747400sp
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Could The Y-3 Become A Triple Aisle Design?

Fri Jan 15, 2010 3:34 am

In 1999, Boeing had a triple aisle design that look like an en large 777 with four engines. Now this design was had a capacity that was larger than a 747 400 and smaller than an A380, so it would have been closer to the larger Y-3 capacity. Could Boeing use a triple aisle design using a 787 section 41, with either two or four engines for the Y-3?
 
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Starlionblue
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RE: Could The Y-3 Become A Triple Aisle Design?

Fri Jan 15, 2010 4:43 am

I have a feeling you'd get a lighter aircraft if you went double decker. Airbus looked at basically putting two 340 fuselages side by side when they were sketching the 380. Too heavy.
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Laddie
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RE: Could The Y-3 Become A Triple Aisle Design?

Fri Jan 15, 2010 5:09 am

Come to think of it, the forward half of a 747-400 is a triple aisle: two aisles below, and one aisle above! And it's a four-engine design too. Hmm...

Quoting Starlionblue (Reply 1):
Airbus looked at basically putting two 340 fuselages side by side when they were sketching the 380. Too heavy.

I believe the double-lobe design was too heavy because of the structure that tied the two lobes together. Taking out the loads that peaked at the intersection of the lobes required some beefy structure.

A four-engine design is a no-go as it is usually heavier and burns more fuel than a twin-engine. In today's world of powerful turbofans it is good to remember: Don't do with four engines what can more efficiently be done with two.
 
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Starlionblue
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RE: Could The Y-3 Become A Triple Aisle Design?

Fri Jan 15, 2010 7:44 am



Quoting Laddie (Reply 2):
A four-engine design is a no-go as it is usually heavier and burns more fuel than a twin-engine. In today's world of powerful turbofans it is good to remember: Don't do with four engines what can more efficiently be done with two.

True. However that depends on the size of the design. If it is significantly larger than a 777-300, there's no engine powerful enough today to make it a twin. Such an engine could conceivably be developed, but the R&D costs for such a comparatively small market might make the quad option more economical.
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DocLightning
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RE: Could The Y-3 Become A Triple Aisle Design?

Fri Jan 15, 2010 4:07 pm



Quoting 747400sp (Thread starter):
In 1999, Boeing had a triple aisle design that look like an en large 777 with four engines. Now this design was had a capacity that was larger than a 747 400 and smaller than an A380, so it would have been closer to the larger Y-3 capacity. Could Boeing use a triple aisle design using a 787 section 41, with either two or four engines for the Y-3?

You run into a serious problem with structural efficiency. Your options are to have a double-bubble design, which is weighty, or a vast cylinder with even more wasted overhead space than the 777 and 747.

Keesje has a few good cross-section diagrams. Keesje??? Where are you?
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SEPilot
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RE: Could The Y-3 Become A Triple Aisle Design?

Fri Jan 15, 2010 7:03 pm

Anything with a single deck wider than the current 777 wastes way too much space if round, and is structurally inefficient if not. There will not be a wider single deck airliner than the 777.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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RE: Could The Y-3 Become A Triple Aisle Design?

Sat Jan 16, 2010 12:58 am



Quoting SEPilot (Reply 5):
There will not be a wider single deck airliner than the 777.

Well, the 747, and you could argue that the -100 is *almost* a single-decker. But you are correct, 777 is pretty much pushing it for the "tube with wings" design. Now, if you wanted to go for a BWB (and all the operational, technical, and engineering joy that brings with it), you could do a whole bunch of aisles.
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Laddie
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RE: Could The Y-3 Become A Triple Aisle Design?

Sat Jan 16, 2010 3:53 am



Quoting DocLightning (Reply 4):
Your options are to have a double-bubble design, which is weighty, or a vast cylinder with even more wasted overhead space than the 777 and 747.

How about a squashed fuselage (i.e., ellipse) that is wider than it is tall? That would reduce the wasted space upstairs. I'm not sure how the hoop loads would work when the fuselage is pressurized. Or what the windows would look like. Just throwing out ideas here in a valiant effort to get this triple-aisle idea to work...

I know a twin-aisle narrowbody with an elliptical cross-section was patented by Boeing last year, so there is hope here.
 
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RE: Could The Y-3 Become A Triple Aisle Design?

Sat Jan 16, 2010 7:03 am



Quoting Laddie (Reply 7):

How about a squashed fuselage (i.e., ellipse) that is wider than it is tall?

It's not a very good design for a pressure vessel. You would need to reinforce it, probably with a wall down the middle, and that would add weight and decrease space.
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JoeCanuck
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RE: Could The Y-3 Become A Triple Aisle Design?

Sat Jan 16, 2010 7:26 am



Quoting DocLightning (Reply 8):
It's not a very good design for a pressure vessel. You would need to reinforce it, probably with a wall down the middle, and that would add weight and decrease space.

Not necessarily. The floor would prevent a flattened oval from going round under pressure. A wall wouldn't be needed, rather a few posts, tying in to a keel beam would suffice for longitudinal stiffness.

Few people seem to think a BWB is structurally inefficient and it is a very squashed oval.

Any added weight might be offset by an increase in aerodynamic efficiency as the shape begins to approach a BWB. It would be, if properly done, a step in the BWB direction.

Or they may just say bugger it and go right to the BWB thing. It would be the ultimate game changer of all time...

Well...a guy can dream, right...?
What the...?
 
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RE: Could The Y-3 Become A Triple Aisle Design?

Sat Jan 16, 2010 7:57 am



Quoting JoeCanuck (Reply 9):

Not necessarily. The floor would prevent a flattened oval from going round under pressure. A wall wouldn't be needed, rather a few posts, tying in to a keel beam would suffice for longitudinal stiffness.



Quoting JoeCanuck (Reply 9):

Few people seem to think a BWB is structurally inefficient and it is a very squashed oval.

Yes, but in that case, there are benefits to that oval construction. In the case of a single-decker with three aisles, it's still a tube with wings, so that benefit is less significant.

Also, what will be the density? 3-5-5-3 is the largest they can do. That's 16 per row. Keeje's "Greenliner" is 15-abreast design (could be 16 with minor changes to the design or using skinnier seats) that offers far superior structural efficiency to a single-deck design.
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tf39
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RE: Could The Y-3 Become A Triple Aisle Design?

Sat Jan 16, 2010 8:47 am

Just a quick question - are folks here assuming traditional aluminum (or other metal) construction or carbon fiber? You have more design options with CF so what's not possible with aluminum could be reality with CF.
 
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Laddie
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RE: Could The Y-3 Become A Triple Aisle Design?

Sat Jan 16, 2010 3:29 pm



Quoting JoeCanuck (Reply 9):
Any added weight might be offset by an increase in aerodynamic efficiency as the shape begins to approach a BWB. It would be, if properly done, a step in the BWB direction.

A BWB is an option, but there are serious design challenges for a passenger jet:
1) Emergency egress: for the passengers in the middle it's a long way to the nearest door. And getting enough doors into the design is a challenge.
2) The passengers in the middle have no windows in sight, so claustorphobia is a concern.
3) IFE in each seatback that displays camera views of the outside world might help #2.
4) But a study done a few years ago showed that if there is even a small delay between what the passenger feels in his/her middle ear as the airplane moves (such as a turn) and what is shown on their IFE screen, then motion sickness can set in. This is especially pronounced for passengers on the outboard seats.

I am a big fan of BWB as a freighter.

Quoting TF39 (Reply 11):
Just a quick question - are folks here assuming traditional aluminum (or other metal) construction or carbon fiber? You have more design options with CF so what's not possible with aluminum could be reality with CF.

I am not wedded to aluminum. CF is fine, maybe even required for this big of a ship.

However, it's beginning to look like a double-decker is the way to go.
 
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RE: Could The Y-3 Become A Triple Aisle Design?

Sat Jan 16, 2010 4:03 pm



Quoting TF39 (Reply 11):
You have more design options with CF so what's not possible with aluminum could be reality with CF.

This is true; however the same structural problems arise. While, for example, a non-round cross section may be easier in CFRP than aluminum, so is round. The weight penalty may be less, but it is still there, and a round cross section will still be more efficient.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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RE: Could The Y-3 Become A Triple Aisle Design?

Sat Jan 16, 2010 6:42 pm



Quoting JoeCanuck (Reply 9):
Not necessarily. The floor would prevent a flattened oval from going round under pressure.

That's only if you run the floor in pure compression. That is, obviously, an option but it's going to be even heavier than running a wall down the middle (tension designs are virtually always lighter than compression ones).

Quoting JoeCanuck (Reply 9):
Few people seem to think a BWB is structurally inefficient and it is a very squashed oval.

The pressure vessel design on a BWB is one of it's huge potential drawbacks; this is a well known problem. That's one of the big reasons it's pretty widely assumed that a military freighter might be the first good spot for a BWB.

Tom.
 
keesje
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RE: Could The Y-3 Become A Triple Aisle Design?

Sun Jan 17, 2010 10:59 pm

Boeing looked at a widebody in the nineties. The 763-246 ;



Very wide cross sections are hard to fill in a revenue generating way. A quick sketch shows the issue. Structural efficiency is highest with a circular (or nearly circular) cross section.



The A380 has a kind of square circle, the 747 a dubble bubble and the 777 a perfect circle.

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RE: Could The Y-3 Become A Triple Aisle Design?

Sun Jan 17, 2010 11:30 pm



Quoting Keesje (Reply 15):
Boeing looked at a widebody in the nineties. The 763-246

That was a nice piece of history, Keesje. Thank you for sharing it.

I guess I won't bother submitting a patent disclosure for a squashed wide-body with three aisles. Sometimes I swear there just isn't anything new under the sun when it comes to airplane design!

However, I will say I like the idea of using the upstairs as a lounge. In that cross-section drawing of the -246, I think something might be made of the lounge upstairs if one takes away that center walkway. I can't imagine walking down such a narrow channel, and I think a flat floor all the way across would be more useful. Of course, that might mean lowering or eliminating the center stowbins....
 
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Starlionblue
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RE: Could The Y-3 Become A Triple Aisle Design?

Mon Jan 18, 2010 3:09 am



Quoting Laddie (Reply 16):
Sometimes I swear there just isn't anything new under the sun when it comes to airplane design!

Frustrating isn't it?  Wink Then again if you can come up with an SST concept for 50-100 people with a) less noise footprint than, say, a 737Classic, b) price per seat equivalent of current business class and c) trans-pacific range, I would say you would have something both new and marketable.  Wink
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keesje
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RE: Could The Y-3 Become A Triple Aisle Design?

Mon Jan 18, 2010 9:58 am

For those who have seen it. Airbus made a short clip displaying the different design options it studied for its VLA project that became the A380. If you use the play/pauze button you can see the various cross sections..



http://www.youtube.com/watch?v=SmigvHkBQIc
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RE: Could The Y-3 Become A Triple Aisle Design?

Mon Jan 18, 2010 6:09 pm



Quoting Laddie (Reply 12):
The passengers in the middle have no windows in sight, so claustorphobia is a concern.

I'm not a claustrophobia sufferer, but I don't see how this would really be all that different than sitting in the center a large restaurant, or perhaps a driver's license bureau...well, except that you'd know you can't leave.
 
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RE: Could The Y-3 Become A Triple Aisle Design?

Mon Jan 18, 2010 7:53 pm



Quoting Keesje (Reply 18):
For those who have seen it. Airbus made a short clip displaying the different design options it studied for its VLA project that became the A380. If you use the play/pauze button you can see the various cross sections..

The funniest part of the video is when an aircraft that is, for all intents and purposes, identical to the 744 appears.
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Laddie
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RE: Could The Y-3 Become A Triple Aisle Design?

Tue Jan 19, 2010 5:12 am



Quoting Starlionblue (Reply 17):
if you can come up with an SST concept for 50-100 people

Oh, is that all, Starlionblue? You only want it to cruise over water? That's easy because I don't have to worry about shock wave att

Quoting Chase (Reply 19):
I'm not a claustrophobia sufferer, but I don't see how this would really be all that different than sitting in the center a large restaurant, or perhaps a driver's license bureau...well, except that you'd know you can't leave.

You hit the nail on the head when you write "you'd know you can't leave." For those who suffer from claustrophobia, that is a very scary feeling indeed.

At any rate, I'm not saying a BWB can never work as a passenger airplane, As far as I know, there are no fatal flaws in the use of a BWB. Please correct me if I am wrong, fellow A.net-ers.
 
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Starlionblue
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RE: Could The Y-3 Become A Triple Aisle Design?

Tue Jan 19, 2010 6:06 am



Quoting Laddie (Reply 21):

Quoting Starlionblue (Reply 17):
if you can come up with an SST concept for 50-100 people

Oh, is that all, Starlionblue? You only want it to cruise over water? That's easy because I don't have to worry about shock wave att

Even just over water I think you'd have quite a few takers.  Wink
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keesje
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RE: Could The Y-3 Become A Triple Aisle Design?

Tue Jan 19, 2010 9:04 am



Quoting Laddie (Reply 21):
At any rate, I'm not saying a BWB can never work as a passenger airplane, As far as I know, there are no fatal flaws in the use of a BWB. Please correct me if I am wrong, fellow A.net-ers.

I think BWB have been around design offices for decades. I suspect their origins are with the Aerofynamic /tunnel guys. Aerosynamicaly is a good way of lifting a volume / mass in an efficient way.

I think the materials / structures people get shivers. Looking how much energy it costed the very experienced / well financed NASA / Boeing people to get the ( straight forward 787) design right, I wonder what it will take to do a seriosu BWB..


The concepts I've seen (several interconnected cilinders) seem very hard to model/ calculate to me & I really wonder how they could be more strutiral efficient/ lighter then a more cilindric like tube..

I think somebody mentioned passenger sickness. Currently passengers sit near the center of gravity. When an aircraft rolls with a certain rate the forces are not high. Imagine you are sitting 15 meters from the cog during a max roll rate. The g forces would be unknow to the regular public & I wonder if meals would stay on the table.. Just a detail, but I do not see an easy fix..

Some BWB concepts:http://www.twitt.org/bldwing.htm
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Starlionblue
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RE: Could The Y-3 Become A Triple Aisle Design?

Tue Jan 19, 2010 10:04 am



Quoting Keesje (Reply 23):
I think somebody mentioned passenger sickness. Currently passengers sit near the center of gravity. When an aircraft rolls with a certain rate the forces are not high. Imagine you are sitting 15 meters from the cog during a max roll rate. The g forces would be unknow to the regular public & I wonder if meals would stay on the table.. Just a detail, but I do not see an easy fix..

This is actually quite critical. Even many cargos might start "caring" with those g-forces. As Keesje says, imagine sitting in the middle of the wing. Now imagine that when the plane rolls. You might go 3-4 metres up or down in a second. Certainly this would mandate seat belts on for long periods, as pax, let alone lunches would not stay seated. And then there's the barfing.
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Laddie
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RE: Could The Y-3 Become A Triple Aisle Design?

Tue Jan 19, 2010 3:16 pm



Quoting Starlionblue (Reply 24):
And then there's the barfing.

You just had to bring up the issue of barfing, didn't you? (pun intended)

Quoting Keesje (Reply 23):
I think BWB have been around design offices for decades. I suspect their origins are with the Aerofynamic /tunnel guys. Aerosynamicaly is a good way of lifting a volume / mass in an efficient way.

The Aero guys definitely love the BWB because one gets the ideal spanloading and minimum drag from the design. A "tube and wing" design has a significant hole in its spanloading/lift because of the fuselage right in the middle of the wing. For a given gross weight, the BWB would have lower drag than a conventional design.

The Noise guys like it too because the engines can be shielded on the top of the fuselage. Fan noise will be much attenuated by the time it reaches the ground because of the shielding of the BWB.

All the issues listed above may mean we only see a BWB as a freighter, or refueling airplane, or airlift machine.
 
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DocLightning
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RE: Could The Y-3 Become A Triple Aisle Design?

Wed Jan 20, 2010 1:10 am



Quoting Laddie (Reply 25):

The Aero guys definitely love the BWB because one gets the ideal spanloading and minimum drag from the design. A "tube and wing" design has a significant hole in its spanloading/lift because of the fuselage right in the middle of the wing. For a given gross weight, the BWB would have lower drag than a conventional design.

Yes, but to date, not enough to overcome the significant operational and technical penalties that come with the design.
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