Joni
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B787 Getting More Overweight?

Wed Jul 12, 2006 5:03 pm

It may be that the 787 weight issues are getting worse, despite Boeing's efforts to control them.

Here's an article from Sept 2005, where they say the plane was about 2% over the design weight (and that this is already more overweight than 767 or 777 were at a similar point in the program)

http://seattletimes.nwsource.com/htm...gy/2002486350_787globalside11.html

And here's a fresh source, attributing the weight to the metal mesh Boeing is inserting in the fuselage structure and putting the figure at 2,5%:

http://seattlepi.nwsource.com/business/277220_air12.html
 
darrenthe747
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 5:09 pm

well as we all know Boeing is well known for underestimating their final production model specs so they have some breathing room. It's really to soon to tell what exactly is going to be a problem until the jet takes more shape.
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WINGS
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 5:15 pm

Quoting Darrenthe747 (Reply 1):
well as we all know Boeing is well known for underestimating their final production model specs so they have some breathing room

This would be the case for a traditional metal fuselage. Now that Boeing are going down the path of a full composite fuselage many uncertainties are still unknown.

I'm confident that Boeing will manage to achieve it's targets by other means.

Regards,
Wings
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Ruscoe
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 7:46 pm

I suppose you gentlemen noted the date of the article.?

Ruscoe
 
AeroWesty
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 7:51 pm

Quoting Ruscoe (Reply 3):
I suppose you gentlemen noted the date of the article.?

Wednesday, July 12, 2006
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Beaucaire
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 7:52 pm

"Wednesday, July 12, 2006

Aerospace Notebook: Lightning a weighty issue for the 787"

Thats' the one with 2,5% overweight...
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Ruscoe
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 8:00 pm

"but the plane will be within the weight promised to airline customers."

This makes it a non issue. Boeing set very severe internal weight goals to cover such contingencies.

Ruscoe
 
Joni
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 8:11 pm

Quoting Ruscoe (Reply 6):
"but the plane will be within the weight promised to airline customers."

This makes it a non issue. Boeing set very severe internal weight goals to cover such contingencies.

Boeing has, apparently wisely, not promised the airlines everything. So the plane may be able to fulfill what was promised to airlines even if it won't be able to do everything now quoted on the Boeing website.

Also performance differences to the present A350 will be significantly changed in the Airbus' favour if the A350 comes in at target weight and the B787 2,5% over.
 
Flying-Tiger
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 8:12 pm

Quoting Ruscoe (Reply 6):
"but the plane will be within the weight promised to airline customers."

This makes it a non issue. Boeing set very severe internal weight goals to cover such contingencies.

Ruscoe

Airbus told airline customers "that the A380 will be delivered in time"... Never take for granted what OEMs - regardless if Airbus or Boeing - are telling you officially. And: goals can be achieved - or they can be missed, no matter how severe they are.
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distanthorizon
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 8:12 pm

"Boeing said it is not sure it will be able to meet the target weight of the 787, but the plane will be within the weight promised to airline customers."

What other thing could they say?

"We always planned to deal with this issue, but we did not anticipate the complexity," acknowledged Boeing's Scott Strode, head of 787 development and production.

So did they antecipated the weight problem conected?

I really hope Boeing can find a way of dealing with the many problems that are still to appear (most of them completly new ones), but they will have serious dificulties with this one: most of the plane in not made by Boeing.
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LS737
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 8:18 pm

Quoting WINGS (Reply 2):
Now that Boeing are going down the path of a full composite fuselage many uncertainties are still unknown.

"Many uncertainties are still unknown". Have you been taking lessons from Donald Rumsfeld? Big grin
 
manni
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 8:35 pm

2,5% what would that be in KG for the 787-8? Boeings best selling 787 so far IIRC.
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zeke
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 8:44 pm

Dont know what all the fuss is about, when they deliver the aircraft, it will be the best they could have achieved at the time. No doubt with time later production aircraft may well be lighter still.

Speculating about a percent or two when we dont know all the baseline parameters is pointless.
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keesje
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 9:27 pm

Quoting Zeke (Reply 14):
Speculating about a percent or two when we dont know all the baseline parameters is pointless.

Where have you been during the last few years..

Quoting Darrenthe747 (Reply 1):
well as we all know Boeing is well known for underestimating their final production model specs

please speak for yourself, IMO this is an un-eraseable A.net legend

The lightning issue was mentioned months ago but quickly dismissed by folks here as bashing and as quickly forgotten.
http://www.airliners.net/discussions...general_aviation/read.main/2640551
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par13del
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 9:58 pm

Keesje
"The lightning issue was mentioned months ago but quickly dismissed by folks here as bashing and as quickly forgotten."

Is this the result of:
A. Pro Boeing slant on this web site

B. Aircraft not yet assembled

??????????
 
boeingbus
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 10:09 pm

Quoting Keesje (Reply 15):
The lightning issue was mentioned months ago but quickly dismissed by folks here as bashing and as quickly forgotten.

It's still a nonissue.... It's a nonissue because the plane is still in its design stage and quickly moving into production and test phase. This is nothing Boeing can't handle. Period!

Why do people blow things out of proportion. Boeing has a target, they missed it by 2.5. The total weight with the 2.5% still meets customers expectations. This just demonstrates that Boeing is doing the right thing to always set the benchmark high and strive to make it the best.

So tell me where is the problem? Many of you need to get a life and stop finding issues when there are non. Non yet, at least.
Airbus or Boeing - it's all good to me!
 
cloudyapple
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 10:17 pm

How long before it's officially declared as obese?  Wink
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atmx2000
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 10:19 pm

Quoting Joni (Reply 7):

Also performance differences to the present A350 will be significantly changed in the Airbus' favour if the A350 comes in at target weight and the B787 2,5% over.

Not really, the weight difference between the two is so large to begin with.

That's why Boeing only had to give looser guarantees to its customers.

Quoting Keesje (Reply 15):

The lightning issue was mentioned months ago but quickly dismissed by folks here as bashing and as quickly forgotten.

Let's not forget the A350's composite wings will have the same issue.
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keesje
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 10:23 pm

Quoting BoeingBus (Reply 17):
This is nothing Boeing can't handle. Period!

Why do people blow things out of proportion. Boeing has a target, they missed it by 2.5.

I think we have to evaluate this issue from all angles, quote every airline exec / annalist that says / thinks something about it, put the 2.5% line at the end of each 787 article, draw far reaching conclusions and bring it up many times over again for months to come.

Broken promises, angry airline customers, doom scenarios.

And do the same process over again for every (possible / likely) delay.

 Smile Nah.. Jooking

Can't wait to see the first real 787!
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NYC777
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 10:46 pm

While this might be a wet dream for all the Boeing haters out there, IMO, Boeing will probably come in at or slightly above weight (>1%).
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PolymerPlane
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 10:52 pm

Quoting Joni (Reply 7):
Boeing has, apparently wisely, not promised the airlines everything. So the plane may be able to fulfill what was promised to airlines even if it won't be able to do everything now quoted on the Boeing website.

I did not know that the airlines are that stupid to sign billion dollars contract without knowing what they are going to get  Yeah sure. Do you have anything to back up this statement? If not then it is only your opinion and means nothing.

Not the doubt the Seattle PI article, but there is a very vague description to when was the 2.5% number released. If you compare the wordings of the Seattle PI article to the previous Seattle times article, the timing of the Information is much more clearer on the earlier article. In my opinion, the writer just take whatever number they get from earlier statements and put it into perspective to support his story.

BTW the overweight estimation will be with respect to the OEW. In the first article, the aircraft was said to be ~5000 lbs overweight, which is about 2% of the OEW. This is 1% overweight by Airbus's accounting method  Wink

Cheers,
PP
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khobar
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 10:57 pm

Quoting Joni (Reply 7):
Also performance differences to the present A350 will be significantly changed in the Airbus' favour if the A350 comes in at target weight and the B787 2,5% over.

The performance promises made to the airlines have added weight taken into account. Thus even if the 787 turns out to be over its target design weight, the airlines will still get the performance they were promised. So no advantage to Airbus at all.
 
Joni
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 11:28 pm

Quoting PolymerPlane (Reply 22):
I did not know that the airlines are that stupid to sign billion dollars contract without knowing what they are going to get Yeah sure. Do you have anything to back up this statement? If not then it is only your opinion and means nothing.

Um, please read reply 7 again. I specifically said that Boeing has promises to the airlines and looks to be able (according to B) to fulfil them. Those promises are looser than the ones on B's website, which apparently depend on the plane making the design weight.

Quoting Khobar (Reply 23):

The performance promises made to the airlines have added weight taken into account. Thus even if the 787 turns out to be over its target design weight, the airlines will still get the performance they were promised. So no advantage to Airbus at all.

The airlines will get the performance they were promised, but the performance they get will be worse than what it would be if the plane made the design weight. Thus if the B787 winds up 2,5% overweight, it's definitely an advantage to Airbus compared to the situation where it was 0% overweight.
 
airfrnt
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 11:29 pm

Quoting Joni (Thread starter):
And here's a fresh source, attributing the weight to the metal mesh Boeing is inserting in the fuselage structure and putting the figure at 2,5%:

Spin.

From the same artcle:

Quote:

Boeing said it is not sure it will be able to meet the target weight of the 787, but the plane will be within the weight promised to airline customers.

It is interesting that Boeing has to do this work on lightning proofing the plane.

Quoting Joni (Reply 7):
Boeing has, apparently wisely, not promised the airlines everything. So the plane may be able to fulfill what was promised to airlines even if it won't be able to do everything now quoted on the Boeing website.

What promises are you accusing Boeing of breaking? Can you be explicit?

I think that Boeing will eventually pull this plane back to target weight. Remember that a huge chunk of the last of theA380's major weight problems was solved by reducing the weight of seats and internal furnishings.
 
lawgman
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RE: B787 Getting More Overweight?

Wed Jul 12, 2006 11:31 pm

Quoting Joni (Thread starter):
And here's a fresh source, attributing the weight to the metal mesh Boeing is inserting in the fuselage structure and putting the figure at 2,5%:

http://seattlepi.nwsource.com/busine....html

As a passenger and not an airline exec (and as someone who was stuck on a roller-coaster of a ride on AC from YYZ to FLL 3 years ago), I found the anti-turbulence system talked about in this article to be much more interesting.
 
baroque
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 12:20 am

Quoting LS737 (Reply 10):
"Many uncertainties are still unknown". Have you been taking lessons from Donald Rumsfeld?

I dont think you can bring Rummie into this LS737 unless we are talking about the 787 lite - the one that has an OEW of about 56 t (joke!).

If the even half the extra weight was due to problems with lightning that suggests an awful lot of metal has to be added. What does Airbus do (or is it going to do) with its composite wing designs, presumably they would have the same issues?

I was in a QF 747 that was struck by lightning while parked at Changi and that blew a whole bunch of circuits and it took some hours to fix - mind you that flight had nearly everything go wrong with it, blown tyre at Athens, failed thrust reversers at Bangkok and Singapore.

Is the current experience with strikes on planes that have some composites relevant? Or is the charging too localized to be of concern where composites are a small portion of the structure?
 
ckfred
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 1:08 am

I remember watching a documentary on the building of the 777. UA had a clause in its contract about weight, so the 777 was put on a scale. It was about 100 pounds under the maximum empty weight permitted under UA's contract.

I'm not worried about Boeing having a plane that exceeds any contractually-promised maximums.
 
khobar
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 1:42 am

Quoting Joni (Reply 22):
The airlines will get the performance they were promised, but the performance they get will be worse than what it would be if the plane made the design weight. Thus if the B787 winds up 2,5% overweight, it's definitely an advantage to Airbus compared to the situation where it was 0% overweight.

Sorry, but no. The performance of the 787 isn't based on its design target weight, so the performance of the 787 will not be hindered in any way. The airlines will get exactly what they were told. Actually it will likely be a little better than what they were told based on the size of the weight safety margin Boeing chose.

The performance of the A350, on the other hand, is based on design target weight, so if it comes in at design target weight then it will simply meet its performance promised based on that one parameter.
 
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Stitch
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 1:59 am

Quoting Joni (Reply 7):
Also performance differences to the present A350 will be significantly changed in the Airbus' favour if the A350 comes in at target weight and the B787 2,5% over.

Not if the A350 is sized like a 777.  Smile

Quoting BoeingBus (Reply 15):
Boeing has a target, they missed it by 2.5. The total weight with the 2.5% still meets customers expectations.

Boeing has not "missed" anything, since the final weight is not known. They are currently 2.5% over what they want the final weight to be, and by their own admission they may not be able to eliminate that amount of weight - either in the structure that is contributing to the weight (the lightning-dissipation system) or in other structures.

So the final 787 specification is completed and Test Article 1 is built and "rolled over to the scales", it's all speculation - even from Boeing's 787 engineering teams themselves. Remember that the A380's weight expansion during design and development was rumored to be worse then it actually ended up being once the plane was finally built.

Quoting Joni (Reply 22):
The airlines will get the performance they were promised, but the performance they get will be worse than what it would be if the plane made the design weight. Thus if the B787 winds up 2.5% overweight, it's definitely an advantage to Airbus compared to the situation where it was 0% overweight.

Yes it is, but those airlines ordered the plane based on the performance they were promised. Any additional performance Boeing may be able to extract prior to delivery would be a bonus, but the airlines were not going "Hmm... Boeing says X and Airbus says X-2%. But we know Boeing 'underpromises and overdelivers' so Boeing will assuredly end up X-3% so let's order the Boeing product."

And as with other Boeing projects (like the 77W), Boeing may very well be able to improve on those guarantees later in the program. So even if the 787 "only" meets the performance specs they are contractually agreed to, that does not mean those specs are all that will ever be.
 
airfrnt
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 2:07 am

Quoting Khobar (Reply 27):
Sorry, but no. The performance of the 787 isn't based on its design target weight, so the performance of the 787 will not be hindered in any way. The airlines will get exactly what they were told. Actually it will likely be a little better than what they were told based on the size of the weight safety margin Boeing chose.

The performance of the A350, on the other hand, is based on design target weight, so if it comes in at design target weight then it will simply meet its performance promised based on that one parameter.

Do you have sources for these statements? Performance of aircraft almost always is affected first and foremost by it's weight. If your arguement is that the 787 is shy of it's weight restrictions under contract, the point is still that it's performance is not as good as it can be.
 
eatmybologna
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 2:10 am

Quoting Joni (Thread starter):
B787 Getting More Overweight?

I told B787 to stay away from McDonalds and to start exercising. Sheesh!  Yeah sure

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Ken777
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 2:11 am

It would be interesting to know how much room Boeing has between their internal target weight and the assured max weight they gave the airlines. If they are 2.5% above the internal target how much more room do they have to stay within the airlines guidelines?

As to comparing with the 350 - isn't the 350 basically using the same engines? The ones that are a good part of the 2.5% overweight? Won't the 350 have the same problems, eliminating any competitive benefits from a "fat" 787?

As long as Boeing can exceed customer expectations with the 787 I don't see that 2.5% as being a problem. It's just something that Boeing will work on over time, allowing for on-giong improvements in the program.
 
787engineer
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 2:20 am

Quoting Joni (Reply 7):
Also performance differences to the present A350 will be significantly changed in the Airbus' favour if the A350 comes in at target weight and the B787 2,5% over.

How do you know the performance "estimates" for the 787 weren't drawn from the performance guarantees given to the airlines? That would mean the performance difference between the present A350 and the 787 will not have changed at all. I think what you're seeing here is why Boeing has a tendency to underestimate their performance guarantees.

Quoting DistantHorizon (Reply 9):
"We always planned to deal with this issue, but we did not anticipate the complexity," acknowledged Boeing's Scott Strode, head of 787 development and production.

So did they antecipated the weight problem conected?

Weight is so important on any airline that it is factored into all possible risks. So in short, yes the weight was anticipated if they were forced to deal with the lighting issue with method A, method B, etc.

Quoting Zeke (Reply 12):
Dont know what all the fuss is about, when they deliver the aircraft, it will be the best they could have achieved at the time. No doubt with time later production aircraft may well be lighter still.

Speculating about a percent or two when we dont know all the baseline parameters is pointless

 checkmark  Planes get lighter as production ramps up. The first few planes will always be heavier. With testing and production experience the weight will fluctuate, and in most cases drop. I expect the same to happen with the A380.

Quoting Cloudyapple (Reply 16):
How long before it's officially declared as obese?

When the test airplanes are so overweight that the plane doesn't meet it's performance requirements, and Boeing doesn't have any plans to solve this on the delivered airplanes. We're still over a year away from any such declaration.

Quoting Joni (Reply 22):
Those promises are looser than the ones on B's website, which apparently depend on the plane making the design weight.

And you know this how? Have you taken the little information on Boeing's website and did the calculations to determine that the performance promises were derived from the design weight? I'm not even sure an accurate calculation can be done for performance with the information out there.

Quoting Joni (Reply 22):
The airlines will get the performance they were promised, but the performance they get will be worse than what it would be if the plane made the design weight. Thus if the B787 winds up 2,5% overweight, it's definitely an advantage to Airbus compared to the situation where it was 0% overweight.

 checkmark  yes  This is good news for Airbus, but I wouldn't consider it bad news for Boeing since they can still meet their promises.

Quoting Khobar (Reply 27):
Sorry, but no. The performance of the 787 isn't based on its design target weight, so the performance of the 787 will not be hindered in any way. The airlines will get exactly what they were told. Actually it will likely be a little better than what they were told based on the size of the weight safety margin Boeing chose.

The performance of the A350, on the other hand, is based on design target weight, so if it comes in at design target weight then it will simply meet its performance promised based on that one parameter.

Do you know the size of the safety margin Boeing chose? If so I'd love to hear it. If it's 2.5% then Boeing must be very careful about not letting the plane get any heavier, if it's 4% or so then we still have some wiggle room. BTW how do you know the performance of the A350 is based on the design target weight?
 
texfly101
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 2:25 am

Quoting Keesje (Reply 13):
The lightning issue was mentioned months ago but quickly dismissed by folks here as bashing and as quickly forgotten.

Yes, that's true. I wrote a response in a thread last year where I said that this would become a major issue and was dismissed as "this is nothing to worry about because lightning protection has been in all planes for decades and is well understood." I was writing in regards to the material properties of CFRP and the physics of a lightning strike (a localized high energy discharge that the material has to act strictly according to its electro-mechanical properties, which are very different between metal and CFRP.

Quoting AirFrnt (Reply 23):

It is interesting that Boeing has to do this work on lightning proofing the plane.

As I stated above, since the properties of CFRP are quite different from metal structures, and this being a FAA certification requirement, the actuality is an ongoing iterative process where the whole structure has to be looked at in view of where a strike happens and how that piece handles the energy load. There are zones of probable strike occurences and where the strike happens, the CFRP has to be protected from the quick rise, high energy discharge since it doesn't handle high energy electrical currents very well. The carbon fibres, not the matrix, are the discharge path and since they are very small, the energy rate and thermal rise is beyond the surrounding resin matrix ability to safely handle. The resin matrix is what keeps the carbon fibre in place to handle the structural design load. Injure that and you reduce the available stress/strain capability. So adding a metalic mesh shielding layer to transfer the electrical energy is the answer. But that adds weight. So you analyze the different areas of the airframe to see how much of this shielding is needed. For example, the wingtips, horizontal and vertical surface tips and nose are the areas of highest probability according to FAA strike zones with all the other surfaces being accorded differing strike probabilities and therefore need the highest degree of protection. Add the fact that CFRP energy load analysis algorithims are still being fine tuned and developed and its a moving target to get the structure both protected and designed with the minimum metallic mesh weight added. You can't just replace a wing or fuselage section just because it was hit, but you still have to figure out if any and how much of an area might have to be repaired to cover the damage which isn't necessarily visible.
And thats just the beginning as you have to develop detection methods, repair methods, damage analysis, etc to handle the actuality that an airplane will be hit during its lifespan. In metal it was understood by the industry and covered by standards. CFRP is a new area where all these methods are not covered by industry standards. Everything from A&P licenses to FAA certification methods will have to be developed and agreed upon by the industry over this next decade as we see airframes that are based on a majority of CFRP for structural integrity.
 
astuteman
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 2:28 am

Quoting Keesje (Reply 13):
Quoting Zeke (Reply 14):
Speculating about a percent or two when we dont know all the baseline parameters is pointless.

Where have you been during the last few years..

This was either an excellent comment, taking the moral "high road" that we all should adopt  pray , or an excellent comment completely taking the piss out of the multitude of times this has been done to the A380 in the last couple of years. Either way it's an excellent comment, Zeke.  thumbsup 

Quoting PolymerPlane (Reply 20):
I did not know that the airlines are that stupid to sign billion dollars contract without knowing what they are going to get

Me neither, but apparrently it's common practice on Airbus widebody contracts......  Smile

Quoting AirFrnt (Reply 23):
Remember that a huge chunk of the last of theA380's major weight problems was solved by reducing the weight of seats and internal furnishings.

 Smile

Quoting Khobar (Reply 27):
The performance of the 787 isn't based on its design target weight, so the performance of the 787 will not be hindered in any way



Quoting Khobar (Reply 27):
The performance of the A350, on the other hand, is based on design target weight,

The logic behind these two comments went over my head, sorry. Any chance of elucidation?  Smile

Regards
 
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Revelation
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 2:31 am

Quoting Cloudyapple (Reply 16):
How long before it's officially declared as obese?

Or nicknamed the WalrusJet?  Smile
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PolymerPlane
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 2:38 am

Quoting Texfly101 (Reply 33):

Since any plane does not have any grounding, how does CFRP plane is in worst shape than metal aircraft? I would think that since CFRP is a bad conductor, the current would not travel from the strike spot. Can anybody explain how having wire mesh will be advantageous and how does an aircraft discharge the energy from lightning strike?

Cheers,
PP
One day there will be 100% polymer plane
 
khobar
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 2:46 am

Quoting AirFrnt (Reply 29):
Do you have sources for these statements? Performance of aircraft almost always is affected first and foremost by it's weight. If your arguement is that the 787 is shy of it's weight restrictions under contract, the point is still that it's performance is not as good as it can be.

No, that wasn't the point of the original argument which was that the weight issue would be an advantage for Airbus, and that is incorrect since that 2.5% over DWT will not adversely affect performance guarantees.

That the 2.5% over DWT might mean the 787 won't perform as well as it possibly could is a separate issue and remains to be seen. After all, the A380 is also over weight by 2-2.5% but is reportedly more slippery than originally anticipated which has supposedly countered the weight penalty.

The worst one can say about the weight issue on the 787 is that the plane might not exceed its performance guarantees by as wide a margin as the numbers originally suggested.

Then again, life's full of surprises.  Wink
 
NADC10Fan
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 2:48 am

Here's the sole point amid all the wonderful AvB foolishness which sprouted here that's worth making: Not a single full 787 airframe is together and flying as yet. Therefore, any final weight issues are unknown and moot ... and will be for another year. The same goes for any issues surrounding the A350/370.

If, when it gets flying, the 787 still experiences these problems - or worse, like the A380 - then you've got some really nice hay to bail.

Until then, every bit of this is all just sound and fury signifying ... nothing.

What keeps it interesting - and would be most wonderful to see - are the serious technical discussions that leave the posturing behind. Some of that is in latter posts ... let's see more of that, why not?

[Edited 2006-07-12 19:50:12]
TANSTAAFL!
 
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 2:52 am

Quoting PolymerPlane (Reply 36):
Since any plane does not have any grounding, how does CFRP plane is in worst shape than metal aircraft? I would think that since CFRP is a bad conductor, the current would not travel from the strike spot. Can anybody explain how having wire mesh will be advantageous and how does an aircraft discharge the energy from lightning strike?

As hinted at in the 2nd article above:

Quote:
Still, the lightning will look for any path of least resistance into the composite material, such as through a wing-skin fastener.

Since there are so few metal parts, and all of the metal parts have less resistance than the composite parts, current and thus heat will be tremendous in the metal parts it does find. I have read a very interesting report of how a composite glider was hit by lightening, and the heat in the metal aileron control rods was so high that the wing just exploded (luckily both pilots had parachutes and survived). The idea of the grid is to spread out the current and thus dissipate the heat - that's what is happening on an all-metal airplane, so the same principle is being applied to the composite airplane.
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 3:00 am

The accident report for the lightning hitting the glider is here.

Follow the "figure" links inside the report to see cool pictures of what happens to a composite aircraft that is hit by lightning and does not have adequate preparation.

Lots of details about exactly what happened - boy those British can be meticulous when they want to be...
Inspiration, move me brightly! Light the song with sense and color.
Hold away despair, more than this I will not ask.
Faced with mysteries dark and vast, statements just seem vain at last.
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 3:02 am

Quoting PolymerPlane (Reply 20):
did not know that the airlines are that stupid to sign billion dollars contract without knowing what they are going to get

Check with Qatar. The signed for the A-350 and it is now in it's fourth re-design. They apparently have experience in this regard.
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khobar
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 3:19 am

Quoting Astuteman (Reply 34):
The logic behind these two comments went over my head, sorry. Any chance of elucidation?

Boeing said the 787 will do X and that's what it will do. Airbus countered that their A350 will do Y which is better than X. If Airbus is basing Y on DWT and they meet Y at DWT then no advantage. If Airbus is basing Y on DWT + fudge factor and they meet DWT, then Y is exceeded and Airbus is at an advantage because of Airbus, not Boeing.

Does that clear things up?
 
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 3:50 am

Quoting Joni (Reply 7):
Also performance differences to the present A350 will be significantly changed in the Airbus's favour if the A350 comes in at target weight and the B787 2,5% over.

I wouldn't count on the A350 coming in on target, given Airbus' experience with the A380.

After all, Airbus is famous for making heavy planes, aren't they?

Quoting Joni (Reply 22):
Um, please read reply 7 again. I specifically said that Boeing has promises to the airlines and looks to be able (according to B) to fulfil them. Those promises are looser than the ones on B's website, which apparently depend on the plane making the design weight.

How do you know this? Are you privy to what Boeing promised the airlines? Pray tell (or prattle).  sarcastic 
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kaneporta1
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 4:03 am

Quoting BoomBoom (Reply 43):
After all, Airbus is famous for making heavy planes, aren't they?

Nice spin. So we have:

A300
A310
A32x
A330
A340
A380

Apart from the A380 which is the biggest, most advanced and most complex airliner ever made, which other aircraft is "heavy"? (I assume you mean overweight)
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 4:15 am

Quoting Stitch (Reply 28):

Boeing has not "missed" anything, since the final weight is not known.

Yes they have. They missed their internal target weight, which you dont have access to. So you don't know but people that actually work at Boeing do!
However, this remains to be within the range of what they have quoted their customers, which is a good thing.
Airbus or Boeing - it's all good to me!
 
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 4:21 am

Quoting Keesje (Reply 18):
Broken promises, angry airline customers, doom scenarios.

Wow, your the last one I'd expect to speak the truth on Airbus.  Smile
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PolymerPlane
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 4:22 am

Quoting DAYflyer (Reply 41):
Check with Qatar. The signed for the A-350 and it is now in it's fourth re-design. They apparently have experience in this regard.

Well they hasn't signed anything yet, just MoU which means squat. The biggest mistake they made IMO was letting their 787 slot go.

Cheers,
PP
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texfly101
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 4:42 am

Quoting PolymerPlane (Reply 36):
Since any plane does not have any grounding, how does CFRP plane is in worst shape than metal aircraft? I would think that since CFRP is a bad conductor, the current would not travel from the strike spot. Can anybody explain how having wire mesh will be advantageous and how does an aircraft discharge the energy from lightning strike?

A lightning strike is simply the passage of electrons from the earth to the atmosphere. The plane acts as a part of the conductive path. The electrons enter the structure at its greatest point of concentration of electrical potential, hence wingtips, etc. It exits at the point of lowest potential relative to the atmosphere since electrons travel from areas of potential differences. (don't try to figure out the high/low business unless you're an EE who does this for a living...its all relative. I'm sure that I'll be corrected by a true EE but it always flows from an area of concentration of electrons to an area that has a lesser concentration) The carbon fibre in the CFRP does represent a possible path since carbon is an electrical conductor. But since the carbon fibre is both very small in diameter, which increases resistance which produces heat, and also doesn't have the electrical passage properties of Al, which also increases the resistance and adds heat, then the carbon fibre heats up quite a bit more than Al, and then the CRFP as a whole heats up since it has to dissipate the heat energy produced by the passage of the electrons. Since its not a homogeneous material like Al, the different materials heat and react at different rates and with different characteristics. Metal simply heats up a bit, expands a bit, and passes the electron flow. Since its homogeneous, it expands and heats together as a whole. Not so in the CFRP. CFRP is a non-homgeneous material composed of carbon fibres in a resin matrix. As I stated, the resin matrix does not like being heated, it degrades, which makes the CRFP not able to perform its mechanical function of handling the stress and strain of mechanical actions. The part also deforms since the carbon fibre heats and expands at a different rate than the resin matrix which breaks the bonds originally established when the CFRP was cured. So it can't be the carrier of the electrical energy of a strike as its electrical characteristics are undesireable. So something has to take its place, hence the introduction of a metal mesh carrier. Just like the shielding on a co-axial cable by a wire mesh surrounding it, the metal mesh represents a "least resistance" path for the electrical energy to follow. With the mesh, you can also plan the path that the energy takes and keep it from entering electrical control systems. This is an "electric airplane" that definitely would like its electrical systems to be secure and free from interference. So they chose the electrical mesh. Its lightweight, able to conform to complex curves, and its electrical characteristics are well understood.
 
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RE: B787 Getting More Overweight?

Thu Jul 13, 2006 4:43 am

Quoting Zeke (Reply 12):
Dont know what all the fuss is about, when they deliver the aircraft, it will be the best they could have achieved at the time. No doubt with time later production aircraft may well be lighter still.

Speculating about a percent or two when we dont know all the baseline parameters is pointless.

Yes it is.

Quoting BoeingBus (Reply 15):
It's still a nonissue.... It's a nonissue because the plane is still in its design stage and quickly moving into production and test phase. This is nothing Boeing can't handle. Period!

They could not handle corporate espionage without getting caught!  Silly

Quoting Atmx2000 (Reply 17):
Not really, the weight difference between the two is so large to begin with.

Massive would be the word.

Quoting PolymerPlane (Reply 20):
I did not know that the airlines are that stupid to sign billion dollars contract without knowing what they are going to get . Do you have anything to back up this statement? If not then it is only your opinion and means nothing.

How logic took you there is a mystery. The parameters in the contracts are clearly higher than the internal targets, which should be as agressive as possible. The contracts parameters should be as low risk as possible, hence the difference. All sevice level agreements work this way, internal and external targets.

Quoting 787engineer (Reply 32):
How do you know the performance "estimates" for the 787 weren't drawn from the performance guarantees given to the airlines?

Best question of the day.

Quoting Texfly101 (Reply 33):
I was writing in regards to the material properties of CFRP and the physics of a lightning strike (a localized high energy discharge that the material has to act strictly according to its electro-mechanical properties, which are very different between metal and CFRP.

NASA (Langley) has been researching this for years, they understand how it works with CFRP and so does Boeing.

http://oea.larc.nasa.gov/PAIS/Concept2Reality/lightning.html

Quoting Astuteman (Reply 34):
Me neither, but apparrently it's common practice on Airbus widebody contracts......

DOH!  Wow!
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