Air Conditioning and Pressurization Systems in Modern Aircraft

Airplanes flying at/about FL300 (30,000ft). Photo Credit: Bedhan Ball

For any modern aircraft to fly at high altitudes, it must be equipped with an air conditioning and pressurization system, which provides a convenient environment for its passengers. The human body is unable to withstand the effects of a low-pressure atmosphere, which makes the A/C and pressurization system a vital component of modern flight.

JAR-OPS 1.770 and 1.775 by the JAA, along with other regulatory authorities,  have established a minimum pressurization requirement for all modern aircraft which must be satisfied before an aircraft can fly.

Air Conditioning System on the Airbus A 320

Aircraft A/C systems are more or less similar on all modern airplanes. However, the following explanation of the system is specific to the A 320 Airbus. The system is fundamentally comprised of air conditioning packs, a pack flow control valve, a by-pass valve, pack controllers, and a mixing unit.

These components provide conditioned air via the following step by step process:

  • First, outside air enters the airplane engine.
  • Next, compressors within the engine compress this low-density air.
  • Hot compressed air from the compressor (bleed air) is then transported via ducts to the A/C packs.
  • Prior to entering the air conditioner units, the bleed air passes through the pack flow control valve, which regulates the flow of air entering the conditioning packs.
  • Within the A/C unit, two air-to-air heat exchangers are installed that supply outside air via a pack inlet scoop and the air exits through an outlet duct.
  • As the cold air exits from the conditioning pack, it is mixed with warm air.
  • The desired air temperature is achieved by regulating the amount of hot air mixed with the cold conditioned air exiting from the packs through a by-pass valve.
  • The regulated air is then fed to a mixing unit which transports the air further on into the cabin and the cockpit.
  • The by-pass valve, pack flow control valve, inlet scoop and outlet duct are all operated by, and connected to, a pack controller.
In the video below – that’s not smoke, it’s condensation due to the AC system.

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© Copyright 2012 Junaid Ali, All rights Reserved. Written For: Decoded Science


  1. Paul Kiang says

    We are interested to find out which are the largest air conditioning system suppliers to the aircraft industry. Our company has a disruptive technology that has been proven to effectively eliminate air-borne bacteria & viruses (mutated or otherwise) & harmful VOCs. This is the perfect solution to ensure the cleanest air circulation within the aircraft. This is the missing link that provide safe & healthy air transportation – if one does recall what happened during the SARs epidemic outbreak (then we have avian flu, MERS & the like, a never ending health problem)? If fact, this technology is government funded R&D efforts by top scientists in the field of nuclear fusion. It took our R&D team over 3 years to harness the technology and another 2 years to productize. It’s been proven with excellent efficacy with major installations in public mass transportation system…….

  2. says

    Assalamualeykum, amazing article.

    I teach science in India and this question was bothering me…and here I got my answers.

    Will look for more such interesting articles on decodedscience!

  3. djordje glusica says

    Will you be so kind to inform me who is manufacturer of pneumatic components for Air Conditioning System on the Airbus A 320. Who privede theoretical and on-job training course for that

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