Definition
A spring-loaded air valve used in aircraft tires, struts, and pneumatic accumulators that opens when a charging fitting depresses its central pin and seals automatically when released, allowing pressure to be added or checked without losing the existing charge.
Plain English
A small valve with a spring-loaded pin in the middle. Push the pin in to add or release air or gas; let go and it seals itself.
Context Anchor
Seen during aircraft tire servicing, tire pressure checks, and landing-gear strut servicing.
Derivation
Named after August Schrader, the inventor who patented this style of valve in the late 1800s. The same design is used on car and bicycle tires, which is why the valve looks familiar to most people.
Why Pilots Care
Correct tire inflation verified through the Schrader valve directly affects takeoff distance, landing handling, and tire longevity.
Analogy
It works like the valve stem on a car tire: you press a gauge or hose onto it, pressure can move through it, and it seals again when you remove the tool.
Intuition Check
Do not think of the cap as the valve. The sealing part is the small spring-loaded core inside the stem; the cap mainly protects it from dirt and damage.
Example Sentence 1
The technician attached the nitrogen servicing hose to the Schrader valve on the main strut and brought it up to the specified pressure.
Example Sentence 2
After the tire change the mechanic replaced the dust cap on the Schrader valve to keep dirt out of the core.