Definition
The ambient atmospheric pressure of the air surrounding an aircraft, measured without any influence from the aircraft's motion through the air. It is sensed through static ports positioned so that ram (impact) air pressure does not affect the reading, and it is the pressure used by the altimeter, vertical speed indicator, and one side of the airspeed indicator.
Plain English
The pressure of the still air around the aircraft, with the effect of forward motion taken out. It's what the surrounding air would push on the aircraft if the aircraft were sitting still.
Context Anchor
Seen in pitot-static system and flight-instrument discussions; the aircraft senses static air pressure through small openings called static ports.
Derivation
Static' comes from the Greek statikos, meaning 'standing still' or 'at rest.' The name fits: this is the pressure of the air at rest around the aircraft, separate from any pressure caused by movement through it.
Why Pilots Care
Accurate static air pressure readings are required for correct altitude, vertical speed, and airspeed indications; blocked or iced static ports produce dangerous instrument errors.
Grounding Statement
As an aircraft climbs, the surrounding air pressure drops, and the instruments use that change to help show what the aircraft is doing.
Intuition Check
Static does not mean radio noise or electricity here. It means the normal surrounding air pressure, separate from the extra pressure created by forward motion.
Example Sentence 1
When the static port iced over, the altimeter froze at the last reading because it had no current static air pressure to reference.
Example Sentence 2
A blocked static port caused the airspeed indicator to read incorrectly during the climb.