Bleed air can be drawn from which locations?

• A. Engine compressor section
• B. APU/GTC
• C. External air source
• D. All of the above

Answer: (D)

Bleed air can come from multiple sources to keep pneumatic systems, cabin conditioning, and anti-ice functioning across different phases of flight and ground operations. The primary source during normal flight is the engine compressor bleed air, taken from specific stages of the engine as pressures and temperatures are suitable for the systems. If the engines aren’t providing bleed air (for example, when they’re not running or during certain start procedures), the APU (or a GTC) can supply bleed air to the same systems. On the ground, an external air source can be connected to provide pneumatic supply when the aircraft is not generating bleed air from its own units. Because the system is designed to switch between these sources as needed, all of these locations can be used to supply bleed air.