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

Mon Mar 20, 2017 4:03 pm

As showed up, barrel is about 15% weight of the aircraft empty weight and much less of the MTOW (8%?). http://www.airliners.net/forum/viewtopic.php?p=19422439#p19420899

So cutting back 20% weight on the fuselage would gain 0.2 * 0.08 = 1.6% of MTOW. It seems a lot of investment for a ~1-2% weight gain. Low priority it seems.

But we can agree that the 787 is a large cross section. The seating at 9 abreast is dense for 787 medium range flights.

A good part of a 787 cross section is taken by the LD3 capable cargo deck. That cargo deck would be a waste of space if you don't use it. So maybe you should. Lowerdeck lavatories, galley capacity seem a low risk option. They would further improve revenue cabin space and lower CASM. Still some usefull cargo opportunity would be left, contrary to e.g. A321LR and the MoM 2-3-2 idea.

If it fits an A340, it should fit a bigger 787 lower deck. This not possible on a A321 or 2-3-2 MoM, where is eats mean deck seat space.

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

Mon Mar 20, 2017 4:24 pm

keesje wrote:
As showed up, barrel is about 15% weight of the aircraft empty weight and much less of the MTOW (8%?). http://www.airliners.net/forum/viewtopic.php?p=19422439#p19420899

So cutting back 20% weight on the fuselage would gain 0.2 * 0.08 = 1.6% of MTOW. It seems a lot of investment for a ~1-2% weight gain. Low priority it seems.



But a 20% reduction in fuselage weight (lets call it 10% of fuselage and payload) means a reduction in wing area (and therefore weight) and so a reduction of thrust (and weight from smaller engine) and a reduction in tail size (less thrust means less tail size required). Weight reductions are not to be sniffed at at the development stage, they are hard to do later but early are very valuable.

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

Mon Mar 20, 2017 5:28 pm

Fred, I think wing area is determined by MTOW, performance/ wingloading requirements and required fuel capacity. I doubt a 1-2% reduction in MTOW would justify the significant investment and de-standarization of the 787 fuselage supply chain.
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flipdewaf
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Mar 20, 2017 7:09 pm

keesje wrote:
Fred, I think wing area is determined by MTOW, performance/ wingloading requirements and required fuel capacity. I doubt a 1-2% reduction in MTOW would justify the significant investment and de-standarization of the 787 fuselage supply chain.

So you are saying they will design the aircraft around a performance criteria to move a certain amount of dead weight (fuselage+payload) over a range from a given runway then remove some of the dead weight. Why wouldn't they remove the dead weight and do the calculations based on that to get the optimised wing for the reduced weight?

If you save 20% from the fuselage and therefore 10% of the dead weight (for arguments sake) then you have good grounds to cut the wing weight by 10% by virtue of needing less area because less lift required, the engine weight by 10% because there is less drag so less powerful engines are needed the list goes on...

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

Mon Mar 20, 2017 8:27 pm

This all depends on how large the MOM should be. If we think 787-8 size and maybe a slightly shrunk variant, there isn't really any excess fuselage structure. The reduced weight will all be centered around the main landing gear.

Reduced wingspan (less structure and smaller fuel tanks), lighter engines (since less trust is required), wing box (reduced structure and smaller center fuel tank). All this equals reduced weight and therefore we can save some more by slimming down the main landing gear.

With the same number of seats and same cargo load as the 787-8, this could be a very efficient medium hauler/ MOM, a true 767-300ER replacement.

I think this is why Airbus is moving the A330neo into longer and longer haul. Recently the rumor is that Airbus is looking at 251t MTOW. The A330 would face difficult competing with a medium haul optimized 787-8, a 787-3 done right.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Mar 20, 2017 9:53 pm

flipdewaf wrote:
keesje wrote:
Fred, I think wing area is determined by MTOW, performance/ wingloading requirements and required fuel capacity. I doubt a 1-2% reduction in MTOW would justify the significant investment and de-standarization of the 787 fuselage supply chain.

So you are saying they will design the aircraft around a performance criteria to move a certain amount of dead weight (fuselage+payload) over a range from a given runway then remove some of the dead weight. Why wouldn't they remove the dead weight and do the calculations based on that to get the optimised wing for the reduced weight?

If you save 20% from the fuselage and therefore 10% of the dead weight (for arguments sake) then you have good grounds to cut the wing weight by 10% by virtue of needing less area because less lift required, the engine weight by 10% because there is less drag so less powerful engines are needed the list goes on...

Fred


Hi Fred, in a previous responds I referred to this source below, indicating the fuselage represents about 15% of an aircraft empty weight. If you optimize the fuselage efficiency /weight by about 20%, the nett effect of this modification on empty weight and MTOW becomes low, a few percent. Probably not closing the business case for the investment.

Image

E.g. if an aircraft has a MTOW of 100t and an OEW of 50t, the fuselage (15%of that) will weigh about 50t*0.15= 7.5t. Improve that by 20% and the fuselage becomes 6t. So you shaved 1.5t of a 100t aircraft.

You should pursue that, if its low hanging fruit, not if it's party-crasher production wise.
Last edited by keesje on Mon Mar 20, 2017 10:00 pm, edited 1 time in total.
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flipdewaf
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Mar 20, 2017 9:58 pm

Yes but when you scale the fuselage down by 20% then nudging by that chart it is still 15% of the weight so everything else drops 20% as well.
I agree that if the scope of such an exercise was limited to fuselage then this becomes less enticing but as this thread was about adding new wings engines and other systems to a previous fuselage then it would only seem right to add the cumulative gains that this could get you.

Fred
Last edited by flipdewaf on Mon Mar 20, 2017 10:03 pm, edited 1 time in total.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Mar 20, 2017 10:02 pm

flipdewaf wrote:
Yes but when you scale the fuselage down by 20% then nudging by that chart it is still 15% of the weight so everything else drops 20% as well.

Fred


I'm afraid not so. Systems, powerplants, LGD would drop around that 1.5%, because related to overall MTOW.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Mar 20, 2017 11:45 pm

I'm pretty convinced that the market for a 763 size aircraft (which MOM is turning out to be) is far too small to justify a 10 billion investment. A re-winged A322 NEO or MAX-11 would make the most sense. I think MOM as Boeing is envisioning would be a massive flop.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 1:59 am

A wonderfully speculative and fanciful thread. A fun 'What If?' but necessarily detached from reality. The notion that a relatively lightweight medium haul airliner would be derived from the long-range 787, somehow deriving savings out of commonality is entertaining but you must keep your mindset within the intended whimsy of this thread. At least it gave me the best chuckle I've had today. Thank you all for your contributions!
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 2:59 am

AvObserver wrote:
A wonderfully speculative and fanciful thread. A fun 'What If?' but necessarily detached from reality. The notion that a relatively lightweight medium haul airliner would be derived from the long-range 787, somehow deriving savings out of commonality is entertaining but you must keep your mindset within the intended whimsy of this thread. At least it gave me the best chuckle I've had today. Thank you all for your contributions!


I'm still trying to get my head around how we went from a souped up A321neoLR competitor to a nine-abreast widebody makeover? If the insulting picture of the photo-shopped 767 in the other thread was mocked, how do we get a nine-abreast medium haul airliner that now is not mocked? Or is this a setup? lol
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 3:58 am

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.



United, for one, likes what it is hearing from Boeing

https://www.bloomberg.com/news/articles ... at-it-sees
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 4:34 am

This premise of a lighter 787 may not be farfetched. First, if a 30t reduction can be had, the result is around 90t OEW. That's in the range of a 767. The original 766s had 40000 lb thrust engines. The LEAP and Pratt GTF are about 35000 lb now. If they can get those engines to 40000 lb, better wings may allow LEAP or GTF engines to be used. The Pratt 1100 (A320 series) is 6300 lb dry weight, while the GEnx is almost 13000 lb dry weight.

If Boeing can get the weight in the 90t range, and put in lighter, higher aspect ratio wings - they will probably not be shorter because the wings will need to support a lower takeoff speed - this just might work.

Wish I could have been a fly on the wall during those presentations to United.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 5:05 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.


Fact or speculation? If later experience allowed faster supercritical wings, then why did subsequent products with new wings like the A320, 737NG, and C-17 cruise in the Mach 0.74 - 0.78 region. Mission optimization clearly plays a role.

dare100em wrote:
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.

All this to safe like 20% to a clean sheet :confused: . No, won't happen. :white:


You say that as if an all-new product isn't itself a compromise of competing design priorities. A new-product is just less compromised.

Flip your premise around: what exactly are you going to gain by spending 25% more on an all-new product? What incremental sales will that investment net? Reducing the development budget by 20% is probably on the order of $2-3 billion dollars. That isn't pocket change to the investment community.

This site worships at the altar of OEW, but OEW is not such a clear-cut parameter.
I have a three post per topic limit. You're welcome to have the last word.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 6:23 am

If you do an all CFRP fuselage and redo everything else from wingbox over MLG to wings and engines, why would you not optimize the fuselage for the lower MTOW? You will need a new production line anyway and in the end it is just laying the carbon fibre matts less thick and at a different angle. The better question is if you can produce the large barrels of the 787 at a price that is suitable for the MoM, or if you are not better off looking at metals or a A350 style fuselage.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 7:07 am

seahawk wrote:
If you do an all CFRP fuselage and redo everything else from wingbox over MLG to wings and engines, why would you not optimize the fuselage for the lower MTOW? You will need a new production line anyway and in the end it is just laying the carbon fibre matts less thick and at a different angle. The better question is if you can produce the large barrels of the 787 at a price that is suitable for the MoM, or if you are not better off looking at metals or a A350 style fuselage.

:checkmark:

Exactly. The MOMs opportunity marked window has to include LCCs on medium range mission – e.g. Asia – WITHOUT hauling much cargo anyway. Cargo hauling is less and less important and fares are going down all the time. The 787 fuse is a big cargo hauler with it’s LD3 capability.
It is vertical oval for overhead crew rests – all a waste for the mission profile of a MOM. Yes, you could use some cargo space for toilets or catering, but that brings weight in it’s own (stairways) and didn’t help the A340 much.

The structure is to heavy build, including center wing box, a 787-based MOM would get very short, which has many negative implications in it’s own.
To start from a heavier base and ripe that base off weight is much, much more difficult than the other way around. One of the reasons is tha every single part of the millions defining a 787 are more-or-less designed for a big long haul twin. You have to screen through every single item and look if it could be downgraded. :banghead: At the end you may even have a MORE comlicated design than to start from scratch. Abaove a certain point on design changes on in the ballpark of the 77X it just doesen't make any sense to commit to a certain base.

It’s not gone be based on a 787-fuse – believe it or not, I’ll guess we’ll see soon enough.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 7:12 am

Is the A330/A340 based on the A300 fuselage or do they just share a diameter?
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 7:21 am

I would say the later.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 8:43 am

KD5MDK wrote:
Is the A330/A340 based on the A300 fuselage or do they just share a diameter?


Fuselage, nose, tail are the same. It's flying 9 abreast MoM like missions for more than 30 years!

Image

As said the empty weight difference between the A310 and A330-200 is an incredible 41t.

Image

Would Boeing JAL, ANA have stopped the 787-3 if it was 30t lighter and fully optimized for 2000-3000NM flights?

Seahawk, thinking about it, a similar sized fuselage fro short/medium haul might not be lighter than for long haul.

Because usually seat counts / cabin density is higher and so are flight cycles.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 9:01 am

And more landing cycles might mean I need to strengthen different areas compared to the long haul optimized version. So even if it the weight comes out close to each other, the CFRP layout will still be different.
Same as a A300 and a A330. Even if the fuselage looks similar, the structural elements are different, even if the stringer is only a tiny bit stronger at one corner, it is still a different and new designed part.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 10:45 am

Well we shouldn't overlook that long haul machines do less cycles, but loads on e.g. the tail would be higher (bigger wings, engines) and they might carry more containers / pallets too. So in the end they might be similar. I'm not sure if Boeing was changing the fuselage for the 787-3, I don't think so. As demonstrated even reducing 20% on the fuselage leads to a weight saving probably not justifying the investment on an aircraft level.

Another consideration might be the 787-8 is not OK Neither from a supplier nor a market perspective. So the MoM gap grew in the higher capacity direction. Airlines might be interested in a big MoM and pay more, if the performance & revenue potential justifies it. It's all about the money.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 10:58 am

The loads created by the tail are very different to the ones created by the landing gear. So even if it the end result weights the same, the strengthening is needed in different places.

And apart from that in the CFRP barrel construction of the 787, it is no big effort. You would do the load calculations anyway and the let the CFRP matt placement be optimized by the software.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 12:02 pm

WIederling wrote:
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.)


I don't know the "per meter length weight"; what I mean is the 787 is so much heavier than the 767/A321LR that you cannot just scale down the 787 and morphs it into a MOM aircraft.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 12:13 pm

I still don't understand why we are talking about a 250 seat MOM aircraft when looking at a 757 replacement.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 12:14 pm

Whalejet wrote:
I still don't understand why we are talking about a 250 seat MOM aircraft when looking at a 757 replacement.


Because we are looking at a 767 sized aircraft, not a 1:1 757 replacement.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 12:55 pm

seahawk wrote:
why would you not optimize the fuselage for the lower MTOW?


Fuselage weight is determined by structure requirements for the payload.
fuel for range and structure to carry both then dertermines MTOW.
Structure to carry payload and fuel feed back into fuel for range.
BUT
fuel in the wings alleviates loads from the payload.
i.e. more MTOW for just fuel comes cheap when your wings have enough available volume.
( best example A330.)
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 1:52 pm

keesje wrote:
KD5MDK wrote:
Is the A330/A340 based on the A300 fuselage or do they just share a diameter?


Fuselage, nose, tail are the same. It's flying 9 abreast MoM like missions for more than 30 years!

Image

As said the empty weight difference between the A310 and A330-200 is an incredible [b]41t.[/b]

Image

Would Boeing JAL, ANA have stopped the 787-3 if it was 30t lighter and fully optimized for 2000-3000NM flights?

Seahawk, thinking about it, a similar sized fuselage fro short/medium haul might not be lighter than for long haul.

Because usually seat counts / cabin density is higher and so are flight cycles.


Wow!! 41 Tons!! Great example. For sure, this new MOM will have more in common with the next 737 replacement than the 787 structural wise.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 3:40 pm

KarelXWB wrote:
WIederling wrote:
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.)


I don't know the "per meter length weight"; what I mean is the 787 is so much heavier than the 767/A321LR that you cannot just scale down the 787 and morphs it into a MOM aircraft.


No, and that's not what's proposed. Exchanging the center wingbox and wing and everything in/on, is a different approach. The A300, A310, A330, A343, A346 demonstrated there's a lot you can do with length, wings and engines. Same for the 737, DC9/MD80 e.g.

William
Wow!! 41 Tons!! Great example. For sure, this new MOM will have more in common with the next 737 replacement than the 787 structural wise.


I guess it's similar to the 777X, 737NG and A346. Wouldn't you agree?
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Mar 21, 2017 6:19 pm

KarelXWB wrote:
I don't know the "per meter length weight"; what I mean is the 787 is so much heavier than the 767/A321LR that you cannot just scale down the 787 and morphs it into a MOM aircraft.


Well, we do have OEW for A300B123, A310, A300-600 and we have OEW for the A330 types.
If we assume the longstanding OEW delta @4t for 5m

A300-600 is ~~4.5m shorter.
A310 is another ~~8m shorter.

In a first order estimation we should be able to derive weights for the different wing structures.
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keesje
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Wed Mar 22, 2017 9:31 am

WIederling wrote:
KarelXWB wrote:
I don't know the "per meter length weight"; what I mean is the 787 is so much heavier than the 767/A321LR that you cannot just scale down the 787 and morphs it into a MOM aircraft.


Well, we do have OEW for A300B123, A310, A300-600 and we have OEW for the A330 types.
If we assume the longstanding OEW delta @4t for 5m

A300-600 is ~~4.5m shorter.
A310 is another ~~8m shorter.

In a first order estimation we should be able to derive weights for the different wing structures.


I did it for various estimations, using "straight forward" stretches/shrinks. For A330/340 you can compare A340-200&-300, A330-200&-300, A340-500&-600. For 777 the -200LR & 300ER, 777-200 and -300. For 787, the 787-9 and -10. Haven't found 787-10 OEW though..

Estimations can be with certain limits, otherwise other specification choices (wings etc) come in.
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inferno
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Wed Mar 22, 2017 10:27 am

I still think a long narrowbody with a slightly wider aisle is still a better MoM aircraft than any short widebody.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Wed Mar 22, 2017 12:27 pm

keesje wrote:
No, and that's not what's proposed. Exchanging the center wingbox and wing and everything in/on, is a different approach. The A300, A310, A330, A343, A346 demonstrated there's a lot you can do with length, wings and engines. Same for the 737, DC9/MD80 e.g.


this may be a misunderstanding on my side.
But:
All the 737 models have the same wingbox basic dimensions.
Same for DC9..MD80 afaik.
for all gauge may obviously be different.

contrasting this:
The 4 basic Airbus types A300, A310, A330/340, A345/6 have decidedly different wingboxes. ( A310 _could_ have a similar dimension wingbox.))
What does not change is the X-section and design details like how the tail tapers and the rear floor lifts up slightly.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Apr 02, 2017 7:36 pm

WIederling wrote:
keesje wrote:
No, and that's not what's proposed. Exchanging the center wingbox and wing and everything in/on, is a different approach. The A300, A310, A330, A343, A346 demonstrated there's a lot you can do with length, wings and engines. Same for the 737, DC9/MD80 e.g.


this may be a misunderstanding on my side.
But:
All the 737 models have the same wingbox basic dimensions.
Same for DC9..MD80 afaik.
for all gauge may obviously be different.

contrasting this:
The 4 basic Airbus types A300, A310, A330/340, A345/6 have decidedly different wingboxes. ( A310 _could_ have a similar dimension wingbox.))
What does not change is the X-section and design details like how the tail tapers and the rear floor lifts up slightly.


I find it hard t believe DC9 and MD90 share the same wing box. https://upload.wikimedia.org/wikipedia/commons/3/3e/MD82v1.0.png

Coming back to the "787-3 Done Right" variants, I think competitions like the EK and Delta 787-A350 competitions would look entirely different if there was a real light and efficient 787 optimized for 1000-4000NM missions. Not sub optimized types like A330NEO, 787-9 and A359, which would look heavy & overspecified with their 30-35t higher OEW's.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Apr 02, 2017 8:37 pm

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?


The trouble with double-deckers, as Joe Sutter discovered, is that the lower deck has to support the weight of the upper deck and so you run into a real problem with sidewall thickness and structural weight. That's why the A380 has such thick sidewalls. The A380 makes up for that in CASM by sheer efficiencies of size, but that kind of advantage would fade away with a double-bubble narrowbody.

I think that a horizontal elliptical fuselage, which is possible with new materials, is the way to go.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Sun Apr 02, 2017 10:05 pm

DocLightning wrote:
I think that a horizontal elliptical fuselage, which is possible with new materials, is the way to go.


But the longitudinal bending moments would require inordinate amounts of stiffening.

Perhaps consider something with a cross section like the rotor of a Wankel engine, pointy side down.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Apr 03, 2017 1:30 pm

DocLightning wrote:
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?


The trouble with double-deckers, as Joe Sutter discovered, is that the lower deck has to support the weight of the upper deck and so you run into a real problem with sidewall thickness and structural weight. That's why the A380 has such thick sidewalls. The A380 makes up for that in CASM by sheer efficiencies of size, but that kind of advantage would fade away with a double-bubble narrowbody.

I think that a horizontal elliptical fuselage, which is possible with new materials, is the way to go.


Sorry, I think you get that the wrong way round... the thick sidewalls are the result of more bulky frames which are there to conduct the pressurisation loads from the skin into the floor beams, which are instrumental in holding the shape. The skin itself is actually the least stressed in that area - where the skin is critical is the top and bottom of the aircraft, because *that's* where it's "carrying" the front and rear of the aircraft on top of the wing.

But - and this is the crucial bit - the taller the A380 fuselage is, the *easier* it is for that skin to carry those loads (due to moment of inertia of the cross section). So a tall oval is structurally much better for carrying a long tube, and a tall oval is much better for holding its shape due to the floor beams.

The flat oval is the worst of both worlds.

Edit: Sutter's problem, as you call it, is that the *circular* fuselage above the wing was carrying the extra weight of the top deck near the nose... in other words, they added weight at the nose but no extra height in the mid-fuselage cross section to help carry it.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Apr 03, 2017 5:03 pm

keesje wrote:
I find it hard t believe DC9 and MD90 share the same wing box. https://upload.wikimedia.org/wikipedia/commons/3/3e/MD82v1.0.png

http://www.dept.aoe.vt.edu/~mason/Mason ... resS07.pdf
page 4: – The wing is based on the DC-9-34

not to be obnoxious here. :-)
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Apr 03, 2017 8:59 pm

WIederling wrote:
keesje wrote:
I find it hard t believe DC9 and MD90 share the same wing box. https://upload.wikimedia.org/wikipedia/commons/3/3e/MD82v1.0.png

http://www.dept.aoe.vt.edu/~mason/Mason ... resS07.pdf
page 4: – The wing is based on the DC-9-34

not to be obnoxious here. :-)

That's great but that's for the 717. You said that the MD-80/90 have the same basic dimensions as the DC-9 although I'm not sure exactly what you mean by that. If it's really basic dimensions such as overall volume, length, width, whatever you would be wrong. The MD-80/90 wing is based off of the DC-9, but it is quite different in that it was extended rootwise and also extended the other way as well. This effectively changed the some basic dimensions of the wing box makeing it different and then as a result much of the design common would have likely had to be modified as well.

You also mentioned the 737. The 737NG/MAX wing uses a different box altogether than the 737orig/classic.

The differences between the A330 and small A340 wings are small aside from structural things. They are almost the same wing. The difference between that design and the larger A340 wing is similar (not the same) to DC-9 vs MD-80 in that the larger one was based off of the smaller one but was modified to be larger making it different in basic dimensions.

Not saying a 787 shrink MOM is a good idea though, on the contrary I think it is a terrible idea.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Mon Apr 03, 2017 11:16 pm

inferno wrote:
I still think a long narrowbody with a slightly wider aisle is still a better MoM aircraft than any short widebody.


Completely agree.

Also, as an aviation aficionado, another twin aisle added to the glut of twin aisles, all with the same general configuration is about as bland and boring as it gets (unless they go for a radical design like the Kermit Cruiser). -Not at all an aircraft I'd be looking forward to seeing from the "aircraft watcher" perspective.
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Apr 04, 2017 7:00 am

767333ER wrote:
That's great but that's for the 717. .

The 717 is nothing more than a rebadged MD-95

A330 A340 are the exact same airframe hung with 2 or 4 engines.

A340NG i.e. A345, A346 have an enlarged wingbox : longer, higher.


The initial "questionable" statement was that the A330 is nothing more than a pimped A300.

Airframes that do not share the same dimension wingbox are not slightly pimped variations on a theme.
They are distinct.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Apr 04, 2017 2:37 pm

WIederling wrote:
767333ER wrote:
That's great but that's for the 717. .

The 717 is nothing more than a rebadged MD-95

A330 A340 are the exact same airframe hung with 2 or 4 engines.

A340NG i.e. A345, A346 have an enlarged wingbox : longer, higher.


The initial "questionable" statement was that the A330 is nothing more than a pimped A300.

Airframes that do not share the same dimension wingbox are not slightly pimped variations on a theme.
They are distinct.

Then by that logic the 737NG isn't just a pimped up 737 classic. The A330 most definetly started as a variant of the A300, but as things progressed and they changed the design more and more during the development stage it became its own plane based off of the A300 platform. You can give a plane a new wing and it's still the same thing, but once you make so many other changes it begins to become it's own thing. They are still similar and share many similar characteristics, but where they don't is that the A330 is better at just about everything than the A300 other than being a freighter.

And when someone talks about the MD-90 99.99999999999% they are not referring to the MD-95 as that is a defunct name. The OP referee to MD-80/90 vs DC-9.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Tue Apr 04, 2017 10:34 pm

WIederling wrote:
767333ER wrote:
That's great but that's for the 717. .

The 717 is nothing more than a rebadged MD-95

A330 A340 are the exact same airframe hung with 2 or 4 engines.

A340NG i.e. A345, A346 have an enlarged wingbox : longer, higher.


The initial "questionable" statement was that the A330 is nothing more than a pimped A300.

Airframes that do not share the same dimension wingbox are not slightly pimped variations on a theme.
They are distinct.


Thats what is proposed here, not a shrink 787, but a new wing box, wing, engines, landing gear, fuel capacity designed for doing shorter flights. Starting by being 30-35t lighter.
"Never mistake motion for action." Ernest Hemingway
 
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Wed Apr 05, 2017 12:08 am

keesje wrote:
WIederling wrote:
767333ER wrote:
That's great but that's for the 717. .

The 717 is nothing more than a rebadged MD-95

A330 A340 are the exact same airframe hung with 2 or 4 engines.

A340NG i.e. A345, A346 have an enlarged wingbox : longer, higher.


The initial "questionable" statement was that the A330 is nothing more than a pimped A300.

Airframes that do not share the same dimension wingbox are not slightly pimped variations on a theme.
They are distinct.


Thats what is proposed here, not a shrink 787, but a new wing box, wing, engines, landing gear, fuel capacity designed for doing shorter flights. Starting by being 30-35t lighter.

At the cost of doing that it would be a far better idea to use a more optimal cross section for the mission than the 787's which is suboptimal for the said mission.
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Wed Apr 05, 2017 7:38 am

767333ER wrote:
Then by that logic the 737NG isn't just a pimped up 737 classic.


The NG wing is nothing more than a reprofiled and extended Classic wing/wingbox.
( Think about why the certification tided over via massive grandfathering ( and why an A330 has its own distinct certfication.)
you are trying to mince airplanes here. :-)
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Re: Boeing 787 as starting point Large NMA / MoM, unlikely?

Thu May 11, 2017 2:36 pm

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?


No Holzmann, that seems a very unlikely scenario.

Boeing has better things to do right now then go after double decker 757 inspired by the A380.

Keep them coming.

:thumbsup:
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