Definition
The altitude that corresponds to the air pressure inside the aircraft cabin, expressed as the equivalent height above sea level in a standard atmosphere. In a pressurized aircraft, the cabin pressure altitude is typically much lower than the actual altitude the aircraft is flying at; in an unpressurized aircraft, it is essentially the same as the aircraft's altitude.
Plain English
It's how high the inside of the cabin 'feels' to your body in terms of air pressure, even if the aircraft itself is much higher. A jet cruising at 35,000 feet might keep the cabin feeling like it's at 7,000 feet.
Context Anchor
Seen in discussions of pressurization, oxygen use, and night vision, especially when explaining how lower air pressure can affect the pilot’s body.
Derivation
“Cabin” means the enclosed space where people sit in an aircraft. “Pressure altitude” means an altitude based on air pressure rather than actual height. Together, the term points to the pressure-based altitude inside the cabin.
Why Pilots Care
Determines the effective altitude for hypoxia risk and visual performance inside a pressurized aircraft.
Grounding Statement
If the cabin pressure altitude is 8,000 feet, the air inside the cabin affects your body like air at 8,000 feet, even if the airplane is much higher.
Intuition Check
Do not read “cabin pressure altitude” as the airplane’s actual altitude. It means the pressure-equivalent altitude inside the cabin.
Example Sentence 1
At a cabin pressure altitude of 8,000 feet, the crew noticed reduced night vision even though the aircraft was cruising at FL350.
Example Sentence 2
Even with pressurization, a higher cabin pressure altitude can reduce night vision effectiveness.