Winglets: Types, Benefits & Differences | Aircraft Aerodynamics

[Hatty]

I have always known quite a bit about aircraft and aerodynamics, but there is something that I have never quite figured out. What is the difference between raked wingtips, blended winglets, wingtip fences, etc? I am guessing that they each have traits that benifit certain aircraft over others, but what are they?

 

[ajSpades]

Winglets, raked (scimitar) winglets, blended winglets, etc. are all about increasing the efficiency of the wing generating lift. On conventional wings there is a circulation of air from the bottom of the wing (higher pressure) around the wingtip to the top of the wing (lower pressure). This circulation increases drag as well as producing powerful vortices that can disrupt nearby aircraft.

Winglets are one (but not necessarily the best) way to mitigate this circulation. Putting a physical barrier (vertical winglets) on the tip of the aircraft helps block the flow of air. Raked (scimitar) winglets are much more efficient and require much less structure to achieve what winglets do.

One reason a lot of heavier aircraft lately have winglets is that they are easy to add on. You are basically putting a flat-plate at the wingtip. Newer transport aircraft, most notably the Boeing 787, will be incorporating raked (scimitar) wingtips.