SERVICING OF CHEMICAL DE-ICING SYSTEMS:
It is essential for the correct operation of the ice protection system that servicing is carried out on a regular basis. The fluids used in these systems are based on:
- Isopropyl alcohol
- Phosphate compounds
Isopropyl alcohol is flammable and must therefore be treated with great care. Both the fluid types are prone to solidifying in to a jelly type substance if left on the blades the resulting deposits will build up and eventually obstruct the distribution nozzles and the overshoe grooves. This will lead to uneven distribution, or no distribution at all, of the de-icing fluids.
The commonly accepted method of keeping the de-icing pipes clear is to flush the system using methylated spirit and distilled water as follows. This is a general procedure and not specific to any aircraft type. Always refer to the aircraft AMM for the correct procedures.
- Fill the tank with the above mixture.
- Operate the pump observing any time limitation on the motor.
- Turn the propeller by hand until the fluid is seen to emerge from the delivery nozzles.
- Empty the tank through the nozzles to ensure sufficient cleaning fluid has passed through the system.
- Clean the blades with methylated spirit or warm soapy water, paying particular attention to the grooves in the overshoes.
- If the system is to be left empty it should be inhibited according to the manufacturer's instructions.