12.76 Control Systems

12.76.2 Explain the common methods of the mechanical operation of the:

(a) primary flight controls;

The primary flight controls (ailerons, elevator, and rudder) are commonly operated through mechanical linkages that transmit pilot control inputs from the cockpit to the control surfaces.

Common methods include:

Cable and Pulley Systems

• Steel control cables run through pulleys from the cockpit controls to the control surfaces
• Movement of the control wheel, control column, or rudder pedals pulls one cable and releases the opposite cable
• Commonly used because they are light, reliable, and flexible in routing

Pushrods / Torque Tubes

• Rigid rods or rotating tubes transmit movement directly to the control surface
• Provide positive, precise control movement with little lost motion
• Often used in shorter control runs

Bellcranks and Linkages

• Used to change the direction of movement or alter mechanical advantage
• Connect cables or rods to the control surface horns