• Created by: stonesy71
  • Created on: 05-11-19 11:01

What are the four fundamental requirements of

  • cabin conditioning/ECS System

  • Air supply and ventilation

  • Temperature control

  • Humidity

  • Purity

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In relation to the 3 air cycle cooling

  • principles, briefly describe the passage of air and any changes it incurs through the major components of an ECS

  • Surface heat exchange – Charge air is routed through a network of pipes which are within the ram air duct.  The ram air passes over these pipes extracting the heat from them.  This happens in the primary and secondary heat exchanger

  • Expansion – The charge air hits the compressor, this increases the pressure and temperature of the air, it then goes through a secondary heat exchanger where the temperature drops slightly.  It then hits the turbine where the air is expands as it goes through the turbine, meaning the pressure and temperature drop

  • Energy conversion – this also happens within the turbine, with the heat energy being converted to kinetic as it turns the turbine.

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What is the purpose of the ejectors fitted to a

 heat exchanger?

  • this will open at a predetermined speed to mitigate the lack of ram air.  It uses a jet pump to force air through the primary and secondary cooler, this effectively sucks more air though the cooler as a whole. 

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Describe the function and operation of the safety

valve for outward relief/inward relief and manual outwards relief conditions?

  • Outward relief - should the PCDV fail and pressure rises too much in cabin, the safety valve will open allowing air to bleed out.

  • Inward relief – during a rapid descent, there might be insufficient air entering the cabin through the PCDV. The safety valve will open allowing air into the cabin to prevent a negative cabin pressure differential.

  • Manual outward relief – should the RAM air valve be manually opened (in the event of smoke in cockpit), a valve in the RAM air valve causes pressure to drop in the top half of the safety valve, allowing the cabin pressure to overcome the spring pressure and lift the valve, venting cabin pressure.
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