Boeing Truss-Braced Wing concepts & X-66

[publiusr]

The nacelles look to have some growth potential mounted that high up.

 

[mkellytx]

The nacelles look to have some growth potential mounted that high up.

That’s the point as the 737 is maxed out in that respect.

 

[Scott Kenny]

Another trick will be convincing passengers and airline executives that UHB/Open-Fan engines are new and sophisticated, not a rehash of old noisy props.

Though I did see a Piper PA31 fitted with an 11-bladed prop on one engine that greatly changed the noise on takeoff. Sounded much more jetlike. Higher pitched and more like a continuous whistle. Higher pitch means it doesn't carry as far. https://www.mt-propeller.com/en/entw/about_firsts.htm#11 As for why 11 blades? That's a prime number, so there's only one resonant frequency to deal with.

So maybe the high blade count on the Open-Fan will not be as horribly loud.

there is not much of a load bearing structure on the upper part of the fuselage here.

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.

How often has the wing truss collapsed the fuselage in C-130, C-141, C-5, or C-17 crashes?

 

[hesham]

About the Boeing Model-765 and NASA N+4 program;


http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120009038_2012008934.pdf

How to get this report again ?.

 

[flateric]

...

 

[sferrin]

How long until we're back to an actual biplane?

 

[1635yankee]

Another trick will be convincing passengers and airline executives that UHB/Open-Fan engines are new and sophisticated, not a rehash of old noisy props.

Though I did see a Piper PA31 fitted with an 11-bladed prop on one engine that greatly changed the noise on takeoff. Sounded much more jetlike. Higher pitched and more like a continuous whistle. Higher pitch means it doesn't carry as far. https://www.mt-propeller.com/en/entw/about_firsts.htm#11 As for why 11 blades? That's a prime number, so there's only one resonant frequency to deal with.

So maybe the high blade count on the Open-Fan will not be as horribly loud.

there is not much of a load bearing structure on the upper part of the fuselage here.

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.

How often has the wing truss collapsed the fuselage in C-130, C-141, C-5, or C-17 crashes?

If one were to look, one could find a lot of information about noise produced by the "open fan" concept (possibly by searching "propfan acoustics" at ntrs.nasa.gov; the the erstwhile Hamilton Standard Division of UTC did a lot of pioneering work on the concept).

As for high-wings crushing passenger compartments, it's a straightforward structural issue that affects just about all commuter aircraft and military transports and there is a very similar issue with helicopters, with the engines, transmission, and main rotor right over the main cabin.

 

[TomS]

I didn't mean to suggest it's a real show-stopper, or even a major problem, just that the high wing required rethinking the structures compared to existing airliners. I think it came up in the context of comparisons between various iterations of SUGAR -- Refined SUGAR was a low-wing design and SUGAR High was the truss-braced high-wing equivalent, so the wing structure was one of the points of comparison between the two.

 

[1635yankee]

G

 

[TomcatViP]

Similar to me. We are discussing the DC-9 adaptation.
DC-9 is a low wing design.

 

[Moose]

Pratt's Geared Turbofan selected to power X-66A and that has the company salivating about breaking back into the Boeing narrowbody market.

Pratt's Boeing TTBW Win Could Open Future Single-Aisle Competition | Aviation Week Network

The PW1100G geared turbofan will power Boeing's high-wing X-66 later this decade, the first Pratt & Whitney engine to power a Boeing narrowbody since the 757.

aviationweek.com

 

[sferrin]

Another trick will be convincing passengers and airline executives that UHB/Open-Fan engines are new and sophisticated, not a rehash of old noisy props.

Though I did see a Piper PA31 fitted with an 11-bladed prop on one engine that greatly changed the noise on takeoff. Sounded much more jetlike. Higher pitched and more like a continuous whistle. Higher pitch means it doesn't carry as far. https://www.mt-propeller.com/en/entw/about_firsts.htm#11 As for why 11 blades? That's a prime number, so there's only one resonant frequency to deal with.

So maybe the high blade count on the Open-Fan will not be as horribly loud.

there is not much of a load bearing structure on the upper part of the fuselage here.

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.

How often has the wing truss collapsed the fuselage in C-130, C-141, C-5, or C-17 crashes?

If one were to look, one could find a lot of information about noise produced by the "open fan" concept (possibly by searching "propfan acoustics" at ntrs.nasa.gov; the the erstwhile Hamilton Standard Division of UTC did a lot of pioneering work on the concept).

Propfan - Wikipedia

en.wikipedia.org

 

[Scott Kenny]

If one were to look, one could find a lot of information about noise produced by the "open fan" concept (possibly by searching "propfan acoustics" at ntrs.nasa.gov; the the erstwhile Hamilton Standard Division of UTC did a lot of pioneering work on the concept).

Wiki entry notes that the UDFs were louder than the turbofans in the cabin.

As a trained aircraft mechanic, I have a preference for the GE36 type direct drive UDF with many turbine stages. Gear reduction is always a failure point.

Another fun point is flying one of those in icing conditions. Propellers and propfans/UDFs will shed ice load radially into the airframe, which sounds like the plane is getting hit by AA fire. And also requires cabin reinforcement across the line of the blades.

As for high-wings crushing passenger compartments, it's a straightforward structural issue that affects just about all commuter aircraft and military transports and there is a very similar issue with helicopters, with the engines, transmission, and main rotor right over the main cabin.

Which means you design for it. Any plane natively designed with a high wing will be designed around that concern.

The only plane this will potentially be an issue on is the converted low wing tech demonstrator.

 

[martinbayer]

I, for one, am for letting the engineering, environmental, and business processes play out. Good design, bad design - let reality and physics decide.

 

[martinbayer]

I, for one, am for letting the engineering, environmental, and business processes play out. Good design, bad design - let reality and physics decide.

Aaand I just realized that this comment unfortunately applies to the ongoing Titan(ic) drama as well...

 

[Moose]

AirCurrent has a paywalled article discussing CFM Rise on X-66A. The first few paragraphs are readable without a subscription

Boeing will fly CFM’s open fan on Sustainable Flight Demonstrator

After initial testing, Boeing will test CFM’s advanced open fan architecture with a radical configuration of its own. The company sees a long life for X-66A, the NASA lower-emissions test aircraft.

theaircurrent.com

 

[Scott Kenny]

AirCurrent has a paywalled article discussing CFM Rise on X-66A. The first few paragraphs are readable without a subscription

Boeing will fly CFM’s open fan on Sustainable Flight Demonstrator

After initial testing, Boeing will test CFM’s advanced open fan architecture with a radical configuration of its own. The company sees a long life for X-66A, the NASA lower-emissions test aircraft.

theaircurrent.com

I'm having trouble figuring out if the CFM Rise is a geared engine or not. It sounds like it is, but the white paper is singularly non-useful:

key technologies like
multi-variable power control, a pitch actuation
system advanced power gearbox integration.

from: https://www.cfmaeroengines.com/wp-content/uploads/2021/07/CFM_RISE_Whitepaper_Media.pdf

Notice the lack of comma between "a pitch actuation system" and "advanced power gearbox integration."

Sounds like it is geared, and their admin weenie forgot a comma.

I'm not very fond of adding gears to a turbine engine, that introduces an extra failure point. The GE36 and the Safran CROR are much better from my point of view as a licensed Airframe and Powerplant Mechanic.

 

[taildragger]

The nacelles look to have some growth potential mounted that high up.

That’s the point as the 737 is maxed out in that respect.

Please avoid using "737" and "maxed out" in the same sentence.

 

[Rhinocrates]

Not Boeing, but ONERA.

Onera Studies Hydrogen-Powered Truss-Braced-Wing Airliner | Aviation Week Network

Onera's Gullhyver concept for a 200-seat, 4,000-nm-range airliner is being studied under Europe’s Clean Aviation public-private research program.

aviationweek.com

 

[Scott Kenny]

Not Boeing, but ONERA.

Onera Studies Hydrogen-Powered Truss-Braced-Wing Airliner | Aviation Week Network

Onera's Gullhyver concept for a 200-seat, 4,000-nm-range airliner is being studied under Europe’s Clean Aviation public-private research program.

aviationweek.com

*facepalm*

Hydrogen SUCKS as an aircraft fuel. It's just not dense enough! Liquid hydrogen is 14 liters per KG, and then you're also dealing with stuff that is extremely low cryotemps.

 

[1635yankee]

Not Boeing, but ONERA.

Onera Studies Hydrogen-Powered Truss-Braced-Wing Airliner | Aviation Week Network

Onera's Gullhyver concept for a 200-seat, 4,000-nm-range airliner is being studied under Europe’s Clean Aviation public-private research program.

aviationweek.com

*facepalm*

Hydrogen SUCKS as an aircraft fuel. It's just not dense enough! Liquid hydrogen is 14 liters per KG, and then you're also dealing with stuff that is extremely low cryotemps.

But it's great as a turbine engine fuel and its LHV/kg is a couple of times greater than hydrocarbon fuels

 

[Scott Kenny]

Not Boeing, but ONERA.

Onera Studies Hydrogen-Powered Truss-Braced-Wing Airliner | Aviation Week Network

Onera's Gullhyver concept for a 200-seat, 4,000-nm-range airliner is being studied under Europe’s Clean Aviation public-private research program.

aviationweek.com

*facepalm*

Hydrogen SUCKS as an aircraft fuel. It's just not dense enough! Liquid hydrogen is 14 liters per KG, and then you're also dealing with stuff that is extremely low cryotemps.

But it's great as a turbine engine fuel and its LHV/kg is a couple of times greater than hydrocarbon fuels

Sure, for a fixed turbine, like ship propulsion or a gas turbine electrical generator for the grid.

But Hydrogen forces an immense aircraft with low seating capacity.

 

[TomcatViP]

First Boeing X-66A donor MD-90 heads to Palmdale

The first of two former Delta Air Lines McDonnell Douglas MD-90-30 aircraft left storage in Victorville, California early July 21 on a short flight to nearby Palmdale where the aircraft will be sliced and diced to become Boeing's Transonic Truss-Braced Wing configured X-66A.

theaircurrent.com

@admins : should we rename this thread to include the X-66 designation?

 

[1635yankee]

Sure, for a fixed turbine, like ship propulsion or a gas turbine electrical generator for the grid.

But Hydrogen forces an immense aircraft with low seating capacity.

Let's stick some numbers here. Hydrogen has about 40% greater HHV than kerosene, but its density is about 70kg/m^3 vs about 850 for kerosene, so you'd need about 7 m^3 of liquid hydrogen to replace one of kerosene.

 

[Scott Kenny]

Let's stick some numbers here. Hydrogen has about 40% greater HHV than kerosene, but its density is about 70kg/m^3 vs about 850 for kerosene, so you'd need about 7 m^3 of liquid hydrogen to replace one of kerosene.

And that's just tank capacity, not counting all the insulation you will need to keep a -255degC liquid, well, liquid.

IIRC you are looking at something more than 10m^3 in total tankage volume to replace 1m^3 of jet A. Which is why I do not see hydrogen working for aircraft fuel. Prototypes that show an engine can run on hydrogen? sure. But how much of their passenger or baggage area was filled up with the hydrogen tanks?

 

[Prophet141]

Another trick will be convincing passengers and airline executives that UHB/Open-Fan engines are new and sophisticated, not a rehash of old noisy props.

Though I did see a Piper PA31 fitted with an 11-bladed prop on one engine that greatly changed the noise on takeoff. Sounded much more jetlike. Higher pitched and more like a continuous whistle. Higher pitch means it doesn't carry as far. https://www.mt-propeller.com/en/entw/about_firsts.htm#11 As for why 11 blades? That's a prime number, so there's only one resonant frequency to deal with.

So maybe the high blade count on the Open-Fan will not be as horribly loud.


How often has the wing truss collapsed the fuselage in C-130, C-141, C-5, or C-17 crashes?

I have a question regarding this 11 bladed propeller (and other high blade number propellers). I did a quick search and found an article that suggested it would improve not just power but efficiency. I was under the impression that it was a trade off where the larger number of blades increased power for a given blade length and fan velocity (so you can avoid supersonic blade tips), but that it also results in high disk-loading/interference between blades. Why is it that these propellers can have both increased efficiency and power?

Also, I understand that even if a 2 blade propeller is more efficient than a higher number of propeller blades, a plane with a 10,000+ hp turboprop/UDF would need a comically large 2 bladed propeller to reach its full potential.

 

[flateric]

I have a question regarding this 11 bladed propeller (and other high blade number propellers).

https://www.secretprojects.co.uk/threads/worlds-first-propeller-with-11-blades-completes-first-test-flight.40737/

 

[Scott Kenny]

I have a question regarding this 11 bladed propeller (and other high blade number propellers). I did a quick search and found an article that suggested it would improve not just power but efficiency. I was under the impression that it was a trade off where the larger number of blades increased power for a given blade length and fan velocity (so you can avoid supersonic blade tips), but that it also results in high disk-loading/interference between blades. Why is it that these propellers can have both increased efficiency and power?

Also, I understand that even if a 2 blade propeller is more efficient than a higher number of propeller blades, a plane with a 10,000+ hp turboprop/UDF would need a comically large 2 bladed propeller to reach its full potential.

Higher blade counts mean each blade can be narrower, which has a better lift/drag ratio. More lift means more thrust from the prop in that specific case.

Higher blade counts can also be smaller diameter, which lets you either spin the prop faster at the design stage, or results in lower propeller tip speed at the engine's max rpm as a retrofit.

 

[Helicoprion]

An even better look at the MD-90 donor fuselage.

NASA, Boeing, Provide a Peek at What the X-66A Will Look Like

NASA and Boeing have unveiled a new livery for the X-66A aircraft that will be produced through the agency’s Sustainable Flight Demonstrator.

www.nasa.gov

 

[aonestudio]

Airplane Arrives at Boeing Site for X-66A Modification

Boeing [NYSE:BA] has ferried an MD-90 airplane to the site where it will be modified to test the Transonic Truss-Braced Wing (TTBW) configuration as part of NASA's Sustainable Flight Demonstrator...

boeing.mediaroom.com

 

[aonestudio]

https://twitter.com/x/status/1709194476520882594

View: https://twitter.com/RaytheonTech/status/1709194476520882594

https://www.rtx.com/news/news-center/2023/10/03/rtx-selected-by-boeing-for-x-66a-nasa-sustainable-flight-demonstrator-project

 

[hesham]

I think that,may if I develop in the design something,it'll have a better performance.

 

[Moose]

Paywalled article, Boeing has begun deconstructing the aircraft which will be rebuilt as X-66A

Boeing begins transforming MD-90 into NASA’s X-66A demonstrator

Boeing has started dismantling and scanning an old MD-90 as part of a multi-year NASA-supported project to transform the former passenger jet into the X-66A truss-braced-wing demonstrator.

www.flightglobal.com

 

[flateric]

I didn't go out of my monthly free views limit so here it goes.

 

[Helicoprion]

3D STL of the X-66a

X-66 3D File - NASA

The X-66 is now available to print in 3D!

www.nasa.gov

 

[Grey Havoc]

Boeing updates X-66A progress as details of PW102XG engines emerge

Boeing has disclosed fresh details on the progress of the X-66A truss-braced-wing demonstrator it is developing under a NASA-backed project, including confirmation that the aircraft will be powered by a derivative of the Pratt & Whitney PW1500G engine designated the PW102XG.

www.flightglobal.com

 

[Scott Kenny]

Boeing updates X-66A progress as details of PW102XG engines emerge

Boeing has disclosed fresh details on the progress of the X-66A truss-braced-wing demonstrator it is developing under a NASA-backed project, including confirmation that the aircraft will be powered by a derivative of the Pratt & Whitney PW1500G engine designated the PW102XG.

www.flightglobal.com

It's really going to take some good sales pitch for any open rotor or unducted fan engines...

 

[1635yankee]

It's really going to take some good sales pitch for any open rotor or unducted fan engines...

It probably would, which may be why there are no plans to do so.

 

[taildragger]

It probably would, which may be why there are no plans to do so.

Boeing has pointed out that the X-66 configuration is well suited to an engine with blades so probably sees re-engining down the road as a possibility. The purpose of the airplane is aerodynamic and structural research though so throwing a another innovation into that mix in the early stages would probably be unwise.

 

[publiusr]

Shoulder mount Gull wings with engine nacelles atop them allow fans behind the wings for the best clearance.