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SCAT15F
Posts: 696
Joined: Fri Feb 09, 2007 8:34 am

Re: Boeing officially forms program office to flesh out 797 plans

Sun Nov 12, 2017 10:33 pm

I'm hoping for either 3-3 or a 2-2-2 that cannot be expanded to 2-3-2.

MOM sweet spot is 762 (or 752.5) per the airlines. Boeing would be better off just NEO-ing the 762 (NOT the 763) and covering the A321/752 replacement with single aisle NSA.
 
bigjku
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Re: Boeing officially forms program office to flesh out 797 plans

Sun Nov 12, 2017 10:56 pm

SCAT15F wrote:
I'm hoping for either 3-3 or a 2-2-2 that cannot be expanded to 2-3-2.


Watching someone deliberately burn billions would be fun I guess.
 
TranscendZac
Posts: 45
Joined: Sat Jun 13, 2015 12:50 pm

Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 12:02 am

SCAT15F wrote:
I'm hoping for either 3-3 or a 2-2-2 that cannot be expanded to 2-3-2.

MOM sweet spot is 762 (or 752.5) per the airlines. Boeing would be better off just NEO-ing the 762 (NOT the 763) and covering the A321/752 replacement with single aisle NSA.

I think the problem with just a re-engined 762 is you have a nearly 40 year old aircraft, i.e. heavy, and with just new engines, I’m don’t believe that’s the right answer. So much more can be optimized for an aircraft to be introduced the mid-late 2020s. I’m still unconvinced that a twin aisle aircraft is the right call. It’s a tough segment to build an aircraft for because you’re in a seat range where single aisle is at the upper limit of being efficient while also being at the lower limit of where a twin aisle is efficient. I feel Airbus has the optimal fuselage diameter for a single aisle, and not sure what the optimal is for a twin aisle.
Zac
 
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Slug71
Posts: 565
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Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 12:05 am

SCAT15F wrote:
I'm hoping for either 3-3 or a 2-2-2 that cannot be expanded to 2-3-2.

MOM sweet spot is 762 (or 752.5) per the airlines. Boeing would be better off just NEO-ing the 762 (NOT the 763) and covering the A321/752 replacement with single aisle NSA.


No way it will be 2-2-2. That configuration just makes no sense from a revenue stand point.
 
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CFM565A1
Posts: 128
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Re: Boeing officially forms program office to flesh out 797...

Mon Nov 13, 2017 12:12 am

TranscendZac wrote:
SCAT15F wrote:
I'm hoping for either 3-3 or a 2-2-2 that cannot be expanded to 2-3-2.

MOM sweet spot is 762 (or 752.5) per the airlines. Boeing would be better off just NEO-ing the 762 (NOT the 763) and covering the A321/752 replacement with single aisle NSA.

I think the problem with just a re-engined 762 is you have a nearly 40 year old aircraft, i.e. heavy, and with just new engines, I’m don’t believe that’s the right answer. So much more can be optimized for an aircraft to be introduced the mid-late 2020s. I’m still unconvinced that a twin aisle aircraft is the right call. It’s a tough segment to build an aircraft for because you’re in a seat range where single aisle is at the upper limit of being efficient while also being at the lower limit of where a twin aisle is efficient. I feel Airbus has the optimal fuselage diameter for a single aisle, and not sure what the optimal is for a twin aisle.



That’s seemed to have worked out quite nicely for the 737 family over the years. I would not be shocked if they continued the trend of the 737 but I firmly believe the 797 needs to be clean sheet.
Flown: C172-M/N/P/R/S , P2006T, PA-34-200T, Been on: ERJ-145, CRJ-100/200, DH8D, CRJ-700/705/900, E-175/190, A319/320/321, 737-200/300/400/600/700/800/900ER, MD-82/83, 757-200, 767-300, F28-4000.
 
RJMAZ
Posts: 214
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 12:26 am

SCAT15F wrote:
MOM sweet spot is 762 (or 752.5) per the airlines. Boeing would be better off just NEO-ing the 762 (NOT the 763) and covering the A321/752 replacement with single aisle NSA.

Any CASM advantage results in an exponential increase in sales. So there is a temptation to keep adding more and more improvements.

Do you spend a $1 billion on engines for the 767 to improve CASM by 10% and sell 100 aircraft?

Do you spend $3 billion on a new lighter carbon wing and engines for the 767 to improve CASM by 20% and sell 400 aircraft?

Do you spend $6 billion on a clean sheet to improve CASM by 30% and sell 1500 Aircraft?

The clean sheet is the best option with the least development cost per plane.

The 767-200 is smaller than you think. It has 160m2 of cabin area vs 127m2 of the A321. Once you take into account the extra aisle it has only 15-20% more seating area than the A321.

The half way point between the A321 and A332 is the 767-300 in terms of seating area. Going to 8 abreast allows the aircraft to be shorter. Which is why my 797 family is 46m, 52m, 58m versus the 767's 48.5, 55m and 62.5m lengths.

So cabin areas are similar but the 797 is much lighter. The longest length of the new MOM family will have the best CASM on short trips. If that model can't at least match the A321 then the primary goal of upgauging narrowbody routes cannot be achieved. For Boeing only a clean sheet can do this.

Airbus could shorten the A330 a bit and fit a tiny carbon wing with the same engines as Boeing as a response. They have the A310 wing box and landing gear designs sitting somewhere.
 
Eyad89
Posts: 242
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Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 6:09 am

RJMAZ wrote:

Wrong wrong wrong.

I am the person that made both graphics. So I can tell you now you aren't comparing similar seat density. I calculated those seat values with lower seat density than all of the narrowbody comparisons you have looked at. We're talking a lie flat business class in my graphic. No narrowbody offers this. The 797-10 being the shortest range would not require lie flat seats, but I kept density consistent across all three models.

Both widebody designs have aisles that are narrower than the A320. With 8 abreast you effectively have two 4 abreast cabins so the aisle can be narrower like a 4 abreast regional. You must calculate aisle area per seat.

With 17.5inch economy seats you are looking at two 16inch aisles on the oval 797 design vs one 22inch aisle in the A320. With 18inch wide seats the A320 has a 19inch aisle and the 797 would require tight 14inch aisles.

Let's compare with the 17.5inch seats.
797 32inch of aisle for 8 seats = 4" per seat
A320 22inch of aisle for 6 seats = 3.66" per seat

So the 797 only has 10% extra aisle area per seat, far from double. This is why 8 abreast is superior to 7 abreast options as the extra aisle is worth it.

The 797-10 has the same 45m cabin length as the A330-200 both with 8 abreast. Most A332 are fitted with a long haul cabin, where as the 797-10 would be used for short haul. Expect well over 300+ seats in the 797-10.

Now let's compare using the exact same recliner business class seats that the narrowbody aircraft use.

https://www.seatguru.com/airlines/Ameri ... 21_V3.php#

This A321 has 187 seats only 8.5% business class.
Business: 16 recliner 4 rows 21" wide, 36" pitch
Economy: 171 with 30 rows average 32" pitch

The 797-10 with 8.5% business has 350 seats
Business: 30 seats 5 rows 2-2-2, 21" wide, 36" pitch
Economy: 320 seats 40 rows with 32" pitch.

797-10: 85T with 350 seats = 242kg per seat
A321LR - 50.8T with 187 seats = 271kg per seat

As you can see the 797-10 smashes every single narrowbody made. Even a carbon fibre wing on the 737 or A321 families would not help them. Empty weight per passenger is the most important factor for short range CASM. In fact it is even more important than engine efficiency. Engine efficiency becomes the most important at much longer ranges.

Now that you can see my I am right you might try and counter saying my empty weights are too low. Look up the A300 weights. My design is 5% narrower but 8% longer cabin, so similar structural volume. So the 5% reduction comes from using composites. If anything 85T is conservative.



Allow me to borrow your phrase here, "wrong wrong wrong" :D Seriously though, allow me to correct some of the errors you made in the seats/area calculations.


You provided an example of a respectable airline and how they operate their A321 with 187 seats (16F with recliners, 18Y+, and 153Y). So far so good. That's normal, and that's what actually many A321 operators go by. That seating configurations isn't dense, they even got 16 recliners. There are other operators who go by more than 200 seats.

Then, you somehow claimed that if we used the same seating configuration as that particular A321, 797-10 would be able to seat 350 passengers !!! Wait a minute, we are not talking about an MoM anymore, that's a freaking A350/777 territory. How can an MOM seat 350 passengers in a normal configuration?

797-10 has 1 meter less in length than an A332, and they both seat 8 across. Basically, Both planes should have similar seating capacity, and NO A332 can ever seat 350 passengers unless it was 9 abreast or something similar to AirAsia. Then I realized where you made your mistake in your calculation, you didn't consider the extra lost areas of galley and lavatories in 797-10.

Narrowbodies have one area for galley/lavatories at the front and another one at the back, that's it. 797-10/A332/788 Should have FOUR. One at the front, one lies between business class and economy class, another one is located in the middle of economy cabin, and the last one would be at the very back. Those two extra areas of galley/lavatories would eat away at least 9-10 rows.

Now it makes sense, if 797-10 has the capability to seat almost the same number as A332, let's see how AA does its A332:

AA A332:
F: 20 seats, Y+: 12 seats, Y: 226 seats. That brings a total of 258 seats
AA A321:
F: 16 seats, Y+: 18 seats, Y: 153 seats
That's almost the same number of premium seats you would find on their A321. A very fair comparison IMO, same operator, almost same number of premium seats. So, it is 187 for A321 vs 258 for 797-10 when using a similar configuration. I am sorry, you just cannot go any further than that with 797-10. Sticking in 350 passengers in that frame size is just inhuman.

For similar configuration:
weight/passenger for 797-10 = 85,000/258 = 329 kg/passenger
weight/passenger for A321 = 48,500/187 = 259 kg/passenger

Again, the A321 has an advantage of 27%.

Note: why are you using the weight of the heavier A321LR here? it is a discussion of the current best narrowbody vs 797-10 in terms of weight/passenger, and A321 has an OEW of 48.5t

I am sorry, it just doesn't work. It is not only that widebodies have more dead weight in terms of one extra aisle and extra areas for galley and lavatories, it is just that the curve of weight vs passengers increases exponentially after some point. When we add more passengers, we don't only make the fuselage heavier, we also have to add more weight to the wings, engines, landing gear, etc. Your statement of "a widebody with the economics of a narrowbody" just cannot be true in my opinion.

Notice how we haven't even discussed weight/passenger for an A322 so far that should easily beat that of A321. We have not even discussed the possibility of Boeing designing a clean sheet narrowbody and equivalent to A322 that is made completely of CFRP.
 
RJMAZ
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Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 11:57 am

Eyad89 wrote:
Allow me to borrow your phrase here, "wrong wrong wrong" :D Seriously though, allow me to correct some of the errors you made in the seats/area calculations.


You provided an example of a respectable airline and how they operate their A321 with 187 seats (16F with recliners, 18Y+, and 153Y). So far so good. That's normal, and that's what actually many A321 operators go by. That seating configurations isn't dense, they even got 16 recliners. There are other operators who go by more than 200 seats.

Then, you somehow claimed that if we used the same seating configuration as that particular A321, 797-10 would be able to seat 350 passengers !!! Wait a minute, we are not talking about an MoM anymore, that's a freaking A350/777 territory. How can an MOM seat 350 passengers in a normal configuration?

797-10 has 1 meter less in length than an A332, and they both seat 8 across. Basically, Both planes should have similar seating capacity, and NO A332 can ever seat 350 passengers unless it was 9 abreast or something similar to AirAsia. Then I realized where you made your mistake in your calculation, you didn't consider the extra lost areas of galley and lavatories in 797-10.

Narrowbodies have one area for galley/lavatories at the front and another one at the back, that's it. 797-10/A332/788 Should have FOUR. One at the front, one lies between business class and economy class, another one is located in the middle of economy cabin, and the last one would be at the very back. Those two extra areas of galley/lavatories would eat away at least 9-10 rows.

Now it makes sense, if 797-10 has the capability to seat almost the same number as A332, let's see how AA does its A332:

AA A332:
F: 20 seats, Y+: 12 seats, Y: 226 seats. That brings a total of 258 seats
AA A321:
F: 16 seats, Y+: 18 seats, Y: 153 seats
That's almost the same number of premium seats you would find on their A321. A very fair comparison IMO, same operator, almost same number of premium seats. So, it is 187 for A321 vs 258 for 797-10 when using a similar configuration. I am sorry, you just cannot go any further than that with 797-10. Sticking in 350 passengers in that frame size is just inhuman.

For similar configuration:
weight/passenger for 797-10 = 85,000/258 = 329 kg/passenger
weight/passenger for A321 = 48,500/187 = 259 kg/passenger

Again, the A321 has an advantage of 27%.

Note: why are you using the weight of the heavier A321LR here? it is a discussion of the current best narrowbody vs 797-10 in terms of weight/passenger, and A321 has an OEW of 48.5t

I am sorry, it just doesn't work. It is not only that widebodies have more dead weight in terms of one extra aisle and extra areas for galley and lavatories, it is just that the curve of weight vs passengers increases exponentially after some point. When we add more passengers, we don't only make the fuselage heavier, we also have to add more weight to the wings, engines, landing gear, etc. Your statement of "a widebody with the economics of a narrowbody" just cannot be true in my opinion.

Notice how we haven't even discussed weight/passenger for an A322 so far that should easily beat that of A321. We have not even discussed the possibility of Boeing designing a clean sheet narrowbody and equivalent to A322 that is made completely of CFRP.

Again you are using a ridiculously spacious business class. 4 abreast open suites used in AA A332's have a small office work area and are not found in any narrowbody.

4 abreast in a A330 with 48" pitch is more spacious than 4 abreast in an A320 with 36" pitch.

In the A330 that works out to be 1.6 square metres per business class passenger. The A320 has only 0.84 square metres per business class passenger.

With every 4 of those ridiculously spacious business class seats you are loosing 16 economy seats. So its easy to sway the seating capacity but you can't fool me.

The A321 with 4 rows of 4 abreast at 36" pitch and 30 rows of 6 abreast at 32" adds up to 28metres for 187 seats.

The 797-10 with 5 rows 6 abreast at 36" pitch
And 40 rows with 32" pitch adds up to 36.5metres for 350 seats.

The A321's has a 34.44m cabin length which means there is 6.44metres left for lavs and exits rows.

The 787-10 has a 45m cabin length so there's 8.5metres for lavs and exits.

If we multiply that lav/exit length by the width we have 23m2 for the A321 and 42m2 for the 787-10. My 350 seat 787-10 config exactly matches the 187 seats in the A321.

Identical seats. Identical ratio of business class seats. Identical ratio of lav space per passenger.

The correct answer is 350 to 187.

So the 797-10 would be lighter per passenger than any narrowbody ever made.

BTW the A321NEO is 50.8T you are using the weight of the CEO.

https://www.seatguru.com/airlines/Thoma ... 0-200.php#

Here is the most suitable A332 for comparison and it has a whopping 322 seats. The premium economy section has nearly the same sized seats as the J seats in the A320 with identical pitch. That cabin has 15% of the seats as premium. To get to the 8.5% J You could loose 3 rows of premium and get 4 of 8 for 11 extra seats. That's puts its at 333 seats.

Long haul aircraft need more food prep and lavs. So you could reduce that a bit and get to 350 seats quite easily.

Check mate ;)
 
Eyad89
Posts: 242
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Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 4:45 pm

RJMAZ wrote:

Again you are using a ridiculously spacious business class. 4 abreast open suites used in AA A332's have a small office work area and are not found in any narrowbody.

4 abreast in a A330 with 48" pitch is more spacious than 4 abreast in an A320 with 36" pitch.

In the A330 that works out to be 1.6 square metres per business class passenger. The A320 has only 0.84 square metres per business class passenger.

With every 4 of those ridiculously spacious business class seats you are loosing 16 economy seats. So its easy to sway the seating capacity but you can't fool me.

The A321 with 4 rows of 4 abreast at 36" pitch and 30 rows of 6 abreast at 32" adds up to 28metres for 187 seats.

The 797-10 with 5 rows 6 abreast at 36" pitch
And 40 rows with 32" pitch adds up to 36.5metres for 350 seats.

The A321's has a 34.44m cabin length which means there is 6.44metres left for lavs and exits rows.

The 787-10 has a 45m cabin length so there's 8.5metres for lavs and exits.

If we multiply that lav/exit length by the width we have 23m2 for the A321 and 42m2 for the 787-10. My 350 seat 787-10 config exactly matches the 187 seats in the A321.

Identical seats. Identical ratio of business class seats. Identical ratio of lav space per passenger.

The correct answer is 350 to 187.

So the 797-10 would be lighter per passenger than any narrowbody ever made.

BTW the A321NEO is 50.8T you are using the weight of the CEO.

https://www.seatguru.com/airlines/Thoma ... 0-200.php#

Here is the most suitable A332 for comparison and it has a whopping 322 seats. The premium economy section has nearly the same sized seats as the J seats in the A320 with identical pitch. That cabin has 15% of the seats as premium. To get to the 8.5% J You could loose 3 rows of premium and get 4 of 8 for 11 extra seats. That's puts its at 333 seats.

Long haul aircraft need more food prep and lavs. So you could reduce that a bit and get to 350 seats quite easily.

Check mate ;)



Thanks for bringing Thomas Cook up, because it will disprove your numbers.

Before I begin, I would like to say I find it surprising that you are still insisting on the 350 seats figure, because that's something even the A350-1000 can barely pull off for a 2-class configuration (QR offers its A35K in 327 seats).

Anyways, first let's look at the Thomas Cook A322 you linked. This plane only managed to get 322 seats by doing the following:

- It only has Y and Y+ seats.
- It only kept the lavs and galley area at the very front and very back. So they removed TWO areas in the middle for lavs/galley. They gained at least 8-10 rows by doing this. (of course, no regular airline would do that with 797-10)
- I didn't know this, but it seems they installed downstairs so it wouldn't take space,

Now, let's look at their other A332 arrangement that would make everything crystal clear, the all-economy A332 arrangement with 31" pitch (no Y+ here). :

https://www.seatguru.com/airlines/Thoma ... 200_V2.php

This one has 321 seats because they installed one area of lavs in the middle. now, explain this, how can 797-10 take in 350 seats in BOTH J and Y (with 4 areas for galley/lavs), while the A332, which is a meter longer, can barely fit in 321 seats there in all economy?

Now, it so happens that Thomas Cook also offers an all-economy A321 with 220 seats. This is the best example for our case. A332 and A321 that are both all-economy.

Since 797-10 is almost a meter shorter than A322, then if it went all-economy as Thomas Cook did, then it would offer 313 seats ( I removed one row). Let's see the weight per passenger in this case:

797-10 = 85,000/ 313 = 271.5 kg/passenger
A321 = 50,800 / 220 = 230.9 kg/passenger

A321 is still 17.6% lighter in this configuration. The number would be bigger if that 797 had four areas for lavs/galley, just like what most airlines would do with it.


Now, we are comparing two planes that are all-economy, it should be clear now. You wouldn't make mistakes like you did up there when you concluded that A332 would offer 1.6 squared meter for each business class passenger. You multiplied 48 inch by 5 rows to get the length of business class to be 6 meters. Your mistake is that you forgot this is an angled seat business class. So the 48 inch is actually the diagonal length of the seat. Had the seats been arranged in straight positions like in A321, then it wouldn't be able to take in 5 rows, and a 48 inch pitch wouldn't be possible. you also again made other mistakes for calculating the area for galley and lavs. But getting all those numbers right requires more data on the dimensions of each galley.

The easiest way to compare is to go with the all-economy arrangement for both AND specify 4 different areas for lavs/galley in that arrangement, because most 797-10 possible operators would do that.

We both know how that would turn out.

Oh I forgot, "check mate" :D
 
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sassiciai
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Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 5:53 pm

You two are clogging up this thread with your pedantic bullship competition. Can you take that elsewhere, please
 
Boeingphan
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Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 6:18 pm

sassiciai wrote:
You two are clogging up this thread with your pedantic bullship competition. Can you take that elsewhere, please


Where is the damn thumbs up button! Thanks sassiciai
 
Eyad89
Posts: 242
Joined: Fri Sep 02, 2016 10:47 pm

Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 7:21 pm

sassiciai wrote:
You two are clogging up this thread with your pedantic bullship competition. Can you take that elsewhere, please



Nah, I think we are good. As long as there’s something to discuss, we will stick around here for a while. You can skip our conversation if you want.
 
chiki
Posts: 246
Joined: Sat Apr 13, 2013 4:32 pm

Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 8:09 pm

Eyad89 wrote:
sassiciai wrote:
You two are clogging up this thread with your pedantic bullship competition. Can you take that elsewhere, please



Nah, I think we are good. As long as there’s something to discuss, we will stick around here for a while. You can skip our conversation if you want.

Very informative and this is the purpose of this forum. Keep going.
 
irelayer
Posts: 1055
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Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 8:27 pm

Can we have a hybrid blended wing body please? Seems to solve all of these problems.

-IR
 
uta999
Posts: 351
Joined: Mon Jun 14, 2010 11:10 am

Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 8:38 pm

If Boeing need some 'new' design ideas and inspiration, then look back to the Vulcan and Victor. We are soooo bored of a tube with two hairdryers attached.
Your computer just got better
 
RJMAZ
Posts: 214
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 9:12 pm

Eyad89 wrote:
- It only has Y and Y+ seats.
- It only kept the lavs and galley area at the very front and very back.

A plane built to fly for 15 hours usually has much larger business class seats. A premium economy seat on a long haul product often matches a business class seat on a short haul product. As you refuse to acknowledge this simply fact then this will be my last post with you. Everyone else reading this can see the Thomas cook A332 cabin with 322 seats is the best comparison to AA A321 with 187 seats. This layout in a 797-10 will provide narrowbody economics. This is what the rumours state and I'm simply explaining how it will be acheived.

I don't care if they call it comfort plus, world first, business extreme, premium economy. I look at the width and legroom and they are the same. So a direct comparison can be made.

Regarding the centre lavs you are wrong. The centre lavs are only used in long haul products. On a 1 hour flight the lavs don't really get used much. The 797-10 would typically be doing short range domestic work in Japan and Asia and thick routes like Melbourne to Sydney. Replacing narrowbody aircraft 2 to 1 freeing up gates and allowing for growth.
 
tjh8402
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Re: Boeing officially forms program office to flesh out 797 plans

Mon Nov 13, 2017 10:48 pm

I'm not gonna try to read through all the long posts about equivalent floor space, but a few thoughts: There are plenty of narrowbodies with Lavs, and a few with gallies, midcabin. 757s have both. UA 739s and AA A321s have midcabin Lavs.

Delta's domestic 763s had 30 2-2-2 recliners in F. They had ~30 rows of Y+/Y seating. Total seating was 261 people and the plane had a set of mid cabin Lavs. If we assume a 797 is 763 cabin length with an extra seat per row, we're up to 291 seats. If those 763s didn't have slimline seats, we could probably get an extra row or two so maybe 300 seats would be possible. % F/Y+/Y is almost the same as the new DL A321s that seat 192, so I think that it's a safe bet that an 8Y 797 that's the same length as a 763 would seat about 300 if configured equivalently to a Domestic A321.

There's not a lot of "international configuration" lie flat equipped A321s that I'm aware of to speculate what an a321LR would be like. The two I looked at were B6 and BA, both of whom are under 160 seats. B6 is the more dense at 159 seats. Based on international 763 capacities, a similar length 8Y 797 would seat around 240-250.
 
RJMAZ
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 4:48 am

tjh8402 wrote:
If we assume a 797 is 763 cabin length with an extra seat per row, we're up to 291 seats. If those 763s didn't have slimline seats, we could probably get an extra row or two so maybe 300 seats would be possible.

Thank you. I agree that 300 seats is realistic if the cabin length was the same as a 763.

Its worth noting the 763 has a cabin length of only 40.36 metres. The 797-10 design is 4metres longer than the 763 and nearly the same as the the A330-200 which has a cabin length of 45 metres. So would this be safe to assume there would be 5 additional rows of Y?

That is 40 extra seats and puts your estimate of 300 up to 340.

797-10: 85T with 340 pass = 250kg pp
A321NEO: 50.8T with 192 pass = 265kg pp

The 797-9 length at 52 metres would have 288 seats and be 277kg per passenger. But as it can fly for longer it would probably have less dense seating. The longest range 797-8 would probably have the least dense cabin. Probably down to 200 seats.
 
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keesje
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 6:23 am

I think we shouldn't overlook capacity (seatcount) as the key selection criterium for a fleet type. E.G a 220 seat aircraft and a 350 seat aircraft would not compete because they have the same CASM. That's not how it works :crossfingers: Is 350 seats middle of the market? Don't know. Depends on the definition you choose.
"Never mistake motion for action." Ernest Hemingway
 
chiki
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 7:14 am

keesje wrote:
I think we shouldn't overlook capacity (seatcount) as the key selection criterium for a fleet type. E.G a 220 seat aircraft and a 350 seat aircraft would not compete because they have the same CASM. That's not how it works :crossfingers: Is 350 seats middle of the market? Don't know. Depends on the definition you choose.

The question is MOM based on capacity or range, i think a combination of the 2 will make sense. As much as i see RJMAZ calculations 350 passengers will be alot of plane to fill. Will be a niche plane for specific routes and i believe you will loose frequency
 
parapente
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 9:11 am

I note there have been a couple of positive statements about the 220-270 797x at the Dubai air show (Emirates and Ethiopian).They both note the reduced cargo space of the (ovoid) shape of the aircraft.
Clearly Boeing will have considered this carefully and decided that for their core long term (this cannot be changed later!)target markets that the improved economy (low drag/weight) outweighs the loss of some cargo carrying capacity.That may give a clue as to how they see the aircraft being used in 10-20 years time.
 
brindabella
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 10:30 am

RJMAZ wrote:
keesje wrote:
If the lower fuselage would be just a bit higher, circular, it would be lighter and it could optionally take the same LD3 containers / pallets as the 787, 777 and A350s. If it has high BPR engines, it would have high main landing gears anyway.

Image
Here is the A330 circular cross section with LD3 containers. Look how tight it is and how high the floor has to be. You want the floor lower so the widest point is at elbow level. Considering my 8 abreast 797-10 is a foot narrower than the A330 even if it was full circular you could not fit LD3's. The floor would have to be at the 50% mark, so the widest point of the cabin would be at floor level.

Using LD2's which are the same height but narrower than the LD3 would allow them to sit slightly lower down in the fuselage. But still that would require a fully circular fuselage. I actually think this is the most likely cross section 8ab, 5m cabin width, circular fuselage with LD2's.

If you want an oval design you can only use LD3-45's. Or maybe a custom container the same height as an LD3-45 but slightly wider. This would be highly likely if they plan on building 1000+.

I'd say 60% chance of circular 8ab with ld2's. 35% chance of oval double bubble, and 5% pure oval. 0% chance of 7ab as it cant reach narrowbody casm. 0% chance of 6ab as it can't reach the passenger requirement for upgauging short thick narrowbody routes. It would need 757-300 length.


Many thanks to keesje & yourself for the graphics!
However, at the risk of seeming to carp, so far the Boeing announcements have referred to the 797 as specifically NOT being seen as a freight-hauler.
So I think that this is a more likely cross-section:

https://screenshots.firefox.com/VOemUjC ... liners.net

(hope that works!)

With respect to range/weight: I am also very keen on your "virtuous circle". I once tried to point-out to the forum the outstanding historic performance of the A300-600R in Asia where many markets were already thick. It worked a treat with lots of seats & not much wing.
However several very respected members observed at the time that the most successful models of successive types only became so when the range was extended, so offering the airline much more versatility, even at the cost of sometimes "abusing" the type.
Maybe they were right - but I suspect rather that they were talking from a "North Atlantic" perspective (EG North America + Europe).
The Asian scene (the "A300-600R" EG) seemed to be historically somewhat different but likely to become much more relevant to the OEMs as hundreds of millions of people continue to join the middle class and so become new airline customers.

So let's be optimistic - maybe the time is now right. Your analysis that halving the range can give a weight-reduction of 1/3rd is compelling indeed.
And I am hoping that the initial range of each model is very much like your plan, assuming future added capability as the type matures & the range of each model grows in the normal way.

I am still to be convinced by your 797-8, however, and I have only ever seen 2 models in the family. The A321neo will get better still, surely; a new wing will make a huge difference to an already super model.
However your thinking RE a wing which will allow a future NSA to outmatch the CS-500 as well as compete with MOST A320neos is lots of fun & a totally new thought, at least for me. But being cool to the 797-8, I still see Boeing being forced into another (larger) wing in there somewhere to compete directly with the A321neo & it's enhanced future versions.

Better stop.
Thanks again,
cheers Bill
(brindabella)
Billy
 
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 10:47 am

So to cut through the obfuscating crap of cabin configurations and toilet and galley placement I compared the options presented by RJMAZ by cabin area to the defacto market leader in the A321 to represent the narrowbody. If you are an airline you can decide what you want to do in the space provided.

For the seat area calculation I assumed that 8/10 of the widebody is useful area and 6/7 of the narrowbody is useful area.


797-8 797-9 797-10 A321
Cabin width 5 5 5 3.7
Cabin Length 38 44 50 40.88
Fuselage Length 46 52 58 45
Cabin area 190 220 250 151.256
Seat area 152 176 200 129.648
OEW 75000 80000 85000 50500
Mass per useful M^2 493.4 454.5 425 389.5

It can be seen that the RJMAZ 797-10 has ~ 9% greater mass per useful area than the A321. If we remove the assumption of useful cabin area then the equation and assume it is all useful the 797-10 is still heavier by nearly 2% per seat.

Edit:Sorry the table is hard to read, it looks lovey on the edit screen (all formatted nice) but needs a bit of unpicking when posted.

Fred
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 11:43 am

chiki wrote:
The question is MOM based on capacity or range, i think a combination of the 2 will make sense. As much as i see RJMAZ calculations 350 passengers will be alot of plane to fill. Will be a niche plane for specific routes and i believe you will loose frequency

Three lengths with a shared wing allows range and capacity in the one family. Most family give the longer members a higher takeoff weight and larger engines to maintain some range. I think a simple stretch and shrink which gives the most versatility to improve CASM at one end and range at the other.

The number of destination pairs with 10+ daily flights, the number of gate restricted airports and the number of widebody aircraft flying under 1000nm is growing exponentially.

Upgauging is the only solution. The market has reached a point where a short range widebody will sell extremely well. A quarter of the worldwide 737 and A320's are flying super thick routes like Melbourne to Sydney. Airlines are desperate to reduce frequency but there are no widebody available designed for short range efficiency.
 
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 12:04 pm

flipdewaf wrote:
For the seat area calculation I assumed that 8/10 of the widebody is useful area and 6/7 of the narrowbody is useful

That's the mistake right there. That assumes all aisles are the same size. Each widebody aisle is supporting only 4 abreast so the aisle can be narrower. The 797's aisles could be three quarters the width of the A321's and still be just as good.

So to recalculate using 8/9.5 for the 797 vs 6/7 for the A321.

Also the cabin lengths are wrong. The A321 is 34.44 and the A332 is 45m

797-8 797-9 797-10 A321
Cabin width 5 5 5 3.7
Cabin Length 33 39 45 34.44
Fuselage Length 46 52 58 45
Cabin area 165 195 225 127
Seat area 139 164 190 109
OEW 75000 80000 85000 50800
Mass per useful M^2 540 487 447 466

The 797-10 beats the lightest per m^2 narrowbody
Last edited by RJMAZ on Tue Nov 14, 2017 12:30 pm, edited 1 time in total.
 
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 12:25 pm

So again economic gains by trading in passenger comfort.
 
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 12:49 pm

How so?

2-4-2 is better than 3-3. Lots of people travel as a couple so its the best layout by far. Plus if there's a food trolley you can use the second aisle.

Its also much better than 3-3-3 on the 787.

The 787 has a massive 556kg per usable square metre. So on short routes the 797 would have better CASM so a more comfortable cabin could be used.
 
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 1:07 pm

RJMAZ wrote:
flipdewaf wrote:
For the seat area calculation I assumed that 8/10 of the widebody is useful area and 6/7 of the narrowbody is useful

That's the mistake right there. That assumes all aisles are the same size. Each widebody aisle is supporting only 4 abreast so the aisle can be narrower. The 797's aisles could be three quarters the width of the A321's and still be just as good.

So recalculate using 8/9.5 for the 797 vs 6/7 for the A321.

Your diagrams definitely showed 18" aisles to compare to the airbus 19" but I'll humour you anyway.

So you are saying that for the 797 design as you have proposed the width of the aisle is scaled on a per seat abreast basis with a narrow body? changed to 8/9.5 It's still heavier per seat than a narrow body. by over 3% per seat with lower comfort levels, higher turn times. I understand that the 80t OEW was an educated guess but my estimates on weight have always shown that unless you are talking about extremely long narrowbodied aircraft (over 753/MD8-63 fineness ratios) then the weight of the fuselage generally favours the narrow bodied aircraft per seat.

Physics dictates that a wide body fuselage will not be able to be as light as a narrow body fuselage for a given technology level, physical constraints such as rotation angles or parking availability are a different matter.

Fred
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flipdewaf
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 1:14 pm

RJMAZ wrote:
flipdewaf wrote:
For the seat area calculation I assumed that 8/10 of the widebody is useful area and 6/7 of the narrowbody is useful

That's the mistake right there. That assumes all aisles are the same size. Each widebody aisle is supporting only 4 abreast so the aisle can be narrower. The 797's aisles could be three quarters the width of the A321's and still be just as good.

So to recalculate using 8/9.5 for the 797 vs 6/7 for the A321.

Also the cabin lengths are wrong. The A321 is 34.44 and the A332 is 45m

797-8 797-9 797-10 A321
Cabin width 5 5 5 3.7
Cabin Length 33 39 45 34.44
Fuselage Length 46 52 58 45
Cabin area 165 195 225 127
Seat area 139 164 190 109
OEW 75000 80000 85000 50800
Mass per useful M^2 540 487 447 466

The 797-10 beats the lightest per m^2 narrowbody


That's a fair point but it throws open another can of worms. How does your 797 proposal only lose 7m of fuselage length for the tail and cockpit sections while the narrower A321 loses over 10m?

Edit:ignore that point, I read the table wrong.
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 1:23 pm

flipdewaf wrote:
Edit:Sorry the table is hard to read, it looks lovey on the edit screen (all formatted nice) but needs a bit of unpicking when posted.

Fred

Seems like the trick is to use the left-bracket / right-bracket symbol on the edit toolbar that generates "code" elements ( Ref: https://www.bbcode.org/examples/?id=15 ) so you get fixed-width characters.. Write your table in an editor such as Notepad that also uses fixed width characters, use spaces rather than tabs, and you're good to go.

Example:

                         797-8  797-9  797-10     A321
Cabin width                  5  5           5        3.7
Cabin Length                38  44         50       40.88
Fuselage Length             46  52         58       45
Cabin area                 190  220       250      151.256
Seat area                  152  176       200      129.648
OEW                      75000  80000   85000    50500
Mass per useful M^2      493.4  454.5     425      389.5
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Ethiopian interested to order 10-20 Boeing 797s

Tue Nov 14, 2017 1:33 pm

News link: https://www.reuters.com/article/us-emir ... SKBN1DE0UF

This is the right sized airplane for them on routes that dont require a 270 seater and more expensive B788 to operate on.

It will also allow them to open new medium haul markets in India, West Africa, Europe, Middle East flown nonstop with no payload issues.
 
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Re: Ethiopian interested to order 10-20 Boeing 797s

Tue Nov 14, 2017 1:42 pm

It will be an exceptional aircraft for them. It will offer the best capacity/range combination for many of their routes. Only thing, it will be yet another type in their already crowded fleet... Boeing will need a lot more interest, though, before they can pull the trigger.
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Re: Ethiopian interested to order 10-20 Boeing 797s

Tue Nov 14, 2017 1:52 pm

It'll also do Warp 6 and make it to the Pegasus Galaxy in under 3 weeks.

Well, it might given how much shifting around Boeing's definition of MoM/NMA/MilleniumFalcon is doing!

Most recent had MoM at < 5,000 nm and < 270 seats.... which to me is dangerously close to A321LR territory to be a safe investment.
 
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Re: Ethiopian interested to order 10-20 Boeing 797s

Tue Nov 14, 2017 1:55 pm

There seems to be a lot of interest, United, American, JAL, Ethiopian, Qantas have all said they are up for it, Boeing should just do it!
 
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Re: Ethiopian interested to order 10-20 Boeing 797s

Tue Nov 14, 2017 4:31 pm

fcogafa wrote:
There seems to be a lot of interest, United, American, JAL, Ethiopian, Qantas have all said they are up for it, Boeing should just do it!

Emirates ( https://www.reuters.com/article/us-emir ... SKBN1DE0EO ) making generally supportive noises too.

On new aircraft developments, Clark suggested that either Emirates or discount carrier flydubai, which is also owned by the Dubai government, could be interested in a mid-sized jet that Boeing (BA.N) is considering developing.

“Whether it is in flydubai ... or in Emirates, with the carriers working far closer than they have been for a long time, would it fit? Yes, I think possibly in certain routes,” Clark said.

Designed to reduce drag by shaving cargo space in the belly while carrying 225-275 passengers, the proposed jet would not work on routes where Emirates carries significant cargo.

But Clark said global aviation would welcome the new plane.

Far from a commitment to order, but also far from a "what the * is Boeing thinking" kind of comment we get quite often here on a.net.
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Re: Ethiopian interested to order 10-20 Boeing 797s

Tue Nov 14, 2017 6:58 pm

fcogafa wrote:
There seems to be a lot of interest, United, American, JAL, Ethiopian, Qantas have all said they are up for it, Boeing should just do it!


These are all good signs, but it's very easy for an airline to say, "there's routes that concept would work well for us on."

It's another thing to sign a paper saying, "we'll buy X of them for $Y billion and pay $Z hundred million in cancellation penalties if we change our mind."

It's not getting done until Boeing is confident enough of the airlines will do that second part. That includes figuring out whether they'll change their mind if an A322 is also developed.

Amiga500 wrote:
It'll also do Warp 6 and make it to the Pegasus Galaxy in under 3 weeks.


That's ridiculous! Warp 6 isn't anywhere near fast enough to reach the Pegasus Galaxy in 3 weeks. Even at Warp 9+ it would take over 30 years just to cross our own galaxy!

Sorry. Just trying to fit in here. ;)
 
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 9:19 pm

Slug71 wrote:
SCAT15F wrote:
I'm hoping for either 3-3 or a 2-2-2 that cannot be expanded to 2-3-2.

MOM sweet spot is 762 (or 752.5) per the airlines. Boeing would be better off just NEO-ing the 762 (NOT the 763) and covering the A321/752 replacement with single aisle NSA.


No way it will be 2-2-2. That configuration just makes no sense from a revenue stand point.



Boeing considered it before with the 7J7.
 
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 9:21 pm

flipdewaf wrote:
Your diagrams definitely showed 18" aisles to compare to the airbus 19" but I'll humour you anyway.

I'm just comparing using the same seats. You can easily fudge the numbers by using different seats.

The A320 standard is 18" seats and a 20" aisle.

My 797 design uses 17.5" seats and 18" aisles.

If you use 18" seats on my design each aisle drops to 16".

Alternatively to do the comparison you could put 17.5" seats in the A320 and make its aisle 23".

Airlines regularly trade aisle and seat space depending on their average sector length. Wider aisles are useful if they are doing lots of flights under 1 hour, it speeds up boarding and the comfort is still fine for a short flight.

15inch aisles are used on 9 abreast A330's and 10 abreast A350, 777's. The 797 is much shorter and has only 8 abreast so less people boarding. So even two 15" aisles on the 797 designs would still board quicker than a 757.

But the 787-10 as the numbers show is lighter per passenger and lighter per usable area than the A321.

Boeing should easily be able to hit my weight numbers. I'm using the weights of a 40 year old A300 design and deducting ONLY 5% off. Boeing will easily hit the target with a carbon fibre design. They may even go lighter than my numbers which might add 100-200nm extra range to the designs.
 
flipdewaf
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 9:39 pm

RJMAZ wrote:
flipdewaf wrote:
Your diagrams definitely showed 18" aisles to compare to the airbus 19" but I'll humour you anyway.

I'm just comparing using the same seats. You can easily fudge the numbers by using different seats.

The A320 standard is 18" seats and a 20" aisle.

My 797 design uses 17.5" seats and 18" aisles.

If you use 18" seats on my design each aisle drops to 16".

Alternatively to do the comparison you could put 17.5" seats in the A320 and make its aisle 23".

Airlines regularly trade aisle and seat space depending on their average sector length. Wider aisles are useful if they are doing lots of flights under 1 hour, it speeds up boarding and the comfort is still fine for a short flight.

15inch aisles are used on 9 abreast A330's and 10 abreast A350, 777's. The 797 is much shorter and has only 8 abreast so less people boarding. So even two 15" aisles on the 797 designs would still board quicker than a 757.

But the 787-10 as the numbers show is lighter per passenger and lighter per usable area than the A321.

Boeing should easily be able to hit my weight numbers. I'm using the weights of a 40 year old A300 design and deducting ONLY 5% off. Boeing will easily hit the target with a carbon fibre design. They may even go lighter than my numbers which might add 100-200nm extra range to the designs.


Why should we. It expect any similar reductions in weight from a modern narrow body? The A320 is after all 30+ years old. I don't think carbon fibre would reduce the weight of the airframe at all, we didn't see that for the A330 vs 787.


What are the characteristic dimensions outside of the fuselage for you design? I.e. Wings, empennage etc. If you stick to a similar wing loading to the A321 then you get a wing area of ~190m^2 and require a 53-54klb engine. What is the 44m span based on?

Fred




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Amiga500
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Re: Ethiopian interested to order 10-20 Boeing 797s

Tue Nov 14, 2017 10:07 pm

iamlucky13 wrote:
That's ridiculous! Warp 6 isn't anywhere near fast enough to reach the Pegasus Galaxy in 3 weeks. Even at Warp 9+ it would take over 30 years just to cross our own galaxy!

Sorry. Just trying to fit in here. ;)



Boeing's powerpoint rangers say it can do both. A real game-changer.
 
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Re: Boeing officially forms program office to flesh out 797 plans

Tue Nov 14, 2017 11:16 pm

SCAT15F wrote:
Slug71 wrote:
SCAT15F wrote:
I'm hoping for either 3-3 or a 2-2-2 that cannot be expanded to 2-3-2.

MOM sweet spot is 762 (or 752.5) per the airlines. Boeing would be better off just NEO-ing the 762 (NOT the 763) and covering the A321/752 replacement with single aisle NSA.


No way it will be 2-2-2. That configuration just makes no sense from a revenue stand point.



Boeing considered it before with the 7J7.


And it never happened...
With most airlines moving to high density cabins, this will be no exception. Being in a niche market, it needs to work harder to return it's investment.
 
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Re: Boeing officially forms program office to flesh out 797 plans

Wed Nov 15, 2017 12:11 am

flipdewaf wrote:
Why should we. It expect any similar reductions in weight from a modern narrow body? The A320 is after all 30+ years old. I don't think carbon fibre would reduce the weight of the airframe at all, we didn't see that for the A330 vs 787.

Actually we did get a weight reduction with the 787. Its all in the details.

The 787 is a 4% wider and 5.5% taller than the A330. To get the weight you must multiple both the height and width percentages which is 1.04 x 1.055. The 787 should weigh 9.77% more per fuselage metre. But it weighs only 2-2.50% more per metre.

So Boeing has reduced the weight by a massive 7% using composites. So my 5% weight reduction on the a300 size is not only achievable but conservative.

That extra height has a HUGE advantage. With the same LD3 containers this allows the floor to be placed lower down. So the 787's maximum 5.49m cabin width is at armrest level. The A330's maximum 5.28m cabin width is an inch above the floor.

At shoulder height it is approx 5.40m vs 5.07m. That is the true cabin widths that should be used.

This is a 6.5% width advantage in favour of the 787.

If you subtract two 18" 45cm aisles off both widths to work out the seating space it is now 4.50m vs 4.17m. That is a 8% increase in available seating width in favour of the 787. This is how Boeing can fit an extra seat in the 787 with only a tiny reduction in comfort levels.



flipdewaf wrote:
What are the characteristic dimensions outside of the fuselage for you design? I.e. Wings, empennage etc. If you stick to a similar wing loading to the A321 then you get a wing area of ~190m^2 and require a 53-54klb engine. What is the 44m span based on?

My designs I have put in a large amount of effort.

I have built a model using 30 popular aircraft using their dimensions, ranges, weights, fuel capacity, wing area, wing loading, wing sweep, takeoff length, cruise speed, cabin area, engine thrust and engine fuel efficiency.

I can then design an aircraft design with any size and range requirement. It will determine the weights, optimal wing details and thrust required.

I can stretch or shrink a design while keeping the MTO constant and see the empty weights and ranges change.

My wing choice is centred around the middle of the family. With a simple stretch and shrink. The advantages of a larger wing and lower wing loading come in the form of improved lift to drag ratio. The added wing weight eventually provides a fuel burn advantage as the flight becomes longer. This is why long haul aircraft appear overwinged.

Wing sweep also comes into play. A 25 degree wing will provide more lift than a 35 degree wing with the same area. But if the plane is designed for 10 hours you might want the faster cruise speed that comes from extra wing sweep.
 
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Re: Boeing officially forms program office to flesh out 797 plans

Thu Nov 16, 2017 10:09 am

RJMAZ wrote:
My designs I have put in a large amount of effort.
There is no denying that, the designs are very well thought through and very well presented!

RJMAZ wrote:
I have built a model using 30 popular aircraft using their dimensions, ranges, weights, fuel capacity, wing area, wing loading, wing sweep, takeoff length, cruise speed, cabin area, engine thrust and engine fuel efficiency.
Intriguing, my models only work through inputs to calculate the outputs although I have long thought about putting a constraints diagram in at the front end for a more automated driving of the models.
RJMAZ wrote:
My wing choice is centred around the middle of the family. With a simple stretch and shrink. The advantages of a larger wing and lower wing loading come in the form of improved lift to drag ratio.
But what are the characteristic dimensions of the wing? We have span but do you have the area available? taper ratio? Root chord? wing sweep?

RJMAZ wrote:
The advantages of a larger wing and lower wing loading come in the form of improved lift to drag ratio. The added wing weight eventually provides a fuel burn advantage as the flight becomes longer. This is why long haul aircraft appear overwinged.
Agreed, the interesting thing about the MOM debate is that we can calculate all the technical things either through direct calculations or statistical models down to an accuracy of a few percent, the real money making piece is in the market numbers and development costs.

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Re: Boeing officially forms program office to flesh out 797 plans

Thu Nov 16, 2017 10:37 am

RJMAZ wrote:


But the 787-10 as the numbers show is lighter per passenger and lighter per usable area than the A321.




Alright, allow me to ask differently this time, why wouldn't Boeing go for an all new composite narrowbody design that would be similar in size to 757/A322. What are the advantages or disadvantage?
 
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Re: Boeing officially forms program office to flesh out 797 plans

Thu Nov 16, 2017 12:41 pm

flipdewaf wrote:
But what are the characteristic dimensions of the wing? We have span but do you have the area available? taper ratio? Root chord? wing sweep?.

I only estimate wing sweep. Long haul 31-33° and short haul 25°. The A300 and A310 have 28°

My model works as follows.

I first calculate empty weight. I made a formula where you enter cabin width, length and max required range and it gives you a weight. I kept tweaking the formula so the answer always matched an existing aircraft. I manually knock off 3% for a carbon wing and another 3% for a carbon fuselage.

For double deck estimates I only add 50% of the upper deck area to the input. It accurately estimates the 747 and A380 weight by doing that.

Payload weight is 150kg per m2 of cabin area.

Fuel capacity is based on range. For a max range of 9000nm the fuel capacity in kg is the same as the empty weight of the aircraft itself. For a max range of 2000nm the fuel capacity is only 10% of the empty weight.

Max takeoff weight is empty weight plus fuel and payload.

I get the wing loading by averaging the four aircraft with the nearest max takeoff weight. Then multiple that by the MTO.

Total Engine thrust is usually 30% of MTO. Slightly more for a narrowbody and slightly less for a long range quad.
 
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Re: Boeing officially forms program office to flesh out 797 plans

Thu Nov 16, 2017 1:12 pm

Eyad89 wrote:
Alright, allow me to ask differently this time, why wouldn't Boeing go for an all new composite narrowbody design that would be similar in size to 757/A322. What are the advantages or disadvantage?

6 abreast won't be able to hit the capacity target. Upgauging is the main market of the MOM.

The half way point between the A321 and the A332 is around 190m2. That would require an aircraft longer than the 757-300.

The loads on a tube grow exponentially with length. So a short thick fuselage ends up becoming much lighter once you go beyond 757 length.

A 757-300 had a 10% increase in empty weight for a 15% increase in length. All the wide bodies gained less than half that weight for similar length gains. The fuselage should be one of the lightest parts.

With cabin areas 165m2 195m2 and 225m2 an A320 would need to be 55m 63m and 71m long.

A short thick fuselage also gives more payload and allows for a shorter and lighter landing gear.
 
flipdewaf
Posts: 1935
Joined: Thu Jul 20, 2006 6:28 am

Re: Boeing officially forms program office to flesh out 797 plans

Thu Nov 16, 2017 1:24 pm

RJMAZ wrote:
flipdewaf wrote:
But what are the characteristic dimensions of the wing? We have span but do you have the area available? taper ratio? Root chord? wing sweep?.

I only estimate wing sweep. Long haul 31-33° and short haul 25°. The A300 and A310 have 28°

My model works as follows.

I first calculate empty weight. I made a formula where you enter cabin width, length and max required range and it gives you a weight. I kept tweaking the formula so the answer always matched an existing aircraft. I manually knock off 3% for a carbon wing and another 3% for a carbon fuselage.

For double deck estimates I only add 50% of the upper deck area to the input. It accurately estimates the 747 and A380 weight by doing that.

Payload weight is 150kg per m2 of cabin area.

Fuel capacity is based on range. For a max range of 9000nm the fuel capacity in kg is the same as the empty weight of the aircraft itself. For a max range of 2000nm the fuel capacity is only 10% of the empty weight.

Max takeoff weight is empty weight plus fuel and payload.

I get the wing loading by averaging the four aircraft with the nearest max takeoff weight. Then multiple that by the MTO.

Total Engine thrust is usually 30% of MTO. Slightly more for a narrowbody and slightly less for a long range quad.

So what is the wing area?

My model uses a modified version of the Stamford weight breakdown method and allies that to a buildup method for the aerodynamics. I then have some code which iterates weights, speeds and altitudes to determine thrust required in each scenario followed applying a basic sfc number to determine fuel usage. This last bit is problematic as i only currently use a sing value for SFC, which I know is innacurate. I normally set the speed to 175 kts at sea level to determine the thrust required from a single engine.

Fred
Image
 
bigjku
Posts: 1097
Joined: Sat Feb 17, 2007 10:51 pm

Re: Boeing officially forms program office to flesh out 797 plans

Thu Nov 16, 2017 1:36 pm

Eyad89 wrote:
RJMAZ wrote:


But the 787-10 as the numbers show is lighter per passenger and lighter per usable area than the A321.




Alright, allow me to ask differently this time, why wouldn't Boeing go for an all new composite narrowbody design that would be similar in size to 757/A322. What are the advantages or disadvantage?


My opinion is no new narrowbody will be effecting launched until one can do so with fundamentally different concepts of operation or construction. You are either going to see a new propulsion concept, a new aerodynamic layout or something that can be produced in a radically automated manner.

Specific to the question of just doing a composite 737/757 replacement the efficiency gains in general aren’t enough to justify the gigantic cost to do the R&D and invest in all new tooling for high volume narrowbody production. You gain less weight efficiency on the smaller frame and you can’t recover what you invest by charging more. See the problems the C-Series is having as a good example.

Plus I don’t think the time is right there. IMHO a hybrid electric narrowbody is coming by 2030 or so. You don’t want to invest a ton of money in something that fundamentally looks like a 737/A320 right now just with newer engines and a composite body.

The 797 is a bit different in that there may be a market for a bigger aircraft optimized for far less range than the A330/350/787. I happen to think the business case makes sense and that many airlines will replace not only some of their wide bodies with the plane but a significant portion of their narrowbodies as well. If that is the case there is a good reason to build this plane and do a narrowbody replacement next.
 
Amiga500
Posts: 1343
Joined: Tue Mar 03, 2015 8:22 am

Re: Boeing officially forms program office to flesh out 797 plans

Thu Nov 16, 2017 1:44 pm

Boeing would be as well buying the MC-21 project from Irkut.

Technically, the program would be a good match to their existing lineup. Politically, well, The Donald does have Vlad the puppetmaster pulling his strings.
 
Eyad89
Posts: 242
Joined: Fri Sep 02, 2016 10:47 pm

Re: Boeing officially forms program office to flesh out 797 plans

Thu Nov 16, 2017 1:58 pm

RJMAZ wrote:
6 abreast won't be able to hit the capacity target. Upgauging is the main market of the MOM.

The half way point between the A321 and the A332 is around 190m2. That would require an aircraft longer than the 757-300.

The loads on a tube grow exponentially with length. So a short thick fuselage ends up becoming much lighter once you go beyond 757 length.


We go back to the most basic question, what is the capacity target? Airlines agree it is somewhere north of 200 passengers. Is it 220? Is it more? Different airlines have different answers. The answer for this questions really matters because it would affect how Boeing could approach its design. Anything up to 230-235 passengers can be managed by a single aisle that is slightly shorter than a 753. Going more than that would require a widebody.
RJMAZ wrote:
A 757-300 had a 10% increase in empty weight for a 15% increase in length. All the wide bodies gained less than half that weight for similar length gains. The fuselage should be one of the lightest parts.

I see your point, but even with that it would still weigh less than a widebody, which is the variable that designers want to optimize.
RJMAZ wrote:
With cabin areas 165m2 195m2 and 225m2 an A320 would need to be 55m 63m and 71m long.


Why target those areas in particular? Airlines are interested in flying 200+ passengers in a reasonable seating configuration and comfort. That's the target.
RJMAZ wrote:
A short thick fuselage also gives more payload and allows for a shorter and lighter landing gear.


A short thick fuselage reminds me of A310, which I guess is the least successful model Airbus has ever made in terms of sales. Is it really time to revive its concept? A310 was a bit too short with 47m in length, and A300-600 had a length of 54m. A widebody 797 would definitely be somewhere between those two.

Now, I am using sales of past models as a predictor of a future 797. I know, this is not 100% correct as the nature of the current market is simply not comparable anymore. My whole points is that most of the demand for MOM seems to be 200-230 seats, and that can be easily achieved by an efficient narrowbody that is also cheaper to obtain. This would make a lot of customers happy.
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