Winglets

In 1897, six years before the first powered flight occurred, a patent was awarded for “wing end-plates”. An engineer had noticed the adverse effect of wingtip vortices that occur on fixed-wings and developed a countermeasure. Vortices are created around wingtips due to air curling up over the wingtip and back down in a circular fashion. The idea was to interrupt the wingtip vortice in such a way to both increase lift and decrease the induced drag (an aerodynamic force produced by lift).
This phenomenon of rotating air has far-reaching consequences. Most notably, the vortices decrease the wing’s efficiency (due to increased induced drag) and leave wake turbulence behind the aircraft which can be hazardous to other aircraft. In theory, the most efficient wing ever designed would have to be infinitely long to avoid creating wingtip vortices. Since that’s clearly impractical, other methods have been designed to mitigate the issue. The famous Supermarine Spitfire is a terrific example of such ingenuity.
The Spitfire was an iconic, single-seat British fighter during World War II (it was actually effective before and after the war). The Royal Air Force (RAF) relied heavily on the Spitfire, along with the Hawker Hurricane, during the Battle of Britain. Numerous engineering advancements made their way into the Spitfire’s wing but its elliptical planform is the most obvious. What’s so special about an elliptical wing is that it is the most efficient aerodynamic shape for an “untwisted wing”. The reason it is the most efficient is that it creates the least induced drag. It’s just another approach to minimizing the wingtip vortice.
With the end of WWII and the dawning of the jet age, minimizing drag (and optimizing a plane’s fuel efficiency/range) became increasingly important. By that time, it was clear that the primitive wing end-plates were not the optimal solution. The Boeing Co., in fact, declined to pursue advancements to wingtip devices despite recommendations from engineers within the company.
Entrepreneurial engineers saw an opportunity and left Boeing to start a company called Aviation Partners, Inc. Soon Boeing realized their mistake. Winglets can improve the fuel efficiency of an aircraft by about 3 - 5%. Over the life of an airplane, that’s serious savings! Soon, Aviation Partners was contracted to retrofit Boeing’s fleet of B737-300 aircraft with winglets. Before too long, Boeing licensed the rights to the technology.
As wing design evolved and planes started covering bigger and bigger distances, swept wings became popular and wing-end plates, now more commonly referred to as winglets, became mainstream.
These days it seems like everyone has a different design for wintip devices (variations include blended, raked, split-tip, and fenced among others) and everyone thinks their design is the most optimal.

In 1897, six years before the first powered flight occurred, a patent was awarded for “wing end-plates”. An engineer had noticed the adverse effect of wingtip vortices that occur on fixed-wings and developed a countermeasure. Vortices are created around wingtips due to air curling up over the wingtip and back down in a circular fashion. The idea was to interrupt the wingtip vortice in such a way to both increase lift and decrease the induced drag (an aerodynamic force produced by lift).


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