As you can see, this creates quite the quandary. So, airplane manufacturers created a cabin pressurization system to keep passengers and employees safe and comfortable while in the air.
But how aircraft cabin pressure works can be a little confusing. So, we're answering a few of the most common questions that arise when discussing the ins and outs of aircraft pressurization. The answer to this first question is a little complex as it can vary across aircraft manufacturers, so let's dive in.
Older piston-powered airliners used to use electric air compressors to pump outside air into the cabin of the airplane. However, this tended to add a lot of extra weight to the aircraft. Jetliners then began to use bleed air from the engines to spin the turbo compressors, which then pumped outside air into the cabin. Today, most modern airplanes use bleed air from the engines' compressors to properly pressurize the cabin. The engine's compressor contains a series of spinning blades that draw in fresh air from outside the plane.
The air becomes extremely hot as it's compressed. It then enters the engine's combustion chamber where it combines with fuel and is burned. Then, the expanded gasses flow through the engine's turbine blades powering the compressor blades and exit the engine, creating thrust.
The bleed air, which is clean, hot air, is taken from the compressor prior to mixing with any fuel or exhaust gasses. Bleed air can help with the following:. While some of the already-hot bleed air is used for things like wing deicing, cabin-bound bleed air must be cooled first. Since then, cabin pressurization has become one of those technologies that most of us who fly probably take for granted. Cabin pressurization works so well that passengers barely even notice it, in part because it gradually adjusts the air pressure inside the plane as it climbs in altitude, and then adjusts it again on the way down, explains Chuck Horning.
He's been an associate professor in the aviation maintenance science department at Embry-Riddle Aeronautical University in Daytona Beach, Florida, since and before that, a mechanic and maintenance instructor at Delta Airlines for 18 years. Essentially, the aircraft uses some of the excess air that's pulled in by the compressors in its jet engines. The excess air from the compressors is cooled, and then pumped into the cabin. It's regulated by a device called the air cabin pressure controller, which Horning describes as "the brains of the pressurization system.
It schedules the pressurizing so that as the airplane climbs and the external pressure goes down, it goes to work. Pressurizing an aircraft too much could put its fuselage under too much stress from differential pressure as the plane climbs, Horning says. To avoid that, airliners don't try to duplicate the air pressure at sea level. Instead, at a cruising altitude of 36, feet 10, meters , most commercial jets simulate the air pressure at an elevation of 8, feet 2, meters , about the same as Aspen, Colorado.
The Boeing Dreamliner , which has super-strong carbon fiber in its airframe, is able to get that down to the equivalent of air pressure at 6, feet 1, meters. How much air needs to be added to pressurize depends on the volume of the cabin, Horning says. Even while at sea level, one can experience this when ears pop while riding an elevator. In mountainous terrain, people new to the elevation may have difficulty breathing during exertion, or feel dizzy while driving up a mountain.
You may have seen footage or images of fighter pilots or high-altitude jet pilots wearing masks in the cockpit. This is the point at which human beings require oxygen in order to function—adults will only last about half an hour without it before losing consciousness.
Since most large passenger jets and turbojets fly between 30, and 43, feet above sea level, pressurization is required; a person would remain conscious without it for less than a minute, as he or she would be experiencing about 4 psi. In addition, airlines and pilots want to provide as smooth a ride as possible for their passengers.
Violent thunderstorms and air pockets swirl at the lower edges of the atmosphere. Not only does turbulence upset nervous fliers, it endangers flight attendants who may be moving about the cabin, carrying extremely hot beverages. Turbulence can also, over time, begin to wear on the airframe and control surfaces of an aircraft.
It disrupts passengers who might be attempting to sleep or work. Turbulence aside, flying higher means flying faster. This also means that less fuel is necessary and the airplane can carry more passengers and cargo. Cheaper and faster are always goals in the airline industry. There is also an engineering and physics reason behind flying over 30, feet: Airplane engines are designed to work at this altitude. Pressurized cabins are usually maintained between 11 and 12 psi.
The pressurization within an aircraft is what enables the passengers and crew to breathe comfortably and retain consciousness. Pressurization systems are designed to continually replace interior air with air from outside the plane. This takes place at the outflow valve or valves, which can be found in the aft section of the airplane. Outflow valves are mechanized and auto-controlled.
Bleeding starts with the ears and nose because those are the smallest places in your body that trap gas; blood can also come out of your oral cavities. If the conditions persist, the effects could eventually spread, possibly causing cardiovascular or lung issues. Of course, the chances of you experiencing a life-threatening shift in barometric pressure while flying are rare. In fact, was dubbed the safest year of air travel with no commercial passenger deaths — a significant improvement from when there were over 1, deaths on commercial air carriers.
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By choosing I Accept , you consent to our use of cookies and other tracking technologies. Reddit Pocket Flipboard Email. A Jet Airways cabin crew forgot to pressurize the cabin, resulting in passenger nosebleeds and ear pain.
Getty Images The never-ending nightmare that is commercial flying just added a rather horrifying new potential mishap to its roster.
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