Why Are Aircraft Cabins Pressurized?

When riding in passenger aircraft that travel upwards of 30,000 feet or more, the surrounding atmosphere is often extreme in its conditions. From very low temperatures to air pressure values well below safe breathing limits, humans are unsuited for such high altitudes. Despite this, passengers most often only face some lighter side effects such as a dry mouth and popping ears throughout a flight. This is due the fact that aircraft cabins are specifically designed to create an environment that is closer to that of sea level, and this is achieved through aircraft pressurization.

While conducting flight operations at lower altitudes can alleviate the risks associated with depressurization, maintaining such high altitudes can be much safer when accounting for the many obstructions that may create flying hazards such as mountains. Above the tallest peaks at around 14,000 feet, many storms and air pockets may be produced and swell, causing aircraft moving through them to have to deal with high amounts of turbulence. While fairly safe to operate in, such conditions are hardly enjoyable to passengers who would like to sleep, work, or relax, and thus the high altitudes that airliners operate at serve as the best height for avoiding safety hazards while also achieving fuel efficiency and increased speed that come with more height.

Within a typical passenger aircraft, pressure is often kept at a value between 11 and 12 psi which is closer to sea level. While pressurization is achieved through various mechanical means, sealing a fuselage completely is impossible while ensuring a steady flow of fresh oxygen. As such, pressurization is typically achieved through a pressurization system known as an environmental control system.

With outflow valves, old air within the cabin can be expelled as needed to bring in fresh air. As an outflow valve is auto-controlled and mechanized, it will automatically open and allow for air to be removed in a very controlled manner. To bring in fresh air at a pressure safe for passengers, air is captured by the engine and undergoes pressurization within the compressor, and some of this air is taken from the engine before combustion and routed towards the cabin. While this air is also used by de-ice systems and other devices, much of the air is separated and routed through intercoolers, air packs, and expansion turbines to reach a temperature and pressure that is most comfortable for breathing.

Similar to a balloon that is consistently inflated and deflated, the process of expelling air and replacing it with fresh, pressurized air is continuous throughout the flight for hygienic and safety purposes. Before conducting a flight, the pilots will utilize the cabin pressure controller that allows them to set a cruise altitude. As such, changes in pressure within the aircraft cabin are at a much slower rate as compared to outside atmospheric pressure. When landing, the pilots will utilize the cabin pressure controller again, this time ensuring that pressure increases gradually to acclimate passengers to their destination in a more comfortable fashion.

With functional air pump parts, outflow valves, and other environmental control system components, managing the pressure within an aircraft can be done safely and efficiently. At Aerospace Buying, we are a premier online distributor of aviation parts offering customers competitive pricing on over 2 billion new, used, and obsolete items. With AS9120B, ISO 9001:2015, and FAA AC 00-56B certification and accreditation, we ensure that every component is of the highest quality and ships alongside its qualifying certifications or manufacturing trace documents. If there are particular items from our website that you would like to procure, fill out and submit an Instant RFQ form as provided on our website and a dedicated account manager will reach out to you in 15 minutes or less with a personalized quote.


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March 22, 2021

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