Definition
The sealed internal cavity inside the airspeed indicator that receives ram air pressure from the pitot tube. As the airplane moves forward, air is forced into this chamber through the pitot line, and the resulting pressure expands a diaphragm that drives the airspeed indicator needle.
Plain English
A small sealed space inside the airspeed indicator where the air pushed in by the pitot tube collects. The harder the air pushes in, the more the indicator reads.
Context Anchor
Seen in pitot-static system discussions, especially when learning how the airspeed indicator receives pressure from the pitot opening.
Derivation
Impact' comes from the Latin impactus, meaning 'struck against.' The chamber is named for the air that strikes into it as the airplane flies forward — the pressure of impact, not just still air.
Why Pilots Care
If the pitot tube or its line becomes blocked, pressure in the impact pressure chamber stops changing normally, and the airspeed indicator will give false readings. Understanding this chamber makes pitot blockage symptoms much easier to recognize in flight.
Grounding Statement
As the airplane moves forward, air is pushed into this chamber, and that trapped pressure is what the airspeed indicator uses.
Intuition Check
Do not read impact as accident or collision here. In this context, impact means the pressure created when moving air is forced into the pitot opening.
Example Sentence 1
Ram air from the pitot tube enters the impact pressure chamber and flexes the diaphragm to move the airspeed needle.
Example Sentence 2
A blocked impact pressure chamber prevents the airspeed indicator from receiving total pressure and causes erroneous low airspeed readings.