Chapter Summary Anti-Icing Systems Engine Anti-Ice Airframe Anti-Ice Deicing  4-19 cause icing of rotor blades and fuselages, rendering them  unflyable until cleaned. Asymmetrical shedding of ice from  the blades can lead to component failure, and shedding ice  can be dangerous as it may hit any structures or people that  are around the helicopter. The tail rotor is very vulnerable to  shedding ice damage. Thorough preflight checks should be  made before starting the rotor blades. If any ice was removed  prior to starting, ensure that the flight controls move freely.  While in flight, for those helicopters that have them, deicing  systems should be activated immediately after entry into an  icing condition.  Piston-powered helicopters use a heat exchanger shroud  around the exhaust manifold to provide cabin heat. Outside  air is piped to the shroud and the hot exhaust manifold heats  the air, which is then blown into the cockpit. This warm air  is heated by the exhaust manifold but is not exhaust gas.  Turbine helicopters use a bleed air system for heat. Bleed air  is hot, compressed, discharge air from the engine compressor.  Hot air is ducted from the compressor to the bleed air heater  assembly where it is combined with ambient air through  and induction port mounted to the fuselage. The amount of  heat delivered to the helicopter cabin is regulated by a pilot- controlled bleed air mixing valve. This chapter discussed all of the common components,  sections, and systems of the helicopter. The chapter also  explained how each of them work with one another to make  flight possible.  Anti-icing is the process of protecting against the formation  of frozen contaminant, snow, ice, or slush on a surface.  The anti-icing system found on most turbine-powered  helicopters uses engine bleed air. Bleed air in turbine engines  is compressed air taken from within the engine, after the  compressor stage(s) and before the fuel is injected in the  burners. The bleed air flows through the inlet guide vanes  and to the inlet itself to prevent ice formation on the hollow  vanes. A pilot-controlled, electrically operated valve on the  compressor controls the air flow. Engine anti-ice systems  should be on prior to entry into icing conditions and remain  on until exiting those conditions. Use of the engine anti-ice  system should always be in accordance with the proper RFM. Airframe and rotor anti-icing may be found on some larger  helicopters, but it is not common due to the complexity,  expense, and weight of such systems. The leading edges of  rotors may be heated with bleed air or electrical elements to  prevent ice formation. Balance and control problems might  arise if ice is allowed to form unevenly on the blades. Research  is being done on lightweight ice-phobic (anti-icing) materials  or coatings. These materials placed in strategic areas could  significantly reduce ice formation and improve performance. The pitot tube on a helicopter is very susceptible to ice and  moisture buildup as well. To prevent this, they are usually  equipped with a heating system that uses an electrical element  to heat the tube. Deicing is the process of removing frozen contaminant,  snow, ice, and/or slush from a surface. Deicing of the  helicopter fuselage and rotor blades is critical prior to starting.  Helicopters that are unsheltered by hangars are subject  to frost, snow, freezing drizzle, and freezing rain that can 