What is the main purpose of the primary stops in a control system?

The main purpose of the primary stops in a control system is to set the range of movement of the control surface. Primary stops are critical components that define the limits to which a control surface, such as an aileron, rudder, or elevator, can travel. By establishing these limits, primary stops ensure that the control surfaces operate within safe and effective parameters, preventing excessive deflection that could lead to structural damage or loss of control during flight. This is particularly important in maintaining the aircraft's stability and handling characteristics.

Setting the correct range of movement contributes to the overall safety and performance of the aircraft, as it prevents the control surfaces from being moved beyond their designed capabilities.