What type of air is used to aid in start injector ventilation, prevent compressor stalls, and provide cabin heat?

• A. Bleed
• B. Ram air
• C. Vent air
• D. Ambient air

Answer: (A)

Bleed air is hot, high‑pressure air drawn from the engine’s compressor stages. It provides the supply for starting the engine (through the air-start system and start injectors), helps prevent compressor stalls by delivering stable air flow during critical operating points, and feeds the environmental control system to provide cabin heat. The air is conditioned before it reaches the cabin, ensuring it’s suitable for occupants. This combination of uses—starting, stall prevention, and cabin heating—comes from bleed air, not from ram or ambient air.