How Modern Aircraft Air Conditioners Work

During a standard passenger flight, the aircraft air conditioner is responsible for providing a constant flow of fresh air that is at a comfortable temperature for passengers. Despite various rumors existing about aircraft air conditioning systems, fresh oxygen is constantly pumped into the cabin and air is thoroughly filtered to maintain a hygienic and microbe free cabin. As a modern marvel of aviation, learning how the aircraft air conditioning system functions can allow you to better understand how they are able to provide passengers with clean air at a comfortable temperature while traveling above 30,000 feet.

While there are a number of air conditioning systems available for aircraft, the most commonly used type for passenger turbine aircraft is the air cycle system. With this type, air is provided to the system through the routing of excess bleed air within the engines. As bleed air is extremely hot, it is initially fed into a heat exchanger that slightly lowers its temperature. Once it passes through the heat exchanger, the air is then sent through an air cycle machine so that it may be compressed. As compression causes the temperature of the air to rise again, the air is passed through a second heat exchanger and then into an expansion chamber which exhibits near-freezing temperatures. To ensure that the freshly cooled air is free of excess moisture, it is forced through a water separator. At this point, the air is nearly ready to be supplied to the passenger cabin, and it simply needs to flow through a mixing box to be heated as desired to ensure a comfortable cabin temperature.

With more recent aircraft models such as the Boeing 787 Dreamliner, air is drawn into the system directly from the outside air, rather than from the engine. As such, engine efficiency is increased while air can be pressurized and temperature treated by compressors. As a final deviation from the air cycle system, the Dreamliner also does not remove all the moisture from its treated air as the air conditioning equipment will automatically determine an optimal humidity value for the cabin. While aircraft may vary in their air conditioning equipment, almost all provide the same amount of airflow and fresh air to the cabin. During a typical flight operation, approximately half of the air within the cabin is fresh while the other half is recirculated. Despite being reused, such air is first forced through a series of HEPA filters which are capable of removing 99.999% of all viruses and bacteria. Additionally, specialty rooms of the aircraft such as the lavatory never have any air recirculated, and all old air is immediately vented from the lavatory and expelled from the aircraft.

With flights constantly varying in their carried passengers and flight locations, the temperature within the cabin may vary by operation. As such, temperature bulbs within the cabin are used to measure cabin temperature and relay data to the cabin temperature control panel. With the control panel, readings are then used to either increase or decrease the amount of hot bleed air and cold air that enters the mixing box. Through such a system, aircraft are also capable of providing heat to the cabin during colder winter months or in colder locations.

At ASAP Part Services, we serve as the premier purchasing platform for all your aviation needs. If you have been in search of air conditioning equipment for your aircraft, we carry a number of parts that cater to a diverse set of models and aircraft types. Explore our part database at your leisure, and our team members are readily available to assist you 24/7x365. Begin the part procurement process today and experience how we can serve you.