workhorse
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80 meters wingspan limit and A380 upgrade

Tue Dec 05, 2017 3:24 pm

As we know from the multiple A380 threads, current A388 wing is sub-optimal not only because it has been made for the bigger A389 and the heavier A380F but also because it had to fit into the 80x80 meters square mandated by the airports. A thinner wing with greater span would be more efficient.

Without getting into the economics of the question (would the potential sales revenue cover the cost of the investment etc...), do you think that a folding wing solution à la B777NG could be applicable to the A380?

Is the 80 meters wingspan limit applicable to parking and taxiing only or to take-off as well? In other words, could a hypothetical A380NG park and taxi with <80m folded wings and then unfold them to, say, 90m once on the runway and take off?

And, if not, would it make sense to introduce an "in-flight unfolding" of the wings? Take off with folded wings (with the loss of lift compensated by bigger flaps, for example) and then unfold them for climb and cruise?
 
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Slug71
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Re: 80 meters wingspan limit and A380 upgrade

Tue Dec 05, 2017 5:39 pm

Heres quotes from another thread where this was recently discussed.

SomebodyInTLS wrote:
Slug71 wrote:
SomebodyInTLS wrote:
I was talking about designers and engineers, not suppliers. The A380 structure you mention is highly optimized and composites would be no improvement at all.


I was thinking more in lines of cost reduction, volume & commonality. While the frame is highly efficient, is it not slightly overweight due to the extra strengthening for the -900? Pretty sure i've read that several times. How much input would the designers and engineers have in the A380 at this point? Couldn't they too be re-purposed?



The overall shape and structure of the wing and landing gear are the type of things that have been dimensioned with the -900 in mind. But you can be sure that the *actual* wing would be considerably heavier for the -900 than the one currently used for the -800. Skin thicknesses, stringer cross-sections etc. would all change. No two stringers or skin panels are the same.


On that note (and I could be wrong), I don't think it needs a wider wingspan. Folding wingtips also add weight and complexity. It's just the shape and structure that needs optimized, and with that will come a weight reduction. Theres probably some weight and other optimizations that can be squeezed out of the fuselage too.
 
workhorse
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Re: 80 meters wingspan limit and A380 upgrade

Tue Dec 05, 2017 6:13 pm

Slug71 wrote:
On that note (and I could be wrong), I don't think it needs a wider wingspan.


Well, not being aeronautical engineer, I can't tell (but I think I read someone on a.net saying that modern wings tend to be thinner and longer and that the A80 suffered from the 80m limitation).

But still, the question is IF someone decided to make an airplane with folding wings with a span >80m when folded and <80m when unfolded, would it still be able to fly to most major airports?

I know the Mriya has an almost 90m wingspan but I am not sure it can be used as proof of feasibility because it is quite possible that its operations imply serious limitations to the operations of other aircraft (such as blocking the taxiways near the runway when it's landing or taking off).
 
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Slug71
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Re: 80 meters wingspan limit and A380 upgrade

Tue Dec 05, 2017 6:57 pm

I could be wrong on this as I have no technical knowledge on the subject either. But as I now understand, the current wingspan is only sub-optimal due to it's shape (aspect ratio and area) having being based on the -900/F. If the wing is redesigned (or was based on the -800), the wingspan would no longer have that short-coming due to the difference in shape. Of course weight comes into the equation too, and is probably the A380's biggest obstacle.

Hopefully someone with more knowledge will chime in.

As to your question (again, im not knowledgeable here), I don't see why it wouldn't be able to operate from most major airports.
 
workhorse
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Re: 80 meters wingspan limit and A380 upgrade

Tue Dec 05, 2017 9:20 pm

Slug71 wrote:
As to your question (again, im not knowledgeable here), I don't see why it wouldn't be able to operate from most major airports.


Well, I can see a situation where, for example, a taxiway parallel to the runway is too close for a 90m wingspan plane on the runway and another plane on the taxiway to pass each other. If it's like that, you'd have to close the entire taxiway during the landing/takeoff roll of the behemoth.

If we're talking about the An-225 of which there is only one flying in the whole world, it's not a big deal, but if it's a massively produced airliner, we have a problem.

But, once again, I don't know if the 80x80 limit dictated by airports to Airbus was only about gate space and taxiways or about runways as well.
 
WIederling
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Re: 80 meters wingspan limit and A380 upgrade

Tue Dec 05, 2017 10:47 pm

if you plot mtow (logscale) vs wingspan ( linear) you'll notice that all existing frames are more or less in line.

indicates that optimal wingspan vs MTOW has an exponential relationship.
Murphy is an optimist
 
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Slug71
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Re: 80 meters wingspan limit and A380 upgrade

Tue Dec 05, 2017 11:55 pm

workhorse wrote:
Slug71 wrote:
As to your question (again, im not knowledgeable here), I don't see why it wouldn't be able to operate from most major airports.


Well, I can see a situation where, for example, a taxiway parallel to the runway is too close for a 90m wingspan plane on the runway and another plane on the taxiway to pass each other. If it's like that, you'd have to close the entire taxiway during the landing/takeoff roll of the behemoth.

If we're talking about the An-225 of which there is only one flying in the whole world, it's not a big deal, but if it's a massively produced airliner, we have a problem.

But, once again, I don't know if the 80x80 limit dictated by airports to Airbus was only about gate space and taxiways or about runways as well.


I haven't been to many, but there are no major airports I can think of where a 90m wingspan would be an issue between the runway and a taxiway. Theres quite a bit of separation. But its also been a while since i've been to one and I haven't landed/taken-off on all their runways. It would never need a 90m wingspan though. If you look at the AN-225's wing compared to the A380's, the AN-225 is shaped more similar to the newer A350's. In that it is more "slender" looking, but with less rake. The A380 has more of a stubby looking wing. If you look at the wingspan and compare it to the length of the aircraft across all variants of other families, you'll see a pattern. Base models and stretches are typically longer in length than the wingspan. Shrinks typically have a wider wingspan than it's length. The A380 seems to be no exception and the ratio seems similar to that of other shrinks. The AN-225 seems rare, that it is a base model with a wider wing than its length. Even the C-5 is longer than it's wingspan. So the theory about the A380 not needing a wider wingspan, has merit. Especially with the scimitar type winglets. If anything it can be reduced.
 
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seahawk
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Re: 80 meters wingspan limit and A380 upgrade

Wed Dec 06, 2017 10:41 am

An 225 has 6 engines, which must fit on the wing.
 
WIederling
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Re: 80 meters wingspan limit and A380 upgrade

Wed Dec 06, 2017 12:21 pm

seahawk wrote:
An 225 has 6 engines, which must fit on the wing.


Someone in the know how the AN124 and AN225 wings are related?
is it just an insert in the middle? ( going to a bigger center wingbox and adding 2 engine stations )
Murphy is an optimist
 
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SomebodyInTLS
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Re: 80 meters wingspan limit and A380 upgrade

Wed Dec 06, 2017 1:10 pm

Came here since I was quoted...

So to chip in: 1) AFAIK the 80m wingspan was gate based, but 2) runway and taxiway limits would cause problems at more than 80m as well. Finally 3) even the -800 could have benefited from a wider wingspan, but my signature explains further... ;)
"As with most things related to aircraft design, it's all about the trade-offs and much more nuanced than A.net likes to make out."
 
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Slug71
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Re: 80 meters wingspan limit and A380 upgrade

Wed Dec 06, 2017 3:47 pm

SomebodyInTLS wrote:
Came here since I was quoted...

So to chip in: 1) AFAIK the 80m wingspan was gate based, but 2) runway and taxiway limits would cause problems at more than 80m as well. Finally 3) even the -800 could have benefited from a wider wingspan, but my signature explains further... ;)


Was hoping you would. :wave:

Not that it really matters since it was only a rumour. But about a year ago (before the Plus anyway), I heard a redesigned wing with blended winglets was being studied. For the most part, only the winglets ended up being true. But the "study" had an unchanged wingspan and the wings resembled that of the A330NEO's in shape. So *if* there is to be new wings, I imagine it will be based off that design. Probably all depends on how much weight can be squeezed out of the frame though.
 
LH707330
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Re: 80 meters wingspan limit and A380 upgrade

Thu Dec 07, 2017 3:42 am

Slug71 wrote:
I haven't been to many, but there are no major airports I can think of where a 90m wingspan would be an issue between the runway and a taxiway. Theres quite a bit of separation. But its also been a while since i've been to one and I haven't landed/taken-off on all their runways. It would never need a 90m wingspan though. If you look at the AN-225's wing compared to the A380's, the AN-225 is shaped more similar to the newer A350's. In that it is more "slender" looking, but with less rake. The A380 has more of a stubby looking wing. If you look at the wingspan and compare it to the length of the aircraft across all variants of other families, you'll see a pattern. Base models and stretches are typically longer in length than the wingspan. Shrinks typically have a wider wingspan than it's length. The A380 seems to be no exception and the ratio seems similar to that of other shrinks. The AN-225 seems rare, that it is a base model with a wider wing than its length. Even the C-5 is longer than it's wingspan. So the theory about the A380 not needing a wider wingspan, has merit. Especially with the scimitar type winglets. If anything it can be reduced.

SJC has limits on who's allowed to be on taxiways Z and Y when there's a 787, 777, A330, or A340 operating on 30R/12L. Source: https://www.airnav.com/airport/KSJC
WIederling wrote:
seahawk wrote:
An 225 has 6 engines, which must fit on the wing.


Someone in the know how the AN124 and AN225 wings are related?
is it just an insert in the middle? ( going to a bigger center wingbox and adding 2 engine stations )

Yes, they took the 124 wing and added an inboard section and another set of pylons. Similarly, the fuselages are related, the 225 having additional donuts.
 
RJMAZ
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Re: 80 meters wingspan limit and A380 upgrade

Thu Dec 07, 2017 5:53 am

The A380 wingspan is already greater than its fuselage length. Most aircraft have a wingspan less than the fuselage length. Span is not the problem.

The main issue is the wing is too thick. It was built to allow for a stretch to 80m. All that needs to be done is for the current wing to be made thinner. The maximum takeoff weight can then be reduced and this would allow other parts to be made lighter.

The thinner wings might only reduce the empty weight by 10T but that means you can carry 10T less fuel to travel the same distance. So a 20T reduction off the maximum takeoff weight.

The new engines can then have slightly less thrust. A higher bypass ratio at the same diameter giving a 2-3% better fuel burn. This means fuel capacity can be further reduced by another 20T. Maximum takeoff weight is now 40T less.

You've successfully improved overall CASM by 5+% without using any new technology.
 
WIederling
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Re: 80 meters wingspan limit and A380 upgrade

Thu Dec 07, 2017 9:18 am

First order a thinner wing is heavier.
Murphy is an optimist
 
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Matt6461
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Re: 80 meters wingspan limit and A380 upgrade

Thu Dec 07, 2017 10:25 am

Slug71 wrote:
But about a year ago (before the Plus anyway), I heard a redesigned wing with blended winglets was being studied.


Where did you hear about this? News report, a.net, other source? AFAIK there hasn't been any Airbus talk of a new wing.
 
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Slug71
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Re: 80 meters wingspan limit and A380 upgrade

Thu Dec 07, 2017 4:16 pm

Matt6461 wrote:
Slug71 wrote:
But about a year ago (before the Plus anyway), I heard a redesigned wing with blended winglets was being studied.


Where did you hear about this? News report, a.net, other source? AFAIK there hasn't been any Airbus talk of a new wing.


I heard it from someone who had a friend or family member that worked in Mobile. Nothing solid. Supposedly it was a rumour going around prior to the Plus. A stretch was also mentioned, but i suspect that was from the previous year when Airbus considered a moderate stretch at Paris. I think I mentioned it in the "mid-life upgrade" thread.

The rumours could also have started from this,

http://www.cnn.com/travel/article/airbu ... index.html

http://www.dw.com/en/emirates-ceo-fight ... a-18410649
 
workhorse
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Re: 80 meters wingspan limit and A380 upgrade

Thu Dec 07, 2017 5:07 pm

SomebodyInTLS wrote:
So to chip in: 1) AFAIK the 80m wingspan was gate based, but 2) runway and taxiway limits would cause problems at more than 80m as well. Finally 3) even the -800 could have benefited from a wider wingspan, but my signature explains further... ;)


LH707330 wrote:
SJC has limits on who's allowed to be on taxiways Z and Y when there's a 787, 777, A330, or A340 operating on 30R/12L.


So, what about the idea to unfold wings in flight? Put some badass flaps on the wing to be able to take off with "shorter" wingspan then once airborne retract flaps and deploy longer wings for efficient cruise.

Would that make sense from the aerodynamics point of view?
 
beenalongtime
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Re: 80 meters wingspan limit and A380 upgrade

Thu Dec 07, 2017 5:07 pm

No 'new' wing as such was discussed for Plus, but there were various aerodynamic tweaks on the table. Certainly nothing like 330 that I ever heard, that would be too radical a change. To be fair, as Mobile is an exclusively Single Aisle site, I wouldn't expect any serious A380 info to come out of there.
Regards
b
 
LH707330
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Re: 80 meters wingspan limit and A380 upgrade

Thu Dec 07, 2017 5:41 pm

workhorse wrote:
SomebodyInTLS wrote:
So to chip in: 1) AFAIK the 80m wingspan was gate based, but 2) runway and taxiway limits would cause problems at more than 80m as well. Finally 3) even the -800 could have benefited from a wider wingspan, but my signature explains further... ;)


LH707330 wrote:
SJC has limits on who's allowed to be on taxiways Z and Y when there's a 787, 777, A330, or A340 operating on 30R/12L.


So, what about the idea to unfold wings in flight? Put some badass flaps on the wing to be able to take off with "shorter" wingspan then once airborne retract flaps and deploy longer wings for efficient cruise.

Would that make sense from the aerodynamics point of view?

Badass flaps would increase induced drag, and thus thrust requirements. Plus, the dynamics of folding down the lifting surfaces would have some interesting load path effects, which means ore strength, which is more weight.

The issue with folding wingtips is that it basically needs to stay constrained to the section outside the ailerons. Boeing tried the inboard fold with the 77A, and it shortened the range because it ended the fuel tank prematurely. The 77E basically got all that fuel volume "for free" when they eliminated the fold option that nobody bought.
 
PhilBy
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Re: 80 meters wingspan limit and A380 upgrade

Thu Dec 07, 2017 5:47 pm

workhorse wrote:
Slug71 wrote:
But still, the question is IF someone decided to make an airplane with folding wings with a span >80m when folded and <80m when unfolded, would it still be able to fly to most major airports?


I assume that you mean "a span <80m when folded and >80m when unfolded,"

WIederling wrote:
First order a thinner wing is heavier.


Not always. Once the aeroelasticity has been resolved a thinner, more flexible wing may be the optimum solution for a given weight/span combination. There are some benefits to be gained from the deformation of a flexible wing at max lift (i.e rotation) but a lot of time/cost in design and certification of said flexible wing. Modern automated systems remove a lot of the flutter problems inherent in flexible wings.
 
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Matt6461
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Re: 80 meters wingspan limit and A380 upgrade

Thu Dec 07, 2017 10:53 pm

PhilBy wrote:
workhorse wrote:
Slug71 wrote:
But still, the question is IF someone decided to make an airplane with folding wings with a span >80m when folded and <80m when unfolded, would it still be able to fly to most major airports?


I assume that you mean "a span <80m when folded and >80m when unfolded,"

WIederling wrote:
First order a thinner wing is heavier.


Not always. Once the aeroelasticity has been resolved a thinner, more flexible wing may be the optimum solution for a given weight/span combination. There are some benefits to be gained from the deformation of a flexible wing at max lift (i.e rotation) but a lot of time/cost in design and certification of said flexible wing. Modern automated systems remove a lot of the flutter problems inherent in flexible wings.


A bigger determinant of wing weight is bending stress at the critical MZFW case. Wiederling is correct that a thicker wing reduces weight for that case, as a thicker beam (or spar/skin) is, ceteris paribus, lighter than a thinner one.
 
WIederling
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Re: 80 meters wingspan limit and A380 upgrade

Fri Dec 08, 2017 8:54 am

" Not always. Once the aeroelasticity has been resolved a thinner, .. "

First order approximation of a wing is two flanges ( wingskin) separated by webbing ( beams )
With wider webbing ( profile thickness ) you reduce stress in the skins for the same tranferred moment
( and can reduce material thickness to accomodate the same material stress limits. )
The thinner wing is thus heavier and additionally "softer" to loading.
You want a thin wing when you can not design a low drag profile while using a thicker wing.
Murphy is an optimist
 
PhilBy
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Re: 80 meters wingspan limit and A380 upgrade

Fri Dec 08, 2017 8:21 pm

WIederling wrote:
" Not always. Once the aeroelasticity has been resolved a thinner, .. "

First order approximation of a wing is two flanges ( wingskin) separated by webbing ( beams )
With wider webbing ( profile thickness ) you reduce stress in the skins for the same tranferred moment
( and can reduce material thickness to accomodate the same material stress limits. )
The thinner wing is thus heavier and additionally "softer" to loading.
You want a thin wing when you can not design a low drag profile while using a thicker wing.


But for a give lift/drag ratio a thinner wing is often optimal
 
WIederling
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Re: 80 meters wingspan limit and A380 upgrade

Fri Dec 08, 2017 10:59 pm

PhilBy wrote:
WIederling wrote:
" Not always. Once the aeroelasticity has been resolved a thinner, .. "

First order approximation of a wing is two flanges ( wingskin) separated by webbing ( beams )
With wider webbing ( profile thickness ) you reduce stress in the skins for the same tranferred moment
( and can reduce material thickness to accomodate the same material stress limits. )
The thinner wing is thus heavier and additionally "softer" to loading.
You want a thin wing when you can not design a low drag profile while using a thicker wing.


But for a give lift/drag ratio a thinner wing is often optimal


neither A330 nor A350 appear to be a "drag" in the L/D department. :-)
Murphy is an optimist
 
parapente
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Re: 80 meters wingspan limit and A380 upgrade

Wed Dec 13, 2017 10:57 am

I believe that whilst the 380 wing was 'sized' (generate lift) so that the -9 stretch could be built,it was not stressed for it.From what I can remember one set of the heavier wings were built (and indeed shipped to Toulouse).They were going to be for the cargo version.Then late in the day with all the wiring problems etc the cargo version got cancelled.This would have been the same wing for the future (heVier) 900.
There may well be one set of 'the heavy' wings still sitting there -or perhaps recycled now.
Would make a lovely exhibit at an aircraft museum perhaps.
The lighter 800 wing was as light as it possibly could be-in truth it (just) failed its stress tests by a couple of percent as I recall.Obviously small mods were made to reinforce the point of failure.
 
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SomebodyInTLS
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Re: 80 meters wingspan limit and A380 upgrade

Wed Dec 13, 2017 12:58 pm

parapente wrote:
There may well be one set of 'the heavy' wings still sitting there -or perhaps recycled now.
Would make a lovely exhibit at an aircraft museum perhaps.


AFAIK the partially-built structures for the freighter were quickly scrapped. Quite a shame IMO.
"As with most things related to aircraft design, it's all about the trade-offs and much more nuanced than A.net likes to make out."

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