Cockpit SX Tutorials: Aileron Differential

By Mike Shellim

Aileron Differential on the Cockpit SX

To obtain smoooth turns especially on gliders, aileron travel is normally set so there is more movement in the up direction than down. This is called aileron differential, or 'diff' for short.

The adjustment for diff on the Cockpit SX is different to other systems, as there is no dedicated Diff menu.

To adjust the diff on the outer control surfaces (ailerons), go to the AI-AI mixer menu (AIleron stick -> AIleron servos). Push the aileron stick one way and adjust the amount of up-aileron travel. Push the stick the other way and adjust the amount of down-aileron travel.

To adjust the diff on the inner control surfaces (flaps), do exactly the same thing, except using the AI-FL mixer (AIleron stick -> FLap servos).

Why the Multiplex way?

Why did Multiplex not simply provide a single Diff menu? Because their way allows independent differential adjustment for the inner (flap) and outer (aileron) control surfaces.

Servo Travel menu

Don't use Servo Travel to adjust aileron differential - this is bad practice. Doing this will make the aileron servos response assymetric to all control inputs, not just aileron, when using mixers. Instead, adjust diff using the AI-AI mixer as described above.

Aileron Differential Suppression (ADS)

On sailplanes with 4-servo wings, the flaps normally go down and the ailerons are raised as spoiler is deployed. As the ailerons are raised, full movement is required from the downgoing aileron to preserve directional control. This raises a potential problem if differential has been set, since differential reduces the amount of downgoing movement.

To overcome this, the Cockpit SX features Automatic Differential Suppression (ADS). This automatically suppresses differential on the outer control surfaces (chs 1&5) as spoiler is deployed. With zero spoiler, the differential takes the value as set in the AI-AI menu. As full spoiler is applied, differential is gradually reduced to zero, i.e. the downgoing aileron movement is restored.

The flaps (chs 6&7) do not feature ADS, since these surfaces are lowered not raised as brakes are deployed.


The Cockpit SX way of setting up differential is flexible and logical. The provision of aileron differential suppression (ADS) means that you can set up crow brakes, without worrying about turn response due to differential.