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Can The 787 Be Stretched?  
User currently offlineDL767captain From United States of America, joined Mar 2007, 2539 posts, RR: 0
Posted (7 years 2 months 2 weeks 2 days 17 hours ago) and read 2838 times:

There has been a lot of talk about the 787 being stretched to a -10 and even a -11, but is this possible?

Does anyone know what size the 767 was designed for? (as in the -200 or the -300)
When looking at the 767, if the plane was designed to be the size of the 767-200 the plane was then stretched to the -300 and finally the -400. So if the wings and everything were designed for the 762, then stretching it twice worked.

For the 787 it seems as if everything was developed for the 787-8 version. It was stretched once for the -9 (nothing much for the -3 just winglets).

So when stretching the 787 to a -10 would the wings need to be changed or would the current wings be sufficient? It seems that if they stretched it for a -10 and were forced to redesign the wings then they might as well look at developing a -11 model to become the new 777s, (only if they have to change the wings for a -10 model)

So can it be done?

30 replies: All unread, showing first 25:
 
User currently offlineDeltaL1011man From United States of America, joined Sep 2005, 9700 posts, RR: 14
Reply 1, posted (7 years 2 months 2 weeks 2 days 17 hours ago) and read 2838 times:

Quoting DL767captain (Thread starter):
Does anyone know what size the 767 was designed for? (as in the -200 or the -300)
When looking at the 767, if the plane was designed to be the size of the 767-200 the plane was then stretched to the -300 and finally the -400. So if the wings and everything were designed for the 762, then stretching it twice worked.

I'm pretty sure the 764 has more of a 777 wing and gear but i might be wrong?



yep.
User currently offlineWingedMigrator From United States of America, joined Oct 2005, 2259 posts, RR: 56
Reply 2, posted (7 years 2 months 2 weeks 2 days 17 hours ago) and read 2838 times:

Quoting DL767captain (Thread starter):
So can it be done?

Yes. Otherwise Boeing wouldn't talk about the 787-10 as a matter of "when", not "if".

Quoting DL767captain (Thread starter):
So when stretching the 787 to a -10 would the wings need to be changed or would the current wings be sufficient?

That all depends on the desired payload and range demanded by airline customers, which drive the required maximum takeoff weight. The existing wings and landing gear are limited to carrying roughly 550,000 lb. Above that, field performance, initial cruise altitude, and landing gear pavement loading become unacceptable. There is a fork in the road: keep the takeoff weight under 550,000 lb and suffer the limited performance, or design a new wing and landing gear to break decisively into 777 territory.

Boeing's choice is an important move in the game of chess being played against the Airbus product strategy.


User currently offlineDL767captain From United States of America, joined Mar 2007, 2539 posts, RR: 0
Reply 3, posted (7 years 2 months 2 weeks 2 days 13 hours ago) and read 2838 times:

Quoting WingedMigrator (Reply 2):

that makes sense, it seems to me that if Boeing wants to quickly compete with the A350 they have to do a quick 777 refresh or rush a redesign on the new 787 wing to make an A350 competitor, but how expensive is it to make a new wing


User currently offlineHa763 From United States of America, joined Jan 2003, 3671 posts, RR: 5
Reply 4, posted (7 years 2 months 2 weeks 2 days 13 hours ago) and read 2838 times:
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Quoting DeltaL1011man (Reply 1):
I'm pretty sure the 764 has more of a 777 wing and gear but i might be wrong?

The 767-400 has the same wing as the -200/-300. The increased span comes from the raked wingtips, which are 7 ft 8 in (2.34 m) long and increased wing span by 14 ft 3 in (4.35 m). For the landing gear, only the wheels, tires, and brakes on the main gear are the same as the 777.


User currently offlineJAAlbert From United States of America, joined Jan 2006, 1624 posts, RR: 1
Reply 5, posted (7 years 2 months 2 weeks 2 days 13 hours ago) and read 2838 times:

Quoting DL767captain (Thread starter):
There has been a lot of talk about the 787 being stretched to a -10 and even a -11, but is this possible?

Not if Boeing doesn't find a big stash of fasteners!


User currently offlineAstuteman From United Kingdom, joined Jan 2005, 10239 posts, RR: 97
Reply 6, posted (7 years 2 months 2 weeks 2 days 13 hours ago) and read 2838 times:
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Quoting WingedMigrator (Reply 2):
The existing wings and landing gear are limited to carrying roughly 550,000 lb. Above that, field performance, initial cruise altitude, and landing gear pavement loading become unacceptable. There is a fork in the road: keep the takeoff weight under 550,000 lb and suffer the limited performance, or design a new wing and landing gear to break decisively into 777 territory.

A suitable engine wouldn't go amiss, either........  Smile

Regards


User currently onlineStitch From United States of America, joined Jul 2005, 31417 posts, RR: 85
Reply 7, posted (7 years 2 months 2 weeks 2 days 7 hours ago) and read 2838 times:
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Quoting DL767captain (Thread starter):
There has been a lot of talk about the 787 being stretched to a -10 and even a -11, but is this possible?

Absolutely. Factoring in the 787's wider fuselage diameter and CFRP construction techniques, a 69m 787-10. 75m 787-11 and even 80m 787-12 are all quite doable without the structural inefficiencies that affected the A340-600.

Quoting DL767captain (Thread starter):
So when stretching the 787 to a -10 would the wings need to be changed or would the current wings be sufficient?

The current wings can support almost 100,000lbs more weight then the undercarriage (640,000lbs vs. 560,000lbs). However, their efficiency at that MTOW would be compromised a bit compared to how they are now at a 540,000lb MTOW, which is why many of us advocate a new wing for a 787HGW.

Quoting DL767captain (Thread starter):
It seems that if they stretched it for a -10 and were forced to redesign the wings then they might as well look at developing a -11 model to become the new 777s, (only if they have to change the wings for a -10 model)

I envision an entire family of 787HGWs, including ER and LR models as well as an eventual freighter.

Quoting DL767captain (Thread starter):
So can it be done?

Most certainly.


User currently offlineCarls From United States of America, joined Aug 2007, 522 posts, RR: 0
Reply 8, posted (7 years 2 months 2 weeks 2 days 7 hours ago) and read 2838 times:

Quoting JAAlbert (Reply 5):
Not if Boeing doesn't find a big stash of fasteners!

 thumbsup 

Quoting Stitch (Reply 7):
Absolutely. Factoring in the 787's wider fuselage diameter and CFRP construction techniques, a 69m 787-10. 75m 787-11 and even 80m 787-12 are all quite doable without the structural inefficiencies that affected the A340-600.

For those who don't know the 787 program that well can you explain us based in what information (any link, or numbers or something that you can share with us) can you state that the 787 because the CFRP construction techniques can be stretched three more times.

I would like to know what structural inefficiencies affected the A340-600, I wasn't aware of it. Other than the first up to the number 6 were with fuel inefficiencies. But I never heard about any structural inefficiencies.

Thank you in advance.


User currently onlineStitch From United States of America, joined Jul 2005, 31417 posts, RR: 85
Reply 9, posted (7 years 2 months 2 weeks 2 days 6 hours ago) and read 2838 times:
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Quoting Carls (Reply 8):
I would like to know what structural inefficiencies affected the A340-600, I wasn't aware of it. Other than the first up to the number 6 were with fuel inefficiencies. But I never heard about any structural inefficiencies.

Because of her length, the A340-600 required not-insignificant structural reinforcement to the fuselage, which resulted in a not-insignificant rise in her MEW which impacts her overall performance and efficiency.

The only reason I bring it up is because the first question folks ask about a 787 stretch is "will it suffer from the same phenomena that affects the A340-600?", so I was just heading off that question. Again, it wasn't a slap at the A340-600 for the sake of taking a slap at the A340-600.

Quoting Carls (Reply 8):
For those who don't know the 787 program that well can you explain us based in what information (any link, or numbers or something that you can share with us) can you state that the 787 because the CFRP construction techniques can be stretched three more times.

The greater fuselage diameter of the 787 will naturally support a longer stretch. Also, the greater strength of the CFRP being used to build the 787's fuselage (vis-a-vis aircraft Al) requires less material to provide the necessary structural reinforcement to support such a stretch and the material itself is lighter, both contributing to a lower "MEW creep" versus aircraft Al.


User currently offlineSEPilot From United States of America, joined Dec 2006, 7140 posts, RR: 46
Reply 10, posted (7 years 2 months 2 weeks 2 days 5 hours ago) and read 2838 times:

Whether or not Boeing goes with a HGW version of the 787 will depend on whether or not they decide to go for Y3 for a 777-747 replacement. I believe that is their long-term plan, and so I do not expect them to raise the MTOW of the 787. They have announced that they will build the 787-10, but my expectation that it will have the same wing and landing gear as the rest, and will thus have shorter range. Y3 will then start at a slightly larger size, but with very long range, and go up to 400-450 seats. My  twocents 


The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineCarls From United States of America, joined Aug 2007, 522 posts, RR: 0
Reply 11, posted (7 years 2 months 2 weeks 2 days 5 hours ago) and read 2838 times:

Quoting Stitch (Reply 9):
Because of her length, the A340-600 required not-insignificant structural reinforcement to the fuselage, which resulted in a not-insignificant rise in her MEW which impacts her overall performance and efficiency.

The only reason I bring it up is because the first question folks ask about a 787 stretch is "will it suffer from the same phenomena that affects the A340-600?", so I was just heading off that question. Again, it wasn't a slap at the A340-600 for the sake of taking a slap at the A340-600.

Thank you, I asked you because I heard about it before but I did not know what really happened.

Quoting Stitch (Reply 9):
The greater fuselage diameter of the 787 will naturally support a longer stretch. Also, the greater strength of the CFRP being used to build the 787's fuselage (vis-a-vis aircraft Al) requires less material to provide the necessary structural reinforcement to support such a stretch and the material itself is lighter, both contributing to a lower "MEW creep" versus aircraft Al.

Do you have any link were I can look for more information. Thank you.


User currently onlineStitch From United States of America, joined Jul 2005, 31417 posts, RR: 85
Reply 12, posted (7 years 2 months 2 weeks 2 days 4 hours ago) and read 2838 times:
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Quoting Carls (Reply 11):
Do you have any link were I can look for more information. Thank you.

Alas, I do not. My knowledge (such as it is) about it is an amalgamation of scores of articles and discussions here and elsewhere with aerospace engineers (including A340 and 787 engineers). It has been discussed in greater depth both in this forum (CivAv) and the TechOps forum, so a search might return some hits that explain the specifics about it in greater depth.


User currently offlinePizzaandplanes From , joined Dec 1969, posts, RR:
Reply 13, posted (7 years 2 months 2 weeks 1 day 23 hours ago) and read 2838 times:

Some planes just don't stretch well...

User currently offlineDeltaL1011man From United States of America, joined Sep 2005, 9700 posts, RR: 14
Reply 14, posted (7 years 2 months 2 weeks 1 day 23 hours ago) and read 2838 times:

Quoting Ha763 (Reply 4):
The 767-400 has the same wing as the -200/-300. The increased span comes from the raked wingtips, which are 7 ft 8 in (2.34 m) long and increased wing span by 14 ft 3 in (4.35 m). For the landing gear, only the wheels, tires, and brakes on the main gear are the same as the 777.

i was close thanks for the info!



yep.
User currently onlineFRNT787 From United States of America, joined Sep 2007, 1329 posts, RR: 15
Reply 15, posted (7 years 2 months 2 weeks 1 day 22 hours ago) and read 2838 times:

Quoting Stitch (Reply 7):
envision an entire family of 787HGWs, including ER and LR models as well as an eventual freighter.

 checkmark 

Quoting SEPilot (Reply 10):
Whether or not Boeing goes with a HGW version of the 787 will depend on whether or not they decide to go for Y3 for a 777-747 replacement.

IMO, Boeing will forego the orignal plan for a Y3 for many years, as the 787 will grow and cover a much larger market than originally planned, due to the A350's new size (i.e. one that competes with the 787/777 combo on most fronts, except 787-8,3). It is possible that Boeing will mainly market the 747-8 in the market between the 777 and A-380. So Y3 will actually depend, again in my opinion, on what becomes of the 787 family in the coming years.



"We have a right to fail, because failure makes us grow" --Glenn Beck
User currently offlineWingedMigrator From United States of America, joined Oct 2005, 2259 posts, RR: 56
Reply 16, posted (7 years 2 months 2 weeks 1 day 15 hours ago) and read 2807 times:

Quoting Astuteman (Reply 6):
A suitable engine wouldn't go amiss, either

 checkmark  thank you sir. The GEnx can't grow much, as has been amply discussed in connection with the A350 XWB.

Quoting Stitch (Reply 7):
The current wings can support almost 100,000lbs more weight then the undercarriage (640,000lbs vs. 560,000lbs).

I don't know where this number came from, but it does stretch the limits of what has been done before. At 640 klbs the wing would be ~10% more loaded than the heaviest 777s. That can't be very good for field performance.

Quoting Carls (Reply 8):
I would like to know what structural inefficiencies affected the A340-600, I wasn't aware of it.

At spec empty weight, the A346 weighs 562 kg/m2 of cabin. The 77W weighs 505 kg/m2 of cabin. That's 11% worse than its direct competitor.

Quoting FRNT787 (Reply 15):
So Y3 will actually depend, again in my opinion, on what becomes of the 787 family in the coming years.

One could equally claim the opposite: what becomes of the 787 family in the coming years depends on the Y3 strategy. That's what makes this decision so much more interesting than a routine stretch.


User currently offlineRIX From United States of America, joined Aug 2000, 1787 posts, RR: 1
Reply 17, posted (7 years 2 months 2 weeks 1 day 15 hours ago) and read 2807 times:

Quoting FRNT787 (Reply 15):
Y3 will actually depend, again in my opinion, on what becomes of the 787 family in the coming years.

- yep, and of 787/787HGW addressing 767-777 seat range and Y3 addressing that of 777-747, the former looks much more probable as 777 market should be addressed today. A350 doesn't allow Boeing to wait until it's ready for all-new design. Plus, 400+ seaters sales are just poor. It may change in not so distant future, but ~350 seat range must be addressed now.


User currently offlineAirbusted From Australia, joined Sep 2007, 13 posts, RR: 0
Reply 18, posted (7 years 2 months 2 weeks 1 day 15 hours ago) and read 2807 times:

is the wing loading a constant in the effectiveness of the stretch as opposed the field performance? Would a wing of the same area but achieving greater lift allow a bigger stretch without increasing the size and thus weight and drag of the wing?

User currently offlineDL767captain From United States of America, joined Mar 2007, 2539 posts, RR: 0
Reply 19, posted (7 years 2 months 2 weeks 1 day 13 hours ago) and read 2807 times:

what would the economics be of using composite panels on the 777 as a quick solution?

User currently onlineStitch From United States of America, joined Jul 2005, 31417 posts, RR: 85
Reply 20, posted (7 years 2 months 2 weeks 1 day 6 hours ago) and read 2547 times:
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Quoting DL767captain (Reply 19):
what would the economics be of using composite panels on the 777 as a quick solution?

Lower MEW, which would improve fuel burn at current payloads or allow airlines to carry larger payloads for equivalent fuel burns as to today.


User currently offlineSEPilot From United States of America, joined Dec 2006, 7140 posts, RR: 46
Reply 21, posted (7 years 2 months 2 weeks 1 day 5 hours ago) and read 2547 times:

Quoting DL767captain (Reply 19):
what would the economics be of using composite panels on the 777 as a quick solution?

It's not that simple. Just substituting CFRP for the same parts made of aluminum would not yield anywhere near the weight savings as redesigning it with CFRP construction. You'd also have all the problems of mating aluminum and CFRP, unless you made the frame CFRP as well. By the time you're done you might as well start over with a full CFRP fuselage, at which point you might as well make a new plane.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently onlineStitch From United States of America, joined Jul 2005, 31417 posts, RR: 85
Reply 22, posted (7 years 2 months 2 weeks 1 day 3 hours ago) and read 2547 times:
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Quoting SEPilot (Reply 21):
Just substituting CFRP for the same parts made of aluminum would not yield anywhere near the weight savings as redesigning it with CFRP construction.

But it evidently does help, based on what Airbus is expecting for the A350.


User currently offlineSEPilot From United States of America, joined Dec 2006, 7140 posts, RR: 46
Reply 23, posted (7 years 2 months 2 weeks 1 day 3 hours ago) and read 2547 times:

Quoting Stitch (Reply 22):
But it evidently does help, based on what Airbus is expecting for the A350.

Well, the A350 is a whole new plane. They tried to "spruce up" the A330 and got laughed off the block. I suspect Boeing would encounter the same reaction if they tried to do the same with the 777. After all, the A330 and 777 are similar technology planes of almost the same age; the A330 excels at short to medium routes and the 777 is the best long range airliner currently in service, so I don't see how Boeing will be any more successful at trying to upgrade without starting over than Airbus was.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineRIX From United States of America, joined Aug 2000, 1787 posts, RR: 1
Reply 24, posted (7 years 2 months 2 weeks 1 day 2 hours ago) and read 2547 times:

Quoting SEPilot (Reply 23):
I don't see how Boeing will be any more successful at trying to upgrade without starting over than Airbus was

- hardly "any more" successful, indeed, just to keep the line running, staying attractive for existing 777 customers for incremental fleet renewals and to improve 787/777 combo competitiveness. May be quite a winner in quite a few situations. But I'm yet to get an answer on a question asked couple of times in other threads: which upgrade of 777 would worth the resources to be invested there rather than to 787HGW?


25 Stitch : Likely none by Boeing. However, with the Japanese heavies building the 787 doing the same on the 777, one wonders if they might find financing any up
26 JoeCanuck : Higher wing loading has a, (I believe), greater negative effect on low speed performance than high speed performance. Higher wing loading will result
27 Airbusted : There is another couple of aspects to stretching the aircraft and increasing range i would imagine. firstly engines not only in efficiency in terms of
28 Astuteman : Correct. It will have a drag benefit in respect of wetted area, certainly. The difficulties that arise if the wing doesn't grow are (IMO) Firstly it
29 JoeCanuck : If the wing is structurally capable of lifting the necessary higher gross weights, then I'm sure it's strong enough, (or can be fairly simple made to
30 Tdscanuck : The limiting factor for stress in an Al fuselage is damage tolerance (fatigue). Fatigue performance is fanstastically sensitive to stress...increase
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