What safety feature prevents the landing gear from being retracted while on the ground?

The weight on wheels switch is a crucial safety feature designed to prevent the landing gear from being retracted when the aircraft is on the ground. This switch detects whether the weight of the aircraft is resting on the landing gear. When the aircraft is on the ground, the switch is activated, sending a signal to the landing gear control system that prohibits retraction. This is essential for safety because retracting the landing gear while on the ground can lead to severe damage to the airplane and potentially endanger the safety of the occupants.

The other features mentioned, while important in their own right, do not serve the specific function of preventing landing gear retraction during ground operations. Landing gear locks are more about ensuring that the gear remains in a specific position (down or up) once it is in place. A brake sensor typically monitors the status of the brakes rather than the landing gear position. A gear position indicator simply shows whether the gear is up or down, without actively preventing retraction based on the aircraft's weight status.