What is the purpose of the weight on wheels switch in aircraft landing gear systems?

The weight on wheels switch plays a crucial role in aircraft landing gear systems by preventing the retraction of the landing gear while the aircraft is on the ground. This safety feature ensures that the landing gear remains extended and locked during ground operations, which is essential for the safe operation of the aircraft during takeoff and landing phases.

When the aircraft is on the ground, the weight on wheels switch senses the load on the landing gear and sends a signal to the landing gear control system. If the aircraft is detected to be sitting on the ground, the switch activates a safeguard that inhibits any command to retract the landing gear. This mechanism helps to avoid accidental retraction, which could lead to catastrophic outcomes.

The other options do not accurately describe the function of the weight on wheels switch. For instance, while the switch is relevant to ground safety, it does not measure the aircraft's weight or control the landing gear doors directly, nor does it activate the landing gear indicator lights. These functionalities are controlled by different systems within the aircraft's landing gear mechanisms.