Active load control

One way to reduce some aeroelastic problems, is to use control surfaces to pro­vide aerodynamic forces to oppose twisting and bending motions before they can build up to serious levels. In particular, it is possible to use control surfaces to oppose the effects of sudden gusts. Thus, if an up-gust causes one wing to bend upwards, the movement can be opposed by applying up-aileron on that wing in order to reduce the aerodynamic lift. This active load alleviation tech­nique requires the use of a special form of auto-pilot, with sensors to detect local accelerations.

There are many benefits from using such a technique. Structural loads are reduced, the fatigue life is improved, possible dangerous aeroelastic conditions can be avoided, and even the ride comfort can be improved.

The use of active load alleviation is another reason why forward-swept wings have become a practical possibility. The main problem lies in the dif­ficulty in designing a system that only does what it is intended to do, and does not start applying spurious or inappropriate control inputs, and does not try to resist intended motion.