-icing of an aircraft with a main engine running."

A Dryden Commission Implementation Project Task Group, which included representatives from government and industry, was responsible for making proposals for the implementation of this recommendation. It has proposed that information be provided to air carriers on the de-icing/anti-icing of aircraft with the main engines running and that air carriers be encouraged, where technically feasible, to develop the necessary procedures for each aircraft type.

DETAILS

Aircraft and engine manufacturers, including McDonnell Douglas, Boeing, Bombardier, Rolls-Royce, Canadair, Airbus, and Fokker, have published information on the advisability of de-icing/anti-icing with the main engines running and, when they permit it, have outlined procedures to be followed in order to protect the engines, the aircraft systems, and the personnel conducting the treatment. These procedures are based on engineering tests and the experience of those air carriers who routinely de-ice/anti-ice their aircraft with the main engines running.

Experience shows that problems can be minimized if precautions are taken to limit the ingestion of de-icing/anti-icing fluid by the engines. The following procedures, which must be adapted to the specific aircraft type, were developed to protect the aircraft during de-icing/anti-icing with the main engines running.

1. Operate as few engines as possible during the de-icing process;
    
2. Operate at the lowest practicable power setting;
    
3. If possible select air conditioning 'OFF';
    
4. Avoid spraying fluid directly into the engine, APU, and air conditioning system intakes;
    
5. Avoid a large run-off of fluid from adjacent surfaces into the intakes, e.g., from a vertical stabiliser into a tail-mounted engine or APU;
    
6. Minimize the generation of spray in the vicinity of the intakes.

Even in cases where substantial ingestion of fluid has occurred due to accident or mishandling, there was no observable adverse effect on the engines. If, contrary to the above procedures, the air conditioning is on during the de-icing/anti-icing treatment, the passenger cabin may fill with smoke, but investigations show that even in the worst ingestion case, the possibly toxic elements are at concentrations well below hazardous levels. However, there is some evidence that residues may accumulate in the air conditioning system and result in malfunctions.

Particular care should be exercised for the APU inlet because fluid ingestion could cause an APU runaway condition or, in an extreme case, an APU rotor burst.

It has been found that, for those aircraft types for which it is technically feasible, if proper procedures are followed, de-icing/anti-icing of aircraft with their main engines running is safe for both the aircraft and de-icing/anti-icing personnel. It is understood that there are aircraft types for which de-icing/anti-icing with the main engines running is not advisable.

CONCLUSION

If procedures for de-icing/anti-icing aircraft with their main engines running are clearly described in the applicable operations manuals and the operational personnel involved are adequately trained in the use of these procedures, it is not necessary for the main engines of most aircraft to be shut down before de-icing/anti-icing.

It must be emphasized that the above-noted procedures are to be used only if they have been approved by the manufacturer.

A.J. LaFlamme
Director
Air Carrier