Scaled half wing SUGAR model in wind tunnel: NASA Langley,Sandie Gibbs

One of the many innovations proposed in the Boeing SUGAR Volt airliner of the future, a very slender high mounted wing, is getting special attention in the trans sonic wind tunnel at NASA’s Langley Laboratory.

The tests seek to validate intended fuel savings of up to 10% compared to more conventional wings, in a truss braced design that could be incorporated in forthcoming airliner designs sooner and with less developmental risks than those of bringing a hybrid electric/liquid fuel power system to market further into the future.

That’s 10% less fuel per load unit of distance because of the wing, irrespective of the engines slung under it. The ball park promise of engine makers for new power plants in the coming decade is 15% less fuel burn, irrespective of the wing to which they are attached.

The combination of advanced wing derived fuel savings and new engine technologies would produce varying cumulative savings depending on design priorities, whether they were to increase range, or optimise range and structural weight downwards to favour middle or short range flights.  Airliner design is all about range/payload trade offs based on where the airlines see the most demand for their particular purposes.

NASA Langley has posted a brief statement on the upcoming tests here, and a thorough technical review has been published by Aviation Week, which features some previously unseen graphics of the wing assembly that show less sweep than was depicted in this Boeing YouTube which although released almost a year ago, is the most current such video in general circulation.

The latest graphics also show the folding wing system for the first time, although it was mentioned by Boeing in 2012 when it revised the SUGAR Volt proposal in this report in Plane Talking.

Boeing video grab. The outer pods house quick change battery arrays

Boeing was talking about folding the full extension of the SUGAR Volt wing before it announced it would use such a system on the wing of the 777-X series, due in service from late 2020, but maybe a bit sooner according to some insiders.

The 777-X wing doesn’t however need to be braced. It is a lower aspect ratio wing than that of the hybrid electric concept aircraft, and clearly intended for an economical cruise speed of around mach 0.85, while the latter would be a slower plane, but over shorter distance where the difference between mach 0.72 (at a guess) and 0.85 doesn’t really mean all that much in operational terms especially in busier air space.

SUGAR stands for Subsonic Ultra Green Aircraft Research. Its wing concept appears relevant to unducted open rotar and turbo-prop powered designs not just the shrouded or ducted fan shown in the earlier Boeing drawings.

However one of those graphics now shows the wing with large but conventional looking turbo-prop engines, which might give pause to the major makers of such airliners, Bombardier and ATR.

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