Moderators: richierich, ua900, PanAm_DC10, hOMSaR

 
User avatar
Matt6461
Topic Author
Posts: 2991
Joined: Wed Oct 16, 2013 9:36 pm

A380NEO: Revisions And BizCase Unclear,2020-25EIS

Thu Jul 23, 2015 8:12 am

As most of us know by now, Airbus has publicly stated its *intent* to launch an A380NEO but is still considering the business case and which revisions will be included. http://airwaysnews.com/blog/2015/07/...o-decision-made-to-launch-a380neo/

Airbus Commercial CEO Fabrice Bregier let slip interesting details by saying:
-EIS will be somewhere between 2020 and 2025
-Engines will be sole-source, may not be clean sheet
-Revisions will include a "better wing"
-A stretch is possible
-Other revisions not yet determined
-Will not be done for just one customer
-A380NEO will not go forward without a business case (not really that interesting...)

http://www.ttgdigital.com/news/airbu...lans-upgraded-a380/4697900.article

Some of us would like a thread for discussing:
-Whether Airbus seems to be moving towards or away from an A380NEO, both in timing and likelihood
-Whether Airbus *should* do a NEO - i.e. is there a realistic business case
-What kinds of revisions should be included in the NEO?

Regarding specific revisions, forumers have discussed a range of possibilities:

-Straight-forward NEO with RR Advance engines. Modeled by Leeham and AirwaysInsight. http://airwaysnews.com/blog/2015/01/...ut-a-business-case-exists-for-neo/
http://leehamnews.com/2014/12/17/a38...ep-analysis-of-its-competitivness/
http://leehamnews.com/2014/02/03/upd...-a-neo-version-and-whats-involved/
(warning - first Leeham analysis has a huge clerical error in the charts re 777X fuel burn. See comment by Leeham)

-NEO with half-stretch

-NEO "lite" - a big PIP from EA/RR, plus maybe a stretch and aero tweaks. http://leehamnews.com/2015/04/26/can...a380-what-emirates-airlines-wants/

-Whatever "better wings" means - a new CFRP wing a la 777X? Just winglets?

This thread is forumers who want to discuss the evolving news and contours A380NEO, along with the likely and/or best future direction of the A380. Nothing is off the table, from program termination to an aggressive makeover around new wings. If you're looking only find news stories, this thread isn't for you.
-----------------------------------------------------------------------------

Because a lot of discussions about how a NEO will behave aerodynamically and economically rely on some basic calculations, I have decided to invest some time in a model for anyone who wants to use it. A link to two public Google Docs, downloadable as Excel spreasheets, is below. Doing math on the forum is hard, Excel/Google Docs is so much easier. If you'd like, take the model and change it as you see fit, though transparency is highly encouraged as well as reciprocal sharing of improved model versions. It's open to editing for now, we'll see how that works.

The model is conceptually simple:
-Take two A380's landing at OEW+payload. One a NEO/PIP/NWO, the other a CEO
-Work backwards, figuring relative drag for small segments of flight
-Induced, parasitic, and wave drag are calculated according to basic aero parameters: span, wingloading=FL, weight, wetted area, SFC, and drag coefficients
-Because both planes are some version of A380, we can abstract fine details regarding fuselage form, airfoil characteristics, interference drag etc.
-Add weight to A380CEO (3% at a time) until it reaches its MTOW (small difference in climb specification)
-MTOW of NEO/PIP/NWO is that plane's weight when A380CEO reaches MTOW

Really briefly, the important relationships (the "~" sign here means "proportional to")

Induced drag ~ (Lift^2)/(Span^2)/(air density)

Parasitic drag ~ (Wetted Area)*(drag coefficient)*(Air density) - I assume equal cruise mach number

A380 fuselage designed for no wave drag at M.85, so wave drag ~ (wing area)*(air density) - smaller term.

Air density ~ wing loading.

In addition to the aerodynamics model (Sheet 1 - drag buildup), other important sheets:

"2-Wing/Structure" - this estimates wing and fuselage stretch weight according to basic aero/engineering stuff from, e.g., the Stanford Aerodynamics department. http://adg.stanford.edu/aa241/

Sheets 3&4 address empennage and engine weight, including takeoff constraints. Mostly irrelevant if you're keeping the wing.

Sheet 5 is where it all comes together.

It imports the fuel burn, aircraft weight, and seat totals from sheets 1&2 into an "Operating Cost Model" and an "OEM Business Case Model."

For the "Operating Cost Model," I imported Leeham's A380CEO trip cost components. Cells represent fractional values of trip cost for maintenance, fuel, capital, crew, and fees. You can toggle "Gas Price" and the fractions change, trip cost increases.

Below the A380CEO cells, your A380NEO's new fuel burn, engine size, frame size, and crew size values are automatically imported and create new trip cost component values for your A380NEO! You can toggle sales price, which then updates trip cost. You can see in an instant the CASM of an A380NEO with, say 17% fuel burn delta, 15% capital delta, and a slightly larger crew.

In addition to updating trip cost, toggling sales price updates the "OEM Business Case Model" below. This estimates A380NEO versions according to weight, engine size, production rate, and materials used. You can toggle "OEM investment" to find the expected ROI of X number of A380's selling for X price at X cost to produce.

I'm sure whoever uses the model will have some clarifying questions. I'll try to answer here. Meant to get this up yesterday but day job was calling...

Anyway, without further ado,here are links to two specific applications of the model:

http://docs.google.com/spreadsheets/...R4HHpLr_jQ3kpjCYU/edit?usp=sharing

http://docs.google.com/spreadsheets/...U25EirmQTXEIGEylU/edit?usp=sharing

One models an "A380-850NEO" with a 10.5ft stretch, RR Advance engines with -10% SFC delta, winglets, and a rational payload reduction to remove wing weight. Its Economics page looks like this:

http://i592.photobucket.com/albums/tt8/matt6461pics/-850NEO%20Economics_zpszqkovcgs.png

The other models an "A380NWO." It has a new 90m CFRP folding wing, new engines of clean-sheet design and -11 SFC (PW NextGen GTF's), a smaller empennage, and - because its MTOW is only ~455t, very slight tweaks to MLG (I'm thinking just reduce gauge of titanium pillars and struts, pull off some breaks, remove a couple wheels - same plan and actuating machinery). It's economics page looks like this:

http://i592.photobucket.com/albums/tt8/matt6461pics/A380NWO%20Economics_zps1p0rj6jp.png

Many of you know my position on where Airbus should go here.

The -850NEO is 17% better on fuel/pax, but only 7.2% better on CASM after the price premium needed for 30% ROI.
The A380NWO (not X, much simpler), is 20% better on CASM with higher project ROI.

But my assumptions are open to adjustment by anybody using the model - sales price, SFC, weight, etc. Somebody want to model the PIP/stretch with low investment?

Anyway, let's discuss.

[Edited 2015-07-23 01:37:00]
 
User avatar
JerseyFlyer
Posts: 1574
Joined: Fri May 25, 2007 7:24 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Thu Jul 23, 2015 12:23 pm

I seem to recall that one of the test flight surprises on the 380 was that it achieved greater lift from the fuselage shape than expected. Would this be better again from a stretch or is it not material?
 
User avatar
Matt6461
Topic Author
Posts: 2991
Joined: Wed Oct 16, 2013 9:36 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Thu Jul 23, 2015 4:44 pm

Quoting JerseyFlyer (Reply 1):
greater lift from the fuselage

I wasn't aware of this, thanks.

Usually lift from the fuselage is something designers specifically try to avoid. As low aspect-ratio as the A380's wing is by modern standards, any fuselage is going to be much worse obviously. Thus it creates far too much induced drag per unit of lift.

One of the benefits of variable camber airfoils, for example, is that they can adjust the wing's angle of attack to avoid creating fuselage lift during climb.

Assuming that the fuselage did provide unexpected lift, I would expect that, when Airbus increased wing twist a few years ago, one of the benefits was avoiding fuselage lift. This change allowed the wing to be at a higher angle of attack in steady flight, without pitching the fuselage up and thereby creating undesired lift. It adds to the downward pitching moment created by the forward fuselage shape, but the added trim drag necessary for stable flight is probably outweighed by avoiding induced drag created by fuselage lift.
 
mjoelnir
Posts: 9411
Joined: Sun Feb 03, 2013 11:06 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Thu Jul 23, 2015 8:26 pm

Quoting Matt6461 (Reply 2):
Usually lift from the fuselage is something designers specifically try to avoid.

That would be completely new to me and I could not imagine any reason why that should be. The designs I know about calculate with the fuselage lift, allowing for slightly smaller wings and reducing overall drag.

I think you are falling in a "textbook trap" were the author separates fuselage from wing to easier employ his theories, to make the calculations more simple.

[Edited 2015-07-23 13:57:30]
 
A342
Posts: 4017
Joined: Sun Jul 31, 2005 11:05 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Thu Jul 23, 2015 8:54 pm

Quoting mjoelnir (Reply 3):
That would be completely new to me and I could not imagine any reason why that should be. The designs I know about calculate with the fuselage lift, allowing for slightly smaller wings and reducing overall drag.

   MiG-29, Su-27 anyone?


Aside from that, Matt6461, don't you notice that your mantra of a new wing sound like a broken record? We all know your opinion very well by now, what's the point of repeating it time and time again?
Exceptions confirm the rule.
 
User avatar
Matt6461
Topic Author
Posts: 2991
Joined: Wed Oct 16, 2013 9:36 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Thu Jul 23, 2015 9:15 pm

Quoting mjoelnir (Reply 3):
That would be completely new to me and I could not imagine any reason why that should be. The designs I know about calculate with the fuselage lift, allowing for slightly smaller wings and reducing overall drag.

I think you are falling in a "textbook trap" were the author separates fuselage from wing to easier employ his theories, to make the calculations more simple.

I'll let aeronautical engineer Bjorn Fehrm handle this for me:

Quote:
The wing variable camber on A350 (and 787) is primarily there to align the fuselage for lowest drag during cruise. The fuselage is a lifting surface with the worst induced drag possible, long and narrow. Thus you don’t want to fly it with higher angle then for lowest drag. At high weights the wing needs higher angle or more camber to generate the necessary high lift, ie with variable camber you can align the fuselage for best overall lift over drag despite needing a lot of lift from the wing. On a non variable camber aircraft you need to crank up the fuselage to get the wing angle necessary for the high lift needed, not ideal as the fuselage is playing short span wing and creates a lot of induced drag.[quote]

http://leehamnews.com/2014/11/04/fun...ls-of-airliner-performance-part-1/

This quote is in Bjorn's comment on the article. Easiest way to find it is "Find" function for "fuselage."

[quote=A342,reply=4]MiG-29, Su-27 anyone?

You're confusing "wing in fuselage" lift with pure fuselage lift. For Mig and Su, most of the fuselage is within the wing's planform. This goes for the part of airliner's wings within their planforms as well - thus Ferpe's spreadsheets, for example, differentiate between "exposed" wing area and gross wing area. The portion of the of the wing that is within/under the fuselage is surrounded by the exposed wings, thus vortices can't form on its lifting surface to the same extent as happens on non-wing fuselage. Just visualize the air swirling up around the non-wing fuselage to equal out pressure differences between top and bottom and you can intuitively grasp the effect.

[Edited 2015-07-23 14:20:31]
 
User avatar
speedbored
Posts: 2230
Joined: Fri Jul 19, 2013 5:14 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Thu Jul 23, 2015 10:18 pm

Quoting Matt6461 (Reply 2):
Usually lift from the fuselage is something designers specifically try to avoid.

Actually, designers specifically design fuselage lift in. If you re-read the quote you posted from Bjorn, you might see that he is not saying that fuselages should not produce lift, he is saying that, in-flight, the fuselage is optimally flown at the best lift/drag ratio.

Fuselages by their nature have to deflect air around them, which creates drag. Some of the shape constraints imposed by things like the pilots needing to be able to see where they are going, or to avoid tailstrikes, mean that lift is going to be created whether you want it or not. But if, with clever shaping, the fuselage can be used to create lift without adding significantly to the drag it is going to create anyway, then why would you not choose to do that when it means you can then design a smaller, lighter wing?

How Much Lift Does The Fuselage Provide? (by CoolGuy Aug 2 2007 in Tech Ops)

Quoting Matt6461 (Reply 2):
This change allowed the wing to be at a higher angle of attack in steady flight, without pitching the fuselage up and thereby creating undesired lift.

A triumph of academic reasoning over reality. They actually twisted the wing 1.5 degrees in the other direction, for a lower angle of attack.
 
User avatar
Matt6461
Topic Author
Posts: 2991
Joined: Wed Oct 16, 2013 9:36 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Thu Jul 23, 2015 10:58 pm

Quoting speedbored (Reply 6):
mean that lift is going to be created whether you want it or not.

Yes it does. But you want to minimize it.

Your argument structure is this:

(1) fuselage lift is unavoidable
(2) therefore, fuselage lift is not something to minimize

Other bad arguments have the same structure:

(1) drag is unavoidable
(2) therefore drag is not something to minimize

The reason to minimize fuselage drag is perfectly stated by Bjorn:

Quote:
not ideal as the fuselage is playing short span wing and creates a lot of induced drag.
Quoting speedbored (Reply 6):
They actually twisted the wing 1.5 degrees in the other direction, for a lower angle of attack.

On an axis of rotation, you either increase or decrease. If they twisted the wing the "in the other direction," they would call this a "decrease" in wing twist. They don't:

http://www.flightglobal.com/news/art...ing-new-higher-weight-a380-341926/

Quote:
incorporate a 1.5 degree increase in twist to further optimise aerodynamics as part of the improvement package.
Quoting speedbored (Reply 6):
A triumph of academic reasoning over reality.

What's up with you and all this "Take yur book-lurnin elsewhere Sonny" stuff lately? Weird thing about aerodynamics is it follows some basic laws that, yes, one can find in text books. Almost like it's a science huh?

[Edited 2015-07-23 16:02:58]

[Edited 2015-07-23 16:13:04]
 
User avatar
Matt6461
Topic Author
Posts: 2991
Joined: Wed Oct 16, 2013 9:36 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Thu Jul 23, 2015 11:11 pm

In other news, you can take a peak at AirInsight's supportive case for the A380NEO. https://books.google.com/books?id=-YW_BgAAQBAJ&pg=PA15&dq=a380neo+%22business+case%22&hl=en&sa=X&ved=0CCcQ6AEwAGoVChMI476Tg6_yxgIVwjo-Ch1x8Abv#v=onepage&q=a380neo%20%22business%20case%22&f=false

The whole thing will set you back $396.
 
mjoelnir
Posts: 9411
Joined: Sun Feb 03, 2013 11:06 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 24, 2015 1:29 am

Quoting Matt6461 (Reply 5):
You're confusing "wing in fuselage" lift with pure fuselage lift. For Mig and Su, most of the fuselage is within the wing's planform. This goes for the part of airliner's wings within their planforms as well - thus Ferpe's spreadsheets, for example, differentiate between "exposed" wing area and gross wing area. The portion of the of the wing that is within/under the fuselage is surrounded by the exposed wings, thus vortices can't form on its lifting surface to the same extent as happens on non-wing fuselage. Just visualize the air swirling up around the non-wing fuselage to equal out pressure differences between top and bottom and you can intuitively grasp the effect.

I am not confusing nothing and what you wrote has nothing to do with the argument.

Ferpe is not talking about if fuselage lift is desirable or not. If you take a look at every new fuselage moved away from the plain symmetric cigar non lift fuselage, but are being designed as fuselage with lift, even the areas between fuselage and wing are more and more lift orientated, just have a look.

Than have a look at a typical fuselage specially developed for lift, on the Piaggio 180 and read why the lift in the fuselage leads to especially low drag. Have a look at some Rutan designs. After you have done that and learned something come again to this discussion.
 
User avatar
Matt6461
Topic Author
Posts: 2991
Joined: Wed Oct 16, 2013 9:36 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 24, 2015 4:48 am

Quoting mjoelnir (Reply 9):
I am not confusing nothing

The "confusing" remark was meant for A342. Impolite, I admit. This is TechOps, I should make a special effort to be civil.

Quoting mjoelnir (Reply 9):
Ferpe is not talking about if fuselage lift is desirable or not.
Quoting mjoelnir (Reply 9):
Than have a look at a typical fuselage specially developed for lift, on the Piaggio 180

Bjorn's quote from Leeham is pretty clear that, for minimum drag, you don't want to increase fuselage lift.

I know there are design concepts that seek lift from the passenger compartment, including some from "lifting fuselage." BWB, flying wing, pax-loaded wing. I have read about all of these. It's efficient to put "lift where the load is." If you're designing a plane to take advantage of those efficiencies, it can be a good path and may be where future planes are headed. My comments are limited to "tube-wing" aircraft, where fuselage shape is extremely low AR (.2?).

Just intuitively think about how efficient a wingless tube would be at cruise (assume it's dropped from a bigger plane or something). The closest real world analogy is a missile. A quick google search tells me that the L/D for the Soviet EKR missile would have been 2.5. http://en.wikipedia.org/wiki/EKR_(missile) I note that it is a supersonic craft, but the Concorde was at ~7 L/D and had relatively more wing than a missile.

And yes, even for "simple" tube-wing aircraft, because some fuselage lift is inevitable, the designer should take this into account when defining the wing.

But let's take a step back and take a look at how this discussion started. A forumer commented about the A380's higher than expected fuselage lift. I hadn't heard of this, but I had heard of the increase in wing twist - which happened. No doubts about that. Given that the A380 wing is what is (for now), if it need X amount of lift in cruise, it's better to get that lift from your wing than from your fuselage.

One way to do this is to increase wing twist. The wing always flies at the same angle of attack for max L/D, so what that twist does in cruise is lower the fuselage angle of attack - thereby lowering its lift. (wing twist also helps at takeoff of course). I think this is what led Speedbored astray - it's the fuselage AoA, not the wing's that is changed. That seems like a good explanation of why the increased wing twist helps the A380's cruise performance. But if you have a better explanation of the effect, please share.
 
mjoelnir
Posts: 9411
Joined: Sun Feb 03, 2013 11:06 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 24, 2015 8:38 am

Quoting Matt6461 (Reply 10):
Bjorn's quote from Leeham is pretty clear that, for minimum drag, you don't want to increase fuselage lift.

That may be and it may be his opinion but that does not make it right. Combining that and the information that the A380 got a change in wing twist can have nothing to do with each other.

You keep going on in this direction just because it fits your pet project.

Again learn about fuselage lift, have a look at modern fuselage and see that they are providing rather than eliminating additional lift compared to the simple tube and do your thinking and research before posting.
 
A342
Posts: 4017
Joined: Sun Jul 31, 2005 11:05 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 24, 2015 9:31 am

Quoting Matt6461 (Reply 10):
The "confusing" remark was meant for A342. Impolite, I admit. This is TechOps, I should make a special effort to be civil.

Maybe it's indeed a different case on the MiG-29 and Su-27. I happily confess to being no expert in aerodynamics. But let's do a little theoretical excercise.


You design an all-new commercial aircraft and because you're a company that wants to get this aircraft 100% right, you give two teams the assignment to design a fuselage with a given pax and cargo capacity.

After the design phase is finished, you build scale models of both fuselages and put them in a wind tunnel, simulating the same cruise conditions and the same AOA.

You conclude that both fuselanges have exactly the same drag. But the fuselage designed by team A also produces some lift, while team B's fuselage doesn't.

Which would you prefer to use?


In other words: Airbus designed the A380's fuselage to have a drag as low as possible, which was probably successful, since in flight test the total drag of the aircraft was found to be lower than expected.
Now if the fuselage also produces some lift AFTER daid optimisation, why would Airbus discard it?

Or to put it another way: Do we really know what percentage of the fuselage drag is inevitable and what percentage is ONLY due to producing lift? I say we don't.

Could Airbus have come up with a fuselage design that doesn't produce lift? Yes, they probably could have.
Are we sure that such a fuselage would necessarily have a lower drag than the present one? I say we don't.

Quoting mjoelnir (Reply 11):
You keep going on in this direction just because it fits your pet project.

  
Exceptions confirm the rule.
 
mjoelnir
Posts: 9411
Joined: Sun Feb 03, 2013 11:06 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 24, 2015 10:36 am

Quoting A342 (Reply 12):
Quoting Matt6461 (Reply 10):

Just as a sign you can look for if a fuselage should produce lift. Take a tube make both ends a symmetrical point. If you than not angle above the wind you practically only have drag not lift. Now move the point of the nose down on the tube, not compared to the direction of the wind, and the fuselage will produce lift. You can increase that by making all the upper line of the tube a lifting profile. Have look at the Piaggio P 180 Avanti. But having all the fuselage as a profile has serious drawbacks for the usage of the inner volume and production cost.
Now have a look at most off the modern fuselage 787, A350, C100/300 etc and tell me what this designers do to avoid lift in the fuselage, or are they in reality designing the fuselage to provide a lift component.

Compare the A350 with the A330 and think what fuselage would likely produce more lift.
A350 point of nose moved down and pointed end of fuselage moved down, both changes increasing fuselage lift.

Than dear Matt6461 start using your brain and start again.

[Edited 2015-07-24 03:59:53]

[Edited 2015-07-24 04:22:55]
 
User avatar
seahawk
Posts: 9865
Joined: Fri May 27, 2005 1:29 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 24, 2015 11:34 am

Every fuselage creates lift. A few percent on Cessna, ~10% for a small twin, 15% on a 747 - more an a A380. Much more a lifting body design.

What Ferpe - Bjorn Fehrm means is that you optimize the angle of attack in cruise for minimal drag, any lift created by the fuselage in that configuration is welcome. And if you look at the A380 profile, it must create lift.
 
User avatar
speedbored
Posts: 2230
Joined: Fri Jul 19, 2013 5:14 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 24, 2015 12:55 pm

Quoting Matt6461 (Reply 7):
The reason to minimize fuselage drag is perfectly stated by Bjorn

That is not what Bjorn is actually saying - he is saying that you want to minimise the lift caused by fuselage AoA. The lift generated by the A380 fuselage is not because it cruises nose-up. But, regardless, if there is a need to minimise lift from the fuselage, perhaps you could explain to us why so many conventional tube and wing aircraft have fuselage lift deliberately designed in, and not designed out as you claimed?

Quoting Matt6461 (Reply 7):
What's up with you and all this "Take yur book-lurnin elsewhere Sonny" stuff lately? Weird thing about aerodynamics is it follows some basic laws that, yes, one can find in text books. Almost like it's a science huh?

What is up with me is you making absolute statements that fit the "basic laws" that you have learnt, and which might even be correct in a perfect system, but are wrong once all those pesky real-world factors start affecting things. Comments like:

Quoting Matt6461 (Reply 2):
This change allowed the wing to be at a higher angle of attack in steady flight, without pitching the fuselage up and thereby creating undesired lift.

A 10 second Google search would have shown you that this is the exact opposite of what was actually done. The 1.5 degree increase in twist was specifically to reduce the angle of attack at the wingtips.

If fuselage lift was such a bad thing, perhaps you could also explain why Airbus, after determining that fuselage lift was higher than expected, would choose to reset aircraft trim by altering wing twist to reduce wing lift rather than by altering the fuselage to reduce lift there?

Quoting Matt6461 (Reply 7):
On an axis of rotation, you either increase or decrease. If they twisted the wing the "in the other direction," they would call this a "decrease" in wing twist. They don't:

My "other direction" comment was in response to your "increase angle of attack" assertion.

Quoting Matt6461 (Reply 10):
One way to do this is to increase wing twist. The wing always flies at the same angle of attack for max L/D, so what that twist does in cruise is lower the fuselage angle of attack - thereby lowering its lift.

Comments like this suggest that you think that wing twist is the angle at which the wing attaches to the fuselage. It is not - Airbus have not changed the angle at which the wings are attached to the fuselage. Wing twist is how the angle of attack varies along the length of the wing to control the distribution of lift along the wing. Its most important purpose is to ensure that, in a stall, the wingtips are the last part of the wing to stall, so as to maintain control for as long as possible. A twisted wing essentially has an infinite number of angles of attack.

In this particular instance, all else being equal, the increased twist would actually have the opposite effect to the one you claim. An increase in twist would reduce the angle of attack for the majority of the length of the wing but increase it slightly near the wing root to compensate, hence pitching the fuselage up and increasing fuselage lift slightly.

Or, to look at it another way, if as you suggest, the fuselage angle of attack were being reduced, to reduce fuselage lift, then the wing root angle of attack would also have to be reduced (because there is no change to the angle of attachment), hence reducing lift at the wing root. The increased twist would then further increase the reduction of the AoA as we go out towards the wingtip, reducing lift there by even greater proportions. The aircraft would simply cease to remain in the air.

Quoting Matt6461 (Reply 10):
it's the fuselage AoA, not the wing's that is changed.

No, it is not. It is both.

Quoting Matt6461 (Reply 10):
I think this is what led Speedbored astray

I was not at all astray. You were - see above.
 
Pihero
Posts: 4318
Joined: Mon Jan 31, 2005 5:11 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 24, 2015 4:26 pm

Quoting Matt6461 (Reply 10):
One way to do this is to increase wing twist.

This is where this thread starts getting wrong and - per force - totally indigestible : A lot of assumptions born on unqualified and, basically uninformed, premices.
1/- Wing Twist is a very normal ( every aircraft has it ) feature that diminishes the wing AoA from root to wing tip, so that on a swept wing, the tip stalls last, therefore providing a nose-down moment to the whole airplane at the stall onset.

2/- Wing INCIDENCE is the angle between the fuselage centerline and the wing chord, so with the fuselage level, the wing has already a ( globally positive ) AoA..

3/- That said for you to assimilate a wing efficiency just with its aspect ratio is quite a formidably simplistic view.
That wing was limited, right from the beginning by two parameters :
3.1/- the 80m box, limiting its span
3.2/- the wing root chord which shouldn't exceed 60 ft (for safety / evacuation reasons ).
Contrarily to what you're thinking, that wing's performance equals or exceeds anything built before it : we're not talking about Mickey Mouse aerodynamics here, but real life, real experience, real outstanding engineering.

Could it be improved ?

*- Yes : sharklets à la A350 : the height of the sharklet equals to a virtual half span increase of 60% ... so a two meter high winglet would bring the virtual span to 83 meters, with better wing tip vortices control.

*- Yes : introduce the cruise variable camber pioneered on the A350, making it a truly cruise adaptative wing.

*- I personally do not agree / believe in folding wig tips : weight, structural weight augmentation and discontinuity in the wing at cruise ( aeroelasticity ) and with high lift devices extended.

As for the fuselage lift
See the studies Airbus led on the subject, especially on the nose design. Most of the fuselage lift comes from the nose, and that design is so smooth that it won't see a supersonic airflow before M.89.
The beauty of that nose is that the lift generated helps reduce the down force required on the horizontal tailplane, hence helping reduce it's size.
Here are some links on the subject of the A380 wing design :
ONERA A380 pressure field

The *numerical aerodynamics study* gives a clear pattern of the pressure field around the airplane. Note that the nose is an area of positive pressure. The depression on the fuselage at and above the wing joint is the result of the wing + fairing interaction... The fuselage then takes some of the overall lift.
It is a bit more obvious on the *structure coupling* image. That result comes also from the tailoring of the fairing to be as close as possible to the Whitcomb area rule between the fuselage and the inner engine.

...and some pics
Here is a study by the Germans, in layman's terms the challeges and the solutions :
the A380

BTW, Fabrise Bregier is not the commercial ceo, he is the President and CEO of Airbus
Tom Enders is the CEO of *Airbus Group* - ex EADS -.

[Edited 2015-07-24 09:28:10]

[Edited 2015-07-24 09:33:11]
Contrail designer
 
User avatar
airmagnac
Posts: 451
Joined: Wed Apr 18, 2012 10:24 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 24, 2015 5:46 pm

Quoting Matt6461 (Reply 7):
Your argument structure is this:

(1) fuselage lift is unavoidable
(2) therefore, fuselage lift is not something to minimize

Other bad arguments have the same structure:

(1) drag is unavoidable
(2) therefore drag is not something to minimize

With all due respect, such kindergarden arguments are not helping your case. Fuselage lift and drag cannot be compared so simplistically

(1) drag is unavoidable
(2) drag is a negative product (a cost)
(3) therefore drag is to be minimized

Whereas
(1) fuselage lift is unavoidable
(2) fuselage lift is itself a positive product, but on the other hand it also leads to induced drag which is a negative
(3) fuselage lift is a fraction of total aircraft lift (which is the only interesting value to be optimized)
(4) fuselage induced drag is a fraction of total aircraft drag (which is the only interesting value to be optimized), and is even only a fraction of total fuselage drag
(5) all these parameters evolve vs one another depending on flight conditions
(5) therefore depending on how fusleage lift and drag relate to each other and to other lift and drag sources on the aircraft in all the various operating conditions, the optimum fuselage lift is...hard to define (sometimes as high as you can make it, sometimes as small as you can make it, and usually somewhere in between I guess)

Which is basically what other have been saying before me. And also fits with Ferpe's point, which is about maintaining optimum L/D, not simply removing lift. [ Edit : Pihero got there before me ]

And I suspect that lift distribution could be of interest in this discussion too (a front-loaded lift distribution could relieve the downforce of the empennage)

Quoting Matt6461 (Reply 7):
Weird thing about aerodynamics is it follows some basic laws that, yes, one can find in text books

The problem is not with the textbook theory, it's with how you apply the theory to the real world.
Models are built by splitting the product of interest (here the aircraft) in smaller parts, and recursively applying the theory to each sub-part in an adapted way. In this case, the wings, the fuselage, the empennage, the gear etc...
The 2 natural traps into which you eagerly fall into are that
1) you are applying simplistic or not applicable versions of the theories to each sub-part (e.g. your argument about "production costs scales directly with weight" in the CivAv thread, regardless of 30 years of digital innovations)
2) you disregard the interdependencies between the sub-parts. See the "fuselage lift must be eradicated", regardless of its magnitude compared to other sources of lift & drag. Or completely disregarding the impact of systems on your cost calculations (OK I might be biased on this topic)

The second one is a classic error. The problem is that the sum of optimals is not the optimal of the sum...ie the optimum aircraft is not the conjunction of the best wing, fuselage, systems etc...


----
Now as for your Excel, I've just taken a quick look. But it's really difficult to understand anything....I take it you are not an Excel expert !  
So just on an IT level for now : try using range names (the box on the top left, next to the cell content bar) and call your calls CEO_Cdi or something like that. It will make your equations much easier to read.
Also, try to gather the constants and global variables in a seperate sheet. Same for all your assumptions, so you can track them and make sensitivty studies.
Maybe tag some cells with comments, to explain what the formula is about if it's a little complex. Adding the source could be useful too.

With so many parameters varying at the same time, I'd also write some macros to run N calculation sequences instead of copy/pasting, but let's keep that for later

At the aerospace level, the "volume" of the model is...well, small. I' ve just produced about 5 times worth of Excel data to assess the weight & costs of a few cables, ducts and pipes. And I still don't have the total weight and costs...
That would make me skeptical about the accuracy of the outputs, but as mentioned I just had a quick look. Nor did I ever have time to go through your other threads here.

[Edited 2015-07-24 10:49:29]

[Edited 2015-07-24 10:49:54]
My goal as an engineer is to fill my soul with coffee and become immortal
 
User avatar
seahawk
Posts: 9865
Joined: Fri May 27, 2005 1:29 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 24, 2015 6:42 pm

Quoting Pihero (Reply 16):
Here is a study by the Germans, in layman's terms the challeges and the solutions :
the A380

Thank you for that and your whole post.
 
A342
Posts: 4017
Joined: Sun Jul 31, 2005 11:05 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 24, 2015 7:24 pm

Quoting Pihero (Reply 16):
...and some pics
Here is a study by the Germans, in layman's terms the challeges and the solutions :
the A380
Quoting seahawk (Reply 18):
Thank you for that and your whole post.

I second that. A question that ocurred to me on page 47: Why is the A300-600 wing so much more efficient than the A300-B4's? I thought it is essentially the same, with only those mini-fences added.

Off-topic, I know, but it doesn't warrant its own thread...
Exceptions confirm the rule.
 
Pihero
Posts: 4318
Joined: Mon Jan 31, 2005 5:11 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 24, 2015 9:26 pm

Quoting A342 (Reply 19):
Why is the A300-600 wing so much more efficient than the A300-B4's?

The graph on that page is, in my opinion, for the whole airplane. The wing, on its own, doesn't explain the difference.
Several things explain the progress :
1/- The trailing edge flaps have been heavily modified : single slotted - iso double slotted - and they have been tweaked by increasing the trailing edge curve. That forced a flatter top of the wing, closer to the supercritical airfoil.
I still remember an improvement of 6% in cruise lift coefficient - Cl - and a drag reduction of 5%, so a total of some 11% improvement... Plus the tip fences

2/- the overall drag had been reduced with A310 aerodynamics : improvement of the lower fuselage, aft of the wing ( more rounded, allowing a longer inner cabin )... The adoption of the A310 tail, much smaller than the A300B-4, further improved the drag.

3/- A small lengthening of the fuselage - some 50 cm - mainly for a better yaw moment from the smaller tailplane in fact lowered the overall drag even more.

It is to be noted that with the same wing geometrical dimensions, the MTOW went from 137 t for the B-100 to 170.5 for the -600... quite a feat for the time.

That example proves, if necessary, that seemingly minor improvements could have some tremendous effects... so I guess you were not OT   

Regards
Contrail designer
 
A342
Posts: 4017
Joined: Sun Jul 31, 2005 11:05 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 24, 2015 10:17 pm

Quoting Pihero (Reply 20):

Thanks for your informative reply!
Exceptions confirm the rule.
 
prebennorholm
Posts: 7128
Joined: Tue Mar 21, 2000 6:25 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Sat Jul 25, 2015 1:34 am

Quoting Matt6461 (Reply 10):
One way to do this is to increase wing twist. The wing always flies at the same angle of attack for max L/D, so what that twist does in cruise is lower the fuselage angle of attack - thereby lowering its lift.

It is exactly the opposite. You obviously mix up wing twist and wing to fuselage incidence. If only Airbus had used the proper name - washout - instead of wing twist, then that misunderstanding would surely have been avoided.

Quoting Matt6461 (Reply 10):
it's the fuselage AoA, not the wing's that is changed.

The wing was indeed changed - increased washout. With unchanged incidence the result is a very slightly increased fuselage AoA.

But the improved cruise performance had very little with fuselage AoA to do, if at all. It changed the spanwise aerodynamic load distribution on the wing, slightly more load near the root and less at the tip.

The result was slightly increased wing drag near the root, and decreased drag at the tip, and less violent tip vortices.

We must believe Airbus when they tell that the overall result was increased cruise performance. Washout is always a compromise, and hopefully they settled at a slightly supperior compromise.
Always keep your number of landings equal to your number of take-offs
 
Max Q
Posts: 8634
Joined: Wed May 09, 2001 12:40 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Sat Jul 25, 2015 8:55 am

I hope AB goes ahead with the NEO.


But the only chance for commercial success is an all out effort, ie the originally envisioned stretch (no half measures) maximum aerodynamic and engine upgrades.

They need to be looking 50-60 years out.


Otherwise it's not worth it.
The best contribution to safety is a competent Pilot.


GGg
 
User avatar
seahawk
Posts: 9865
Joined: Fri May 27, 2005 1:29 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Sat Jul 25, 2015 10:57 am

And that is why a limited effort makes more sense now, because by 2025 new engines will add 5-12% extra. (it depends on what engine they would use now - 5% would be compared to a full new RR Advance engine, 12% would probably be compared to an existing engine like Trent 10)

But the Advance engine won´t be ready before 2025 the next gen will be ready by 2030.

So imho they could decide to do a modest upgrade gaining up to 10% improvement with an EIS by 2020/2021 and then another up-date with new engines by 2030+ or a bigger update gaining 15% by 2025/26.
 
User avatar
speedbored
Posts: 2230
Joined: Fri Jul 19, 2013 5:14 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Sat Jul 25, 2015 11:43 am

Quoting seahawk (Reply 24):
And that is why a limited effort makes more sense now, because by 2025 new engines will add 5-12% extra

While that is true, it will always be true that waiting longer will enable a greater improvement. The question for Airbus to answer is "how long can we afford to wait?" Given the current A380 order book and order rate, I'm not sure that they will be able to wait much beyond 2020.

Quoting seahawk (Reply 24):
But the Advance engine won´t be ready before 2025 the next gen will be ready by 2030.

RR are saying Advance will be ready to EIS "from the end of this decade" (so 2019 or 2020 depending on how you interpret that), and Ultrafan from 2025:
http://www.rolls-royce.com/customers...ducts/future-products/advance.aspx
http://www.rolls-royce.com/customers...ucts/future-products/ultrafan.aspx

My own suspicion is that we will get a formal announcement soon (Dubai?) for an Advance powered neo with some aero and weight improvements, and possibly a stretch (remaining short of 80m) , to EIS 2020-2021. I'm not sure they would be able to wait much longer than that and still be able to maintain a viable production rate.
 
User avatar
seahawk
Posts: 9865
Joined: Fri May 27, 2005 1:29 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Sat Jul 25, 2015 12:00 pm

Sorry, I mixed up the dates.

However I am a bit sceptical that sending a nEO into production just 4 years before the second gen. GTFs will be ready is not optimal. I´rather do the fuselage, wing and cabin work and maybe a Trent 900 PiP using Advance technology and a NEO with the Ultrafan.
 
A342
Posts: 4017
Joined: Sun Jul 31, 2005 11:05 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Sat Jul 25, 2015 1:27 pm

Quoting seahawk (Reply 26):
However I am a bit sceptical that sending a nEO into production just 4 years before the second gen. GTFs will be ready is not optimal. I´rather do the fuselage, wing and cabin work and maybe a Trent 900 PiP using Advance technology and a NEO with the Ultrafan.

Yes, but in 2030 it's likely that an engine even better than the Ultrafan is going to appear. What are you going to do then?

I say it's time to stop tinkering and do this:

Quoting speedbored (Reply 25):
an Advance powered neo with some aero and weight improvements, and possibly a stretch (remaining short of 80m) , to EIS 2020-2021. I'm not sure they would be able to wait much longer than that and still be able to maintain a viable production rate.

   I'd say the originally envisioned stretch to 79,4 m is still ideal. It stays inside the 80 m box and thus doesn't create major operational headaches.
Plus, who really needs the small stretch pondered by Leahy? Customers are either finding the -800's current capacity to be enough (some maybe more than enough), while especially EK wants as much capacity as possible. So I hope/believe the NEO will come in two lenghts.
Exceptions confirm the rule.
 
Max Q
Posts: 8634
Joined: Wed May 09, 2001 12:40 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Mon Jul 27, 2015 3:45 am

The 747 has had several different generations of engines now.


From the first, quite primitive and cranky JT9D's to the more refined offerings from P&W, GE and RR on later classic and -400 models all the way to todays GEN X on the -8 series.


I don't think AB can wait forever for the ultimate engine, if this program is to endure they need to start developing the NEO stretch with the best of what is available today.


If they can finally inspire some serious sales numbers they can develop even further down the road but they need to get on it today, if this aircraft really does have potential it will be around 40-50 more years.


After all the 747 is still in production forty six years after roll out and I think it will make it to fifty !
The best contribution to safety is a competent Pilot.


GGg
 
User avatar
seahawk
Posts: 9865
Joined: Fri May 27, 2005 1:29 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Mon Jul 27, 2015 5:31 am

Quoting A342 (Reply 27):
Yes, but in 2030 it's likely that an engine even better than the Ultrafan is going to appear. What are you going to do then?

I think a NEO is only worth the effort if the engine brings clearly over 10% better performance. For the advance that will be not easy compared to a PiP2 standard Trent 900.

And I do not see why they should not do what they did with the A320 series. Wing and fuselage up-dates and maybe another engine PiP by 2019/2020 followed by the Ultrafan NEO by 2024/2025.
 
User avatar
DocLightning
Posts: 21968
Joined: Wed Nov 16, 2005 8:51 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Mon Jul 27, 2015 6:06 am

Quoting Pihero (Reply 16):
*- Yes : sharklets à la A350 : the height of the sharklet equals to a virtual half span increase of 60% ... so a two meter high winglet would bring the virtual span to 83 meters, with better wing tip vortices control.

IIRC the A380 wingspan is 79.75 m, so they will have to be very careful about this. Most winglets have an outboard cant to them so that when they are airborne they rotate inward to roughly vertical with the aeroelastic upward bend of the wing. This cannot be done with the A380; the winglet must be almost perfectly vertical (well, canted out no more than 25 cm) when the wing is on the ground, meaning that it will have an inward cant when the aircraft is airborne. My understanding is that an inward-canted winglet will not offer as much efficiency gain and this may destroy the business case for the winglet.

An alternative would be to add a downward winglet. This would rotate outboard when the aircraft takes flight and increase the overall wingspan (same thing the downward wing-like-element on the Split Scimitar and Boeing ATW does) but it would also present risks for ramp rash and allowable roll angle when taking off or landing. A folding wingtip that expands the span past 80 m would also not be allowable unless it was to be deployed after takeoff and stowed just before crossing the threshold on landing. But that would obviate many of the efficiency gains afforded by the wingtip device in the first place.

I suppose Airbus could completely redesign the main wing to shorten the main span so as to be able to add a wingtip extension bringing the span back to 79.75 m. That would improve efficiency by allowing a smaller, lighter wing to do the same job (especially because the wing is way overbuilt for the A388; they had been planning on an A38J). But a complete relofting of the A380 wing would be a massive (expensive) undertaking.

More likely, they will do some mild recontouring of the airfoil in problematic places. They might also introduce differential flaps and drooping spoilers that close the spoiler-flap gap like they do on the A350 and 787. And if they could figure out a way to go from three to two ailerons, that might also help the overall weight and mechanical complexity of the wing.
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
-Carl Sagan
 
User avatar
speedbored
Posts: 2230
Joined: Fri Jul 19, 2013 5:14 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Mon Jul 27, 2015 7:34 am

Quoting seahawk (Reply 29):
followed by the Ultrafan NEO by 2024/2025.

While that would be great to see, I just don't think it is realistically going to happen in anything near that sort of timeframe.

While RR have said that the Ultrafan should be ready to EIS around 2025, they have also said that this will be in the narrowbody thrust range. Given the enormous challenges inherent in producing high speed, high power gearboxes with the sort of reliability, and maintenance costs/intervals required for commercial aviation, I just can't see RR wanting to risk scaling the Ultrafan up to widebody thrust ranges, until they have gained a good few years experience in the field with it. I doubt we'll see a widebody Ultrafan engine until 2030 at the very earliest.

PW, on the other hand, with their narrowbody head-start, might just come up with something before then.  
Quoting DocLightning (Reply 30):

That pretty much sums up my own opinion on potential wing changes. The 80m box constraint, and potential cost of any major changes to structure, suggest to me that changes to the wing will be mostly tweaking of various wing devices, maybe some structural weight reduction, and software enhancements.
 
User avatar
seahawk
Posts: 9865
Joined: Fri May 27, 2005 1:29 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Mon Jul 27, 2015 7:55 am

Good point about the risk of starting a GTF with the high thrust version needed for the A380.
 
mjoelnir
Posts: 9411
Joined: Sun Feb 03, 2013 11:06 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Mon Jul 27, 2015 11:01 am

Quoting Pihero (Reply 16):
*- Yes : sharklets à la A350 : the height of the sharklet equals to a virtual half span increase of 60% ... so a two meter high winglet would bring the virtual span to 83 meters, with better wing tip vortices control.

The A350 has 2.4 m high sharklets, I would expect something near to 5m for the A380.

Quoting DocLightning (Reply 30):

The 79.75 wing span is including the current wing tip devices. If the wing tips are redesigned you could move the starting point of the winglet inside. As the aim of the winglets would be drag reduction not increased lift, a nearly vertical version could do the work. The effective increased span working for the drag reduction is not depending only on the angle of the winglet.
Vertical winglets have been working well on diverse designs. Adding downward winglets reduces the torsional moment on the wing. Winglets are are a very difficile design, it is not an obvious simple calculation and small changes can have big effects. Design is still dependent on a lot of wind tunnel work.
 
User avatar
DocLightning
Posts: 21968
Joined: Wed Nov 16, 2005 8:51 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Mon Jul 27, 2015 3:06 pm

Quoting mjoelnir (Reply 33):
As the aim of the winglets would be drag reduction not increased lift, a nearly vertical version could do the work.

  

In this context, the reduction of induced drag also implies increased lift. Fundamentally, any wingtip device reduces the field of vorticity that forms as the air travels over the wing. This field of vorticity introduces a downwash such that any three-dimensional wing flies through a downwash of its own making. This reduces the effective AOA and thus the lift. Wingtip devices increase the lift the wing can produce at a given AOA.



On the A380 wingtip, we see that the very most outboard section has what looks to me like a blunter leading edge than the main wing and a radical increase in sweep. The blunter airfoil would prevent separation and buffet at high AOA and the high sweep would reduce the local mach number in cruise and reduce shock formation from the blunt leading edge. Thus, there is an element of a raked tip on the outboard section of the A380. The downward wing-like element does protrude outward a little bit from the looks of this image. If Airbus chopped off the wing just outboard of the wingtip strobe and then introduced a blended upwards wing-like element, they might be able to cant it outwards enough that it would be vertical in flight. The question is whether this would provide them enough room to do this with a winglet of any meaningful size. The transition from horizontal wing to vertical winglet would need to have a pretty small radius, too, and that would introduce a vortex at the interface that might erase any gains in overall efficiency. Then again, a sharp transition was successful on the A330/A340 and 747. But even on those models, there is a good outboard cant to the winglet such that it becomes more vertical in flight:

View Large View Medium
Click here for bigger photo!

Photo © Daniel Werner

-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
-Carl Sagan
 
User avatar
AirlineCritic
Posts: 1774
Joined: Sat Mar 14, 2009 1:07 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Mon Jul 27, 2015 7:14 pm

Quoting Pihero (Reply 16):
Quoting airmagnac (Reply 17):

Awesome, informative posts. As always. Thanks guys.
 
mjoelnir
Posts: 9411
Joined: Sun Feb 03, 2013 11:06 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Mon Jul 27, 2015 7:48 pm

Quoting DocLightning (Reply 34):

My statement was that the AIM or objective is drag reduction not lift, as the wings have enough lift as it is.
Even if any better winglet brings some lift, it makes a difference for what you optimize.
There are near vertical winglets, you see it on a C17, on various Rutan designed smaller frames, on a Beach Starship and others. There are aerodynamically quite effective.
Airbus could also look at spiroid winglets, Aviation Partners is claiming 11% drag reduction for such winglets, or some other form turned back on itself. The patent of the spiroid winglet is from 1992.

The possibilities are quite broad.
 
User avatar
DocLightning
Posts: 21968
Joined: Wed Nov 16, 2005 8:51 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Tue Jul 28, 2015 5:35 am

Quoting mjoelnir (Reply 36):
My statement was that the AIM or objective is drag reduction not lift, as the wings have enough lift as it is.

And I am saying there is no difference. A new A380 wing would produce the same lift at less AOA (which is the same as "more lift at the same AOA"), which would mean less induced drag.
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
-Carl Sagan
 
Pihero
Posts: 4318
Joined: Mon Jan 31, 2005 5:11 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Tue Jul 28, 2015 10:11 am

Quoting DocLightning (Reply 34):
Wingtip devices increase the lift the wing can produce at a given AOA.

  

Quoting DocLightning (Reply 34):
. If Airbus chopped off the wing just outboard of the wingtip strobe and then introduced a blended upwards wing-like element, they might be able to cant it outwards enough that it would be vertical in flight.

One of the problems any modification to this wing will encounter is that it is a lot stiffer than the *new gen* carbon fibre wing one sees on the 787 or the 350... Very difficult to cant those winglets to the vertical.

See


View Large View Medium
Click here for bigger photo!

Photo © Luca Carminati - Malpensa Spotters Group
View Large View Medium
Click here for bigger photo!

Photo © Paul McCarthy



To fit inside the 80m box, there is only a length of some 25 cm to add to each wing ( that's just ten inches ! ) to play with.
But then, there are the outboard aileron to cope with, and even worse, the outboard slat., whicxh ends right at the bend of the wingtip (just at the landing light in your previous picture.
Could Airbus modify these flight controls is the big question ( I mean in terms of costs of modification / certification ).
Contrail designer
 
tommy1808
Posts: 13980
Joined: Thu Nov 21, 2013 3:24 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Tue Jul 28, 2015 10:58 am

Quoting Pihero (Reply 38):
One of the problems any modification to this wing will encounter is that it is a lot stiffer than the *new gen* carbon fibre wing one sees on the 787 or the 350... Very difficult to cant those winglets to the vertical.

Maybe I habe an error in my thinking, but shouldn't the stiffer wing make it easier since the on ground/in flight positions are much closer to each other?

Maybe there is an aerolastic solution to the problem that has a flexible wingtip device bent outwards with flight loadings?

Best regards
Thomas
Well, there is prophecy in the bible after all: 2 Timothy 3:1-6
 
User avatar
DocLightning
Posts: 21968
Joined: Wed Nov 16, 2005 8:51 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Wed Jul 29, 2015 5:39 am

Quoting Pihero (Reply 38):
    

Coming from you, that little checkmark was one of the best stamps of approval I've ever received. Thanks!   

Quoting Pihero (Reply 38):
To fit inside the 80m box, there is only a length of some 25 cm to add to each wing ( that's just ten inches ! ) to play with.

It's worse than that. 25 cm TOTAL, IIRC. 12.5 cm each wing. Total span is 79.75 m (some sources say 79.85 m, which is even worse).

Quoting Pihero (Reply 38):
One of the problems any modification to this wing will encounter is that it is a lot stiffer than the *new gen* carbon fibre wing one sees on the 787 or the 350...

No, but it does flex a lot, mostly the outer 2/3 of the span. The wingtips probably swing through an arc of at least 5°, maybe 10°.


View Large View Medium
Click here for bigger photo!

Photo © Jerome Mervelet
View Large View Medium
Click here for bigger photo!

Photo © Johannes Klinghardt

Quoting Pihero (Reply 38):
But then, there are the outboard aileron to cope with, and even worse, the outboard slat., whicxh ends right at the bend of the wingtip (just at the landing light in your previous picture.
Could Airbus modify these flight controls is the big question ( I mean in terms of costs of modification / certification ).

If they are going to modify the wingtip, it won't be cost-effective to alter the aileron or slat. The light might be moveable outboard or contoured into a blended sweep without a major redesign (it is neither structural nor does it significantly alter aerodynamics) but that's it. Any modification other than that is going to be a show-stopper. Might as well just clean-sheet a whole new wing at that point.

Quoting tommy1808 (Reply 39):
Maybe there is an aerolastic solution to the problem that has a flexible wingtip device bent outwards with flight loadings?

The only solution that exists is a downward-pointing wing-like element. Basically an upside-down winglet. This would rotate outward on wing flexion and increase the total span. The trouble is reduced ground clearance and increase risk of contact with ground vehicles ("ramp rash")
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
-Carl Sagan
 
Pihero
Posts: 4318
Joined: Mon Jan 31, 2005 5:11 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Wed Jul 29, 2015 11:28 am

Quoting DocLightning (Reply 40):
f they are going to modify the wingtip, it won't be cost-effective to alter the aileron or slat. The light might be moveable outboard or contoured into a blended sweep without a major redesign (it is neither structural nor does it significantly alter aerodynamics) but that's it

  
Plus : That wing is very busy and between the slats and ailerons outer limits, I just don't see where the winglet could start.
So, to me it's down to a cruise-adaptable wing / slat / aileron solution... which could in fact be very interesting.... unless, of course they did away with the outboard slat.
That would, at the cost of a few Vref knots, improve the overall efficiency of that geometry.

The origin of this thread is a basic misconception : that the A380 wing is inefficient, because its aspect ratio doesn't conform to the aerodynamics of the 787, A350 or the 777X.
In my opinion, it's a red herring : The sweep is the most important of all the long-haulers ==> better trans-sonic qualities with an aspect ratio increase.... noit even counting the influence of the area-ruled fairing and the influence opf the whole aircraft aerodynamics ( the size of the tailplane is also a sign ).
Contrail designer
 
User avatar
Matt6461
Topic Author
Posts: 2991
Joined: Wed Oct 16, 2013 9:36 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Thu Jul 30, 2015 2:37 pm

Greeting from a hinterland of Southeast Asia, to which exigent circumstances have brought me via 77W and various older technologies, and which has separated me for a while from reliable internet service (and ant-free accomodations, air conditioning, among other things).

You all are right about the wing twist, I was wrong. I was indeed thinking angle of incidence at fuselage join. Now I've learned something about wash-out/in, thanks.

Re fuselage lift - still not sure about the point in dispute, which I define in a much narrower sense than some of you perhaps. I get that it's a factor and is unavoidable etc., should be used when there.

BUT - if the fuse's lift produces, say, 10x the induced drag of the wing per unit of lift, it seems better to add a few extra tons of wing than to chase fuse lift. Even 10% more wing seems better, rather than 10x induced drag. Again, this is assuming a "tube-wing" plane, not a different design.

Quoting Pihero (Reply 38):
To fit inside the 80m box, there is only a length of some 25 cm to add to each wing ( that's just ten inches ! ) to play with.

If you're keeping the current wing, wouldn't it make sense to shave nominal (pre-winglet) span by a foot or so to achieve greater effective span?

Quoting airmagnac (Reply 17):
Now as for your Excel, I've just taken a quick look. But it's really difficult to understand anything....I take it you are not an Excel expert !

Nope! I never use it professionally except to send numbers to my accountant, who then makes my garble much better.

Quoting airmagnac (Reply 17):
At the aerospace level, the "volume" of the model is...well, small. I' ve just produced about 5 times worth of Excel data to assess the weight & costs of a few cables, ducts and pipes

It's intentionally "low volume." All it's supposed to do is give forumers a quick and easy estimate of relative drag parameters based on span, weight, and wetted area. This is, as you point out and I've said all along, far from a detailed picture. But I'm not going for a detailed picture. I'm going for a very basic tool that would avoid discussions like I've had in the past (with very well-respected members) where we're doing arithmetic with words.

Quoting Pihero (Reply 16):
Contrarily to what you're thinking, that wing's performance equals or exceeds anything built before it

Look I'm not going to dispute that you seem to know a bit more about aerodynamics than me. Great, that's why I come here. (and thanks!)

But your assertion has a really big problem: the A380's actual performance. Every analysis of the plane, even those with new RR Advance engines, show it as *less* fuel-efficient per-pax than the 777-9.

http://leehamnews.com/2014/02/03/upd...-a-neo-version-and-whats-involved/
http://leehamnews.com/2014/12/17/a38...ep-analysis-of-its-competitivness/
http://airwaysnews.com/blog/2015/01/...ut-a-business-case-exists-for-neo/

As knowledgeable as you seem to be, I'm also inclined to defer to the judgments of these published analyses, with which the authors have publicly identified themselves and staked their professional reputations.

There must be an explanation for this performance shortfall, and I think we can eliminate the following:

-engines (the linked models assume RR Advance for NEO)
-fuselage (correct me if I'm wrong but it seems that the A380's fuselage has compelling aerodynamic and structural efficiencies over single-deck competition)

If the engines were equal and the fuselage better, the wing is a very good explanation of what is happening here. And not just the wing - also its knock-on effects on engine, empennage, and landing gear size. Leeham says induced drag is 55% of drag for A380, blowing the curve for modern airliners. Leeham blames the low AR wing for the fuel burn. Ferpe's analysis agrees. My counting ability tells me that its low AR is an anomaly among its contemporaries. If that's Mickey Mouse aerodynamics, I'm at least in good company.

Quoting Pihero (Reply 41):
The origin of this thread is a basic misconception : that the A380 wing is inefficient, because its aspect ratio doesn't conform to the aerodynamics of the 787, A350 or the 777X.
In my opinion, it's a red herring : The sweep is the most important of all the long-haulers ==> better trans-sonic qualities with an aspect ratio increase

The trend in modern widebodies has been towards lower sweep angle. As I understand, this is one of the benefits of supercritical airfoils - less sweep needed to achieve desired Mdd. Sweep has some effect on induced drag via the "span efficiency" term, but for all non-gate-constrained aircraft, designers have judged the tradeoff to favor less sweep and higher AR.

Re transonic qualities I have read that this is true of A380 as well: very good in that department. But AFAIK form/parasitic+induced drag is typically ~90% of drag, transonic properties wouldn't make up even 10% (interference, fuselage upsweep, trim, etc. also factor in the remainder).

So as I've said repeatedly I'm not saying "Those Europeans can't design a wing." They did a great job within the constraints they faced, but the constraints were too much to give us a plane that anybody besides EK wants. It may have been that no technical solution was possible to give us a great-selling VLA. In which case the A380 shouldn't have been launched. If it wasn't going to beat smaller competition dramatically, it wasn't going to sell, hasn't sold, and won't sell. (...well enough to justify a program)

But if there's a technical solution that can give us a great VLA now...

Quoting Pihero (Reply 16):
*- I personally do not agree / believe in folding wig tips : weight, structural weight augmentation and discontinuity in the wing at cruise ( aeroelasticity ) and with high lift devices extended.

Again I'm sure you have reasons for this personal belief. But I'm sure Boeing has a couple smart folks who pondered the tradeoffs before betting $5bn on the folding wing. Boeing expects only ~800lb weight delta from folding wing. It won't effect the portions on which high lift devices are or would be placed, it seems.

Could you say more about the aeroelastic impacts?

[Edited 2015-07-30 07:41:47]
 
User avatar
Matt6461
Topic Author
Posts: 2991
Joined: Wed Oct 16, 2013 9:36 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Thu Jul 30, 2015 3:38 pm

Quoting Pihero (Reply 41):
the size of the tailplane is also a sign

This is another remark that I don't get. I mean that simply: what do you mean?

Isn't it a disadvantage, ceteris paribus, to carry and drag a huge tailplane? Don't designers try to minimize empennage weight and area? Isn't one of the biggest benefits of a BWB the omission of the empennage?

Quote:
The Blended-Wing-Body (BWB) concept has shown substantial performance
benefits over conventional aircraft configuration with part of the benefit being
derived from the absence of a conventional empennage arrangement.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090007702.pdf

One of the biggest benefits of a rewing, imj, is its synergy with a smaller empennage and engines. (Also other elements - e.g. landing gear and fuse stringer gauge - if you want to go that far). Maybe I'm off in thinking so, but... why? As long as the tailplane creates adequate maneuver force and efficiently provides trim stability, shouldn't it be as small/light as possible?
 
mjoelnir
Posts: 9411
Joined: Sun Feb 03, 2013 11:06 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Thu Jul 30, 2015 6:06 pm

Quoting Matt6461 (Reply 42):
Re fuselage lift - still not sure about the point in dispute, which I define in a much narrower sense than some of you perhaps. I get that it's a factor and is unavoidable etc., should be used when there.

BUT - if the fuse's lift produces, say, 10x the induced drag of the wing per unit of lift, it seems better to add a few extra tons of wing than to chase fuse lift. Even 10% more wing seems better, rather than 10x induced drag. Again, this is assuming a "tube-wing" plane, not a different design.

The dispute is very simple, you decided that fuselage lift was something bad, something to avoid.

The main point you get wrong is comparing the fuselage lift to wing designs. The question is rather how much does the drag of the fuselage increase if the fuselage produces less or more lift. As nearly all new designed fuselages are rather producing more lift than twenty years older designs, even wing fairings are designed for lift, you perhaps should leave your textbooks alone and think why that is so.
 
User avatar
airmagnac
Posts: 451
Joined: Wed Apr 18, 2012 10:24 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 31, 2015 12:26 pm

Quoting Matt6461 (Reply 42):
All it's supposed to do is give forumers a quick and easy estimate of relative drag parameters based on span, weight, and wetted area. This is, as you point out and I've said all along, far from a detailed picture

The intent is noted and understood, no worry. I just have an issue with the execution.

You are choosing a priori which parameters you want to study, generally because
a/ you have a text book formula to derive them, or
b/ it goes in the general direction of your arguments

But an aircraft is too complex a system, with too many interdependancies, to proceed like that. You actually need to go down to some level of detail to understand those interdependencies, and undertsand how all relevant parameters affect each other in all operational cases. Only then can you identify the main driving parameters of your business case, and clean up your model to focus only on those drivers.

Just to pick up on the BWB you mention : that concept is often touted as "the optimum arcraft design". But that's only true if you look at structure weight and L/D exclusively, in isolation of all other design parameters.
In the real world you'll need to take into account total weight, total development costs, total manufacturing costs, maintenance costs, infrastructure costs, and those would be related to : loads distribution, control & stability, aircraft survivability requirements (uncontained engine failure, wheel burst, etc), evacuation requirements, reliability/ETOPS, maintainability, serviceability (load/unload the passengers/cargo, food etc...), compatibility with existing ground infrastructure (taxiway/runway loading, boarding bridges, etc...), visibility for the pilots, manufacturability & assembly, system complexity and impacts on production testing volumes (& costs) and operational reliability, disassembly at end of life, noise, system installation constraints (for example length limits due to voltage drop in electrical wires, pressure drop in ducts, latency times for data communication, etc...), ability to design & test (if aerodynamics are too complicated for either CFD or wind tunnels, you're stuck), pressure and temperature control, etc etc....and that is a non exhaustive list.

If you look at all those things together, a BWB may not be such an optimum solution. The weight gains linked to pure aerodynamic considerations may be cancelled out by overall heavier system installation. Or a less efficient cabin layout. Or additionnal strcutural shielding to protect sensitive areas against engine bursts.

Other example : the fabulous "bleedless" aircraft. Get rid of all those big hot bleed pipes, and save space, weight and maintenance needs...hurray ! Those will all be replaced by electrical wires, which are small, flexible, easier to install, ie much lighter.
Except that in the end, for electro-magnetic issues those small wires have to be big heavily protected electrical harnesses which weigh just as much as ducts. They are connected to heavy power electronics, which require a heavy & complex cooling system to manage the heat losses. Those may be much lower than with a bleed design, but they are now trapped deep within the fuselage and must be evacuated somehow.
End result : hardly any gains. Luckily no significant losses either, it seems. But the end result is very different from the first "simple" analysis, just because that analysis only looked at the convenient part of the picture and ignored the rest.

Quoting Matt6461 (Reply 43):
One of the biggest benefits of a rewing, imj, is its synergy with a smaller empennage and engines. (Also other elements - e.g. landing gear and fuse stringer gauge - if you want to go that far). Maybe I'm off in thinking so, but... why? As long as the tailplane creates adequate maneuver force and efficiently provides trim stability, shouldn't it be as small/light as possible?

  

A rewing capitalizes N years of progress in aerostructure design and manufacturing to reduce manufacturing costs, fuel costs and maintenance costs. Yet avoids a full redesign of the complex (expensive) fuselage with all its complex systems, structural maintenance & repair needs, crew & passenger constraints, etc...
IOW it' should have a better value/cost relation than a full aircraft redesign.
If you try to chase only aerostructure weight and L/D, as you suggest, it would indeed be interesting to go for empennage and gear redesign. But the little benefits from those changes would likely be outweighed by the redesign costs, and costs of the impacts on the manufacturing and maintenance infrastructures.
So your business case would rapidly degrade in the real world, but by focusing on structural weight and L/D you'd likely miss that.
My goal as an engineer is to fill my soul with coffee and become immortal
 
User avatar
seahawk
Posts: 9865
Joined: Fri May 27, 2005 1:29 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 31, 2015 12:42 pm

Quoting airmagnac (Reply 45):
A rewing capitalizes N years of progress in aerostructure design and manufacturing to reduce manufacturing costs, fuel costs and maintenance costs. Yet avoids a full redesign of the complex (expensive) fuselage with all its complex systems, structural maintenance & repair needs, crew & passenger constraints, etc...
IOW it' should have a better value/cost relation than a full aircraft redesign.
If you try to chase only aerostructure weight and L/D, as you suggest, it would indeed be interesting to go for empennage and gear redesign. But the little benefits from those changes would likely be outweighed by the redesign costs, and costs of the impacts on the manufacturing and maintenance infrastructures.
So your business case would rapidly degrade in the real world, but by focusing on structural weight and L/D you'd likely miss that.

Or worst case, you optimize completely for the 800 size and the VLA market picks up with customers asking for a stretch. The -850 idea has way more merit imho.
 
Pihero
Posts: 4318
Joined: Mon Jan 31, 2005 5:11 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Fri Jul 31, 2015 10:21 pm

Quoting airmagnac (Reply 45):

As usual a weel written and informative post.

Many thanks.

Quoting Matt6461 (Reply 43):

Quoting Pihero (Reply 41):
the size of the tailplane is also a sign

This is another remark that I don't get. I mean that simply: what do you mean?

Sorry. Wrote as usual too fast : The A380 tailplane is much smaller than initially thought, which participates in the overall efficiency of the airplane.

Quoting Matt6461 (Reply 42):
The trend in modern widebodies has been towards lower sweep angle. As I understand, this is one of the benefits of supercritical airfoils - less sweep needed to achieve desired Mdd.

Problem is aerodynamics are not exactly an à-la-mode fashion design ( long skirts : short skirts etc...) and designers would try to use all the tricks in their bags to achieve maximum efficiency. Sweep angle is one

Quoting Matt6461 (Reply 42):
if the fuse's lift produces, say, 10x the induced drag of the wing per unit of lift, it seems better to add a few extra tons of wing than to chase fuse lift.
Quoting Matt6461 (Reply 42):
Now I've learned something about wash-out/in, thanks.

You might add that washout as a generic term also includes the gradual change of airfoil along the wing span : it's sometimes called *evolutive airfoil*

Quoting Matt6461 (Reply 42):
If you're keeping the current wing, wouldn't it make sense to shave nominal (pre-winglet) span by a foot or so to achieve greater effective span?

Seems very difficult without changing the slats and ailerons configuration.

Quoting Matt6461 (Reply 42):
Every analysis of the plane, even those with new RR Advance engines, show it as *less* fuel-efficient per-pax than the 777-9.

Those are quite difficult to really measure : Is an A380 with 800 passengers less fuel efficient than a B777 with 400 or 500 ?
Can the engines' progress erase that perceived superiority ?

What I know is that a wing has to perform as efficiently as can be designed in all flight regimes AND still conform to increasing requirements in terms of noise, wake... etc... and be as easy to slot into the normal airport traffic with the least disturbance possible.
In these respects, the A380 is in the same approach category - C - as smaller jets ( the 737s and 320s ), meaning its approach speed is the lowest of the existing long haulers and its noise print would allow it night ops in the most demanding airports.

*As an aside, the A350, which conforms to *modern high aspect ratio wing* achieves the same performance... not really better... and that after another ten more years of progress in aerodynamics .

Quoting Matt6461 (Reply 42):
I'm sure Boeing has a couple smart folks who pondered the tradeoffs before betting $5bn on the folding wing

Me, I'm just someone with a passion for anything related to airplanes... which means that I can marvel at some elegant solutions that crack engineers have thought of and brought to the world... I'm expecting with baited breath to see how the 777x new wing adjunct will blend into the existing one : will the result be a stiffer new wing or will we see a kink in the dihedral at cruising Mach ?
Contrail designer
 
User avatar
Matt6461
Topic Author
Posts: 2991
Joined: Wed Oct 16, 2013 9:36 pm

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Sun Aug 02, 2015 4:19 pm

Quoting airmagnac (Reply 45):
But an aircraft is too complex a system, with too many interdependancies, to proceed like that. You actually need to go down to some level of detail to understand those interdependencies, and undertsand how all relevant parameters affect each other in all operational cases. Only then can you identify the main driving parameters of your business case, and clean up your model to focus only on those drivers.

I have very clearly identified the main driving factors of the business case: (1) operating economics of the plane, of which CASM gives a pretty good picture, and (2) production cost of the plane. I have used publicly available data to break out A380 operating costs by category. I have put forward parameters for production costs. You have no specific objections to these figures, other than as they relate to fuel burn and aerodynamics. That's fine to point out, but where I'm showing a 20% CASM improvement versus 7% for the NEO, there is plenty of room for the fuel burn term to be in error, while my basic thesis remains true: a rewing is a better than a NEO.

There are interdependencies, sure. But in which way do these point? For or against the basic thesis? You don't dispute that a longer, lighter wing would give better fuel performance.

Quoting airmagnac (Reply 45):
Just to pick up on the BWB you mention

I'm not favoring a BWB. Pressurization and evacuation alone seem insuperable under current technology.

Quoting airmagnac (Reply 45):
If you try to chase only aerostructure weight and L/D, as you suggest, it would indeed be interesting to go for empennage and gear redesign. But the little benefits from those changes would likely be outweighed by the redesign costs, and costs of the impacts on the manufacturing and maintenance infrastructures.
So your business case would rapidly degrade in the real world, but by focusing on structural weight and L/D you'd likely miss that.

Again you're just stating generalities. I have provided estimates of the impact of empennage changes, you don't do so. The benefits are potentially not "little" because they interact synergistically with new wing and engines to create exponential benefits.

You argue that the business case would "rapidly degrade" but provide zero numbers for why this is so. The degradation of the business case is a matter of development cost. I use $4bn in the version I posted, but even $6bn would still have provided a higher ROI than a NEO. You're not pointing out something I missed, you're just not engaging with any numbers. It's all generalities and obfuscation.

Quoting seahawk (Reply 46):
Or worst case, you optimize completely for the 800 size and the VLA market picks up with customers asking for a stretch. The -850 idea has way more merit imho.

Seriously? That's the worst case? First of all this seems enormously unlikely.

Second, if customers were asking for a stretch - too bad. What are they going to do, convince Boeing to build a rival VLA? No chance of that. No, customers who want an -850 size aircraft will simply have to buy the -800. Just as EK does today.

Quoting Pihero (Reply 47):
The A380 tailplane is much smaller than initially thought, which participates in the overall efficiency of the airplane.

The tailplane is huge though and disproportionate in size to passengers carried. That it is smaller than initially expected is entirely irrelevant - it's still a big heavy piece of structure that contributes to the A380's lackluster performance.

Quoting Pihero (Reply 47):
Problem is aerodynamics are not exactly an à-la-mode fashion design ( long skirts : short skirts etc...) and designers would try to use all the tricks in their bags to achieve maximum efficiency. Sweep angle is one

Like Airmagnac, you're giving generalities that might sound smart but have little actual content. Of course designers will try "all the tricks," but the best trick is the optimal design. Greater-than-prevailing sweep is not optimal except for a gate-constrained aircraft. The 747 has more sweep than A380, for example, but not because it's an optimal design.

Quoting Pihero (Reply 47):
Those are quite difficult to really measure : Is an A380 with 800 passengers less fuel efficient than a B777 with 400 or 500 ?

This is a dodge of my challenge to your thesis. Instead of confronting the fact that the A380 is not fuel-efficient for its size, you obfuscate by playing with passenger numbers. The A380 has about 52% more floor area than the 777-9. That's a physical fact that can't be avoided and seat numbers should roughly follow that 52%. In fact, because the A380's seating is more generous at ten-abreast, it should contain fewer than 52% more seats.

Quoting Pihero (Reply 47):
and be as easy to slot into the normal airport traffic with the least disturbance possible.
In these respects, the A380 is in the same approach category - C - as smaller jets ( the 737s and 320s ), meaning its approach speed is the lowest of the existing long haulers and its noise print would allow it night ops in the most demanding airports.

You focus on approach speed category but ignore wake separation, which certainly contravenes your "least disturbance possible" dictum. A new wing and MTOW reduction would greatly improve the wake separation problem - wake vortices are directly related to induced drag.

And which operators really bought the A380 because of its approach speed? I have never heard of anyone saying so. A380 has a QC1 weight variant, but has anybody purchased it?

Like a lot of what you're saying, this another example of selective nitpicking to avoid really grappling with my central argument: That the NEO isn't enough of an efficiency jump to make the A380 more broadly attractive, but that a rewinged A380 could be broadly attractive.

Quoting Pihero (Reply 47):
*As an aside, the A350, which conforms to *modern high aspect ratio wing* achieves the same performance... not really better... and that after another ten more years of progress in aerodynamics .

Does "same performance" mean "same approach speed?" I mean who cares in the end? The 77W is pretty bad on that metric and is one of the most successful planes ever. If "same performance" means same overall efficiency that's just wrong. The A350 has better L/D than A380, despite the A380 having a much more aerodynamically efficient fuselage.

You and Airmagnac may have a lot of knowledge and a lot to say, but you're missing the forest for the trees. You're obfuscating the central issue of whether a simple NEO will make the A380 attractive; you're avoiding any discussion of what efficiency improvement is required; you're not providing any proposals yourself.

[Edited 2015-08-02 10:12:42]
 
User avatar
speedbored
Posts: 2230
Joined: Fri Jul 19, 2013 5:14 am

RE: A380NEO: Revisions And BizCase Unclear,2020-25EIS

Sun Aug 02, 2015 7:19 pm

Quoting Matt6461 (Reply 48):
I have very clearly identified the main driving factors of the business case: (1) operating economics of the plane, of which CASM gives a pretty good picture, and (2) production cost of the plane.

No, you have not identified that these are the main drivers, you have guessed. As airmagnac has already pointed out, the drivers of a business case are far more complex than that.

Quoting Matt6461 (Reply 48):
You're not pointing out something I missed, you're just not engaging with any numbers. It's all generalities and obfuscation.

He is pointing out something you missed - all of the detail that is required if you are to make any sensible comparisons.

You are massively oversimplifying everything, making far too many assumptions and guesses, and coming up with answers that are completely unrelated to the reality that is today's aviation business. You can't treat the real world like a school project and hope to come up with commercial reality.

I suspect that the main reason why people are not "engaging with numbers" is because to do so on a meaningful basis requires access to a lot of commercially confidential information, and a whole load of time.

Quoting Matt6461 (Reply 48):
You and Airmagnac may have a lot of knowledge and a lot to say, but you're missing the forest for the trees. You're obfuscating the central issue of whether a simple NEO will make the A380 attractive; you're avoiding any discussion of what efficiency improvement is required; you're not providing any proposals yourself.

See above. I also suspect that they are missing your "forest" because it hasn't got past the acorns stage yet.

I am almost beginning to admire your determination that, having read a few books and articles, you know better than the many people with so many years of experience in the field who keep pointing out the flaws in your arguments. I suspect that you will make a very successful politician one day.

Who is online

Users browsing this forum: 738Pilot, Google [Bot], SAAFNAV and 14 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos