An Introduction to Bleed Air in Airplanes

Airplanes need air for a variety of purposes. Fortunately, they can get this air from their engines. Known as bleed air, engines will generate it naturally. Airplanes don’t have to use separate devices or systems to generate air. As long as an airplane has air-breathing turbine engines, it can use bleed air. What is bleed air exactly, and why do airplanes need it?

What Is Bleed Air?

Bleed air consists of excess air taken from or “bled off” air-breathing turbine engines. Turbine engines require air. They burn air and jet fuel to generate propulsion.

Air from outside of the airplane will initially go into the turbine engines. While inside of the engines’ compressor, the air will become hotter. An increase in temperature will then cause the air to expand, thereby pressurizing it. Most of the pressurized air will proceed to the combustion chamber where it’s burned with jet fuel. However, some excess pressurized air will be rerouted to a bleed air system duct system valves. This excess pressurized air is bleed air.

Why Airplanes Need Bleed Air

Airplanes need bleed air to power pneumatic components. Pneumatic components are characterized by their use of pressurized air. Most airplanes have both hydraulic and pneumatic components. The former requires the use of pressurized air, whereas the latter requires the use of pressurized fluid. To power pneumatic components, most airplanes use bleed air.

In addition to powering pneumatic components, bleed air helps to regulate the cabin pressure. The air becomes thinner at high altitudes. To provide a safe and comfortable environment for passengers — as well as crew members — airplanes must have a pressurized cabin.

Airplanes will use bleed air to regulate the pressure of their cabin. If the cabin pressure is too low, they will pump more air into it. Bleed air will pass through a filter so that any pollutants and particulate matter are removed from it. The newly cleaned air will then enter the cabin where it increases the pressure.

Some airplanes use bleed air to prevent the formation of ice on their wings. They will reroute the bleed air over their wings. Because bleed air is hot, it will melt any lingering ice while simultaneously protecting the wings from ice.

In Conclusion

Bleed air is excess pressurized air that comes from an airplane’s turbine engines. It’s used to power pneumatic components, regulate cabin pressure and prevent the formation of ice on the wings.

Looking to Build Your Own Airplane?

Click below to browse Monroe's Aerospace Parts!

Browse Aerospace Parts