In cabin pressurization, which elements are involved in regulating pressure and temperature?

• A. Fuel flow and engine tuning.
• B. Bleed air flow, exhaust through outflow valves, and packs in the ECS.
• C. Airspeed and altitude indicators.
• D. Hydraulic fluid and piston pumps.

Answer: (B)

The key idea is how the cabin environmental control system uses three elements to set both pressure and temperature. Bleed air from the engines provides the high‑pressure, high‑temperature air that becomes the source for the cabin. The packs in the environmental control system cool and condition that air, bringing it to a comfortable temperature for passengers. The outflow valves regulate cabin pressure by controlling how much air is vented to the outside; the position of the valve, guided by the pressurization controller, maintains the desired cabin altitude. Together, these parts determine the amount of supply air and the rate at which air leaves the cabin, which sets the pressure, while the packs adjust the temperature of that air. Other options don’t relate to how the cabin’s pressure and temperature are managed—they involve propulsion, flight instruments, or hydraulic systems, not the environmental control system.