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airplane cabin pressure

Asked by: 4834 views Aircraft Systems

what is airplane cabin pressurization


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3 Answers

  1. Jim Foley on Sep 15, 2012

    http://www.google.com Pressurization is such a big topic, I suggest you do some basic research first, then come back and ask more specific questions that you may have.

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  2. John D. Collins on Sep 15, 2012

    The density of the air decreases as you climb in altitude. Pilot’s and passengers need sufficient oxygen to breath as the airplane climbs. Between 12,500 feet and 14,000 feet cabin altitude, supplemental oxygen is required for the pilot if they remain at these altitudes for more than 30 minutes. The flight crew is required to use supplemental oxygen any time the cabin altitude is above 14000 feet and passengers are required to use supplemental oxygen with a cabin altitude above 15,000 feet. In most GA airplanes the cabin altitude and the actual altitude are the same, as the cabin is not pressurized. For more sophisticated airplanes that cruise at high altitudes, the cabin is pressurized by an air compressor that fills the cabin with air at a pressure higher than the outside air pressure. In this case, the portion of the aircraft that contains the cabin is sealed against air leaks. Usually the air compressor provides more air pressure than is needed, so an outflow valve opens and closes to maintain a particular cabin pressure (or cabin altitude). Each pressurized cabin is able to maintain an internal pressure differential with respect to the outside air pressure, so for an example, if one airplane can maintain a 3 PSI differential and another can maintain a 8 PSI differential, the latter aircraft system will be able to maintain sea level pressure in the cabin to a higher actual altitude. A system with a 3 PSI differential can maintain a cabin altitude of 12,000 feet at 25,000 feet, whereas a system with a 8 PSI differential can keep the cabin altitude down to 8,000 feet well up into the thirty thousand foot level. An 8 PSI system requires a stronger cabin than a 3 PSI system due to the higher forces on every square inch inside the cabin. Of course, not having to wear an oxygen mask to fly at high altitudes is a great advantage of a pressurized cabin.

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  3. Wes Beard on Sep 15, 2012

    Simply put, cabin presurization is the process of forcing air into the cabin so that the occupants of the aircraft due not have to wear oxygen masks at higher altitudes.

    You may recall that air pressure drops roughly 1″ Hg every 1000 feet of altitude above sea level. At some altitude (typically around 12,000 to 14,000 FT MSL), the pressure of the air is so low that the body has trouble bonding the oxygen to the hemoglobin inside the blood cells. When this starts to happen, we say that person is experiencing hypoxia (more correct is hypoxic hypoxia).

    Cabin pressurization forces air into the cabin so that the pressure INSIDE the cabin remains at a higher pressure and as such the occupants should not experience hypoxia.

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