Trim drag

Trim drag is the aerodynamic drag created by the flight control surfaces on an aircraft when they are used to offset the changes in center of gravity as the aircraft flies. These changes are often caused by fuel being burned off over the period of the flight. They are magnified in designs where the wing planform is not arranged to lie directly outward from the fuselage, as in a swept wing or delta wing aircraft. Systems that actively pump fuel between separate fuel tanks in the aircraft can be used to offset this effect and reduce the trim drag component.