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Boeing 797... Why Not Just Base It On The 787?  
User currently offlineSKAirbus From Norway, joined Oct 2007, 1737 posts, RR: 1
Posted (3 years 6 months 1 week 6 days 16 hours ago) and read 15072 times:

I was thinking.

Boeing seems to be keen on going down the route of a dual-aisle replacement for the larger 737 models by designing a whole new aircraft. However, this doesn't make sense to me. Wouldn't it be better to base it on the 787 by doing the following:

- Reduce the fuselage length to reduce capacity.
- Replace doors two and three with overwing exits (like most 767-300 models).
- Redesign the 787 wing to be smaller.
- Put on new engines to reflect the new aircraft's range/profile.

I think this would benefit customers by offering a common cockpit and simplified maintenance procedures.

Any ideas?

[Edited 2011-03-10 05:47:02]


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45 replies: All unread, showing first 25:
 
User currently offlineseabosdca From United States of America, joined Sep 2007, 5467 posts, RR: 6
Reply 1, posted (3 years 6 months 1 week 6 days 16 hours ago) and read 15051 times:

The 9Y fuselage of the 787 is just too wide for a 150-220 seat aircraft. Even a "stubby" A310-like version would be at the very top end of that range.

If the new aircraft is to be a twin-aisle at all (something I'm deeply skeptical of), then it will have to be 2-2-2 or 2-3-2 at most, not 3-3-3.


User currently offlinesw733 From United States of America, joined Feb 2004, 6324 posts, RR: 9
Reply 2, posted (3 years 6 months 1 week 6 days 16 hours ago) and read 14970 times:

if they're going to base a 797 on a 787, they might as well just make a new version of the 787. Among other things, it makes certification a lot easier/quicker/cheaper. Boeing must feel the need for a brand new airplane.

Quoting seabosdca (Reply 1):
then it will have to be 2-2-2

What's the point of wasting space with a dual-aisle plane if you're going to do 2-2-2? I'm not criticizing, just curious...what advantage does that have over 3-3 and making a slightly skinnier aircraft with just one aisle?


User currently offlinerheinwaldner From Switzerland, joined Jan 2008, 2225 posts, RR: 5
Reply 3, posted (3 years 6 months 1 week 6 days 16 hours ago) and read 14968 times:

Just?

Using the 787 cross section and add a short range wingset has some merits (hints A300, A310, mega cities) ...

It would just not help to keep the 737 market...


User currently offlineBurkhard From Germany, joined Nov 2006, 4397 posts, RR: 2
Reply 4, posted (3 years 6 months 1 week 6 days 15 hours ago) and read 14848 times:

If it were as simple, Boeing would not have skipped the 783, and at least some airlines would have shown interest in it.

Basically, a 787 has an empty weight of 125 tons, while an A321 has 48 tons. The 787 is FAR to heavy to be a good point to start from.


User currently offlineNAV20 From Australia, joined Nov 2003, 9909 posts, RR: 35
Reply 5, posted (3 years 6 months 1 week 6 days 15 hours ago) and read 14849 times:

Quoting rheinwaldner (Reply 3):
Using the 787 cross section and add a short range wingset has some merits

To put it shortly, surely it was tried with the (cancelled) B783?



"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
User currently onlineBMI727 From United States of America, joined Feb 2009, 15744 posts, RR: 27
Reply 6, posted (3 years 6 months 1 week 6 days 15 hours ago) and read 14682 times:

Quoting SKAirbus (Thread starter):
Reduce the fuselage length to reduce capacity.
Quoting SKAirbus (Thread starter):
Redesign the 787 wing to be smaller.
Quoting SKAirbus (Thread starter):
Put on new engines to reflect the new aircraft's range/profile

Do those things and it isn't really based on the 787 so much anymore. What you described as in many ways similar to the 787-3, which was met mostly with indifference by the market.

But, you will undoubtedly see a lot of the 787's technology in the 737 replacement, just as there is a lot of 707 type technology in the 727 and so on.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlinegordomatic From United States of America, joined Mar 2009, 93 posts, RR: 0
Reply 7, posted (3 years 6 months 1 week 6 days 15 hours ago) and read 14605 times:

Quoting BMI727 (Reply 6):
But, you will undoubtedly see a lot of the 787's technology in the 737 replacement

Exactly. I think the timing of the 797 announcement may be attached to the completion of 787 flight testing & validation of new technologies; what works, what does not. For example, will bleedless be applied to the 797 or are the benefits limited to larger aircraft?

-Gordon



We have clearance, Clarence. Roger, Roger. What's our vector, Victor?
User currently offlinetsugambler From United States of America, joined Jul 2010, 302 posts, RR: 0
Reply 8, posted (3 years 6 months 1 week 6 days 15 hours ago) and read 14590 times:

Quoting sw733 (Reply 2):
What's the point of wasting space with a dual-aisle plane if you're going to do 2-2-2? I'm not criticizing, just curious...what advantage does that have over 3-3 and making a slightly skinnier aircraft with just one aisle?

I, and many others I'm sure, would be far more comfortable and happy in a 2-2-2 rather than a 3-3. The "wasted" space penalty may not be as much as previously thought, especially if CFRP construction allows an elliptical cross-section. Turnaround times would be much lower, increasing utilization, and it would also be a "game-changer" in a way... no other narrowbody could compete in terms of comfort for passengers. Many might not be persuaded by these arguments, insisting that weight and drag are the only concerns that should be be considered, but there are definitely good reasons to explore the possibility of a 2-2-2.

(By the way, if it has two aisles, it's by definition no longer a narrowbody, is it?)


User currently offlinesw733 From United States of America, joined Feb 2004, 6324 posts, RR: 9
Reply 9, posted (3 years 6 months 1 week 6 days 15 hours ago) and read 14554 times:

Quoting tsugambler (Reply 8):
I, and many others I'm sure, would be far more comfortable and happy in a 2-2-2 rather than a 3-3

Me too, but what about economics? Which is cheaper to operate? a 2-2-2 would be a larger plane with the same number of people, I imagine that costs more to operate while still pulling in the same number of customers. At the end of the day, the airplane that is cheaper to operate will win the orders...simple economics.


User currently offlineSKAirbus From Norway, joined Oct 2007, 1737 posts, RR: 1
Reply 10, posted (3 years 6 months 1 week 6 days 14 hours ago) and read 14478 times:

Quoting sw733 (Reply 9):
Me too, but what about economics? Which is cheaper to operate? a 2-2-2 would be a larger plane with the same number of people, I imagine that costs more to operate while still pulling in the same number of customers. At the end of the day, the airplane that is cheaper to operate will win the orders...simple economics.

I tend to agree.

Although from a passenger point of view the two aisle solution sounds great in terms of comfort, from an economical point of view, surely a twin aisle aircraft with the same passenger capacity as the 737-800/900 would be heavier?

That's why I am wondering if in the long run a shortened 787 would work. Remove some fuselage sections, change the wing and put on lighter engines and in theory there should be a significant reduction in the weight. Also, it would provide some great cargo capacity on shorter trunk routes LHR-FRA for example.



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User currently offlineNAV20 From Australia, joined Nov 2003, 9909 posts, RR: 35
Reply 11, posted (3 years 6 months 1 week 6 days 14 hours ago) and read 14339 times:

Quoting sw733 (Reply 2):
What's the point of wasting space with a dual-aisle plane if you're going to do 2-2-2?

I think it comes down to 'elbow-room,' sw773. Unless you're seriously overweight, a somewhat narrower seat is no great problem provided that you have at least one elbow in 'free mode,' able to 'overhang' either the window-space or the aisle. I'd BET that all of us tend to avoid 'middle seats' like the plague, for just that reason.

Hope Boeing pulls it off. If they can, it'll be a 'match-winner.' People will finally be able, just as passengers, to see a clear difference between the 'offerings' of the two main manufacturers. At the moment most passengers don't even know how many engines the blasted aeroplane has, leave alone which of the two major firms built it.........



"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
User currently offlinesw733 From United States of America, joined Feb 2004, 6324 posts, RR: 9
Reply 12, posted (3 years 6 months 1 week 6 days 14 hours ago) and read 14326 times:

Quoting SKAirbus (Reply 10):
surely a twin aisle aircraft with the same passenger capacity as the 737-800/900 would be heavier?

The only thing I can think of is perhaps it can carry more cargo, making it economically-feasible despite its larger size...I admit that while I am an economics nerd, I know little real info about airline economics.


User currently offlineAesma From France, joined Nov 2009, 6655 posts, RR: 11
Reply 13, posted (3 years 6 months 1 week 6 days 13 hours ago) and read 14088 times:

That 797/783bis would cost a fortune compared to a 739/A321.


New Technology is the name we give to stuff that doesn't work yet. Douglas Adams
User currently offlineStitch From United States of America, joined Jul 2005, 30986 posts, RR: 86
Reply 14, posted (3 years 6 months 1 week 6 days 13 hours ago) and read 14064 times:
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Quoting rheinwaldner (Reply 3):
Using the 787 cross section and add a short range wingset has some merits (hints A300, A310, mega cities) ...
Quoting NAV20 (Reply 5):
To put it shortly, surely it was tried with the (cancelled) B783?

Exactly. Beyond about 500km, the 787-8 is more efficient, even with an extra 10t of empty weight, thanks to it's greater wing area.

[Edited 2011-03-10 09:23:22]

User currently offlineNAV20 From Australia, joined Nov 2003, 9909 posts, RR: 35
Reply 15, posted (3 years 6 months 1 week 6 days 13 hours ago) and read 14062 times:

Quoting Aesma (Reply 13):
That 797/783bis would cost a fortune compared to a 739/A321.

Why, Aesma?



"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 16, posted (3 years 6 months 1 week 6 days 13 hours ago) and read 14031 times:

Quoting SKAirbus (Thread starter):
I think this would benefit customers by offering a common cockpit and simplified maintenance procedures.

Any ideas?

You can offer common cockpit and simplified maintenance procedures without holding cross section (e.g. 757/767). The major problem with this idea is drag...you can't shrink the length of 787 cross-section down to where it's in the 737 size class and not ruin the fineness ration of the fuselage, making it draggy. There's a reason the fuselage proportions of aircraft tend to be pretty tightly clustered.

Tom.


User currently offlinejonnyclark From United Kingdom, joined Feb 2011, 116 posts, RR: 0
Reply 17, posted (3 years 6 months 1 week 6 days 8 hours ago) and read 13030 times:

Funny, I think this decision is based purely on their customer's profile. most of the boeing 737 series (especially 800 series) are operated by LCC's, which most have a very short turn around time on their aircraft. The airlines would make more profit by having less trips, but more passengers (or generally more passengers) and i am sure that the tight turnaround times are unfeasable with more than 180 odd passengers on a single aisle config (have you ever been on an FR flight? in the middle of the plane, it can take 10 mins just to get off!) Dual aisle provide a faster boarding time. Plus they become more preferential with seating. How many people get really hacked off when they get the middle seat?

I think it's a good idea, and from what i can tell from the general aviation training i'm doing as a trainee ATPL pilot, i can't sense any great weight penalties from increasing the fuselage diameter by a small amount, compared to the increase in payload. As most of a frame's weight is due it's fuel and wing characteristics. Not that i need to preach that to you guys!

and is it just me, or did ATA used to fly 757's with a 2 x 2 x 2 config? Or 2 x 3 x 2 (with really narrow seats?)



Jonny, commercial pilot & founder of Thedesignair
User currently offlineAesma From France, joined Nov 2009, 6655 posts, RR: 11
Reply 18, posted (3 years 6 months 1 week 6 days 8 hours ago) and read 12586 times:

Quoting NAV20 (Reply 15):
Why, Aesma?

737-900ER list price is $85.8 million

787-800 list price is 100 millions more !



New Technology is the name we give to stuff that doesn't work yet. Douglas Adams
User currently offlinerikkus67 From Canada, joined Jun 2000, 1646 posts, RR: 1
Reply 19, posted (3 years 6 months 1 week 6 days 7 hours ago) and read 11602 times:

Perhaps the only reusable part would be the cockpit. Much like the 777 uses the same section (cockpit/nose) of the 767...except in this case, the larger plane -787- is built first.

Even the 757's cockpit was designed to be able to use a single certification for pilots on the 57/67, and has similar cockpit windows....

history repeating itself, like the 07/27/37 before them...


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User currently offlinerikkus67 From Canada, joined Jun 2000, 1646 posts, RR: 1
Reply 20, posted (3 years 6 months 1 week 6 days 6 hours ago) and read 11542 times:

Quoting tdscanuck (Reply 16):
The major problem with this idea is drag...

Boeing was unable to use much more than JUST the cockpit section of the 767 vs the 777. The transitional piece between the cockpit and main fuselage did provide a challenge.



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User currently offlinehannahpa From United States of America, joined Mar 2010, 128 posts, RR: 0
Reply 21, posted (3 years 6 months 1 week 6 days 6 hours ago) and read 11055 times:
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If the 797 will seat 2-2-2 in Y class, and still be a twin-aisle, what would the F/J class be 1-1-1? Or 1-2-1?

User currently offlinegoblin211 From United States of America, joined Jun 2010, 1209 posts, RR: 0
Reply 22, posted (3 years 6 months 1 week 6 days 5 hours ago) and read 10727 times:

The way i see it, Boeing will have to pull out a completely new design out of their hats when they do it. every a/c made has some kind of distinguishing feature that makes it stand out aerodynamically and internally as well. in other words it has to be innovative and basing it off of the 787 wouldn't sell.


From the airport with love
User currently offlineyendig From United Kingdom, joined Mar 2006, 145 posts, RR: 0
Reply 23, posted (3 years 6 months 1 week 6 days 5 hours ago) and read 10622 times:
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If Boeing go 2-2-2, it doesn't mean they're going to increase drag in doing so. They've talked of widening the fuselage, yes, but also (I believe, though could be wrong) making it an ellipsoid in shape. They'll keep similar frontal area to the 737 by lowering ceiling height slightly, therefore no drag penalty. Think of a soft, very squishy ball. Unsquashed, it's perfectly circular (737). Squash it onto a flat surface and it gets wider (797). The frontal area is still the same, just redistributed.

With my (very limited) understanding of aerodynamics, I believe there would be drag penalties if they were to base the new aircraft on the body of the 787. Am I correct in thinking that the longer an object is, the easier it is to make it more aerodynamically efficient? If so, a shortened 787 will be less efficient than a whole new type optimised for the correct lengths. Not to mention, as others have before me, that the 787-3 was already offered to airlines and politely refused....

One final point, would an ellipsoidal fuselage have any benefit from a lift vs drag point of view? I believe it might - perhaps someone with greater knowlege than I could shed some light on the matter?

Either way, I'm looking forward already to another new shape in the sky!


User currently offlineYXwatcherMKE From United States of America, joined May 2007, 1003 posts, RR: 2
Reply 24, posted (3 years 6 months 1 week 6 days 5 hours ago) and read 10244 times:

The idea of a twin-aisle A/C for the 737 replacement is to make de-planeing and loading the a/c as quickly as possible, primarily for an airline like WN, but lets face it other carriers want the same thing. The longer the a/c is on the ground the less money it makes for the airline. A clean sheet a/c is the best way to go, yes maybe using some old ideas from previous designs there nothing wrong with that. But to take the 787 and shrinking it still would need to a complete new design because you just can't take a plan and run it through the copier to make the new a/c.


I miss the 60's & 70's when you felt like a guest on the plane not cattle like today
25 Aesma : With that idea, I think the bins would be smaller, and the cargo hold too.
26 COS777 : Not quite-if you squash it all the way the area is essentially zero. A circle has the largest area for a given circumference. The elliptical design w
27 prebennorholm : Ellipsoid shaped fuselage won't work on a pressurized fuselage. The pressure will always try to convert the shape to circular. Trying to prevent that
28 Post contains images yendig : Thanks for putting me straight, guys! Just goes to show that you never stop learning I do hope Boeing can find a way of making the 2-2-2 layout work;
29 tdscanuck : Generally yes. High fineness ratio (length over width) is generally good aerodynamics. High fineness ratio is structurally heavy there, so there's a
30 yendig : Would there be any benefit to an airframer 'pinching' the side-of-body (like the SR71) on a passenger aircraft? Would this help the fuselage generate
31 BMI727 : Quite possibly, and Boeing showed a design concept called Honeydew (I think) that shows this characteristic. Basically, yes. This sort of configurati
32 Post contains images Stitch :
33 Post contains images yendig : I've somehow managed to miss the 'Honeydew' project - thanks for posting some info It looks really interesting, certainly waaaaaaay better than yet an
34 flybyguy : You liken building airplanes to a big Lego project. Sadly that isn't how things are really done. You can't just shrink a 787 to make it a 737 replace
35 DocLightning : Turnaround time. On a narrowbody, passengers seated up front come aboard, there's no space in the overhead for their bag, they proceed to the rear, s
36 BMI727 : Of course the other half to this story is that the 757 probably moved you at a cost that the 767 could not match. Furthermore, the 737 replacement wi
37 tdscanuck : I'm not sure why it was originally on the Blackbird, but it's generally dangerous (from a design integrity standpoint) to take high supersonic design
38 yendig : Thanks Tom, but wouldn't a suitably speed-adjusted 'pinch' improve the lift / drag ratio of the 797, to the benefit of overall performance?[Edited 201
39 Post contains images rheinwaldner : Except for wings!
40 Carls : There is another thread about Boeing anouncing the 797 at Paris Air Show. And I made the very same question. What the advantage of 2x2x2 could be ove
41 Carls : I was in a 747 and the same thing happened to me, I had to go up to six rows back and then when I was trying to go back to my seat I had to wait at t
42 tdscanuck : The lift/drag ratio of the pinch can never be as high as the wing (for conventional configurations). Since total lift is, at best, fixed, moving lift
43 NZ2 : We need to remember that it is a narrow body with twin aisles, so fusalage width it not that much greater than the current 737. Why do it, well if yo
44 Post contains images yendig : Gotta love this site - so many knowledgable contributors! Thanks for clearing things up for me, Tom
45 bmacleod : Good ideas; not sure though if Boeing is thinking along these lines..... I was thinking of something like the 747SP or A310 a "stubby" version of the
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