The aircrafts have pressurized cabins because *
no change in atmospheric pressure
atmospheric pressure decreases with altitude
none
atmospheric pressure is high
Answers
Answer:
To recap, airplanes are pressurized because it protects pilot, crew and passengers from hypoxia. Airplanes are designed to pump air into the cabin to mimic the 14.7 pounds per square (PSI) of pressure that's found at sea level.
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Explanation:Cabin 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 passengers and crew flying at high altitudes. 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. The air is cooled, humidified, and mixed with recirculated air if necessary, before it is distributed to the cabin by one or more environmental control systems.[1] The cabin pressure is regulated by the outflow valve.
While the first experimental pressurization systems saw use during the 1920s and 1930s, it was not until 1938 that the Boeing 307 Stratoliner, the first commercial aircraft to be equipped with a pressurized cabin, was introduced. The practice would become widespread a decade later, particularly with the introduction of the British de Havilland Comet in 1949, the world's first jetliner. While initially a success, two catastrophic failures in 1954 temporarily grounded the worldwide fleet; the cause was found to be a combination of progressive metal fatigue and aircraft skin stresses, both of which aeronautical engineers only had a limited understanding of at the time. The key engineering principles learned from the Comet were applied directly to the design of all subsequent jet airliners, such as the Boeing 707.
Certain aircraft have presented unusual pressurization scenarios. The supersonic airliner Concorde had a particularly high pressure differential due to flying at unusually high altitude (up to 60,000 feet (18,000 m) while maintaining a cabin altitude of 6,000 feet (1,800 m). This not only increased airframe weight, but also saw the use of smaller cabin windows than most other commercial passenger aircraft, intended to slow the decompression rate if a depressurization event occurred. The Aloha Airlines Flight 243 incident, involving a Boeing 737-200 that suffered catastrophic cabin failure mid-flight, was primarily caused by its continued operation despite having accumulated more than twice the number of flight cycles that the airframe was designed to endure. 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-maximising practices.