Morphing winglets under development promise fuel savings and reduced aircraft noise on landing
Continental Airlines Boeing 757-300 with winglets (photo: Continental)
Mon 16 Feb 2009 – Boeing and Airbus are developing moveable winglets – the fins at the end of a wing – in a bid to build greener, quieter planes, reports New Scientist magazine. Perfected at NASA in the 1970s, conventional, fixed winglets are small, upward extensions to a plane’s wing which minimize the drag experienced by the wing, making it easier for the plane to cut through the air, which in turn boosts its fuel efficiency. Winglets fixed at an angle of around 25 degrees from the vertical – known as the cant angle – can cut an aircraft’s fuel consumption by 3 to 5 percent.
By designing these winglets to move during the flight, changing their angle for take-off, climb, cruise and landing approach, for example, Boeing and Airbus hope to improve fuel efficiency even further, while reducing the noise the aircraft makes during landing.
Boeing has filed a patent application on a winglet that moves using shape-memory alloys (SMAs). Engineers working on an Airbus project are planning to file three patents on their own morphing winglet technology, says Askin Isikveren, chief engineer on the Airbus-funded ‘Morphlet’ project at the University of Bristol in the UK.
“The 3 to 5 percent variation in fuel efficiency today results from using fixed winglets optimized for cruising flight. If we vary the cant angle during flight we can maintain a 5 percent fuel reduction all through the flight.”
Allowing the winglet to flatten completely will also give the wing extra lift at low speeds. “That means less thrust from the engines is needed and so we can have a quieter landing approach,” Isikveren says.
The two plane manufacturers have very different ideas about how to build their morphing winglets, however, and both teams face considerable safety challenges before their technologies can be certified.
Meanwhile, according to Aviation Week magazine, Continental Airlines is expected to take delivery soon of its first winglet-equipped Boeing 757-300 aircraft, which is currently undergoing flight testing, that will allow the twin-engined stretched narrowbody to operate on longer range routes, including those across the Atlantic. The airline estimates that the modification could save each aircraft up to $164,000 in fuel per year. Continental now has winglets on over 270 of its 737 and 757 fleet.
The Aviation Partners Boeing blended winglet design has been fitted to more than 2,730 Boeing 737 and 757-200 aircraft. It is also in the process of being certificated on the 767-300ER aircraft and is being evaluated by Airbus for potential application on the A320 family.