A winglet is a device on the wing of an aircraft which is designed to increase the operating efficiency of the aircraft. Winglets consist of angled projections at the end of the wing. The precise size and angle vary, depending on the aircraft, and winglets may be installed during manufacturing, or added later. Some companies offer aircraft with and without winglets, allowing people to choose which option they prefer when they order. Retrofitting to add winglets can be performed by facilities which specialize in aviation repair and maintenance.
The science behind the winglet dates back to the late 1800s, when people experimenting with the physics of flight noted that angled projections on the end of a wing could increase efficiency. Various experiments with winglets on various aircraft took place during the 1900s, and in the 1970s, winglets began to be added to production aircraft. Today, they can be seen on planes of all sizes along with gliders and other aircraft. It is important to note that winglets can change performance slightly, and pilots need to be alerted to this to compensate with some aircraft.
Using winglets adds thrust and decreases induced drag, reducing the amount of power required to get and keep a plane flying. Winglets also reduce the vortices which form behind the wingtips of an aircraft. While these vortices may not be a problem for the plane, if another plane crosses the path of air disturbed in a vortex, it can experience turbulence, which creates unsafe conditions. Thus, using winglets improves safety for other planes, especially around areas like airports which see a lot of air traffic.
There's another advantage to the winglet: It cuts down on noise produced by the aircraft. In areas with noise abatement laws or worries about noise, such devices may be greatly appreciated because they lower sound. While the sound of an individual plane may not be reduced that much, when this is multiplied across a fleet, it can make a significant difference. This has made the winglet popular in communities near airfields and airports.
When designing new aircraft, engineers play with various winglet configurations to find the most appropriate angle and size for the aircraft they are designing. People who are interested in seeing how winglets change the dynamics of flight can try testing out winglets on model aircraft; some allow people to reposition the winglets, creating a great demonstration of how the angle can impact the aircraft in flight.