Operations of present day aircraft necessitates flying in all weather conditions plus the fact that high velocity air induced into the intakes means a provision must be made for ice protection. There are three systems of thermal anti-icing; hot air, hot oil or electrical There is, however, one disadvantage and that is the loss of engine power. This loss must be corrected for on ground runs and power checks.
ENGINE HOT AIR ANTI-ICING
The hot air system provides surface heating of the engine and/or power plant where ice is likely to form. The affected parts are the engine intake, the intake guide vanes, the nose cone, the leading edge of the nose cowl and, sometimes, the front stage of the compressor stator blades. The protection of rotor blades is rarely necessary, because any ice accretions are dispersed by centrifugal action. The hot air for the anti-icing system is usually taken from the latter stages of the HP compressor and externally ducted, through pressure regulation valves, to the parts requiring protection. When the nose cowl requires protection, hot air exhausting from the air intake manifold may be collected and ducted to the nose cowl. Exhaust outlets are provided to allow the air to pass into the compressor intake or vent to atmosphere, thus maintaining a flow of air through the system.