What is the point of winglets on modern aircraft like the boeing 737-800?
Sarastro is correct. You may have seen videos of aircraft flying through clouds or fog and noticed the vortex created at the tip of each wing and trailing off behind the aircraft. These wing tip vortices result from the differential pressure between the lower and upper surface of the wing. The high pressure air is “leaking” around the wing tip to try and balance the lower pressure air on top of the wing. The vortices are pulled along by the aircraft, resulting in what is known as induced drag – i.e. drag that is purely the result of the lift created by the wing itself. The small surfaces added to the wing tips really reduce that induced drag to a minimum, while admittedly adding a bit of form drag in the process. But once you do the math, the winglets provide a significant fuel cost reduction – just by reducing the overall drag.
