![]() ![]() The principal physiological problems are listed below. Pressurization of the cargo hold is also required to prevent damage to pressure-sensitive goods that might leak, expand, burst or be crushed on re-pressurization. On commercial aircraft, the cabin altitude must be maintained at 8,000 ft (2,438 m) or less. At altitudes above 15,000 ft (4,572 m), passengers are required to be provided oxygen masks as well. For private aircraft operating in the US, crew members are required to use oxygen masks if the cabin altitude (a representation of the air pressure, see below) stays above 12,500 ft (3,810 m) for more than 30 minutes, or if the cabin altitude reaches 14,000 ft (4,267 m) at any time. Pressurization becomes increasingly necessary at altitudes above 10,000 ft (3,048 m) above sea level to protect crew and passengers from the risk of a number of physiological problems caused by the low outside air pressure above that altitude. ![]() ![]() Need for cabin pressurization The pressurization controls on a Boeing 737-800 For increased passenger comfort, several modern airliners, such as the Boeing 787 Dreamliner and the Airbus A350 XWB, feature reduced operating cabin altitudes as well as greater humidity levels the use of composite airframes has aided the adoption of such comfort-maximizing practices. The Aloha Airlines Flight 243 incident, involving a Boeing 737-200 that suffered catastrophic cabin failure mid-flight, was primarily caused by the aircraft's continued operation despite having accumulated more than twice the number of flight cycles that the airframe was designed to endure. This increased airframe weight and saw the use of smaller cabin windows intended to slow the decompression rate if a depressurization event occurred. For example, the supersonic airliner Concorde had a particularly high pressure differential due to flying at unusually high altitude: up to 60,000 ft (18,288 m) while maintaining a cabin altitude of 6,000 ft (1,829 m). Improved testing involved multiple full scale pressurization cycle tests of the entire fuselage in a water tank, and the key engineering principles learned were applied to the design of subsequent jet airliners.Ĭertain aircraft have unusual pressurization needs. The causes were investigated and found to be a combination of progressive metal fatigue and aircraft skin stresses caused from pressurization. However, two catastrophic failures in 1954 temporarily grounded the Comet worldwide. The practice would become widespread a decade later, particularly with the introduction of the British de Havilland Comet jetliner in 1949. In the 1940s, the first commercial aircraft with a pressurized cabin entered service. The first experimental pressurization systems saw use during the 1920s and 1930s. The air is cooled, humidified, and mixed with recirculated air by one or more environmental control systems before it is distributed to the cabin. For aircraft, this air is usually bled off from the gas turbine engines at the compressor stage, and for spacecraft, it is carried in high-pressure, often cryogenic, tanks. For other uses, see Cabin Pressure (disambiguation).Īn airliner fuselage, such as this Boeing 737, forms a cylindrical pressure vesselĬabin pressurization is a process in which conditioned air is pumped into the cabin of an aircraft or spacecraft in order to create a safe and comfortable environment for humans flying at high altitudes. ![]()
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