Vortex-Reducing Winglets Reduce Drag

If a traditionally configured wing is producing lift at a positive angle of attack, the higher pressure below the wing at the wingtip tends to spill up into the low-pressure area above the wing. The higher-pressure air curls upward and because the wing is moving forward through the atmosphere, that moving air simultaneously produces a twirling vortex of spinning air that trails behind the wingtips. The energy needed to generate these vortices is a drag...