Long-span wings twist when large rolling forces are applied near their tips. Inboard ailerons, located closer to the fuselage, apply their forces ahead of the flexural axis, reduce wing twists and control reversal, and thus remain effective enough to maneuver the aircraft. At high speed the outboard surfaces are locked out, leaving inboard ailerons - often called high-speed ailerons - to provide smooth roll commands, while during low-speed flight flaps are extended and both sets can combine for greater authority.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is the function of the inboard aileron tab?
Inboard aileron tabs operate as control tabs. When the control wheel is turned, the aileron cable moves the inboard aileron tabs. The tabs move opposite to the direction of aileron movement to assist in positioning the aileron aerodynamically. This deflection causes the aileron to move in the opposite direction, reducing the force needed by the pilot to deflect the aileron. If all hydraulic power to the aileron is lost, the system automatically shifts to manually operate aerodynamic tab control, assuring continued roll authority.
What is the difference between outboard and inboard ailerons?
Outboard ailerons are located farther from the fuselage near the wingtips, whereas inboard ailerons sit closer to the fuselage on the trailing edge of the same wing. Both types of ailerons are found on the trailing edge of wings, and they move in opposite directions when manual or autopilot control input is made, rolling the aircraft around its longitudinal axis.
The key functional difference lies in when each set is allowed to operate. Outboard ailerons work only when wing flaps are extended, and they are automatically locked out when flaps are retracted. At high speed they remain locked, and some of the outer roll spoilers are locked out at high speed as well. This scheduling prevents excessive wing twist because outboard ailerons exert forces on the wing behind its flexural axis, the point about which it twists. Inboard ailerons stay active throughout the speed envelope, providing roll control when the outboard surfaces are stowed.
When are inboard ailerons normally used?
Inboard ailerons are used during cruising operations at comparatively high speeds for control, while the outer roll spoilers are locked out at high speed.
