RJMAZ
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 7:15 am

mjoelnir wrote:
You can put 440 passengers in a A330-900 and you can put 440 passengers in a 787-10, that are maximum numbers.

As pointed out they are theoretical maximum numbers and don't apply to the 1000+ aircraft in service. It is irrelevant and It only applies to a handful of aircraft.

Airbus could fit a dozen doors and make the exit limit 600 on the A330. You could fit 9ab with 26" pitch using slim seats and move all the toilets and food prep areas underneith. You would easily hit 500+ seats. So based on this the 777-9 is the direct competitor to the A330-900. All hail the almighty A330! :banghead:

As already pointed out many times by multiple users they aren't comparible. The 787-9 seats more seats than the A330-900 let alone the 787-10

Image
Both existing cabins with their business cabins replaced with economy seats.

So the 787-10 seats far more than the A330-900. If you fit the same amount of seats in both the 787-10 will be far more comfortable.
 
WIederling
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 7:21 am

rbavfan wrote:
Nice to see someone else using actual ACAP data, rather than just the usual well wikipedia says this comments.

WP usually reflects those ACAPS numbers too.
What lala numbers some people here reference is usually scraped from some lopsided article that fits their agenda.

caveat:
A332,A333 OEW numbers seem to have been changed to some unintuitive set that references the Type page on A.net :-)
Murphy is an optimist
 
WIederling
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 7:29 am

rbavfan wrote:
No they have the same exit limit for number of doors.

They are not approved for the same exit limits for seating in real operations. Boeing specs from: 787 Airplane Characteristics for Airport Planning are as follows. 787-8 limits 359 seats all-economy seats; FAA exit limit = 381 seats. 787-9 limits 406 seats all-economy seats; FAA exit limit = 420 seats.


There is no further limit than "exit limit".

What you pull from the ACAPS is a reference layout offered by the manufacturer.
there are other "limiting" metrics around: like number of FAs required : with the "last FA" on occasion
handling a handfull only introduces a cost vs revenue limit.
Murphy is an optimist
 
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keesje
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 8:51 am

Indeed Boeing has a majority of all civil aircraft in service.

They probably have an average 65% marketshare.

Over the last 40 years.

Image
"Never mistake motion for action." Ernest Hemingway
 
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Matt6461
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 1:44 pm

LH707330 wrote:
Matt6461 wrote:
There's no tech reason for the A330 to have significantly greater AR than 787.

Yeah there is: the A330/340 wing was deliberately designed with a high T/C ratio to get that aspect ratio, which involved sacrificing a few percent in cruise speed.


Good point.
Still, I wonder whether a .03M difference pencils out to ~15% AR penalty.
 
mjoelnir
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 3:28 pm

RJMAZ wrote:
mjoelnir wrote:
You can put 440 passengers in a A330-900 and you can put 440 passengers in a 787-10, that are maximum numbers.

As pointed out they are theoretical maximum numbers and don't apply to the 1000+ aircraft in service. It is irrelevant and It only applies to a handful of aircraft.

Airbus could fit a dozen doors and make the exit limit 600 on the A330. You could fit 9ab with 26" pitch using slim seats and move all the toilets and food prep areas underneith. You would easily hit 500+ seats. So based on this the 777-9 is the direct competitor to the A330-900. All hail the almighty A330! :banghead:

As already pointed out many times by multiple users they aren't comparible. The 787-9 seats more seats than the A330-900 let alone the 787-10

Image
Both existing cabins with their business cabins replaced with economy seats.

So the 787-10 seats far more than the A330-900. If you fit the same amount of seats in both the 787-10 will be far more comfortable.


The A330-300 is used with 440 pax. We are not talking about a dozen doors. I am talking about a setup used.

I was talking about LCC and ULCC not mainline. I was not talking about comfort levels. I was simply talking about the fact that if an ULCC uses the A330-900 with maximum pax, they will not be able to fit more pax in neither the 787-9, nor the 787-10.

Perhaps if you bang your head a little more you would not try to confuse facts.
 
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Momo1435
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 3:41 pm

Yes, Lion Air has put more seats in an A330 then any airline has done in the 787. But on the other side, Lion Air is now rumored to be close to placing a 787 order, at least that is what their CEO told the press a couple of weeks ago. So maybe we don't have to wait to long to be able to make an actual 1 on 1 comparison on the max seating of both models.
 
mjoelnir
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 4:24 pm

Momo1435 wrote:
Yes, Lion Air has put more seats in an A330 then any airline has done in the 787. But on the other side, Lion Air is now rumored to be close to placing a 787 order, at least that is what their CEO told the press a couple of weeks ago. So maybe we don't have to wait to long to be able to make an actual 1 on 1 comparison on the max seating of both models.


We know the max seating for those models. A330-900 440 pax, 787-9 420 and 787-10 440. The exit limit is the absolute limit.
 
LH707330
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 4:47 pm

Matt6461 wrote:
LH707330 wrote:
Matt6461 wrote:
There's no tech reason for the A330 to have significantly greater AR than 787.

Yeah there is: the A330/340 wing was deliberately designed with a high T/C ratio to get that aspect ratio, which involved sacrificing a few percent in cruise speed.


Good point.
Still, I wonder whether a .03M difference pencils out to ~15% AR penalty.

Where are you getting the 15% from, just out of curiosity? For argument's sake, let's assume that is the number. While the 330 has better aspect ratio and thus probably better induced drag numbers, the 12% T/C versus 9-10% (not sure about the 787) means more form drag on the 330. Given that tradeoff, it makes sense that the 787 has a faster optimum cruise, because it's relatively advantaged there. This goes back to Bjorn's thread about the stiff A wings and the noodly B wings with the inboard ailerons. What's interesting is that with the 350 and 787, the two seem to be converging relative to what they each built in the prior generations:

777>787: double to single slot flaps, simpler mechanisms, improved flaperon integration in trailing edge
330/340>350: more sweep, lower aspect ratio, faster optimum cruise, fewer flaptrack canoes

Both have converged on ~32 degree sweep, single slot flaps, and three canoes, though they're still a bit apart on wing stiffness and loading.
 
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Momo1435
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 4:52 pm

Yes we know those numbers.

But that doesn't make it any less interesting to see how many seats an airline that actually goes to the max on the A330 will put in their 787s. It's always good to see some real world examples when a discussion like this only turns into a screaming match, which happens way to often on this forum.
 
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Matt6461
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 5:25 pm

LH707300 wrote:
Given that tradeoff, it makes sense that the 787 has a faster optimum cruise, because it's relatively advantaged there.


The difference in cruise speed owes to the difference in drag divergence mach number (Mdd), not a tradeoff between non-compressive Dp and Di.
787 and A350 converge at .85M because that's their Mdd - go any faster and wave/compressibility drag increases at a high multiple of speed delta.

LH707300 wrote:
Where are you getting the 15% from, just out of curiosity?


It's based on effective AR. Bjorn/Ferpe gives 9.6 for 787 because nominal span > effective span for 787; 11 for A330NEO.

You're definitely correct that lower Mdd makes for higher optimal AR, I just doubt whether the AR/Mdd curve is so steep that you'd trade .03M for ~15% AR. Maybe it is? Plus we know that CFRP means a higher optimal AR than aluminum...

IIRC a good approximate relationship between t/c and Mdd trades them ~linearly. Does anyone have that formula? I remember Flipdewaf gave it once.
If .03 lower Mdd means ~4% t/c delta, that should mean ~4% wing bending weight delta. If bending weight is ~40% of wing weight then that's ~1.6% wing weight delta. From first principles you'd easily trade 1.6% wing weight for 15% higher AR in almost any case.
Maybe someone else knows these design tradeoffs better...

EDIT: on second thought, a linear t/c vs. Mdd tradeoff doesn't make much sense. I'm going to leave this scratch up just to lay out some picture of the tradeoff but my numbers are almost certainly far afield.
 
Bricktop
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 5:44 pm

keesje wrote:
Indeed Boeing has a majority of all civil aircraft in service.

They probably have an average 65% marketshare.

Over the last 40 years.

Image

Interesting, but maybe you should say it's the last forty years before the last eight.
 
Swadian
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 8:17 pm

Newbiepilot wrote:
keesje wrote:

I'm not of the 787-9 "small is fine" believers in a growing markets. I just don't see airlines downscaling from the 772ER from Asia for the next 20 years.


I remember you sharing that opinion a number of times in the AA 777-200ER thread before they cancelled the A350 order and selected the 787. Some airlines will choose the 787-9 and others will choose the A350-900 for transpacific flying. No one plane is perfect for every mission

From this thread:
viewtopic.php?f=3&t=1373579

keesje wrote:
It seems this post was well timed. :biggrin:

I think in this trade-off we shouldn't ignore the A350 is the must-have 300-350 seats /8000NM platform at this stage. AA & Leahy know all the numbers. It seems AA is negotiating price via the press.

...

The A350s offer more payload-range, comfort, bigger wings for hot airports and a growth option (-1000) for Asian flights. The 787-9 & -10 are better dimensioned for America's and Europe in this case.
.


The payload range of the A350 attractive over longer missions, but as we can tell from the number of 787-8s and 787-9s flying transpacific, the 787-9 is not only for the Americas and Europe. It can do transpacific.

The 787-10 certainly could be made to fly longer with higher MTOWs, but I think its simple stretch design is advantageous because it is one of the only widebodies built for the short to medium range high capacity markets.


I'm no A or B fanboy, but it's clear that AA does want to downsize and use the smallest plane possible for long routes. Most of the 77E flights at ORD were not replaced with 789, they were replaced with 788 and ORD-PEK is being discontinued. 788 and 789 are the perfect AA aircraft for the Pacific; 77Es are being sent to Hawaii, South America, and Europe.
Inland Streamliner
 
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keesje
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 8:23 pm

Isn't the AA order for 767/A330 replacement?
"Never mistake motion for action." Ernest Hemingway
 
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Polot
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 8:23 pm

Swadian wrote:
Newbiepilot wrote:
keesje wrote:

I'm not of the 787-9 "small is fine" believers in a growing markets. I just don't see airlines downscaling from the 772ER from Asia for the next 20 years.


I remember you sharing that opinion a number of times in the AA 777-200ER thread before they cancelled the A350 order and selected the 787. Some airlines will choose the 787-9 and others will choose the A350-900 for transpacific flying. No one plane is perfect for every mission

From this thread:
viewtopic.php?f=3&t=1373579

keesje wrote:
It seems this post was well timed. :biggrin:

I think in this trade-off we shouldn't ignore the A350 is the must-have 300-350 seats /8000NM platform at this stage. AA & Leahy know all the numbers. It seems AA is negotiating price via the press.

...

The A350s offer more payload-range, comfort, bigger wings for hot airports and a growth option (-1000) for Asian flights. The 787-9 & -10 are better dimensioned for America's and Europe in this case.
.


The payload range of the A350 attractive over longer missions, but as we can tell from the number of 787-8s and 787-9s flying transpacific, the 787-9 is not only for the Americas and Europe. It can do transpacific.

The 787-10 certainly could be made to fly longer with higher MTOWs, but I think its simple stretch design is advantageous because it is one of the only widebodies built for the short to medium range high capacity markets.


I'm no A or B fanboy, but it's clear that AA does want to downsize and use the smallest plane possible for long routes. Most of the 77E flights at ORD were not replaced with 789, they were replaced with 788 and ORD-PEK is being discontinued. 788 and 789 are the perfect AA aircraft for the Pacific; 77Es are being sent to Hawaii, South America, and Europe.

That’s because for years AA only had 2 intercontinental widebodies: the 763ER and the 77E. Need more range than the 763ER? Have to use the 77E. Need more capacity than the 763? Have to use the 77E. You can see the effects of this in AA’s fleet useage- the 777 operates tons of short (~4000 nm) routes.

Now with future planes of various sizes AA can and is right-sizing 777 routes, and can also replace 777s with planes with less payload/range (don’t need the capability of the A359 to replace a 77E on JFK-LHR for example). Not every 77E in the world will be replaced by something of equal capability. Not every 77E operator is using the plane to it’s full capabaility, in fact that is why the A333 killed off the 77E a decade ago. Some members here have trouble grasping that concept though.
 
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keesje
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 8:25 pm

Isn't the AA order for 767/A330 replacement? There will probably be another order for 777 replacements.
"Never mistake motion for action." Ernest Hemingway
 
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Polot
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Re: a MTOW increase on 787-10 to compete with A359?

Tue May 15, 2018 8:27 pm

keesje wrote:
Isn't the AA order for 767/A330 replacement? There will probably be another order for 777 replacements.

They have also stated they will replace some of the older 77Es.
 
rbavfan
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 6:45 am

WIederling wrote:
rbavfan wrote:
No they have the same exit limit for number of doors.

They are not approved for the same exit limits for seating in real operations. Boeing specs from: 787 Airplane Characteristics for Airport Planning are as follows. 787-8 limits 359 seats all-economy seats; FAA exit limit = 381 seats. 787-9 limits 406 seats all-economy seats; FAA exit limit = 420 seats.


There is no further limit than "exit limit".

What you pull from the ACAPS is a reference layout offered by the manufacturer.
there are other "limiting" metrics around: like number of FAs required : with the "last FA" on occasion
handling a handfull only introduces a cost vs revenue limit.


My point was the 787-9 has 4 doors which should allow 440 seats, but the FAA says only 381 are allowed. Same on the 787-9 440 based on number of doors, but FAA only allows 420. As such the number of doors as a seating limit does not mean that many seats can actually be installed by FAA/EASA rules. In other words people need to stop saying a 3 door WB will seat 330 seats, a 4 door WB will seat 440 seats & a 5 door model will seat 550. It is NOT accurate.
 
rbavfan
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 7:02 am

mjoelnir wrote:
RJMAZ wrote:
mjoelnir wrote:
You can put 440 passengers in a A330-900 and you can put 440 passengers in a 787-10, that are maximum numbers.

As pointed out they are theoretical maximum numbers and don't apply to the 1000+ aircraft in service. It is irrelevant and It only applies to a handful of aircraft.

Airbus could fit a dozen doors and make the exit limit 600 on the A330. You could fit 9ab with 26" pitch using slim seats and move all the toilets and food prep areas underneith. You would easily hit 500+ seats. So based on this the 777-9 is the direct competitor to the A330-900. All hail the almighty A330! :banghead:

As already pointed out many times by multiple users they aren't comparible. The 787-9 seats more seats than the A330-900 let alone the 787-10

Image
Both existing cabins with their business cabins replaced with economy seats.

So the 787-10 seats far more than the A330-900. If you fit the same amount of seats in both the 787-10 will be far more comfortable.


The A330-300 is used with 440 pax. We are not talking about a dozen doors. I am talking about a setup used.

I was talking about LCC and ULCC not mainline. I was not talking about comfort levels. I was simply talking about the fact that if an ULCC uses the A330-900 with maximum pax, they will not be able to fit more pax in neither the 787-9, nor the 787-10.

Perhaps if you bang your head a little more you would not try to confuse facts.



Wrong depending on door types used the A330 has a limit of 375 (8 FA's), 400 (8 FA's) or 420 (9 FA's) seats max per EASA, NOT 440. See page 32 of the following EASA TYPE-CERTIFICATE DATA SHEET for the A330. It shows both max seating for each configuration of the 4 doors & the required FA's for them.

https://www.easa.europa.eu/sites/defaul ... 092017.pdf
 
NZ321
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 7:02 am

This thread seems to have gone a bit off topic. Wasn't the question as to whether to increase the take-off weight of the 787-10, indeed, how possible would this even be? It seems to be in danger of turning into another A vs B thread. I'm interested in the actual technical information in terms of what would be involved in a 78J MTOW increase. Flew on this bird a couple of weeks ago and am looking forward to another flight soon.
Plane mad!
 
rbavfan
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 7:08 am

mjoelnir wrote:
RJMAZ wrote:
mjoelnir wrote:
You can put 440 passengers in a A330-900 and you can put 440 passengers in a 787-10, that are maximum numbers.

As pointed out they are theoretical maximum numbers and don't apply to the 1000+ aircraft in service. It is irrelevant and It only applies to a handful of aircraft.

Airbus could fit a dozen doors and make the exit limit 600 on the A330. You could fit 9ab with 26" pitch using slim seats and move all the toilets and food prep areas underneith. You would easily hit 500+ seats. So based on this the 777-9 is the direct competitor to the A330-900. All hail the almighty A330! :banghead:

As already pointed out many times by multiple users they aren't comparible. The 787-9 seats more seats than the A330-900 let alone the 787-10

Image
Both existing cabins with their business cabins replaced with economy seats.

So the 787-10 seats far more than the A330-900. If you fit the same amount of seats in both the 787-10 will be far more comfortable.


The A330-300 is used with 440 pax. We are not talking about a dozen doors. I am talking about a setup used.

I was talking about LCC and ULCC not mainline. I was not talking about comfort levels. I was simply talking about the fact that if an ULCC uses the A330-900 with maximum pax, they will not be able to fit more pax in neither the 787-9, nor the 787-10.

Perhaps if you bang your head a little more you would not try to confuse facts.


Perhaps if you read the EASA TYPE-CERTIFICATE DATA SHEET for the A330 you would not confuse the facts. Your assuming that 4 doors on the airframe mean it can legally be configured for 440 seats. Same on the 787 series the FAA limits the capacity allowed, not the 4 doors. Before you tell someone they should bang their head more so not to confuse facts, you should look the FACTS UP! The FAA and EASA give the facts. READ them.

https://www.easa.europa.eu/sites/defaul ... 092017.pdf
 
VV
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 7:17 am

"a MTOW increase on 787-10 to compete with A359?"

Why would you do that?
 
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Qantas94Heavy
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 7:46 am

rbavfan wrote:
Perhaps if you read the EASA TYPE-CERTIFICATE DATA SHEET for the A330 you would not confuse the facts. Your assuming that 4 doors on the airframe mean it can legally be configured for 440 seats. Same on the 787 series the FAA limits the capacity allowed, not the 4 doors. Before you tell someone they should bang their head more so not to confuse facts, you should look the FACTS UP! The FAA and EASA give the facts. READ them.

https://www.easa.europa.eu/sites/defaul ... 092017.pdf


Before accusing someone of not reading a document properly, it might be worth actually reading the document you listed.

If you did, you would clearly see that the A330-300 has a certified exit rating of 440 passengers with 4 Type A exits.

Image
 
flipdewaf
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 9:43 am

Matt6461 wrote:
LH707300 wrote:
Given that tradeoff, it makes sense that the 787 has a faster optimum cruise, because it's relatively advantaged there.


The difference in cruise speed owes to the difference in drag divergence mach number (Mdd), not a tradeoff between non-compressive Dp and Di.
787 and A350 converge at .85M because that's their Mdd - go any faster and wave/compressibility drag increases at a high multiple of speed delta.

LH707300 wrote:
Where are you getting the 15% from, just out of curiosity?


It's based on effective AR. Bjorn/Ferpe gives 9.6 for 787 because nominal span > effective span for 787; 11 for A330NEO.

You're definitely correct that lower Mdd makes for higher optimal AR, I just doubt whether the AR/Mdd curve is so steep that you'd trade .03M for ~15% AR. Maybe it is? Plus we know that CFRP means a higher optimal AR than aluminum...

IIRC a good approximate relationship between t/c and Mdd trades them ~linearly. Does anyone have that formula? I remember Flipdewaf gave it once.
I use Mdd = (0.95-t/c-Cl/10)/cos(Sweep). This was suggested in the stamford course for "peaky" aerofoils.

Matt6461 wrote:
If .03 lower Mdd means ~4% t/c delta, that should mean ~4% wing bending weight delta. If bending weight is ~40% of wing weight then that's ~1.6% wing weight delta. From first principles you'd easily trade 1.6% wing weight for 15% higher AR in almost any case.
Maybe someone else knows these design tradeoffs better...
My estimation calcs (and intuition) says that the weight of the wing is a function of the 'real' span^3 (makes sense) and 1/(t/c) (also makes sense).

Be careful with the t/c values and how you compare them i.e. t/c=0.12 is not 2% higher than t/c=0.1 it is 20% higher.

Fred
Image
 
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keesje
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 9:50 am

VV wrote:
"a MTOW increase on 787-10 to compete with A359?"

Why would you do that?


"..to compete withA359?"
"Never mistake motion for action." Ernest Hemingway
 
WIederling
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 10:13 am

rbavfan wrote:
My point was the 787-9 has 4 doors which should allow 440 seats, but the FAA says only 381 are allowed.


Not all doors are equal ( and the spacing neither i.e. you may have the doors right but the spacing "wrong" :-) :
ref: http://rgl.faa.gov/Regulatory_and_Guida ... Rev_27.pdf

Maximum Passengers: ( 787-8 )
The maximum number of passengers approved for e m ergency evacuation is:
381 with four pairs of exits in an (A, A, A, A) exit arrangement,
355 with four pairs of exits in a (C, A, A, A) exit arrangement,
330 with four pairs of exits in an (A, A, C, A) exit arrangement, and
300 with four pairs of exits in a (C, A, C, A) exit arrangement.

Maximum Passengers: ( 787-9 )
The maximum number of passengers approved for e m ergency evacuation is:
420 with four pairs of exits in an (A, A, A, A) exit arrangement,
355 with four pairs of exits in a (C, A, A, A) exit arrangement,
355 with four pairs of exits in an (A, A, C, A) exit arrangement,
300 with four pairs of exits in a (C, A, C, A) exit arrangement


Maximum Passengers: ( 787-10 )
The maximum number of passengers approved for e m ergency evacuation is:
< not in the TCD yet >
Murphy is an optimist
 
mjoelnir
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 10:45 am

rbavfan wrote:
WIederling wrote:
rbavfan wrote:
No they have the same exit limit for number of doors.

They are not approved for the same exit limits for seating in real operations. Boeing specs from: 787 Airplane Characteristics for Airport Planning are as follows. 787-8 limits 359 seats all-economy seats; FAA exit limit = 381 seats. 787-9 limits 406 seats all-economy seats; FAA exit limit = 420 seats.


There is no further limit than "exit limit".

What you pull from the ACAPS is a reference layout offered by the manufacturer.
there are other "limiting" metrics around: like number of FAs required : with the "last FA" on occasion
handling a handfull only introduces a cost vs revenue limit.


My point was the 787-9 has 4 doors which should allow 440 seats, but the FAA says only 381 are allowed. Same on the 787-9 440 based on number of doors, but FAA only allows 420. As such the number of doors as a seating limit does not mean that many seats can actually be installed by FAA/EASA rules. In other words people need to stop saying a 3 door WB will seat 330 seats, a 4 door WB will seat 440 seats & a 5 door model will seat 550. It is NOT accurate.


There can be 440 seats installed in the A330-300 and A330-900. Cebu Pacific does 436, Lion Air does 440 on the A330-300. Real World numbers. Just take the fact.
Regarding comfort, there is non. 16.5 inch seat and about 30 inch pitch.

So all the same if you look at the 787-9, limit 420, or 787-10, limit 440, an ULCC or LCC will not be able to press more pax in a 787 than the A330-300/900.
 
parapente
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 10:47 am

NZ321.Regarding the main topic as you state.
My understanding is that the 787 as an aircraft 'package' is maxed out.You can have range but less pax (789) or 'max pax' but less range.
But not both at the same time!Physics doesn't work like that.
The 787 series is an incredible aircraft family as it is.
The 788 has effectively replaced the longer range 767's and indeed the 332/8
The 789 is a replacement for the 333/339.And it's doing superbly at its job.Indeed if you needA359 range but not capacity then it does that too.
The 7810 is like a 772 (non er).On shorter/ mid missions it does what the A359 does but more economically.The British Airways order was telling in that respect.They had bought both the 789 and the. 3510 so the 'middle. Plane' was right in the balance.However in BA'scase it does not need the 359 range so went for the 10 (just like Emirates).
But the plane ( wing,engine,MLG,structure etc) is totally maxed out now.It can't be. Everything to everybody.
Perhaps an interesting question is whether Airbus over spec'd the A359.I suspect - looking at their order book- the answer is a firm no.
Horses for courses.
 
VV
Posts: 218
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 11:13 am

keesje wrote:
VV wrote:
"a MTOW increase on 787-10 to compete with A359?"

Why would you do that?


"..to compete withA359?"


Why would you do that?
 
User avatar
Momo1435
Posts: 675
Joined: Sat Aug 25, 2012 2:33 pm

Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 11:26 am

parapente wrote:
NZ321.Regarding the main topic as you state.
My understanding is that the 787 as an aircraft 'package' is maxed out.You can have range but less pax (789) or 'max pax' but less range.
But not both at the same time!Physics doesn't work like that.
The 787 series is an incredible aircraft family as it is.
The 788 has effectively replaced the longer range 767's and indeed the 332/8
The 789 is a replacement for the 333/339.And it's doing superbly at its job.Indeed if you needA359 range but not capacity then it does that too.
The 7810 is like a 772 (non er).On shorter/ mid missions it does what the A359 does but more economically.The British Airways order was telling in that respect.They had bought both the 789 and the. 3510 so the 'middle. Plane' was right in the balance.However in BA'scase it does not need the 359 range so went for the 10 (just like Emirates).
But the plane ( wing,engine,MLG,structure etc) is totally maxed out now.It can't be. Everything to everybody.
Perhaps an interesting question is whether Airbus over spec'd the A359.I suspect - looking at their order book- the answer is a firm no.
Horses for courses.

It's only maxed because Boeing wanted to keep the 787-10 as similar to the 787-9 as possible.

If you look at the changes from the 773 to the 77W, new engine, new MLG, new wingtips, a strengthened fuselage, it's all the things you mention that might be maxed out. So if Boeing wants to upgrade the 787-10 they will have to do similar upgrades as they did with the 773 to the 77W.
I don't think it's a technical issue that keeps Boeing doing it. The success of the A359 shows there's a big demand for a plane in this market segment. Instead the financial side of the story, meaning another big investment in the 787 for an MTOW increase is what preventing Boeing from doing this 787-10ER (for now).

I'm sure that Boeing will consider it if 1: there are enough airlines asking Boeing to do it and want to pay for it. or 2: if there's a new engine that is so much more efficient then the current engines that it will simply be needed to do an upgrade. With that engine upgrade it would also be a good time to do some more upgrades. Right now both options are not actual, so Boeing will keep on selling the current 787-10 to the customers who don't need the extra MTOW.

@VV
Why competing with the A359. It's an interesting market segment. If Boeing can easily compete with the A359 without having to make a big investment they can take a nice piece of that market. And it's not just from a competition with Airbus perspective, as they will also be able to offer their customers an even more capable 787 in a popular market segment.
 
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par13del
Posts: 8125
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 11:27 am

If the 787 is upgraded to compete with the A359, the A330 which made the 767 obsolete will be in a space by itself thus forcing Boeing to either abandon the market segment or design a new clean sheet as a replacement for the 767 and a competitor to the A330NEO, seems pretty straight jacket.. forward to me....
 
mjoelnir
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 12:39 pm

Momo1435 wrote:
parapente wrote:
NZ321.Regarding the main topic as you state.
My understanding is that the 787 as an aircraft 'package' is maxed out.You can have range but less pax (789) or 'max pax' but less range.
But not both at the same time!Physics doesn't work like that.
The 787 series is an incredible aircraft family as it is.
The 788 has effectively replaced the longer range 767's and indeed the 332/8
The 789 is a replacement for the 333/339.And it's doing superbly at its job.Indeed if you needA359 range but not capacity then it does that too.
The 7810 is like a 772 (non er).On shorter/ mid missions it does what the A359 does but more economically.The British Airways order was telling in that respect.They had bought both the 789 and the. 3510 so the 'middle. Plane' was right in the balance.However in BA'scase it does not need the 359 range so went for the 10 (just like Emirates).
But the plane ( wing,engine,MLG,structure etc) is totally maxed out now.It can't be. Everything to everybody.
Perhaps an interesting question is whether Airbus over spec'd the A359.I suspect - looking at their order book- the answer is a firm no.
Horses for courses.

It's only maxed because Boeing wanted to keep the 787-10 as similar to the 787-9 as possible.

If you look at the changes from the 773 to the 77W, new engine, new MLG, new wingtips, a strengthened fuselage, it's all the things you mention that might be maxed out. So if Boeing wants to upgrade the 787-10 they will have to do similar upgrades as they did with the 773 to the 77W.
I don't think it's a technical issue that keeps Boeing doing it. The success of the A359 shows there's a big demand for a plane in this market segment. Instead the financial side of the story, meaning another big investment in the 787 for an MTOW increase is what preventing Boeing from doing this 787-10ER (for now).

I'm sure that Boeing will consider it if 1: there are enough airlines asking Boeing to do it and want to pay for it. or 2: if there's a new engine that is so much more efficient then the current engines that it will simply be needed to do an upgrade. With that engine upgrade it would also be a good time to do some more upgrades. Right now both options are not actual, so Boeing will keep on selling the current 787-10 to the customers who don't need the extra MTOW.

@VV
Why competing with the A359. It's an interesting market segment. If Boeing can easily compete with the A359 without having to make a big investment they can take a nice piece of that market. And it's not just from a competition with Airbus perspective, as they will also be able to offer their customers an even more capable 787 in a popular market segment.


The move from the 777-300 to the 777-300ER is not comparable to what you have to do to the 787-10 to increase MTOW. Just look at the MLG. The 777-300ER is in principle still the same MLG the 777-200 started out with. 2 six wheel bogies. Looking at the 777-300ER you find simply bigger wheels, overall strengthening of components and a looking mechanism so at rotation the airplane rotates around the back tires rather than the attachment point of the bogies.

The 787-10 would have to move either to a big four wheel bogie like the A350, or to a six wheel bogie. The current MLG is maxed out.

The 777 was designed with reserves. The 787 is maxed out. That is exactly why the 787 is more economical, no unnecessary additional structure to carry around.
 
Newbiepilot
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 1:43 pm

mjoelnir wrote:

The move from the 777-300 to the 777-300ER is not comparable to what you have to do to the 787-10 to increase MTOW. Just look at the MLG. The 777-300ER is in principle still the same MLG the 777-200 started out with. 2 six wheel bogies. Looking at the 777-300ER you find simply bigger wheels, overall strengthening of components and a looking mechanism so at rotation the airplane rotates around the back tires rather than the attachment point of the bogies.

The 787-10 would have to move either to a big four wheel bogie like the A350, or to a six wheel bogie. The current MLG is maxed out.

The 777 was designed with reserves. The 787 is maxed out. That is exactly why the 787 is more economical, no unnecessary additional structure to carry around.


Your post is kind of contradicting itself. You say the 777-300ER gear is in principle the same as the 777-200 and then list all the things that are different such as tires, structural components, semi levered main gear and dual camber nose gear (you didn’t mention that, but I thought it was worth adding). The landing gear on the 777-300er is quite different unless you are looking at it from 50 feet away and only counting tires. Have you ever seen the gear up close? I would love to show you the shock strut differences, tilt actuator, etc.

The 787-10 gear is also semi-levered. I agree they didn’t leave in extra capability for future weigh upgrades like they did on the 777. With the 787, the airframe wasn’t leading engines and waiting for more powerful engines to be developed like the 777 was. The 777 design had extra capability because in the early 1990s, Boeing was really pushing the max thrust possible out of an engine. The 787 doesn’t have that challenge. With that said, airplanes can be modified and redesigned to increase capability. Boeing probably studied the cost of spreading axles further apart and bigger tires. The A359 has a 60K lbs higher MTOW with two main axles. Boeing probably also studied options to add a tail skid or tail strike software to help increase MTOW. All those things are possible, but at a cost.

I think it is erroneous to say the 787 is maxed out. It certainly could be made to carry more payload, But that comes at a cost in price plus fuel burn and from looking at their decisions so far, there probably was not a business case to do so. That may change in the future, but for now an airline can also choose the 777 if they need more payload.
 
mjoelnir
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 2:55 pm

Newbiepilot wrote:
mjoelnir wrote:

The move from the 777-300 to the 777-300ER is not comparable to what you have to do to the 787-10 to increase MTOW. Just look at the MLG. The 777-300ER is in principle still the same MLG the 777-200 started out with. 2 six wheel bogies. Looking at the 777-300ER you find simply bigger wheels, overall strengthening of components and a looking mechanism so at rotation the airplane rotates around the back tires rather than the attachment point of the bogies.

The 787-10 would have to move either to a big four wheel bogie like the A350, or to a six wheel bogie. The current MLG is maxed out.

The 777 was designed with reserves. The 787 is maxed out. That is exactly why the 787 is more economical, no unnecessary additional structure to carry around.


Your post is kind of contradicting itself. You say the 777-300ER gear is in principle the same as the 777-200 and then list all the things that are different such as tires, structural components, semi levered main gear and dual camber nose gear (you didn’t mention that, but I thought it was worth adding). The landing gear on the 777-300er is quite different unless you are looking at it from 50 feet away and only counting tires. Have you ever seen the gear up close? I would love to show you the shock strut differences, tilt actuator, etc.

The 787-10 gear is also semi-levered. I agree they didn’t leave in extra capability for future weigh upgrades like they did on the 777. With the 787, the airframe wasn’t leading engines and waiting for more powerful engines to be developed like the 777 was. The 777 design had extra capability because in the early 1990s, Boeing was really pushing the max thrust possible out of an engine. The 787 doesn’t have that challenge. With that said, airplanes can be modified and redesigned to increase capability. Boeing probably studied the cost of spreading axles further apart and bigger tires. The A359 has a 60K lbs higher MTOW with two main axles. Boeing probably also studied options to add a tail skid or tail strike software to help increase MTOW. All those things are possible, but at a cost.

I think it is erroneous to say the 787 is maxed out. It certainly could be made to carry more payload, But that comes at a cost in price plus fuel burn and from looking at their decisions so far, there probably was not a business case to do so. That may change in the future, but for now an airline can also choose the 777 if they need more payload.


The MLG is still the same size and fits in the same space when retracted regarding the 777 family. Is it really so difficult to understand the difference between reinforcing and developing a design regarding a MLG and having to do a completely new one in a different size?
I assume the 787 will need a bigger wheel well to accommodate a big four wheel or six wheel bogie. That could mean changes to the wing box with all the related changes.

The 777-300ER finally maxed out that MLG design, that is why we see no MTOW increase for the 777-9 over and above the 777-300ER.

The 787-9/10 maxed out its current MLG design. The wings are also not big enough for a serious MTOW increase. Of course you can develop a new version 787 out of the current 787, but that was not what happened when the 777-300 grew to be the 777-300ER, the reserves in the frame were there, but today the 777-300ER wings are smaller than a new designed wing would be.
 
JayinKitsap
Posts: 834
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 3:17 pm

Boeing right now has a nice space between the 787-10 and the 778, if the -10 can't do a mission choose the 778. The 787 lines are rather full at 14/month with backlog out 5 to 6 years. Why would you spend billions doing an upgrade now in that situation. Maybe in a decade with a new really good engine available. Better to spend that $ on the MOM.
 
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Momo1435
Posts: 675
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 3:34 pm

mjoelnir wrote:
Newbiepilot wrote:
mjoelnir wrote:

The move from the 777-300 to the 777-300ER is not comparable to what you have to do to the 787-10 to increase MTOW. Just look at the MLG. The 777-300ER is in principle still the same MLG the 777-200 started out with. 2 six wheel bogies. Looking at the 777-300ER you find simply bigger wheels, overall strengthening of components and a looking mechanism so at rotation the airplane rotates around the back tires rather than the attachment point of the bogies.

The 787-10 would have to move either to a big four wheel bogie like the A350, or to a six wheel bogie. The current MLG is maxed out.

The 777 was designed with reserves. The 787 is maxed out. That is exactly why the 787 is more economical, no unnecessary additional structure to carry around.


Your post is kind of contradicting itself. You say the 777-300ER gear is in principle the same as the 777-200 and then list all the things that are different such as tires, structural components, semi levered main gear and dual camber nose gear (you didn’t mention that, but I thought it was worth adding). The landing gear on the 777-300er is quite different unless you are looking at it from 50 feet away and only counting tires. Have you ever seen the gear up close? I would love to show you the shock strut differences, tilt actuator, etc.

The 787-10 gear is also semi-levered. I agree they didn’t leave in extra capability for future weigh upgrades like they did on the 777. With the 787, the airframe wasn’t leading engines and waiting for more powerful engines to be developed like the 777 was. The 777 design had extra capability because in the early 1990s, Boeing was really pushing the max thrust possible out of an engine. The 787 doesn’t have that challenge. With that said, airplanes can be modified and redesigned to increase capability. Boeing probably studied the cost of spreading axles further apart and bigger tires. The A359 has a 60K lbs higher MTOW with two main axles. Boeing probably also studied options to add a tail skid or tail strike software to help increase MTOW. All those things are possible, but at a cost.

I think it is erroneous to say the 787 is maxed out. It certainly could be made to carry more payload, But that comes at a cost in price plus fuel burn and from looking at their decisions so far, there probably was not a business case to do so. That may change in the future, but for now an airline can also choose the 777 if they need more payload.


The MLG is still the same size and fits in the same space when retracted regarding the 777 family. Is it really so difficult to understand the difference between reinforcing and developing a design regarding a MLG and having to do a completely new one in a different size?
I assume the 787 will need a bigger wheel well to accommodate a big four wheel or six wheel bogie. That could mean changes to the wing box with all the related changes.

The 777-300ER finally maxed out that MLG design, that is why we see no MTOW increase for the 777-9 over and above the 777-300ER.

The 787-9/10 maxed out its current MLG design. The wings are also not big enough for a serious MTOW increase. Of course you can develop a new version 787 out of the current 787, but that was not what happened when the 777-300 grew to be the 777-300ER, the reserves in the frame were there, but today the 777-300ER wings are smaller than a new designed wing would be.
That's why I say it's financial reason why Boeing isn't increasing the MTOW right now. Boeing can improve the 787-10, but it will be a big investment. And they are also tired of reading the same acounting discussion over and over again when they read this forum... With such investment the deffered costs would increase significantly again...
 
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Stitch
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Re: a MTOW increase on 787-10 to compete with A359?

Wed May 16, 2018 3:42 pm

rbavfan wrote:
My point was the 787-9 has 4 doors which should allow 440 seats, but the FAA says only 381 are allowed. Same on the 787-9 440 based on number of doors, but FAA only allows 420. As such the number of doors as a seating limit does not mean that many seats can actually be installed by FAA/EASA rules. In other words people need to stop saying a 3 door WB will seat 330 seats, a 4 door WB will seat 440 seats & a 5 door model will seat 550. It is NOT accurate.


Boeing did not perform physical Evacuation Tests for the 787 family. Instead, they used the 767 family Evacuation Tests to show via computer analysis that the 787-8 and 787-9 could be evacuated as quickly as a 767. As such, the 787-8 and 787-9 were certified by the FAA using the lower Exit Limits of the 767-300 and 767-400. If Boeing had performed a physical Evacuation Test on both models, they would have received a maximum Exit Limit of 440 with four Type A doors.

Boeing did the same with the 787-10, using the 777-200 as the comparison and therefore it received the full 440 seats with four Type A doors because that is what the 777-200 family is certified at with four Type A doors.
 
Newbiepilot
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Re: a MTOW increase on 787-10 to compete with A359?

Thu May 17, 2018 3:13 am

mjoelnir wrote:


The MLG is still the same size and fits in the same space when retracted regarding the 777 family. Is it really so difficult to understand the difference between reinforcing and developing a design regarding a MLG and having to do a completely new one in a different size?
I assume the 787 will need a bigger wheel well to accommodate a big four wheel or six wheel bogie. That could mean changes to the wing box with all the related changes.

The 777-300ER finally maxed out that MLG design, that is why we see no MTOW increase for the 777-9 over and above the 777-300ER.

The 787-9/10 maxed out its current MLG design. The wings are also not big enough for a serious MTOW increase. Of course you can develop a new version 787 out of the current 787, but that was not what happened when the 777-300 grew to be the 777-300ER, the reserves in the frame were there, but today the 777-300ER wings are smaller than a new designed wing would be.


I’d like to know how you came to the conclusion that the 787-10 would need a completely new gear if MTOW was increased. Do you know exactly what the pavement loading is for the 787-10? Do you know what the tire diameter and width is? Or is your opinion based on assumptions and anecdote? In a way every design is maxed out until it is redesigned for more capability. I know the difference between reinforcing and redesign. Bulkheads can be moved, tire dimensions can be increased, brakes can get bigger, axle separation can change, etc.

In general a 1 inch increase in tire diameter increases contact area sufficiently to allow about 1,000lbs more weight to be carried while maintaining pavement loading. If you want to see some numbers, I can go look for the landing gear interchangeability document if you’d like. Given 8 main tires, a 4 inch increase in diameter would allow about 30K lbs in weight increase. Of course rotation speeds, landing speeds, tail strike risk, gear weight, wingbox strengthening, wing strengthening, thrust ratings, etc all change as well and result in redesign efforts. That is the business case that needs to be made to justify an increase in MTOW. I don’t think it is reasonable to say that the 787-10 would need a completely new gear unless you can provide some facts and data.
 
JayinKitsap
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Re: a MTOW increase on 787-10 to compete with A359?

Thu May 17, 2018 4:01 am

I recall the original 789 specification was for a lower MTOW, but with the testing done on the 788 they increased the MTOW to its current value basically taking out excess reserve. The -10 was done to have the most commonality of parts with the -9. Until a decade or more goes by and new engines are available it makes little financial sense to do it.
 
Newbiepilot
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Joined: Tue Aug 30, 2016 10:18 pm

Re: a MTOW increase on 787-10 to compete with A359?

Thu May 17, 2018 4:09 am

JayinKitsap wrote:
I recall the original 789 specification was for a lower MTOW, but with the testing done on the 788 they increased the MTOW to its current value basically taking out excess reserve. The -10 was done to have the most commonality of parts with the -9. Until a decade or more goes by and new engines are available it makes little financial sense to do it.


I agree with one caveat. If a group of airlines or even a single airline comes in and says they will pay $X more for Y planes, and if it covers development costs, I could see Boeing launching a higher weight version. If an airline wants it enough to pay for it, I could see it happening.
 
rheinwaldner
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Re: a MTOW increase on 787-10 to compete with A359?

Thu May 17, 2018 6:05 am

Newbiepilot wrote:
In general a 1 inch increase in tire diameter increases contact area sufficiently to allow about 1,000lbs more weight to be carried while maintaining pavement loading.

Source? I cant find wheel diameter mentioned in any of the following links:
https://www.civil.iitb.ac.in/tvm/1100_L ... plain.html
http://aviationweek.com/bca/landing-ass ... arture-not
http://code7700.com/acn_v_pcn.htm
https://repository.tudelft.nl/islandora ... 53b5bac054 (chapter 10)
Many things are difficult, all things are possible!
 
WIederling
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Re: a MTOW increase on 787-10 to compete with A359?

Thu May 17, 2018 6:47 am

Newbiepilot wrote:
... some facts and data.


Hard data is that the 787 MTOW seems to be up against a hard wall. last 5..8 years have just squeezed another ton or two out of the design. The wing is thin. not much room behind the wingbox to stow more gear.

Then it is not only about per tire loading but also about the area spanned by the gear truck foot print.
There is a reason why the A359 has that camel toe splayed layout.

If you have finally worked around those limitations you can continue over to the wing and enlarge that.
787 Wingloading @254t is rather high.

to conclude: the 787 is a maxed out design from day one ( of actual use ).
all the design reserves ( intended for later improvements ( 20.25t?)) have been squandered in fixing issues on the initial product.
Like the initial offering 787 performance hangs on engine performance and will only grow further with continuing engine PIPs.
Murphy is an optimist
 
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keesje
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Re: a MTOW increase on 787-10 to compete with A359?

Thu May 17, 2018 7:26 am

VV wrote:
keesje wrote:
VV wrote:
"a MTOW increase on 787-10 to compete with A359?"

Why would you do that?


"..to compete withA359?"


Why would you do that?


To sell aircraft, pay salaries and other bills, invest a bit. It's what they do.

https://www.boeing.com/resources/boeingdotcom/commercial/market/current-market-outlook-2017/assets/downloads/cmo-2017-executive-summary_0919.pdf
"Never mistake motion for action." Ernest Hemingway
 
mjoelnir
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Re: a MTOW increase on 787-10 to compete with A359?

Thu May 17, 2018 9:41 am

Newbiepilot wrote:
mjoelnir wrote:


The MLG is still the same size and fits in the same space when retracted regarding the 777 family. Is it really so difficult to understand the difference between reinforcing and developing a design regarding a MLG and having to do a completely new one in a different size?
I assume the 787 will need a bigger wheel well to accommodate a big four wheel or six wheel bogie. That could mean changes to the wing box with all the related changes.

The 777-300ER finally maxed out that MLG design, that is why we see no MTOW increase for the 777-9 over and above the 777-300ER.

The 787-9/10 maxed out its current MLG design. The wings are also not big enough for a serious MTOW increase. Of course you can develop a new version 787 out of the current 787, but that was not what happened when the 777-300 grew to be the 777-300ER, the reserves in the frame were there, but today the 777-300ER wings are smaller than a new designed wing would be.


I’d like to know how you came to the conclusion that the 787-10 would need a completely new gear if MTOW was increased. Do you know exactly what the pavement loading is for the 787-10? Do you know what the tire diameter and width is? Or is your opinion based on assumptions and anecdote? In a way every design is maxed out until it is redesigned for more capability. I know the difference between reinforcing and redesign. Bulkheads can be moved, tire dimensions can be increased, brakes can get bigger, axle separation can change, etc.

In general a 1 inch increase in tire diameter increases contact area sufficiently to allow about 1,000lbs more weight to be carried while maintaining pavement loading. If you want to see some numbers, I can go look for the landing gear interchangeability document if you’d like. Given 8 main tires, a 4 inch increase in diameter would allow about 30K lbs in weight increase. Of course rotation speeds, landing speeds, tail strike risk, gear weight, wingbox strengthening, wing strengthening, thrust ratings, etc all change as well and result in redesign efforts. That is the business case that needs to be made to justify an increase in MTOW. I don’t think it is reasonable to say that the 787-10 would need a completely new gear unless you can provide some facts and data.


Why should I do the work for you? Your point seems to be that it can not be, that there are limits. Perhaps because it is a Boeing or something like that.

Pavement loading is not only one point loads, but also the area in regards to weight. Start to have a look at a comparable MLG, that would be the A330. Than have a look at frames having a higher MTOW. The A340 adds a center MLG with 2 wheels on the A340-200/300 and the A340-500/600 adds a center MLG with a 4 wheel bogie. The A350-900 has a 4 wheel bogie yes, but quite a bit bigger size, as in spreading out the contact points. The A350-1000 and 777 go for 6 wheel bogies. The 747 and A380 really spread it out with 4 bogies. You can also look at the DC10 and the Lookhead Tristar. The Tristar has 2 four wheel bogies and a MTOW of 231t and the MLG has limited it in regards of MTOW increase. The DC10 has 2 four wheel bogies and goes for the center leg to manage 259.5 t and the MD11 goes to 286 t on that design. All those comparisons would already show you that the 787-9/10 has already a rather high MTOW in regards to the size of the MLG.

They do it all build bigger MLG for fun and games only, because you decided a 4 wheel bogie sized like the one on the 787-9/10 has no weight limits.
 
RJMAZ
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Re: a MTOW increase on 787-10 to compete with A359?

Thu May 17, 2018 1:26 pm

Newbiepilot wrote:
I’d like to know how you came to the conclusion that the 787-10 would need a completely new gear if MTOW was increased. Do you know exactly what the pavement loading is for the 787-10? Do you know what the tire diameter and width is? Or is your opinion based on assumptions and anecdote?

Actually the 787-10 pavement loadings are all in the ACAP's. It has one of the highest pavement loadings ever.

On a rigid high strength pavement it has a pavement rating of 66. This is equal highest with the 777-300ER.

So saying a new gear is required is a fair call. I highly doubt you could increase the 787-10 MTOW by more than 5T.

Countless airports had to be upgraded to operate the 777-300ER. The 787-10 requires 777-300ER standard airports. This already limits the 787-10 to be used only at major hubs. A 5T MTOW increase would probably exceed the pVement loading limits of some major hubs.

The 787-10 already has the largest diameter and width tyres.

The A350-900 tyres are the same sized but are rated higher with more plys. This is to allow a higher tyre pressure. Higher tyre pressure reduces the contact patch on the 787-10 and actually increases pavement loading further.

There is also absolutely no way a 6 wheel bogie can fit the 787 without massive modifications. I've looked at some drawings and there is zero room. The A350-900 wheels are actually highly spaced front to rear, so the A350-1000 with three smaller tyres isn't noticeably longer. The 787-10 wheels are very closely spaced front to rear.

The only option would be maybe to increase the bogie width by a couple inches this could allow a very slightly increase.
 
Newbiepilot
Posts: 3223
Joined: Tue Aug 30, 2016 10:18 pm

Re: a MTOW increase on 787-10 to compete with A359?

Thu May 17, 2018 1:30 pm

rheinwaldner wrote:
Newbiepilot wrote:
In general a 1 inch increase in tire diameter increases contact area sufficiently to allow about 1,000lbs more weight to be carried while maintaining pavement loading.

Source? I cant find wheel diameter mentioned in any of the following links:
https://www.civil.iitb.ac.in/tvm/1100_L ... plain.html
http://aviationweek.com/bca/landing-ass ... arture-not
http://code7700.com/acn_v_pcn.htm
https://repository.tudelft.nl/islandora ... 53b5bac054 (chapter 10)


The tire requirements and weight limits is contained in the landing gear as well as tire and wheel interchangeability document. Anyone who has access to MyBoeingFleet can access it when looking at the maintenance documents. Many on this forum will know exactly what I am talking about.

The 777 has numerous tire options for different weights. The lighter weight versions are using 50X20 inch tires at 177PSI pressure. The 200ER uses the same diameter but increases pressure to 220PSI. The 777-300ER uses 52x21 inch tires at 227PSI.

The 787-9 is using 50X20 inch tires at 235PSI. I am not sure about the 787-10. I haven’t seen anyone credibly looking at increasing tire size or pressure and how that correlates with a possible higher MTOW.

Without posting the actual information, it is hard having a discussion with armchair landing gear design engineers who keep saying things can’t be done based on comparison and anecdote. I feel like I am having a losing battle with people who keep saying the gear is maxed out, but don’t actually have any of the facts and data to come up with the conclusion and probably have no idea what the actual tire dimensions, pressures, geometry etc is used on a plane. In my opinion for some posters, it comes down to an A vs B argument with the B critics exaggerating design constraints by saying silly things like the design is maxed out or a MTOW increase would require a new gear on the 787.

RJMAZ wrote:
Newbiepilot wrote:
I’d like to know how you came to the conclusion that the 787-10 would need a completely new gear if MTOW was increased. Do you know exactly what the pavement loading is for the 787-10? Do you know what the tire diameter and width is? Or is your opinion based on assumptions and anecdote?

Actually the 787-10 pavement loadings are all in the ACAP's. It has one of the highest pavement loadings ever.

On a rigid high strength pavement it has a pavement rating of 66. This is equal highest with the 777-300ER.

So saying a new gear is required is a fair call. I highly doubt you could increase the 787-10 MTOW by more than 5T.

Countless airports had to be upgraded to operate the 777-300ER. The 787-10 requires 777-300ER standard airports. This already limits the 787-10 to be used only at major hubs. A 5T MTOW increase would probably exceed the pVement loading limits of some major hubs.

The 787-10 already has the largest diameter and width tyres.

The A350-900 tyres are the same sized but are rated higher with more plys. This is to allow a higher tyre pressure. Higher tyre pressure reduces the contact patch on the 787-10 and actually increases pavement loading further.

There is also absolutely no way a 6 wheel bogie can fit the 787 without massive modifications. I've looked at some drawings and there is zero room. The A350-900 wheels are actually highly spaced front to rear, so the A350-1000 with three smaller tyres isn't noticeably longer. The 787-10 wheels are very closely spaced front to rear.

The only option would be maybe to increase the bogie width by a couple inches this could allow a very slightly increase.


Good points and I appreciate someone actually looking at the numbers. The 787 is not using the biggest tires in the industry as far as I know. I thought the 787 is not using the 52 inch tires that the 777-300ER has, but I haven’t seen the landing gear interchangeability data on the 787-10. The 787-9 is using 50 inch tires from what I saw. That leads me to believe that bigger tires can be studied to see if the airplane MTOW could go up. Also axle spacing may have to change as well, which is another trade study and the impact on the wheel well is another consideration. It could be a matter of inches though or we could see a 54 inch tire. All of that comes at a cost since an all new tire would be expensive and airlines may not be eager to pay for it. I still haven’t seen evidence that an all new gear is required like Mjoelnir claimed. My opinion is that it would be a modified gear. When I look at 777 interchangeability, there looks like there are about 100 parts on the gear that have different part numbers for the higher weight.

Lots of trade studies have probably already been done. My guess is the costs of a higher MTOW is not worth it, but I appreciate the technical discussion around the actual design constraints.
 
mjoelnir
Posts: 7416
Joined: Sun Feb 03, 2013 11:06 pm

Re: a MTOW increase on 787-10 to compete with A359?

Thu May 17, 2018 3:21 pm

Newbiepilot wrote:
rheinwaldner wrote:
Newbiepilot wrote:
In general a 1 inch increase in tire diameter increases contact area sufficiently to allow about 1,000lbs more weight to be carried while maintaining pavement loading.

Source? I cant find wheel diameter mentioned in any of the following links:
https://www.civil.iitb.ac.in/tvm/1100_L ... plain.html
http://aviationweek.com/bca/landing-ass ... arture-not
http://code7700.com/acn_v_pcn.htm
https://repository.tudelft.nl/islandora ... 53b5bac054 (chapter 10)


The tire requirements and weight limits is contained in the landing gear as well as tire and wheel interchangeability document. Anyone who has access to MyBoeingFleet can access it when looking at the maintenance documents. Many on this forum will know exactly what I am talking about.

The 777 has numerous tire options for different weights. The lighter weight versions are using 50X20 inch tires at 177PSI pressure. The 200ER uses the same diameter but increases pressure to 220PSI. The 777-300ER uses 52x21 inch tires at 227PSI.

The 787-9 is using 50X20 inch tires at 235PSI. I am not sure about the 787-10. I haven’t seen anyone credibly looking at increasing tire size or pressure and how that correlates with a possible higher MTOW.

Without posting the actual information, it is hard having a discussion with armchair landing gear design engineers who keep saying things can’t be done based on comparison and anecdote. I feel like I am having a losing battle with people who keep saying the gear is maxed out, but don’t actually have any of the facts and data to come up with the conclusion and probably have no idea what the actual tire dimensions, pressures, geometry etc is used on a plane. In my opinion for some posters, it comes down to an A vs B argument with the B critics exaggerating design constraints by saying silly things like the design is maxed out or a MTOW increase would require a new gear on the 787.

RJMAZ wrote:
Newbiepilot wrote:
I’d like to know how you came to the conclusion that the 787-10 would need a completely new gear if MTOW was increased. Do you know exactly what the pavement loading is for the 787-10? Do you know what the tire diameter and width is? Or is your opinion based on assumptions and anecdote?

Actually the 787-10 pavement loadings are all in the ACAP's. It has one of the highest pavement loadings ever.

On a rigid high strength pavement it has a pavement rating of 66. This is equal highest with the 777-300ER.

So saying a new gear is required is a fair call. I highly doubt you could increase the 787-10 MTOW by more than 5T.

Countless airports had to be upgraded to operate the 777-300ER. The 787-10 requires 777-300ER standard airports. This already limits the 787-10 to be used only at major hubs. A 5T MTOW increase would probably exceed the pVement loading limits of some major hubs.

The 787-10 already has the largest diameter and width tyres.

The A350-900 tyres are the same sized but are rated higher with more plys. This is to allow a higher tyre pressure. Higher tyre pressure reduces the contact patch on the 787-10 and actually increases pavement loading further.

There is also absolutely no way a 6 wheel bogie can fit the 787 without massive modifications. I've looked at some drawings and there is zero room. The A350-900 wheels are actually highly spaced front to rear, so the A350-1000 with three smaller tyres isn't noticeably longer. The 787-10 wheels are very closely spaced front to rear.

The only option would be maybe to increase the bogie width by a couple inches this could allow a very slightly increase.


Good points and I appreciate someone actually looking at the numbers. The 787 is not using the biggest tires in the industry as far as I know. I thought the 787 is not using the 52 inch tires that the 777-300ER has, but I haven’t seen the landing gear interchangeability data on the 787-10. The 787-9 is using 50 inch tires from what I saw. That leads me to believe that bigger tires can be studied to see if the airplane MTOW could go up. Also axle spacing may have to change as well, which is another trade study and the impact on the wheel well is another consideration. It could be a matter of inches though or we could see a 54 inch tire. All of that comes at a cost since an all new tire would be expensive and airlines may not be eager to pay for it. I still haven’t seen evidence that an all new gear is required like Mjoelnir claimed. My opinion is that it would be a modified gear. When I look at 777 interchangeability, there looks like there are about 100 parts on the gear that have different part numbers for the higher weight.

Lots of trade studies have probably already been done. My guess is the costs of a higher MTOW is not worth it, but I appreciate the technical discussion around the actual design constraints.


The 787-9 is using already the biggest tire on any commercial Boeing frame, that is 54x21R23 38PR, same tires as the 787-10.
The 747-8 and 777-200LR/300ER/F uses a smaller size, 52x21R22 36PR.
The 787-8 uses 50x20R22 34PR.

If we look now at the A330 that bird uses 54*21 R23 36PR for the heavier frames. Metric would be 1400x530R23 36PR I would imagine we will see 38PR on the 251t version.
The A350 uses the 1400x530R23 but now with 42PR, that is a stronger tire than both the A330 and the 787-9/10 uses.

Let us look now at the geometry of those bogies used.
787-9/10 wheel track 1520 mm, wheel base 1510mm it covers 1.520*1.510=2.3 square meter inside the contact points.
A330 wheel track 1397 mm, wheel base 1981 mm 2.8 square meter
A350 wheel track 1735 mm, wheel base 2040 mm 3.5 square meter

So you have the 787-9/10 a rather broad but short bogie, the A330 a narrow but long bogie and the A350-900 a broad and long bogie.
The contact points on the 787-8/10 cover a broad but otherwise the smallest area of those bogies.
I very much doubt that a bogie, the size of the A350-900 bogie, would fit in the wheel well of the 787.

All 3 frames use the same tire size with different ply ratings. The static tire diameter is 1400 mm. The wheel base of the 787-9/10 is only 1510mm. There are only 110 mm between the two tire surfaces. It is therefore also questionable how much a bigger tire would help the 787-9/10 once it would become available. Because you have to calculate with some tire deformation and expansion at full rotational speed.
Last edited by mjoelnir on Thu May 17, 2018 3:34 pm, edited 1 time in total.
 
User avatar
keesje
Posts: 11668
Joined: Thu Apr 12, 2001 2:08 am

Re: a MTOW increase on 787-10 to compete with A359?

Thu May 17, 2018 3:21 pm

Maybe the 787-9/10 and A321 are comparable here. Very good aircraft but your are running into significant investment if your customers want to grow with demand.
"Never mistake motion for action." Ernest Hemingway
 
rheinwaldner
Posts: 1555
Joined: Wed Jan 02, 2008 4:58 pm

Re: a MTOW increase on 787-10 to compete with A359?

Thu May 17, 2018 4:33 pm

Newbiepilot wrote:
rheinwaldner wrote:
Newbiepilot wrote:
In general a 1 inch increase in tire diameter increases contact area sufficiently to allow about 1,000lbs more weight to be carried while maintaining pavement loading.

Source? I cant find wheel diameter mentioned in any of the following links:
https://www.civil.iitb.ac.in/tvm/1100_L ... plain.html
http://aviationweek.com/bca/landing-ass ... arture-not
http://code7700.com/acn_v_pcn.htm
https://repository.tudelft.nl/islandora ... 53b5bac054 (chapter 10)


The tire requirements and weight limits is contained in the landing gear as well as tire and wheel interchangeability document.

That was not the source I asked for. You talked about maintaining pavement loading by increasing the wheel size. For that claim I asked you to provide evidence. The interchangeability document would only prove that claim, if the 772ER tires would have a diameter of 161 inches, which is nonsene of course (MTOW increase of 111000 lbs require a 111 inch wheelsize increase). So your claim requires more solid evidence, please provide it!

The example shows, that the wheel options dont differ to "maintain pavement loading". The tire parameter are simply changing for practical purposes. To minimize tire wear, brakeability and so on. Therefore IMO the interchangeability document is totally useless to judge existing pavement loading headroom and even more to provide insight, how a higher MTOW could be achieved.

Newbiepilot wrote:
Without posting the actual information, it is hard having a discussion with armchair landing gear design engineers...

Absolutely, so post the information I have asked for. If your evidence is half as comprehensive, as the sources I have provided all will be good.


Newbiepilot wrote:
Who keep saying things can’t be done based on comparison and anecdote.

And you keep saying that things can be done based one what? As far as I can see, you provided several bold assumptions without factual evidence:
- The pavement loading vs wheel diameter claim
- That the dimension of the 787 wheels can be increased at all
- Assumption that there is any causality between the tire options and pavement loading (it could be, but that is far from clear)


Newbiepilot wrote:
In my opinion for some posters, it comes down to an A vs B argument with the B critics exaggerating design constraints by saying silly things like the design is maxed out or a MTOW increase would require a new gear on the 787.

Not only that, but the 787 also has the 737 problem of not enough ground clearance. Take off performance due to lift off angle considerations must be at (or close to) the limit too.


RJMAZ wrote:
...

Good post, I agree.
Many things are difficult, all things are possible!
 
mjoelnir
Posts: 7416
Joined: Sun Feb 03, 2013 11:06 pm

Re: a MTOW increase on 787-10 to compete with A359?

Thu May 17, 2018 4:34 pm

rheinwaldner wrote:
Newbiepilot wrote:
rheinwaldner wrote:


The tire requirements and weight limits is contained in the landing gear as well as tire and wheel interchangeability document.

That was not the source I asked for. You talked about maintaining pavement loading by increasing the wheel size. For that claim I asked you to provide evidence. The interchangeability document would only prove that claim, if the 772ER tires would have a diameter of 161 inches, which is nonsene of course (MTOW increase of 111000 lbs require a 111 inch wheelsize increase). So your claim requires more solid evidence, please provide it!

The example shows, that the wheel options dont differ to "maintain pavement loading". The tire parameter are simply changing for practical purposes. To minimize tire wear, brakeability and so on. Therefore IMO the interchangeability document is totally useless to judge existing pavement loading headroom and even more to provide insight, how a higher MTOW could be achieved.

Newbiepilot wrote:
Without posting the actual information, it is hard having a discussion with armchair landing gear design engineers...

Absolutely, so post the information I have asked for. If your evidence is half as comprehensive, as the sources I have provided all will be good.


Newbiepilot wrote:
Who keep saying things can’t be done based on comparison and anecdote.

And you keep saying that things can be done based one what? As far as I can see, you provided several bold assumptions without factual evidence:
- The pavement loading vs wheel diameter claim
- That the dimension of the 787 wheels can be increased at all
- Assumption that there is any causality between the tire options and pavement loading (it could be, but that is far from clear)


Newbiepilot wrote:
In my opinion for some posters, it comes down to an A vs B argument with the B critics exaggerating design constraints by saying silly things like the design is maxed out or a MTOW increase would require a new gear on the 787.

Not only that, but the 787 also has the 737 problem of not enough ground clearance. Take off performance due to lift off angle considerations must be at (or close to) the limit too.


RJMAZ wrote:
...

Good post, I agree.


Pavement pressure is in regards to tire inflation pressure. A bigger tire carries the same weight at a lower tire pressure. That is why a bigger tyre gives you a lower pavement pressure.

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