MD-90 Test Bed For Trussed Wing Demonstrator Project


Boeing has chosen an old McDonnell-Douglas airliner as the test bed for the Transonic Truss Braced Wing that it hopes will eventually lift a new-generation passenger aircraft toward sustainability. NASA has contracted Boeing to build a Sustainable Flight Demonstrator and key to the design is a set of long, thin wings that are braced by large trusses that also work as lifting surfaces. It will be known as the X-66A, and the actual prototype is expected to fly in 2028, but in the meantime the old rear-engined descendent of the DC-9 will test the wing concept. It was ferried from Victorville to Boeing’s Palmdale, California, facility on Aug. 17.

“We at NASA are excited to be working with Boeing on the X-66A Sustainable Flight Demonstrator making critical contributions to accelerate aviation towards its 2050 net-zero greenhouse gas emission goal,” said Ed Waggoner, deputy associate administrator for programs in the NASA Aeronautics Research Mission Directorate. Boeing and NASA are hoping for a 30 percent reduction in fuel burn and emissions with the skinny wings and trusses.

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  1. Uh OH! NASA Armstrong will be spending TONS of money on another crazy “green” X-airplane idea. The notion that a large jet airplane is ‘sustainable’ or can be made “net zero” is laughable! Oh well … at least another “deputy associate administrator’ and his minions will have jobs into retirement. Time to cut off the funding to NASA.

    • I imagine there were some who thought the NACA cowling was a silly “green” idea that would never prove useful. Research projects like this are supposed to try out “crazy” ideas to see what can be learned from them. Even if they don’t translate directly into commercial products, there’s something to be learned from it.

    • I guess you gents haven’t heard of diminishing returns on an investment? OR, good money chasing bad? Kinda like the X-47 “Maxwell” that was gonna take a Tecnam P2006 multi-engine airplane, re-wing it w/ 6 self-fairing electric motors on each low drag high aspect ratio wing for climb and a larger wing-tip mounted cruise engine. THAT NASA Armstrong project started in 2016 with a $40M budget. It ran on and on and on, slowed due to covid (I’ll give ’em that) but — finally — after running over budget by 120% to $87+M, someone finally pulled the plug on it. The taxpayers didn’t get an airplane, the research yielded nothing tangible but .. oh boy … the boys at NASA Armstrong stayed employed. Someone up high shoulda shut that idea down immediately after passing $40M … IF it ever started at all.

      Given my heartburn with that project, at Airventure, I went to the forum on the X-47 Maxwell. The people putting on the forum were not only trying to defend the indefensible, they were an embarrassment to NASA and aviation. When I vociferously challenged them, they knew they were “had” and started tap dancing with excuses. Finally, one of ’em says, … ‘well, our people learned some lessons and the vendors we worked with learned some things. Really! For $87M, NASA could have paid for ~200 PhD degrees for deserving employees and gotten a helluva lo more bang for each buck spent.

      I, for one, am damn tired of the incessant use of “green” this and “sustainable” that … all the while wasting MY money. I spent 27 1/2 years in the business of flight test and know darned well how it all works. Wasting money isn’t part of it. This project will likely waste hundreds of millions and have little to show for it when the final page is turned. Let’s just see.

      IMHO, NASA is now in the business of coming up with nutty ideas and justifying the spending of huge sums of money chasing same. The NASA Dryden I remember in the 70’s and 80’s — and worked with — is a far cry from where NASA Armstrong is today. THAT is MY beef with them.

      If those of you think all of these nutty ideas are good … send them YOUR money … stop spending mine.

    • Thinking about it some more, I think NASA Armstrong should buy an Italian Caproni Ca60 Noviplano and add 3 more wings and put 16 electric motors on each wing…. these ideas are THAT nutty. (Google it!) The ‘greenies’ would love it …

  2. I wonder how they will deal with the interference drag at the strut to wing and strut to fuselage attachments. Those have always contributed to the Cessna headwind, hard to imagine the transonic version of that!

    • I believe from previous articles on this, they have used modern CFD modelling to find ways to cut down on the drag. One advantage a jet has over a piston-powered plane like the 172/182 is that the weight-to-drag-reduction penalty is more favorable for larger planes than smaller ones. And as Cirrus has shown, smart fuselage and wheel fairing designs can generate fairly sizable drag reductions.

  3. Sustainability. I’m sick of the word. Hooey!

    This is about like putting airflow skirts and wheel covers on the big semi-trailers to save fuel. Oh yeah, and like worrying about silverware and so forth on airplanes (to save weight, for the same reason).

    “Sustainable”, “Green” (that one’s getting a little dated…), so forth and so on = we’re willing to say and do what we think you want, in order to part you from your money. That’s what I hear. Sickening.

    • How can this be, Hans? NASA’s X-59 techno demonstrator will make commercial supersonic flight both acceptable to the masses on the ground and affordable to the ultra rich?? Maybe Boom is gonna hire PiBor as a Captain ??