What is the role of bleed air in ATR's environmental and pressurization system?

• A. Bleed air from the engines powers air conditioning packs and cabin pressurization.
• B. Bleed air cools the cockpit.
• C. Bleed air provides electrical power.
• D. Bleed air fuels the engines.

Answer: (A)

Bleed air is the pneumatic power source for the environmental and pressurization system. High‑pressure air taken from the engine compressor stages is routed to the air conditioning packs, where it is cooled and conditioned before being supplied to the cockpit and cabin. This conditioned air maintains comfortable temperatures and, through the cabin pressure controller and outflow valve, keeps the cabin at the correct pressure and altitude. The cooling required is achieved inside the packs; bleed air itself is hot and must be conditioned. Electrical power comes from generators (on the engines or APU), not from bleed air, and bleed air does not fuel the engines.