Rotorcraft Flying Handbook, FAA-H-8083-21

depends on the temperature of the outside air. Air conditioning
provides better cooling but it is more complex
and weighs more than a ram air system.
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 helicopter
cabin through a pilot-controlled, bleed air valve.
ANTI-ICING SYSTEMS
Most anti-icing equipment installed on small helicopters
is limited to engine intake anti-ice and pitot heat systems.
The anti-icing system found on most turbine-powered
helicopters uses engine bleed air. The bleed air flows
through the inlet guide vanes to prevent ice formation on
the hollow vanes. A pilot-controlled, electrically operated
valve on the compressor controls the air flow. The pitot
heat system uses an electrical element to heat the pitot
tube, thus melting or preventing ice formation.
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.
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