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keesje
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Boeing 787 as starting point Large NMA / MoM, unlikely?

Sat Mar 18, 2017 8:35 pm

It seems Boeing is looking for a twin aisle MoM solution. Twin aisles are heavy/costly under say 250 seats, so Boeing probably is aiming higher.

If we look at what's in the market, 767, A330 fleets will be up for retirement and 787-8 and A330-8 have been selling poorly lately. Not surprising, these aircraft's weights and dimensions make clear they're long haul machines. Big wings, fuel tanks & landing gears.

Boeing tried for a quick solution with the 787-3, but everybody realized in time that wasn't a good idea. To make to an 787 attractive for short/ medium flights, expensive, radical weight & cost cutting would be required. A 787 MoM would need to fit smaller gates and provide razor sharp CASM at unique payload-ranges.

Advantages of using 787 technology would be lower development costs (e.g. fuselage, engines), fleet commonality and LD3 capability versus smaller aircraft types. Disadvantage could be airlines might find it large for a MoM, despite it being way lighter and cheaper to operate than existing 787 types.

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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sat Mar 18, 2017 8:48 pm

Lord how many MOM threads does there need to be? We should just have 1 Boeing and 1 Airbus thread.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sat Mar 18, 2017 8:58 pm

Yay... yet another MoM thread (not that I care too much the topic is really interesting). I think the MoM will happen, but I feel that all this speculation and argument over twin-aisle vs. single, fuselage shapes, and whether Boeing marketing or Leahy and physics are correct. I personally think we will see a 767-sized 787, with the reductions in engine thrust and some additions (folding wing tips, CFRP, etc.) Of course, they'll probably call it the 797, and I'm gonna guess they'll announce it at one of the major air shows later this year.

Personally, I'm hoping we get all the good stuff (aka 18-inch wide seats, folding wing tips, CFRP, etc), but that remains to be seen. I also agree with you that going too short will be inefficient and stubby (although I'd like to not get into that argument). Whatever happens, I think Boeing needs to make a plane that can be used as a base for future replacements.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sat Mar 18, 2017 9:06 pm

The 787 is structurally vastly overbuilt for this. Right down to skin thickness. Boeing has always been a very safety first builder and this first foray into composites is no different. If you have to re engineer substantially all of the structure why make it a family member? The gear, engines, wings, etc have to change anyway. That's why the 788 is so heavy relative to a modern a300 type competitor. And Boeing can't wait to stop making them in that size even at a higher price so I think what was learned from the 788 and 783 was just eventually implemented in the 789.

The 788 itself is basically a throw away model at this point for them. That's part of the reason they're working on this new model in any case.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sat Mar 18, 2017 9:19 pm

This is getting out of control. Why would this not be in the existing thread? Perhaps because it was started by someone else?

viewtopic.php?f=3&t=1357237
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sat Mar 18, 2017 9:25 pm

I think it is clear the 787-8 isn't selling anymore. Some say Boeing is avoiding sales of this sub type. Still there are many 767's up for replacement at e.g. DL, AA and UA. On top of that the A330 early fleet from the nineties starts aging.

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2000-4000NM flights from ATL

Matching the right capacity requirements might be key to success.

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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sat Mar 18, 2017 10:37 pm

texl1649 wrote:
The 787 is structurally vastly overbuilt for this. Right down to skin thickness. Boeing has always been a very safety first builder and this first foray into composites is no different. If you have to re engineer substantially all of the structure why make it a family member? The gear, engines, wings, etc have to change anyway. That's why the 788 is so heavy relative to a modern a300 type competitor. And Boeing can't wait to stop making them in that size even at a higher price so I think what was learned from the 788 and 783 was just eventually implemented in the 789.

The 788 itself is basically a throw away model at this point for them. That's part of the reason they're working on this new model in any case.


These variants would be 30t lighter and smaller (ICAO Cat D). Only fuselage cross section stays the same. A high capacity short/medium range aircaft. A carbon A300-600 / 767-300 like aircraft.

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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sat Mar 18, 2017 10:57 pm

Looks like you're still planning to cross oceans with that thing. What makes you think you can shave off 30+ tons from one of the most efficient wide-body aircraft available, by keeping it much the same as it is today and 'only' only lobbing 4 meters off the fuselage and fitting a new set of feathers?
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sat Mar 18, 2017 11:09 pm

keesje wrote:
Boeing tried for a quick solution with the 787-3, but everybody realized in time that wasn't a good idea.


And the reason it wasn't a good idea was the 52m wingspan, which your 787-4 has, as well.

Boeing pulled 10,000kg out of the OEW of the 787-3 by optimizing it for the short-haul mission through the shorter wings (worth ~4,000kg) and a thinner fuselage and lighter MLG (the other ~6000kg). Now you want them to knock another 20,000kg off on top of that? From where, exactly?
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sat Mar 18, 2017 11:22 pm

What about the economics of a single aisle double-decker? Think a two level 757, inspired by the A380? Could this be built as a vertical oval with space for LD3s?
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sat Mar 18, 2017 11:49 pm

I have never heard of a shrink that reduced OEW by 25 tons. That might as well be a new type design since basically everything will be redesigned.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 12:16 am

holzmann wrote:
What about the economics of a single aisle double-decker? Think a two level 757, inspired by the A380? Could this be built as a vertical oval with space for LD3s?



:banghead: Double jet ways? Longer boarding times? Where would you put 400 + bags alongside the belly freight? Aeroplanes make money in the sky, not on the ground. You'd basically be flying in an aeroplane in the shape of a chicken egg. Try again.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 12:37 am

The 787-8 is a long haul machine. This variant would not "shave off" 30t. It would have a new different wing, wingbox, engines and landing gear. It would have the same empty weight as the 1960s technology, slightly longer all metal A300-600. (which is 30t lighter than the longhaul A330-200).

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Last edited by keesje on Sun Mar 19, 2017 12:42 am, edited 1 time in total.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 12:39 am

keesje wrote:
texl1649 wrote:
The 787 is structurally vastly overbuilt for this. Right down to skin thickness. Boeing has always been a very safety first builder and this first foray into composites is no different. If you have to re engineer substantially all of the structure why make it a family member? The gear, engines, wings, etc have to change anyway. That's why the 788 is so heavy relative to a modern a300 type competitor. And Boeing can't wait to stop making them in that size even at a higher price so I think what was learned from the 788 and 783 was just eventually implemented in the 789.

The 788 itself is basically a throw away model at this point for them. That's part of the reason they're working on this new model in any case.


These variants would be 30t lighter and smaller (ICAO Cat D). Only fuselage cross section stays the same. A high capacity short/medium range aircaft. A carbon A300-600 / 767-300 like aircraft.

Image



Please articulate how Boeing could reduce 30 additional tons from the 787-8?
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 12:42 am

Despite the numerous but popular MoM threads, I want to thank keesje for introducing this topic. To be sure, Boeing will rely heavily on the 787 as it continues to refine the criteria for a new clean-sheet MoM aircraft. Whether the same fuselage of the 787 will be used for the MoM is debatable; nevertheless, the idea shouldn't be ruled out.

Perhaps the biggest issue facing Boeing with the MoM is weight. If it's too heavy, the anticipated fuel-saving consumption numbers will be hard to meet. As noted in other posts, the 787 is a long-haul aircraft that is too big and heavy to be workable as a MoM plane. The question becomes whether a revised version of the 787 can be made light enough despite its sizable girth. At this time, it appears Boeing has surmised that's it not doable, as the leaked concepts of the MoM all point to an aircraft with 7-abreast seating.

With 7 abreast seating, the MoM fuselage could be shrunk to roughly 16-17 feet, and that in itself should bring meaningful weight savings in the fuselage, wing box and landing gear. A smaller wing should produce even more weight savings. With the continuing shift toward more parts utilizing CFRP and ceramic technologies, the aircraft of the mid-21st Century will be significantly lighter than current aircraft produced today. What's still unknown with the MoM, however, is whether in the end, when all factors are taken into account—weight savings, new engine technology, etc.—there's a compelling claim for a new clean-sheet design. That's for the engineers and management to figure out. From what's being reported Boeing seems to believe a strong case for the project can be advanced. Of course, any final design of the MoM will rest heavily on cost/benefit analysis. Boeing may not be wanting to attempt another moon shot, but with a new clean-sheet MoM concept they be willing to push much further and harder than to simply devise a smaller-sized 787.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 12:55 am

The 787-8,-9 and -10 share the same center wingbox, wing, fuel capacity, engines and landing gear. Optimized for carrying a full 787-10 on 12 hour flighs. Flying the 787-9 on 8000NM flights.

Image

Remove that longhaul capability out of the 787 and design a new optimized set for the MTOW's given. It's a different machine. The 787-3 just cut off wingtips. That's not comparable. This 787-4 and 787-5 concepts would big MoM's, more on the right upper side of the spectrum.

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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 1:05 am

Well if the only thing you are really leveraging from the 787 is the fuselage diameter and (de-rated) engines, where are Boeing (and the airlines) saving the money, exactly? Designing and producing all these new parts will be expensive for Boeing, which means they'll be expensive for the airlines (in the Average Sales Price paid). And since they'll be unique to the MoM, the airlines aren't exactly going to see much in the way of spares and maintenance commonality with their 787 fleets. And I expect using 787 engines isn't going to be very optimal, even if de-rated., It would be like hanging de-rated A330 engines off an A300/A310 - they're larger and heavier than they need to be for the mission at hand.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 1:08 am

keesje wrote:
The 787-8,-9 and -10 share the same center wingbox, wing, fuel capacity, engines and landing gear. Optimized for carrying a full 787-10 on 12 hour flighs. Flying the 787-9 on 8000NM flights.


Remove that longhaul capability out of the 787 and design a new optimized set for the MTOW's given. It's a different machine. The 787-3 just cut off wingtips. That's not comparable.


What does "Remove the longhaul capability" mean exactly? I see a few obvious points:

1) Higher aspect ratio (make the wing skinnier)
2) Lower wingspan
3) Shorten fuselage
Possibly
4) Fuselage narrowing (this basically makes it a new model)

I don't know how much weight the above would shave off, but 30 tons is a lot.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 1:13 am

Whalejet wrote:
keesje wrote:
The 787-8,-9 and -10 share the same center wingbox, wing, fuel capacity, engines and landing gear. Optimized for carrying a full 787-10 on 12 hour flighs. Flying the 787-9 on 8000NM flights.


Remove that longhaul capability out of the 787 and design a new optimized set for the MTOW's given. It's a different machine. The 787-3 just cut off wingtips. That's not comparable.


What does "Remove the longhaul capability" mean exactly? I see a few obvious points:

1) Higher aspect ratio (make the wing skinnier)
2) Lower wingspan
3) Shorten fuselage
Possibly
4) Fuselage narrowing (this basically makes it a new model)

I don't know how much weight the above would shave off, but 30 tons is a lot.


I really don't understand Keesje's logic. In one thread he is saying this about the proposed 797 concept:

"In my opinion a 7-8 abreast aircraft with (operating) costs similar to a narrow-body are a fairy tale. Also if you shrink it."

Now he is saying that a 787-5 is possible with a 26t OEW reduction and a 787-4 can have a 32t OEW reduction.

So what is the fairy tale? An all new MOM competing with the A321 or a 26ton weight reduction to the existing 787. I don't understand how the premise of this thread is not a fairy tale.
Last edited by Newbiepilot on Sun Mar 19, 2017 1:27 am, edited 1 time in total.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 1:22 am

30 t may sound a lot. But it's difference between a long haul machine and a shorter short/ medium haul machine. Sharing the same fuselage, cockpit, tail but wings, wing boxes and landing gears for different missions.

Image

The empty weight difference between an A330-200 and A310-300 is even more, 41t.. or 34%.

If we are comparing this big 3-3-3 MoM concept to an oval 2-3-2 twin aisle concept with 250 seats single class 4000NM range, that's of course again a totally different beast. We should compare apples to apples, oranges to oranges. :yes:
Last edited by keesje on Sun Mar 19, 2017 1:30 am, edited 1 time in total.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 1:29 am

keesje wrote:
30 t may sound a lot. But it's difference between a long haul machine and a shorter short/ medium haul machine. Sharing the same fuselage, cockpit, tail but wings, wing boxes and landing gears for different missions.

Image

The empty weight difference between an A330-200 and A310-300 is even more, 41t.. or 34%.

If we are considering this big 3-3-3 MoM to an oval 2-3-2 twin aisle with 250 seats single class 4000NM range, that's of course again a totally different beast. We should compare apples to apples, oranges to oranges.


The A310 and A330 have different type certificates. This is not a stretch or shrink like you are suggesting.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 1:32 am

Newbiepilot wrote:
keesje wrote:
30 t may sound a lot. But it's difference between a long haul machine and a shorter short/ medium haul machine. Sharing the same fuselage, cockpit, tail but wings, wing boxes and landing gears for different missions.

Image

The empty weight difference between an A330-200 and A310-300 is even more, 41t.. or 34%.

If we are considering this big 3-3-3 MoM to an oval 2-3-2 twin aisle with 250 seats single class 4000NM range, that's of course again a totally different beast. We should compare apples to apples, oranges to oranges.


The A310 and A330 have different type certificates. This is not a stretch or shrink like you are suggesting.


No Newbiepilot, I'm not suggesting a stretch or shrink. Please re-read the OP, thnx.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 1:37 am

keesje wrote:
Image


This chart illustrates perfectly why the A330-900 and the 787-9 have been so successful. Both found the sweet spot. For the A330-900, it's a seating capacity of 300 and a range of 6000nm. And, similarly, for the 787-9, it's a seating capacity of 280 and a range of 7500nm.

The sweet spot for the MoM appears to be an aircraft with a seating capacity of 220 to 280 with a range from 4000 to 6000nm. The keys will be fuel consumption, durability, and efficiency.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 1:38 am

keesje wrote:
Newbiepilot wrote:
keesje wrote:
30 t may sound a lot. But it's difference between a long haul machine and a shorter short/ medium haul machine. Sharing the same fuselage, cockpit, tail but wings, wing boxes and landing gears for different missions.

Image

The empty weight difference between an A330-200 and A310-300 is even more, 41t.. or 34%.

If we are considering this big 3-3-3 MoM to an oval 2-3-2 twin aisle with 250 seats single class 4000NM range, that's of course again a totally different beast. We should compare apples to apples, oranges to oranges.


The A310 and A330 have different type certificates. This is not a stretch or shrink like you are suggesting.


No Newbiepilot, I'm not suggesting a stretch or shrink. Please re-read the OP, thnx.


I read everyone of your posts. What you are doing to a 787 would be a new type certificate with pretty much new everything kind of like the differences between the A310 and A330. You pretty much are calling the MOM a 787-4/787-5. I don't understand what you are getting at.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 1:52 am

Newbiepilot wrote:
keesje wrote:
Newbiepilot wrote:

The A310 and A330 have different type certificates. This is not a stretch or shrink like you are suggesting.


No Newbiepilot, I'm not suggesting a stretch or shrink. Please re-read the OP, thnx.


I read everyone of your posts. What you are doing to a 787 would be a new type certificate with pretty much new everything kind of like the differences between the A310 and A330.


Exactly. Like the 777-8 is not a 77W shrink, the 737-9 isn't a 737-200 stretch. Or the A330 a A300 stretch.
But they still did it, with a ton of grandfathering, the same production lines and lots of commonality.

This upper sized MoM could in higher density configuration move over 300 people between large cities. E.g. Amsterdam London, 70 flights a day and fit the smaller gates, pay less airport taxes and burn less fuel because it's flying around 30t less structure (~ similar to the payload!) Other use could be found e.g. US Eastcoast, domestic China and the Leisure carriers that use high density, even 8 abreast 767-300ER's and 9 abreast A310s, to the Caribbean and Mediterranee.

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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 2:02 am

Newbiepilot wrote:
I read everyone of your posts. What you are doing to a 787 would be a new type certificate with pretty much new everything kind of like the differences between the A310 and A330. You pretty much are calling the MOM a 787-4/787-5. I don't understand what you are getting at.

What keesje seems to be saying is Boeing might be looking to develop a larger MoM aircraft because the benefits of a twin aisle that only seats 250 are questionable. If one agrees with this premise, a MoM aircraft with 2-3-2 seating loses it edge in favor of 2-4-2, which brings the fuselage size up to the 787. If that's the case, then why not use the fuselage of the 787 as a basis for the MoM.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 3:16 am

PlanesNTrains wrote:
This is getting out of control. Why would this not be in the existing thread? Perhaps because it was started by someone else?


Which existing thread? I get that the OP is obsessed with "MOM" and how dumb Boeing is or whatever, but do we really need a new thread on "MOM" every few days? It would declutter the board a lot if any of the many existing threads could be used.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 8:01 am

ITB wrote:
Newbiepilot wrote:
I read everyone of your posts. What you are doing to a 787 would be a new type certificate with pretty much new everything kind of like the differences between the A310 and A330. You pretty much are calling the MOM a 787-4/787-5. I don't understand what you are getting at.

What keesje seems to be saying is Boeing might be looking to develop a larger MoM aircraft because the benefits of a twin aisle that only seats 250 are questionable. If one agrees with this premise, a MoM aircraft with 2-3-2 seating loses it edge in favor of 2-4-2, which brings the fuselage size up to the 787. If that's the case, then why not use the fuselage of the 787 as a basis for the MoM.


In other words, MoM doesn't look so much like a B757 replacement as it is an uber-efficient B767-200ER replacement.

Correct?
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 9:21 am

keesje wrote:
I think it is clear the 787-8 isn't selling anymore. Some say Boeing is avoiding sales of this sub type.


Boeing can either backport the 789 improvements to the 788 ( incurring similar cost delta that already went into the Mk2/789 design
( as you say they don't want to go there)
or they can go full hog and create a new subtype that fixes all shortcomings and also moves a bit down in range
and thus overall structure to at least get a grip on the A332/8 competitor.
This would require real demand _and_ efficient fullfilment of "cheaper to operate" than the competitor.
( But note the 767-300ER was much lighter and shorter ranged than the A332 but per seat less efficient ( ~6% less fuel for 12% less capacity. Large wings have a quality all on their own) .

But what could happen is that a slightly more efficient airframe just sits a bit higher on the onwards moving wave of "more range, more capacity" demand for twin aisles. ( What can be seen in the NB arena. C-Series does not open a new market segment but can live for a while where the heavier frames looked less than optimal.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 9:39 am

It's probably less technically challenging to design a light weight "MoM" aircraft from scratch than to shave off massive amounts of weight off an already heavy long haul airplane like the 787. But of course, there are upsides to using the 787 as a starting point too, like commonality and maybe shared production lines. The 787-9 only shares about 40% commonality with the 787-8 if I remember correctly. Maybe a "787-4" would have the same amount of commonality.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 11:14 am

I think there might be a big segment currently served by long haul platforms, because of capacity- slot considerations.

Image
2000-3000NM flights from Emirates.

https://www.oag.com/pressroom/a350-dreamliner
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 11:25 am

Ok, maybe a couple of barrels and some flight systems will be used from 787 (I doubt the barrels especially), but keep in mind Boeing really wants nothing to do with the Washington based industrial (labor) agreements and tax packages on this (they will want new ones), and that they won't want to be forced/required to use the same suppliers either (part of taking the cost out will be doing more on this themselves. It's not just a "will this cross section work, and can we lighten this frame" decision, but how to make this thing for 50 million in cost before engines per frame?

Finally, what airline would really be buying these frames or finalizing such a decision on the basis of commonality with their 787 fleet? Not many. This will dovetail, eventually, into their narrow body fleets, not long range international ops. The NSA commonality is hoped to benefit from this thing in their fleets but that's long term.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 12:57 pm

texl1649 wrote:
Ok, maybe a couple of barrels and some flight systems will be used from 787 (I doubt the barrels especially), but keep in mind Boeing really wants nothing to do with the Washington based industrial (labor) agreements and tax packages on this (they will want new ones), and that they won't want to be forced/required to use the same suppliers either (part of taking the cost out will be doing more on this themselves. It's not just a "will this cross section work, and can we lighten this frame" decision, but how to make this thing for 50 million in cost before engines per frame?

Finally, what airline would really be buying these frames or finalizing such a decision on the basis of commonality with their 787 fleet? Not many. This will dovetail, eventually, into their narrow body fleets, not long range international ops. The NSA commonality is hoped to benefit from this thing in their fleets but that's long term.


I think we should realize the amount of out of pocket money spend on fuel, airport taxes, extra frequencies WB doc because of operating 2000-3000NM flights with 77W's, 787s and A330s because they are the only ones offering 300+ seat capacity. Add the costs of extra flights around the same rush hours with NB's.

Key selling point that such a light, high capacity machine would have are the easily 30t / 66,000 lbs (!) lighter weight (fuel, airporttax, MRO) than a A330 or 787, offering the same payload. Also fitting smaller gates can not be ignored. A significant cost reduction.

https://thepointsguy.com/2016/10/american-airlines-787-9-business-flight-review/
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 1:45 pm

keesje wrote:
Also fitting smaller gates can not be ignored.


I really do not get this.

Aircraft are so much more expensive than a shovel of concrete and some rebar to upgrade airport infrastructure.

Is it because infrastructure is not "market" enough to profit from?
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RayChuang
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 2:05 pm

I think it's more likely we'll see a "clean sheet" design than a shorter, lower MTOW 787 derivative. You still have to deal with the wing box weight of 787, substantial part of the weight of the plane. A "clean sheet" MoM design would have a much lighter wing box and be optimized for 4,500 to 5,500 nm range, or could be optimized for high-freqency, high-density operations like SYD-MEL, SDU-GRU, HKG-TPE, and so on.
 
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seahawk
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 2:26 pm

If you lighten the CFRP barrel, you change everything apart from the manufacturing technology, so 7M7 will not be a version of the 787, while it surely will use some technology. Although I think cold cured composites might play a big part in the design of the 7M7.
 
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keesje
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 2:28 pm

RayChuang wrote:
I think it's more likely we'll see a "clean sheet" design than a shorter, lower MTOW 787 derivative. You still have to deal with the wing box weight of 787, substantial part of the weight of the plane. A "clean sheet" MoM design would have a much lighter wing box and be optimized for 4,500 to 5,500 nm range, or could be optimized for high-freqency, high-density operations like SYD-MEL, SDU-GRU, HKG-TPE, and so on.


RayChuang, the wingbox is indeed one of the heavier long haul specific sub assemblies. I assumed a new, lighter, lower fuel capacity wingbox. The range you mention is exactly the one mentioned. Going further would compromise the low weight design and is covered by larger twin aisles.

WIederling wrote:
keesje wrote:
Also fitting smaller gates can not be ignored.


I really do not get this.

Aircraft are so much more expensive than a shovel of concrete and some rebar to upgrade airport infrastructure.

Is it because infrastructure is not "market" enough to profit from?


Some major airports are designed around ICAO category aircraft. That's why Boeing is spending so much on the 777X wingtips. Flying to smaller airport with a limited numbers of code E gates becomes more feasible.

Image
ATL ICAO D gates


If you lighten the CFRP barrel, you change everything apart from the manufacturing technology, so 7M7 will not be a version of the 787, while it surely will use some technology. Although I think cold cured composites might play a big part in the design of the 7M7.


Somebody told me the fuselage is a limitted part of total aircraft MTOW.. say 15%.
So saving 20% there is valuable, but not very valuable.

Image
http://adg.stanford.edu/aa241/structures/weights.html
"Never mistake motion for action." Ernest Hemingway
 
WIederling
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 4:21 pm

keesje wrote:
Somebody told me the fuselage is a limitted part of total aircraft MTOW.. say 15%.
So saving 20% there is valuable, but not very valuable.


The fuselage is the central item on an aircraft ( even if its weight overall is only a fraction.)
One other element is tankage both together influence all other dimensions.
( and there appears to be some synergy between fuselage size and tankage size.
invariably it seems to make much sense to actually use available wing volume fully for fuel.)

airport "raster": how long are airport buildings useable without needing major redesign/rebuild?
It is not like aircraft growing happens over night and rather unexpected.
Murphy is an optimist
 
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keesje
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 4:44 pm

WIederling wrote:
keesje wrote:
Somebody told me the fuselage is a limitted part of total aircraft MTOW.. say 15%.
So saving 20% there is valuable, but not very valuable.


The fuselage is the central item on an aircraft ( even if its weight overall is only a fraction.)
One other element is tankage both together influence all other dimensions.
( and there appears to be some synergy between fuselage size and tankage size.
invariably it seems to make much sense to actually use available wing volume fully for fuel.)

airport "raster": how long are airport buildings useable without needing major redesign/rebuild?
It is not like aircraft growing happens over night and rather unexpected.


The reason the wing could shrink is because a significant lower tankage capacity is required compared to the 787-8,-9,-10. Lowering OEW (the above graph gives wing weight as part of empty weight, not MTOW) and needing less range/fuel triggles down all over the wing structure, LDG and tail weight. And engines.

The new advanced CRFP wing would be optimized for short/medium payload range. Without build in growth, because that already exists.

Image
"Never mistake motion for action." Ernest Hemingway
 
DfwRevolution
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 5:15 pm

keesje wrote:
The reason the wing could shrink is because a significant lower tankage capacity is required compared to the 787-8,-9,-10. Lowering OEW (the above graph gives wing weight as part of empty weight, not MTOW) and needing less range/fuel triggles down all over the wing structure, LDG and tail weight. And engines.

The new advanced CRFP wing would be optimized for short/medium payload range.


I would submit that reducing cruise Mach would better enable a 787 platform to compete as a MOM. Reducing cruise Mach to 0.80 would allow a reduction of wing sweep and allow a more structurally efficient wing. It would also reduce cruise drag by roughly 12%, equivalent to reducing fuselage diameter by about 13 inches.
 
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keesje
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 7:43 pm

DfwRevolution wrote:
keesje wrote:
The reason the wing could shrink is because a significant lower tankage capacity is required compared to the 787-8,-9,-10. Lowering OEW (the above graph gives wing weight as part of empty weight, not MTOW) and needing less range/fuel triggles down all over the wing structure, LDG and tail weight. And engines.

The new advanced CRFP wing would be optimized for short/medium payload range.


I would submit that reducing cruise Mach would better enable a 787 platform to compete as a MOM. Reducing cruise Mach to 0.80 would allow a reduction of wing sweep and allow a more structurally efficient wing. It would also reduce cruise drag by roughly 12%, equivalent to reducing fuselage diameter by about 13 inches.


For short flights a lower cruise speed could be a good option. On medium 2000-3000NM flights it could become a burden. If the wing has morphing / load elevation / adjustable wingtips, maybe the wing could dynamically be optimized for different speeds, so it would be up to the crew/operator to decide on the speed-efficiency compromise.
"Never mistake motion for action." Ernest Hemingway
 
texl1649
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 8:26 pm

Boeing has historically preferred the fastest speed they could build into a family (or notional family such as 2707 or sonic cruiser.)

Again, once carbon wing production and carbon fuselage construction (regardless of panels, 787, or cold set) are mastered, there's no marriage to a given frame cross section a la 707 or A300. I really think that's what we are about to see.
 
DfwRevolution
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 8:55 pm

keesje wrote:
For short flights a lower cruise speed could be a good option. On medium 2000-3000NM flights it could become a burden. If the wing has morphing / load elevation / adjustable wingtips, maybe the wing could dynamically be optimized for different speeds, so it would be up to the crew/operator to decide on the speed-efficiency compromise.


Will it be a burden for the A321neo to cruise at Mach 0.78 on 2,000-3,000 nm flights? :stirthepot:

If were talking about the MOM as something of a 767 replacement, it has apparently been no major penalty for 767 operators to cruise at Mach 0.80 to this day.

keesje wrote:
If the wing has morphing / load elevation / adjustable wingtips, maybe the wing could dynamically be optimized for different speeds, so it would be up to the crew/operator to decide on the speed-efficiency compromise.


If the point of an MOM is to shed weight and better optimize for short/medium-haul flying, then why add the weight for variable geometry features to broaden the performance envelope? I find that schizophrenic.

texl1649 wrote:
Boeing has historically preferred the fastest speed they could build into a family (or notional family such as 2707 or sonic cruiser.)


I don't think that is supported by history. The early Boeing jets like the 707 and 727 were both fast Mach 0.85 cruisers. The later generation of 757 and 767 jets slowed down to Mach 0.80. Boeing crept back up to Mach 0.84 with the 777 and now is returned to 0.85 with the 787. The conclusion I would draw is that Boeing selects the cruise Mach given the technology and mission needs at the time a product is launched.

I think a further reality is that Boeing has neither the time nor the money to spend on a clean-sheet type. The relatively soft and unfocused demand for an MOM type over the last 20 years combine with other development priorities should steer Boeing away from a moonshot. The MOM needs to re-use existing in-production hardware, suppliers, and processes.

Airlines clearly see the 787 as the product line of the future, so Boeing should start there. I starting with the 787-8 and then applying a minor shrink, weight reduction program, updated wing design, and revised engine option is actually one of Keesje better paper airplane hypotheticals.
 
Natflyer
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 8:56 pm

What Boeing is pitching to potential "MOM" customers these days is NOT a variation of the 787. Nuff said.
 
flipdewaf
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Mar 19, 2017 9:08 pm

keesje wrote:
Somebody told me the fuselage is a limitted part of total aircraft MTOW.. say 15%.
So saving 20% there is valuable, but not very valuable

I'd say that if you could save 20% of fuselage weight then you are well of the way to bog weight savings. The fuselage and useful payload is what the rest of the aircraft has to deal with moving and lifting into the air. If the fuselage + payload is 10% lighter then I'd wager the rest of the aircraft would/could be 10% lighter also. I'd say very valuable.

Fred
Image
 
WIederling
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Mar 20, 2017 7:49 am

DfwRevolution wrote:
I don't think that is supported by history. The early Boeing jets like the 707 and 727 were both fast Mach 0.85 cruisers. The later generation of 757 and 767 jets slowed down to Mach 0.80. Boeing crept back up to Mach 0.84 with the 777 and now is returned to 0.85 with the 787. The conclusion I would draw is that Boeing selects the cruise Mach given the technology and mission needs at the time a product is launched.


767 saw the very first steps into supercritical wing profile design by Boeing. Quality of implementation limited cruise Mach.
Murphy is an optimist
 
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keesje
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Mar 20, 2017 11:23 am

WIederling wrote:
DfwRevolution wrote:
I don't think that is supported by history. The early Boeing jets like the 707 and 727 were both fast Mach 0.85 cruisers. The later generation of 757 and 767 jets slowed down to Mach 0.80. Boeing crept back up to Mach 0.84 with the 777 and now is returned to 0.85 with the 787. The conclusion I would draw is that Boeing selects the cruise Mach given the technology and mission needs at the time a product is launched.


767 saw the very first steps into supercritical wing profile design by Boeing. Quality of implementation limited cruise Mach.


Designing an aircraft is an endless process of interactions and compromises. From what I've heard and seen over the last decade, significant improvements should be possible for EIS after 2020 in the list I summed a few posts ago and e.g. laminar flow technology. The most important consideration would be that all is optimized for an entirely different set of requirements than the current 787 wing. Todays fly-by-wire enables the aircraft to optimize everything using all control surfaces. In the past controls like flaps and ailerons had their own settings and control logic. Now control surface can simultaneous be active in lift -drag optimization, load elevation, cg trimming, noise reduction and pilot control inputs.
"Never mistake motion for action." Ernest Hemingway
 
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KarelXWB
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Mar 20, 2017 11:48 am

The 787 tube is way too heavy, though I could see some technologies ending up in the MOM airplane.
Close, but no cigar http://vine.co/v/OjqeYWWpVWK
 
dare100em
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Mar 20, 2017 11:53 am

DfwRevolution wrote:
keesje wrote:
For short flights a lower cruise speed could be a good option. On medium 2000-3000NM flights it could become a burden. If the wing has morphing / load elevation / adjustable wingtips, maybe the wing could dynamically be optimized for different speeds, so it would be up to the crew/operator to decide on the speed-efficiency compromise.


Will it be a burden for the A321neo to cruise at Mach 0.78 on 2,000-3,000 nm flights? :stirthepot:

If were talking about the MOM as something of a 767 replacement, it has apparently been no major penalty for 767 operators to cruise at Mach 0.80 to this day.

keesje wrote:
If the wing has morphing / load elevation / adjustable wingtips, maybe the wing could dynamically be optimized for different speeds, so it would be up to the crew/operator to decide on the speed-efficiency compromise.


If the point of an MOM is to shed weight and better optimize for short/medium-haul flying, then why add the weight for variable geometry features to broaden the performance envelope? I find that schizophrenic.

texl1649 wrote:
Boeing has historically preferred the fastest speed they could build into a family (or notional family such as 2707 or sonic cruiser.)


I don't think that is supported by history. The early Boeing jets like the 707 and 727 were both fast Mach 0.85 cruisers. The later generation of 757 and 767 jets slowed down to Mach 0.80. Boeing crept back up to Mach 0.84 with the 777 and now is returned to 0.85 with the 787. The conclusion I would draw is that Boeing selects the cruise Mach given the technology and mission needs at the time a product is launched.


:checkmark: Reducing to about mach 0.8 could make sense for a MOM.

DfwRevolution wrote:
keesje wrote:
For short flights a lower cruise speed could be a good option. On medium 2000-3000NM flights it could become a burden. If the wing has morphing / load elevation / adjustable wingtips, maybe the wing could dynamically be optimized for different speeds, so it would be up to the crew/operator to decide on the speed-efficiency compromise.

I think a further reality is that Boeing has neither the time nor the money to spend on a clean-sheet type. The relatively soft and unfocused demand for an MOM type over the last 20 years combine with other development priorities should steer Boeing away from a moonshot. The MOM needs to re-use existing in-production hardware, suppliers, and processes.

Airlines clearly see the 787 as the product line of the future, so Boeing should start there. I starting with the 787-8 and then applying a minor shrink, weight reduction program, updated wing design, and revised engine option is actually one of Keesje better paper airplane hypotheticals.


The problem is that with all twist necessary for a 787-based MOM the program would essentially be at least 80% of a clean sheet. You would have to touch even the wingbox to get the desired reductions. But at the end, you will still have a compromissed design but consumed 80% of the money and 90% of the time for a clean sheet.

The main drawbacks would be the to big fuse because the MOM would'nt need 9-abreast and crewrests overhead - so an vertical oval - and LD3's. A sardine 8-abreast MOM could have significant less frontal area, at least 20%, propably more, to a 787. Furthermore by using the 787-fuse the plane will get really really short compared to the fuse diameter, so the fitness ration would not be ideal too. And the fuse itself has to be overworked because the structural stiffness a 787-10 needs - resulting in wall thickness etc. - would add weight and costs to the MOM.

All this to safe like 20% to a clean sheet :confused: . No, won't happen. :white:
 
WIederling
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Mar 20, 2017 11:54 am

KarelXWB wrote:
The 787 tube is way too heavy, though I could see some technologies ending up in the MOM airplane.


Are there actually some real "per meter length" weight numbers around for 787 barrels?
( 788 to 789 delta due to changes in structure doesn't provide anything useful.)
Murphy is an optimist

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