atmx2000
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787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 7:51 am

http://boeing.com/commercial/airports/acaps/787brochure.pdf

Looking at the latest airport compatibility brochure for the 787, it appears that Boeing has left out the OEW information from the data table. Looking at the payload range charts and comparing it to the Sept 2005 version it appears that max payload for both has decreased by about 4,000 lbs (~1.8t). Since the weight table indicates that maximum zero fuel weight is the same, and OEW = MZFW - max payload, it would appear the OEW has increased by 4,000 pounds. For the 787-8 that is a ~1.7% increase. It would appear that this OEW increase is leading to a drop in range of ~250-300nm at MTOW for the design passenger capacity range.

Is this the final weight or will Boeing be able to reduce weight further?
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worldxplorer
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 7:57 am

Quoting Atmx2000 (Thread starter):
Is this the final weight or will Boeing be able to reduce weight further?

Expect Boeing to continue to reduce the weight right thru testing.

WorldXplorer
 
atmx2000
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 9:52 am

Quoting WorldXplorer (Reply 1):
Expect Boeing to continue to reduce the weight right thru testing.

Actually, I just realized the OEWs can't be compared directly, as they were for configurations with different numbers of passengers, with 8Y in the old one and 9Y in the new one.

Looking at -8 cabin layout for 3 class with 9Y seating a total of 237 pax (which is less than the 242 pax quoted on the payload range chart), one can see that a few more heavier premium seats have been added in addition to more Y seats. There appears to be more galley space in economy, and an additional bathroom in first and business class. Also additional supplies will also be need for the extra passengers. All of these things will increase OEW.
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sunrisevalley
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 9:55 am

Quoting Atmx2000 (Reply 2):
All of these things will increase OEW.

Typically the OEW is for a generic aircraft and does not reflect the weight needed to make it passenger ready.
 
atmx2000
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 10:08 am

Quoting SunriseValley (Reply 3):
Typically the OEW is for a generic aircraft and does not reflect the weight needed to make it passenger ready.

The OEW corresponds to a generic configuration. Those configurations are often lighter than what an airline would put into it, but it still takes into account passenger and crew count.
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sunrisevalley
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 11:04 am

Quoting Atmx2000 (Reply 4):
but it still takes into account passenger and crew count.

The way I read your response is that the OEW includes passenger and crew count. Is this what you meant? If not perhaps you should rephrase your response.
 
atmx2000
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 11:31 am

Quoting SunriseValley (Reply 5):
The way I read your response is that the OEW includes passenger and crew count. Is this what you meant? If not perhaps you should rephrase your response.

By taking into account passenger and crew count, I meant that is was a factor in its calculation. OEW includes personnel required for full operations. It also includes fixtures, like seats, and other items that are determined by passenger capacity count.
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iwok
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 3:44 pm

Quoting Atmx2000 (Reply 2):
Looking at -8 cabin layout for 3 class with 9Y seating a total of 237 pax (which is less than the 242 pax quoted on the payload range chart), one can see that a few more heavier premium seats have been added in addition to more Y seats. There appears to be more galley space in economy, and an additional bathroom in first and business class. Also additional supplies will also be need for the extra passengers. All of these things will increase OEW.

Interesting catch.. Its amazing that you actually study these things so intensly..

So, what's you thought? Is it a -8 vs. -9 issue, or is there some other weight gain that we have not heard about yet?

I remember there was talk of the 787 being a little over weight (although similar to the 777 at the same stage of development); any update on this?

iwok
 
art
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 3:59 pm

I was just wondering: should it be easier or more difficult to trim weight from an all composite design? You don't have the option of replacing (heavier) metal panels with (lighter) composite ones as you would in a more conventional aircraft.

Any thoughts?
 
atmx2000
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 4:27 pm

Quoting Iwok (Reply 7):
Interesting catch.. Its amazing that you actually study these things so intensly..

Well, I had a vague impression that the range-payload curves had changed for the -8 (it changed for the -3 as they appear to have eliminated the extra tanks), with lower range for payload. I was also curious to see if the OEW changed, and saw the numbers were missing from the table. Then I went back to the range payload curve and realized max payload had been lowered. Then I started analyzing the graph.

Quote:
So, what's you thought? Is it a -8 vs. -9 issue, or is there some other weight gain that we have not heard about yet?

I don't see why this has anything to do with the -9. Whether the apparent increase in OEW is due to changes in cabin configuration, or whether they reflect new estimates of what 787 weight will be, or some combination I don't know.

However, if Boeing is going quote a upper and lower bound for capacity and range based on 8 abreast versus 9 abreast seating, I don't see why they shouldn't quote a range for OEW.

Quoting Iwok (Reply 7):
I remember there was talk of the 787 being a little over weight (although similar to the 777 at the same stage of development); any update on this?

iwok

Last fall the talk was something like 1 to 2 metric tons or so, which would be consistent with what I think the OEW increase is. But I have a hard time imagining they did not make further progreess in the last 6 months.
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Rheinbote
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 4:49 pm

Quoting Art (Reply 8):
I was just wondering: should it be easier or more difficult to trim weight from an all composite design? You don't have the option of replacing (heavier) metal panels with (lighter) composite ones as you would in a more conventional aircraft.

I'd assume that the 787 fuselage, being the first large scale application of composites of its kind, was designed with elevated safety margins. These will be gradually reduced once experience starts to build up from early manufacturing and operations.

Generally, it should be easier to reduce weight, because slight variations in the number and orientation of plies don't necessarily have a huge impact on tooling, and tooling requirements are reduced with composites anyway.

Likewise many components of the "more electric" system are expected to benefit form near/mid-term advances in technology, decreasing weight, bulk and cost. For example, future electric power conversion electronics might do away with liquid cooling. Even a later upgrade to all-electric systems is conceivable.

The 787 has to be considered as a moving target perhaps.
 
ikramerica
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 4:55 pm

Quoting Atmx2000 (Reply 2):
Actually, I just realized the OEWs can't be compared directly, as they were for configurations with different numbers of passengers, with 8Y in the old one and 9Y in the new one.

Yes, and the brochure still seems to be incomplete, like they revised it as much as they could for 9Y but didn't get it finished.

Quoting Iwok (Reply 7):
So, what's you thought? Is it a -8 vs. -9 issue, or is there some other weight gain that we have not heard about yet?

I think it is weight gain due to 9Y. For the -8, we are talking 27 more seats, +1 toilet and increased galley. The ranges are cut 300-500nm with 9Y seating vs. 8Y.

The brochure just no longer shows 8Y anymore...
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abba
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 5:02 pm

Quoting Art (Reply 8):
I was just wondering: should it be easier or more difficult to trim weight from an all composite design? You don't have the option of replacing (heavier) metal panels with (lighter) composite ones as you would in a more conventional aircraft.

Any thoughts?

It seems that a few issues with CFRP at the 787 has been dealt with using the AMM-principle (Add More Material) - eg. around doors and where delamination might be the most likely to take place. As better technical solutions than the AMM-principle to these issues are being developed there might be room to reduce the weight of the 787.
Abba
 
atmx2000
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 5:06 pm

Quoting Ikramerica (Reply 11):
Yes, and the brochure still seems to be incomplete, like they revised it as much as they could for 9Y but didn't get it finished.

I don't see why they don't put both in there. After all they are marketing it with a range. Many of the figures are marked 9 abreast. Of course adding 8 abreast figures will increase document size considerably.

And I do have a feeling that this was put out in a rush without a whole lot of proofreading. The same table that lacks OEW information lists the max landing weight for the 787-9 as over 1.5 million ponds (684t), more than 50% greater than the max landing weight of the A388F.  Smile

[Edited 2006-05-28 10:11:33]
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leelaw
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 5:49 pm

Quoting Iwok (Reply 7):
Interesting catch.. Its amazing that you actually study these things so intensly..



Quoting Atmx2000 (Reply 13):
And I do have a feeling that this was put out in a rush without a whole lot of proofreading.

Perhaps Randy will read this thread and have any obvious errors corrected PDQ.  Smile
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HS748
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 5:57 pm

Quoting WorldXplorer (Reply 1):
Expect Boeing to continue to reduce the weight right thru testing.

What a bold statement to make! Where is your evidence to supporty it? Oh, sorry, just realised we're talking about Boeing so of course they can have the benefit of the doubt.
 
slz396
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 6:13 pm

How easy would it to reduce the EOW weight of an entirely new plane still under development which is fully design frozen?

I mean: pretty much every screw, every joint, every part of the plane has now been designed in detail, been manufactured already and been tested individually, so I'd expect Boeing to have a very good idea of what a newly assembled 787 will weigh, hence their subtle corrections to the technical documents.

Since nothing has been flight tested yet however, I'd suppose it would be sound judgement not to fiddle around with the 787 design in an ultimate effort to reduce its weight by almost 2 tons before the complete design has been flight tested and proven its structural strenght as it was initially designed.

I thus expect to 787 to be slightly heavier than planned and have a small range penalty because of that... Nothing extremely bad about it, just proof that Boeing, its industrial partners and engineers in general are only human too.
 
leelaw
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 6:34 pm

Quoting Slz396 (Reply 16):
How easy would it to reduce the EOW weight of an entirely new plane still under development which is fully design frozen?

I mean: pretty much every screw, every joint, every part of the plane has now been designed in detail, been manufactured already and been tested individually, so I'd expect Boeing to have a very good idea of what a newly assembled 787 will weigh, hence their subtle corrections to the technical documents.

EVERETT, May 21, 2006 -- Boeing announced today that it has reached a major milestone in the design of the all-new 787 Dreamliner. The team has completed 25 percent of the releases required for the program. This means that one quarter of the pieces of information to build parts and tools for assembly have been completed and released to manufacturing organizations for fabrication or procurement.

Releases are the formal documents -- digital models in the case of the 787 program -- that allow purchases to be made, tools to be developed and parts to be built.

"We have seen tremendous progress by our international partners and the Boeing team working on the detailed design of this airplane," said Mike Bair, vice president and general manager of the 787 program. "Twenty-five percent release signifies that the largest elements - like fuselage and wing skins - are defined from the tooling requirements to the specific raw material elements."


http://www.boeing.com/news/releases/2006/q2/060521a_nr.html
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slz396
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 6:41 pm

Thanks for the quick link, Leelaw!

Quoting Leelaw (Reply 17):
The largest elements - like fuselage and wing skins - are defined from the tooling requirements to the specific raw material elements."

The way I read this, it means any serious weight reduction is no longer possible at this stage? Unless of course Boeing and its partners were to target the smaller parts only. In this respect, it would be interesting to know how much of the total weight this 25% release makes up....

[Edited 2006-05-28 11:43:31]
 
Rheinbote
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 6:58 pm

Quoting Slz396 (Reply 18):
The way I read this, it means any serious weight reduction (not talking a few pounds/kilograms, but rather tons like seems to be needed here) is no longer possible at this stage?

Do you see a need to reduce 787 weight by tons ???

If you take a close look at the structural design, it is obvious that it could be made even lighter than it already is, but mostly at the expense of manufacturability, cost and risk. Why would you want to do that unless the competition can build up pressure in terms of payload/range performance?

Whatever, any remaining potential for weight reductions, if needed, can be cashed in with -9 and -10, and then transitioned back to later versions of the -8.
 
zvezda
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 7:01 pm

Quoting Art (Reply 8):
I was just wondering: should it be easier or more difficult to trim weight from an all composite design?

I can think of factors that cut both ways. I'm not sure anyone will know the answer with certainty until the first B787 flight.

Quoting Atmx2000 (Reply 9):
I don't see why they shouldn't quote a range for OEW.

I agree. OEW should be quoted as a range. In actual service, OEW varies considerably from airline to airline.

Quoting WorldXplorer (Reply 1):

Expect Boeing to continue to reduce the weight right thru testing.



Quoting HS748 (Reply 15):
What a bold statement to make! Where is your evidence to supporty it? Oh, sorry, just realised we're talking about Boeing so of course they can have the benefit of the doubt.

Both Airbus and Boeing have reduced the weight right up through testing. I can't think of any reason why that would not continue to be the case with the B787.
 
aeronut
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 9:30 pm

Quoting Rheinbote (Reply 10):
I'd assume that the 787 fuselage, being the first large scale application of composites of its kind, was designed with elevated safety margins. These will be gradually reduced once experience starts to build up from early manufacturing and operations.

I doubt that very much. Once you certify a configuration and strength test it, I doubt you are gonna start reducing number of plys, etc... here and there.. There is a real effort to leave things alone once this point is reached.
 
aeronut
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 9:36 pm

Quoting HS748 (Reply 15):
Quoting WorldXplorer (Reply 1):
Expect Boeing to continue to reduce the weight right thru testing.

What a bold statement to make! Where is your evidence to supporty it? Oh, sorry, just realised we're talking about Boeing so of course they can have the benefit of the doubt.

Bold statement....Silly actually, I have never known strength and fatigue testing to every lead to a lighter structure in the end.
 
zvezda
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 10:13 pm

Quoting Aeronut (Reply 22):
I have never known strength and fatigue testing to every lead to a lighter structure in the end.

It happens in Japanese automobile design every day. When they find that a part is overengineered, they lighten it.
 
sunrisevalley
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 10:18 pm

Quoting Atmx2000 (Reply 6):
OEW includes personnel required for full operations. It also includes fixtures, like seats, and other items that are determined by passenger capacity count.

The OEW as published by the aircraft manufacturer does not include the items that you list. It is the weight of the aircraft before these items. For a typical 300 seater I believe you must add 20 to 24000lbs.
 
atmx2000
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 10:36 pm

Quoting SunriseValley (Reply 24):

The OEW as published by the aircraft manufacturer does not include the items that you list. It is the weight of the aircraft before these items. For a typical 300 seater I believe you must add 20 to 24000lbs.

From Boeing's 777 AC document:

Operating Empty Weight (OEW). Weight of structure, powerplant, furnishing systems, unusable fuel and other unusable propulsion agents, and other items of equipment that are considered an integral part of a particular airplane configuration. Also included are certain standard items, personnel, equipment, and supplies necessary for full operations, excluding usable fuel and payload.

From the A340NG AC document:

Operating Weight Empty (OWE) :
Weight of structure, powerplant, furnishings, systems, and other items of equipment that are an integral part of a particular aircraft configuration plus the operator's items. The operator's items are the flight and cabin crew and their baggage, unusable fuel, engine oil, emergency equipment, toilet chemical and fluids, galley structure, catering equipment, seats, documents, etc.



There is a reason why it is called OPERATING Empty Weight, and not just Empty Weight.
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DfwRevolution
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 11:56 pm

Quoting Abba (Reply 12):
It seems that a few issues with CFRP at the 787 has been dealt with using the AMM-principle (Add More Material) - eg. around doors and where delamination might be the most likely to take place.

The areas around the doors were reinforced to protect against abrasion and impact, not delamination.

Delamination occurs when moisture or contanimation penetrates the material and causes the resign and fiber to debond. This is a risk to any CFRP panel, regardless of thickness, and isn't necessarily aggrevated by scratches or dents.

Quality control in manufacturing process is the single most important factor in the safety and reliability of a CFRP component.

Quoting Zvezda (Reply 23):
I have never known strength and fatigue testing to every lead to a lighter structure in the end.

To echo Zvendza, it's also very common in civil engineering of buildings, dams, bridges, etc that removing material can strengthen the overal structure.

Quoting Rheinbote (Reply 19):
Whatever, any remaining potential for weight reductions, if needed, can be cashed in with -9 and -10, and then transitioned back to later versions of the -8.

Boeing still has a good deal of time to obtain their OEW target. They about two full years before EIS, and about 12-18 months before the remaining production-standard components must be finalized.

Also, not all of the weight problem is due to structural weight. At the last OEW update, both the GEnx and Trent 1000 were over their weight target by about 500-1,000 lbs. Suppliers have a bit more time to reach their target as the prototypes often fly with pre-production standard engines.
 
art
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RE: 787-3/8 4000 Lbs Overweight?

Sun May 28, 2006 11:57 pm

Quoting Atmx2000 (Reply 25):
The operator's items are... ...unusable fuel...

Would this include fuel to fly for 30 minutes?

I'm curious about something else. How much unusable fuel is normal? I mean, if you run the tanks dry what residual fuel is left? Just a few gallons in each tank?
 
sunrisevalley
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RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 5:37 am

Quoting Atmx2000 (Reply 25):
There is a reason why it is called OPERATING Empty Weight, and not just Empty Weight.

Atmx2000.... I do not want to appear to be argumentative but I think the difference between what is defined as OEW in the spec sheets and what is the weight of a passenger ready aircraft needs to be clear.
I will use the example of the 777-200LR. Widebodyphotog in table http://theaviationspecialist.com/777-200lr_a340-500s_dmission.gif
gives the OEW as 320000lb which in the notes he describes as "operating empty weight reflects generic aircraft configuration". This matches the Boeing
data. Where he does a mission analysis as in http://www.airliners.net/discussions...eral_aviation/read.main/2277135/6/
(reply 74) he uses a weight of 341600lbs. which in the notes he explains as "operating empty weight reflects described in-service aircraft configuration.
I think clarification is needed since the weight difference significantly impacts payload.
If WBP is monitoring this thread he may wish to comment.
 
atmx2000
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RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 6:35 am

Quoting SunriseValley (Reply 28):
Where he does a mission analysis as in http://www.airliners.net/discussions...eral_aviation/read.main/2277135/6/
(reply 74) he uses a weight of 341600lbs. which in the notes he explains as "operating empty weight reflects described in-service aircraft configuration.

He's modeling what SQ would do, including their use of heavy premium seats, including premium economy.
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aeronut
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RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 7:12 am

Quoting DfwRevolution (Reply 26):
To echo Zvendza, it's also very common in civil engineering of buildings, dams, bridges, etc that removing material can strengthen the overal structure.

You make great points, but we are talking about automotive and civil engineering industries which is different than aerospace.

The design is frozen before testing is complete. I just don't get the statement that "boeing will continue to reduce weight right through testing".
 
Picard
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RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 7:29 am

The data in that .pdf contains a few errors, fuel capcity for 787-9 is wrong as is the 787-8 wing span.
 
widebodyphotog
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RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 7:41 am

Quoting SunriseValley (Reply 28):
If WBP is monitoring this thread he may wish to comment.

I just ran into this thread and had to chuckle a bit...The new figures in the ACB leave something to desired, but the performance represents the changed configurations of the -3, -8, -9. What we are seeing here is reflective of the increased OEW relative to the old eight abreast generic spec. Nothing less, nothing more. Overall I'm a bit disappointed at the quality of the work in the brochure as it leaves a lot to be desired. Be assured that potential customers are not operating solely by this information...

I'll be very critical and say that the preliminary representations in the April 1 release are not even up to past standards for 777 and 767 and overall it's quite sloppy. Hopefully the ACB can be revised soon to the quality of information we've become accustomed to...

As far as SunriseValley and Atmx2000 back and forth goes. Atmx' has got it down correctly. I'll also say, as SunriseValley referenced a thread where I used an estimated in service config for SQ, that the current spec aircraft would lower that OEW by at least 1t...

The manufactures OEW reflects the weight of the service ready airplane in the described configuration. And furthermore Boeing and Airbus define exactly what the OEW includes, Atmx posted clear representations of this in several replies...

Interesting thread though, overall I think Atmx answered his own query through the course of it.



-widebodyphotog
If you know what's really going on then you'll know what to do
 
atmx2000
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RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 8:01 am

Quoting Widebodyphotog (Reply 32):
The manufactures OEW reflects the weight of the service ready airplane in the described configuration. And furthermore Boeing and Airbus define exactly what the OEW includes, Atmx posted clear representations of this in several replies...

Do you have numbers for the adjustments to empty weight Boeing and Airbus use to account for passenger capacity?
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leelaw
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RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 9:00 am

Weight continues to be a focal point. The 787 is about 2% above its targets, although Bair says it is 13-14% "more weight-efficient than anything that has been done before." The overage is within the margin Boeing set to meet its fuel burn promises. No specific points have been identified for weight reduction; the drive to get weight out occurs system-wide as detailed parts are configured, Bair says.

http://www.awstonline.com/avnow/news...t_story.jsp?id=news/aw052906p3.xml

Some new comments form Mr. Bair in this article which are interesting:

The uncertainty over Airbus's plans is not materially altering the competition between the 787 and A350, Bair says. Airlines aren't holding off committing to the 787 because of Airbus's indecision. Rather, the market is being driven by the bottleneck in slot availability for the 787, whose delivery positions are essentially sold out until mid-2011.
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sunrisevalley
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RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 9:09 am

Atmx2000..........
My apologies for questioning your data and Widebodyphotog, thanks for your clarification.

[Edited 2006-05-29 02:10:38]
 
abba
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RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 11:35 am

Quoting Leelaw (Reply 34):
Some new comments form Mr. Bair in this article which are interesting

This is a very very good example of a commercial statement that is approaching being nonsense as it would have been very difficult - if not outright impossible - for Bair to have said the opposite:

Quote:
Due to our competitor considering coming up with a new offer, the market has died. No one really wants to commit themselves to our product before they know if our competitor's product might be more suitable for their needs. I am sorry about this. But there is not much I can do about it.

Had he said this I would have trusted him - and expected him NOT to be allowed to say much more for a very long time to come. What he said could be true - but might also very well not be.
Abba
 
DfwRevolution
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RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 11:58 am

Quoting Aeronut (Reply 30):
You make great points, but we are talking about automotive and civil engineering industries which is different than aerospace.

The fundamental mechanics doesn't change whether we are talking a chasis, a span, or a wing rib.

Quoting Aeronut (Reply 30):
The design is frozen before testing is complete

The entire 787 has not been frozen, only about 25% is firm, and even that can be revised if absolutely necessary.

Quoting Aeronut (Reply 30):
I just don't get the statement that "boeing will continue to reduce weight right through testing".

It's rather simple. You test a component and find it is adaquetly strong. You remove material (weight) and test again. If it's still adaquetly strong, you remove more. Continue until the component is light enough with necessary safety margin in strenght
 
zvezda
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Joined: Sat Aug 28, 2004 8:48 pm

RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 2:40 pm

Quoting DfwRevolution (Reply 37):

The entire 787 has not been frozen, only about 25% is firm, and even that can be revised if absolutely necessary.

Not only can be revised if absolutely necessary but would be revised if someone found a large enough weight savings. It would be a strictly commercial decision. What is the cost of changing the design of a part after it was frozen vs. what is the cost of flying extra weight around on a few thousand airliners their their expected lifespan? If making the change would slip the delivery schedule, then making the change would be very expensive. If it wouldn't slip the delivery schedule, then it would have a good chance of going forward.
 
ikramerica
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RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 4:00 pm

Look, guys, while I'm sure the current weight is higher than the target, you have to understand that this is a brochure that is incomplete and full of errors.

It truly does look like they switched it to 9Y seating and didn't cross their i's and dot their t's.

I wouldn't read much into this document as any evidence about the ultimate 787 that will fly.

Whether the plane is overweight is a valid question, but inferring anything about a planned change in specifications from this flawed document is an exercise in speculation and futility.
Of all the things to worry about... the Wookie has no pants.
 
iwok
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RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 4:30 pm

Quoting Aeronut (Reply 30):
You make great points, but we are talking about automotive and civil engineering industries which is different than aerospace.

One of the best ways of making any structure stronger is to reduce weight. The less weight you have to support, the less sucseptible the component is to g-load failures. This is one of the reasons why high performance machines are weight reduced to the maximum. Cars, bridges, sky-scrapers etc all follow this standard principle.

Quoting Zvezda (Reply 38):
If it wouldn't slip the delivery schedule, then it would have a good chance of going forward.

Z, well said and welcome back.  thumbsup 

iwok
 
keesje
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RE: 787-3/8 4000 Lbs Overweight?

Mon May 29, 2006 5:43 pm

Quoting Atmx2000 (Thread starter):
Atmx2000



Quoting Atmx2000 (Reply 25):
Atmx2000

Sharp  thumbsup 
"Never mistake motion for action." Ernest Hemingway
 
widebodyphotog
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RE: 787-3/8 4000 Lbs Overweight?

Wed May 31, 2006 2:48 am

Quoting Atmx2000 (Reply 33):
Do you have numbers for the adjustments to empty weight Boeing and Airbus use to account for passenger capacity?

Ironically enough it looks to be 3,000lbs for the -8 nine abreast to eight abreast.




-widebodyphotog
If you know what's really going on then you'll know what to do
 
deltadc9
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RE: 787-3/8 4000 Lbs Overweight?

Wed May 31, 2006 3:12 am

Quoting HS748 (Reply 15):
What a bold statement to make! Where is your evidence to supporty it?

Not bold, business as usual. Airbus is doing the very same thing right now with the 380, or are you implying they are not too?

Quoting HS748 (Reply 15):
Oh, sorry, just realised we're talking about Boeing so of course they can have the benefit of the doubt.

And in your world the opposite is not true?

Quoting Aeronut (Reply 21):
There is a real effort to leave things alone once this point is reached.

It is called change control, and all it does is control the change with a much higher degree of analysis that before the freeze.

Quoting Zvezda (Reply 23):
When they find that a part is overengineered, they lighten it.

No reason not to.

Quoting DfwRevolution (Reply 26):
To echo Zvendza, it's also very common in civil engineering of buildings, dams, bridges, etc that removing material can strengthen the overal structure.

Some people refuse to consider the counter-intuative.

Quoting Aeronut (Reply 30):
The design is frozen before testing is complete

Change never freezes, and neither does the design in reality. Design freeze is a formal project milestone, not a commandment from on high nothing will change. All it does is set another set of processes in motion to control change, not eliminate it, which would be self defeating.
Dont take life too seriously because you will never get out of it alive - Bugs Bunny
 
atmx2000
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RE: 787-3/8 4000 Lbs Overweight?

Wed May 31, 2006 4:33 am

Quoting Widebodyphotog (Reply 42):
Ironically enough it looks to be 3,000lbs for the -8 nine abreast to eight abreast.

Can you break that down by class?
ConcordeBoy is a twin supremacist!! He supports quadicide!!
 
787engineer
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RE: 787-3/8 4000 Lbs Overweight?

Wed May 31, 2006 5:47 am

Quoting DeltaDC9 (Reply 43):
Change never freezes, and neither does the design in reality. Design freeze is a formal project milestone, not a commandment from on high nothing will change. All it does is set another set of processes in motion to control change, not eliminate it, which would be self defeating.

Absolutely correct, there are several procedures for initiating change on parts that have already been released. Just because a part has been released doesn't mean Boeing can't go back and change it. How else do we continually make minor improvements to keep planes competitive? There are even plans for "re-releases" in which large numbers of parts can be replaced by newer releases. Early on re-releases are necessary because through testing many things may need to change.

I'd like to also add that the -3 should not be considered in this "overweight" discussion. The -3 is still a long ways away, even if the -8 turns out to be overweight, it will have little affect on whether or not the -3 is also.

[Edited 2006-05-30 22:48:37]
 
hb88
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RE: 787-3/8 4000 Lbs Overweight?

Wed May 31, 2006 6:05 am

Apparently the 787 is 3-4% above weight - which shouldn't be surprising at this stage of the game.

Quoting Rheinbote (Reply 10):
Generally, it should be easier to reduce weight, because slight variations in the number and orientation of plies don't necessarily have a huge impact on tooling, and tooling requirements are reduced with composites anyway.

I'm not sure I agree. Metal structures being isotropic are more amendable to 'arbitrary' removal of material for weight saving purposes whereas composite structures are significantly more complex in terms of the loads as a function of specific ply direction, layup structure etc.

A while ago I asked a bunch of composite guys about this and most agreed that once excess weight is in a composite structure it would be more difficult and time-consuming to get out. Not impossible, just more problematic.
 
texfly101
Posts: 343
Joined: Fri Jan 06, 2006 6:42 am

RE: 787-3/8 4000 Lbs Overweight?

Wed May 31, 2006 6:08 am

Quoting Zvezda (Reply 20):
Both Airbus and Boeing have reduced the weight right up through testing. I can't think of any reason why that would not continue to be the case with the B787



Quoting Rheinbote (Reply 10):
I'd assume that the 787 fuselage, being the first large scale application of composites of its kind, was designed with elevated safety margins. These will be gradually reduced once experience starts to build up from early manufacturing and operations.

Yes, and Yes. That's the case and what will happen. The first part of the model design, until validation during testing, will have had some increased margins due to the uncertainty of how disparate assemblies actually work together, both in manufacture and assembly. The partners that actually design and build the parts usually leave some extra materials in areas like webs, fillets, etc as they are both difficult to model and design, and it gives some room when B comes calling saying "gotta reduce weight, give me 2%". Actual flight will produce another round of refinements that will reduce weight but sometimes adds weight, so I would call it at worst to be a wash, but as Zvezda states, I agree with him.
I would expect the first group of airframes, I can't say how many that encompasses, to be at best, close to the target weight. I would expect the follow on airframes of the initial model to be on target for weight and performance. The next models will benefit from the lessons learned and will meet their target weight and performance, probably exceeding it, as has typically been the case for B's models. That was the way it went for 772LR and 773ER with their actual SFB to be even better than planned.
 
atmx2000
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Joined: Wed Oct 13, 2004 4:24 pm

RE: 787-3/8 4000 Lbs Overweight?

Wed May 31, 2006 7:22 am

Quoting Hb88 (Reply 46):
Apparently the 787 is 3-4% above weight - which shouldn't be surprising at this stage of the game

Where are you getting this number from? I haven't seen anything to suggest that it is above 2%.
ConcordeBoy is a twin supremacist!! He supports quadicide!!
 
Boeing7E7
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Joined: Sat Jul 31, 2004 9:35 pm

RE: 787-3/8 4000 Lbs Overweight?

Wed May 31, 2006 4:22 pm

Quoting Atmx2000 (Thread starter):
Looking at the latest airport compatibility brochure for the 787, it appears that Boeing has left out the OEW information from the data table. Looking at the payload range charts and comparing it to the Sept 2005 version it appears that max payload for both has decreased by about 4,000 lbs (~1.8t). Since the weight table indicates that maximum zero fuel weight is the same, and OEW = MZFW - max payload, it would appear the OEW has increased by 4,000 pounds. For the 787-8 that is a ~1.7% increase. It would appear that this OEW increase is leading to a drop in range of ~250-300nm at MTOW for the design passenger capacity range.

1. Extra seats = extra weight.
2. The wing is a smidge heavier, but the aircraft has better airfield performance so something is to be said there. The -9 wing is a bit more than a smidge bigger.

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