If you think that you've been seeing some funny-looking airliners in the past couple of months, you're not imagining things. On February 18th, a United Airlines Boeing 737-800 made the world's first commercial flight by an aircraft equipped with fuel-saving Split Scimitar Winglets.
Regular blended winglets are now quite common on commercial aircraft, as they improve aerodynamics and thus reduce fuel consumption. Made by Aviation Partners Boeing, the Split Scimitar Winglets reportedly do an even better job – when retrofitted onto United's existing Next Generation 737 Blended Winglets, they should reduce fuel consumption by two percent per aircraft.
The airline plans to add the new winglets to its entire fleet of 737, 757 and 767 airliners. By doing so, it estimates that it will save "more than 65 million gallons [246,051,780 liters] of fuel a year, equivalent to more than 645,000 metric tons [710,991 tons] of carbon dioxide and $200 million per year in jet fuel costs."
Retrofitting Split Scimitars into existing blended winglets involves adding strengthening spars, aerodynamic "scimitar tips," and a large ventral strake (the bit that points down).
Yesterday, Southwest Airlines announced that it had also started using the Split Scimitar Winglets on one of its 737-800s. The company plans on retrofitting 52 existing planes, and having the winglets pre-installed on 33 new aircraft.
Numerous other airlines have placed orders for the winglets, so expect to start seeing them on a runway near you soon.
Sources: United Airlines, Southwest Airlines, Aviation Partners Boeing
Sort of related, I stumbled on a video about some predictions of the future made in the 1920's and 1930's. At about 4:10 they talk about boats and aerodynamics and its actually pretty interesting how close they come: https://www.youtube.com/watch?v=czr-98yo6RU#t=250
Looking back on videos like that its kind of surprising it took automobiles so long to adopt an aerodynamic shape.
It was found a long while ago that downward pointing blended winglets had a higher effective wingspan extension than upward pointed, just that tipping them down was more difficult to package and had a higher risk of ground strike. (Vertical wing tip fences (as in Airbus) actually do very little to improve anything apart from somewhere to put the airline adverising, and ads a little longitudinal stability)
Boeing felt that the raked wingips as on the B787 were more effective, at preventing low, slow and heavy wingtip turbulence and reversed airflow at the tip, however lateral extensions can't be used on existing aircraft, because they wouldn't fit into their designated airport gates. Ans the airframes may not cope with the additional bending moment.
With all these variations (and many more under examination) all we are trying to do is copy the eagles and other soaring birds who use their tip feathers as variable geometry efficiency improving devices
The design for this "invention appears to stem from the mid 1970's with work at NASA, understanding what is happening at the wing-tip of an aircraft is important, the hard thing is to improve the efficiency at all staged of the flight, not just on take-off and landing with these fixed aerofoil extensions.