Thursday, 7 February 2013

WINGTIP DEVICES (WINGLETS)



It’s time to give an overview to our readers about the cool and stylish looking aircraft parts.
Wingtip devices increase the lift generated at the wingtip and reduce the lift-induced drag caused by wingtip vortices, improving lift-to-drag ratio. This increases fuel efficiency and range. Wingtip devices can also improve aircraft handling characteristics.

WHAT ARE WINGTIP VORTICES: - Wingtip vortices ARE the twin tornados formed by the difference between the pressure on the upper surface of an airplane's wing and that on the lower surface.
High pressure on the lower surface creates a natural airflow that makes its way to the wingtip and curls upward around it. When flow around the wingtips streams out behind the airplane, a vortex is formed. These twisters represent an energy loss and are strong enough to flip airplanes that blunder into them

NECESSITY IS THE MOTHER OF INVENTION:-
There is an interesting history behind the invention of winglets. In 1976, shortly after an energy crisis sent fuel prices skyward, Richard Whitcomb, a NASA aerodynamicist, published a paper that compared a wing with a winglet and the same wing with a simple extension to increase its span. As a basis for comparing both devices, the extension and the winglet were sized so that both put an equal structural load on the wing. Whitcomb showed that winglets reduced drag by about 20 percent and offered double the improvement in the wing's lift-to-drag ratio, compared with the simple wing extension.
DESIGNING OF WINGLETS.
The airflow around winglets is complicated, and winglets have to be carefully designed and tested for each aircraft.
CANT:  the angle to which the winglet is bent from the vertical.
TOE   : the angle at which the winglets' airfoils diverge from the relative wind direction.
These determine the magnitude and orientation of the lift force generated by the winglet itself. By adjusting these so that the lift force points slightly forward, a designer can produce the equivalent of thrust.
TYPES OF WINGTIP DEVICES.

BLENDED WINGLETS
A blended winglet is attached to the wing with smooth curve instead of a sharp angle and is intended to reduce interference drag at the wing/winglet junction.
BLENDED WINGLETS 
In 2009 Airbus launched a new blended winglet design which the company called a "sharklet", designed to enhance the payload-range performance of the A320 Family. Offered as a retrofit option, sharklets are expected to result in a reduced fuel burn of at least 3.5 percent over longer sectors, corresponding to an annual CO2 reduction of around 700 tons per aircraft. The A320 will be the first model fitted with sharklets, which will be delivered in 2012


WINGTIP FENCE
WINGTIP FENCES
A wingtip fence refers to the winglets used in some Airbus airplane models which include surfaces extending both above and below the wingtip.  Wingtip fences are the preferred wingtip device of Airbus, employed on all their airliners except for the A330 and A340 families. . The Airbus A300 was actually the first jet airliner to feature this kind of solution by default, but it was a very small version of the tool.


RAKED WINGTIPS
Raked wingtips are a feature on some Boeing airliners, where the tip of the wing has a higher degree of sweep than the rest of the wing. The stated purpose of this additional feature is to improve fuel efficiency and climb performance, and to shorten takeoff field length.