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Could The Y-3 Become A Triple Aisle Design?  
User currently online747400sp From United States of America, joined Aug 2003, 3623 posts, RR: 2
Posted (4 years 8 months 1 week 3 days 1 hour ago) and read 9472 times:

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?

26 replies: All unread, showing first 25:
 
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17040 posts, RR: 66
Reply 1, posted (4 years 8 months 1 week 3 days ago) and read 9449 times:

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.


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineLaddie From United States of America, joined Jan 2010, 602 posts, RR: 8
Reply 2, posted (4 years 8 months 1 week 2 days 23 hours ago) and read 9449 times:

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.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17040 posts, RR: 66
Reply 3, posted (4 years 8 months 1 week 2 days 21 hours ago) and read 9416 times:



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.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineDocLightning From United States of America, joined Nov 2005, 19722 posts, RR: 58
Reply 4, posted (4 years 8 months 1 week 2 days 12 hours ago) and read 9336 times:



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?


User currently offlineSEPilot From United States of America, joined Dec 2006, 6910 posts, RR: 46
Reply 5, posted (4 years 8 months 1 week 2 days 9 hours ago) and read 9291 times:

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
User currently offlineDocLightning From United States of America, joined Nov 2005, 19722 posts, RR: 58
Reply 6, posted (4 years 8 months 1 week 2 days 4 hours ago) and read 9208 times:



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.


User currently offlineLaddie From United States of America, joined Jan 2010, 602 posts, RR: 8
Reply 7, posted (4 years 8 months 1 week 2 days 1 hour ago) and read 9178 times:



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.


User currently offlineDocLightning From United States of America, joined Nov 2005, 19722 posts, RR: 58
Reply 8, posted (4 years 8 months 1 week 1 day 21 hours ago) and read 9148 times:



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.


User currently offlineJoeCanuck From Canada, joined Dec 2005, 5471 posts, RR: 30
Reply 9, posted (4 years 8 months 1 week 1 day 21 hours ago) and read 9140 times:



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...?
User currently offlineDocLightning From United States of America, joined Nov 2005, 19722 posts, RR: 58
Reply 10, posted (4 years 8 months 1 week 1 day 21 hours ago) and read 9134 times:



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.


User currently offlineTF39 From United States of America, joined Jul 2006, 110 posts, RR: 0
Reply 11, posted (4 years 8 months 1 week 1 day 20 hours ago) and read 9121 times:

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.

User currently offlineLaddie From United States of America, joined Jan 2010, 602 posts, RR: 8
Reply 12, posted (4 years 8 months 1 week 1 day 13 hours ago) and read 9086 times:



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.


User currently offlineSEPilot From United States of America, joined Dec 2006, 6910 posts, RR: 46
Reply 13, posted (4 years 8 months 1 week 1 day 12 hours ago) and read 9078 times:



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
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 14, posted (4 years 8 months 1 week 1 day 10 hours ago) and read 9044 times:



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.


User currently offlineKeesje From , joined Dec 1969, posts, RR:
Reply 15, posted (4 years 8 months 1 week 5 hours ago) and read 8935 times:

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.



User currently offlineLaddie From United States of America, joined Jan 2010, 602 posts, RR: 8
Reply 16, posted (4 years 8 months 1 week 5 hours ago) and read 8922 times:



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....


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17040 posts, RR: 66
Reply 17, posted (4 years 8 months 1 week 1 hour ago) and read 8879 times:



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



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineKeesje From , joined Dec 1969, posts, RR:
Reply 18, posted (4 years 8 months 6 days 19 hours ago) and read 8764 times:

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


User currently offlineChase From United States of America, joined Nov 2005, 1054 posts, RR: 0
Reply 19, posted (4 years 8 months 6 days 10 hours ago) and read 8684 times:



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.


User currently offlineDocLightning From United States of America, joined Nov 2005, 19722 posts, RR: 58
Reply 20, posted (4 years 8 months 6 days 9 hours ago) and read 8657 times:



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.


User currently offlineLaddie From United States of America, joined Jan 2010, 602 posts, RR: 8
Reply 21, posted (4 years 8 months 5 days 23 hours ago) and read 8552 times:



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.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17040 posts, RR: 66
Reply 22, posted (4 years 8 months 5 days 22 hours ago) and read 8545 times:



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



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineKeesje From , joined Dec 1969, posts, RR:
Reply 23, posted (4 years 8 months 5 days 19 hours ago) and read 8515 times:



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


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17040 posts, RR: 66
Reply 24, posted (4 years 8 months 5 days 18 hours ago) and read 8508 times:



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.



"There are no stupid questions, but there are a lot of inquisitive idiots."
25 Laddie : You just had to bring up the issue of barfing, didn't you? (pun intended) The Aero guys definitely love the BWB because one gets the ideal spanloadin
26 DocLightning : Yes, but to date, not enough to overcome the significant operational and technical penalties that come with the design.
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