What Winglets Do
Winglets increase efficiency by reducing lift-induced drag. They do this by relocating and diminishing the vortex at the wing’s tip, resulting in lower fuel burn, higher cruise speed and longer range.
Conventional winglets, which angle up from the wing at more-or-less straight obtuse angles, reduce drag. But with their curved transition between wing and winglet and precisely designed airfoil, the Aviation Partner Blended Winglets do it better–up to 60-percent better depending on the installation, according to the company. The design cuts drag by avoiding concentrations of trailing vortices and reducing aerodynamic interference between the wing and winglet, particularly at high speeds.
Performance gains realized by Blended Wingtip-equipped jets average about 5 to 7 percent. A Hawker 800, for example, will fly 30 minutes longer, 180 nm farther and 18 knots faster and have an initial cruise altitude of 2,000 feet higher. Aviation Partners CEO and founder Joe Clark estimates that Southwest’s 737-700s each save about 100,000 gallons of fuel per year. Other benefits include reduced wake turbulence and lower noise, when the engines operate at lower settings while providing the same airspeed as nonwingletted aircraft.
Waiting in the wings for a launch customer is an even more exotic winglet design that Aviation Partners calls a “Spiroid Winglet.” In flight tests on a Gulfstream II, this closed-loop, double winglet reduced drag and cruise fuel consumption by up to 10 percent. It needs more development, however, and Clark said Aviation Partners has no commercial plans for the Spiroid Winglet at this time.