The reason differential aileron movement works is that deflection of an aileron upward can't do much harm; it is the aileron deflected downward that can be the "troublemaker," i.e., the one possibly precipitating a wing-tip stall.
To help reduce the likelihood of wing tip stall and adverse yaw, engineers developed differential ailerons. As the name implies, they deflect by different amounts: When the stick or yoke is moved to the right, for example, the aileron on the right (descending) wing is deflected up much more than the left (ascending) wing's aileron is deflected down.
Another method engineers use to minimize adverse yaw is the differential aileron
design, pictured in Figure 2 on the opposite page.
This is known as differential aileron design (see the sidebar above).
According to the FAA and its Pilot's Handbook of Aeronautical Knowledge (PHAK), FAA-H-8083-25A, when a differential aileron design is employed, "one aileron is raised a greater distance than the other aileron is lowered for a given movement of the control wheel or control stick.
Also, many planes use differential aileron
throw or other design techniques to minimize adverse yaw.
Credit may belong to a design trait called "differential ailerons
." Differential ailerons
, well, differ in the degree of deflection between inside and outside wings.
(By the time most of today's airplanes were designed, engineers knew to make the aileron's downward movement less than its upward movement, dubbed "differential ailerons
," to help correct for adverse yaw).