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zeke
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 9:14 am

Quoting AeroPiggot (Reply 45):
ICAO all are collaborating on the certification and rule making process

Thats not my understanding of what ICAO is, they are an international organisation without any legal frameowrk behind them like EASA, FAA, Eurocontrol to create "rules" or to "certify" any aircarft.

I will be interested when/if this reports exists and when/if its made public, if it is what was stated in the start of the thread, or an adoption of recommendations from EASA, FAA, Eurocontrol and Airbus.
 
MarshalN
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 9:19 am

Quoting Glideslope (Reply 47):
Why is this news????? Did people ACTUALLY believe Airbus' claims!!!!

This is just the tip of the 380 iceberg. Sit back and watch all the other John Leahy style predictions become the fairy dust that they are.

Man, they should have learned from the 346 experience. Too bad really.

I'm impressed it took 47 posts before a real "I told you so, Airbus always sucks" post to show up.

This is indeed a problem for Airbus though. I wonder if a quick fix is even possible -- but like a number of you have said, perhaps this is an initial guideline that will be refined over time? After all, we're still a year away from EIS
 
ContnlEliteCMH
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 9:29 am

Quoting Cloudyapple (Reply 2):
A lot worse than our predictions but not unexpected.

Don't predictions = expectations? They do in my line of work. If I tell my client that his MOLAP database can process 15 MB/sec, and it actually processes only 5 MB/sec, I don't say "but not unexpected." As Ricky Ricardo would say, "I got some 'splainin' to do." I guess that's why I'm careful to avoid predictions until I have some real data...

Quoting MD80fanatic (Reply 4):
Big plane = Big wake .... it's physics.

Yes, but only partly. Fluid mechanics is, ah, complicated. I wonder what Airbus thought would cause a plane weighing nearly 50% more than the 747 to have a similar wake?

Quoting A350 (Reply 21):
I fail to understand how so large differences between wind tunnel experiments and reality can occur. Sure, the wind tunnel experiment is a scaled down model, but I'm convinced they have done a decent work at it.

I wonder about this as well. Fluid mechanics is definitely a black art, despite what some on this board postulate, that computational fluid dynamics is mature enough that you shouldn't even need physical testing. But wind tunnel testing is a well-established method. There are millions of wind tunnel hours in the books.

It's like the Hubble debacle. The story has it that the mirror was ground to a perfect QA level -- measured with a faulty QA rig. Makes you wonder...
 
Areopagus
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 9:44 am

Quoting MD80fanatic (Reply 4):
I figured that was the cause of the deformed exhaust trails in the "contrail" pic, posted yesterday, but I did not want to start another war.

I just looked at all the pictures that came up as a result of querying for A380 in the last 7 days, and didn't see any with contrails. Could you (or anyone else) post a reference?

OBTW, the 380 looks very nice in these recent inflight photos. (A normal perspective on a fully assembled and painted, flying aircraft is much nicer than close-up wide-angle distortion of an unpainted prototype with missing pieces.)

Quoting PPVRA (Reply 39):
What about blended wingtips, a la B777?

Given that the A380's wing span is already 79.8m, wingtip treatments that lengthen the span don't seem very likely. That's why A350 suggested 737-style winglets.

Quoting StuckInCA (Reply 29):
Quoting Ikramerica (Reply 27):
Not exactly a great "hub-hub" aircraft if a 50% increase in capacity inside creates a 66% negative impact in capacity on the outside

Isn't what you're implying here only even possibly the case if the only factor in airport capacity were runway slots (Nothing to do with gates, etc)? Is this the case at some or many airports?

I think that's fair to say, but it is a big problem, given that a major justification for buying the 380 is to make more efficient use of precious slots at major hubs.

I sure hope there is a relatively simple technical fix.
 
N79969
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 10:04 am

Have any of the news services or aviation publications wrote about these results?
 
md80fanatic
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 10:15 am

In this image I think you can see where some of the problems are originating from.


View Large View Medium
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Photo © French Frogs AirSlides



The outboard vortex (caused by high pressure air below the wing/slats slipping around the cutout in the slats for the engine pylon), looks pretty consistant and extends beyond the trailing edge...this indicates, at least, pretty laminar flow over the outer portions of the wing.

The inner vortex is ripped apart by the time it gets to mid-wing, this indicates generally turbulent air. This is not really what you want as it decreases the pressure differential above and below the airfoil (lift).

I think if they can calm the flow over this area of the wing....the turbulence in the wake field can be reduced.


Areopagus: The topic containing the contrail photo has slipped off the front page....try the next page. I forgot the thread title. The photo is from another website which is why your search was fruitless.

There is a good shot of a 744 contrail someone posted there....and you can see the forcing apart of the trails (the trails are following the wake profile). You can see the inboard trails are staying consistant as they move below the outboard trails....very little washout of the inner trails.

The A380 smears the inner trails within 1 plane length of distance, which is wierd. It really shouldn't be doing that.

[Edited 2005-11-15 02:21:55]
 
redflyer
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 10:19 am

Quoting Areopagus (Reply 53):
I just looked at all the pictures that came up as a result of querying for A380 in the last 7 days, and didn't see any with contrails. Could you (or anyone else) post a reference?

http://www.planepictures.net/netshow.php?id=413198
 
Areopagus
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 10:25 am

MD80fanatic and RedFlyer: Thank you.
 
TaromA380
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 10:27 am

If the report if official, this is the end of the first A380 legend.

But is it official ?
 
PyroGX41487
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 11:07 am

I hope this doesn't take away from the conversation, but a bit of humor: If one of these things managed to land and take off again at SXM, the beach and all the people on it would be OBLITERATED.
 
boeingbus
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 11:08 am

Quoting Areopagus (Reply 57):
MD80fanatic and RedFlyer: Thank you.

ditto...

I hope this all works out at the end for Airbus. Afterall, Leahey just mentioned the other day or so that the Airbus is meeting all performance targets. We wouldn't want another cover up would we? But again I really hope this all works out at the end. At first I thought the 380 was an ugly duckling. But lately, she is looking real nice.

Cheers,

Ric
 
Jalto27R
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 12:53 pm

Quoting Milan320 (Reply 23):
So what! If it reduces the amount of traffic by taking on more passengers, then that's good. What's one minute anyway? Wink
-Milan320

Yeah, but talk about one big pain in the a$$ for air traffic controllers.

Mike
 
jasond
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 1:01 pm

Quoting N79969 (Reply 5):
What is the sensible and fair way of dealing with that effect?

I guess it will be dealt with like many other things in this industry, some form of compromise between money and safety.
 
abba
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 1:06 pm

Quoting MD80fanatic (Reply 55):
The A380 smears the inner trails within 1 plane length of distance, which is wierd. It really shouldn't be doing that.

MD80fanatic - thank you for a very good and informative post!

How do you interpret that observation? And what do you make of the fact that there seems to be a difference between the right and left inner trails? Could some of be due to test-equipment being fitted?

Abba
 
BG777300ER
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 1:35 pm

Quoting ContnlEliteCMH (Reply 52):
Yes, but only partly. Fluid mechanics is, ah, complicated. I wonder what Airbus thought would cause a plane weighing nearly 50% more than the 747 to have a similar wake?

I saw a show on The Learning Channel that talked about the wake turbulance thing for like 10 minutes. They said that the new "walled" wing tips on the end were the reason. I don't remembe exactly what it was, but since they extended below the wind it made a difference or something....
 
RichardJF
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 1:49 pm

Quoting Cloudyapple (Reply 36):
I suspect 10Nm is a super conservative guideline to start with just to be on the safe side. It should reduce to perhaps heavy +1 or +2 as we collect and analyse actual operational data.

How much of an issue will the cross runways used by much smaller planes such as Dash 8's be at Sydney and Melbourne.
I'm assuming the A380's travelling fast but on the ground are not much of a problem in terms of wake.
 
md80fanatic
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 1:55 pm

The contrail image is with "clean wings" (no flaps/slats deployed)....so what you are seeing is probably the wake field at it's smoothest (this cannot be fixed as it is natural). It's a huge object that displaces a great deal of air.

This is a wild guess....I think the flaps/slats deployed wake turbulence problem is due to two items....first the slats do not extend to the fuselage, making a odd junction that is not necessarily conducive to laminar flows. In fact the entire leading edge is broken up into 6 sections, root to tip.


View Large View Medium
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Photo © Sam Chui



The 747's setup also does not extend to the fuselage but the difference is that the 747 uses a Krueger-type flap as the "slats", which folds out from under the wing (as on the 727)...this leaves the upper surface of the wings consistantly smooth.


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Photo © Dan Valentine

 
iwok
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 3:22 pm

Quoting AeroPiggot (Reply 3):
Very interesting indeed, what happen to the Airbus prediction of vortex strength below the 747 due to exotic control surface manipulations??

CFD is good, but its really a "garbage in-garbage out type of excersize. Your results are only as good as your assumptions, which it appears in this case were faulty (this happens very often  Smile )

Quoting Areopagus (Reply 53):
Given that the A380's wing span is already 79.8m, wingtip treatments that lengthen the span don't seem very likely. That's why A350 suggested 737-style winglets.

I wonder if the 380 will ever get optional fold up wing tips a la 777?

Quoting MD80fanatic (Reply 55):
The outboard vortex (caused by high pressure air below the wing/slats slipping around the cutout in the slats for the engine pylon), looks pretty consistant and extends beyond the trailing edge...this indicates, at least, pretty laminar flow over the outer portions of the wing.

The inner vortex is ripped apart by the time it gets to mid-wing, this indicates generally turbulent air. This is not really what you want as it decreases the pressure differential above and below the airfoil (lift).



Quoting MD80fanatic (Reply 66):
The contrail image is with "clean wings" (no flaps/slats deployed)....so what you are seeing is probably the wake field at it's smoothest (this cannot be fixed as it is natural). It's a huge object that displaces a great deal of air.

This is a wild guess....I think the flaps/slats deployed wake turbulence problem is due to two items....first the slats do not extend to the fuselage, making a odd junction that is not necessarily conducive to laminar flows. In fact the entire leading edge is broken up into 6 sections, root to tip.

MD80fanatic, you seem to know what the heck you're talking about. Great post. When I see those pictures, I see a plane taking off. Great analysis!

iwok
 
abba
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 3:47 pm

Quoting MD80fanatic (Reply 66):
This is a wild guess....I think the flaps/slats deployed wake turbulence problem is due to two items....first the slats do not extend to the fuselage, making a odd junction that is not necessarily conducive to laminar flows. In fact the entire leading edge is broken up into 6 sections, root to tip.

Thank you again! The first item (as I understand you) is that the slats do not extent to the fuselage - eh what is the second reason in your "wild guesses"?

Abba
 
boeing767-300
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 4:10 pm

This is exactly part of the reason I will adopt a 'Wait and See' attitude with A380.

Sure I have been quick to critisize A380 but then I don't blindly believe everything the Leahy and Co say about it either.

To put is simply, Big Plane equals Big Wake And Big Wake equals Big Drag and Big drag equals More Fuel to propel A380 through the Air which probably equal a lot more expensive to operate than A may have predicted.

As I have stated before A380 has a big task ahead proving it is capable of its 'promised expectations'

I sincerely hope A does better with this project than with A346 because it just may prove that it will be better to fill a fuel efficient large twin "Ala 777-300ER than to run around with less than full A380s burning cash.

Time will tell  Wink
 
ikramerica
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 4:13 pm

Quoting MD80fanatic (Reply 55):
The A380 smears the inner trails within 1 plane length of distance, which is wierd. It really shouldn't be doing that.

I noticed this on the picture in the high altitude thread, and it struck me as strange to look at, like something was wrong and I couldn't figure out what because I'm not an aerospace engineer. but I am a civil engineer by education and have taken enough dynamics to recognize when something seems off...

Thanks for providing a plausible explanation for why it might look that way.
 
zvezda
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 6:58 pm

Quoting N79969 (Reply 5):
That's true and that could be a serious problem especially at LHR. I am sure the Narita airport authority will not be thrilled either. What is the sensible and fair way of dealing with that effect?

Make it wait until no other traffic are predicted to need to use the runway for 10 minutes.

Quoting Ikramerica (Reply 35):
Wonder if two HUGE engines and two Boeing style wings on a composite Y3 will have a much lower wake profile than 4 merely BIG engines on a larger, Airbus wing with the A380. And what will this mean to the as of yet not launched A380-900 and A380-800HGW?

Y3 will probably be about 100,000 lbs (OEW) lighter than the WhaleJet. Therefore the wake turbulence will almost certainly be less.
 
oly720man
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 7:29 pm

Interesting that everyone's getting so excited about ATC difficulties with the A380. How many airports is this going to affect? If an airport gets 10 a day it's only 10 minutes added if there's 1 minute increased separation. I'd imagine that DXB will be most affected if EK are getting 43 of the beasts and I don't think that airport is congested in terms of slots.

Now there's the issue of the prevailing wind. If it's across the runway rather than parallel to it then separations can be reduced because the wake will be blown sideways, though this will be another issue with parallel runways.

A lot of people seem to be confused by wake turbulence. There are 2 totally different aspects to this;

1 the turbulent wake of the aircraft that gets dispersed fairly quickly and
2 the tip (wing/flap) vortices that are sustained for a long time - look at any contrail or aircraft landing


View Large View Medium
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Photo © Josef P. Willems



In this photo you're not seeing the exhaust plumes from the aircraft it is some of the condensation from the exhaust that have become entrained in the tip vortices as you can see here


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Photo © TriplET



On landing there are different issues as the flaps are deployed.


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Photo © Erwin



It is the tip/flap vortices that have the greatest impact on aircraft separation and inevitably these will be stronger with a heavier aircraft. Not a lot you can do about that.

In simple terms the equation for vortex strength (gamma) is

Lift = Air density * Velocity * gamma

For an aircraft at low velocity (landing) then gamma has to be high. This is complicated slightly by the issue of flaps/slats, etc.

Quoting MD80fanatic (Reply 66):
This is a wild guess....I think the flaps/slats deployed wake turbulence problem is due to two items....first the slats do not extend to the fuselage, making a odd junction that is not necessarily conducive to laminar flows. In fact the entire leading edge is broken up into 6 sections, root to tip.

There will be next to no laminar flow on an aircraft this size. It will be turbulent over most of the aircraft, and over any aircraft bigger than a glider. Even an aircraft in the cruise configuration will have turbulent flow over it, or more accurately a turbulent boundary layer.

Beware terminology. Turbulence in aircraft design is a description of the nature of the boundary layer over the aircraft. It is not the same as the popular description of turbulence as a disturbed flow. Laminar flow is a description of the nature of the boundary layer.

In brief a laminar flow has no mixing, i.e. as the boundary layer develops streamlines within it will remain reasonably parallel. In a turbulent boundary layer they don't.


View Large View Medium
Click here for bigger photo!

Photo © French Frogs AirSlides



In this photo the two vortices are from the engine chines and are no different from those that are found on the 737 or DC10.


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Photo © Thowman



The difference between the inner and outer vortices are that the inner one has burst and the outer one hasn't. This in no way reflects laminar or turbulent flow, it's to do with vortex behaviour.



This is vortex bursting on an F18 and happens when a vortex becomes unstable and rather than having a spiral structure it goes chaotic. In this photo smoke is used to show the vortex. On the A380 it's condensation and that disappears as the pressure field changes when the vortex has burst.
 
sabenapilot
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 8:21 pm

Quoting Oly720man (Reply 72):
There will be next to no laminar flow on an aircraft this size. It will be turbulent over most of the aircraft, and over any aircraft bigger than a glider. Even an aircraft in the cruise configuration will have turbulent flow over it, or more accurately a turbulent boundary layer.

Indeed, plane manufacturers will do every thing possible to make the flow over the wing turbulent by means of putting small wings (called vortex generators) on top of the wing... just have a look at the wing of a 737 to see what I am talking about!

Quoting Oly720man (Reply 72):
Beware terminology. Turbulence in aircraft design is a description of the nature of the boundary layer over the aircraft. It is not the same as the popular description of turbulence as a disturbed flow.

I guess we've seen too many people with minimal knowledge of aerodynamics stepping in a discussion where sadly terminology is not the same as in the outside world, leading to all kinds of completely ludicrous assumptions like: they have to make the wing more laminar!!!

Back to the initial topic:

Quoting AeroPiggot (Thread starter):

Initial ICAO guidance is as follows:
1) one additional min to be added to all separations, when the A380 is the leading aircraft.
2) Horizontal spacing on final approach to be no less than 10 NM between A380 and following aircraft.
3) vertical spacing to be no less than 2000ft when following behind the A380.

Putting this into practice:
1) ICAO recommends the A380 to make a full runway length departure and the following plane an intersection departure, thus making it 3 minutes, just like it is now in case for instance a 737 from an intersection follows a 747.
2) Horizontal spacing between the A380 and what? a Light aircraft? a Medium aircraft or a Heavy? Can't imagine they will not distinguish for the category of the following aircraft as this is done in all other cases. The 10NM miles figure wouldn't be in case a Light aircraft ala Citation X follows on an A380, would it???
3) That could potentially be somewhat annoying for ATC during cruise, but not really posing much problems since the bottle necks are on the ground, not high up in cruise.

Anyhow, these are initial recommendations only, based on a very conservative approach to the occasional handling by unfamiliar ATC of a non-certified test plane rather than a set of legal separation minima based on experience gathered from real day-to-day operations. Was it really necessary to blow this out of proportion???
 
Rj111
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 9:18 pm

Well, isn't this catastrophical for Airbus' "A380 needed for slot resticted airports" slogan?
 
oly720man
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 9:32 pm

Quoting Sabenapilot (Reply 73):
Indeed, plane manufacturers will do every thing possible to make the flow over the wing turbulent by means of putting small wings (called vortex generators) on top of the wing... just have a look at the wing of a 737 to see what I am talking about!

These are to stop flow separation at higher incidences. Ideally manufacturers wouldn't want them because they increase the cruise drag.
 
alasdaironeil
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 10:27 pm

Oly720man.



I've seen that F18 photo before. I watch it on a video.

I believe that the vortex from the front actually causes excitation in the vertical stabiliser, i forgotten the frequency but its pretty damn high.

Just shows the problems the votex can cause.

On the Tornado, the excitation from the wing caused part of the vertical stabiliser to break off because they was using it as a fighter role, rather than a bomber as it was designed for.

Point being though, the F18 mananged to fix this problem by adding a "block" on the fuselage on the path of the vortex and divert it from the tail, however it is still a problem for the F18 today in general.

It shows that this problem is difficult to solve, i wonder if it can be fixed on the A380???

Alasdair
 
md80fanatic
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 10:41 pm

Ideally, the top surface of any wing should be as smooth as possible. The more the air is churned the higher it's pressure will be.

People should not discount the leading edge geometry, as this is where the "rubber meets the road". The leading edge seperates an air parcel into an upper section and lower section. The smoother this is accomplished the smoother the two parcels will be reintegrated after the wing passes, with minimum internal rotations.

I think the Airbus design of having the entire leading edge drop into the airflow is fine on smaller aircraft, more mechanically dependable and less expensive to implement for certain. However I think we have reached critical mass with this huge bird.
 
Mark_D.
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 10:44 pm

Sabenapilot -- Was it really necessary to blow this out of proportion???

For a lot of the gang here, absolutely it is! The societally-induced xenophobic tribal hatred in some of these ~16-year-old or ~16-year-old-mindset characters is maybe too self-injurious to keep bottled up for long!  fever  fluffy 

As for ol' 380 --and its prospects, and Airbus' as a whole, and so on-- I think it's great that it's visiting Singapore and Down Under and Malaysia too, presently. And I figure it's unlikely they'd trot the plane around like that if the wake vortex data really are anything even close to a showstopper for its passenger use in slot-restricted high-traffic airports worldwide.
 
Boogyjay
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 11:03 pm

Well, these are recommendations only.

I'll wait for the final certification and real-life ATC practices.

In TLS, the A380 already flies with the regular "heavy" category wake turbulence distances and although TLS is not as crowded as LHR, there is some traffic there everyday with annual 5.6M pax.

That's just to contrast with some over-exxagerated comments that state (in another thread) that "the whalejet crashes anything that flies within 50 miles of her wake". Has someone heard about fatal accidents in TLS lately?  Yeah sure .
 
abba
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 11:14 pm

Quoting Oly720man (Reply 72):
Interesting that everyone's getting so excited about ATC difficulties with the A380



Quoting Sabenapilot (Reply 73):
Was it really necessary to blow this out of proportion???



Quoting BoogyJay (Reply 79):
In TLS, the A380 already flies with the regular "heavy" category wake turbulence distances and although TLS is not as crowded as LHR, there is some traffic there everyday with annual 5.6M pax.

So is this to say that there realy is no major problem related to this? I ask the question due to the fact that I have no knowledge of this field and you people seems to know pretty much what you are talking about!

Abba
 
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RayChuang
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 11:49 pm

Quoting BoogyJay (Reply 79):
I'll wait for the final certification and real-life ATC practices.

I agree at this point--someone should try to fly a jet fighter behind the A380-800 and actually measure its wake turbulence. I wonder does Airbus have access to a Mirage III or F1 test plane that can be outfitted with such measuring devices?
 
trent900
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RE: A380 Wake Turbulence Data Are In

Tue Nov 15, 2005 11:58 pm

If someone could clear a thought for me:

If the wake falls away after the aircraft has passed (be it an A380 or 737) how can the aircraft following on the glideslope be effected? Surely it would just fly over the top. From experience I've only been 'bumped' by aircraft at a higher altitude then me.

I think once the craft is in service you'll see the standard large aircraft spacing of 6 nm.

D.
 
oly720man
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RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 12:18 am

Quoting MD80fanatic (Reply 77):
Ideally, the top surface of any wing should be as smooth as possible. The more the air is churned the higher it's pressure will be.

People should not discount the leading edge geometry, as this is where the "rubber meets the road". The leading edge seperates an air parcel into an upper section and lower section. The smoother this is accomplished the smoother the two parcels will be reintegrated after the wing passes, with minimum internal rotations.

Aircraft are not designed so that a block of air is chopped in 2 by a wing and then joined up again after the wing has gone past. Aerodynamics doesn't work like that. The only way this could happen is if the wing was infinitely thin and at zero incidence, and even then you'd still have the boundary layers from each side of the "wing" that would form a wake that would separate the divided air.

About the only feature of the leading edge that is critical is its radius of curvature. If the curvature is too high then there is the possibility of flow separation leading to higher drag and reduced lift. This is why leading edges are elliptical (or distorted elliptical) rather than semicircular.

Why some manufacturers go for droop slats or Krueger slats is a matter of design considerations since they have similar performance. Any gaps or discontinuities created by the droops are very minor. Kruegers are usually used on thinner wings.

Quoting Alasdaironeil (Reply 76):
It shows that this problem is difficult to solve, i wonder if it can be fixed on the A380???

It's not a big problem on the A380. The vortex from the chine does its work around the slat gap at the wing leading edge. Once it's past there it has little impact on the flow over the wing. All they'd need to do is probably move the chine if they wanted to avoid vortex bursting. This is probably a case of it worked fine there in the wind tunnel and behaves a little differently on the full size aircraft. Vortex bursting causes pressure fluctuations that lead to fatigue. This is potentially a big problem with composites used in combat aircraft because the high frequency pressure fluctuations can lead to delamination of the composites and reduced strength.

The F18 problem is much more serious because it led to metal fatigue in the fin root so stronger+heavier structures had to be used.
 
georgiaame
Posts: 1025
Joined: Sat Aug 13, 2005 7:55 am

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 12:24 am

Is this really bad news?

The physics may not be pretty, and it might be a great point for bashing, but if I were sitting with some 800 other people, I would be a lot happier knowing the nearest aircraft to me is a lot further away from this machine that it might be if I were flying in something else. I wouldn't care what the reasons are.

Its like wearing garlic around your neck to ward off a cold. It works, but not for the reason you think
 
keta
Posts: 405
Joined: Thu Mar 24, 2005 7:14 am

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 12:44 am

Quoting AeroPiggot (Thread starter):
Flight test data shows that the A380 wake vortices will descend further and are significantly stronger at 1000ft (300m) below the generation altitude than for any other aircraft in its weight category

I'm disappointed. I believed Airbus would get an airplane with weaker vortices. But well, maybe they can fix the problem a little bit, let see what happens with final certification.

Quoting AirFrnt (Reply 34):
You would have to reduce the weight of the plane by a good 13-20 percent (as I understand it, Wake is increased by weight but decreased by wingspan) to make the wake profile look similar to a 747.

Yes, but using wingtip fences I hoped they would be able to get a similar wake. Perhaps they can do changes to the wingtips.

Quoting MD80fanatic (Reply 55):
In this image I think you can see where some of the problems are originating from.

Are you serious?? Are you really taking these conclusions from regarding this picture? So, it seems like the wing root produces less lift than it should, hence the wing produces greater wake? If that was true, actually the wake would be reduced, as wingtip vortices are created because lift decreases from wing root to tip. Well, sort of. I'm not saying that this is what actually happens, because I can't get much useful information from that pic! I think all your conclusions are, sorry to say, based on nothing.

Quoting MD80fanatic (Reply 55):
The A380 smears the inner trails within 1 plane length of distance, which is wierd. It really shouldn't be doing that.

Lots of people are saying things out of that picture. You can't really get a lot out of that. It's just a few meters of sky, where you don't know what conditions there were, what shot angle, etc.

Quoting Oly720man (Reply 72):

Thanks for AN informative post!  thumbsup 
 
Slarty
Posts: 302
Joined: Fri Sep 16, 2005 5:23 am

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 12:56 am

Quoting AeroPiggot (Thread starter):
What will be the impact on airport operations?

A380 traffic will reduce overall airport aircraft movements. The increases in pax loads on A380 will be reduced by decreased flight movements.

Net result? A wash!

so much for it helping with congestion ... LOL
 
Glom
Posts: 2056
Joined: Sat Apr 23, 2005 2:38 am

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 1:02 am

Quoting GeorgiaAME (Reply 84):
The physics may not be pretty, and it might be a great point for bashing, but if I were sitting with some 800 other people, I would be a lot happier knowing the nearest aircraft to me is a lot further away from this machine that it might be if I were flying in something else. I wouldn't care what the reasons are.

This is really not particularly useful at all. First of all, we can't overlook the FUD loaded into your statement where you imply that spacing as it stands is noticeably less safe than you would like it. Second of all, the business case for the A380 is to help increase capacity at slot restricted airports. As it stands, capacity is reduced with the A380.
 
N79969
Posts: 6605
Joined: Tue Jan 29, 2002 1:43 am

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 1:09 am

This issue will create tension between A380 operators and non-operators at airports. Some in the "non-" category have already made clear that they would be unwilling to help pay for improvements made to accommodate the A380. I do not think this group would be amenable to making changes to their own schedules to accommodate A380 operations. British Airways at Heathrow is the obvious example.
 
Slarty
Posts: 302
Joined: Fri Sep 16, 2005 5:23 am

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 1:31 am

Quoting Ikramerica (Reply 27):
Not exactly a great "hub-hub" aircraft if a 50% increase in capacity inside creates a 66% negative impact in capacity on the outside.

I had been following the delays associated with the vortex data, and suspected something might be amiss. Clearly, this is not the result that Airbus was designing for.

Quoting Cloudyapple (Reply 36):
I suspect 10Nm is a super conservative guideline to start with just to be on the safe side. It should reduce to perhaps heavy +1 or +2 as we collect and analyse actual operational data.

IIRC, when the 747 was introduced almost 40 years ago (wow), they also used a conservative separation envelope, and it got relaxed as more operational data was gained.

So I would expect the same for the A380. With a final result being a larger separation requirement than any other aircraft today, but still far better than what is being suggested for launch.
 
N1120A
Posts: 26856
Joined: Sun Dec 14, 2003 5:40 pm

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 2:04 am

Quoting MD80fanatic (Reply 4):
Big plane = Big wake .... it's physics.

Usually true, and certainly true here, but how do you explain the disproportionately large wakes of the 757 and the DC-10?
 
TAP340
Posts: 100
Joined: Mon Nov 01, 2004 7:22 am

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 2:08 am

Quoting A350 (Reply 21):
I fail to understand how so large differences between wind tunnel experiments and reality can occur.

Not hard at all. Fluid mechanics is one of the most complex areas of physics, if not the most. For instance, mathematics are not developed enough for some cases in fluid mechanics, and the "simple" flow that emanates from a cigarette is not yet understood. Furthermore, CFD and wind test still have high error margins. This is only what I was thought at collegue though.

Oly720man:
Finally a post from someone that really understands what the hell he is talking about! (BTW, welcome to my respected users list)

[Edited 2005-11-15 18:28:01]

[Edited 2005-11-15 18:32:46]
 
asteriskceo
Posts: 515
Joined: Fri May 21, 2004 12:42 pm

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 2:26 am

Quoting PPVRA (Reply 32):
What if Airbus managed to reduce some weight?

Take out the bar. The gym. The Library. The lounge. The restraunt. The Liquor Store. The onboard farmer's market, and I'll bet It'll be as light as the 747!

Wink.
 
redflyer
Posts: 3910
Joined: Thu Feb 24, 2005 3:30 am

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 2:38 am

Quoting Oly720man (Reply 83):
Kruegers are usually used on thinner wings.

Not that I'm disputing what you're saying (hardly, since I'm no aeronautical engineer); however, I thought Kruegers were used on thicker wings? Hence, the use of them on the inboard sections of 72's and 73's where the wing is considerably thicker.

Quoting N1120A (Reply 90):
but how do you explain the disproportionately large wakes of the 757

If I recall correctly from reading the original NTSB reports that involved some incidents' with aircraft following too close behind 757's back in the 90's, the problem was not that the 757 produced disproportionately large wakes. Rather, the problem was that the 757 was not classified as a "heavy". The reason being, its typical operating weight was just a shade under 250,000 lbs and at the time (still?) the "heavy" classification was/is assigned to aircraft over 250,000 lbs. In short, you had an aircraft approaching a "heavy" classification but which was given standard separation sequencing more appropriate for smaller and lighter aircraft.
 
ikramerica
Posts: 15180
Joined: Mon May 23, 2005 9:33 am

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 2:40 am

Quoting Oly720man (Reply 72):
Interesting that everyone's getting so excited about ATC difficulties with the A380. How many airports is this going to affect? If an airport gets 10 a day it's only 10 minutes added if there's 1 minute increased separation.

It only really effects the airports it is designed to increase traffic flow at. Potential, repeat potential, to offer no value to an airport, now that they've invested all that money making them ready.

Quoting GeorgiaAME (Reply 84):
Is this really bad news?

The physics may not be pretty, and it might be a great point for bashing, but if I were sitting with some 800 other people, I would be a lot happier knowing the nearest aircraft to me is a lot further away from this machine that it might be if I were flying in something else. I wouldn't care what the reasons are.

What a silly, silly comment.

Quoting N1120A (Reply 90):
but how do you explain the disproportionately large wakes of the 757 and the DC-10

From how I understand it, the 757 has small wings to fit in 727 sized gates, and large engines to keep it flying. Small wings add to wake vortex.

The DC-10 has small wings as well, and flies at a greater pitch to help generate lift (plus has the 3 engines when it could have been designed to take off with two). Again, this was partly to get into LGA. Again, smaller wingspan on a heavy powerful jet leads to more wake, right?
 
Ken777
Posts: 10194
Joined: Thu Mar 11, 2004 5:39 am

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 4:26 am

I think Airbus will work out the problems, but it's really poor timing since the 747ADV was released right after this news hit.

The main challenge Airbus faces will be the ability to have the 380 participate in the important slot times, like the early morning at LHR. If it impacts other carriers then you can be sure they will be pushing for 380 arrivals to be moved to times where they will not cause a problem, resulting in the changes in the flight schedules of the 380.

It's going to be a weird situation until Airbus gets a handle on it.
 
BoomBoom
Posts: 2459
Joined: Fri Nov 04, 2005 2:26 am

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 4:33 am

Quoting Mark_D. (Reply 78):
Sabenapilot -- Was it really necessary to blow this out of proportion???

For a lot of the gang here, absolutely it is! The societally-induced xenophobic tribal hatred in some of these ~16-year-old or ~16-year-old-mindset characters is maybe too self-injurious to keep bottled up for long!

Actually it's been quite an informative thread. Nothing blown out of proportion.

And please spare us to the pop-psychology...
 
DAYflyer
Posts: 3546
Joined: Wed Sep 08, 2004 9:35 pm

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 4:47 am

Quoting Cloudyapple (Reply 2):
I can say categorically it is going to be a pain to work it as an air traffic controller. If 10Nm is the case for every A380 arrival you lose up to 3 other slots (2.5Nm). It actually reduces capacity at congested airports like Heathrow.

Guess that effectively kills off any hope of a BA order, eh?
 
slider
Posts: 7751
Joined: Wed Feb 25, 2004 11:42 pm

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 4:50 am

Quoting Cloudyapple (Reply 2):
I can say categorically it is going to be a pain to work it as an air traffic controller. If 10Nm is the case for every A380 arrival you lose up to 3 other slots (2.5Nm). It actually reduces capacity at congested airports like Heathrow.



Quoting Ikramerica (Reply 27):
Not exactly a great "hub-hub" aircraft if a 50% increase in capacity inside creates a 66% negative impact in capacity on the outside. Hopefully this can be reduced, but it demonstrates that the net effect of A380s at an airport might be a ZERO sum, meaning it won't bring more pax into a slot limited airport in any meaningful way, which was the promise.

Both good points- I'm sure the details will all shake out as time goes by and the practical considerations of flying the 380 take shape, but yes, on the surface, it does seem incongruous that a bird that was supposed to (and sold as) relieve congestion at large hubs may add to it in ATC terms. Not to mention the actual airport engineering specs of accommodating this leviathan.

Quoting ContnlEliteCMH (Reply 52):
Fluid mechanics is definitely a black art, despite what some on this board postulate, that computational fluid dynamics is mature enough that you shouldn't even need physical testing. But wind tunnel testing is a well-established method. There are millions of wind tunnel hours in the books.

It's like the Hubble debacle. The story has it that the mirror was ground to a perfect QA level -- measured with a faulty QA rig. Makes you wonder...

Not black art, but at both ends of the spectrum--very large and micro, aerodynamics doesn't change per se, but the way they interface with it does. Tough to explain, but Air & Space had a great feature on how the characteristics of micro-sized flying machines are vastly different from 'standard' aerodynamics. Same phenomena at the other end with gigantic A/C. Also, the Hubble suffered from having a mirror that was crafted and shaped in a gravity environment--I believe some of the distortion issues grew out of the fact it was then operating in a zero-g environment; something about the optics was also a complicating factor.

Quoting PyroGX41487 (Reply 59):
I hope this doesn't take away from the conversation, but a bit of humor: If one of these things managed to land and take off again at SXM, the beach and all the people on it would be OBLITERATED.

YIKES!! LOL! No kidding- I don't think we'll see the 380 buzz the beach on final for SXM.

Quoting MD80fanatic (Reply 77):
I think the Airbus design of having the entire leading edge drop into the airflow is fine on smaller aircraft, more mechanically dependable and less expensive to implement for certain. However I think we have reached critical mass with this huge bird.

I'm not engineer, but that might be a valid point- is size an inhibitor to what would otherwise be more optimal control surface designs?

Quoting Oly720man (Reply 83):
Why some manufacturers go for droop slats or Krueger slats is a matter of design considerations since they have similar performance. Any gaps or discontinuities created by the droops are very minor.

Again, I don't speak from an engineering background, other than having some working knowledge of it, but wouldn't the effect of those gaps be magnified by virtue of the massive size? Theoretically on a standard narrowbody or even some widebodies, one would think slat type wouldn't make that big a difference, but that's a hell of a lot of air moving over a hell of a large object being forced into a much larger wake profile. Possible?
 
tockeyhockey
Posts: 882
Joined: Fri Feb 04, 2005 10:57 pm

RE: A380 Wake Turbulence Data Are In

Wed Nov 16, 2005 4:53 am

not to bash airbus, but this is all further proof to me of how amazing the 747 is. boeing seems to have gotten the jumbo jet right the first time 30 years ago -- and it's still alive and kicking!

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