Boeing unveiled a new “advanced technology winglet” design for the 737 Max on Wednesday, saying that it will provide up to an additional 1.5-percent fuel-burn advantage on top of the 10- to 12-percent improvement already advertised for the re-engined narrowbody.

Michael Teal, 737 Max chief project engineer, said the design combines the raked wingtip feature of the Boeing 787 Dreamliner and 747-8 with a “dual feather” concept winglet consisting of an upper and a lower piece.

“To get more efficiency with just an upper winglet, you have to add more height to the top the winglet. This adds weight and negates any additional benefit,” Teal explained in a teleconference. “The lower part of the winglet lets us, in essence, cheat a bit on span by balancing the effective span increase uniquely between the upper and the lower parts. This makes the system more efficient without adding more weight, thereby reducing drag and improving the overall fuel burn. The dual-feather winglet creates the fuel-burn improvement at cruise, giving a total fuel-burn improvement of up to five-and-a-half percent relative to having no winglet at all.”

If realized in service, the percentage gain of the new Boeing winglet would exceed the 3.5-percent fuel-burn improvement Airbus claims for the A320 equipped with new “Sharklet” wingtips.

The dual-feather winglet design is Boeing’s intellectual property. The company currently does not plan to retrofit it on 737NGs equipped with blended winglets from Seattle-based Aviation Partners, said Beverly Wyse, 737 program general manager. “We may change that decision in the future, but right now we’re just focused on introducing it on the Max,” she said.

The Aviation Partners Boeing (APB) joint venture now supplies blended winglets for 737NGs, 757s and the 767-300ER. “We’ll continue to have a strong relationship with APB. They will continue to be our partner for the winglets we have on the 737 Next Generation as well as the 757 and the 767,” Wyse said.