Definition
The sealed internal cavity inside the airspeed indicator into which ram (pitot) air pressure is fed through a line from the pitot tube. The pressure inside this chamber acts on a diaphragm, which expands or contracts as the ram pressure changes. The diaphragm's movement is mechanically linked to the airspeed needle.
Plain English
The small enclosed space inside the airspeed indicator that receives the air pressure piped in from the pitot tube. As that pressure rises with speed, it pushes on a flexible diaphragm inside the chamber, which moves the needle on the gauge.
Context Anchor
Seen in pitot-static system diagrams, especially when learning how the airspeed indicator uses pitot pressure and static pressure.
Derivation
Pitot comes from Henri Pitot, an 18th-century French engineer who invented the tube that captures the pressure of moving air. Chamber comes from the Latin camera, meaning a room or enclosed space. So a pitot pressure chamber is simply the enclosed space inside the instrument that holds the pressure delivered by the pitot tube.
Why Pilots Care
Blockage or damage to the pitot pressure chamber produces incorrect airspeed readings that can lead to loss of control or unsafe flight decisions.
Grounding Statement
As the airplane moves forward, air enters the pitot tube and sends pressure to the pitot pressure chamber inside the airspeed indicator.
Intuition Check
Do not think of “chamber” as a large room. Here it means a small enclosed space inside the instrument that holds air pressure.
Example Sentence 1
Ram air from the pitot tube travels through the pitot line and enters the pitot pressure chamber inside the airspeed indicator.
Example Sentence 2
A blocked pitot pressure chamber caused the airspeed indicator to read zero during the takeoff roll.