What is a limit switch, and where is it commonly used on aircraft landing gear?

• A. A switch that detects temperature in the landing gear bay.
• B. A switch that detects position; used to indicate gear up/down position to the flight deck.
• C. A switch that measures hydraulic fluid level.
• D. A switch that signals wheel speed.

Answer: (B)

A limit switch is a device that detects the end of travel of a moving part and sends an electrical signal when the part reaches a defined position. In aircraft landing gear, limit switches are placed at the gear’s travel ends to indicate when the gear is fully extended (down) or fully retracted (up). These signals feed the cockpit gear position indicator and the gear control logic, helping coordinate door sequencing, interlocks, and confirmation that the gear is properly locked before flight. They aren’t used to measure temperature, hydraulic fluid level, or wheel speed.