The DES is a system that allows you to link the trimmers of the rear risers (C and D) with the speed-bar. From the start, the DES holds the wing in the trim position, and as it is released, it accelerates by lowering the A and B-risers and raising the rear risers.
This technology allows us to have all the differential available on the speed-bar, so that we do not have to take the hands off the controls to be able to go from the neutral trimmer position to maximum speed, or vice versa.
In case of high speed collapses, it is very useful to be able to return to the neutral position by releasing the speed-bar without having to close the trimmers manually. In this way flights are more comfortable and safe.