Definition
The pressure of the air that strikes the front of the aircraft as it moves forward through the atmosphere. It is the total pressure sensed at the open end of the pitot tube, made up of the static (still) air pressure plus the additional pressure created by the aircraft's forward motion. The airspeed indicator works by comparing this impact pressure to static pressure to determine how fast the aircraft is moving through the air.
Plain English
The pressure the air pushes back with as the aircraft flies into it. The faster the aircraft moves, the harder the air pushes against the front of the pitot tube, and that extra push is what the airspeed indicator measures.
Context Anchor
Seen in pitot/static system and airspeed indicator discussions, especially when explaining how the pitot tube supplies air pressure to the instrument.
Derivation
Impact comes from the Latin impactus, meaning 'struck against.' It captures the idea of air striking the forward-facing opening of the pitot tube as the aircraft moves through it.
Why Pilots Care
Accurate impact air pressure is essential for correct airspeed readings; errors can lead to incorrect speed management and potential loss of control.
Analogy
Think of holding your hand out a car window. The faster the car moves, the harder the air pushes on your palm. Impact air pressure is that push, measured at the front of the pitot tube.
Grounding Statement
Higher speeds produce greater impact air pressure on the pitot tube.
Intuition Check
Impact does not mean a crash or damage here. It means the pressure made by oncoming air being stopped at the pitot tube opening.
Example Sentence 1
On the takeoff roll, impact air pressure builds in the pitot tube and the airspeed indicator begins to show a reading.
Example Sentence 2
During preflight, pilots check that the pitot tube is unobstructed so impact air pressure can be properly measured in flight.