Boeing Truss-Braced Wing concepts & X-66

alberchico said:
Assuming that Boeing rolls the dice and launches a 737 replacement based on this concept, what would be the timeframe for entry into service ? Late 2030's ?
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According to Boeing, they're waiting for the propulsion side of the industry to take it's next major step before they commit to a new airframe. So, we need to see how soon the unducted, or hydrogen, or ultra-high-bypass, or hybrid engines are ready.
 
Moose said:
alberchico said:
Assuming that Boeing rolls the dice and launches a 737 replacement based on this concept, what would be the timeframe for entry into service ? Late 2030's ?
Click to expand...
According to Boeing, they're waiting for the propulsion side of the industry to take it's next major step before they commit to a new airframe. So, we need to see how soon the unducted, or hydrogen, or ultra-high-bypass, or hybrid engines are ready.
Click to expand...

Can't imagine it will be hydrogen; the infrastructure hurdles are just too high. Same for hybrid, probably, though Boeing has combined this shape with hybrid-propulsion in SUGAR Volt. (The pods are batteries, apparently.)

551e5078-611a-4459-8b6e-ab83fa2941bf-full-jpg.574585


So, my money would be on unducted fans or UHB (which are the same thing, aren't they?) But there's a lot of institutional resistance to anything that looks like a propeller.
 
TomS said:
Moose said:
alberchico said:
Assuming that Boeing rolls the dice and launches a 737 replacement based on this concept, what would be the timeframe for entry into service ? Late 2030's ?
Click to expand...
According to Boeing, they're waiting for the propulsion side of the industry to take it's next major step before they commit to a new airframe. So, we need to see how soon the unducted, or hydrogen, or ultra-high-bypass, or hybrid engines are ready.
Click to expand...
So, my money would be on unducted fans or UHB (which are the same thing, aren't they?) But there's a lot of institutional resistance to anything that looks like a propeller.
Click to expand...
UHB fans with ducts are definitely still a thing, so we might need to re-purpose a old phrase from Geometry and say "All Unducted are UHB, but not all UHB are Unducted."
 
NASA never did upload the whole PC, but CNET did:
View: https://www.youtube.com/watch?v=3QgwRgbQX5Q

Notably they neither committed to nor ruled out asking the Air Force for an X-plane designation. They also left open the question of exactly what fuselage and engines the demonstrator aircraft will use.
 
How will they certificate a truss for safe life?
 
This contract is essentially NASA and the US Government paying Boeing to resurrect its aircraft design ability. Critical for national security, but I would have preferred that it be accompanied by a commitment to fire the entire Boeing board.
 
TomS said:
Moose said:
alberchico said:
Assuming that Boeing rolls the dice and launches a 737 replacement based on this concept, what would be the timeframe for entry into service ? Late 2030's ?
Click to expand...
According to Boeing, they're waiting for the propulsion side of the industry to take it's next major step before they commit to a new airframe. So, we need to see how soon the unducted, or hydrogen, or ultra-high-bypass, or hybrid engines are ready.
Click to expand...

Can't imagine it will be hydrogen; the infrastructure hurdles are just too high. Same for hybrid, probably, though Boeing has combined this shape with hybrid-propulsion in SUGAR Volt. (The pods are batteries, apparently.)

551e5078-611a-4459-8b6e-ab83fa2941bf-full-jpg.574585


So, my money would be on unducted fans or UHB (which are the same thing, aren't they?) But there's a lot of institutional resistance to anything that looks like a propeller.
Click to expand...
There's market pressure against anything that looks like a propeller also. One of the reason for the rapid adoption of regional jets was a passenger preference demonstrated in load factors and pricing power.
 
I'd be very interested in seeing this configuration with a UHB (especially an unducted one)!
 
Now, by wholly unforced chosen education I'm just your average German good old fashioned rocket/hypersonic airbreathing propulsion aerospace engineering university graduate suburban kinda guy, but I still fail to understand what is the simple dumbed down explanation of how in the most sacred of all bovines electric whirligigs would/could replace good old fashioned fossile and/or LH2 fuel burning powered turbine based engines with respect to maintaining the current staunchly subsonic altitude/velocity airliner flight envelope vs. CO2 production?
 
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Methane is cheap and harvested. Every cubic meter of it used as a fuel is one that is not ejected into the atmosphere with its known cascading effect.

Fuel cells usage of methane is also more efficient that burning it. You also restricts Nox production.

Methane can then be burned only for high load usage.
 
The Air Current has a piece, paywalled though the opening few paragraphs are free
theaircurrent.com

NASA gives Boeing a second shot at reshaping commercial aviation

The U.S. puts its “finger on the scale” for new Boeing jetliner development. Company awarded $425 million to develop its truss-braced wing concept into Sustainable Flight Demonstrator for a 2028 first flight.
theaircurrent.com theaircurrent.com
 
TomcatViP said:
Methane is cheap and harvested. Every cubic meter of it used as a fuel is one that is not ejected into the atmosphere with its known cascading effect.

Fuel cells usage of methane is also more efficient that burning it. You also restricts Nox production.

Methane can then be burned only for high load usage.
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That's fine, but I'd like to know what the projected top airspeed of any *exclusively* electric driven airplane engine would be.
 
Speed for electric aircraft is limited by the propulsion mode. Propeller ones are only limited like any other Propeller aircraft.

The difference is in range since electric propulsion is always confronted to power density.
 
That's pretty much my understanding, so I remain mystified why there's speculation/chatter of all electric airliners when presumably purely electric propulsion will not be able to routinely match conventional turbofan powered airliner airspeeds of up to Mach 0.85.
 
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(The pods are batteries, apparently.)
Am I alone in thinking that if those pods hold 'lithium' cells, would be wise to have a way to discard pods that spontaneously ignite ??

Equivalent of fuel-dump before emergency landings...
 
From memory, the SUGAR Volt concept from 5-10 years or so ago depended on batteries with about 30x the current kWh/kg... Concepting is easy when you can use technology which doesn't exist yet

From the range of NASA studies it seemed that configuration changes for narrow bodies made pretty limited impact (<10% ish) compared to the more advanced tech assumptions that got you towards ~50% block fuel reductions.

It'll be interesting to see what works out best at full scale e.g. TTBW or the semi-aeroelastic wing
 
Boeing's Calhoun has declared the old "NMA" concept dead and the company seems to be embracing the idea of TTBW being the configuration for their next airliner.
www.seattletimes.com

Boeing CEO offers hints about next new airplane and a radical tech shift

Boeing CEO Calhoun expressed confidence in recovery and catching Airbus. He said a new airplane concept developed with NASA could produce Boeing's next new jet
www.seattletimes.com www.seattletimes.com
 
Its going to be exciting to see this project take shape. Shame that we wont see it enter service until at least 2035. It also appears that Boeing will concentrate all their resources on developing this concept as a 737 replacement and will leave the 757 replacement market to the A321XLR.
 
RavenOne said:
These ultra-thin folding wings measure more than half the length of a football field! Our new Transonic Truss-Braced Wing concept is revealed at #aiaaSciTech today. #TheFutureIsBuiltHere Read more: http://bit.ly/2VAnHks
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"Half the length of a football field"* isn't that big. Several current or recent production aircraft exceed that. What's novel is the very high aspect ratio.
 
Why are they using an old MD90 and not something newer like a 737 airframe?
 
Too wide to be representative (and probably that fuselage section also differs too much or is too specific to be representative).
 
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1635yankee said:
RavenOne said:
These ultra-thin folding wings measure more than half the length of a football field! Our new Transonic Truss-Braced Wing concept is revealed at #aiaaSciTech today. #TheFutureIsBuiltHere Read more: http://bit.ly/2VAnHks
Click to expand...
"Half the length of a football field"* isn't that big. Several current or recent production aircraft exceed that. What's novel is the very high aspect ratio.
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Yes, 180 ft is big. Both 737 and A320 are a little under 118 ft, so unless they fold it’s a problem to use existing gates (777X had this problem as well). Pretty much all of those bigger wings you reference are on twin aisle aircraft that use a different gate spacing.

What’s novel about these very high aspect ratio wings is that they’re transonic. That causes all kinds of fun aeroelastic stuff, as do folding tips. It’s probably impossible to make them out of metal, but with composites you can do some neat stuff that makes it possible. The other issue would be handling qualities which would be a bit different from current wings, but again with FBW some of the nastier things can be mitigated.
 
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Hood said:
Why are they using an old MD90 and not something newer like a 737 airframe?
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Because it’s available. Most of the 737NG’s are still in use, Max’s can’t get delivered fast enough so you’d be left with a classic if you went the 737 route. The MD90’s on the other hand are being retired and not converted into cargo jets like many of the NG’s are. So, it’s a bit easier to get ahold of one and Boeing would rather want to make money on a cargo conversion for an NG.
 
mkellytx said:
Hood said:
Why are they using an old MD90 and not something newer like a 737 airframe?
Click to expand...
Because it’s available. Most of the 737NG’s are still in use, Max’s can’t get delivered fast enough so you’d be left with a classic if you went the 737 route. The MD90’s on the other hand are being retired and not converted into cargo jets like many of the NG’s are. So, it’s a bit easier to get ahold of one and Boeing would rather want to make money on a cargo conversion for an NG.
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Also, I'm thinking that the T-Tail keeps the tailplane out of the way of any 'unexpected' airflow conditions generated by the high mounted wing and engines, as well as the struts . . .

cheers,
Robin.
 
robunos said:
Also, I'm thinking that the T-Tail keeps the tailplane out of the way of any 'unexpected' airflow conditions generated by the high mounted wing and engines, as well as the struts . . .
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Just so. Most high-wing jets with engines on the wings have T-tails to get the horizontal stabilizers out of the engine exhaust flow. And Boeing has been showing their truss-braced wing designs as high wings with T-tails since at least SUGAR High (2008), so I doubt it's a coincidence that they selected a T-tail aircraft as the basis for the demonstrator.
 
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robunos said:
mkellytx said:
Because it’s available. Most of the 737NG’s are still in use, Max’s can’t get delivered fast enough so you’d be left with a classic if you went the 737 route. The MD90’s on the other hand are being retired and not converted into cargo jets like many of the NG’s are. So, it’s a bit easier to get ahold of one and Boeing would rather want to make money on a cargo conversion for an NG.
Click to expand...
Also, I'm thinking that the T-Tail keeps the tailplane out of the way of any 'unexpected' airflow conditions generated by the high mounted wing and engines, as well as the struts . . .

cheers,
Robin.
Click to expand...
Actually, horizontals positioned in the wing down wash is considered beneficial for stability and control since they increase the effective AOA and the effectiveness of the surface. As @TomS pointed out it does keep them out of the engine exhaust, particularly the hot core gases which composites generally don’t like. T tails don’t come without their issues, namely deep stall, where the wing/fuselage can blank out the horizontal, where a conventional horizontal will see “clean air” at higher AOA and maintain effectiveness. There’s no free lunch!
 
I will be interested to see how they process for the wing relocation from bottom to top (DC9 have low mounted ones).
 
TomcatViP said:
I will be interested to see how they process for the wing relocation from bottom to top (DC9 have low mounted ones).
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It looks like the trusses attach to the old low wing mounting points. Given that they are cutting the fuselage to remove a section, adding internal structure there to connect the new high wing to the fuselage seems obvious. I wonder if the primary loads might not be through the trusses, though, into the old main wing structure.
 
mkellytx said:
T tails don’t come without their issues, namely deep stall, where the wing/fuselage can blank out the horizontal, where a conventional horizontal will see “clean air” at higher AOA and maintain effectiveness. There’s no free lunch!
Click to expand...

Indeed. Deep stall characteristics seem to be one of the main focus areas for future research.

www.techbriefs.com

Predicting Buffet Onset on the Transonic Truss-Braced Wing

Boeing will work with NASA to build, test, and fly a full-scale demonstrator aircraft and validate technologies aimed at lowering emissions.
www.techbriefs.com www.techbriefs.com
 
@TomS : there is not much of a load bearing structure on the upper part of the fuselage here. But I do agree that the bracing struts will convey part of the load to the original wing attachment points.
 
TomcatViP said:
there is not much of a load bearing structure on the upper part of the fuselage here.
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True. It's possible that they will simply "cheat" and build an internal frame to carry the loads down from the top of the fuselage to the existing load structures in the lower fuselage. After all, this experimental aircraft doesn't need to have a clear cabin for passengers anymore.

A commercial version would need a different load structure entirely. And that is one item I've seen mentioned as an issue -- you end up with a rather strong and relatively heavy structure sitting at the top of the fuselage, ready to come down into the cabin in a crash.
 

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