With the arrival of jets, airliners required a movable stabiliser to accommodate CG changes as fuel was consumed from tanks in swept wings (later on fuel was pu

With the arrival of jets, airliners required a movable stabiliser to accommodate CG changes as fuel was consumed from tanks in swept wings (later on fuel was put in the stabiliser in some models). Of course the supersonic program led to the development of the movable stabiliser. Typically an airliner stabiliser is moved with a screwjack. Air loads can overpower the screwjack;so, you have to relieve the air load enough to allow the screwjack to do its job. Next to none of this applies to smaller aircraft which have a variety of trim systems, mostly single axis.