Will MoM be a TTBW?

a reply to: Zaphod58

It works for Cessna!

a reply to: justwanttofly

The MoM is coming and will most likely be designated the 797. Or at least that is the rumbling I'm hearing within Boeing.

That certainly looks different from most commercial jets now.




The wing will be longer won't it.

Will the wing have to fold to land at airports now?

a reply to: grey580

Yes it will be longer, and probably not. They'll have to use the gates for larger aircraft though.

a reply to: Zaphod58

Concorde has been retired for 15 years now, the MD-11 is no more, and the 747 is about to become another flying memory.

And yet, we may live to see our airliner turn into a bunch of giant jet-powered Cessna's.

It's stuff like this that sometimes makes me think I'm living in some sort of Demolition Man-style nightmare future...

a reply to: Barnalby

And it will save millions a year. Which is better? An SST that costs over $5,000 a seat round trip, or an aircraft that saves the airlines millions and brings ticket costs down?

Just because something doesn't look like it's from the 29th century doesn't mean it isn't advanced as hell.

The MD-11 was one of the worst commercial aircraft produced. It was actually worse than the DC-10.

a reply to: Zaphod58

Those spars, I suppose you could use them for more than just support, sort of like near vertical stabilisers although I have no idea if that would be a useful thing where they are placed on the CoG?

a reply to: Zaphod58

I know the economics of the wing are great and all, and I know the high-wing desogn also solves the problem of how to reconcile ever-growing fan diameters with a desire to minimize landing gear length (and weight) as well as helping to keep floor heights and other logistical footprint issues in line with current aircraft and facilities.

But still, the idea of subsonic airliners one day resembling giant Shorts 360s still feels dirty and wrong.

And the MD-11 may well have been a flying turd, but it was a cool-looking flying turd...

Also, speaking of fuel-saving concepts that still feel kind of wrong, whatever happened to the UDF?

Only because if we're going for hideous, I would love to see someone throw together a UDF upgrade for the A380 that nets us something resembling the love child of The Pregnant Guppy and a Tu-114...

originally posted by: Barnalby
a reply to: Zaphod58
Also, speaking of fuel-saving concepts that still feel kind of wrong, whatever happened to the UDF?

Cheaper fuel and the MD-90 if I remember correctly.

a reply to: Barnalby

So basically, build more aircraft to make flying harder on the general public because they look cooler.

a reply to: Zaphod58

I'm all for the happy medium. I saw my first Qatar A350 in the flesh last week, parked alongside a JAL 787, and thinking of those two designs, they both clearly have made tremendous strides in terms of advancing efficiency in their segment, and yet they're both absolutely beautiful designs (well, the 787 is at least) that prove that even a decade worth of CFD work still validates the old saying that "if it looks right, it'll fly right".

The TTBW, on the other hand, just doesn't seem to hold up to that same scrutiny. I see it as potentially making big waves in the world of regional jets, but I also feel that the short/medium haul market has survived all manner of "disruptive" fad technologies that were just too weird or too specialized to really be able to take over the 737/A320/DC-9 market.

Basically, look at it this way. If I'm a major US buyer (and we're still the single biggest market for 737/757-sized aircraft), what I'm looking for more than anything else is flexibility. If I'm Jetblue/Southwest or any of the other carriers (AKA everyone else) who are following them down the path to single-type domestic fleets, what I value more than anything else is flexibility. For instance, that SWA 737 based at Love Field might have one day where it flies DAL->ATL->ORF->BWI->BOS->CLT->DAL and never spends more than 90 minutes in the air, and the next day it's flying DAL->LAX->BWI->PHX->DAL where most of its legs are really medium bordering on long-haul service. The story is the same for JetBlue's A320s as well as the growing 737/A320 fleets of other US carriers. Essentially, if I'm an airline and I'm dropping $45m/airframe on a new aircraft aircraft, I need it to be able to follow the demand and make me money every day of the week, regardless of whether that means shuttling consultants around on 500 mile hops all day on Monday-Thursday, or whether it means flying families cross-country on the weekends, and the days of airlines being able to justify specialized fleets for different service types died either with deregulation or the post-9/11 market shake-ups.

Were the market unchanged from 1975(both in terms of fuel pressures and regulatory climate), there absolutely would be a place for a TTBW aircraft, with the speed and drag penalties that it design imparts, to serve in the 737-200's old segment feeding hubs at opposite ends of the countries while 787's and 777MAXs shuttle passengers between the hubs. But that era is past, and it seems to me like the airlines have made it pretty clear that they would rather have (in the size segment where the TTBW makes the most sense) to eat the 3-5% efficiency decrease that a "jack of all trades" design like the 737MAX will have relative to the TTBW on a day when it's stuck doing regional hops, in order to gain back an extra 3-5% in terms of efficiency (on top of the 10-15% higher cruise speed) on days when that same steerage bus is pressed into long-distance service.

It's the same reason why 787's and 777's are killing the 747, and the regional/domestic market doesn't seem to have the same tolerance for "unicorns" that can only handle a certain specific type of service that has kept the A380 wheezing along in its segment. Just ask the folks at Bombardier trying to explain the CSeries' sales how slightly exotic short-haul optimized aircraft are faring in the current market.

a reply to: Barnalby

Fortunately the airlines couldn't care less if it looks good. They're about efficiency and savings. They learned a hard lesson in recent years that fuel prices aren't stable, despite holding fairly steady for so long.

As for range and market, we don't know anything about what market they're looking at. It could be regional, it could have more range than the 757. This design is flexible enough that it could be either.

a reply to: Zaphod58

No, they don't seem to care about what it looks like, but passengers can/do and I'd imagine that the airline boards will as well, if only subconsciously.

And then there's the issue of maintenance. It seems like one of the major benefits of this design (killer aspect ratios) is dependent on a wingspan that'll be an absolute no-go for any terminal designed to service A320s and 737s, so folding wingtips will be a necessity. So now, add another set of hydraulic/electric actuators to maintain (and the weight that they and the articulating wing spar bring with them), along with a second set of structural spars which now require all the normal inspection/PMI work to the existing list of things that need to be maintained, which will now be more difficult than before since it's a high-wing design.

It'll be interesting to see how the 777MAX's folding wingtips will fare in commercial service. If there are issues, that alone could kill the TTBW outright before a prototype design is even approved.

And that's ignoring the issue of where the fuel is going to go.

Ironically, it seems like the segment where the TTBW would make the most sense would be as a potential design for a C130 replacement, where payload could now be maximized through that ultra high-lift, ultra light-weight wing, the high-wing design meshes perfectly with the aircraft's role while allowing it to use a pair of GTF's or UDF's to give it true jet speeds, and even the folding wingtips would be much less scary to the military maintenance depts.

a reply to: Barnalby

You're obsessed with fitting this into the 737/regional markets without any kind of data that it's going into that area. Just as you're obsessed with form over function.

a reply to: Zaphod58

I was just interpolating that it would be a 737-class aircraft because all of the studies have been for 737-class aircraft (and the 787 and 777MAX are so new that the 737 airframe is currently at the raggedest edge of what the technology can squeeze out of it in terms of extra performance.

Part of me thinks that MOM will end up replacing the larger 737 variants, and that sizewise the true 737 replacement will be a smaller aircraft that can bridge the gap between the E175 and the current 737.

And I'm not ANTI-TTBW, per se, but I DO tend to get pretty skeptical when I see radical new wing designs and planforms for airliners as they currently have a batting average of .000 in terms of making it to market these days. The failure of the BWB, the pi-tailed UDF airliners, wasp-waisted area-ruled airliners, and even the box wing to get any traction has left me a little gun-shy.

But I will say that I see there being a ton of room for innovation when it comes to fuselages and powertrains, and I could easily see the 737 replacement being an elliptical-fuselaged mini-widebody powered by hybrid engines. I'm just not entirely convinced that radical planform changes will ever really fly.

a reply to: Barnalby

The BWB was almost always going to be a cargo aircraft. It's hardly "failed" as they're still building demonstrators and planning a half scale separator in the next few years.

Why would they be planning to replace the 737 when the Max flew a few weeks ago for the first time? They're booked solid well into when we might see this fly. The Max will fill the gap between the 737 and 757 class and even have the range to fly some 757 routes.

I've seen some designs for some very low drag truss braced/semi cantilever aircraft that are very far from looking like a Cessna 152! In fact, I'd go as far as to say that they look very futuristic, and as an engineer I see the elegance in the form that makes it all the more attractive.

As for what the airlines think, they think cost v profit. It's the manufacturers marketing department's job to get the airlines on board and the airlines marketing guys to get the public on board. Lets face it, the 747 is one ugly monster on paper, but it was turned in an icon by clever marketing...anyone say "Jumbo".

I'd love MoM to be a semi cantilever, swept wing design.

Cheers
Robbie

a reply to: Zaphod58

I was just figuring that they were looking at the 737 class as it's the design family that's closest to the hard limit of what they can do to upgrade it due to the engine clearance issues.

The 777 still has many years left in it, and the 787 may well have many decades left if they choose to go the 737 route with it.

Though ironically, now that the 737MAX has replaced Y1 and the 777MAX has replaced the Y3, in a couple years time, the oldest/most outdated aircraft in Boeing's stable will be the 787!

So after making a fool of myself on the truss wing issue, I have a legitimate question. Why the high wing?

One of the reasons why the low wing has stayed so popular for jetliners is that it's a really elegant solution. For one, landing gear can be accommodated in the wing, which allows for a wider, more stable main gear arrangement while also eliminating the need for dedicated fairings (and the drag that they produce) in which to house the main gear.

In terms of weight, the main spar now does all the work, carrying the weight of the aircraft on the ground AND in the air, while also handling thrust/braking loads. Compare that to a high wing design where you now need a second spar to adequately spread the main gear and handle their rolling/braking forces when on the ground, while the wing has to handle all those same forces in the air.

Furthermore, the low wing design does wonders for cabin environment, effectively shielding the passenger area from the engines minimizing cabin noise. Compare that to a high-wing design, where there will be a night and day difference in cabin noise for passengers who are ahead vs behind of the engines, unless airlines are willing to pay a major weight/cabin width penalty due to acoustic insulation.

Finally, I'd imagine that there could be a maintenance/safety penalty to pay for the high-wing truss-braced design. Accidents happen, and jetliners are constantly bumping into stuff on the tarmac. With a low-wing design, the non-structural aerodynamic elements like leading edges, engine intakes, and control surfaces serve almost like crumple zones to keep all of the critical stuff (spars, engines, fuel tanks) protected when someone makes a whoops and drives a tug/baggage train/food truck/other airplane into a parked or moving airliner. Now, with this high-wing truss-braced design, the lowest hanging element is now critical structural element that is essentially unprotected to minimize drag. On a presumably composite design where repairing it, much less replacing it, will be a relative nightmare compared to doing the same on a Cessna, Skyvan, or Twin Otter. Right now, a baggage van driving into the wing means a lot of incident reports and a day or two worth of sheet metal repairs. On a high-mounted truss-braced wing, it could mean taking an aircraft out of service for a month or more while the truss spar is replaced.

With that all being the case, might it be more likely that we will instead see an upside-down truss-braced wing with significant dihedral, where the engines hang below the wing to shield them from passengers, the main gear are mounted to the wing spar, and the truss spars now reach upwards to mount to the top of the fuselage tube? I'd imagine that such a design would also save you the extra weight of that T-tail, since a conventional tail would now be extended into essentially clean air.

Airliners would now all look like giant Cessna 188s, but it seems like it would solve a bunch of potential design problems.

a reply to: Barnalby

The 757 family will be 25 years old when they finally come up with a replacement for it. They're not even going to start on it until after the 777X is being built it looks like. The designs that they're studying would be able to carry 325 people, up to 7500 nm.

The reason for the high wing, is weight and efficiency. A cantilever wing tends to be heavier than a high wing like this. With a high wing they can make it as light as possible, for better efficiency than they could a similar cantilever design. A cantilever wing has more structure and stress on it than this wing would, which means they couldn't make it near supercritical.

There are drawbacks to the design, yes, but overall it's much more efficient.

a reply to: Zaphod58

Which is where I was thinking you might get the best of both worlds with a low-mounted truss braced wing, like an ag plane has. The truss spar might have to be a little thicker because it would be acting in compression instead of tension, but I'd imagine some of that weight penalty would be more than made up for by the ability to use a conventional tail as well as the elimination of of the separate landing gear structure/fairings.

I'd imagine that the replacement of the top-mounted wing box with a smaller spar box would also do good things for cabin space and would avoid a large structure that might affect overhead bin space for a significant number of economy-section passengers, while allowing it to retain a more conventionally-sized cargo compartment. The operational changes compared to cantilever designs would also be minimized, I'd imagine.

That's why a lot of me thinks that this "100% aerodynamics" TTBW/SUGAR concept will take its place alongside the wasp-waisted T-tailed 757 concept, the UDF-engined MD-80s, the Sonic Cruiser, and the scimitar-tailed 7E7 as a sort of "concept plane" demonstrating what's possible that'll end up getting refined into a much more conservative design (that retains 75% of the efficiency gains of its no-holds-barred predecessor) once the change-shy airline boards as well as the even more conservative ILFC/ALC get their hands into the design process and start bringing their decidedly non-aerodynamic concerns into the design process.