Airframe Systems & Components: Ice & Rain Control Systems 🔊 Flashcards
Describe the operating principle of inflatable deicer boots.
Pneumatic deicing systems use rubber inflatable boots attached to the leading edge of the wings and stabilizers. Tubes are inflated with pressurized air and deflated in alternating cycles. It causes ice to break off and it is carried away in the airstream.
Why is it critical to prevent the formation of ice on aircraft wings and control surfaces?
Ice formation distorts the shape of the wing and air flowing over it, reducing aerodynamic lift. Ice weighs the aircraft down and adds stress.
What are two methods of inflating pneumatic deicer boots?
Pressurized air provided by an engine driven air pump (vacuum pump) or bleed air from the turbine engine compressor
What methods are used to attach deicer boots to leading edges of wings and tail surfaces?
Bonding to the surface with cement, fairing strips and screws, or a combination of both
What is the purpose of an air-oil separator in a pneumatic deicing system?
Removing the oil prevents deterioration of the rubber boots caused by contact with the oil
What is used to clean deicer boots?
A mild soap and water solution
What must be done before you can make a cold patch repair to a deicer boot?
Clean, rough the surface of the boot and patch, glue, and attach
What component of a pneumatic deicer system normally allows suction to be supplied to the boots to hold them down in flight?
The solenoid distributor valve
Describe the operating principle for thermal anti-icing systems.
Airfoils that need to be protected are usually provided with closely spaced double skin. Hot air passes through the space between skins and the heat is sufficient to prevent formation of ice or melt ice that is next to the skin. The heated air is supplied continuously when the system is on. Once used, the air is vented overboard through a hole in the leading edge.
How can you determine if the heater in a pitot is working?
Turn it on and feel for heat coming from it
What methods are used to supply heated air for thermal anti-icing systems?
Bleed air from the turbine engine compressor, engine exhaust heat exchangers, and ram air heated by a combustion heater
How is overheating prevented in a thermal anti-icing system using bleed air?
A thermal switch will cause a shut off valve to close and stop the flow of bleed air when the temperature of the leading edge reaches 185° F. When the temperature drops, the valve opens and the hot bleed air enters the wing again.
What is the purpose of the de-ice boot electrical timers?
To inflate the boots symmetrically. In the case of an electrical systems, the boots inflate individually to prevent excessive load on the electrical system.
In a thermal anti-icing system, what happens to the air after it has heated the leading edge of the wing?
The air is exhausted to the atmosphere at the wingtip and points where ice formation could be critical.
What problems are associated with electrically heated windshields?
Delamination, arcing, scratches, and discoloration
