Definition
Hot, high-pressure air drawn (bled) from the compressor section of a turbine engine and routed through ducts to power aircraft systems such as anti-ice, pressurization, air conditioning, and engine starting.
Plain English
Some of the hot, pressurized air being squeezed inside the engine is tapped off and piped to other parts of the aircraft to do useful work, like keeping the wings free of ice or pressurizing the cabin.
Context Anchor
Seen in turbine aircraft anti-ice systems, especially when describing how hot air is used to protect wings, tail surfaces, or engine inlets from ice.
Derivation
‘Bleed’ is used in the engineering sense of letting a controlled amount of fluid or gas escape from a system, like bleeding brakes. Here, a portion of compressed air is let out of the engine on purpose to feed other systems.
Why Pilots Care
Provides an efficient source of hot air for ice protection and other systems but reduces engine thrust and fuel efficiency when in use.
Analogy
It is like taking some hot air from a strong air pump and sending it through a pipe to warm another part of the machine. The air still comes from the engine, but it is being used for a system job instead of only for power.
Intuition Check
“Bleed” does not mean the engine is damaged or leaking air by accident. Here it means air is intentionally taken from the engine and sent where the aircraft needs it.
Example Sentence 1
Before entering icing conditions, the crew turned on the wing anti-ice system, which uses engine bleed air to heat the leading edges.
Example Sentence 2
Engine bleed air was used to maintain cabin pressure after the aircraft climbed through the freezing level.