Aircraft wingtip projections called
winglets have been used on aircraft such as the Airbus A-319 and the Boeing 737-800 to reduce wingtip vortices and lower induced
drag. These single winglets are able to improve fuel efficiency by 3-5%.
STAR, Inc. conceived a system of multi-winglets similar to the wingtips of eagles and other soaring birds
for improved performance, and evaluated them under a Phase I contract with the Air Force Research Laboratory at Wright-Patterson
Air Force Base, Ohio.
We designed and fabricated
several wind tunnel models and tested them in wind tunnels at Georgia Tech and Ohio State universities for lift and drag information
and laser flow visualization. We confirmed experimental wind tunnel results by Navier-Stokes analysis, and showed that certain
multi-winglet configurations reduced the wing induced drag and improved L/D by 15-30% compared with the baseline wing.
In a follow-on Phase II SBIR contract, STAR,
Inc. produced models of passive and active multiple winglets, and demonstrated them on a Marine Corps DragonEye UAV provided
by the Naval Research Laboratory. The combination of multiple winglets, smart structures, and active control will greatly
improve aircraft range and endurance, and reduction in wing dynamic response will lead to improved ride quality and fatigue
life. Multi-winglets can be retrofitted on general aviation aircraft for improved fuel economy, and can be designed into airliners
to improve fuel economy, ride quality, and wing fatigue life.