Examples: Winglets and Tip Devices
The most common contemporary nonplanar wing configuration is the wing with winglets, as seen below on the McDonnell-Douglas MD-11. These surfaces do reduce induced drag for a given span, as well as providing a means of quickly distinguishing the airplane from a DC-10. The MD-11 design includes small downward winglets, while the 747-400 employs a full-chord single winglet, and many other variations are possible.
A variant of the winglet concept, the C-wing is discussed later in this paper. It involves adding a horizontal winglet extension (a wingletlet?) and has interesting aerodynamic, structural, and control implications.