Plain English Meaning

A small sealed space inside the airspeed indicator where the air coming in from the pitot tube is captured. As the airplane flies faster, more air pressure builds up in this space, and that pressure is what makes the airspeed needle move.

Full Definition

In the pitot-static system, a sealed compartment inside the airspeed indicator that receives ram air pressure from the pitot tube. The chamber contains a flexible diaphragm that expands as ram air pressure rises and contracts as it falls. This movement drives the linkage that turns the airspeed needle.

Context Anchor

Seen in diagrams and explanations of the pitot-static system, especially around the pitot tube, airspeed indicator, and the lines that carry air pressure between them.

Derivation

Chamber comes from Latin camera, meaning a room or enclosed space. A pressure chamber is simply an enclosed space designed to air at a pressure so that pressure can be measured or used to drive something — in this case, the airspeed needle.