History imho teaches us only one thing, which seems to indicate that over 5000nm effective range is a positive factor for sales, which is shown by the ER versions selling better on the 767 and the A332 and A333 balance before and after the A333 reached this range.

For the rest I am much more careful. Sure there are plenty 767s still flying, but imho it does only mean that so far retiring the 767 early and buying a new replacement was not seen as efficient, it does not mean that airlines are wanting a 767 replacement.

seahawk wrote:

History imho teaches us only one thing, which seems to indicate that over 5000nm effective range is a positive factor for sales, which is shown by the ER versions selling better on the 767 and the A332 and A333 balance before and after the A333 reached this range.

For the rest I am much more careful. Sure there are plenty 767s still flying, but imho it does only mean that so far retiring the 767 early and buying a new replacement was not seen as efficient, it does not mean that airlines are wanting a 767 replacement.

I am not sure history tells is that over 5000 miles range is a positive factor. With the exception of newer quads like the A340 and A380, every widebody built was launched with the most powerful engines available (747, DC10, L1011, A300, 767, A330, MD-11 and 777) until the 787 was launched. When airplanes are launched with the most powerful engines available, subsequent thrust increases with newer engines increase capability with a relatively low impact on OEW.

The newer widebodies are not like that. They are optimized around engines designed specifically for them. The 787 and A350 are not built wit 10% extra capability once a new engine derivative comes out. This helps efficiency and keep the OEW down. A new plane can be optimized from the start.

To make this a more useful debate on the mom I have made these charts to show where I believe the middle of the market is.
They represent cabin area of current airliners, the first with the 757 and 767 variants included

This is without the 757 and 767 variants to see where the gap is without them.

I believe this shows the perceived gap that is trying to be filled by these MOM offerings/ideas without the muddying effects of seat counts and premium cabins etc.
This shows a scatter plot of cabin area Vs range (the 757 and 767 models are highlighted in red (seems I have left the 767-400 off)) This again shows the gap from a range perspective, I see this gap at around 5000nm but I think there is more to read in to this in that a widebody airliner has a lot of capacity spare for cargo and so the marketing ranges that I have used are out by a larger factor for the widebodies than they are for the narrow bodies. I think the modern push for veryhigh range is more of a marketing spin that is derived from the fact that MZFW range goes up a bit and as engines become more efficient the slopes of payload range curves drops giving the benefit of huge marketing ranges that might be useful to some airlines but really not many.
It also shows that the 757 is no special case, it sits squarely with the narrowbodies. If anything the 767 is the special case.


This last chart shows the cabin area vs How many seats abreast the cabin is, i have put the 77L and 77W as 9.5 abreast as it is on the cusp of 9 and 10. Again the 767 is the one that sticks out here.


I then took a cabin width of 175m^2 and used a 6 abreast width and 7 abreast 2 aisle widths based on 20"seats and 20" aisles with 10 inch total wall width. I then calculated the cabin length based on these dimensions. To get the total length of the fuselage I added 3.5x the fuselage width (1.5x for nose + 2x for tail taper). to give me a single aisle length of 59m and a twin aisle length of 53m. I then used this to plug in to my weight estimation tool which gave me a fuselage structure weight of 10610kg for the narrow and 14256kg for the wide body.

My thoughts on that are on a weight perspective is that its a no brainer but I think there is a significant issue with rotation angle but it would have to be seen what size a ~2025 40klb thrust engine is, my guess is not small.

Fred

Interesting charts and I think nobody has ever disputed that there is a gap. The question is, if there is a market. 757 and 767 sold when the best option below was the 737-400, MD-80, 707 or 727 and above you had the DC-10, Tristar and 747. Once A321-200 and 737-900 came on, sales of the 757 dropped and once the A330 came on sales of the 767 dropped. (just like they did for A300/A310)

The I would not dispute the need for something a bit larger than the A321 and maybe something a bit less heavy than the A332/338/788 but the question imho is, if the size in between might be the three seat car. For which you could draw all the same diagrams and find the same "gap" in the car market.

seahawk wrote:

Interesting charts and I think nobody has ever disputed that there is a gap. The question is, if there is a market. 757 and 767 sold when the best option below was the 737-400, MD-80, 707 or 727 and above you had the DC-10, Tristar and 747. Once A321-200 and 737-900 came on, sales of the 757 dropped and once the A330 came on sales of the 767 dropped. (just like they did for A300/A310)

The I would not dispute the need for something a bit larger than the A321 and maybe something a bit less heavy than the A332/338/788 but the question imho is, if the size in between might be the three seat car. For which you could draw all the same diagrams and find the same "gap" in the car market.

I totally agree, the sweet spot in the market doesn't marry up with a sweet spot in the engineering, I think the 767 sitting there in the charts by itself says a lot.

Fred

Polot wrote:

Amiga500 wrote:

767333ER wrote:

Well it outsold and killed off its 2-4-2 and LD3 capable competitors, the A300 and A310.

The A330/A340 fuselage is "identical" to the A300/310. You not including those in your figures?

The A330/A340 are completely different beasts than the 767/A300/A310. They share the same fuselage as the A300/A310 but little else...so kind of hard to use them when talking about the feasibility of the 767 fuselage/7 abreast in the MoM. That is like saying the 737/A320 fuselage is perfect for a ~100 seat market while the C series's fuselage sucks for it because look at all those 738s/739s/A320s/A321s.

Thank you Polot, that's what I was trying to get at. The A330/340 slightly resemble the A300, share the same fuselage for good or bad, but they are quite different and the A330 is far more competitive than the A300 and far better utilizes the wider cross section than the A300 did. The A340 obviously is not very competitive anymore.

@ 767333ER & Polot

My point is fairly straightforward - using the 767 (all variants) sales vs. the A300/A310 sales as a means to compare 7-abreast vs. 8-abreast is misleading bordering on foolish. The capabilities of the airframes are significantly different addressing different sections of the market outside of this supposed "MoM".

-----------------------------------

Regarding the earlier point about reducing the fuselage diameter - see image below.

There is some fat could be cut away - incorporating side rollers (mounted between the ribs) to guide the LD3 via their sloped lower surface would help reduce the gap required to run them along the fuselage. But I'd reckon your looking at around 10-15 cm. Beyond that it gets difficult - moving the fuselage toward a taller ovoid would help further - but your then fighting hoop stress concentrations to keep weight equivalent.

Amiga500 wrote:

Regarding the earlier point about reducing the fuselage diameter - see image below.

There is some fat could be cut away - incorporating side rollers (mounted between the ribs) to guide the LD3 via their sloped lower surface would help reduce the gap required to run them along the fuselage. But I'd reckon your looking at around 10-15 cm. Beyond that it gets difficult - moving the fuselage toward a taller ovoid would help further - but your then fighting hoop stress concentrations to keep weight equivalent

Thanks for pointing that out. On top of the gains of the bottom half, we can further look at the passenger section. Below is a list of the difference between cabin and fuselage width of several modern widebodies. It's based on wikipedia and I'm not sure if it's all with equal definition, but here goes:

A330 46cm
A330neo 38cm
777 36cm
A350XWB 35cm
787 28cm
777x 24cm

If we try to avoid all the possible uncertainties of basing too much conclusions on the above list and we just subtract a 18-inch seat width from the A350XWB 5,96m fuselage width you end up at the mentioned 5,50m. Much smaller and you loose LD3 capability, comfort as A330 replacement and flexibility to use wider aisles with narrower seats for boarding speed in MoM form.

14cm difference you wouldn't normally design a completely new fuselage for. However with 2025 SFC gains the A330 structures will have become even more excessive than they are already are in their current neo form. It will be time for a new design and with that they can probably gain a few centimetres in fuselage efficiency.

flipdewaf wrote:

To make this a more useful debate on the mom I have made these charts to show where I believe the middle of the market is.
They represent cabin area of current airliners, the first with the 757 and 767 variants included

This is without the 757 and 767 variants to see where the gap is without them.

I believe this shows the perceived gap that is trying to be filled by these MOM offerings/ideas without the muddying effects of seat counts and premium cabins etc.
This shows a scatter plot of cabin area Vs range (the 757 and 767 models are highlighted in red (seems I have left the 767-400 off)) This again shows the gap from a range perspective, I see this gap at around 5000nm but I think there is more to read in to this in that a widebody airliner has a lot of capacity spare for cargo and so the marketing ranges that I have used are out by a larger factor for the widebodies than they are for the narrow bodies. I think the modern push for veryhigh range is more of a marketing spin that is derived from the fact that MZFW range goes up a bit and as engines become more efficient the slopes of payload range curves drops giving the benefit of huge marketing ranges that might be useful to some airlines but really not many.
It also shows that the 757 is no special case, it sits squarely with the narrowbodies. If anything the 767 is the special case.


This last chart shows the cabin area vs How many seats abreast the cabin is, i have put the 77L and 77W as 9.5 abreast as it is on the cusp of 9 and 10. Again the 767 is the one that sticks out here.


I then took a cabin width of 175m^2 and used a 6 abreast width and 7 abreast 2 aisle widths based on 20"seats and 20" aisles with 10 inch total wall width. I then calculated the cabin length based on these dimensions. To get the total length of the fuselage I added 3.5x the fuselage width (1.5x for nose + 2x for tail taper). to give me a single aisle length of 59m and a twin aisle length of 53m. I then used this to plug in to my weight estimation tool which gave me a fuselage structure weight of 10610kg for the narrow and 14256kg for the wide body.

My thoughts on that are on a weight perspective is that its a no brainer but I think there is a significant issue with rotation angle but it would have to be seen what size a ~2025 40klb thrust engine is, my guess is not small.

Fred

Nice graphs!

I think the fuselage weights differences between a widebody and narrowbody tell a lot. Even with all your assumptions, it's what we see in the 757 vs 762 weight differences.

The "significant issue with rotation angle" I don't see. Many aircraft are 60, 70 or even 80m long. Of course it would need long legs, but not exceptionally long.


DC8-73

When you make relatively narrow bodies very long (DC8-73, 757-300, MD90, A340-600) compared to their cross sections, you increasingly start to pay a price

- in terms of required weight/structure to provide strenght and stiffness to the aircraft, diluting overall economics/ structural efficiency.
- passenger / crew movement in the cabin start to be an issue during ground as well as inflight operations.
- perceived comfort of small seats/cabin starts to play at long stretches.
- so far composites prove less useful on narrowbody fusealges. E.g. impact (hail, ground) starts to overrule longitudinal load requirements in determining skin thickness.

Adding cross section (30 inch versus the 54m 757-300) keeping it a efficient narrowbody but removing/reducing some of the above constrains, opens new opportunities.
As Newbiepilot says, keeping everything else equal, fuselage weight is only a limited percentage of the aircraft.

keesje wrote:

flipdewaf wrote:

To make this a more useful debate on the mom I have made these charts to show where I believe the middle of the market is.
They represent cabin area of current airliners, the first with the 757 and 767 variants included

This is without the 757 and 767 variants to see where the gap is without them.

I believe this shows the perceived gap that is trying to be filled by these MOM offerings/ideas without the muddying effects of seat counts and premium cabins etc.
This shows a scatter plot of cabin area Vs range (the 757 and 767 models are highlighted in red (seems I have left the 767-400 off)) This again shows the gap from a range perspective, I see this gap at around 5000nm but I think there is more to read in to this in that a widebody airliner has a lot of capacity spare for cargo and so the marketing ranges that I have used are out by a larger factor for the widebodies than they are for the narrow bodies. I think the modern push for veryhigh range is more of a marketing spin that is derived from the fact that MZFW range goes up a bit and as engines become more efficient the slopes of payload range curves drops giving the benefit of huge marketing ranges that might be useful to some airlines but really not many.
It also shows that the 757 is no special case, it sits squarely with the narrowbodies. If anything the 767 is the special case.


This last chart shows the cabin area vs How many seats abreast the cabin is, i have put the 77L and 77W as 9.5 abreast as it is on the cusp of 9 and 10. Again the 767 is the one that sticks out here.


I then took a cabin width of 175m^2 and used a 6 abreast width and 7 abreast 2 aisle widths based on 20"seats and 20" aisles with 10 inch total wall width. I then calculated the cabin length based on these dimensions. To get the total length of the fuselage I added 3.5x the fuselage width (1.5x for nose + 2x for tail taper). to give me a single aisle length of 59m and a twin aisle length of 53m. I then used this to plug in to my weight estimation tool which gave me a fuselage structure weight of 10610kg for the narrow and 14256kg for the wide body.

My thoughts on that are on a weight perspective is that its a no brainer but I think there is a significant issue with rotation angle but it would have to be seen what size a ~2025 40klb thrust engine is, my guess is not small.

Fred

Nice graphs!

I think the fuselage weights differences between a widebody and narrowbody tell a lot. Even with all your assumptions, it's what we see in the 757 vs 762 weight differences.

The "significant issue with rotation angle" I don't see. Many aircraft are 60, 70 or even 80m long. Of course it would need long legs, but not exceptionally long.


DC8-73

When you make relatively narrow bodies very long (DC8-73, 757-300, MD90, A340-600) compared to their cross sections, you increasingly start to pay a price

- in terms of required weight/structure to provide strenght and stiffness to the aircraft, diluting overall economics/ structural efficiency.
- passenger / crew movement in the cabin start to be an issue during ground as well as inflight operations.
- perceived comfort of small seats/cabin starts to play at long stretches.
- so far composites prove less useful on narrowbody fusealges. E.g. impact (hail, ground) starts to overrule longitudinal load requirements in determining skin thickness.

Adding cross section (30 inch versus the 54m 757-300) keeping it a efficient narrowbody but removing/reducing some of the above constrains, opens new opportunities.
As Newbiepilot says, keeping everything else equal, fuselage weight is only a limited percentage of the aircraft.

Looking at cabin area and comparing weights and ranges is only part of the story. Why is no one talks not about wing area and thrust? A 767 has a wing that is 50% larger than the 757 and more powerful larger engines. That is where much of the OEW difference comes from.

Newbiepilot wrote:

Looking at cabin area and comparing weights and ranges is only part of the story. Why is no one talks not about wing area and thrust? A 767 has a wing that is 50% larger than the 757 and more powerful larger engines. That is where much of the OEW difference comes from.

I'd say that talking about cabin area/seats and ranges is done a lot because that is where the choices are, where decisions have to be made whereas with wing area and thrusts the physics tell you what they need to be (more or less).

Keesje wrote:

As Newbiepilot says, keeping everything else equal, fuselage weight is only a limited percentage of the aircraft.

But keeping everything else equal is not possible, you cannot preserve performance (payload/range, takeoff and landing distances, fuel burn) and increase the weight at a given technology level.

Fred

flipdewaf wrote:

Newbiepilot wrote:

Looking at cabin area and comparing weights and ranges is only part of the story. Why is no one talks not about wing area and thrust? A 767 has a wing that is 50% larger than the 757 and more powerful larger engines. That is where much of the OEW difference comes from.

I'd say that talking about cabin area/seats and ranges is done a lot because that is where the choices are, where decisions have to be made whereas with wing area and thrusts the physics tell you what they need to be (more or less).

Keesje wrote:

As Newbiepilot says, keeping everything else equal, fuselage weight is only a limited percentage of the aircraft.

But keeping everything else equal is not possible, you cannot preserve performance (payload/range, takeoff and landing distances, fuel burn) and increase the weight at a given technology level.

Fred

I think wing, fuel engine dimensions are determined by MTOW, which are mainly determined by payload - range requirements. Keep payload, range requirememnt the same expanding the fuselage cross section by 20% versus a narrow narrowbody has effect mainly on drag. A slightly wider long narrowbody gives positive better structural efficiency. I can't really imagine a 150 inch fuselage getting longer then 55m, like the 757 or DC8. You need some height to reduce strains / material to carry these loads.



I modified the drawing a bit, including the stretch -900 version giving in range for payload and accentuating the high comfort crew rest seat 1CD and behind the last passenger row.

keesje wrote:

I think wing, fuel engine dimensions are determined by MTOW, which are mainly determined by payload - range requirements. Keep payload, range requirememnt the same expanding the fuselage cross section by 20% versus a narrow narrowbody has effect mainly on drag. A slightly wider long narrowbody gives positive better structural efficiency. I can't really imagine a 150 inch fuselage getting longer then 55m, like the 757 or DC8. You need some height to reduce strains / material to carry these loads.

I have seen you post "a slightly wider long narrowbody gives positive structural efficiency" multiple times. Please provide the definition of structural efficiency that you are using. Please also show the equations that you are using to come to the conclusion that a 10 inch wider cabin increases structural efficiency and has a positive benefit, but a 34 inch wider cabin does not. Such math is going to be quite complicated because I don't see where there is a difference between 140 inches and 150 inches where getting wider reduces structural weight and then flips to the point where 180 inches is too wide and has such an impact on drag. Using your logic, drag is not a big factor going from 140 to 150in width and structural weight decreases yet drag is a big factor and structural weight increases (?) at 180 inches. I would like to see the math you use to derive 150 inches being most structurally efficient. Such math would probably require significant analysis by some masters and PhD level mechanical engineers who know as much or more about structural efficiency than the Airbus and Boeing design teams.

I have seen you share anecdotal comments supporting your idea of a wider narrowbody, but I cannot understand how making the cabin 10 inches wider is going to reduce the weight of the airplane. I don't know what definition you are using for structural efficiency either. It doesn't have a common definition like strength, strain, stress, etc does that can be found in an engineering text book.

Newbiepilot wrote:

I have seen you post "a slightly wider long narrowbody gives positive structural efficiency" multiple times. Please provide the definition of structural efficiency that you are using. Please also show the equations that you are using to come to the conclusion that a 10 inch wider cabin increases structural efficiency and has a positive benefit, but a 34 inch wider cabin does not. Such math is going to be quite complicated because I don't see where there is a difference between 140 inches and 150 inches where getting wider reduces structural weight and then flips to the point where 180 inches is too wide and has such an impact on drag. Using your logic, drag is not a big factor going from 140 to 150in width and structural weight decreases yet drag is a big factor and structural weight increases (?) at 180 inches. I would like to see the math you use to derive 150 inches being most structurally efficient. Such math would probably require significant analysis by some masters and PhD level mechanical engineers who know as much or more about structural efficiency than the Airbus and Boeing design teams.

I have seen you share anecdotal comments supporting your idea of a wider narrowbody, but I cannot understand how making the cabin 10 inches wider is going to reduce the weight of the airplane. I don't know what definition you are using for structural efficiency either. It doesn't have a common definition like strength, strain, stress, etc does that can be found in an engineering text book.

Its based on the second moment of inertia for the bending stresses and the hoop stresses for the pressure stresses. Normally one of these is the dominating stress on the fuselage and the other doesn't really add any mass to overcome it. As the fuselage gets longer the the bending moment stresses go up and as the fuselage gets wider the hoop stresses go up. There is a magic number at which point the dominating forces cross over and the fuselage will not be overbuilt for each of the driving conditions. I believe this is what Keesje is trying to achieve here. Its my understanding that you have to get very very very long before something becomes bending dominated over pressure dominated, like ~60m for a narrow body and probably over 70 for a 7 abreast. My weight estimation spreadsheets have this built in to help understand the dominating stresses. Whilst you need thousands of engineers to design the things getting a close estimates of where those engineers will end up can be quite accurate.

Fred

Fred, I agree with you. I want to know how Keesje came up with the 150 inch wide and 55 meter long airplane that is ideal. What math did he use? How does he know 150 inches is better than 140 inches or 180 inches?

A fuselage is a lot more complicated than a simply supported cylinder. An engineer can break down a simple cylinder, but airplanes aren't simple cylinders. The fuselage is made of frames, stringers and stiffness. Adjusting the dimensions of them can radically alter the equations for how to deal with the bending moment.

More importantly, when the smaller diameter needs to be increased due to needed strengthening for bending stress, you also have the option to just built it a tad shorter and trade in some seats. And this points out the big problem of the MoM. For the upper part of the market a wide body is better, for the lower part a single aisle is better.

seahawk wrote:

More importantly, when the smaller diameter needs to be increased due to needed strengthening for bending stress, you also have the option to just built it a tad shorter and trade in some seats. And this points out the big problem of the MoM. For the upper part of the market a wide body is better, for the lower part a single aisle is better.

Or more likely the geometry of the frames and stringers can be changed. I would be beyond shocked if Airbus or Boeing have the geometry of the frames and stringers so far off that increasing the diameter of the fuselage by 10 inches would reduce weight. I don't believe Keesje's concept because modern airplanes have been optimized with the size and dimensions of frames with carefully calculated distances, gaps, thicknesses, and materials in the frames and stringers that I don't see how the fuselage is going to get lighter by making it bigger.

Newbiepilot wrote:

Fred, I agree with you. I want to know how Keesje came up with the 150 inch wide and 55 meter long airplane that is ideal. What math did he use? How does he know 150 inches is better than 140 inches or 180 inches?

I would think that the fuse diameter would be based on trade studies rather than equations, not sure Keesje has done that (I'd be surprised) but I would be surprised if there was an equation to get such a thing because the variables are not easily measured. I'd be very surprised if was lighter than a narrower fuse maybe lighter per area but not per seat. I've put my computer away for the weekend so wont be checking till Tuesday.

Newbiepilot wrote:

A fuselage is a lot more complicated than a simply supported cylinder. An engineer can break down a simple cylinder, but airplanes aren't simple cylinders. The fuselage is made of frames, stringers and stiffness. Adjusting the dimensions of them can radically alter the equations for how to deal with the bending moment.

less of a more complicated equation and more the same equation but with more bits, it may be more complex than a simple cylinder but the factors scale in the same way so it's a good enough proxy.

Fred

flipdewaf wrote:

Newbiepilot wrote:

I have seen you post "a slightly wider long narrowbody gives positive structural efficiency" multiple times. Please provide the definition of structural efficiency that you are using. Please also show the equations that you are using to come to the conclusion that a 10 inch wider cabin increases structural efficiency and has a positive benefit, but a 34 inch wider cabin does not. Such math is going to be quite complicated because I don't see where there is a difference between 140 inches and 150 inches where getting wider reduces structural weight and then flips to the point where 180 inches is too wide and has such an impact on drag. Using your logic, drag is not a big factor going from 140 to 150in width and structural weight decreases yet drag is a big factor and structural weight increases (?) at 180 inches. I would like to see the math you use to derive 150 inches being most structurally efficient. Such math would probably require significant analysis by some masters and PhD level mechanical engineers who know as much or more about structural efficiency than the Airbus and Boeing design teams.

I have seen you share anecdotal comments supporting your idea of a wider narrowbody, but I cannot understand how making the cabin 10 inches wider is going to reduce the weight of the airplane. I don't know what definition you are using for structural efficiency either. It doesn't have a common definition like strength, strain, stress, etc does that can be found in an engineering text book.

Its based on the second moment of inertia for the bending stresses and the hoop stresses for the pressure stresses. Normally one of these is the dominating stress on the fuselage and the other doesn't really add any mass to overcome it. As the fuselage gets longer the the bending moment stresses go up and as the fuselage gets wider the hoop stresses go up. There is a magic number at which point the dominating forces cross over and the fuselage will not be overbuilt for each of the driving conditions. I believe this is what Keesje is trying to achieve here. Its my understanding that you have to get very very very long before something becomes bending dominated over pressure dominated, like ~60m for a narrow body and probably over 70 for a 7 abreast. My weight estimation spreadsheets have this built in to help understand the dominating stresses. Whilst you need thousands of engineers to design the things getting a close estimates of where those engineers will end up can be quite accurate.

Fred

Thanks Fred perfectly summarized.

Newbiepilot no doubt understands but apparently is playing games. The big difference with a 2-3-2 is that we are not only talking a different cross section, but different loads too, that extra passenger per row. A

It's becoming clear " anecdotic" as Newbiepilot would say that there are optimum cross sections. Maybe 2-2 under 100 seats, 3-3 up to 220 and 2-3 100-160. For larger aircraft 2-4-2, 3-3-3- and 3-4-3 seem the preferred cross section. Above 500 a double deck starts to make sense. And I'm not going to prove, because I've spend far to much time answering NBP's questions. He quickly ignores, changes the subject and asks new questions. Not very constructive. So Newbiepilot: prove it ain't so

Consider stringers, frames and stiffeners part of the tube, they are integral part of the load carrying structure in all semi-monocoque construction FEM models I've seen.

Anecdotical evidence over the last 50 years shows narrowbodies have grown in capacity and range. Following DC9, 737, A320 and MS-21 the cross section grew too.

[photoid][/photoid]Keesje, I agree with your last post. Different capacities have different optimized cross sections and dimensions. I also agree with Fred. It sounds like you backed down from the point you made about a slightly wider narrowbody improving structural efficiency.

With that said, I think Airbus wants to continue to push A321 sales. A new airplane would hurt those sales. I also think Airbus is still committed to the A330neo even if the entry into service date and first flight keeps getting delayed.

Newbiepilot wrote:

[photoid][/photoid]Keesje, I agree with your last post. Different capacities have different optimized cross sections and dimensions. I also agree with Fred. It sounds like you backed down from the point you made about a slightly wider narrowbody improving structural efficiency.

With that said, I think Airbus wants to continue to push A321 sales. A new airplane would hurt those sales. I also think Airbus is still committed to the A330neo even if the entry into service date and first flight keeps getting delayed.

It sounds like you backed down from the point you made about a slightly wider narrowbody improving structural efficiency.

Really Newbiepilot ?!

Anyway, this isn't a A321 and development would take the usual 7-8 years.

keesje wrote:

Cool image. Why are you reducing wingsweep angle from the A321? The A320 already has lower wingsweep than anything else that Airbus makes. Are you suggesting slower cruising speeds?

Wingsweep angles :

717 24.5
737 25
a320 25
757 25
a300 28
a310 28
a330 29.7
a340 29.7
767 31.5
777 31.6
727 32
707 35
747 37.5

Newbiepilot wrote:

keesje wrote:

Cool image. Why are you reducing wingsweep angle from the A321? The A320 already has lower wingsweep than anything else that Airbus makes. Are you suggesting slower cruising speeds?

Wingsweep angles :

717 24.5
737 25
a320 25
757 25
a300 28
a310 28
a330 29.7
a340 29.7
767 31.5
777 31.6
727 32
707 35
747 37.5

A slight reduction in sweep to improve aspect ratio and lift to drag ratio. Wingsweep is one of many variables determining optimal wing design. Cord, thickness, dihedral, materials, fuel capacity, flexibility, weight and profile all play a role. New materials and CFD analyses make possible higher aspect ratio, lower drag wings. I think we'll see less sweep / higher aspect ratio's over the next 30 years. https://www.nasa.gov/sites/default/files/styles/946xvariable_height/public/sugar_volt_semispan_2014_14-l-00010lh.jpg?itok=U_d8goya

keesje wrote:

Newbiepilot wrote:

keesje wrote:

Cool image. Why are you reducing wingsweep angle from the A321? The A320 already has lower wingsweep than anything else that Airbus makes. Are you suggesting slower cruising speeds?

Wingsweep angles :

717 24.5
737 25
a320 25
757 25
a300 28
a310 28
a330 29.7
a340 29.7
767 31.5
777 31.6
727 32
707 35
747 37.5

A slight reduction in sweep to improve aspect ratio and lift to drag ratio. Wingsweep is one of many variables determining optimal wing design. Cord, thickness, dihedral, materials, fuel capacity, flexibility, weight and profile all play a role. New materials and CFD analyses make possible higher aspect ratio, lower drag wings. I think we'll see less sweep / higher aspect ratio's over the next 30 years. https://www.nasa.gov/sites/default/files/styles/946xvariable_height/public/sugar_volt_semispan_2014_14-l-00010lh.jpg?itok=U_d8goya

Airbus increased wing sweep angle on the A350 to 31.9 from the A330 and A340. So far we haven't seen a transition to lower sweep, which is why I asked. The A350 should have the latest materials and computational fluid dynamic models.

I expect that Boeing intends to develop a clean sheet MOM Aircraft in 767 size. There biggest problem is to get an engine that has an efficiency similar to the PW GTF on the A321 but with enought thrust for a small dual aisle aircraft. This can't be done by scaling the GTF or LEAP engines, this requires a development of a new engine. And somebody has to pay for this development.
If Boeing decides to pay for the engine development, they will insist that they get this engine exclusive.

If the MOM market will be splitted between two Clean Sheet designs, Airbus as the second would have to pay even more for the engine development, as the remaining market is smaller.

In consequence I see only three options for Airbus:
1.) Do the first step with a Clean Sheet MOM Airbus
2.) Wait 10-15 years until Boeings MOM is no longer state of the art regarding economics and launch a Clean Sheet development. Until than develop aircrafts for other market sectors like a A318/A139 successor.
3.) Develop an Aircraft with existing engines but similar economics as the Boeing MOM

My concept for this would be a Trijet design:
-with 2 GTF or Leap engines (same power rating as for the A321) on the wings
-a third engine which is operating as hot standby standby during takeoff an landing. Efficieny is no issue for this engine as it's only used in TOGA situations. Therefore this engine will be placed inside the tail (and not on top) and during normal two engine cruising, the inlets will be closed by doors, to provide as less aerodynamical drag as possible. Also maintenance costs of this engine would be very low, as it will run only a few hours a week.

The benefit of this design is, that it always get the latest engine technology for free, as it can reuse the engines from the biggest aircraft market share. This will be different for a Dual-Engine MOM, where somebody has to pay the development of the next generation engines in 10-15 years - same situation as with the A380 today.

Just my thoughts
Jörg

Newbiepilot wrote:

Airbus increased wing sweep angle on the A350 to 31.9 from the A330 and A340. So far we haven't seen a transition to lower sweep, which is why I asked. The A350 should have the latest materials and computational fluid dynamic models.

Correct, and as you probably know Boeing reduced sweep on the 777X. Looking at sweep only is an oversimplification. The goal is to improve lift-drag ration, reduce weight, provide good airfield performamance and stow enough fuel.

Jörg I like your idea of a trijet. I used it some time ago for a 500 seat VLA design because the required 160k lbs engines don't exist. https://vimeo.com/5514854 I'm not sure if it would be a good idea if engines exist with the required thrust levels for twin engine operations. Over the last few years tail engine came back with concepts using hybrid energy. They would also absorb energy during e.g. decent.



Back on topic/ your post, it seems most people believe Airbus will launch an A321 stretch, probably rewing, before coming up with something new for the mid segment.

I believe, using the same technology, capacity and range, under ~300 seats / 4500NM a big narrow body might be more efficient than a small wide body.

Existing aircraft design parameters seem to support this assumption. I sketched the stretch -900 in all economy class lay-out. Seatcomfort should be superior to most other aircraft economy cabins because of effective 2 inch additional seat space per passenger seat. (every single passenger 2 full sized armrests and 32 inch seat pitch) and sufficient inches wall thickness have been reserved for effective noise isolation.

A 60.3 meter narrowbody? That is longer than the A330-800. That thing is going to take an hour to board.

Newbiepilot wrote:

A 60.3 meter narrowbody? That is longer than the A330-800. That thing is going to take an hour to board.

In case you missed, this is a rather wide narrowbody concept, where people can pass each other in the 30 inch wide aisle. Aisles are usually 18-20 inch.

Yes we talked about how much cabin space is wasted due to double arm rests and a 30 inch aisle. 12 more inches of cabin width and the plane could be a 2-3-2 widebody and earn more revenue with those cabin dimensions while simultaneously reducing the number if exit doors in half and speeding up loading and unloading without requiring scrum boarding shoving past people in the aisle. Given the plethora of airplanes flying with 17 inch wide seats, I think I know what plane the airlines would prefer and it won't be a 60 meter long Xwide narrowbody.

keesje wrote:

Newbiepilot wrote:

A 60.3 meter narrowbody? That is longer than the A330-800. That thing is going to take an hour to board.

In case you missed, this is a rather wide narrowbody concept, where people can pass each other in the 30 inch wide aisle. Aisles are usually 18-20 inch.

Assuming, of course, people actually do that versus using the extra space to just stand in the middle and avoid rubbing up against seats/strangers.

Newbiepilot wrote:

A 60.3 meter narrowbody? That is longer than the A330-800. That thing is going to take an hour to board.

Depends where you board from. Which I believe is the most likely solution to this. A narrowbody with main boarding through L2, not L1.


Aside from that - most European airports already embark and debark through front and rear exits - making a narrowbody a quasi-double aisle for the turnaround process - so its really a problem of archaic infrastructure or legislation elsewhere in the world.

keesje wrote:

Will Airbus ever launch a dedicated replacement to fill their A320 series - A330 series gap ?


Airbus A370-800 60t Medium Concept

I'm sure I'd like to be a fly on the wall, but this is ridiculous. Does this image give us a sense of scale?

Newbiepilot wrote:

A 60.3 meter narrowbody? That is longer than the A330-800. That thing is going to take an hour to board.

And to think something significant narrower and just 3 meters short has been in operation for almost 50 years, in-cre-di-ble https://www.airliners.net/photo/KLM-Royal-Dutch-Airlines/McDonnell-Douglas-DC-8-63/1377444

Btw toxtethogrady, that fly is just to prevent a picture starts its own life. picture gives some scale. Cross section would be around 15% wider than a A320 and the loads wouldn't change much.

I don't think loading times are an issue for the mom, if you want to fly 4/5 hrs then you would be flying something far more capable than required if you are doing 7/8 hrs then you don't really care all that much. I wouldn't think airlines are too bothered about turnaround times on TATL.

Fred

keesje wrote:

Newbiepilot wrote:

A 60.3 meter narrowbody? That is longer than the A330-800. That thing is going to take an hour to board.

And to think something significant narrower and just 3 meters short has been in operation for almost 50 years, in-cre-di-ble https://www.airliners.net/photo/KLM-Royal-Dutch-Airlines/McDonnell-Douglas-DC-8-63/1377444

Btw toxtethogrady, that fly is just to prevent a picture starts its own life. picture gives some scale. Cross section would be around 15% wider than a A320 and the loads wouldn't change much.

I'm not saying such a plane can't be built. Is the DC8 your vision of success? There were about 200 of the stretched DC8s built. The DC8 got crushed by the 707 about 2 to 1. The 767 with its 2-3-2 cross section has also about double the fleet size as the DC8. Why can't we built a widebody for this gap again? Why a super long awkwardly and pointlessly wide narrowbody? Again 12 more inches gets you industry standard 17 inch wide seats and 18 inch wide aisles if I did my math correctly.

I still doubt Airbus wants to build such a plane but Boeing is interested.

A competitive light and practicle 2-3-2 for medium haul. Why has it never been a succes? The 767 only became a succes when it was stretched and got longer range. Nothing prevented anybody from building short range widebody. The logic apart from ' Boeing says so' is unclear to me. Defeating physics proved unsuccesfull so far..

I like the propulsive fuselage concept. Replace the APU with a larger turbofan that is driving a geared ultra large fan, that is sucking the boundary layer of the fuselage and converting it into thrust.

http://aviationweek.com/technology/ever ... er-designs

Bauhaus Design.

flipdewaf wrote:

I don't think loading times are an issue for the mom, if you want to fly 4/5 hrs then you would be flying something far more capable than required if you are doing 7/8 hrs then you don't really care all that much. I wouldn't think airlines are too bothered about turnaround times on TATL.
Fred

I expect that the most MOMs will replace A321s where more capacity is needed, only a few will fly further than the A321 today.
The short turn around times will be one of the few Boeings MOM characteristics, which Airbus can't beat without doing a clean sheet design. As we can see today on the A330NEO vs. 787, efficiency depends primary on the engine and more capacity and range just require a A322/737MAX11 with a new wing.

But a widebody with more range will be having a hard time to compete with the A321 in economics on missions that are time critical when it comes to turning the plane around. We would be talking less than 2500nm range missions.

seahawk wrote:

But a widebody with more range will be having a hard time to compete with the A321 in economics on missions that are time critical when it comes to turning the plane around. We would be talking less than 2500nm range missions.

Also most of those 321 missions are into smaller airports with restricted gates for larger frames. Will a widebody fit into the same box?

Most have space for at least a small number of 767s or A330s (usually less of the later)

seahawk wrote:

But a widebody with more range will be having a hard time to compete with the A321 in economics on missions that are time critical when it comes to turning the plane around. We would be talking less than 2500nm range missions.

Agree that is the biggest risk for a MoM. Overspecification and beeing wiped away by something smaller lighter and way cheaper that can fly 4000NM..
http://i191.photobucket.com/albums/z160/keesje_pics/AirbusA321A322NEOStretch757.jpg

.
While everybody assumes Airbus will need a new wing for a stretch, that only seems the case if payload-range must grow accordingly.

A simple 3 row stretch based on the A321LR MTOW, wing, engines etc. would produce a realistic 250 seat aircraft for flight up to 2800NM.

It would have low development cost, full compatibility, fit all the gates. A simple capacity for range derivative.

An A321-10 so to say, Or A321Plus fully matching 757 seat capacity

You realize that aircraft could be payload-restricted on some transcons, and couldn't make it across the pond, right? 2800nm for the MoM is cringeworthy.

ASQ400 wrote:

You realize that aircraft could be payload-restricted on some transcons, and couldn't make it across the pond, right? 2800nm for the MoM is cringeworthy.

Yes, it would give in on range and hardly qualify as medium range. But it would cover large domestic and regional markets like Europe, China and 90% of Americas. An uncomplicated cheap fully compatible 250 seater. Leisure and LCC's would probably love it.

keesje wrote:

ASQ400 wrote:

You realize that aircraft could be payload-restricted on some transcons, and couldn't make it across the pond, right? 2800nm for the MoM is cringeworthy.

Yes, it would give in on range and hardly qualify as medium range. But it would cover large domestic and regional markets like Europe, China and 90% of Americas. An uncomplicated cheap fully compatible 250 seater. Leisure and LCC's would probably love it.

It's the original, failed premise of the 321 and 739, which failed spectacularly

A321 a failed premise?

A321LR has 4000NM range. Add 3t to OEW + 2t payload & it should still have decent range. Probably better than A321CEO? I don't have a payload range graph..

keesje wrote:

A321 a failed premise?

A321LR has 4000NM range. Add 3t to OEW + 2t payload & it should still have decent range. Probably better than A321CEO? I don't have a payload range graph..

A321ceo originally (early design) had low range, which was an impediment.
A321neo and LR learned that lesson, and focus on range. Your proposal, which you state has 2800nm range, has even less than the original 739 (not ER), which distinctly under-performed.

I'd be really surprised if Airbus went ahead with this. I'd imagine that right now they are focused on getting the A400m, A320 and A330NEO engine woes addressed. And the issues with Zodiac.

I think this market will be addressed with the A320 replacement and the A319 going away.
Perhaps going back to another four member family with a "323".

I could see something like a replacement being 2/3 meters longer than the A320 and A321. The 322 being the same length as the A321 but, a wide body in 2-4-2 configuration. Uses the same wing, horizontal tp, VTP, mlg, and windscreen as the A320/A321.
323 being a stretch of the 322 to around 50/51 meters.

Slug71 wrote:

I'd be really surprised if Airbus went ahead with this. I'd imagine that right now they are focused on getting the A400m, A320 and A330NEO engine woes addressed. And the issues with Zodiac.

I think this market will be addressed with the A320 replacement and the A319 going away.
Perhaps going back to another four member family with a "323".

I could see something like a replacement being 2/3 meters longer than the A320 and A321. The 322 being the same length as the A321 but, a wide body in 2-4-2 configuration. Uses the same wing, horizontal tp, VTP, mlg, and windscreen as the A320/A321.
323 being a stretch of the 322 to around 50/51 meters.

I assure you this is not a legitimate propostiob from A or B, just wishful thinking from Mr. Keesje