Definition
An electrical switch mounted on a landing gear strut that senses whether the airplane's weight is on the wheels. When the strut is compressed by the airplane's weight on the ground, the switch is in one state; when the strut extends as the airplane lifts off, the switch changes state. It is used to enable or disable systems that should only operate on the ground or only in flight, including landing gear retraction circuits, anti-skid systems, and certain warning systems.
Plain English
A switch on the landing gear that knows whether the airplane is sitting on the ground or flying. It tells other systems on the airplane which one it is, so things like gear retraction can't happen on the ground by accident.
Context Anchor
Seen in landing gear safety device discussions, especially on retractable-gear airplanes.
Derivation
Called a 'squat' switch because the landing gear strut compresses, or 'squats,' under the weight of the airplane on the ground. When the airplane lifts off, the strut extends and the switch flips. The name describes exactly what triggers it.
Why Pilots Care
It prevents the landing gear from being accidentally retracted while the airplane is still on the ground, avoiding structural damage or loss of control.
Grounding Statement
When the airplane settles onto its wheels, the compressed gear moves the squat switch and tells the airplane it is on the ground.
Intuition Check
“Squat” does not mean the airplane is damaged or sitting incorrectly. Here it means the landing gear is compressed because the airplane’s weight is on the wheels.
Example Sentence 1
The squat switch prevents the landing gear from retracting while the airplane's weight is still on the wheels.
Example Sentence 2
After takeoff the squat switch opened, allowing the pilot to raise the landing gear without triggering a warning.