[trebuchet03]

Originally Posted by Tourigjm

Winglets are used to reduce the downwash vorticies that are created by this shock at the end of the wing, which in turn reduces induced drag.

There's also noise reduction benefits too

Blended winglets offer operational and economic benefits to BBJ and 737-800 customers. Mission block fuel is improved approximately 4 percent. Range capability is increased by as much as 200 nmi on the BBJ and 130 nmi on the 737-800 commercial airplane. The reduction in takeoff flap drag during the second segment of climb allows increased payload capability at takeoff-limited airports.

Environmental benefits include a 6.5 percent reduction in noise levels around airports on takeoff and a 4 percent reduction in nitrogen dioxide emissions on a 2,000-nmi flight.

The blended winglets now are available as standard equipment on BBJs, as optional equipment on 737-800 commercial airplanes, and by retrofit for BBJs, 737-800, and 737-700 commercial airplanes already in service. Because the winglet structure and systems follow established maintenance intervals and life cycles, winglets have a minimal effect on airplane maintenance.

Aero 17 - Blended Winglets