RJMAZ
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Re: NMA/MOM/797 variant performance analysis

Thu Feb 20, 2020 1:28 pm

keesje wrote:
Then we would end up with an A300 like 8 abreast, medium range aicraft. 35-40t higher empty weight than an A321. But able to carry LD3s..

No it is smaller and much lighter than the A300. The design flipdewaf showed a 142t MTOW. 4inchs of extra cabin width will still see the MTOW remaining below 150t. That is still well below the 188t A300 and also well below the 164t A310. The wing area he gave is the same as the smaller A310.

The largest 797-7 still has less cabin area than the A300 and 80% of the area of the 787-8 or A330-800. The smaller 767-6 is around three quarters of the cabin area of the A300 and nearly two thirds of the size of the 787-8 or A330-800.

It uses LD2 containers. LD3 containers would give a huge penalty of nearly 15% greater fuselage surface area.

For 50% more seats it burns only 40% more fuel. It beats the most efficient narrowbody on the market.

The 787-8 has 20% more seats than this 797-7 but it burns 30% more fuel. Airlines always take the smaller aircraft if it has better fuel burn.
 
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keesje
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Re: NMA/MOM/797 variant performance analysis

Thu Feb 20, 2020 2:11 pm

RJMAZ wrote:
Airlines always take the smaller aircraft if it has better fuel burn.


I guess that is Boeing biggest challenge. MTOW 101t and unbeatable commonality with existing fleets, pilots & gates..

Image
"Never mistake motion for action." Ernest Hemingway
 
RJMAZ
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Re: NMA/MOM/797 variant performance analysis

Thu Feb 20, 2020 9:05 pm

keesje wrote:
RJMAZ wrote:
Airlines always take the smaller aircraft if it has better fuel burn.


I guess that is Boeing biggest challenge. MTOW 101t and unbeatable commonality with existing fleets, pilots & gates..

The A321 vs A320 actually proves why the 797 will dominate.

90+% of orders in the last few years have been for the A321. The main reason is the A321 has 5% better fuel burn per seat than the A320. The A321 has 25% more seats for 20% more fuel burn. Airlines are upgauging all the A320CEO and 737-800 routes to the larger A321NEO to save fuel.

Airlines will upgauge again to the 797 to save a massive 10% fuel per seat. All the current widebody aircraft are long haul beasts so they will not upgauge to a 787-8 for example as it burns more fuel per seat.
 
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seahawk
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Re: NMA/MOM/797 variant performance analysis

Fri Feb 21, 2020 5:08 pm

Over 50% of all NEo orders are still A320s, the A321 might achieve a 50:50 split but we are a long time away from 90% A321s.
 
marcelh
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Re: NMA/MOM/797 variant performance analysis

Sun Feb 23, 2020 11:41 am

RJMAZ wrote:
keesje wrote:
RJMAZ wrote:
Airlines always take the smaller aircraft if it has better fuel burn.


I guess that is Boeing biggest challenge. MTOW 101t and unbeatable commonality with existing fleets, pilots & gates..

The A321 vs A320 actually proves why the 797 will dominate.

90+% of orders in the last few years have been for the A321. The main reason is the A321 has 5% better fuel burn per seat than the A320. The A321 has 25% more seats for 20% more fuel burn. Airlines are upgauging all the A320CEO and 737-800 routes to the larger A321NEO to save fuel.

Airlines will upgauge again to the 797 to save a massive 10% fuel per seat. All the current widebody aircraft are long haul beasts so they will not upgauge to a 787-8 for example as it burns more fuel per seat.

You only have to always fill those seats....
 
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Stitch
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Re: NMA/MOM/797 variant performance analysis

Sun Feb 23, 2020 8:21 pm

marcelh wrote:
You only have to always fill those seats....


If trip costs are close enough, you actually always do not have to fill them. Stretches usually prove to be more popular than the baseline in large part because those extra seats come in close to "free" in terms of overall cash operating costs. As such, if you do not fill them, the penalty is low and you can usually fill them by offering low fares at close in to departure to encourage discretionary travel.
 
RJMAZ
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Re: NMA/MOM/797 variant performance analysis

Mon Feb 24, 2020 4:33 am

marcelh wrote:
You only have to always fill those seats....

Exactly. This is why the 797 widebody would capture a huge percentage of the existing widebody market.

Airlines can replace a 10 large widebodies with 15 small widebodies. We already have proof that airlines are downgauging their widebody fleets. The 797 offers higher frequency, lower capacity risk and can open new routes. We can split 90% of the intercontinetal market into the following range categories, the range is against the wind.

Atlantic rim - 4000nm
Transatlantic - 4500nm
Europe to central asia - 5000nm
Europe to east Asia - 5500nm
Pacific rim - 5500nm
Transpacific - 6500nm

The A321XLR is really limited to transatlantic, so many routes it falls short even if fitted with a premium cabin. The 797 hits a critical range point, going off the brochure spec it has 500nm greater range with 30% more passengers than the A321XLR.

The 6-7% faster cruising speed and a cross section that allows for crew rests is a huge advantage once you go beyond transatlantic.

This applies for the longer range 797 model with the shorter fuselage.

In terms of the stretched models, the 797-8 model I mentioned with sub 4000nm range is a more realistic downgauge option for Asian carriers operating 400+ seat regional A330's. You would gain a big 20+% efficiency improvement with only a 10-20% reduction in seats. That is very attracuve. Going down to the A321 would probabaly gain no efficiency over this short haul 797 model but it would reduce capacity too far. Gate and slot shortages would prevent the downgauge as there is no efficiency benefit over the 797-8.

That is two very important growing markets. Short thick routes and thin medium/long haul.
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 25, 2020 3:13 pm

RJMAZ wrote:
marcelh wrote:
You only have to always fill those seats....

Exactly. This is why the 797 widebody would capture a huge percentage of the existing widebody market.

Airlines can replace a 10 large widebodies with 15 small widebodies. We already have proof that airlines are downgauging their widebody fleets. The 797 offers higher frequency, lower capacity risk and can open new routes. We can split 90% of the intercontinetal market into the following range categories, the range is against the wind.

Atlantic rim - 4000nm
Transatlantic - 4500nm
Europe to central asia - 5000nm
Europe to east Asia - 5500nm
Pacific rim - 5500nm
Transpacific - 6500nm

The A321XLR is really limited to transatlantic, so many routes it falls short even if fitted with a premium cabin. The 797 hits a critical range point, going off the brochure spec it has 500nm greater range with 30% more passengers than the A321XLR.

The 6-7% faster cruising speed and a cross section that allows for crew rests is a huge advantage once you go beyond transatlantic.

This applies for the longer range 797 model with the shorter fuselage.

In terms of the stretched models, the 797-8 model I mentioned with sub 4000nm range is a more realistic downgauge option for Asian carriers operating 400+ seat regional A330's. You would gain a big 20+% efficiency improvement with only a 10-20% reduction in seats. That is very attracuve. Going down to the A321 would probabaly gain no efficiency over this short haul 797 model but it would reduce capacity too far. Gate and slot shortages would prevent the downgauge as there is no efficiency benefit over the 797-8.

That is two very important growing markets. Short thick routes and thin medium/long haul.


If carrying Big Cargo containers is the big reason to go 8W - why not just reuse 787 with a different wingbox/wing/fuselage length/ gear/engines. A real 787-3. It would be a lot cheaper and the bigger cross section should not be that much of a disadvantage on shorter 797 missions?

This is the only way I can see the NMA being bigger than 6W or 7W - by reusing 787 cross section - there would just not be enough volume to justify a clean sheet. Plus you could build it on the underutilized 787 lines which changes the program math considerably.

What's your assumption of 8W fuselage cross section dimensions again?
 
TFawkes
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 25, 2020 3:33 pm

Clearly Boeing should go for a 3-6-3 ovoid ultra wide body to reduce the electronics and cable length (weight) and allow 2 LD3 containers side by side to fit in the cargo hold to make the Asians happy. since the longest flights would be for 10 hours, not too many would complain about a crowded middle seat section.
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 25, 2020 3:56 pm

TFawkes wrote:
Clearly Boeing should go for a 3-6-3 ovoid ultra wide body to reduce the electronics and cable length (weight) and allow 2 LD3 containers side by side to fit in the cargo hold to make the Asians happy. since the longest flights would be for 10 hours, not too many would complain about a crowded middle seat section.


As that was most likely aimed at me I will give this discussion something else to consider on 7W vs 6W.

BTW cabling is 3-5% of the MTOW of an airliner. We are talking about a difference of less than 1% in MTOW due to a wider fuselage. It is not a big difference.

It's been bugging me why the 777X's tail has gotten so much bigger and that seems to be due to the fact that engines are farther apart so in an engine out situation you need a bigger tail to counteract the thrust of the one engine. This may be because they are planning a very long 777-10 future stretch as a mid life update when engines become more efficient.

Thinking about Fred's model - which is great - is probably making the same sort of calculations as it goes about it's merry way saying if this is bigger then that has to be bigger.

I suspect that in Fred's model the tail has to get so much bigger due to a similar issue. It is probably assuming that due to the Wider wingspan or wider fuselage the engines are farther apart, which leads to a bigger tail which leads to more weight which leads to wider wingspan, more thrust, more weight in an endless loop.

However assuming they are trying to fit a 6W or 7W into the same gates and that the same amount of Wing that can be hinged the wingspan has to be held constant. He is assuming a 41M wing on 6W that I am assuming is about the maximum that could fold down to 36M.

If you hold the distance from wingtip to wingtip the same the Engines could be in the same place (or possibly slightly narrower on 7W if the distance between engines/gear is more dependent on length of the fuselage) meaning not as big an increase in the tail size.

Effectively this would mean a shorter wing on 7W - you would need a wing with lower aspect ratio to get the same lift - offset by possibly more lift off the wider flatter body.

And of course shorter/lighter gear - especially if it is closer spaced due to the shorter fuselage length.

As I keep saying the math is complicated. Airliner design is complex and there are many tradeoff's to be made in many areas.
 
TFawkes
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 25, 2020 4:16 pm

morrisond wrote:
TFawkes wrote:
Clearly Boeing should go for a 3-6-3 ovoid ultra wide body to reduce the electronics and cable length (weight) and allow 2 LD3 containers side by side to fit in the cargo hold to make the Asians happy. since the longest flights would be for 10 hours, not too many would complain about a crowded middle seat section.


As that was most likely aimed at me I will give this discussion something else to consider on 7W vs 6W.

BTW cabling is 3-5% of the MTOW of an airliner. We are talking about a difference of less than 1% in MTOW due to a wider fuselage. It is not a big difference.

It's been bugging me why the 777X's tail has gotten so much bigger and that seems to be due to the fact that engines are farther apart so in an engine out situation you need a bigger tail to counteract the thrust of the one engine. This may be because they are planning a very long 777-10 future stretch as a mid life update when engines become more efficient.

Thinking about Fred's model - which is great - is probably making the same sort of calculations as it goes about it's merry way saying if this is bigger then that has to be bigger.

I suspect that in Fred's model the tail has to get so much bigger due to a similar issue. It is probably assuming that due to the Wider wingspan or wider fuselage the engines are farther apart, which leads to a bigger tail which leads to more weight which leads to wider wingspan, more thrust, more weight in an endless loop.

However assuming they are trying to fit a 6W or 7W into the same gates and that the same amount of Wing that can be hinged the wingspan has to be held constant. He is assuming a 41M wing on 6W that I am assuming is about the maximum that could fold down to 36M.

If you hold the distance from wingtip to wingtip the same the Engines could be in the same place (or possibly slightly narrower on 7W if the distance between engines/gear is more dependent on length of the fuselage) meaning not as big an increase in the tail size.

Effectively this would mean a shorter wing on 7W - you would need a wing with lower aspect ratio to get the same lift - offset by possibly more lift off the wider flatter body.

And of course shorter/lighter gear - especially if it is closer spaced due to the shorter fuselage length.

As I keep saying the math is complicated. Airliner design is complex and there are many tradeoff's to be made in many areas.

It's only halfway a poke-the-bear post. Every last percentage point matters.

If CFRP really is untennable for a narrowbody due to scaling requirements and minimal thickness of panels to prevent delamination (on which I call BS), then on a widebody, you can reduce wetted area by going as wide as possible, which additionally has the benefit of providing lift from the fuselage while using CFRP to minimise weight. By going as wide as possible with 17.5" wide seats, you can get incredible freight capacity on a short frame and reduce baggage loading times while also not being exorbitant on passenger space and reduced aerodynamic efficiency from an oversized fuselage. Going ovoid also reduces waste on cabin crew rest areas, which on a circular 3-6-3 fuselage would be downright lavish.

So, frame weight savings from CFRP, ground operation efficiency from cargo hold capability, minimized cable weight due to shorter fuselage, reduced landing gear weight due to shorter fuselage, less bending relief weight required, minimized tail size, and reduced thrust requirements due to the applicable previous items.

Some people will say it's an absurd short and stubby design. I say it's halfway to being a blended wing body design.
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 25, 2020 4:43 pm

TFawkes wrote:
morrisond wrote:
TFawkes wrote:
Clearly Boeing should go for a 3-6-3 ovoid ultra wide body to reduce the electronics and cable length (weight) and allow 2 LD3 containers side by side to fit in the cargo hold to make the Asians happy. since the longest flights would be for 10 hours, not too many would complain about a crowded middle seat section.


As that was most likely aimed at me I will give this discussion something else to consider on 7W vs 6W.

BTW cabling is 3-5% of the MTOW of an airliner. We are talking about a difference of less than 1% in MTOW due to a wider fuselage. It is not a big difference.

It's been bugging me why the 777X's tail has gotten so much bigger and that seems to be due to the fact that engines are farther apart so in an engine out situation you need a bigger tail to counteract the thrust of the one engine. This may be because they are planning a very long 777-10 future stretch as a mid life update when engines become more efficient.

Thinking about Fred's model - which is great - is probably making the same sort of calculations as it goes about it's merry way saying if this is bigger then that has to be bigger.

I suspect that in Fred's model the tail has to get so much bigger due to a similar issue. It is probably assuming that due to the Wider wingspan or wider fuselage the engines are farther apart, which leads to a bigger tail which leads to more weight which leads to wider wingspan, more thrust, more weight in an endless loop.

However assuming they are trying to fit a 6W or 7W into the same gates and that the same amount of Wing that can be hinged the wingspan has to be held constant. He is assuming a 41M wing on 6W that I am assuming is about the maximum that could fold down to 36M.

If you hold the distance from wingtip to wingtip the same the Engines could be in the same place (or possibly slightly narrower on 7W if the distance between engines/gear is more dependent on length of the fuselage) meaning not as big an increase in the tail size.

Effectively this would mean a shorter wing on 7W - you would need a wing with lower aspect ratio to get the same lift - offset by possibly more lift off the wider flatter body.

And of course shorter/lighter gear - especially if it is closer spaced due to the shorter fuselage length.

As I keep saying the math is complicated. Airliner design is complex and there are many tradeoff's to be made in many areas.

It's only halfway a poke-the-bear post. Every last percentage point matters.

If CFRP really is untennable for a narrowbody due to scaling requirements and minimal thickness of panels to prevent delamination (on which I call BS), then on a widebody, you can reduce wetted area by going as wide as possible, which additionally has the benefit of providing lift from the fuselage while using CFRP to minimise weight. By going as wide as possible with 17.5" wide seats, you can get incredible freight capacity on a short frame and reduce baggage loading times while also not being exorbitant on passenger space and reduced aerodynamic efficiency from an oversized fuselage. Going ovoid also reduces waste on cabin crew rest areas, which on a circular 3-6-3 fuselage would be downright lavish.

So, frame weight savings from CFRP, ground operation efficiency from cargo hold capability, minimized cable weight due to shorter fuselage, reduced landing gear weight due to shorter fuselage, less bending relief weight required, minimized tail size, and reduced thrust requirements due to the applicable previous items.

Some people will say it's an absurd short and stubby design. I say it's halfway to being a blended wing body design.


You are not wrong - it's just how small/short (in terms of capacity) can you make that so it can seat 200 Y seats (so you can use the cross section as an 737 replacement) at a reasonable 30-31" pitch without having a tailfin that is long as the wing. It may not be 12 W - but if you can make the cross section squishy enough without that much weight penalty then 8W and 9W may totally come into play.

Apparently there is a big advantage to lifting bodies or at least quasi lifting bodies - but that would require others to think outside the Circular cross section.
 
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Stitch
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 25, 2020 4:55 pm

TFawkes wrote:
Clearly Boeing should go for a 3-6-3 ovoid ultra wide body to reduce the electronics and cable length (weight) and allow 2 LD3 containers side by side to fit in the cargo hold to make the Asians happy. since the longest flights would be for 10 hours, not too many would complain about a crowded middle seat section.


Well there is always the Boeing 763-246C Concept which is 2+4+4+2...

But it was a quad, so that's out. :yuck:

Airbus looked at a double-bubble Ultra-High Capacity Aircraft study that was two A300 pressure vessels encased in a wider fuselage with a wall down the middle. That one did support four LD-3s (two per pressure vessel). I think that might have been the ASX-700 study.
 
TFawkes
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 25, 2020 6:58 pm

morrisond wrote:
TFawkes wrote:
morrisond wrote:

As that was most likely aimed at me I will give this discussion something else to consider on 7W vs 6W.

BTW cabling is 3-5% of the MTOW of an airliner. We are talking about a difference of less than 1% in MTOW due to a wider fuselage. It is not a big difference.

It's been bugging me why the 777X's tail has gotten so much bigger and that seems to be due to the fact that engines are farther apart so in an engine out situation you need a bigger tail to counteract the thrust of the one engine. This may be because they are planning a very long 777-10 future stretch as a mid life update when engines become more efficient.

Thinking about Fred's model - which is great - is probably making the same sort of calculations as it goes about it's merry way saying if this is bigger then that has to be bigger.

I suspect that in Fred's model the tail has to get so much bigger due to a similar issue. It is probably assuming that due to the Wider wingspan or wider fuselage the engines are farther apart, which leads to a bigger tail which leads to more weight which leads to wider wingspan, more thrust, more weight in an endless loop.

However assuming they are trying to fit a 6W or 7W into the same gates and that the same amount of Wing that can be hinged the wingspan has to be held constant. He is assuming a 41M wing on 6W that I am assuming is about the maximum that could fold down to 36M.

If you hold the distance from wingtip to wingtip the same the Engines could be in the same place (or possibly slightly narrower on 7W if the distance between engines/gear is more dependent on length of the fuselage) meaning not as big an increase in the tail size.

Effectively this would mean a shorter wing on 7W - you would need a wing with lower aspect ratio to get the same lift - offset by possibly more lift off the wider flatter body.

And of course shorter/lighter gear - especially if it is closer spaced due to the shorter fuselage length.

As I keep saying the math is complicated. Airliner design is complex and there are many tradeoff's to be made in many areas.

It's only halfway a poke-the-bear post. Every last percentage point matters.

If CFRP really is untennable for a narrowbody due to scaling requirements and minimal thickness of panels to prevent delamination (on which I call BS), then on a widebody, you can reduce wetted area by going as wide as possible, which additionally has the benefit of providing lift from the fuselage while using CFRP to minimise weight. By going as wide as possible with 17.5" wide seats, you can get incredible freight capacity on a short frame and reduce baggage loading times while also not being exorbitant on passenger space and reduced aerodynamic efficiency from an oversized fuselage. Going ovoid also reduces waste on cabin crew rest areas, which on a circular 3-6-3 fuselage would be downright lavish.

So, frame weight savings from CFRP, ground operation efficiency from cargo hold capability, minimized cable weight due to shorter fuselage, reduced landing gear weight due to shorter fuselage, less bending relief weight required, minimized tail size, and reduced thrust requirements due to the applicable previous items.

Some people will say it's an absurd short and stubby design. I say it's halfway to being a blended wing body design.


You are not wrong - it's just how small/short (in terms of capacity) can you make that so it can seat 200 Y seats (so you can use the cross section as an 737 replacement) at a reasonable 30-31" pitch without having a tailfin that is long as the wing. It may not be 12 W - but if you can make the cross section squishy enough without that much weight penalty then 8W and 9W may totally come into play.

Apparently there is a big advantage to lifting bodies or at least quasi lifting bodies - but that would require others to think outside the Circular cross section.

200Y as a single class? Or 200+21 for 2-class? Very different lengths.

The A321 is 44.51m long, with roughly 83% of the length usable for passenger cabin. So in 12ab config, you get 0.17*44.51 + 0.415*44.51 = 26.03835m long assuming 1:1 scaling, which is probably generous, so let's say 27m long for 200 pax in a "typical" 2-class short haul aircraft.
 
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enzo011
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 25, 2020 7:25 pm

RJMAZ wrote:
The A321 vs A320 actually proves why the 797 will dominate.

90+% of orders in the last few years have been for the A321. The main reason is the A321 has 5% better fuel burn per seat than the A320. The A321 has 25% more seats for 20% more fuel burn. Airlines are upgauging all the A320CEO and 737-800 routes to the larger A321NEO to save fuel.

Airlines will upgauge again to the 797 to save a massive 10% fuel per seat. All the current widebody aircraft are long haul beasts so they will not upgauge to a 787-8 for example as it burns more fuel per seat.



What is your definition of "last few years"?

2018 A320neo sales in total - 562
2018 A321neo sales - 155
2018 A321neo sales of total, 27%

2019 A320neo sales in total - 672
2019 A321neo sales - 476
A321neo sales of total, 70%

2020 A320neo sales so far - 207
2020 321neo sales so far - 117
2020 A321 sales of total - 56%

Maybe you meant 2017? In that year the A321neo sales made up of 45% of the total (418 of a total of 925). So I wonder where you get your 90% from and what these revised figures make for your assertion that the 797 will dominate the market?
 
TFawkes
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 25, 2020 8:00 pm

enzo011 wrote:
RJMAZ wrote:
The A321 vs A320 actually proves why the 797 will dominate.

90+% of orders in the last few years have been for the A321. The main reason is the A321 has 5% better fuel burn per seat than the A320. The A321 has 25% more seats for 20% more fuel burn. Airlines are upgauging all the A320CEO and 737-800 routes to the larger A321NEO to save fuel.

Airlines will upgauge again to the 797 to save a massive 10% fuel per seat. All the current widebody aircraft are long haul beasts so they will not upgauge to a 787-8 for example as it burns more fuel per seat.



What is your definition of "last few years"?

2018 A320neo sales in total - 562
2018 A321neo sales - 155
2018 A321neo sales of total, 27%

2019 A320neo sales in total - 672
2019 A321neo sales - 476
A321neo sales of total, 70%

2020 A320neo sales so far - 207
2020 321neo sales so far - 117
2020 A321 sales of total - 56%

Maybe you meant 2017? In that year the A321neo sales made up of 45% of the total (418 of a total of 925). So I wonder where you get your 90% from and what these revised figures make for your assertion that the 797 will dominate the market?

Just to clarify, your numbers include the LR and XLR right? If not, that could be where the 90% comes from.
 
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enzo011
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Re: NMA/MOM/797 variant performance analysis

Tue Feb 25, 2020 8:37 pm

TFawkes wrote:
enzo011 wrote:
RJMAZ wrote:
The A321 vs A320 actually proves why the 797 will dominate.

90+% of orders in the last few years have been for the A321. The main reason is the A321 has 5% better fuel burn per seat than the A320. The A321 has 25% more seats for 20% more fuel burn. Airlines are upgauging all the A320CEO and 737-800 routes to the larger A321NEO to save fuel.

Airlines will upgauge again to the 797 to save a massive 10% fuel per seat. All the current widebody aircraft are long haul beasts so they will not upgauge to a 787-8 for example as it burns more fuel per seat.



What is your definition of "last few years"?

2018 A320neo sales in total - 562
2018 A321neo sales - 155
2018 A321neo sales of total, 27%

2019 A320neo sales in total - 672
2019 A321neo sales - 476
A321neo sales of total, 70%

2020 A320neo sales so far - 207
2020 321neo sales so far - 117
2020 A321 sales of total - 56%

Maybe you meant 2017? In that year the A321neo sales made up of 45% of the total (418 of a total of 925). So I wonder where you get your 90% from and what these revised figures make for your assertion that the 797 will dominate the market?

Just to clarify, your numbers include the LR and XLR right? If not, that could be where the 90% comes from.



Numbers are from Wikipedia and seeing as the LR and XLR are A321's they are included in the numbers and are not separate. Otherwise you need to add even more numbers to the A320neo family orders per year.
 
RJMAZ
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 26, 2020 1:51 am

morrisond wrote:
If carrying Big Cargo containers is the big reason to go 8W - why not just reuse 787 with a different wingbox/wing/fuselage length/ gear/engines. A real 787-3. It would be a lot cheaper and the bigger cross section should not be that much of a disadvantage on shorter 797 missions?

The reason to use LD2 containers is simply because it packages so nicely. A perfectly circular cross section that fits a tight 8ab with 10+% lower drag and weight than the A330 cross section. The cross section will have even load distribution compared to ovoid and it will be fairly light. Rarely would the belly space get used up but it is there when needed.

The 787 cross section would result in a very short and stubby aircraft at that passenger capacity. It would limit the design to a fully optimised 787-3. To

morrisond wrote:
What's your assumption of 8W fuselage cross section dimensions again?

Here is a link to the cross section i created a couple years ago. http://members.iinet.net.au/~1300subbox/767-797.jpg

It is much more comfortable than what Flipdewaf created, but it will add a 3-5% more weight over his numbers. The 80t OEW and 150t MTOW effectively creates an aircraft 75% the size of the 787-8 but with 66% of the weight. That translates into a pure efficiency gain without even using exotic engines
 
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keesje
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Re: NMA/MOM/797 variant performance analysis

Wed Feb 26, 2020 10:45 pm

Lets all agree a big oval cross section comes with serious bending moments that would create serious OEW penalty to compensate, regardless of the miracle materials used.

And that LD3 and LD3-45 are the standards for cargo globally. You would have to offer a very convincing business case to divert from that. A business case that e.g. Boeing wasn't able to convince airlines on.

Calhoun seems aware now and reality is slowly sinking in after a decade of groupthink, that's hopeful.
"Never mistake motion for action." Ernest Hemingway
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Thu Feb 27, 2020 1:39 am

keesje wrote:
Lets all agree a big oval cross section comes with serious bending moments that would create serious OEW penalty to compensate, regardless of the miracle materials used.

And that LD3 and LD3-45 are the standards for cargo globally. You would have to offer a very convincing business case to divert from that. A business case that e.g. Boeing wasn't able to convince airlines on.

Calhoun seems aware now and reality is slowly sinking in after a decade of groupthink, that's hopeful.


How big of an Oval cross section are you talking about?

I think you are referring to 9-12W but If it's 7W Fred calculated it's only 1,000KG and that's with adding a bunch of extra weight in.

I don't think Boeing wasn't able to convince Airlines of the viability of their concept because of the size of the container. It sounds like they are just looking at a shorter less capable version but with the same cross section or possibly 6W (which of course would then be an LD3-45).

There is no reason that you couldn't put LD3-45's in a tight light 7W. But you also could take advantage of the wider width to make a new container that effectively replace the LD2 in Global fleets.

I would be surprised if a meaningful number of full containers go from one aircraft to another - and there is no reason they couldn't use an LD3-45 if they are going from an 7W to a 6W. You just make the new container the same length as the LD3-45.

If Boeing uses NMA cross section for NSA there will be plenty of frames to use the new size on.

Also not to point out the obvious but an A220 won't take an LD3-45 either.
 
RJMAZ
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Re: NMA/MOM/797 variant performance analysis

Thu Feb 27, 2020 2:08 am

keesje wrote:
And that LD3 and LD3-45 are the standards for cargo globally. You would have to offer a very convincing business case to divert from that. A business case that e.g. Boeing wasn't able to convince airlines on.

Building the aircraft for LD2 containers is by far the best option. An aircraft that fits LD2 containers can also fit LD3 containers that is why the tight 8ab is so good. The 797 design would probably max out on payload weight well before payload volume. So a single large LD3 taking up the space of two medium LD2 containers is not a problem.

Very few airlines will require the 797 to carry bulk cargo so they can simply put LD3 containers in sideways. Airlines with a big A321 fleet can also fit LD3-45 containers.

If the cargo bay is the same length of the 767-200 and 767-300 then using LD2 containers will provide 75% and 100% more cargo volume than the A321 with a single ACT. That is overkill volume consider they carry only 30-60% more passengers.

With LD3 containers there is still 40-70% more volume than an A321 with one ACT. So for passenger bags an airline can easily use LD3 containers with room to spare.

keesje wrote:
Lets all agree a oval cross section comes with serious bending moments that would create serious OEW penalty to compensate, regardless of the miracle materials used.

The cargo hold with LD2's might not be used efficiently but it is better to have wasted space and a bit of extra skin surface drag than going to a complex oval shape that pushes up empty weight.
 
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Re: NMA/MOM/797 variant performance analysis

Fri Feb 28, 2020 9:09 pm

RJMAZ wrote:


In that case the US carriers better don't throw away the 767 dedicated LD2s while they retire 767 fleets in the coming years. Put them in a barn waiting for the 797..
"Never mistake motion for action." Ernest Hemingway
 
flipdewaf
Topic Author
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Re: NMA/MOM/797 variant performance analysis

Tue Mar 03, 2020 5:06 pm

morrisond wrote:
We are talking about a difference of less than 1% in MTOW due to a wider fuselage

Yes, the increase in the fuselage weight is less than 1% of MTOW, the other weight increases however add up to a significant amount and you have negated to show those?

morrisond wrote:
It is probably assuming that due to the Wider wingspan or wider fuselage the engines are farther apart, which leads to a bigger tail which leads to more weight which leads to wider wingspan, more thrust, more weight in an endless loop.
there are many potential reasons, the optimisation may have shown that it was better to have a bigger surface rather than a heavier double articulated rudder mechanism.

morrisond wrote:
However assuming they are trying to fit a 6W or 7W into the same gates and that the same amount of Wing that can be hinged the wingspan has to be held constant. He is assuming a 41M wing on 6W that I am assuming is about the maximum that could fold down to 36M.
Incorrect, the wing geometries were held with equal AR and equal wing loading at MTOW, this dictated the wingspan.

morrisond wrote:
offset by possibly more lift off the wider flatter body.

What? Still on with the body lift. Can you show it?

morrisond wrote:
And of course shorter/lighter gear - especially if it is closer spaced due to the shorter fuselage length.
Shorter gear? Do you want me to re run the analysis compensating fort he Higher SFC due to needing lower bypass ratio for the lower gear required?

morrisond wrote:
As I keep saying the math is complicated. Airliner design is complex and there are many tradeoff's to be made in many areas.
No, the maths is not complicated. At all.

morrisond wrote:
Fred calculated it's only 1,000KG
In the fuselage, for the aircraft with the significantly wider aisle....
Wing is 1998kg heavier
Horizontal tail is 701kg heavier
Vertical tail is 369kg heavier
Fuselage is 1010kg heavier
Gear is 400kg heavier
Control weight is 668kg heavier
Hydraulics and pnue is 63kg heavier

morrisond wrote:
and that's with adding a bunch of extra weight in.

I have added no extra weight. Please redact that statement or I shall have your post reported.

morrisond wrote:
tight light 7W

Trope Much?

morrisond wrote:
is probably making the same sort of calculations as it goes about it's merry way saying if this is bigger then that has to be bigger.
No, I have explained this previously, the two compared models to which you refer and that I have done the analysis for have the horizontal tail which scale comparatively with the ratio of lengths and ratio of wing areas and the vertical tail scales with the ratio of thrust, the ratio of length and the ratio of wingspan. This assumes that a constant pressure differential (Cl) is maintained by the vertical and horizontal tail surfaces.

Like I say Morrisond please remedy the areas where you have part quoted me out of context or I will be forced to report the offending posts and have them deleted. Is that clear?

Fred
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morrisond
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Re: NMA/MOM/797 variant performance analysis

Tue Mar 03, 2020 8:08 pm

flipdewaf wrote:
morrisond wrote:
We are talking about a difference of less than 1% in MTOW due to a wider fuselage

Yes, the increase in the fuselage weight is less than 1% of MTOW, the other weight increases however add up to a significant amount and you have negated to show those?

morrisond wrote:
It is probably assuming that due to the Wider wingspan or wider fuselage the engines are farther apart, which leads to a bigger tail which leads to more weight which leads to wider wingspan, more thrust, more weight in an endless loop.
there are many potential reasons, the optimisation may have shown that it was better to have a bigger surface rather than a heavier double articulated rudder mechanism.

morrisond wrote:
However assuming they are trying to fit a 6W or 7W into the same gates and that the same amount of Wing that can be hinged the wingspan has to be held constant. He is assuming a 41M wing on 6W that I am assuming is about the maximum that could fold down to 36M.
Incorrect, the wing geometries were held with equal AR and equal wing loading at MTOW, this dictated the wingspan.

morrisond wrote:
offset by possibly more lift off the wider flatter body.

What? Still on with the body lift. Can you show it?

morrisond wrote:
And of course shorter/lighter gear - especially if it is closer spaced due to the shorter fuselage length.
Shorter gear? Do you want me to re run the analysis compensating fort he Higher SFC due to needing lower bypass ratio for the lower gear required?

morrisond wrote:
As I keep saying the math is complicated. Airliner design is complex and there are many tradeoff's to be made in many areas.
No, the maths is not complicated. At all.

morrisond wrote:
Fred calculated it's only 1,000KG
In the fuselage, for the aircraft with the significantly wider aisle....
Wing is 1998kg heavier
Horizontal tail is 701kg heavier
Vertical tail is 369kg heavier
Fuselage is 1010kg heavier
Gear is 400kg heavier
Control weight is 668kg heavier
Hydraulics and pnue is 63kg heavier

morrisond wrote:
and that's with adding a bunch of extra weight in.

I have added no extra weight. Please redact that statement or I shall have your post reported.

morrisond wrote:
tight light 7W

Trope Much?

morrisond wrote:
is probably making the same sort of calculations as it goes about it's merry way saying if this is bigger then that has to be bigger.
No, I have explained this previously, the two compared models to which you refer and that I have done the analysis for have the horizontal tail which scale comparatively with the ratio of lengths and ratio of wing areas and the vertical tail scales with the ratio of thrust, the ratio of length and the ratio of wingspan. This assumes that a constant pressure differential (Cl) is maintained by the vertical and horizontal tail surfaces.

Like I say Morrisond please remedy the areas where you have part quoted me out of context or I will be forced to report the offending posts and have them deleted. Is that clear?

Fred


Part quoting you out of context? That is all you have done in this post.

Boeing seems to really like mounting engines pretty high on the wing so the driver of gear length could be the length of the fuselage - not the Fan diameter.

If you had read my whole post about the length of the wing you will see that you might have to use a lesser AR to get the planes to fit in the same gates if the lift of the body does not offset the loss of effective wingspan.

How much lift would you get off of a flatter wider belly - no idea but I know it isn't zero - NASA seems to be able to get quite a bit of lift out of flatter belly's https://www.nasa.gov/centers/armstrong/ ... -DFRC.html

The only way to really know is if you set the 7W fuselage with the shorter cable runs (3-5% of MTOW) and possibly shorter gear and same wingspan with the engines spaced the same distance apart to the same weight and see how much the bigger tail costs in performance.

That is the question if Boeing optimizes everything for the 7W fuselage and the same sized gates. But if you don't want to do that - that's fine - please stop attacking me.

It won't be 15%.
 
flipdewaf
Topic Author
Posts: 3402
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NMA/MOM/797 variant performance analysis

Tue Mar 03, 2020 10:57 pm

morrisond wrote:
flipdewaf wrote:
morrisond wrote:
We are talking about a difference of less than 1% in MTOW due to a wider fuselage

Yes, the increase in the fuselage weight is less than 1% of MTOW, the other weight increases however add up to a significant amount and you have negated to show those?

morrisond wrote:
It is probably assuming that due to the Wider wingspan or wider fuselage the engines are farther apart, which leads to a bigger tail which leads to more weight which leads to wider wingspan, more thrust, more weight in an endless loop.
there are many potential reasons, the optimisation may have shown that it was better to have a bigger surface rather than a heavier double articulated rudder mechanism.

morrisond wrote:
However assuming they are trying to fit a 6W or 7W into the same gates and that the same amount of Wing that can be hinged the wingspan has to be held constant. He is assuming a 41M wing on 6W that I am assuming is about the maximum that could fold down to 36M.
Incorrect, the wing geometries were held with equal AR and equal wing loading at MTOW, this dictated the wingspan.

morrisond wrote:
offset by possibly more lift off the wider flatter body.

What? Still on with the body lift. Can you show it?

morrisond wrote:
And of course shorter/lighter gear - especially if it is closer spaced due to the shorter fuselage length.
Shorter gear? Do you want me to re run the analysis compensating fort he Higher SFC due to needing lower bypass ratio for the lower gear required?

morrisond wrote:
As I keep saying the math is complicated. Airliner design is complex and there are many tradeoff's to be made in many areas.
No, the maths is not complicated. At all.

morrisond wrote:
Fred calculated it's only 1,000KG
In the fuselage, for the aircraft with the significantly wider aisle....
Wing is 1998kg heavier
Horizontal tail is 701kg heavier
Vertical tail is 369kg heavier
Fuselage is 1010kg heavier
Gear is 400kg heavier
Control weight is 668kg heavier
Hydraulics and pnue is 63kg heavier

morrisond wrote:
and that's with adding a bunch of extra weight in.

I have added no extra weight. Please redact that statement or I shall have your post reported.

morrisond wrote:
tight light 7W

Trope Much?

morrisond wrote:
is probably making the same sort of calculations as it goes about it's merry way saying if this is bigger then that has to be bigger.
No, I have explained this previously, the two compared models to which you refer and that I have done the analysis for have the horizontal tail which scale comparatively with the ratio of lengths and ratio of wing areas and the vertical tail scales with the ratio of thrust, the ratio of length and the ratio of wingspan. This assumes that a constant pressure differential (Cl) is maintained by the vertical and horizontal tail surfaces.

Like I say Morrisond please remedy the areas where you have part quoted me out of context or I will be forced to report the offending posts and have them deleted. Is that clear?

Fred


Part quoting you out of context? That is all you have done in this post.


Are you going to change your statements or shall I report the posts?

morrisond wrote:
Boeing seems to really like mounting engines pretty high on the wing so the driver of gear length could be the length of the fuselage - not the Fan diameter.

At what cost? You like the benefits but not the costs...
morrisond wrote:
If you had read my whole post about the length of the wing you will see that you might have to use a lesser AR

At what cost? Higher drag? I can certainly model these scenarios. Higher drag and reduced wing mass. Should I do the same for the NB? Shall I keep span constant and adjust AR with required area?
morrisond wrote:

to get the planes to fit in the same gates if the lift of the body does not offset the loss of effective wingspan.

How much lift would you get off of a flatter wider belly - no idea but I know it isn't zero - NASA seems to be able to get quite a bit of lift out of flatter belly's https://www.nasa.gov/centers/armstrong/ ... S-011-DFRC.

Seriously? You think high Mach re-entry lifting bodies have that much relevance in this regime? Hilarious. Vortex shedding much?
morrisond wrote:


The only way to really know is if you set the 7W fuselage with the shorter cable runs

When you say shorter do you actually mean the same because a lot of these mystical cables still have to go across the fuselage too and actually across the longer heavier wings to the controls there too.
morrisond wrote:


(3-5% of MTOW) and possibly shorter gear and same wingspan

Same wingspan with higher induced drag?
morrisond wrote:
with the engines spaced the same distance apart

At a less optimal location for wing bending relief?
morrisond wrote:
to the same weight and see how much the bigger tail costs in performance.


But they aren’t the same weight..... why are you so hell bent on ignoring that?

You can run any analysis you like Morrisond, I’m not stopping you. The problem is that I’m not prepared to just make it up, if you want to make a model that isn’t based on expert learnings from trusted institutions then by all means go do it, I won’t do it.
morrisond wrote:


That is the question if Boeing optimizes everything for the 7W fuselage and the same sized gates.

Same sized gate? Longer length of folding wing or lower AR and take the hit on induced drag? Or a smaller wing and take the hit on payload/range performance. Choice is yours.
The numbers I have presented are already for an aircraft so ‘optimised’ that it has no capacity for either growth or shrink. I have explained many times why the numbers are what they are and if you don’t like them go and argue with Stamford university and the university of Bath.
morrisond wrote:
But if you don't want to do that - that's fine - please stop attacking me.

As I have mentioned numerous times before, I shan’t be modelling scenarios that are wholly unrealistic as I have had my hard work taken out of context numerous times by yourself and do not want the risk of my numbers forming the basis of bad conclusions and having my name associated with it.

morrisond wrote:

It won't be 15%.


You are right, Boeing aren’t stupid enough to make decisions like that.

Edit:I’m totally happy to run any configuration through the model/simulation. I’ll change geometries, speeds, assumed SFCs fuselage lengths, engine sizes. What I won’t do is fudge it, I have more integrity than that.

Fred



Sent from my iPhone using Tapatalk
Image
 
morrisond
Posts: 2495
Joined: Thu Jan 07, 2010 12:22 am

Re: NMA/MOM/797 variant performance analysis

Wed Mar 04, 2020 12:42 pm

flipdewaf wrote:
morrisond wrote:
flipdewaf wrote:
Yes, the increase in the fuselage weight is less than 1% of MTOW, the other weight increases however add up to a significant amount and you have negated to show those?

there are many potential reasons, the optimisation may have shown that it was better to have a bigger surface rather than a heavier double articulated rudder mechanism.

Incorrect, the wing geometries were held with equal AR and equal wing loading at MTOW, this dictated the wingspan.


What? Still on with the body lift. Can you show it?

Shorter gear? Do you want me to re run the analysis compensating fort he Higher SFC due to needing lower bypass ratio for the lower gear required?

No, the maths is not complicated. At all.

In the fuselage, for the aircraft with the significantly wider aisle....
Wing is 1998kg heavier
Horizontal tail is 701kg heavier
Vertical tail is 369kg heavier
Fuselage is 1010kg heavier
Gear is 400kg heavier
Control weight is 668kg heavier
Hydraulics and pnue is 63kg heavier


I have added no extra weight. Please redact that statement or I shall have your post reported.


Trope Much?

No, I have explained this previously, the two compared models to which you refer and that I have done the analysis for have the horizontal tail which scale comparatively with the ratio of lengths and ratio of wing areas and the vertical tail scales with the ratio of thrust, the ratio of length and the ratio of wingspan. This assumes that a constant pressure differential (Cl) is maintained by the vertical and horizontal tail surfaces.

Like I say Morrisond please remedy the areas where you have part quoted me out of context or I will be forced to report the offending posts and have them deleted. Is that clear?

Fred


Part quoting you out of context? That is all you have done in this post.


Are you going to change your statements or shall I report the posts?

morrisond wrote:
Boeing seems to really like mounting engines pretty high on the wing so the driver of gear length could be the length of the fuselage - not the Fan diameter.

At what cost? You like the benefits but not the costs...
morrisond wrote:
If you had read my whole post about the length of the wing you will see that you might have to use a lesser AR

At what cost? Higher drag? I can certainly model these scenarios. Higher drag and reduced wing mass. Should I do the same for the NB? Shall I keep span constant and adjust AR with required area?
morrisond wrote:

to get the planes to fit in the same gates if the lift of the body does not offset the loss of effective wingspan.

How much lift would you get off of a flatter wider belly - no idea but I know it isn't zero - NASA seems to be able to get quite a bit of lift out of flatter belly's https://www.nasa.gov/centers/armstrong/ ... S-011-DFRC.

Seriously? You think high Mach re-entry lifting bodies have that much relevance in this regime? Hilarious. Vortex shedding much?
morrisond wrote:


The only way to really know is if you set the 7W fuselage with the shorter cable runs

When you say shorter do you actually mean the same because a lot of these mystical cables still have to go across the fuselage too and actually across the longer heavier wings to the controls there too.
morrisond wrote:


(3-5% of MTOW) and possibly shorter gear and same wingspan

Same wingspan with higher induced drag?
morrisond wrote:
with the engines spaced the same distance apart

At a less optimal location for wing bending relief?
morrisond wrote:
to the same weight and see how much the bigger tail costs in performance.


But they aren’t the same weight..... why are you so hell bent on ignoring that?

You can run any analysis you like Morrisond, I’m not stopping you. The problem is that I’m not prepared to just make it up, if you want to make a model that isn’t based on expert learnings from trusted institutions then by all means go do it, I won’t do it.
morrisond wrote:


That is the question if Boeing optimizes everything for the 7W fuselage and the same sized gates.

Same sized gate? Longer length of folding wing or lower AR and take the hit on induced drag? Or a smaller wing and take the hit on payload/range performance. Choice is yours.
The numbers I have presented are already for an aircraft so ‘optimised’ that it has no capacity for either growth or shrink. I have explained many times why the numbers are what they are and if you don’t like them go and argue with Stamford university and the university of Bath.
morrisond wrote:
But if you don't want to do that - that's fine - please stop attacking me.

As I have mentioned numerous times before, I shan’t be modelling scenarios that are wholly unrealistic as I have had my hard work taken out of context numerous times by yourself and do not want the risk of my numbers forming the basis of bad conclusions and having my name associated with it.

morrisond wrote:

It won't be 15%.


You are right, Boeing aren’t stupid enough to make decisions like that.

Edit:I’m totally happy to run any configuration through the model/simulation. I’ll change geometries, speeds, assumed SFCs fuselage lengths, engine sizes. What I won’t do is fudge it, I have more integrity than that.

Fred



Sent from my iPhone using Tapatalk


Fred - All I'm asking for is to run one sim at same weight for Fuselage cabling and gear and with the same wingspan tip to tip. Do what you have to do to the AR and the tail.

It is conceivable with the same wingspan tip to tip and 20' shorter Fuselage length the cabling is lighter. Most of the cabling across the cabin does not exist anymore except for power in the age of Wifi.

Boeing had to lengthen the gear on the 787-10 to account for the longer fuselage. The Fan diameters are the same.

That will isolate the effect of the worse AR, bigger tail but lower wetted area on the fuselage (if the model accounts for that).

Thank you.
 
flipdewaf
Topic Author
Posts: 3402
Joined: Thu Jul 20, 2006 6:28 am

Re: NMA/MOM/797 variant performance analysis

Wed Mar 04, 2020 1:23 pm

RJMAZ wrote:
keesje wrote:
The landing weight seems higher than an A321XLR MTOW. That's translating in costs at all levels.

It is much lower costs than the thousands of other widebody aircraft. Lower costs at all levels.

The 797-7 proposed actually has better econimics per passenger than the A321.


This is the mission info for the A321NEO
Image

the 2-4-2 version has lower fuel burn per seat of ~0.5%.

Fred
Image
 
flipdewaf
Topic Author
Posts: 3402
Joined: Thu Jul 20, 2006 6:28 am

Re: NMA/MOM/797 variant performance analysis

Wed Mar 04, 2020 3:59 pm

morrisond wrote:
flipdewaf wrote:
morrisond wrote:

Part quoting you out of context? That is all you have done in this post.


Are you going to change your statements or shall I report the posts?

morrisond wrote:
Boeing seems to really like mounting engines pretty high on the wing so the driver of gear length could be the length of the fuselage - not the Fan diameter.

At what cost? You like the benefits but not the costs...
morrisond wrote:
If you had read my whole post about the length of the wing you will see that you might have to use a lesser AR

At what cost? Higher drag? I can certainly model these scenarios. Higher drag and reduced wing mass. Should I do the same for the NB? Shall I keep span constant and adjust AR with required area?
morrisond wrote:

to get the planes to fit in the same gates if the lift of the body does not offset the loss of effective wingspan.

How much lift would you get off of a flatter wider belly - no idea but I know it isn't zero - NASA seems to be able to get quite a bit of lift out of flatter belly's https://www.nasa.gov/centers/armstrong/ ... S-011-DFRC.

Seriously? You think high Mach re-entry lifting bodies have that much relevance in this regime? Hilarious. Vortex shedding much?
morrisond wrote:


The only way to really know is if you set the 7W fuselage with the shorter cable runs

When you say shorter do you actually mean the same because a lot of these mystical cables still have to go across the fuselage too and actually across the longer heavier wings to the controls there too.
morrisond wrote:


(3-5% of MTOW) and possibly shorter gear and same wingspan

Same wingspan with higher induced drag?
morrisond wrote:
with the engines spaced the same distance apart

At a less optimal location for wing bending relief?
morrisond wrote:
to the same weight and see how much the bigger tail costs in performance.


But they aren’t the same weight..... why are you so hell bent on ignoring that?

You can run any analysis you like Morrisond, I’m not stopping you. The problem is that I’m not prepared to just make it up, if you want to make a model that isn’t based on expert learnings from trusted institutions then by all means go do it, I won’t do it.
morrisond wrote:


That is the question if Boeing optimizes everything for the 7W fuselage and the same sized gates.

Same sized gate? Longer length of folding wing or lower AR and take the hit on induced drag? Or a smaller wing and take the hit on payload/range performance. Choice is yours.
The numbers I have presented are already for an aircraft so ‘optimised’ that it has no capacity for either growth or shrink. I have explained many times why the numbers are what they are and if you don’t like them go and argue with Stamford university and the university of Bath.
morrisond wrote:
But if you don't want to do that - that's fine - please stop attacking me.

As I have mentioned numerous times before, I shan’t be modelling scenarios that are wholly unrealistic as I have had my hard work taken out of context numerous times by yourself and do not want the risk of my numbers forming the basis of bad conclusions and having my name associated with it.

morrisond wrote:

It won't be 15%.


You are right, Boeing aren’t stupid enough to make decisions like that.

Edit:I’m totally happy to run any configuration through the model/simulation. I’ll change geometries, speeds, assumed SFCs fuselage lengths, engine sizes. What I won’t do is fudge it, I have more integrity than that.

Fred



Sent from my iPhone using Tapatalk


Fred - All I'm asking for is to run one sim at same weight for Fuselage

No, Even not adding any extra weight for the difficult ovid shape its heavier. Assuming the same weight for fuselage is an exercise I'm not willing to put my name to.
morrisond wrote:
cabling

The electrics have been the same weight all the way, there is no difference between the variants of the same capacity.
morrisond wrote:
and gear

even though it has to hold additional weight?
morrisond wrote:
and with the same wingspan tip to tip.
Do what you have to do to the AR and the tail.

Same wing loading and reduce the span to the 41m of the smaller variant, the weight will go down but for the time being I would leave the MTOW the same due to expectation of an increase in Fuel burn, If I find it is not needed I will reduce accordingly.
morrisond wrote:
It is conceivable with the same wingspan tip to tip and 20' shorter Fuselage length the cabling is lighter. Most of the cabling across the cabin does not exist anymore except for power in the age of Wifi.

Even if that were true, you have to remember that there are 3 sets of pax cabling running down the WB vs the NB...
morrisond wrote:


Boeing had to lengthen the gear on the 787-10 to account for the longer fuselage. The Fan diameters are the same.


morrisond wrote:

That will isolate the effect of the worse AR, bigger tail but lower wetted area on the fuselage (if the model accounts for that).

The model does account for those things but the whole point of not doing that is that you do not and can not isolate those things in reality.
morrisond wrote:
Thank you.


Image

First is as before, second is with short wing and reduced gear weight, third is with made up fuselage weight.

Fred
Image
 
morrisond
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Joined: Thu Jan 07, 2010 12:22 am

Re: NMA/MOM/797 variant performance analysis

Wed Mar 04, 2020 4:42 pm

Thank you - Do 1 and 2 have he same MTOW? Interesting that the fuel burn is basically the same. Does Number 2 have bigger AR?

So where does the extra weight come from on Number 2 vs NB? 1,000KG fuselage - Wing basically the same - 2,000KG for the tail even with the smaller wing?

I never meant reduce Fuselage weight by 1,000KG on Number 3 - I was assuming you saved enough from cabling and gear to equal it.
 
flipdewaf
Topic Author
Posts: 3402
Joined: Thu Jul 20, 2006 6:28 am

Re: NMA/MOM/797 variant performance analysis

Wed Mar 04, 2020 5:57 pm

morrisond wrote:
Thank you - Do 1 and 2 have he same MTOW?

No, 1 is 125t, 2 is 123t.
morrisond wrote:
Interesting that the fuel burn is basically the same. Does Number 2 have bigger AR?

No, it’s 41m span vs 44 for no2.

morrisond wrote:
So where does the extra weight come from on Number 2 vs NB?

Bigger wing, heavier more powerful engines, higher tail surfaces, bigger control surfaces, more pneumatic system required, more fuel to be lifted.

morrisond wrote:
1,000KG fuselage - Wing basically the same

Wing is bigger, remember we are dealing with planes and a key requirement is that they can actually fly.

morrisond wrote:
- 2,000KG for the tail even with the smaller wing?

The wing is the key driver for losing 2000kg. Just so happens that this also increases the induced drag. The wing is barely smaller than the previous offering just lower span. Hence higher AR

morrisond wrote:
I never meant reduce Fuselage weight by 1,000KG on Number 3 - I was assuming you saved enough from cabling and gear to equal it.

1. There is nothing you are saving from cabling. Having a shorter fuselage assumes you are routing it all longitudinally when you aren’t. How do you think stuff is getting from the left side to the right side and vice verse?
2. The gear is already heavier as well as the fuselage compared to the NB, the Savings associated from the gear weight are making up for the increased gear weight and not the fuselage.

It appears you are assuming wrong.

Fred



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morrisond
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Re: NMA/MOM/797 variant performance analysis

Wed Mar 04, 2020 6:22 pm

Hi Fred,

Just so we are on the same page - Number 2 has same wingtip to wingtip span as the NB at 41m. But due to the wider fuselage the chord is less or are you making the chord larger to get the same area?

And what is the MTOW of the NB?

Thanks
 
flipdewaf
Topic Author
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Re: NMA/MOM/797 variant performance analysis

Wed Mar 04, 2020 7:04 pm

morrisond wrote:
Hi Fred,

Just so we are on the same page - Number 2 has same wingtip to wingtip span as the NB at 41m. But due to the wider fuselage the chord is less or are you making the chord larger to get the same area?

And what is the MTOW of the NB?

Thanks

The wing span (tip to tip) is the same in both cases but because the WB requires a higher TOW it has a higher area and so a lower AR (bigger chord).

MTOW of NB is 115t

Fred


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morrisond
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Re: NMA/MOM/797 variant performance analysis

Thu Mar 05, 2020 12:20 pm

Thanks Fred.

So how come between #2 and #3 when the Fuselage/ Gear Cabling weight is artificially reduced by 1,000 kg DOW only drops by 1,000KG as well?

Should there not be knock on effects and lesser weight in the wing (due to less area) - lower thrust (lighter engines) and smaller lighter tail?
 
flipdewaf
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NMA/MOM/797 variant performance analysis

Thu Mar 05, 2020 1:49 pm

morrisond wrote:
Thanks Fred.

So how come between #2 and #3 when the Fuselage/ Gear Cabling weight is artificially reduced by 1,000 kg DOW only drops by 1,000KG as well?

Should there not be knock on effects and lesser weight in the wing (due to less area) - lower thrust (lighter engines) and smaller lighter tail?


Because the reduction in wing area creates an increase in wing weight under those circumstances :crazy: .

Because we are holding the span constant rather than the AR when the wing area is reduced the cord is then reduced and so the thickness drops (holding t/c at 0.1) the thinner wing then actually gets heavier and cancels out the weight gains you would otherwise expect (flicking between the breakdown of the numbers that appears to be what it is showing). I do not move the predetermined weight figures (MTOW and MZFW) By anything other than 1t increments as at some point we need to know when to stop. The MZFW I have been using for this is Empty weight + Payload (payload = 300pax *100kg. I then round up to the nearest 1000kg.

Edit: I have noticed some areas to change and potentially optimise, when my computer restarts I will have a look.

Fred
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morrisond
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Re: NMA/MOM/797 variant performance analysis

Thu Mar 05, 2020 2:44 pm

flipdewaf wrote:
morrisond wrote:
Thanks Fred.

So how come between #2 and #3 when the Fuselage/ Gear Cabling weight is artificially reduced by 1,000 kg DOW only drops by 1,000KG as well?

Should there not be knock on effects and lesser weight in the wing (due to less area) - lower thrust (lighter engines) and smaller lighter tail?


Because the reduction in wing area creates an increase in wing weight under those circumstances :crazy: .

Because we are holding the span constant rather than the AR when the wing area is reduced the cord is then reduced and so the thickness drops (holding t/c at 0.1) the thinner wing then actually gets heavier and cancels out the weight gains you would otherwise expect (flicking between the breakdown of the numbers that appears to be what it is showing). I do not move the predetermined weight figures (MTOW and MZFW) By anything other than 1t increments as at some point we need to know when to stop. The MZFW I have been using for this is Empty weight + Payload (payload = 300pax *100kg. I then round up to the nearest 1000kg.

Edit: I have noticed some areas to change and potentially optimise, when my computer restarts I will have a look.

Fred


Thanks - it sounds like it would be a fun model to play with.

I really do appreciate it.
 
flipdewaf
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Re: NMA/MOM/797 variant performance analysis

Thu Mar 05, 2020 4:15 pm

Image

Final data was pretty much the same.

Weight estimation came out with the following.
Image
The weights were as calculated but with lower landing gear weight as of the NB version and with 1t taken out of the final figure to represent the 1t reduction in fuselage.

Yes, the model is incredibly fun. The main reason it is fun is because from a fundamental level I understand each of the specific parts and what can drive something in isolation, I also understand the tradeoffs but whaty makes it very interesting to do is the small interplay between things that are very counter intuitive but actually when you dig in to make complete sense, I dont think it sis something that is possible to understand how the play between things work completely at an intuitive level, it's too networked. Why I made the model really.

Fred
Image
 
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keesje
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Re: NMA/MOM/797 variant performance analysis

Fri Mar 06, 2020 4:41 pm

flipdewaf wrote:
morrisond wrote:
Thank you - Do 1 and 2 have he same MTOW?

No, 1 is 125t, 2 is 123t.
morrisond wrote:
Interesting that the fuel burn is basically the same. Does Number 2 have bigger AR?

No, it’s 41m span vs 44 for no2.

morrisond wrote:
So where does the extra weight come from on Number 2 vs NB?

Bigger wing, heavier more powerful engines, higher tail surfaces, bigger control surfaces, more pneumatic system required, more fuel to be lifted.

morrisond wrote:
1,000KG fuselage - Wing basically the same

Wing is bigger, remember we are dealing with planes and a key requirement is that they can actually fly.

morrisond wrote:
- 2,000KG for the tail even with the smaller wing?

The wing is the key driver for losing 2000kg. Just so happens that this also increases the induced drag. The wing is barely smaller than the previous offering just lower span. Hence higher AR

morrisond wrote:
I never meant reduce Fuselage weight by 1,000KG on Number 3 - I was assuming you saved enough from cabling and gear to equal it.

1. There is nothing you are saving from cabling. Having a shorter fuselage assumes you are routing it all longitudinally when you aren’t. How do you think stuff is getting from the left side to the right side and vice verse?
2. The gear is already heavier as well as the fuselage compared to the NB, the Savings associated from the gear weight are making up for the increased gear weight and not the fuselage.

It appears you are assuming wrong.

Fred

Sent from my iPhone using Tapatalk


Intersetingly when you start from a blank sheet of paper, you can optimize around a carefully carved out specification.

If you can't and have to compromise on every aspect, still a modified oldy can be a hard to beat obstacle, because of it's superior time to market, cost, low risk levels, MRO and cockpit commonality.

Image
"Never mistake motion for action." Ernest Hemingway
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Sat Mar 07, 2020 11:09 am

flipdewaf wrote:
Image

Final data was pretty much the same.

Weight estimation came out with the following.
Image
The weights were as calculated but with lower landing gear weight as of the NB version and with 1t taken out of the final figure to represent the 1t reduction in fuselage.

Yes, the model is incredibly fun. The main reason it is fun is because from a fundamental level I understand each of the specific parts and what can drive something in isolation, I also understand the tradeoffs but whaty makes it very interesting to do is the small interplay between things that are very counter intuitive but actually when you dig in to make complete sense, I dont think it sis something that is possible to understand how the play between things work completely at an intuitive level, it's too networked. Why I made the model really.

Fred


Hi Fred,

Sorry I have been really busy with my Son's robotics team and the competitions have started so really busy.

Can you post the same weight numbers for the narrow body?
 
flipdewaf
Topic Author
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Re: NMA/MOM/797 variant performance analysis

Sat Mar 07, 2020 12:00 pm

morrisond wrote:
flipdewaf wrote:
Image

Final data was pretty much the same.

Weight estimation came out with the following.
Image
The weights were as calculated but with lower landing gear weight as of the NB version and with 1t taken out of the final figure to represent the 1t reduction in fuselage.

Yes, the model is incredibly fun. The main reason it is fun is because from a fundamental level I understand each of the specific parts and what can drive something in isolation, I also understand the tradeoffs but whaty makes it very interesting to do is the small interplay between things that are very counter intuitive but actually when you dig in to make complete sense, I dont think it sis something that is possible to understand how the play between things work completely at an intuitive level, it's too networked. Why I made the model really.

Fred


Hi Fred,

Sorry I have been really busy with my Son's robotics team and the competitions have started so really busy.

Can you post the same weight numbers for the narrow body?

I can do but likely not till Monday. Like you weekend is family time and I only turn laptop on after 22:00 on a Sunday.

Fred


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Image
 
strfyr51
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Re: NMA/MOM/797 variant performance analysis

Mon Mar 09, 2020 1:05 am

oschkosch wrote:
Nma will never be 7W, absolutely no point in doing so.

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Since that would depend on the Airline? who KNOWS what the point might be?
 
strfyr51
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Re: NMA/MOM/797 variant performance analysis

Mon Mar 09, 2020 1:26 am

TFawkes wrote:
Clearly Boeing should go for a 3-6-3 ovoid ultra wide body to reduce the electronics and cable length (weight) and allow 2 LD3 containers side by side to fit in the cargo hold to make the Asians happy. since the longest flights would be for 10 hours, not too many would complain about a crowded middle seat section.

while I don't doubt that some airline would fo a 3-6-3 main cabin? I could see a 3-4-3 Main cabin much like the 767. and? Since the LD2 containers are already available?there might be a savings in using them along with the 767 cargo loading system.
 
flipdewaf
Topic Author
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Re: NMA/MOM/797 variant performance analysis

Mon Mar 09, 2020 1:36 pm

strfyr51 wrote:
oschkosch wrote:
Nma will never be 7W, absolutely no point in doing so.

Gesendet von meinem SM-G950F mit Tapatalk

Since that would depend on the Airline? who KNOWS what the point might be?


Well I imagine that the what was being referred to was the sizing to fit 7W in a 2-3-2 type layout with standard sized economy seating. In that scenario whilst possible to go with something else (2-2-2) it is very unlikely that an airline will choose anything other that the 2-3-2 for the economy cabin. To all intents and purposes it would be the design dictating the layout available for economy.

morrisond wrote:
Can you post the same weight numbers for the narrow body?


Image

Fred
Image
 
morrisond
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Re: NMA/MOM/797 variant performance analysis

Sun Mar 15, 2020 12:38 pm

flipdewaf wrote:
strfyr51 wrote:
oschkosch wrote:
Nma will never be 7W, absolutely no point in doing so.

Gesendet von meinem SM-G950F mit Tapatalk

Since that would depend on the Airline? who KNOWS what the point might be?


Well I imagine that the what was being referred to was the sizing to fit 7W in a 2-3-2 type layout with standard sized economy seating. In that scenario whilst possible to go with something else (2-2-2) it is very unlikely that an airline will choose anything other that the 2-3-2 for the economy cabin. To all intents and purposes it would be the design dictating the layout available for economy.

morrisond wrote:
Can you post the same weight numbers for the narrow body?


Image

Fred


Hi Fred - Sorry I have been really busy. No worries if the following takes a while - I hope all is well with you and your family in these times.

What happens to the NB tail weight (Horizontal, Vertical and control weight) if you keep the MTOW/wingspan/thrust the same as existing and chop 20' from the fuselage? Capability would be way up - I know - just curious if the weight grows the same as the WB.

Thanks
 
Sokes
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Re: NMA/MOM/797 variant performance analysis

Tue Mar 17, 2020 8:58 am

seahawk wrote:
...Imagine a rubber balloon with the floor as a fixed (round) structure inside it. When pressurised it would aim to become a circle with the diameter the same as the diameter of the round floor inside the balloon. A fuselage of a plane does not act differently.


I know cabin width at shoulder height matters. Just for thought experiment: Suppose one takes a circular fuselage (not double bubble) and places the floor exactly in the middle. One would have to increase diameter or loose one seat, but in exchange one would get greatly increased cargo capacity.
How much weight would that shave of the fuselage?
Why can't the world be a little bit more autistic?
 
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keesje
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Re: NMA/MOM/797 variant performance analysis

Mon Mar 23, 2020 7:56 pm

A MTOW of 115t, OEW of 60-65t sounds like credible weights for a NB larger, more capable (5000NM) than A321XLR.

New PW1000/LEAP version sporting 86-90 inch fans, composites seagull wing to support those.
https://d1a2ot8agkqe8w.cloudfront.net/w ... _77645.jpg

The large single aisle cross section to creddibly handle up to 45 rows.

An NMA concept airlines probably would have pulled their check books for, a few years ago.
"Never mistake motion for action." Ernest Hemingway
 
744SPX
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Re: NMA/MOM/797 variant performance analysis

Tue Mar 24, 2020 10:07 pm

Keesje,
Doesn't a seagull wing give up a certain amount of lift/efficiency compared to a relatively straight (near the wing root) design? Especially as the gull portion being at the root comprises a significant portion of the total wing area? (I don't know the answer, just asking)

This is where I think an A322 with a wing-root extension or new composite wing (also of greater area) would only require a PW1000/LEAP of perhaps 83 inches as required thrust might only be 38K or so as the greater wing area will compensate for the greater MTOW. I think such a design could possibly do 20 tons to 4500nmi with no gull wing required...

Beyond that, I think the Truss Braced Wing is clearly the way ahead for not only better airframe efficiency but no real limits on fan/open rotor size...
 
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keesje
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Re: NMA/MOM/797 variant performance analysis

Tue Mar 24, 2020 11:13 pm

744SPX, I think aerodynamically an uninterrupted high wing is optimal in combination with high BPR engines. But not operationally (engine check/ maintenance) and for landing gear efficiently. You either end up with a long heavy one (Q400) or fuselage fairings (ATR) and limited stretch options /rotation angles.

That is why lower wings are mostly preferred. A seagull could keep landing gear efficiency while allowing for higher BPR engines. At the costs of some aerodynamic efficiency.
"Never mistake motion for action." Ernest Hemingway
 
strfyr51
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Re: NMA/MOM/797 variant performance analysis

Wed Mar 25, 2020 2:02 am

keesje wrote:
744SPX, I think aerodynamically an uninterrupted high wing is optimal in combination with high BPR engines. But not operationally (engine check/ maintenance) and for landing gear efficiently. You either end up with a long heavy one (Q400) or fuselage fairings (ATR) and limited stretch options /rotation angles.

That is why lower wings are mostly preferred. A seagull could keep landing gear efficiency while allowing for higher BPR engines. At the costs of some aerodynamic efficiency.

while I would not doubt the Gull wing because Boeing cannot again build another short landing gear aircraft In the 737 model type and the 757-767 model types could allow for an extended fan diameter If they intend to move to fewer and wider Fan blades. So the fuselage is not as important to dual aisle or single aisle width except as the length of the Fuselage is concerned. The 757-300 fuselage is about as long a Single aisle fuselage as is practical, so to get the pax count? the 767-400 might be as long as is practical for regional operations as the airplane might well have to fit into existing hangar bays and Existing Airport gates especially if you're looking at the 777X's folding wing tips to allow regular WB gate parking. so? It might very well be the double aisle design with 3-3-3, or 2-4-2 in main Cabin seating. At least? That would be my bet.
 
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keesje
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Re: NMA/MOM/797 variant performance analysis

Fri Mar 27, 2020 11:17 am

strfyr51 wrote:
keesje wrote:
744SPX, I think aerodynamically an uninterrupted high wing is optimal in combination with high BPR engines. But not operationally (engine check/ maintenance) and for landing gear efficiently. You either end up with a long heavy one (Q400) or fuselage fairings (ATR) and limited stretch options /rotation angles.

That is why lower wings are mostly preferred. A seagull could keep landing gear efficiency while allowing for higher BPR engines. At the costs of some aerodynamic efficiency.

while I would not doubt the Gull wing because Boeing cannot again build another short landing gear aircraft In the 737 model type and the 757-767 model types could allow for an extended fan diameter If they intend to move to fewer and wider Fan blades. So the fuselage is not as important to dual aisle or single aisle width except as the length of the Fuselage is concerned. The 757-300 fuselage is about as long a Single aisle fuselage as is practical, so to get the pax count? the 767-400 might be as long as is practical for regional operations as the airplane might well have to fit into existing hangar bays and Existing Airport gates especially if you're looking at the 777X's folding wing tips to allow regular WB gate parking. so? It might very well be the double aisle design with 3-3-3, or 2-4-2 in main Cabin seating. At least? That would be my bet.


Embraer had to same situation, wanting to benefit from the high BPR Pratt GTF's they redesined the wing, using a seagull configuration.
A radical, expensive modification from the E190 E1. https://www.aerotime.aero/upload/files/ ... t_view.jpg

Image
Source: https://www.flickr.com/photos/ramonkok/

I expect Boeing to go down the same road with a new FSA single aisle configuration.
Besting the 80 inch A321 fans with turbofan approaching 88-90 inch, for ~45-50k lbs thrust.
Pratt was already sharing plans for BPR growth options years ago.
"Never mistake motion for action." Ernest Hemingway
 
flipdewaf
Topic Author
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Re: NMA/MOM/797 variant performance analysis

Fri Mar 27, 2020 11:33 am

keesje wrote:
strfyr51 wrote:
keesje wrote:
744SPX, I think aerodynamically an uninterrupted high wing is optimal in combination with high BPR engines. But not operationally (engine check/ maintenance) and for landing gear efficiently. You either end up with a long heavy one (Q400) or fuselage fairings (ATR) and limited stretch options /rotation angles.

That is why lower wings are mostly preferred. A seagull could keep landing gear efficiency while allowing for higher BPR engines. At the costs of some aerodynamic efficiency.

while I would not doubt the Gull wing because Boeing cannot again build another short landing gear aircraft In the 737 model type and the 757-767 model types could allow for an extended fan diameter If they intend to move to fewer and wider Fan blades. So the fuselage is not as important to dual aisle or single aisle width except as the length of the Fuselage is concerned. The 757-300 fuselage is about as long a Single aisle fuselage as is practical, so to get the pax count? the 767-400 might be as long as is practical for regional operations as the airplane might well have to fit into existing hangar bays and Existing Airport gates especially if you're looking at the 777X's folding wing tips to allow regular WB gate parking. so? It might very well be the double aisle design with 3-3-3, or 2-4-2 in main Cabin seating. At least? That would be my bet.


Embraer had to same situation, wanting to benefit from the high BPR Pratt GTF's they redesined the wing, using a seagull configuration.
A radical, expensive modification from the E190 E1. https://www.aerotime.aero/upload/files/ ... t_view.jpg

Image
Source: https://www.flickr.com/photos/ramonkok/

I remember when the T7 first came out and there was piece in a magazine (I was 9) showing how the Ge90 was as big as the fuselage of a 737, I wonder when we will see the first jet engine with a higher diameter than the fuselage of the plane it is powering...

Fred

I expect Boeing to go down the same road with a new FSA single aisle configuration.
Besting the 80 inch A321 fans with turbofan approaching 88-90 inch, for ~45-50k lbs thrust.
Pratt was already sharing plans for BPR growth options years ago.
Image

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