User avatar
seahawk
Posts: 8521
Joined: Fri May 27, 2005 1:29 am

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 11:15 am

Amiga500 wrote:
seahawk wrote:
I just have a huge problem when linking the bypass ratio to thrust levels.


Yeah, well... there is a link, but its far more complex than just bigger = more.

I suppose most are just seeing:
- Newer engines have higher BPRs.
- Newer engines have higher thrust levels.
and extrapolating a somewhat incorrect conclusion from that.

While higher BPR will help produce thrust more efficiently at low speed, at high speed that tails off and eventually becomes a hindrance.


And then we are looking at the differences between optimal working rpms for each section and then the Mach number of the tips of the fan... If I want to reach 55.000lbs with a LEAP, it is not enough to increase the fan so much that the increase in bypass ratio matches the needed increase in thrust. It would be easy if it would be so easy.
 
User avatar
keesje
Posts: 13045
Joined: Thu Apr 12, 2001 2:08 am

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 11:22 am

seahawk wrote:
Amiga500 wrote:
seahawk wrote:
I just have a huge problem when linking the bypass ratio to thrust levels.


Yeah, well... there is a link, but its far more complex than just bigger = more.

I suppose most are just seeing:
- Newer engines have higher BPRs.
- Newer engines have higher thrust levels.
and extrapolating a somewhat incorrect conclusion from that.

While higher BPR will help produce thrust more efficiently at low speed, at high speed that tails off and eventually becomes a hindrance.


And then we are looking at the differences between optimal working rpms for each section and then the Mach number of the tips of the fan... If I want to reach 55.000lbs with a LEAP, it is not enough to increase the fan so much that the increase in bypass ratio matches the needed increase in thrust. It would be easy if it would be so easy.


Just scale up the core a bit :wink2:
"Never mistake motion for action." Ernest Hemingway
 
User avatar
bikerthai
Posts: 2906
Joined: Wed Apr 28, 2010 1:45 pm

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 1:22 pm

Amiga500 wrote:
the concept of a tight, light, 7AB ovoid is fraught with difficulties.


But a challenge that must be conquered if they are to transition to a BWB.

bt
Intelligent seeks knowledge. Enlightened seeks wisdom.
 
Amiga500
Posts: 2267
Joined: Tue Mar 03, 2015 8:22 am

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 2:04 pm

bikerthai wrote:
Amiga500 wrote:
the concept of a tight, light, 7AB ovoid is fraught with difficulties.


But a challenge that must be conquered if they are to transition to a BWB.

bt


Erm, who said that is ever going to happen?
 
User avatar
Revelation
Posts: 20960
Joined: Wed Feb 09, 2005 9:37 pm

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 2:13 pm

seahawk wrote:
And then we are looking at the differences between optimal working rpms for each section and then the Mach number of the tips of the fan... If I want to reach 55.000lbs with a LEAP, it is not enough to increase the fan so much that the increase in bypass ratio matches the needed increase in thrust. It would be easy if it would be so easy.

Good thing CFM and Pratt have been working the issues for a while now, they presented a first round of proposals last summer and a more detailed set last winter, and have six years till proposed EIS.

keesje wrote:
Just scale up the core a bit :wink2:

According to John Leahy it's Boeing that gets the customized cores and it's Airbus that has to deal with making those cores work on their designs.

We shall see if the pattern holds.
Wake up to find out that you are the eyes of the world
The heart has its beaches, its homeland and thoughts of its own
Wake now, discover that you are the song that the morning brings
The heart has its seasons, its evenings and songs of its own
 
User avatar
seahawk
Posts: 8521
Joined: Fri May 27, 2005 1:29 am

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 3:06 pm

Revelation wrote:
seahawk wrote:
And then we are looking at the differences between optimal working rpms for each section and then the Mach number of the tips of the fan... If I want to reach 55.000lbs with a LEAP, it is not enough to increase the fan so much that the increase in bypass ratio matches the needed increase in thrust. It would be easy if it would be so easy.

Good thing CFM and Pratt have been working the issues for a while now, they presented a first round of proposals last summer and a more detailed set last winter, and have six years till proposed EIS.

keesje wrote:
Just scale up the core a bit :wink2:

According to John Leahy it's Boeing that gets the customized cores and it's Airbus that has to deal with making those cores work on their designs.

We shall see if the pattern holds.


I was merely referring to the speculation on the design within this thread. The engine makers are all 3 very eager to get a place on the wing of the 797 and they give the 797 the best engines they can make, as it is a huge market an nobody wants to give up a chance at selling 10.000 or more engines.
 
iberiadc852
Posts: 257
Joined: Thu May 26, 2005 8:23 am

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 3:33 pm

astuteman wrote:
morrisond wrote:

If they don't do a dual aisle 7W - they would be better off to do wider 6W SA for NMA that they reuse for NSA than do a separate 8W for NMA and 6W for NSA. .


A tight, light 7-across ovoid cross section not massively greater than the cross-section of an A32X would not weigh a lot more than the A321XLR and not be much more expensive.

I'm pretty clear in my mind that an 8-across NMA and 6-across NSA just isn't a solution that will deliver all of the things that supporters of this approach believe it will.


Ok, so let's say that Boeing goes ahead with the 7-across 797 NMA. How safe can they be that Airbus won't launch just after a 797 alternative 8ab with the latest techologies (ie. a A310 size efficiency aimed aircraft in width, interior space, wings, technologies, etc.), that can kill the 797 economics?

Are those arguments (supposed better comfort, synergies etc.), really so strong to overcome the theoretical 7ab loss of efficiency?
variety is the spice of life; that's what made the "old times" so good
 
FluidFlow
Posts: 238
Joined: Wed Apr 10, 2019 6:39 am

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 3:38 pm

Here just a small info about fineness of existing aircraft. Aerodynamically the best ratio is around 6 but this does not work for airliners because of the tail. For a jetliner the best ratio lies around 7.5-8. Everything above this ratio means more drag, if you are below this the tail (H-Stab) of the aircraft is too small (not enough authority due to proximity to the CoG). The reason most aircraft are actually above that ratio is because the next higher diameter (one more seat per row, or seat + aisle) increases the size of the aircraft massively. The numbers for the 797 are made up based on 737 cabin height and 4.9m width.

Name Length Width((W+H)/2) Ratio Seats (1class)
A318 31.44 4.045 7.772558714 136
A319 33.84 4.045 8.365883807 160
A320 37.57 4.045 9.288009889 195
A321 44.51 4.045 11.00370828 240
A330-800 58.82 5.64 10.42907801 406
A339-900 63.66 5.64 11.28723404 440
B737-7 35.56 3.76 9.457446809 172
B737-8 39.47 3.76 10.49734043 200
B737-9 42.16 3.76 11.21276596 220
B737-10 43.8 3.76 11.64893617 230
B757-200 47.3 3.76 12.57978723 239
B757-300 54.4 3.76 14.46808511 295
B767-200 48.51 5.22 9.293103448 290
B767-300 54.94 5.22 10.52490421 351
B767-400 61.37 5.22 11.75670498 375
B787-8 56.72 5.85 9.695726496 359
B787-9 62.81 5.85 10.73675214 406
B787-10 68.28 5.85 11.67179487 440

B797-5 35.6 4.45 8 200
B797-6 40.05 4.45 9 240
B797-7 44.5 4.45 10 280
B797-8 48.95 4.45 11 320

The result shows where the different versions would land and what their actual "problems" are. The -5 is too small and would need a redesigned tail if the tail is optimized for the -7. It would be an really inefficient airliner like the A318 and the B737-7. The -6 is in direct competition with the A321 and there Boeing has to show that the small twin aisle can be more efficient than a single aisle aircraft. The -7 would be in the perfect spot. The -8 would also be feasible even tho it is really close to the 787-8 and with more than 300 seats would need additional FA's. Also it is important for Boeing to optimize the wing and tail between the -7 and the -8 to have an aircraft that can shine and also stop airbus from closing into this space. This leaves the -6 sub optimal compared to the A321.

There are two things I conclude out of this. Boeing needs to decide if they want to hit the MoM perfect with the -7 and -8 but leave the A321 "alone" or fight for that space and drop the -8 (needs additional development and can be launched later). Smaller aircraft (an NSA hybrid) is not possible because this would need a complete overhaul of the wing/wingbox/tail and this aircraft would even then be not competitive vs the B737-8 or A320. A NSA with a smaller fuselage would be necessary to compete in the 180-200 market and stretched versions of this aircraft can also fill the ~240 pax area. Now Boeing has to figure out which segment gives the most sales to launch the program. It will possibly be the -7 but witch which tail? One between the -6/-7 or one between the -7/-8? This will be the question which will show the goal of the MoM at Boeing.
 
User avatar
keesje
Posts: 13045
Joined: Thu Apr 12, 2001 2:08 am

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 4:55 pm

A tight, light 7-across ovoid cross section not massively greater than the cross-section of an A32X would not weigh a lot more than the A321XLR and not be much more expensive.


Let's just add 40 inch in cross section, a seatpan, 2 armrests and an aisle. Making a flat cross section adds weight over a circular one. Floorbeams also significantly heavier, the 3 seater in the middle. For same seat capacity the fuselage would shorter though. But also less AKH positions because of that. Physics.

Image
"Never mistake motion for action." Ernest Hemingway
 
JayinKitsap
Posts: 1397
Joined: Sat Nov 26, 2005 9:55 am

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 6:01 pm

keesje wrote:
A tight, light 7-across ovoid cross section not massively greater than the cross-section of an A32X would not weigh a lot more than the A321XLR and not be much more expensive.


Let's just add 40 inch in cross section, a seatpan, 2 armrests and an aisle. Making a flat cross section adds weight over a circular one. Floorbeams also significantly heavier, the 3 seater in the middle. For same seat capacity the fuselage would shorter though. But also less AKH positions because of that. Physics.

Image


Looking at the NMA7-200 section inserting a compression strut just above the ceiling to support the bins there would allow a circular arc from the floor beams to this strut, then a flatter arc above the strut. The shell would then be 4 circular arcs with the sides being one radius, the bottom a 2nd and the top a flatter 3rd radius. This would be reasonably efficient and keeps the floor beams in tension. Assuming hinges in the shell at the strut/floor connection, the side radius puts tension into the strut and floor beams, but the flatter radius top and bottom would cause compression, so probably a net tension in the floor and a net compression in the ceiling strut under internal pressure. Most importantly, this approach reduces the rib moment at the windows where the thinnest members are needed.

I've done similar stays in flat oval pressure vessels, sure they are heavier than a circular section but not substantially.
 
DenverTed
Posts: 243
Joined: Wed Mar 27, 2019 11:12 pm

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 6:03 pm

keesje wrote:
Let us assume a realistic 797 benchmark:

:airplane: a NB fuselage
:airplane: mass produced
:airplane: 2 versions for up to 230-250 passengers
:airplane: range up to up to 3700-4700NM,
:airplane: rolling of US, China and Euro assembly lines, a few years earlier than a 797.
:airplane: an OEW of around 52-55t
:airplane: a MTOW of around 101t.
:airplane: ability to carry 10-12 cargo / luggage containers/pallets or bulk load
:airplane: 18 inch wide seats
:airplane: commonality, variants in service by most major airlines
:airplane: established, competitive global maintenance and support options
:airplane: a choice between the latest Geared / Leap 80 inch fan engines
:airplane: a list price of an A321NEO + 10-15%.

https://07185918574543712684.googlegrou ... zGRin12AV0

I think an oval, 2 aisle 797 better be mightly light weight, and cheap to produce. In large quantities, from day one. Maybe EIS in 2025, but no rushed design and certification and ensure lean and low cost production using new supply chain and aftermarket strategies..
:expressionless:

I think Boeing is to follow a robust roadmap of program risk migitation
and explore ways to vigorously strenghten share holder value moving forward.
:checkmark:

Will the new NB fuselage be CFRP? Is the MC-21 a CFRP fuselage? I haven't found out searching.
I think that is the big decision, to choose a fuselage for the 737 replacement. I don't think it is time yet. In 2025 to 2028 is when they will commit to a CFRP mass produced NB fuselage.

My personal preference for the NMA is 2-2-2, 2-3-2, 2-4-2, and lastly 3-3. Why degrade the air travel experience? Twin aisle for 200 seats and up is a plus. If it is all about design to the bone economy, then the 787 is great, and yes a single aisle 5m longer than the A321 is just the ticket. A 250 seat to 300 seat single aisle, and why waste all that A320/737 width. We'll go with 17" seats, 1.5 armrests, 18" aisle and 1/2" between the armrest and sidewall. 133" interior width, 6" savings over the 737. Who want's that? I want 2-2-2 and 18" seats and 2" armrests, 163" width. Think big!
 
2175301
Posts: 1439
Joined: Wed May 16, 2007 11:19 am

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 6:19 pm

I have refrained from posting for a few days; and would like to give my opinion at this point on some of the issues raised and debate on this forum:

1) I generally agree with the point that a certain poster was clearly showing (up to that point) a highly negative view and had proposed a whole collection of individually different possibilities; many of which were not plausible given the history and what was known; and could understand why some would see that overall as trolling. It appears to me that individual poster has become more focused and realistic since. I'd like to thank them for that improvement.

2) I agree with that Boeing has not told us what the 797 actually will be, except that its ovid, does not push technology, is focused on manufacturability, focuses on passengers and minimizes extra cargo (no claims that is uses existing containers - any modeling by anyone using and existing container assumption is in my opinion is likely wrong), and is targets to a middle of market target segment. There are strong hints or indications that it seats 7 wide with 2 isles.

Anyone who knows more has signed a NDA and it appears that the NDA has held (no real leaks). A lot of Airline Executives, who have signed such NDA's, have said that they are excited about what Boeing is proposing.

3) I agree with astuteman that there are no long term manufacturing competitive advantages. However, I believe that in this industry there can be short term 5-10 years manufacturing advantages by changes in technology and approach. IF Boeing pulls off what they say the are planning to do in regards to the cost of manufacturing a commercial airliner; it may realistically give Boeing a 5-10 year advantage in the market that they apply it too. Since the MOM market size is not expected to be huge... The proposed 797 will likely end up owning the market segment IF Boeing pulls it off because Airbus will not be able to effectively and economically enter it in a timely manner. In my opinion, that actually reduces the gamble on Boeing's part.

4) I disagree with the concept that the NMA and NSA will share major components (other than perhaps flight deck layout and instruments for possibly a common type rating). My opinion, and my sources, indicate that the NSA concepts are for a much different aircraft; and what Boeing is counting on from the NMA is a refined and fleshed out new manufacturing/procurement strategy that will give the NSA a huge cost advantage over current existing aircraft in the NSA size range. I expect that the NSA will likely be a robust (but not extreme) technology push - using a substantially proven NMA manufacturing/procurement method.

5) I have personally avoided the debates on what is the potential layouts as it is my understanding that Boeing has already worked out what they are offering - in detail - on at least the 1st variant of the proposed 797. I see no reason not to just wait and see what comes out when it is offered for sale. Apparently a lot of airlines are very excited about their detailed concept. Why debate something already decided.

6) It is my understanding from both my source and also released by other sources that the 797 program is sufficiently advanced that they were ready to ask the Board of Directors earlier this year for permission to offer it for sale, that it had passed a key engineering and manufacturing review point: far more advanced than previous projects (lessons learned) - and is near if not at design freeze. That it was not offered for sale (and not part of a major airshow) only because of the 737Max8 issue; which to me is very understandable. I personally do not understand people who keep criticizing Boeing for continuing delays, when their strategy of performing far more engineering and design work up front before program approval has been discussed many times (different than past programs that went astray and damaged their reputation).

Their plans were to offer for sale in 2019, and then if enough orders materialize; authorize full program launch (production) in 2020. My information is that all of that was on track before the 737Max8 issues, and yet could still happen. Boeing has previously used the Offer for sale 1st, and not authorize production unless sufficient sales before; although its been a while (and not on the 787). I take that as one of the lessons learned from the more recent aircraft developments (along with advanced design and modeling up front before even offering for sale).

The 2025 delivery is still possibly plausible; but, may be affected by the 737Max8 issue. In my opinion likely no more than 1 year. It is clear to me from what information I have that the FAA is changing their approval process to ensure an independent 3rd party review of the Failure Modes and Effects Analysis (FMEA); and that in general all companies will need to apply more focus on the FMEA's in the future.

Have a great day,
 
DenverTed
Posts: 243
Joined: Wed Mar 27, 2019 11:12 pm

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 6:23 pm

FluidFlow wrote:
Here just a small info about fineness of existing aircraft. Aerodynamically the best ratio is around 6 but this does not work for airliners because of the tail. For a jetliner the best ratio lies around 7.5-8. Everything above this ratio means more drag, if you are below this the tail (H-Stab) of the aircraft is too small (not enough authority due to proximity to the CoG). The reason most aircraft are actually above that ratio is because the next higher diameter (one more seat per row, or seat + aisle) increases the size of the aircraft massively. The numbers for the 797 are made up based on 737 cabin height and 4.9m width.

Name Length Width((W+H)/2) Ratio Seats (1class)
A318 31.44 4.045 7.772558714 136
A319 33.84 4.045 8.365883807 160
A320 37.57 4.045 9.288009889 195
A321 44.51 4.045 11.00370828 240
A330-800 58.82 5.64 10.42907801 406
A339-900 63.66 5.64 11.28723404 440
B737-7 35.56 3.76 9.457446809 172
B737-8 39.47 3.76 10.49734043 200
B737-9 42.16 3.76 11.21276596 220
B737-10 43.8 3.76 11.64893617 230
B757-200 47.3 3.76 12.57978723 239
B757-300 54.4 3.76 14.46808511 295
B767-200 48.51 5.22 9.293103448 290
B767-300 54.94 5.22 10.52490421 351
B767-400 61.37 5.22 11.75670498 375
B787-8 56.72 5.85 9.695726496 359
B787-9 62.81 5.85 10.73675214 406
B787-10 68.28 5.85 11.67179487 440

B797-5 35.6 4.45 8 200
B797-6 40.05 4.45 9 240
B797-7 44.5 4.45 10 280
B797-8 48.95 4.45 11 320

The result shows where the different versions would land and what their actual "problems" are. The -5 is too small and would need a redesigned tail if the tail is optimized for the -7. It would be an really inefficient airliner like the A318 and the B737-7. The -6 is in direct competition with the A321 and there Boeing has to show that the small twin aisle can be more efficient than a single aisle aircraft. The -7 would be in the perfect spot. The -8 would also be feasible even tho it is really close to the 787-8 and with more than 300 seats would need additional FA's. Also it is important for Boeing to optimize the wing and tail between the -7 and the -8 to have an aircraft that can shine and also stop airbus from closing into this space. This leaves the -6 sub optimal compared to the A321.

There are two things I conclude out of this. Boeing needs to decide if they want to hit the MoM perfect with the -7 and -8 but leave the A321 "alone" or fight for that space and drop the -8 (needs additional development and can be launched later). Smaller aircraft (an NSA hybrid) is not possible because this would need a complete overhaul of the wing/wingbox/tail and this aircraft would even then be not competitive vs the B737-8 or A320. A NSA with a smaller fuselage would be necessary to compete in the 180-200 market and stretched versions of this aircraft can also fill the ~240 pax area. Now Boeing has to figure out which segment gives the most sales to launch the program. It will possibly be the -7 but witch which tail? One between the -6/-7 or one between the -7/-8? This will be the question which will show the goal of the MoM at Boeing.

If 8 is the best ratio, if one were to design a new 150 seat aircraft, then 6x beats 5x and at 175 seats, 5x is definitely not the solution. Looking towards an eventual 737-7 and 737-8 replacement.
 
DenverTed
Posts: 243
Joined: Wed Mar 27, 2019 11:12 pm

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 6:41 pm

JayinKitsap wrote:
keesje wrote:
A tight, light 7-across ovoid cross section not massively greater than the cross-section of an A32X would not weigh a lot more than the A321XLR and not be much more expensive.


Let's just add 40 inch in cross section, a seatpan, 2 armrests and an aisle. Making a flat cross section adds weight over a circular one. Floorbeams also significantly heavier, the 3 seater in the middle. For same seat capacity the fuselage would shorter though. But also less AKH positions because of that. Physics.

Image


Looking at the NMA7-200 section inserting a compression strut just above the ceiling to support the bins there would allow a circular arc from the floor beams to this strut, then a flatter arc above the strut. The shell would then be 4 circular arcs with the sides being one radius, the bottom a 2nd and the top a flatter 3rd radius. This would be reasonably efficient and keeps the floor beams in tension. Assuming hinges in the shell at the strut/floor connection, the side radius puts tension into the strut and floor beams, but the flatter radius top and bottom would cause compression, so probably a net tension in the floor and a net compression in the ceiling strut under internal pressure. Most importantly, this approach reduces the rib moment at the windows where the thinnest members are needed.

I've done similar stays in flat oval pressure vessels, sure they are heavier than a circular section but not substantially.

That's an interesting concept. So if you take a plane with a big crown, like the 777 or 747, and put a strut across the ceiling, then flatten the roof, and put a tension strut from the ceiling to the roof to hold it flat from buldging back to circular? I've seen the Jon Ostrower article that shows the 797 with a circular top and a flat bottom, which I assume they can get with the struts beneath the floor. I wonder if this all pencils out by weight and cost, but the concept of using struts structurally to decrease the surface area seems like a good idea.
 
DenverTed
Posts: 243
Joined: Wed Mar 27, 2019 11:12 pm

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 6:51 pm

2175301 wrote:

2) I agree with that Boeing has not told us what the 797 actually will be, except that its ovid,

And it will be named the 797 Publius Ovidius Naso-liner.
 
morrisond
Posts: 1179
Joined: Thu Jan 07, 2010 12:22 am

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 7:56 pm

DenverTed wrote:
JayinKitsap wrote:
keesje wrote:


Let's just add 40 inch in cross section, a seatpan, 2 armrests and an aisle. Making a flat cross section adds weight over a circular one. Floorbeams also significantly heavier, the 3 seater in the middle. For same seat capacity the fuselage would shorter though. But also less AKH positions because of that. Physics.

Image


Looking at the NMA7-200 section inserting a compression strut just above the ceiling to support the bins there would allow a circular arc from the floor beams to this strut, then a flatter arc above the strut. The shell would then be 4 circular arcs with the sides being one radius, the bottom a 2nd and the top a flatter 3rd radius. This would be reasonably efficient and keeps the floor beams in tension. Assuming hinges in the shell at the strut/floor connection, the side radius puts tension into the strut and floor beams, but the flatter radius top and bottom would cause compression, so probably a net tension in the floor and a net compression in the ceiling strut under internal pressure. Most importantly, this approach reduces the rib moment at the windows where the thinnest members are needed.

I've done similar stays in flat oval pressure vessels, sure they are heavier than a circular section but not substantially.

That's an interesting concept. So if you take a plane with a big crown, like the 777 or 747, and put a strut across the ceiling, then flatten the roof, and put a tension strut from the ceiling to the roof to hold it flat from buldging back to circular? I've seen the Jon Ostrower article that shows the 797 with a circular top and a flat bottom, which I assume they can get with the struts beneath the floor. I wonder if this all pencils out by weight and cost, but the concept of using struts structurally to decrease the surface area seems like a good idea.


The other concept I've heard is half a Circle on top with 1/3 or 1/4 of a larger diameter circle on bottom - would that not be relatively simple to build and take care of the floor compression issues?
 
RJMAZ
Posts: 1529
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 10:38 pm

FluidFlow wrote:
B797-5 35.6 4.45 8 200
B797-6 40.05 4.45 9 240
B797-7 44.5 4.45 10 280
B797-8 48.95 4.45 11 320

Your numbers and lengths are way off. The two class 797 seating numbers of 228 and 267 are fractionally higher than the 767-200 (214) and 767-300 (261). I'm not sure how your lengths could then be less than the 767 as they are both 7ab.

Your seating numbers for the 797-6 and 797-7 are even smaller than the 757.

The numbers for a 7ab cross section would then be:
B797-5 44 4.45 9.88 220
B797-6 49 4.45 11.01 260
B797-7 55 4.45 12.35 305
B797-8 60. 4.45 13.48 350

That is one skinny plane.
 
morrisond
Posts: 1179
Joined: Thu Jan 07, 2010 12:22 am

Re: Boeing 797 Thread - 2019

Tue Jul 23, 2019 11:12 pm

RJMAZ wrote:
FluidFlow wrote:
B797-5 35.6 4.45 8 200
B797-6 40.05 4.45 9 240
B797-7 44.5 4.45 10 280
B797-8 48.95 4.45 11 320

Your numbers and lengths are way off. The two class 797 seating numbers of 228 and 267 are fractionally higher than the 767-200 (214) and 767-300 (261). I'm not sure how your lengths could then be less than the 767 as they are both 7ab.

Your seating numbers for the 797-6 and 797-7 are even smaller than the 757.

The numbers for a 7ab cross section would then be:
B797-5 44 4.45 9.88 220
B797-6 49 4.45 11.01 260
B797-7 55 4.45 12.35 305
B797-8 60. 4.45 13.48 350

That is one skinny plane.


Hi RJMAZ,

I think where a lot of the confusion is with the fact that 767 Capacities are usually quoted with long haul seating. NMA capacities seem to be quoting shorter haul 2 class capacity. Thomas Cook packs 326 into an 763 in a single class layout.

No one really knows what seating density Boeing is using for NMA - the only quotes I recall were A321 plus 1 extra seat in width.

I think a better way to look at it would be start with an A321 and figure it out from there.

Supposedly NMA-6 is 5-10% bigger than A321 - as it would probably have one more seat in width (or 16.7% more Y seats and 50% more Premium seats) per meter of fuselage length - lets call that 20% more seats per meter of Cabin length.

That would mean NMA-6 would be shorter than A321 to get 5-10% more seats. An A321 is 44.5M in Length - call it three rows less (20 seats) or 2.5M less - NMA-6 would be about 42M in length.

Say NMA -7 was 20% bigger than that. or 40 seats more - call it 6-7 rows or about 5-6M for a length of about 48-49M. An NMA-8 about 54-55M - which all seems fine.

I would guess an A322 would be about 49-50ishM.

An A220-300 is 39M with an A220-500 possibly around 43-44M and no one seems that is impossible - the fact it's Carbon might help.
An 757-300 is 54M

It all seems reasonable/doable to me.
 
DenverTed
Posts: 243
Joined: Wed Mar 27, 2019 11:12 pm

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 1:10 am

morrisond wrote:

I think a better way to look at it would be start with an A321 and figure it out from there.

Supposedly NMA-6 is 5-10% bigger than A321 - as it would probably have one more seat in width (or 16.7% more Y seats and 50% more Premium seats) per meter of fuselage length - lets call that 20% more seats per meter of Cabin length.

That would mean NMA-6 would be shorter than A321 to get 5-10% more seats. An A321 is 44.5M in Length - call it three rows less (20 seats) or 2.5M less - NMA-6 would be about 42M in length.


I agree that the baseline of A321 plus 10% is the most relevant. If a 34 row x 6w A321 is 204 seats, a 32 row x 7w 797 is 224 seats, and that is 10%. I think that is about the two class density Airbus is quoting, so Boeing has to stick with that for comparison, whether it is real world average or not. With the extra width and taper, I could see the 797-6 at 45m, which would put the -7 at 51m.

In the reality of more common densities, a two class A321 is 191 seats, the -6 would seat 210, the -7 would seat 248. Going: baseline, plus 10%, plus 30%.
 
RJMAZ
Posts: 1529
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 1:13 am

morrisond wrote:
[Hi RJMAZ,

I think where a lot of the confusion is with the fact that 767 Capacities are usually quoted with long haul seating. NMA capacities seem to be quoting shorter haul 2 class capacity.

100% incorrect. This is bloody frustrating as you just wasted your time posting all of that. If you actually checked the 767 uses the narrowbody standard for the two class seating with business class recliners.

The 787 and 777 uses the lie flat beds for the two class standard.

I said this a week ago in this thread. I shouldn't have to keep reminding people every page.

The 767 ACAP even has graphics showing the cbin layout. The recliner seats are three rows of 2-2-2 with 38inch pitch.

It is hard to debate people in here when they get the basics wrong.

The 767-200 for example seats the following:
290 in 8ab in 1 class.
245 in 7ab in 1 class with 31inch pitch
216 in 2 class with recliners
174 in 3 class with three rows of 2-1-2 beds at 60inch pitch. Seven rows of 2-2-2 recliners at 38inch pitch.

The 767-300 is:
351 seats in 8ab 1 class
290 seats in 7ab 1 class
261 seats in 2 class with recliners.
210 seats with 3 class beds, recliners and economy.

Now the narrowbody uses the two class with recliners standard. The 797 numbers of 228 and 267 seats are two class with recliners. Both are higher than the 767-200 and 767-300. The 797-6 cabin will need to be a couple metres longer than the 767-200 and the 797-7 will need a cabin maybe 1 metre longer than the 767-300.

As i said before the 797-8 will be a pencil if it is an reduced height 7ab. If the 797-7 is already one row longer than the 767-300 the 797-8 will be approachinf the length of the 767-400. Now imagine the 767-400 with a reduced fuselage height similar to a narrowbody. Here is a picture:

Image

This is what it will look like. Yet the boeing rendering shows a stubby plane pointing to an 8ab aircraft.
 
morrisond
Posts: 1179
Joined: Thu Jan 07, 2010 12:22 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 2:19 am

So compare it to the A321 228 is 10% more than what they quote for 2 class at 208. My answer might be right as well.

What lengths do you get if you start with an A321 Cabin?

Boeing might be assuming a lot tighter pitch on Y on the 797.
 
RJMAZ
Posts: 1529
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 2:44 am

morrisond wrote:
So compare it to the A321 228 is 10% more than what they quote for 2 class at 208. My answer might be right as well.

What lengths do you get if you start with an A321 Cabin?

Boeing might be assuming a lot tighter pitch on Y on the 797.

We are talking about Boeing.

The 737 is 13%. So the 767 seats are exactly the same standard as the 737 at 13%.
 
morrisond
Posts: 1179
Joined: Thu Jan 07, 2010 12:22 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 3:30 am

RJMAZ wrote:
morrisond wrote:
So compare it to the A321 228 is 10% more than what they quote for 2 class at 208. My answer might be right as well.

What lengths do you get if you start with an A321 Cabin?

Boeing might be assuming a lot tighter pitch on Y on the 797.

We are talking about Boeing.

The 737 is 13%. So the 767 seats are exactly the same standard as the 737 at 13%.


What does 13% mean?

Look at a typical A321 vs 767 layout. Most 767's waste a lot more space on Galleys and Lav's - a 797 will probably be a lot more efficient and like the A321.
 
RJMAZ
Posts: 1529
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 4:24 am

morrisond wrote:
[What does 13% mean?

Look at a typical A321 vs 767 layout. Most 767's waste a lot more space on Galleys and Lav's - a 797 will probably be a lot more efficient and like the A321.

13% more seats in the 1class versus 2 class.

Please read the 767 ACAP before writing. There is hardly any space wasted in the 767 seat map. The toilets and galleys are at the very front and back of the plane where you can not fit seats.

There are two tiny toilets half way down cabin. Hardly wasted space.

This is getting ridiculous.
 
FluidFlow
Posts: 238
Joined: Wed Apr 10, 2019 6:39 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 5:06 am

RJMAZ wrote:
FluidFlow wrote:
B797-5 35.6 4.45 8 200
B797-6 40.05 4.45 9 240
B797-7 44.5 4.45 10 280
B797-8 48.95 4.45 11 320

Your numbers and lengths are way off. The two class 797 seating numbers of 228 and 267 are fractionally higher than the 767-200 (214) and 767-300 (261). I'm not sure how your lengths could then be less than the 767 as they are both 7ab.

Your seating numbers for the 797-6 and 797-7 are even smaller than the 757.

The numbers for a 7ab cross section would then be:
B797-5 44 4.45 9.88 220
B797-6 49 4.45 11.01 260
B797-7 55 4.45 12.35 305
B797-8 60. 4.45 13.48 350

That is one skinny plane.


The -6 is bigger than the 757-200 and the -7 actually bigger then the 757-300. And this numbers are one class seatings. And as you see I used generic ratios to extrapolte the length. You can always play around to fit a row or two more into the aircraft by lengthening a bit. The 767 by the way could have a way denser layout if you remove certain galleys and toilets. The 797 will optimize space way more so a single class 797 will sit more than the same length 767.

And this are just numbers games, but your numbers make no sense, as your 797-6 would need 6 FA. If you want the aircraft to be optimized your -6 is only allowed to sit 250 in high density config. The MoM has to be really good otherwise the A321 will ruin the show. The reason the 737-9 is so outsold by the A321 is because a seating of 220 is not optimal, as soon as you go over 200 you better go towards 250. Thats why the 797-5 in your option will not work and the -7 is a bit too big as well. On top of that aerodynamically only a three model family makes sense otherwise you need to modify the tail section or compromise a lot on efficiency.

If you really want to build a 797 with up to 350 seats you have to go 8ab. The skin drag on that tube would offset every benefit of new engines. The real thing Boeing is probably thinking about is if the 797 should cover the 250-300 segment or the 300-350. If you go the full spec from 250-350 you have at least at one end a really inefficient aircraft. Thats what happened to the 767, in the upper end it was so inefficient that the A330 killed it off and in the lower end the 757 was the better choice for many airlines. So if Boeing goes from 250-350 the A321 will push the lower end hard and Airbus has an opening at the upper end. Therefore Boeing needs to choose if they want to be efficient in the 250-300 range with 7ab (or even 6ab like the 757) or go for the upper end with 8ab. Being efficient in both is not possible.
 
RJMAZ
Posts: 1529
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 5:44 am

FluidFlow wrote:
And this are just numbers games, but your numbers make no sense, as your 797-6 would need 6 FA. If you want the aircraft to be optimized your -6 is only allowed to sit 250 in high density config

The numbers are actually perfect.

The 797-6 is near perfect for 250 seats with 32inch pitch in a single class.
The 797-7 near perfect for 300 seats with 31inch pitch in a single class.

Remember the A321 is 240 seats at 28inch pitch and only two lavs. Jetstar for instance has 220 seats in the A321 with at 29inch pitch and 230 seats at 28inch pitch. So really it is the A321 that is not maximising the flight attendant ratio for low cost carriers.

The 767-300 is 261 seats in 2 class with narrowbody standard recliners and 290 seats in 1 class with 7ab. The 797-7 number we have is 267 seats with 2 class. That is 6 more seats than the 767-300. So if the 767-300 sits 290 in 1 class then the 797-7 will sit dead on 300 passengers with the average seat pitch and average number of toilets. Sure an ULCC could cram in 320 seats into the 797-7 with 28inch pitch and less toilets but it is sized for the average LCC customer.

The 767-200 seats 216 in 2 class and 245 in 1 class with 31inch pitch. Now the 797-6 is 228 seats in 2 class. That works out to be 258 seats in one class going off the 767 numbers with 31inch pitch. Increase the pitch to 32inch and you'll bring it down to 250 seats.

I actually think the 797-7 at 300 seats will be the aircraft often used on shorter trunk routes and will be more likely to see a single class cabin with low cost carriers such as AirAsiaX.

The 797-6 will have worse CASM with the only advantage being greater range. I then expect it to be the point to point route opener and due to the longer flights I expect it to have 2 class and 3 class cabins on most aircraft. So being slightly over 250 seats with LCC pitch should not be an issue. I would expext the 797-6 to often have below 200 seats with a premium cabin.
 
FluidFlow
Posts: 238
Joined: Wed Apr 10, 2019 6:39 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 6:16 am

RJMAZ wrote:
FluidFlow wrote:
And this are just numbers games, but your numbers make no sense, as your 797-6 would need 6 FA. If you want the aircraft to be optimized your -6 is only allowed to sit 250 in high density config

The numbers are actually perfect.

The 797-6 is near perfect for 250 seats with 32inch pitch in a single class.
The 797-7 near perfect for 300 seats with 31inch pitch in a single class.

Remember the A321 is 240 seats at 28inch pitch and only two lavs. Jetstar for instance has 220 seats in the A321 with at 29inch pitch and 230 seats at 28inch pitch. So really it is the A321 that is not maximising the flight attendant ratio for low cost carriers.

The 767-300 is 261 seats in 2 class with narrowbody standard recliners and 290 seats in 1 class with 7ab. The 797-7 number we have is 267 seats with 2 class. That is 6 more seats than the 767-300. So if the 767-300 sits 290 in 1 class then the 797-7 will sit dead on 300 passengers with the average seat pitch and average number of toilets. Sure an ULCC could cram in 320 seats into the 797-7 with 28inch pitch and less toilets but it is sized for the average LCC customer.

The 767-200 seats 216 in 2 class and 245 in 1 class with 31inch pitch. Now the 797-6 is 228 seats in 2 class. That works out to be 258 seats in one class going off the 767 numbers with 31inch pitch. Increase the pitch to 32inch and you'll bring it down to 250 seats.

I actually think the 797-7 at 300 seats will be the aircraft often used on shorter trunk routes and will be more likely to see a single class cabin with low cost carriers such as AirAsiaX.

The 797-6 will have worse CASM with the only advantage being greater range. I then expect it to be the point to point route opener and due to the longer flights I expect it to have 2 class and 3 class cabins on most aircraft. So being slightly over 250 seats with LCC pitch should not be an issue. I would expext the 797-6 to often have below 200 seats with a premium cabin.


I think we discuss here about the same issue for no reason as I agree with you. So you expect Boeing to build a product for the 250-300 market what is really interesting, I expected them to go for the upper part of the MoM of 300-350. In my eyes it is easier to establish a product in a segment where there is no competition than go straight up against an established product. See 737-9/10 vs A321 or A350 vs 787 and 777.
 
VV
Posts: 791
Joined: Sat Feb 13, 2016 1:03 pm

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 6:30 am

Rolls-Royce is not anymore in the engine selection process.

Is Boeing going to choose only one engine or will there be two engines on the program?
 
RJMAZ
Posts: 1529
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 6:55 am

FluidFlow wrote:
I think we discuss here about the same issue for no reason as I agree with you. So you expect Boeing to build a product for the 250-300 market what is really interesting, I expected them to go for the upper part of the MoM of 300-350. In my eyes it is easier to establish a product in a segment where there is no competition than go straight up against an established product. See 737-9/10 vs A321 or A350 vs 787 and 777.

I expect the 797-8 to cover up to 350 seats in single class.

The problem people have here are they don't often see single class seating numbers on widebody aircraft. They think 350 seats in a 797 is way too big but they don't realise an A330-200 can fit 400 passengers and the A330-300 can fit 440 passengers in single class. The 787-8 has a theoretical max seating of 381.

The 797-6 and 797-7 in terms of 1 class seating is about 44 seats apart if we scale off the 767 numbers. That is using Boeing's narrowbody standard seating. We could then assume 797-8 is also 44 seats bigger than the 797-7.

So that is 258 and 302 seats for the 797-6/7 in single class and 346 seats for the 797-8. Now this is hard to dispute as we have the 797 seating numbers and we know the Boeing standard for seating.

At 346 seats in 1 class it is hard to believe it will be a reduced height 7ab.

The 7ab 797 would then need:
49m, 55m and 61m fuselage lengths for the -6 -7 and -8. With a 4m high reduced height fuselage that is really skinny!!

The 8ab 797 would need:
46m, 51m and 56m lengths. This produced a perfect fineness ratio and matches Boeing's rendering. With a 4.3m high fuselage that spot on for structural efficiency.

The 8ab 797-8 at 56m would effectively have the same length as the 787-8 but would be one less seat in the width. So 88% of the capacity of the 787-8. That is not too big. Frontal area with the reduced height would be about 75% of that of the 787.

Remember the 787 was originally sold as an 8ab aircraft. We might see the 797 being sold as a comfortable 7ab aircraft but it ends up being fitted with 8ab with every airline.
 
FluidFlow
Posts: 238
Joined: Wed Apr 10, 2019 6:39 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 7:03 am

RJMAZ wrote:
FluidFlow wrote:
I think we discuss here about the same issue for no reason as I agree with you. So you expect Boeing to build a product for the 250-300 market what is really interesting, I expected them to go for the upper part of the MoM of 300-350. In my eyes it is easier to establish a product in a segment where there is no competition than go straight up against an established product. See 737-9/10 vs A321 or A350 vs 787 and 777.

I expect the 797-8 to cover up to 350 seats in single class.

The problem people have here are they don't often see single class seating numbers on widebody aircraft. They think 350 seats in a 797 is way too big but they don't realise an A330-200 can fit 400 passengers and the A330-300 can fit 440 passengers in single class. The 787-8 has a theoretical max seating of 381.

The 797-6 and 797-7 in terms of 1 class seating is about 44 seats apart if we scale off the 767 numbers. That is using Boeing's narrowbody standard seating. We could then assume 797-8 is also 44 seats bigger than the 797-7.

So that is 258 and 302 seats for the 797-6/7 in single class and 346 seats for the 797-8. Now this is hard to dispute as we have the 797 seating numbers and we know the Boeing standard for seating.

At 346 seats in 1 class it is hard to believe it will be a reduced height 7ab.

The 7ab 797 would then need:
49m, 55m and 61m fuselage lengths for the -6 -7 and -8. With a 4m high reduced height fuselage that is really skinny!!

The 8ab 797 would need:
46m, 51m and 56m lengths. This produced a perfect fineness ratio and matches Boeing's rendering. With a 4.3m high fuselage that spot on for structural efficiency.

The 8ab 797-8 at 56m would effectively have the same length as the 787-8 but would be one less seat in the width. So 88% of the capacity of the 787-8. That is not too big. Frontal area with the reduced height would be about 75% of that of the 787.

Remember the 787 was originally sold as an 8ab aircraft. We might see the 797 being sold as a comfortable 7ab aircraft but it ends up being fitted with 8ab with every airline.


Do you think a slimmed down A300 (the new 8ab 797-6 you propose) with limited cargo compete with the A321 or in worst case an upgraded A321(322) or would it not just be better for Boeing to skip that aircraft at all and only go for the -7 and -8 then? I cannot see how the -6 would be in anyway more economical to open routes than the A321(XLR if needed).
 
User avatar
seahawk
Posts: 8521
Joined: Fri May 27, 2005 1:29 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 7:05 am

Thanks for the number,s it is obvious that this will be a huge winner. I can not wait for Boeing to launch.
 
User avatar
keesje
Posts: 13045
Joined: Thu Apr 12, 2001 2:08 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 7:26 am

Any idea about the empty weights.

The composites 787 has the same empty weight as the A330.

Boeing said they avoid technical challenging technology.

A 7 abreast 767-200 weighs 80-81t, a single aisle 757-200 58t.

Image
https://theblogbyjavier.com/2010/03/13/ ... t-in-gold/
"Never mistake motion for action." Ernest Hemingway
 
RJMAZ
Posts: 1529
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 7:41 am

FluidFlow wrote:
Do you think a slimmed down A300 (the new 8ab 797-6 you propose) with limited cargo compete with the A321 or in worst case an upgraded A321(322) or would it not just be better for Boeing to skip that aircraft at all and only go for the -7 and -8 then? I cannot see how the -6 would be in anyway more economical to open routes than the A321(XLR if needed).

The A300 is a comfortable 8ab and a very tight 9ab.
The 767 is a comfortable 7ab and a very tight 8ab.

I expect the 797 to be a slightly tight 8ab, but still comfortable enough that all airlines fit 8ab. This requires a cabin width roughly half way between the 767 and A300.

The A300 is larger than the 767-300 in terms of cabin area 190m2 vs 215m2. I expect the 8ab 797-7 to be the same cabin area as the smaller 767-300 with the more space efficient 8ab giving the dozen extra seats.

I expect the 797-6 to be a metre or so longer than the A310. I expect the 797-7 to be a metre or so shorter than the A300.

Of course the longer 797-8 will have the best CASM but that is the case with most stretchs. It will have significantly less range definitely below 4000nm. Having good CASM is only a part of the 797's business case. Being the smallest aircraft capable of 5000nm is very significant in terms of opening new point to point routes. The 787 is just the tip of the iceberg in terms of the point to point market.

We often see 787's flying with less than 200 seats on long haul routes with a premium 3 class cabin. This density on the 797-6 would see as few as 150 seats. Range of such a payload would probably exceed 5500nm and this allows many transpacific destinations. The sales of such a model might actually be quite high if the trend of point to point routes continue.
 
Armadillo1
Posts: 409
Joined: Thu Apr 20, 2017 5:14 pm

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 7:45 am

so all topic going to desision new small point-to-point plane will be wide "long haul" NB (707-340 range class)
 
FluidFlow
Posts: 238
Joined: Wed Apr 10, 2019 6:39 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 7:58 am

RJMAZ wrote:
FluidFlow wrote:
Do you think a slimmed down A300 (the new 8ab 797-6 you propose) with limited cargo compete with the A321 or in worst case an upgraded A321(322) or would it not just be better for Boeing to skip that aircraft at all and only go for the -7 and -8 then? I cannot see how the -6 would be in anyway more economical to open routes than the A321(XLR if needed).

The A300 is a comfortable 8ab and a very tight 9ab.
The 767 is a comfortable 7ab and a very tight 8ab.

I expect the 797 to be a slightly tight 8ab, but still comfortable enough that all airlines fit 8ab. This requires a cabin width roughly half way between the 767 and A300.

The A300 is larger than the 767-300 in terms of cabin area 190m2 vs 215m2. I expect the 8ab 797-7 to be the same cabin area as the smaller 767-300 with the more space efficient 8ab giving the dozen extra seats.

I expect the 797-6 to be a metre or so longer than the A310. I expect the 797-7 to be a metre or so shorter than the A300.

Of course the longer 797-8 will have the best CASM but that is the case with most stretchs. It will have significantly less range definitely below 4000nm. Having good CASM is only a part of the 797's business case. Being the smallest aircraft capable of 5000nm is very significant in terms of opening new point to point routes. The 787 is just the tip of the iceberg in terms of the point to point market.

We often see 787's flying with less than 200 seats on long haul routes with a premium 3 class cabin. This density on the 797-6 would see as few as 150 seats. Range of such a payload would probably exceed 5500nm and this allows many transpacific destinations. The sales of such a model might actually be quite high if the trend of point to point routes continue.


I still cannot see how the -6 is in anyway efficient and can beat the A321. There is only one way to do this: The 797 is designed for the -6 size and then streched twice for the -7 and -8. This makes the especially the -8 a prime target to compete for Airbus as it is really inefficient and the -6 has to prove to be more economical than a 140 seat 3class A321 XLR. This will be a difficult task due to the extra weight and drag that will need to be compensated for with the new engine. On top of that the wing will be designed for the -6 and long range. This makes the design inefficient on <3000nm routes, even more for the -7 and -8. A really risky business case, because you compete vs an old design (that will sooner than later be replaced with a new design) and you are limited upwards due to a too small initial design (see the first iteration of the A350)
On the other side if the aircraft is designed around the -7 size, the -6 will be in the same category as the A319 and the B737-7 and will suffer the same fate. Nice but not commercially viable.

We can clearly see it with past designs. If you over design the (smallest) base version (A330-800, B787-8, etc.) the stretches will take over and the base version is not economically viable in the long run. If you design for the middle version, a shortening is a huge compromise and ends up a "dead" design (737-7, A319).
 
RJMAZ
Posts: 1529
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 8:42 am

FluidFlow wrote:
On top of that the wing will be designed for the -6 and long range. This makes the design inefficient on <3000nm routes, even more for the -7 and -8.

Actually it makes all designs of the 797 efficient. So you got it backward.

Long haul aircraft you want a better lift to drag ratio than a short haul aircraft. Long range aircraft will generally have a bigger wing.

Short haul aircraft you want a lighter empty weight per passenger. A stretch like the 787-10 gains a larger percentage of cabin area over the 787-9 than it does in empty weight.

The 797 if it shares the same MTOW will result in the 797-6 having the best lift to drag ratio this is exactly what you want for the longer ranged model. The 797-8 will have the largest cabin area with relatively small weight gain this is exactly what you want for a short ranged model.

The A321XLR is the exact opposite of what you want. The largest stretch is also the longest range model in the family. This results in an overworked work and a poor initial cruise altitude and increased fuel burn.

On a 10 hour flight the A321LR has a very low initial cruise altitude of 29,000ft. With the 797-6 its wing will be sized for a future 797-8 model. So the larger wing will be allow it the 797-6 to 5,000+ft higher than the A321 for the first half of the 10 hour flight. This should offset or even allow the 797-6 to beat the A321XLR.

If you need proof of this is the 787-8 has a really high initial cruise altitude as it has the best lift to drag ratio in the family as it has the the same large wing (lift) but the shortest fuselage (drag).
 
User avatar
seahawk
Posts: 8521
Joined: Fri May 27, 2005 1:29 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 8:51 am

And that is why the 797 will eat the A321 for lunch. The superior wing design of Boeing will add to this, especially when compared to the outdated wing of the A321.
 
Amiga500
Posts: 2267
Joined: Tue Mar 03, 2015 8:22 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 9:11 am

VV wrote:
Rolls-Royce is not anymore in the engine selection process.

Is Boeing going to choose only one engine or will there be two engines on the program?


Market isn't big enough to justify two dedicated designs (or two dedicated iterations to existing designs).
 
RJMAZ
Posts: 1529
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 9:12 am

Lots of people think the 797-6 will be dead of arrival. But the 797-6 and 797-7 are closer in size than people think. Their performance will not be that difference one will have slightly greater range, the other slightly better CASM.

The 757-200/300, 767-200/300 and 777-200/300 are further apart in size than the two 797 sizes.

An airline will probably buy both 797 sizes and simply mix the aircraft. If an airline is a 737 operator it might be difficult to justify a small A321XLR purchase for a narrow 3500/4700nm range window. The 797-6 can then be the route opener for new routes over 3500nm as it has the least capacity risk. It is also needed to fly the routes over 4500nm as the 797-7 does not have the range.

I expect a large number of 767 and A330CEO operators to order the 797. They will downgauge routes accordingly and add extra destinations to spread out the passengers to where they want to go.

It is not all about the 797-7 model. It could go either way which model sells the best. The whole idea that there is a range "sweet spot" means the 797-6 might hit the range to allow it to replace most widebodies.
 
FluidFlow
Posts: 238
Joined: Wed Apr 10, 2019 6:39 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 9:13 am

RJMAZ wrote:
FluidFlow wrote:
On top of that the wing will be designed for the -6 and long range. This makes the design inefficient on <3000nm routes, even more for the -7 and -8.

Actually it makes all designs of the 797 efficient. So you got it backward.

Long haul aircraft you want a better lift to drag ratio than a short haul aircraft. Long range aircraft will generally have a bigger wing.

Short haul aircraft you want a lighter empty weight per passenger. A stretch like the 787-10 gains a larger percentage of cabin area over the 787-9 than it does in empty weight.

The 797 if it shares the same MTOW will result in the 797-6 having the best lift to drag ratio this is exactly what you want for the longer ranged model. The 797-8 will have the largest cabin area with relatively small weight gain this is exactly what you want for a short ranged model.

The A321XLR is the exact opposite of what you want. The largest stretch is also the longest range model in the family. This results in an overworked work and a poor initial cruise altitude and increased fuel burn.

On a 10 hour flight the A321LR has a very low initial cruise altitude of 29,000ft. With the 797-6 its wing will be sized for a future 797-8 model. So the larger wing will be allow it the 797-6 to 5,000+ft higher than the A321 for the first half of the 10 hour flight. This should offset or even allow the 797-6 to beat the A321XLR.

If you need proof of this is the 787-8 has a really high initial cruise altitude as it has the best lift to drag ratio in the family as it has the the same large wing (lift) but the shortest fuselage (drag).


If the -6 wing is designed for long range, that means it is bigger and heavier than needed for all the routes <3000nm. This means the -6 will be a real niche product that can only be used on really long thin routes. That is fine but it is hardly a business case as you can see with the 787-8. It also increases the OEW for no real benefit. On the -7 said wing will be good. It will be the perfect balance and therefore the -6 has no business case. Especially if over time the engine PIPs and eventual MTOW bumps will increase the range of the -7. This will kill the -6 outright. Now while the wing will be a good fit for the -8 the tail section will be of the wrong dimension. Keep in mind the tail section will be dimensioned for the wing and fuselage length of the -6. This leads to extreme high H-stab authority on the -8. You can see this already for the A321. It is a rather "pitchy" aircraft as seen by the EASA AD, and on the other hand the B737-10 that will not need MCAS because the H-Stab has enough authority to prevent the sh*t show seen on the B737-8.

Boeings goal is to bring a super lean MoM Aircraft that is "cheap" and does not need too much new technic upgrades over current aircraft (as said by Boeing) to gain a massive advantage over existing aircraft, and also be competitive 10-15 years after EIS it has to be designed narrow, so only 1-2 versions. All currently sold aircraft model ranges have only one or two really good selling versions (B787-9/10, A320/321, B737-8, A350-9 and soon -10, etc.) while the other family members are niche if not even outright gone.

Therefore Boeing should and hopefully will design the aircraft into the narrow gap of the MoM with a two model version, either a -6/-7 or the -7/-8. This will be really hard to beat for any other manufacturer. If you go broad you kill off one of your own models or a product of another manufacturer will just fit at least one of the specs better.
 
Amiga500
Posts: 2267
Joined: Tue Mar 03, 2015 8:22 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 9:23 am

RJMAZ wrote:
FluidFlow wrote:
On top of that the wing will be designed for the -6 and long range. This makes the design inefficient on <3000nm routes, even more for the -7 and -8.

Actually it makes all designs of the 797 efficient. So you got it backward.


No, he doesn't have it backward.

The 797-6 (BTW why are we not starting with traditional -200, -300 and -400 instead of this new MBA driven daft naming?) would not be able to compete with A321 over mission lengths < 3000 nm. That is a given.

The 797-7 may be competitive, but then as we have observed, unless airlines need the range (that I assume a -7 will provide over XLR) then they will go for the smaller, better yielding aircraft. So the -7 needs to offer a sizeable range advantage over A321 without being too big.

The 797-8 absolutely has to be [i]significantly[/i ]better on a CASM basis, because if its not, then A321 will win on RASM and the whole thing is surviving solely on the range niche offered by the -6 (and lesser extent -7)..


[Also; extrapolating the logic of airlines by and by large picking the smaller aircraft (of approx equivalent CASM) that can do the mission for RASM reasons - if the 797-6 flies too far then the manufacturer who stands to lose the most is... Boeing. on the 787.]
 
RJMAZ
Posts: 1529
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 10:02 am

FluidFlow wrote:
Therefore Boeing should and hopefully will design the aircraft into the narrow gap of the MoM with a two model version, either a -6/-7 or the -7/-8.

Boeing will definitely optimise the 797 for the -6 and -7.

The 797-8 would most likely come a decade later once engine PIP's, extra thrust, aero tweaks and MTOW bumps come. I only mention the 797-8 as it must be part of the long term planning. The optimal cross section 7ab or 8ab must take into account this future stretch. With a 7ab cross section it makes it hard for the 797 to grow to the 797-8 capacity.

The sales of the 797-6 will probably slow down once the 797-7 gains range like we have seen in the past. Most members expect the 787-9 and 787-10 to gather most future sales.
 
User avatar
Pudelhund
Posts: 187
Joined: Tue Jan 15, 2019 11:06 pm

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 10:15 am

2175301 wrote:
I have refrained from posting for a few days; and would like to give my opinion at this point on some of the issues raised and debate on this forum:

1) I generally agree with the point that a certain poster was clearly showing (up to that point) a highly negative view and had proposed a whole collection of individually different possibilities; many of which were not plausible given the history and what was known; and could understand why some would see that overall as trolling. It appears to me that individual poster has become more focused and realistic since. I'd like to thank them for that improvement.

2) I agree with that Boeing has not told us what the 797 actually will be, except that its ovid, does not push technology, is focused on manufacturability, focuses on passengers and minimizes extra cargo (no claims that is uses existing containers - any modeling by anyone using and existing container assumption is in my opinion is likely wrong), and is targets to a middle of market target segment. There are strong hints or indications that it seats 7 wide with 2 isles.

Anyone who knows more has signed a NDA and it appears that the NDA has held (no real leaks). A lot of Airline Executives, who have signed such NDA's, have said that they are excited about what Boeing is proposing.

3) I agree with astuteman that there are no long term manufacturing competitive advantages. However, I believe that in this industry there can be short term 5-10 years manufacturing advantages by changes in technology and approach. IF Boeing pulls off what they say the are planning to do in regards to the cost of manufacturing a commercial airliner; it may realistically give Boeing a 5-10 year advantage in the market that they apply it too. Since the MOM market size is not expected to be huge... The proposed 797 will likely end up owning the market segment IF Boeing pulls it off because Airbus will not be able to effectively and economically enter it in a timely manner. In my opinion, that actually reduces the gamble on Boeing's part.

4) I disagree with the concept that the NMA and NSA will share major components (other than perhaps flight deck layout and instruments for possibly a common type rating). My opinion, and my sources, indicate that the NSA concepts are for a much different aircraft; and what Boeing is counting on from the NMA is a refined and fleshed out new manufacturing/procurement strategy that will give the NSA a huge cost advantage over current existing aircraft in the NSA size range. I expect that the NSA will likely be a robust (but not extreme) technology push - using a substantially proven NMA manufacturing/procurement method.

5) I have personally avoided the debates on what is the potential layouts as it is my understanding that Boeing has already worked out what they are offering - in detail - on at least the 1st variant of the proposed 797. I see no reason not to just wait and see what comes out when it is offered for sale. Apparently a lot of airlines are very excited about their detailed concept. Why debate something already decided.

6) It is my understanding from both my source and also released by other sources that the 797 program is sufficiently advanced that they were ready to ask the Board of Directors earlier this year for permission to offer it for sale, that it had passed a key engineering and manufacturing review point: far more advanced than previous projects (lessons learned) - and is near if not at design freeze. That it was not offered for sale (and not part of a major airshow) only because of the 737Max8 issue; which to me is very understandable. I personally do not understand people who keep criticizing Boeing for continuing delays, when their strategy of performing far more engineering and design work up front before program approval has been discussed many times (different than past programs that went astray and damaged their reputation).

Their plans were to offer for sale in 2019, and then if enough orders materialize; authorize full program launch (production) in 2020. My information is that all of that was on track before the 737Max8 issues, and yet could still happen. Boeing has previously used the Offer for sale 1st, and not authorize production unless sufficient sales before; although its been a while (and not on the 787). I take that as one of the lessons learned from the more recent aircraft developments (along with advanced design and modeling up front before even offering for sale).

The 2025 delivery is still possibly plausible; but, may be affected by the 737Max8 issue. In my opinion likely no more than 1 year. It is clear to me from what information I have that the FAA is changing their approval process to ensure an independent 3rd party review of the Failure Modes and Effects Analysis (FMEA); and that in general all companies will need to apply more focus on the FMEA's in the future.

Have a great day,


This is the best post in this thread as of late. Thank you for your input.
 
FluidFlow
Posts: 238
Joined: Wed Apr 10, 2019 6:39 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 10:32 am

RJMAZ wrote:
FluidFlow wrote:
Therefore Boeing should and hopefully will design the aircraft into the narrow gap of the MoM with a two model version, either a -6/-7 or the -7/-8.

Boeing will definitely optimise the 797 for the -6 and -7.

The 797-8 would most likely come a decade later once engine PIP's, extra thrust, aero tweaks and MTOW bumps come. I only mention the 797-8 as it must be part of the long term planning. The optimal cross section 7ab or 8ab must take into account this future stretch. With a 7ab cross section it makes it hard for the 797 to grow to the 797-8 capacity.

The sales of the 797-6 will probably slow down once the 797-7 gains range like we have seen in the past. Most members expect the 787-9 and 787-10 to gather most future sales.


I wonder how the pilots will be contracted. They will probably earn way more on the 797 than the A321. This will be factored in aswell. I cannot see why an airline that uses A320 as of now would go 797-6 and -7 if it has your suggested specs and not outright go A321 XLR and 797-7. If you wanna go long and thin the A321 is great and you can do short cycles between long cycles if needed. It is probably possible to do MAN-BOS-MAN-DUB-MAN with a two class A321 while the same with a 797-6 will be not optimal at all also regarding crew cycles.

For the 7ab 797-7 to be a success it should be optimized for <=3000nm and be initially able to do 4500nm. This would be the ideal aircraft. In low density it will be good for TATL and in high density to haul lots of pax to the common holiday destinations. With MTOW and efficiency increases the -8 will be able to do the same distances with more pax a few years later. The bulk of sold 797 will be used for the high pax possibility and not the max possible range and there is in my eyes no need to design the aircraft to be efficient over 5500nm because most flights will be <4000nm. East coast TATL from the common hubs of UA, DL(JFK) and AA will not need more than 4000nm. So longer routes should not be the design goal even if they will be possible in the future.
 
User avatar
keesje
Posts: 13045
Joined: Thu Apr 12, 2001 2:08 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 11:08 am

FluidFlow wrote:
Boeings goal is to bring a super lean MoM Aircraft that is "cheap" and does not need too much new technic upgrades over current aircraft (as said by Boeing) to gain a massive advantage over existing aircraft, and also be competitive 10-15 years after EIS it has to be designed narrow, so only 1-2 versions. All currently sold aircraft model ranges have only one or two really good selling versions (B787-9/10, A320/321, B737-8, A350-9 and soon -10, etc.) while the other family members are niche if not even outright gone.

Therefore Boeing should and hopefully will design the aircraft into the narrow gap of the MoM with a two model version, either a -6/-7 or the -7/-8. This will be really hard to beat for any other manufacturer. If you go broad you kill off one of your own models or a product of another manufacturer will just fit at least one of the specs better.


Amiga500 wrote:
The 797-6 (BTW why are we not starting with traditional -200, -300 and -400 instead of this new MBA driven daft naming?) would not be able to compete with A321 over mission lengths < 3000 nm. That is a given.


I will look forward to NMA -6, -7 whatever it will be called empty weight. Knowing that OEW I will get a pretty good picture at purchasing & operating costs. I'll put aside twin aisle at NB costs as a marketing slogan. The vast majority of flights in this category are up to 2-3 hours. If a Boeing NMA can't effectively compete in that arena, because it needs to be oval, two aisle, and be able to do 280 people 5000NM also, it will become a niche aircraft, driving up cost per unit.

We can try convince each other all is set & Boeing knows exactly what it wants and look for straws (sketches, qoutes) confirming that. But in the end the market decides. Last year, even before the 737 MAX dramas, a big majority of 200 airlines indicated they wanted 150-250 seats. Ignore your customers, modify their requirements & sooner or later you hit the wall.

Image
https://aviationweek.com/awin-only/airl ... definition

United, Delta & AA need an affordable efficient 757 replacement & asked Boeing. If Boeing comes back presenting them they really want a composites oval 2 aisles, up to 320 seats, craddle to grave MRO included, those airlines will think Boeing didn't listen & order A321s soon after.

It's not that Boeing doesn't understand this, contrary, it is the reason they didn't close the business case in 2016, 2017 and 2018 and told us 2020 even before the MAX drama. There's a gab between market requirements & the aircraft Boeing has on the drawing table. The manufacturer says it has 1,000 people working on the aircraft design. That could be 10% of their jobs next to other tasks / projects. Mark Jenks leaving the 797 ship & Mike Sinnett adding it to his repsonsibilities is not an indication of increased focus.

I think Boeing should put their money where their mouth is (~175-225 seats) & then build an NMA based on that. Not the other way around. We can do without another shrink nobody wants.


Boeing’s preference for a widebody NMA has surprised many within the industry, given the popularity of the single-aisle 757 and challenge of widebody production costs. “For me, a single-aisle up to 230-250 seats is all they need, and then they get the pricing right,” says Phil Seymour, CEO of consultancy IBA.


“They’re building a twin-aisle and giving it twin-aisle capabilities yet trying to capture some of the single-aisle market—that’s an enormous challenge in terms of operating economics and production economics,” says Richard Aboulafia, vice president for analysis at the Teal Group.


https://www.mro-network.com/airframes/can-boeing-sell-nma-less-and-make-it-aftermarket
Last edited by keesje on Wed Jul 24, 2019 11:23 am, edited 2 times in total.
"Never mistake motion for action." Ernest Hemingway
 
JibberJim
Posts: 76
Joined: Tue Nov 08, 2016 1:33 pm

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 11:20 am

Amiga500 wrote:
The 797-8 absolutely has to be [i]significantly[/i ]better on a CASM basis, because if its not, then A321 will win on RASM and the whole thing is surviving solely on the range niche offered by the -6 (and lesser extent -7)..


I'm sure there is a niche for the larger aircraft - the larger LHR-west coast, but of course all of those routes are currently widebody orders so any replacement would still be sizing down for RASM (reducing number of economy seats in the back of these aircraft whilst maintaining premium capacity)
 
morrisond
Posts: 1179
Joined: Thu Jan 07, 2010 12:22 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 11:42 am

RJMAZ wrote:
FluidFlow wrote:
I think we discuss here about the same issue for no reason as I agree with you. So you expect Boeing to build a product for the 250-300 market what is really interesting, I expected them to go for the upper part of the MoM of 300-350. In my eyes it is easier to establish a product in a segment where there is no competition than go straight up against an established product. See 737-9/10 vs A321 or A350 vs 787 and 777.

I expect the 797-8 to cover up to 350 seats in single class.

The problem people have here are they don't often see single class seating numbers on widebody aircraft. They think 350 seats in a 797 is way too big but they don't realise an A330-200 can fit 400 passengers and the A330-300 can fit 440 passengers in single class. The 787-8 has a theoretical max seating of 381.

The 797-6 and 797-7 in terms of 1 class seating is about 44 seats apart if we scale off the 767 numbers. That is using Boeing's narrowbody standard seating. We could then assume 797-8 is also 44 seats bigger than the 797-7.

So that is 258 and 302 seats for the 797-6/7 in single class and 346 seats for the 797-8. Now this is hard to dispute as we have the 797 seating numbers and we know the Boeing standard for seating.

At 346 seats in 1 class it is hard to believe it will be a reduced height 7ab.

The 7ab 797 would then need:
49m, 55m and 61m fuselage lengths for the -6 -7 and -8. With a 4m high reduced height fuselage that is really skinny!!

The 8ab 797 would need:
46m, 51m and 56m lengths. This produced a perfect fineness ratio and matches Boeing's rendering. With a 4.3m high fuselage that spot on for structural efficiency.

The 8ab 797-8 at 56m would effectively have the same length as the 787-8 but would be one less seat in the width. So 88% of the capacity of the 787-8. That is not too big. Frontal area with the reduced height would be about 75% of that of the 787.

Remember the 787 was originally sold as an 8ab aircraft. We might see the 797 being sold as a comfortable 7ab aircraft but it ends up being fitted with 8ab with every airline.


And yet again you are ignoring the fact that the 767 wastes a lot of length with all those Galleys and Lav's and possibly in the nose and tail compared to modern designs. The 767 was basically designed as a mini jumbo with a ton of wasted space/length - one of the reasons the A330 wiped the floor with it. The 797 will be competing with the A321 on the bottom - they won't have the luxury of wasting all that space.

Start with an efficient space design like an A321 and add 10% more seats for 797-6(than A321) and 15% more than that for 797-7 - what lengths do you get at 7AB and 8AB? It won't make that big of a difference whether or not you assume the A321 seats 160, 180 or 208 - just add 10% and about 15% on top of that.

BTW - it's doubtful that Boeing could get an 7W that is as short as an 737 at 4.0M. A 7W would most likely have to be more like 4.2-4.3M to at least get an Ultra Wide LD3-45 in the belly.

You are also ignoring the fact that if done in Carbon the fuselage could be a lot stiffer making fineness ratios less of an issue at longer lengths.

Please look at the A220. No one seems to think that stretching it to an -500 (42-43 M with a fuselage height of 3.7M) will be that much of an issue.
 
User avatar
seahawk
Posts: 8521
Joined: Fri May 27, 2005 1:29 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 11:56 am

I would not say that the early A330 versions were much more refined when it came to using space.
 
User avatar
keesje
Posts: 13045
Joined: Thu Apr 12, 2001 2:08 am

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 12:00 pm

To make an oval 2-3-2 fuselage a bit lighter and improve cargo capability for Asia, they could make it a bit higher. Maybe using a dubble bubble to reduce loads. 8 abreast could be used for ULCC's narrowing seats and aisles.
"Never mistake motion for action." Ernest Hemingway
 
User avatar
Polot
Posts: 9377
Joined: Thu Jul 28, 2011 3:01 pm

Re: Boeing 797 Thread - 2019

Wed Jul 24, 2019 12:07 pm

seahawk wrote:
I would not say that the early A330 versions were much more refined when it came to using space.

Galley/lav space efficiency also has little to do with fuselage design. The A330 has more modern (re:smaller, more space efficient) galleys/lavs because it is still being actively sold as a passenger aircraft, and more space efficient galley/lavs so more seats can be squeezed in is what airlines want now. There is comparatively little interest in developing more space efficient galley/lavs in the 767 because most are aging out of fleets and nobody is buying new passenger ones.

The A330s payload/range is what allowed it to kill the 767, not the amount of space dedicated to galleys or lavs.

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos