Taxi645
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Revising the A380 NEO MLG

Sat Nov 25, 2017 6:36 pm

In this very informative thread; viewtopic.php?f=5&t=771991&p=11193763&hilit=a380+wing+high+efficiency#p11137069
Ferpe and Klaus pointed out that the A380 MLG design takes up a lot of potential cargo volume, also because the 6-wheel bogie can't be stored upright.

In recent discussions we've looked at a light weight non stretched A380NEO. In this post: viewtopic.php?f=3&t=1377885&start=800#p19976285 Tomcat roughly calculated that a 16 wheel MLG (instead of 20 wheel) would probably be able to handle about 505T. That seems like a huge weight reduction however, assuming a 14% SFC reduction from a GTF engine over the trent 900 and a range reduction to about 7.700NM, there could easily be a 50T weight reduction from the 1st order fuel load decrease alone.

This would mean that there would be no more 6 wheel bogie and perhaps there would be scope to store it upright after all. This might free up some cargo volume making the plane more competitive for other airliners.


What do you guys think, would:

1 Would it be technically possible to rearrange a 16 wheel MLG so it is stored more efficiently, freeing up cargo volume?

2 Apart from being technically possible, how big a change would this be? Is this something so far reaching that you could effectively start from scratch?
 
Taxi645
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Re: Revising the A380 NEO MLG

Sun Nov 26, 2017 11:40 am

I'll add a video and a PDF to make more clear what the current configuration is. Hopefully it is more obvious then how a vertically stored 4-wheel boogie (instead of the 6 wheels boogie now) would save a lot of space (if it fit's vertically):

https://www.youtube.com/watch?v=3lz96Xi07js

http://www.fzt.haw-hamburg.de/.../text_ ... ngGear.pdf
 
WIederling
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Re: Revising the A380 NEO MLG

Sun Nov 26, 2017 1:00 pm

Murphy is an optimist
 
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Slug71
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Re: Revising the A380 NEO MLG

Mon Nov 27, 2017 5:08 pm

What if it used the A350's MLG? I'm clueless on the technical side of these things, but if the A359 is good for 280T, couldn't you combine another set which would be good for 560T?
 
Taxi645
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Re: Revising the A380 NEO MLG

Mon Nov 27, 2017 7:50 pm

WIederling wrote:


Thanks WIederling, very informative. I'm thinking the maximum gain in the number of LD3 containers would be 2. (+ 4 - 2 in the centre). Not a lot, but it would be a welcome side-effect of downsizing the MLG based on an updated and more realistic market forecast and product positioning in that market for the A380NEO (not designing with the possibility of a 900 in mind). The weight saving would probably amount to between 3-6T depending on the design chosen.

Just wonder what the possibilities are looking at the centre of gravity and the points in the frame where currently the loads are taken. Would require some serious changes, that's for sure.

Slug71 wrote:
What if it used the A350's MLG? I'm clueless on the technical side of these things, but if the A359 is good for 280T, couldn't you combine another set which would be good for 560T?


One perhaps could, although even a slightly stretched A380-850NEO probably wouldn't need a 560MTOW if they keep the range reasonable when using GTF engines. At 560MTOW the improvement in induced drag would be very marginal, that's why I was looking in a much more reduced MTOW.
 
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Slug71
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Re: Revising the A380 NEO MLG

Mon Nov 27, 2017 8:35 pm

Taxi645 wrote:
Slug71 wrote:
What if it used the A350's MLG? I'm clueless on the technical side of these things, but if the A359 is good for 280T, couldn't you combine another set which would be good for 560T?


One perhaps could, although even a slightly stretched A380-850NEO probably wouldn't need a 560MTOW if they keep the range reasonable when using GTF engines. At 560MTOW the improvement in induced drag would be very marginal, that's why I was looking in a much more reduced MTOW.


Agreed. But the A359 already uses a 4-wheel bogie. Most likely more advanced (?lighter?) than the 4-wheel bogie currently used on the A380. So no need to redesign anything, other than fitting.
Whatever off-the-shelf parts (or close to) from the A350 that it (A380) can use, the better. Airbus has to lower production costs on the A380 to keep low rate production sustainable. Remember, a rate cut to 6 per year is a possibility. That should help with costs on the A350 too, you would think?
 
Taxi645
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Re: Revising the A380 NEO MLG

Tue Nov 28, 2017 9:35 am

Slug71 wrote:
Agreed. But the A359 already uses a 4-wheel bogie. Most likely more advanced (?lighter?) than the 4-wheel bogie currently used on the A380. So no need to redesign anything, other than fitting.
Whatever off-the-shelf parts (or close to) from the A350 that it (A380) can use, the better. Airbus has to lower production costs on the A380 to keep low rate production sustainable. Remember, a rate cut to 6 per year is a possibility. That should help with costs on the A350 too, you would think?


It's difficult for me to judge how much change would be needed to the A350 MLG to be usable on an A380NEO and if there would be any significant benefit technically (weight) or financially. 6 or 8 per year will be for the A380CEO not NEO, although cost reductions are welcome at any rate of course.


I wonder if there would be scope for storing the front 4-wheel bogie inside the wing and why that wasn't done for the CEO? If you look at the A380 frontal view, there seems to plenty of room for it. I can imagine it being a fuel volume thing and/or perhaps a change in centre of gravity complication. With the fuel volume requirement for the A380NEO being so dramatically lower, one would imagine the former not being an issue. Perhaps someone more technically inclined would be so kind to step in and expand a bit on the feasibility of the A380 front bogie being stored in the wing?

With the front 4-wheel bogie folding into the wing, the cargo length taking up by the MLG would go down from the equivalent of the length of 5.5 wheels (2 from the front bogie, 3 from the rear and space in between) to only the length of 1.5 wheels, a two axle bogie stored (almost) upright. That would be a major increase in cargo volume, probably four extra LD3 containers (+ 8 – 4 in the centre).
 
WIederling
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Re: Revising the A380 NEO MLG

Tue Nov 28, 2017 10:04 am

Taxi645 wrote:
Perhaps someone more technically inclined would be so kind to step in and expand a bit on the feasibility of the A380 front bogie being stored in the wing?


The A380 wing skin is an Al multi layer "composite" load bearing item. If you start to break it for gear doors ...
Same for integrating room for the gear leg inside the wing displacing tankage.
Currently all MLG legs fold into space behind the Center wing box and its extension into the wings.
Load bearing structure is unbroken going from wingtip to wingtip.
Murphy is an optimist
 
Taxi645
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Re: Revising the A380 NEO MLG

Tue Nov 28, 2017 10:42 am

WIederling wrote:
Taxi645 wrote:
Perhaps someone more technically inclined would be so kind to step in and expand a bit on the feasibility of the A380 front bogie being stored in the wing?


The A380 wing skin is an Al multi layer "composite" load bearing item. If you start to break it for gear doors ...
...
Load bearing structure is unbroken going from wingtip to wingtip.


Thanks. That makes sense and I should've been able to figure out that one myself. So then I think a maximum additional cargo capacity due to the revised 16 MLG would be 2 LD3's (see above), if technically and financially feasible. That's not earth shattering, but would be a nice bonus none the less.
 
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william
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Re: Revising the A380 NEO MLG

Tue Nov 28, 2017 6:08 pm

I am glad you started a second thread on this, it is interesting. If one puts the A380 on major enough diet, could it be one could replace the inboard six wheel bogeys with two dual wheel MLG instead? Think the center gear on the A340 but two of them instead. That would open up further cargo room. The present four wheel bogey under the wings could be upgraded to six wheel bogeys to help with pavement loading.

This is all fanciful thinking of course, I imagine it would require a massive re engineering to accomplish the above.
 
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Matt6461
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Re: Revising the A380 NEO MLG

Fri Dec 01, 2017 5:06 am

Taxi645 wrote:
2 Apart from being technically possible, how big a change would this be? Is this something so far reaching that you could effectively start from scratch?


I raised this idea a few years ago in one of my A380X threads:

In addition, we are also changing the arrangement into a conventional design that puts the MLG behind the wing box instead of on each side of a shrunken cargo compartment. The 747-8, which has a higher MTOW than my A38X, employs this design. The revised arrangement has multiple benefits: first, it allows 2 more LD-3 spots in the underbelly. Second, it enables significantly shrinking the flat pressure bulkheads that surround the “T”-shape aft cargo compartment in the A388. For reference, look at the layout of that rear cargo compartment. It is ~32 feet long. It requires, on each of its sides, a flat pressure bulkhead. In addition, a pressure bulkhead goes underneath the cabin floor from the compartment to the fuselage sidewall. The side bulkheads are ~5.5ft tall, the underfloor bulkheads are ~6 feet wide. Thus we have ~350ft2 of flat pressure bulkheads. These bulkheads are extremely heavy: it is structurally very difficult to pressurize a flat object. If we remove them, and replace this section of the plane, which is covered by the belly fairing, with fuselage tube instead, we’re looking at huge savings. Yes, we have to pressurize the walls around the revised layout, but this is a much more compact area. If the bulkheads weigh 15lbs/ft2, and we replace them with half as much fuselage area at less than a third of bulkhead weight per area, we realize 2-3,000lbs in weight savings. Let's be conservative and taken a 2,000lb weight saving from the exchange.


viewtopic.php?t=774669#p11173035

So I think you're underestimating the potential impact of this revision but also the cost of such a revision.
You would need to change the pressure bulkhead structure as well as move/replace all wiring and systems built to the specifications of the current structure. It would be a HUGE undertaking - another reason I'm now more in favor of replacing the A380 than revising it.

But if you're doing a new wing - as your misleadingly-labeled "A380NEO" concepts suppose - then MLG revision is probably both necessary and beneficial.
 
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Matt6461
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Re: Revising the A380 NEO MLG

Fri Dec 01, 2017 5:23 am

Further to my last reply, the question you've framed, along with most of the replies here, is tackling an issue that would never arise:
If you're spending enough money to rearrange the MLG, that has to be a part of larger project with new wing/engines/empennage.
In that scenario, the A380's MTOW wouldn't be anywhere near 500t. So much structural weight in wing/empennage/engines/MLG comes out of a revised A380 that it would be low-400's tonnes of MTOW. Thus using a conventional MLG is easy, a la 747-8.

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