Editing Bleed air (section)

==Uses==
[[File:Cabin pressure and Bleed air control panels on a Boeing 737-800.jpg|thumb|right|upright|Cabin pressure and bleed air controls in a [[Boeing 737-800]]]]
[[File:ECSB737-300ENGINES ON.svg|thumb|right|Environmental control system (ECS) schematic of [[Boeing 737-300]]]]

In civil aircraft, bleed air's primary use is to provide pressure for the aircraft [[cabin (aircraft)|cabin]] by supplying air to the [[environmental control system]]. Additionally, bleed air is used to keep critical parts of the plane (such as the wing [[leading edge]]s) ice-free.<ref name="skybrary">{{cite web | url=http://www.skybrary.aero/index.php/Bleed_Air_Systems | title=Bleed Air Systems | publisher=Skybrary.aero | access-date=January 1, 2013}}</ref>

Bleed air is used on many aircraft systems because it is easily available, reliable, and a potent source of power. For example, bleed air from an airplane engine is used to start the remaining engines. [[Aircraft lavatory|Lavatory]] water storage tanks are pressurized by bleed air that is fed through a [[pressure regulator]].<ref name="skybrary" />

When used for [[cabin pressurization]], the bleed air from the engine must first be cooled as it exits the compressor stage at temperatures as high as {{cvt|250|°C|sigfig=1}} by passing it through an air-to-air [[heat exchanger]] cooled by the cold outside air. It is then fed to an [[air cycle machine]] unit that regulates the temperature and flow of air into the cabin, keeping the environment comfortable.<ref name="skybrary" /> This process is contrary to the [[List of common misconceptions|common misconception]] that cabin air in airplanes is the same air being recycled.<ref>{{Cite web |last=Villazon |first=Luis |title=How 'stale' is the recycled air in a plane? |url=https://www.sciencefocus.com/science/how-stale-is-the-recycled-air-in-a-plane |access-date=July 6, 2024 |website=[[BBC Science Focus]]}}</ref>

Bleed air is also used to heat the engine [[intake]]s. This prevents ice from forming, accumulating, breaking loose, and being ingested by the engine, which could damage it.<ref name="skybrary2">{{cite web | url=http://www.skybrary.aero/index.php/Ice_Protection_Systems | title=Ice Protection Systems | publisher=Skybrary | access-date=January 1, 2013}}</ref>

On aircraft powered by jet engines, a similar system is used for [[Ice protection system|wing anti-icing]] by the 'hot-wing' method. In icing conditions, water droplets [[condensation|condensing]] on a wing's leading edge can freeze. If that happens, the ice build-up adds weight and changes the shape of the wing, causing a degradation in performance and possibly a critical loss of control or [[Lift (force)|lift]]. To prevent this, hot bleed air is pumped through the inside of the wing's leading edge, heating it to a temperature above freezing, which prevents the formation of ice. The air then exits through small holes in the wing edge.

On propeller-driven aircraft, it is common to use bleed air to inflate a rubber boot on the leading edge, breaking the ice loose after it has already formed.<ref name="skybrary" /><ref name="skybrary2" />

Bleed air from the high-pressure compressor of the engine is used to supply [[Harrier jump jet#Specifications|reaction control valves]] as used for part of the [[flight control system]] in the [[Harrier jump jet|Harrier]] family of military aircraft.