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 (airplane on the ground), the switch is in one state; when the strut extends after liftoff, it changes state. This signal is used by other airplane systems to enable or disable functions that should only operate on the ground or only in flight, such as preventing inadvertent landing gear retraction while on the ground.
Plain English
A switch on the landing gear that tells the airplane whether it is sitting on the ground or flying. Other systems use this information to allow or block certain actions depending on the situation.
Context Anchor
You may encounter this term when studying retractable landing gear systems, gear warning systems, or aircraft maintenance items related to weight-on-wheels sensing.
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 releases.
Why Pilots Care
It stops the gear from retracting while weight is on the wheels, preventing damage or loss of control on the ground.
Grounding Statement
When the airplane’s weight is on the wheels, the gear compresses and the switch changes position.
Intuition Check
“Squat” does not mean a person crouching here. It means the airplane’s landing gear is compressed because the airplane is sitting on its wheels.
Example Sentence 1
With the airplane on the ground, the safety (squat) switch prevents the landing gear from retracting even if the gear handle is moved up.
Example Sentence 2
After liftoff the squat switch opened, allowing the pilot to raise the landing gear.