Definition
The altitude indicated when an altimeter's barometric setting is adjusted to 29.92 inches of mercury (the standard sea-level pressure). It represents height above the standard datum plane and is used as a common reference for aircraft performance calculations and for flight at higher altitudes.
Plain English
The altitude your altimeter shows when you set it to the standard pressure value of 29.92. It gives every aircraft a shared reference point, regardless of the actual local pressure.
Context Anchor
Pilots see pressure altitude in performance planning, especially when checking takeoff distance, landing distance, and climb capability.
Derivation
The word 'pressure' comes from the Latin 'pressura,' meaning 'a pressing.' Air has weight, and that weight presses down. Pressure altitude is altitude expressed in terms of that pressing force, measured against an agreed standard rather than today's local weather.
Why Pilots Care
Aircraft performance data in the pilot's operating handbook is based on pressure altitude so that takeoff, climb, and landing distances remain accurate regardless of local barometric pressure.
Grounding Statement
As an airplane climbs, air pressure drops; pressure altitude names the altitude that matches the surrounding air pressure on a standard scale.
Intuition Check
Pressure altitude is not the airplane’s exact height above the ground. It is altitude based on air pressure using the standard altimeter setting.
Example Sentence 1
Before takeoff, the pilot briefly set 29.92 in the altimeter to read the pressure altitude for the performance chart.
Example Sentence 2
High temperature and high pressure altitude together reduce engine and propeller performance even when the field elevation is low.