Definition
The pressure produced by the forward motion of an aircraft through the air, equal to the difference between total (ram) pressure measured at the pitot tube and static pressure measured at the static port. Impact pressure represents only the dynamic component of airflow striking the aircraft and is the quantity used by the airspeed indicator to display airspeed.
Plain English
The extra pressure the air creates simply because the aircraft is moving forward through it. It is what is left after you subtract the normal surrounding air pressure from the pressure pushing into the front of the pitot tube.
Context Anchor
Seen in pitot-static system and airspeed indicator discussions.
Derivation
From Latin impactus, meaning 'struck against' or 'driven into.' The name reflects what the pressure represents: air being struck by the moving aircraft and pressing against the front of the pitot tube.
Why Pilots Care
Correct impact pressure is required for accurate airspeed readings used in performance and safety decisions.
Analogy
It is like holding your hand flat out of a car window. The faster the car moves, the harder the air pushes on your hand.
Grounding Statement
Stick your hand out of a moving car window. The push you feel on your palm is impact pressure -- the pressure caused purely by motion through the air.
Intuition Check
Impact pressure does not mean pressure from a collision or damage. Here it means pressure created by moving air being stopped at a measuring opening.
Example Sentence 1
When the pitot tube iced over in cruise, impact pressure dropped to zero and the airspeed indicator slowly fell toward the bottom of the scale.
Example Sentence 2
A blocked pitot tube prevents accurate impact pressure from reaching the instruments.