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Air Conditioning
Heating and ventilation of the (unpressurised) cabin, bleed-air/combustion heaters and vapour-cycle cooling.
Air conditioning — summary notes
FreeMain ideas
- Most helicopters are UNPRESSURISED, so 'air conditioning' means heating and ventilation rather than a pressurisation pack; cabin comfort is managed with fresh-air vents and a heating source.
- Heating is provided by engine BLEED AIR through a heat exchanger, or by a separate combustion heater on piston/some turbine helicopters; a cracked heat source is a carbon-monoxide risk, as on a piston aeroplane.
- Where cooling is fitted it is usually a VAPOUR-CYCLE (refrigerant) air-conditioning system rather than the air-cycle machine used on pressurised jets.
- Temperature and airflow are controlled by mixing/valve arrangements; demist air is supplied to the windscreen.
- Because there is no pressurisation, there is no cabin-altitude control, outflow valve or differential-pressure limit to manage.
- ⚠ Exam trap: helicopters are generally UNPRESSURISED — air conditioning is heating/ventilation (bleed-air or combustion heater), and any cooling is usually a vapour-cycle system, NOT an air-cycle pressurisation pack.
Solved examples
Why does a typical helicopter not have an air-cycle machine and outflow valve like an airliner?
An air-cycle machine and outflow valve exist to cool and control the pressure of a pressurised cabin. Helicopters generally operate at low altitude and are unpressurised, so there is no cabin differential pressure to manage. Comfort is handled by simple ventilation and a heater (bleed-air or combustion), with a vapour-cycle cooling system if cooling is needed.
Air conditioning concept map
FreeAir Conditioning
Air conditioning quiz
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