How is cabin pressure controlled on the 787?

How is cabin pressure controlled on the 787?

• A. Manually by the pilot via a dial
• B. Automatically by the pressurization controller using feedback from sensors, with outflow valves regulating cabin pressure
• C. By venting cabin air to atmosphere at 1 atm
• D. By relying on engine bleed air to regulate cabin pressure

Answer: (B)

Cabin pressure is kept at a safe, comfortable level by an automatic closed‑loop system. The pressurization controller constantly reads actual cabin pressure and differential pressure from sensors and uses that data, along with the altitude schedule, to determine the target cabin pressure. It then moves the outflow valves to control how much air is vented from the cabin to the atmosphere. By venting more air, the pressure drops; by venting less, the pressure rises toward the target. The 787’s environment control system is bleedless, so the air supplied to the cabin comes from electric packs, and the controller handles pressure by regulating venting through the outflow valves, not by manual pilot input or engine bleed air. Safety relief valves provide protection against overpressure.

Cabin pressure is kept at a safe, comfortable level by an automatic closed‑loop system. The pressurization controller constantly reads actual cabin pressure and differential pressure from sensors and uses that data, along with the altitude schedule, to determine the target cabin pressure. It then moves the outflow valves to control how much air is vented from the cabin to the atmosphere. By venting more air, the pressure drops; by venting less, the pressure rises toward the target. The 787’s environment control system is bleedless, so the air supplied to the cabin comes from electric packs, and the controller handles pressure by regulating venting through the outflow valves, not by manual pilot input or engine bleed air. Safety relief valves provide protection against overpressure.