Definition
The difference between the air pressure inside a pressurized aircraft cabin and the air pressure outside the aircraft. It is normally expressed in pounds per square inch (psi) and is monitored and limited by the aircraft's pressurization system to stay within structural limits.
Plain English
How much higher the air pressure is inside the cabin than outside the aircraft. As the airplane climbs, the outside air thins, but the cabin is kept thicker so passengers and crew can breathe normally. The gap between the two is the cabin differential pressure.
Context Anchor
Seen in pressurized aircraft operations, especially when checking cabin pressure limits during climb, cruise, and descent.
Derivation
Differential comes from the Latin differentia, meaning 'a difference.' It simply names the gap between two values — here, the gap between inside and outside cabin pressure.
Why Pilots Care
Keeps the cabin environment safe and comfortable at altitude while preventing structural stress on the fuselage from excessive pressure difference.
Grounding Statement
As the aircraft climbs and outside air pressure drops, the cabin pressure system keeps more pressure inside, creating cabin differential pressure.
Intuition Check
Cabin differential pressure is not the same as cabin altitude. Cabin altitude tells what pressure the cabin feels like; cabin differential pressure tells the pressure difference between inside and outside.
Example Sentence 1
As the aircraft climbed through 30,000 feet, the cabin differential pressure approached its maximum limit of 8.6 psi.
Example Sentence 2
Exceeding the aircraft's maximum cabin differential pressure can stress the airframe and trigger an emergency descent.