Boeing and NASA are teaming up for an interesting experiment.
Boeing has moved an MD-90 to the site in Palmdale, California where it plans to modify the former passenger jet into NASA’s X-66A truss-braced-wing demonstrator aircraft.
Boeing MD-90 (image courtesy of Wikipedia)
Boeing is now gearing up to begin the process of equipping the airframe with the truss-braced wing.
(Image courtesy of Boeing)
“Modification will begin soon, and ground and flight testing is expected to begin in 2028,” Boeing says.
The X-66A is part of NASA’s Sustainable Flight Demonstrator programme, an effort to study technologies that will improve aircraft efficiency.
Boeing plans to replace the MD-90’s low, swept wing with a longer wing mounted atop its fuselage and supported by trusses – a configuration it calls the Transonic Truss-Braced Wing (TTBW).
The long, thin wing will generate less drag than that of a typical airliner, potentially allowing an aircraft equipped with a truss-braced wing to cut fuel consumption by 10%, according to NASA.
There's more at the link.
I'm finding it hard to visualize how a cantilever low-wing 1970's-technology airliner can be transformed into a truss-braced high-wing airliner using 2020's technology. I'm sure it can be done, but it's going to be a radical transformation of the aircraft's basic structure, so much so that it'll end up as, effectively, an entirely new plane. I don't know how much of the original airframe will remain. There's the engines, too: switching from two tail-mounted turbofans to two wing-mounted units of a type and design yet to be finalized - perhaps even a hybrid electric propulsor.
We're all familiar with truss-braced wings, of course; anyone who's seen a high-wing Cessna single-engine monoplane can't help but notice them.
Cessna 172 (image courtesy of Wikipedia)
However, until now they've always been on relatively low-performance, smaller airframes. Translating that simple braced structure to something that can withstand the aerodynamic and other pressures on a higher-speed airliner isn't going to be easy. To make matters even more interesting, the long, thin truss-braced wing will be designed to fold, so that the aircraft can fit into a standard airport bay for loading and unloading - a feature that's not found on small aircraft.
I don't know whether I'll live long enough to fly on one of these aircraft (or even if it will be successful enough to produce in quantity), but it's going to be interesting to watch developments.
Peter
So we are bringing back biplanes?
ReplyDelete@Miguel: Not biplanes, but braced wings. The truss design may be an airfoil itself, but that's not clear yet.
ReplyDeleteWhy, quite soon they will discover the efficacy of the Bi-Plane configuration!
ReplyDeleteWe once again have sailing ships, and soon airplanes with the correct number of wings.
My degree is in Aerospace but it was earned 34 years ago and I never worked in the field, instead going nuclear and then transitioning out of engineering completely.
ReplyDeleteBut...
Dihedral wings (slanted upwards and used on every low wing plane I've ever seen) are better for stability
Anhedral wings (slanted downwards and used on every high wing plane I've ever seen) are better for maneuverability.
Other military factors such as ease of loading and keeping the engines away from the ground in the event that rough landing fields are utilized could also contribute to the military's choice of high wing.
No idea if this is why low wing designs are generally used by civilian aircraft but it could be.
Who had transsonic biplanes for the twenty first and a fifth century? My guess is that the brace wing would be an active airfoil to get the necessary wing area.
ReplyDeleteWhy am I getting thoughts of the Christmas Bullet?
ReplyDeleteHaven't flown since 2002 and don't plan to break that streak, but a folding wing for an airliner sounds, er, interesting. What could possibly go wrong?
I suspect, given the age of the airframe design, that it is significantly overbuilt by modern standards. The new wing structure will probably graft on pretty easily.
ReplyDeletePartnership between Boeing and NASA, more correctly called partnership between Boeing and US taxpayers who fund NASA.
ReplyDeleteThe advantages come mostly from being able to practically operate a very high aspect-ratio wing (thing sailplane) to reduce drag and gain another few tenths of a percent in fuel savings. This is not a new idea. They're just getting more desperate for another incremental fuel savings.
ReplyDeleteDownsides include structural strength (truss braced) and very long wingspan (folding). And relatively low speed (Vmo). Since we have been going backwards on speed for years (737, a320) thats not noticable to paying pax.
My prediction is nothing will come of it. They have already shown practicable fuel savings from blended wing-body design and we dont see it happening. The commercial aircraft world is still building and selling 1950s, cigar-tube designs. Nothing new has happened, engineering-wise since then; its all been propulsion related improvements to fuel burn and thrust.
Shades of Clutch Cargos Bellanca!
ReplyDeleteJune J. made me think. Boing🤔 will be able to use Our money to explore different designs and not have to pay for the experiments.
ReplyDeleteYaKnow, G.E. had the benefit of being handed a prototypical jet engine to work with and funding from We the People and They benefited. The People who paid for their research and development?
NotSoMuch.
@heresolong: Anhedral low-wing plane - F104, dihedral high-wing plane - c-172 (as pictured).
ReplyDeleteI'm just curious how much the extra drag of the bracing struts would diminish the gain from the high-aspect wind. Also the added weiught of a wing folding mechanism.
Me, I'm waiting for them to bring back ridged airships i.e. Zeppelins.
ReplyDelete