During the flight,on the surface of various parts of the aircraft is formed ice, which is a source of danger. Icing reduces lift and increases drag of aircraft,interferes operation of controls, adversely affects the operation of the engine, impairs visibility and creates a separate load. Accordingly, the protection against ice formation is one of the important functions of flight safety and anti-icing systems are required.
The formation of ice on the surface of aircraft is typical in general, only for the fore surface that is flown by air. Accordingly, the means of de-icing should be placed in these areas.
The main means of anti-icing are thermal methods, based on the heating of aircraft surface to the temperature that prevents ice formation. Depending on the heating mean there are electrothermal and bleed air systems .
Thermal-electric systems provide surface heating of aircraft periodically with some intervals. Thus, ice that had formed, begins to melt and is blown away by air. After melting of the ice, surface temperature decreases and ice forms again. Repeated heating saves electricity.
An important thing in protection against ice formation is the place where engine intakes air. Since the formation of ice and getting of its pieces inside the engine can adversely affect its operation. For heating of inlet bleed air method is used (Fig.189). Warm air from the high pressure compressor is fed into the heating system.
Separately, electrothermal heating is provided for: windshields, angle of attack sensors, receivers of total of static pressure.
Anti-icing system comprises avionics equipment, which controls the presence of ice with the help of special sensors and ensures its removal (Fig. 190).
Fig. 189 . Heating system of inlet