Which term refers to a pressurization range where cabin pressure remains constant as altitude changes?

• A. Isobaric range
• B. Unpressurized
• C. Differential pressure range
• D. Heat exchanger range

Answer: (A)

Isobaric range means the cabin pressure is kept constant as the aircraft changes altitude. The pressurization system holds the cabin at a fixed pressure, so as outside air pressure drops with higher altitude, the inside pressure stays the same, changing only the differential pressure across the cabin walls. This is different from unpressurized, where there is no controlled cabin pressure, or from a differential pressure range, which refers to the allowable pressure difference the system can maintain rather than keeping cabin pressure fixed across altitudes. Heat exchanger range is unrelated to maintaining a constant cabin pressure.