stalling promoted by the forward sweep. Washout near the tips can also be used to decrease lift-induced drag, since at a lower angle of incidence, the lift produced will be lower, and thus the component of that lift which acts against thrust is reduced, however, it has been theorised by Albion H. Bowers that certain washout characteristics in the tips, that lead to a bell-shaped span loading may in fact produce lift-induced thrust, and upwash. He thus suggests that birds do not utilise vertical stabilisers, since they do not need to counteract adverse yaw caused by lift-induced drag. Washout is also found in gliders and hang gliders. In helicopters, blade twist is used to reduce lift towards the blade tip, thus reducing unequal rotor lift distribution. See also Wing twist Stall (flight) Spin (flight) Unequal rotor lift distribution References External links http://www.allstar.fiu.edu/aero/Wing32.htm http://www.fly-imaa.org/imaa/hfarticles/const/v1-4-10.html http://www.propdesigner.co.uk/html/washout_and_washin.html Aerodynamics Aircraft wing design