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Boeing Eliptical Fuselage 777 Replacement?  
User currently offlinemorrisond From Canada, joined Jan 2010, 244 posts, RR: 0
Posted (2 years 1 month 2 weeks 5 days 22 hours ago) and read 15501 times:

Now that it seems like Boeing will delay the 777X into the 2020's it's brings a wholescale replacement into the picture.

If they are going to go traditional tube and wing a 10W new Barrel seems like somewhat of a waste seeing that they just designed a perfectly good 9W one (787), so why not go 11W or even 12W.

One of the 737 replacement studies was a 7W twin aisle eliptical fuselage design with roughly the same cross section (maybe 1% more) than A320.

With Boeing starting to master large scale composite construction how attractive would a 11W eliptical cross section be with roughly the same frontal area as the existing 777 barrel?

At 11W how long would a Eliptical Y3 have to be to have 77W capacity? At 80M long what would typical capacity be?

Would 115K engines be enough?

15 replies: All unread, jump to last
 
User currently offlinemorrisond From Canada, joined Jan 2010, 244 posts, RR: 0
Reply 1, posted (2 years 1 month 2 weeks 5 days 21 hours ago) and read 15418 times:

Article from Flight Global on eliptical 737

http://www.flightglobal.com/blogs/fl...oeing-patent-may-provide-glim.html


User currently offlineStitch From United States of America, joined Jul 2005, 31418 posts, RR: 85
Reply 2, posted (2 years 1 month 2 weeks 5 days 18 hours ago) and read 14727 times:
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Depending on how the surface area works out, parasitic drag might be worse with an elliptical fuselage compared to a circular one. It will also need more reinforcement as a pressure vessel (though CFRP will probably help there). You also need to consider how the wings and wingbox integrate since your passenger deck will be closer to the bottom of the fuselage. And you also have a minimum height down below defined by LD3 dimensions.

Airbus has looked at it for a concept as a horizontal double-bubble encased in a larger structure.

Airbus UHCA Concept with "horizontal double-bubble" parallel cabins


User currently offlineXT6Wagon From United States of America, joined Feb 2007, 3432 posts, RR: 4
Reply 3, posted (2 years 1 month 2 weeks 5 days 18 hours ago) and read 14656 times:

Quoting morrisond (Reply 2):
How would it compare to A350-1000 - could it beat A380-800 or 900 with XWB engines?

Wouldn't this be an exceptional aircraft for EK ?

A 10Y size could compete well against the A351, at 11Y it would be a size class larger atleast as you would need the length to have meaningful cargo space and operating economics. Which might be good if you can keep the trip costs close enough to the smaller plane, it is afterall what we have seen in A380 vs 748i contests. The 748i is cheaper to operate, but the A380 is more than close enough to make its extra size be only an asset.

That said, if you go to 11Y, you may still want a near circular cross section as the potential for taller cargo containers starts to get easier to justify. More volume mean more revenue per flight.


User currently offlineBMI727 From United States of America, joined Feb 2009, 15833 posts, RR: 27
Reply 4, posted (2 years 1 month 2 weeks 5 days 18 hours ago) and read 14631 times:

Quoting Stitch (Reply 3):
Depending on how the surface area works out, parasitic drag might be worse with an elliptical fuselage compared to a circular one.

A cylinder gives the best volume to surface area, but you might be able to reduce the surface area for a given passenger and cargo space by going elliptical and not have to deal with stuff like the crown space on the 747-8. A circular cross section for ten or more seats is going to have a lot of wasted space in the crown and probably some below the hold too. Also, don't forget that you can probably get some lift from a flatter fuselage if you're smart about it.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlineDocLightning From United States of America, joined Nov 2005, 20343 posts, RR: 59
Reply 5, posted (2 years 1 month 2 weeks 5 days 16 hours ago) and read 14215 times:

Quoting Stitch (Reply 2):
Depending on how the surface area works out, parasitic drag might be worse with an elliptical fuselage compared to a circular one. It will also need more reinforcement as a pressure vessel (though CFRP will probably help there). You also need to consider how the wings and wingbox integrate since your passenger deck will be closer to the bottom of the fuselage. And you also have a minimum height down below defined by LD3 dimensions.

The only circular cross-section of which I'm aware is the 777. All others are eliptical, but the long axis is vertical. They are reinforced by the floor beams.

The issue is that the reinforcement must be vertical when the long axis is horizontal. Except that CFRP is a lot stiffer and newer forms might be able to compensate for the structural needs.

I don't think we'll see more than 11Y (3-5-3) because once you get over that, you run into issues with aisle access for safety reasons and number of exits per passenger. Passengers may not be more than two seats from the aisle, so any wider and you'd have to go 3-3-3-3- or 3-4-4-3 or even 3-5-5-3, but at that point you are adding an extra aisle, which takes up yet more cabin width. If you're going to go for that sort of width, you might as well go the whole hog and do a hybrid or full BWB.

But when you go for that sort of width, you now have less surface area per passenger and that becomes a problem for emergency egress. Every exit door adds weight and takes up space and if each aisle has 12, 14, or 16 pax, you need an awful lot of doors per aisle as compared to a narrower fuselage.

Ultimately, I think that's why Airbus went with the double-deck design over a single wide fuselage.


User currently offlinemafi29 From Germany, joined Nov 2010, 58 posts, RR: 0
Reply 6, posted (2 years 1 month 2 weeks 5 days 15 hours ago) and read 13867 times:

Quoting DocLightning (Reply 5):
I don't think we'll see more than 11Y (3-5-3) because once you get over that, you run into issues with aisle access for safety reasons and number of exits per passenger. Passengers may not be more than two seats from the aisle, so any wider and you'd have to go 3-3-3-3- or 3-4-4-3 or even 3-5-5-3,

Not necessarily, 12Y is also possible in a 3-6-3 configuration as not pax is more than two seat from the aisle. If that is a comfortable configuration is an other question  


User currently offlinencfc99 From United Kingdom, joined May 2005, 752 posts, RR: 0
Reply 7, posted (2 years 1 month 2 weeks 5 days 14 hours ago) and read 13830 times:

Quoting DocLightning (Reply 5):

Regarding number of exits, do wider doors offer a solution, more people out of each door in an emergency?


User currently offlinemorrisond From Canada, joined Jan 2010, 244 posts, RR: 0
Reply 8, posted (2 years 1 month 2 weeks 5 days 14 hours ago) and read 13760 times:

Quoting Stitch (Reply 2):
Depending on how the surface area works out, parasitic drag might be worse with an elliptical fuselage compared to a circular one. It will also need more reinforcement as a pressure vessel (though CFRP will probably help there). You also need to consider how the wings and wingbox integrate since your passenger deck will be closer to the bottom of the fuselage. And you also have a minimum height down below defined by LD3 dimensions.

I would assume the surface area would be the same as the area of the ellipse would be roughly equal to a circle- the Cabin Width would need to be approximately 32" wider to accommodate 11 18" seats in Y, however you could easily take 28" out of the vertical of the fuselage to get the same area - Your dimensions would be roughly 276" wide and 216" high - or only 6" shorter than an A330 fuselage which can accomodate LD3's - meaning 3" taken out of the cargo area - it might have to be a few inches higher - but with the flatter elipse it might work.

Interesting to think about and one of the beauty of composites - non - standard shapes are a lot easier.


User currently offlinebonusonus From United States of America, joined Nov 2009, 403 posts, RR: 0
Reply 9, posted (2 years 1 month 2 weeks 5 days 12 hours ago) and read 11695 times:

Quoting ncfc99 (Reply 7):
Regarding number of exits, do wider doors offer a solution, more people out of each door in an emergency?

It might, but a wider door starts to require a significantly stronger/heavier door frame/surrounding structure.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 10, posted (2 years 1 month 2 weeks 5 days 11 hours ago) and read 10805 times:

Quoting morrisond (Thread starter):
If they are going to go traditional tube and wing a 10W new Barrel seems like somewhat of a waste seeing that they just designed a perfectly good 9W one (787), so why not go 11W or even 12W.

If 10W was the right cross-section for the 777, it's still the right cross section for that market. None of the technology changes have altered the basic relationship there.

Quoting morrisond (Thread starter):
One of the 737 replacement studies was a 7W twin aisle eliptical fuselage design with roughly the same cross section (maybe 1% more) than A320.

You actually work out better (at least on fuel burn) but going even shorter/wider with 8W twin aisle (2-4-2).

Quoting ncfc99 (Reply 7):
Regarding number of exits, do wider doors offer a solution, more people out of each door in an emergency?

They help get exit capacity up but they don't get you out of the rule about being X seats away from an aisle...wider doors don't help if you can't get out of your seat in time. You also have an issue with too many people trying to go down a standard aisle if your seats-to-aisles ratio gets out of whack.

Tom.


User currently offlineDocLightning From United States of America, joined Nov 2005, 20343 posts, RR: 59
Reply 11, posted (2 years 1 month 2 weeks 5 days 10 hours ago) and read 10000 times:

Quoting ncfc99 (Reply 7):

Regarding number of exits, do wider doors offer a solution, more people out of each door in an emergency?

That was the solution for the 747. The issue is that on the 747 each door uses about 1.5 Y rows. The 747 has 5 exits on each side, so that's 7 Y rows or 70 pax that can't be flown because of the exits. OK, in reality the center seats can be left in place, so that's 42 pax (6x7). (I'm not saying safety is unimportant, but these calculations go into the aircraft design and purchasing decisions by the OEM and the customer, respectively.) The wider the doors, the more "wasted" space aboard.

The wider the cabin, the more doors are required to allow for complete evacuation in 90 seconds.

Quoting mafi29 (Reply 6):
Not necessarily, 12Y is also possible in a 3-6-3 configuration as not pax is more than two seat from the aisle. If that is a comfortable configuration is an other question

Ooh, clever! I hadn't thought of that. Of course, it's Y, so comfort is about the 60th consideration.


User currently offlinemorrisond From Canada, joined Jan 2010, 244 posts, RR: 0
Reply 12, posted (2 years 1 month 2 weeks 5 days 10 hours ago) and read 9979 times:

Quoting tdscanuck (Reply 10):
If 10W was the right cross-section for the 777, it's still the right cross section for that market. None of the technology changes have altered the basic relationship there.

I wouldn't call the ability to be build efficient elliptical cross sections out of composites a immaterial technological change and if you are going wider than 9W(an elliptical 9W may not have enough room for LD3's) you might as well go 11W as per my example above where you have a cross section with the same area as a 777 - still accomodate LD3's but gain an extra seat and possibly go 12W with the same seat width as 777 at it's current 10W width


User currently offlineBE77 From Canada, joined Nov 2007, 455 posts, RR: 0
Reply 13, posted (2 years 1 month 2 weeks 5 days 1 hour ago) and read 5881 times:

Quoting DocLightning (Reply 5):
3-5-5-3
Quoting mafi29 (Reply 6):
3-6-3

     
Economically going wider makes a world of sense, and it likely will happen as soon as the technology allows it (or a bit sooner like the 380 and 787).
But, when you configure it, I have visions of being in seat 28F on a 10 hour flight connecting to the world Sumo wrestling convention.



Tower, Affirmitive, gear is down and welded
User currently offlineSasha From Russia, joined May 1999, 861 posts, RR: 0
Reply 14, posted (2 years 1 month 2 weeks 5 days 1 hour ago) and read 5796 times:

Quoting Stitch (Reply 2):
Airbus has looked at it for a concept as a horizontal double-bubble encased in a larger structure.

interesting but ugly. also means even smaller window/middle seat ratio. it will be very hard to book a window seat on such a plane  



An2/24/28,Yak42,Tu154/134,IL18/62/96,B737/757/767,A310/320/319,F100,BAe146,EMB-145,CRJ,A340-600,B747-400,A-330-300,A-340
User currently offlineBE77 From Canada, joined Nov 2007, 455 posts, RR: 0
Reply 15, posted (2 years 1 month 2 weeks 5 days ago) and read 5375 times:

Quoting Sasha (Reply 14):
it will be very hard to book a window seat on such a plane

Might be the same as booking F or J, which is to say it could be really easy...but expensive.



Tower, Affirmitive, gear is down and welded
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