Fuel efficiency is a key driver in aircraft design, allowing some combination of lower fuel costs and/or higher payloads. Wing-tip devices such as winglets — attachments to the tip of aircraft wings — are commonly used to minimize wing-tip vortices, reducing aircraft drag by two to three drag counts (e.g., allowing for 400-600 pounds of additional payload at the same fuel cost). While lowering drag overall, some additional drag is induced at the root of a winglet.
NASA Ames has developed a novel patent-pending technology that employs the injection of air at the trailing edge of a winglet to further reduce drag, resulting in fuel savings in the operation of the aircraft. This technology can be applied to aircraft (large or small) that currently use winglets and more particularly, to wing-tip devices with the addition of pores for reducing vortex drag.
This can be done through either passive or active designs. In the passive design, the leading edge of the winglet is made porous (e.g., holes machined, fabricated using mesh, etc.) to ingest air, and ducting placed within the wing carries that air to the trailing edge where it is injected. In the active design, air lines already within the wing are tapped to obtain flow from an existing air source, such as the bleed air from the engines, and the air flows out through trailing-edge openings in the winglet to facilitate trailing-edge air injection.
A passive wing-tip blown effect would reduce vortex drag and possibly provide additional lift. In addition, it could also have an influence on reducing pressure-induced drag and friction drag. Reduction in vortex drag would result in fuel savings in the operation of the aircraft.