A squat switch may be installed in a landing gear retraction system to prevent the landing gear from being raised while the aircraft is on the ground.

• A. False
• B. Only on some aircraft
• C. Not used
• D. True

Answer: (D)

Ground sensing interlocks protect gear by preventing retraction when weight is on the wheels. A squat switch is one way to implement that safety function: it is actuated by the aircraft’s weight on the main gear and signals the retraction system to stay extended while on the ground. When the airplane is airborne and the wheels are unloaded, the switch changes state and allows the retraction circuit to operate. Because some aircraft use this method while others rely on different sensors or logic, a squat switch may be installed on certain designs to provide this protection. The purpose is to prevent inadvertent gear retraction on the ground, which could cause a gear-up condition or damage.