remcor
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What's The Diff Between The 787-3 And 787-8?

Sun Sep 17, 2006 11:48 am

The 783 is a high-cap shorter range aircraft to replace the A300 and sorts, right?

My understanding is that the fuselage length is the same between the 787-3 and 787-8. I may be wrong but I haven't heard of a different wing between the two models. So is the 787-3 just a high-density configured 787-8 with fewer fuel tanks to trade range for capacity? Why not just get a 787-8 and use the tanks only half full (or less)? How much weight do the tanks really add?
 
CHIFLYGUY
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RE: What's The Diff Between The 787-3 And 787-8?

Sun Sep 17, 2006 11:56 am

The 788 and 783 definitely have very different wings. Some have said that carriers will prefer to "misuese" 788/789 rather than order the 783, but I'm not sure what the minimum economically feasible range of former planes' wings is. I've heard that the 788 wing is majorly optimized for cruise vs. climb, which could really hurt short range economics.

If Boeing gets it right, the 783 could be a sleeper hit, serving Japan, India, and China domestic routes; US transcon, Hawaii, and short range intl as well as other high density short haul where cargo handling is key. Even for replacement, there were a lot of A300's sold and Airbus doesn't have a replacement aircraft in the works at all. Right now the 783 lacks trans-atlantic range at only 3,500 miles, unlike the 764, which might scare US carriers off.
 
airlinelover
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RE: What's The Diff Between The 787-3 And 787-8?

Sun Sep 17, 2006 12:26 pm

Umm.. 5?


Chris
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futurecaptain
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RE: What's The Diff Between The 787-3 And 787-8?

Sun Sep 17, 2006 12:49 pm

Quoting Remcor (Thread starter):
I may be wrong but I haven't heard of a different wing between the two models

That's correct.
787-8 - 197 ft wing span
787-3 - 170 ft wing span

Main differences are in range and MTOW.

I guess it saves weight also by carrying around 27 less feet of wing too? Wonder how much that helps.
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Lemurs
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RE: What's The Diff Between The 787-3 And 787-8?

Sun Sep 17, 2006 2:25 pm

Quoting Futurecaptain (Reply 3):
I guess it saves weight also by carrying around 27 less feet of wing too? Wonder how much that helps.

It helps quite a bit, but it's not everything...remember that it's not just the extra 27ft of material hanging off the ends, but how much stronger the rest of the wing has to be to handle the longer moment arm of that extra span...all that extra weight PLUS extra lift means the load bearing parts of the wing have to be that much stronger.

Think of it in smaller terms. If you have a piece of fairly stiff plastic, you can make a 6 inch strip that's very sturdy and strong and will support a fairly heavy weight. That same width/thickness strip stretched out to 3 feet long however would need to be thicker or made of a stronger material to support the same kind of weight out at it's ends without putting undue stress on it in the middle...simply because it would need to support it's OWN weight as well.

That's part of the reason why original (pre-2001?) 737NG's can't just have winglets slipped on...parts of the wing need strengthening to handle the extra weight and lift out there, since it was already highly optimized to be as light as possible.
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brendows
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RE: What's The Diff Between The 787-3 And 787-8?

Sun Sep 17, 2006 7:26 pm

Quoting Remcor (Thread starter):
I may be wrong but I haven't heard of a different wing between the two models.

One important reason for not using a 788 is the wing span, the extra 27 feet on the 788 reduces the number of domestic gates it can fit into dramatically.
It seems like the 783 will have the same wing as the 788, it's just 27 feet shorter ("cut" just on the out side of the ailerons,) with the addition of blended winglets.

Quoting Remcor (Thread starter):
Why not just get a 787-8 and use the tanks only half full (or less)? How much weight do the tanks really add?

The 788 is optimized for long haul, both in terms of wing design and structural strength, and isn't the optimal aircraft for domestic flights in Japan (and other similar distances,) hence the 783. I've read that the 783 will have the same fuel tanks as the 788, but most of the fuel volume will not be used. The 783 won't be that much lighter than the 788 (only something like 7,5 tonnes,) mostly because it shares so much of the design with the 788, and that it has to be reinforced to handle the higher number of cycles.

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