Why Cabin Pressurization is Important

          In general, a majority of aircraft operate in high altitude conditions, often ranging from 31,000 to 38,000 feet. At such heights, temperatures and the density of oxygen can be dangerously low, presenting a risk to anyone without sufficient protection. Despite this, most passengers and aircraft operators never worry about the comfort of breathing or the extreme cold during typical flights. This is because of cabin pressurization, allowing for passengers, pilots, and crew to safely travel in aircraft at high altitudes. In this blog, we will discuss what cabin pressurization is, how it is achieved, and how it benefits all of those on an aircraft during flight.

            In general, the more than one travels upwards into the atmosphere, the less pressure there is acting upon them. Subsequently, air molecules also become more spread apart the higher one goes, causing each breath to take in less oxygen. At 18,000 feet, pressure is low enough to become lethal to most humans after a short period of time. Despite this, aircraft operate at altitudes that can double this height, and thus systems need to be in place to maintain a level of pressure that is closer to sea level. To achieve such a result, many aircraft have air pumped into the sealed cabin, ensuring the comfort of all aboard.

            When designing aircraft fuselages, they are built to be able to withstand a decent amount of differential pressure, allowing for the inside of the aircraft to stay at a base cabin air pressure regardless of the changes of air pressure on the outside. While one may think that the fuselage is completely sealed, such an endeavor would prove nearly impossible and would cause the amount of fresh air to quickly deplete. Instead, an air outlet door called an outflow valve is placed near the tail end of the fuselage, allowing for old air to exit the aircraft. Larger aircraft may have two of these outflow valves, and valve operation is typically controlled automatically by the aircraft pressurization system. When the pressure of the cabin needs to be higher than the outside pressure, the outflow valve restricts air from escaping, and the door can slowly open as needed to reduce pressure. Because of this, the outflow valve serves as a highly simplistic aircraft system despite its crucial role.

            While the air outlets allow for old air to escape the aircraft cabin, there also needs to be a method to filter air and provide new, fresh oxygen for passengers. To supply clean air to the cabin, a number of methods may be used, often depending on the type of aircraft. On old piston powered aircraft, electric air compressors may be used to bring outside air into the aircraft, though they are typically very heavy. With early jetliners, bleed air from the engine is fed to turbocompressors in order to rotate turbine blades, and the turbocompressors bring fresh air into the fuselage. With most modern aircraft, bleed air is now provided by the engine compressor in order to pressurize the cabin and provide clean, breathable air for passengers. As this air comes from the engine, however, it is cooled down before it is comfortable for passengers.

            As establishing a base cabin air pressure that is safe for passengers can cause a great pressure differential between the aircraft interior and exterior, it is important that certain devices are put in place in order to protect parts. With positive pressure relief valves, excess air pressure can be vented from the fuselage when limits are exceeded. Negative pressure differential relief doors are also used to protect the fuselage from damage when the outside pressure is greater, such as when conducting a rapid descent. When the pressure exerted on the outside of the components drops below a set limit during descent, the doors will swing inwards to allow for pressurized air to enter the aircraft.

            With the various systems and devices put in place, aircraft and pilots can easily control pressurization in order to safely and comfortablY travel at high altitudes. When you are in need of cabin pressurization systems and components for your aircraft, let the experts at Sourcing Streamlined assist you with rapid lead-times and competitive pricing on all that we carry. Sourcing Streamlined is a premier distributor of aviation parts, and customers can find air filter parts, turbine components, AC compressor systems, and much more. Get started today by filling out and submitting an Instant RFQ form and receive a personalized quote in 15 minutes or less.


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April 22, 2021

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