In which pressurization range does cabin altitude track the aircraft altitude?

• A. Unpressurized
• B. Isobaric range
• C. Differential pressure range
• D. Positive pressure range

Answer: (A)

When there is no cabin pressurization system actively controlling the air inside, the cabin pressure simply equals the outside ambient pressure. As the aircraft climbs, outside pressure drops, so the cabin altitude rises and effectively tracks the aircraft's altitude. This is the unpressurized condition, where no deliberate pressure control keeps the cabin at a fixed altitude. In contrast, when a aircraft is pressurized, the system maintains a set cabin pressure (and thus a relatively fixed cabin altitude) despite increasing outside altitude, so it does not track the aircraft altitude. Isobaric, differential pressure, and positive pressure ranges describe different ways the system manages pressure, but none of them result in cabin altitude mirroring the airplane’s altitude. So the correct choice is unpressurized.