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A380 And Wake Turbulance  
User currently offlineEK156 From United Arab Emirates, joined May 2005, 765 posts, RR: 3
Posted (9 years 2 months 2 weeks 5 days 4 hours ago) and read 9082 times:

Can anyone give us more info on the wake turbulance of the A380.. Discovery channel states that the new wing design will reduce wake turbulance on the A380... by how much?? Will the A 380 have a bigger separation distance...

As far as I know, the B747 can flip a learjet upside down due to wake turbulance unless there is a sufficient separation....

40 replies: All unread, showing first 25:
 
User currently offlineMorvious From Netherlands, joined Feb 2005, 707 posts, RR: 1
Reply 1, posted (9 years 2 months 2 weeks 5 days 3 hours ago) and read 9054 times:

They designed the wing in a way that it wouldn't have a bigger wake turbelence then any other big jet flying already around.
Wind tunnel tests gave a positive result. I think they will or have already tested it with the original scale!

They explained why in that same program. And if I remeber correct, there is no need for a bigger seperation bewteen the A380 and the following aircraft.
Don't sue me if this info isn't correct.. I saw this at the Discovery channel.. blame them  Wink



have a good day, Stefan van Hierden
User currently offlineGlom From United Kingdom, joined Apr 2005, 2815 posts, RR: 10
Reply 2, posted (9 years 2 months 2 weeks 5 days 3 hours ago) and read 9012 times:

I suspect the wing fences will prevent the wake turbulence from being too high. Shame though, I was hoping for a new wake turbulence category: light, small, medium, heavy, electron degenerate.

Bigger question: what about wake turbulence from the AN-225?


User currently offlineAeroPiggot From United States of America, joined May 2005, 283 posts, RR: 0
Reply 3, posted (9 years 2 months 2 weeks 5 days 1 hour ago) and read 8815 times:

Quote:
They designed the wing in a way that it wouldn't have a bigger wake turbelence then any other big jet flying already around.
Wind tunnel tests gave a positive result. I think they will or have already tested it with the original scale!

They explained why in that same program. And if I remeber correct, there is no need for a bigger seperation bewteen the A380 and the following aircraft.
Don't sue me if this info isn't correct.. I saw this at the Discovery channel.. blame them

Listen gentlemen, wake turbulence is pure physics, it cannot be avoided. The airplane must generate lift to fly, and as a consequence a downwash is produce from the wings, which dissipates into the surrounding airflow as wake turbulence. The A380 weighing over 1.2 million lbs, must generate at least this amount of lift in level flight, therefore the downwash and associated trailing vortices will be greater than other commercial aircraft. The A380 will have to have a greater separation distance than the B744 from trailing aircraft, which will limit the number of takeoffs and landing from departing or arriving airports.
 twocents 



A scientist discovers that which exists, an engineer creates that which never was.
User currently offlineRichard28 From United Kingdom, joined Aug 2003, 1605 posts, RR: 6
Reply 4, posted (9 years 2 months 2 weeks 5 days ago) and read 8780 times:

Quoting AeroPiggot (Reply 3):
the downwash and associated trailing vortices will be greater than other commercial aircraft. The A380 will have to have a greater separation distance than the B744 from trailing aircraft, which will limit the number of takeoffs and landing from departing or arriving airports.

Not according to Airbus, per an article in the Observer :

"Airbus insists that its unprecedented new design means the A380 will create no more wake disturbance than a 747. The company has measured the wake using computer simulation and is confident it will pass the real-world assessments."

( Source: http://observer.guardian.co.uk/travel/story/0,6903,1474063,00.html )

[Edited 2005-05-16 23:08:31]

User currently offlineAJRfromSYR From United States of America, joined May 2005, 454 posts, RR: 0
Reply 5, posted (9 years 2 months 2 weeks 5 days ago) and read 8729 times:

The A380 wing might be able to distribute the turbulence better, therefore there might not be any need for extra separation. Just a thought.


-AJR-
User currently offlineDLKAPA From , joined Dec 1969, posts, RR:
Reply 6, posted (9 years 2 months 2 weeks 5 days ago) and read 8669 times:

Quoting AeroPiggot (Reply 3):

Like you say, wake turbulence is pure physics. And yes, the A380 weighs alot. In mid-flight, it will probably have a mass something on the order of 450,000kg (this is assuming some fuel has been burned off- note: fuel will be burning thus the weight will constantly change. This is just assuming somewhere in cruise). This means that gravity will be acting to pull the plane downward at a constant force of 4,410,000 Newtons. In order to sustain level flight, the wing then has to create a constant upward force of 4,410,000 Newtons. Anything less and the plane will begin to accelerate in a downward direction, anything more and it will begin to accelerate in an upward direction. To achieve this upward force, there needs to be enough airflow over the wing surface such that it is a mostly laminar flow, and the air on top has to be going faster than the air on the bottom. Basic Bernoulli's principal. When there's enough difference in speeds on the top and bottom of the wing, the faster air on top will create less of a drag force than the slower air on the bottom of the wing. This slower air pushes on the bottom of the wing, exerting more force than the faster air on top, effectively sucking the airliner into the air.

Here's where wing design comes in. At the back of the wing, where the airflow comes back together, alot of turbulence is created, aka wake turbulence. The Faster air hits the slower air and creates eddies. The challenge for airbus was to create a wing that could (using our model of mid-cruise here again) provide 4,410,000 Newtons of upward lift (just enough to resist gravity without climbing), while at the same time keeping the airflow immediately aft of the wing as smoothe as possible. To do this, they would want to create a wing that could accelerate the air at the front of the wing to a very rapid speed, slowing down as it passes to the rear of the wing, where it meets the air coming from the bottom of the wing. The closer these two airstreams match each other in airspeed, the less turbulence there is. There is always going to be wake turbulence, because if the airspeed off the top and bottom of the wing matched each other, the wing wouldn't lift. Airbus has produced a wing that can efficiently lift their airliner, without excessive wake turbulence, because of their extensive wind tunnel experiments and an efficient wing design.


User currently offlineVSIVARIES From United Kingdom, joined Aug 2004, 108 posts, RR: 4
Reply 7, posted (9 years 2 months 2 weeks 5 days ago) and read 8665 times:

Wake turbulence is a very complicated field that is hard to research. But there are many factors that affect it. The latest thinking suggests that large A/C actually produce more wake vortex on the ground (i.e. prior to rotation) than when airborne.
It's been discussed a lot in tech/ops before - suggest you do a search.
B/R



For every action there is always an unequal but mostly similar reaction.
User currently offlineAeroPiggot From United States of America, joined May 2005, 283 posts, RR: 0
Reply 8, posted (9 years 2 months 2 weeks 4 days 23 hours ago) and read 8620 times:

Quote:
Airbus has produced a wing that can efficiently lift their airliner, without excessive wake turbulence, because of their extensive wind tunnel experiments and an efficient wing design.

As you correctly mentioned above, wake turbulence is difficult to research in a lab or computationally. Flight test is truly where the "rubber meets the road", and I am curious to see if all of Airbus CFD data indicating that the A380 will have a lower wake turbulence signature than the B744 will be proven. My guess is....NOT!! The A380 should be properly called the "Typhoon", because that is what will be chasing the it, as it take off and land at the various airports around the world.
 Smile



A scientist discovers that which exists, an engineer creates that which never was.
User currently offlineDLKAPA From , joined Dec 1969, posts, RR:
Reply 9, posted (9 years 2 months 2 weeks 4 days 23 hours ago) and read 8593 times:

Quoting AeroPiggot (Reply 8):
NOT!! The A380 should be properly called the "Typhoon", because that is what will be chasing the it, as it take off and land at the various airports around the world.

Just because an airplane is big doesn't necessarily mean it's wake is going to be. If the difference of the speed coming from the top and bottom is great, then wake turbulence will be great also. You could have a business jet that would require heavy separation if the wing isn't an efficient one.


User currently offlineVSIVARIES From United Kingdom, joined Aug 2004, 108 posts, RR: 4
Reply 10, posted (9 years 2 months 2 weeks 4 days 23 hours ago) and read 8512 times:

Quoting DLKAPA (Reply 9):
Just because an airplane is big doesn't necessarily mean it's wake is going to be.

Sorry but this is wrong. There are no absolutes in this area but what we do know for sure is that more weight = greater wake vortex. This isn't to say that the people in Wales haven't been able to do some clever things with the wings to make it no worse than (let's say) a 744. But sorry my old china wake vortex from biz jets is not considered in normal flying practice here, we allow for about three-five minutes separation on 737 upwards. Haven't had the pleasure of landing behind a departing A380 yet!



For every action there is always an unequal but mostly similar reaction.
User currently offlineAeroPiggot From United States of America, joined May 2005, 283 posts, RR: 0
Reply 11, posted (9 years 2 months 2 weeks 4 days 22 hours ago) and read 8444 times:

Quote:
DLKAPA (Reply 9): Just because an airplane is big doesn't necessarily mean it's wake is going to be

No DLKAPA, size is not the important variable here, weight is. Also remember the conservation of energy law. The heavier the airplane the more lift the wings must generate, and thus the greater the strength of the vortex. Now what do you want to do with it, to reduce the effect on other airplanes is the key. There are ways to cause the vortex to dissipate more rapidly, through destructive interference. I will not mentioned the details here, but suffice it to say, the A380 will not get with in the B744 separation distance (6 nm). In fact if Airbus had this technology, then why did they not implement it on the A346, which has wake vortex strength to rival the B744  Confused



A scientist discovers that which exists, an engineer creates that which never was.
User currently offlineB744F From Germany, joined Jan 2006, 0 posts, RR: 0
Reply 12, posted (9 years 2 months 2 weeks 4 days 21 hours ago) and read 8370 times:

So how exactly can you slow down the air on the top of the wing but not have adverse effects on such things as fuel efficiency? You are creating more drag on the top of the wing, at least that is what it seems. I'm sure Airbus' experts are better at this than I am, but this is probably more from their PR department stating something like it doesn't need any more separation rather than from actual flight testing.

User currently offlineSpeedbird128 From Pitcairn Islands, joined Oct 2003, 1648 posts, RR: 2
Reply 13, posted (9 years 2 months 2 weeks 4 days 17 hours ago) and read 8175 times:

Quoting DLKAPA (Reply 9):
Just because an airplane is big doesn't necessarily mean it's wake is going to be.



Quoting VSIVARIES (Reply 10):
Sorry but this is wrong.

OK, so why then is a 757 notorious for having a wake-turbulence greater than the weight category it should have been in... It's well under the upper limit for a medium aircraft, yet as ATC we treat it as a heavy because of it's wake!?

I tend to agree with DLKAPA...



A306, A313, A319, A320, A321, A332, A343, A345, A346 A388, AC90, B06, B722, B732, B733, B735, B738, B744, B762, B772, B7
User currently offlineAreopagus From United States of America, joined Sep 2001, 1369 posts, RR: 1
Reply 14, posted (9 years 2 months 2 weeks 4 days 16 hours ago) and read 8140 times:

The weight of the aircraft is equal to the downward force it places on the air, if the plane is flying straight and level -- no doubt about it. In order to produce lift, the air pressure over the top of the wing must be lower than the air pressure on the bottom. Out at the wing tip, the high pressure air can scoot around the tip to reach the low-pressure zone. This sets up the vortex or tornado at the wing tips. (To be sure, the air is pressed downward all along the span.)

How bad the vortex is on following aircraft depends partly on the spanwise lift distribution. If the wingtip generates a substantial part of the lift, the vortex will be strong. If the lift is concentrated more toward the center, and falls off toward the wing tips, the vortex strength is reduced. This does not change the total momentum per second transferred to the air, but it reduces the peak wind speed in the tip vortex.

Think of it this way: Would you rather be hit by a tornado for one second, or by a 20 knot wind for ten seconds?

The Spitfire had elliptical wings to achieve an elliptical lift distribution, but an elliptical wing is not the only way to do it. Wing twist and changing wing section can also do the job.

757: relatively short wing, strong vortex.
380: long wing span distributes the load to a wider swath of air, reducing the tip vortex speed.


User currently offlineDLKAPA From , joined Dec 1969, posts, RR:
Reply 15, posted (9 years 2 months 2 weeks 4 days 16 hours ago) and read 8114 times:

Quoting AeroPiggot (Reply 11):
No DLKAPA, size is not the important variable here, weight is.

I guess that's why the 757 is treated by ATC as Heavy?

Quoting B744F (Reply 12):
So how exactly can you slow down the air on the top of the wing but not have adverse effects on such things as fuel efficiency? You are creating more drag on the top of the wing, at least that is what it seems.

No. Change the shape, specifically the curve of the wing. Most of the lift is generated at the front of the wing, where the top of the wing rises sharply before tapering off. This is where the airflow is fastest. By making the taper more gradual, you'd have to extend the wing farther back a little bit, but when the two airflows from the top and bottom come together, the speed will be closer at that point, and the eddies that form will generally be much weaker.

Out of Idle curiosity, has anybody here ever heard the wake behind a CR2 on short final? I've heard pretty much everything that lands at DEN, but the CR2's wake you can hear and it lasts alot longer than any other aircraft. Is it that wierd wing design that is the same reason they have to make that steep nose-down angle on landing (though that's partly also due to the lack of leading edge slats)?


User currently offlineWukka From United States of America, joined Jan 2005, 1017 posts, RR: 16
Reply 16, posted (9 years 2 months 2 weeks 4 days 16 hours ago) and read 8106 times:

Even with the potential of a 99% efficient wing, the displacement of the aircraft is what it is. Bernoulli might back me up here, with his principles, as well as Archimedes and his bathtub.

If anyone wants to take bets on the mandated separation being less than or equal to a 744, I'm thinking about starting my own online betting. Perhaps 100:1 on "less than", 15:1 on "equal"... anything over equal goes to the house.

Worth my while?  Wink How many takers?



We can agree to disagree.
User currently offlineRichard28 From United Kingdom, joined Aug 2003, 1605 posts, RR: 6
Reply 17, posted (9 years 2 months 2 weeks 4 days 14 hours ago) and read 7986 times:

lets not forget that the A380 wing span is longer, so the downward pressure generated is spread over a greater surface area.

Quoting AeroPiggot (Reply 11):
In fact if Airbus had this technology, then why did they not implement it on the A346, which has wake vortex strength to rival the B744

I would guess that the A346 wake turbulance fell within standard limits for normal airplane separation, so there was no need to incorporate anything fancy into the basic wing design.


User currently offlineEnviroTO From Canada, joined Aug 2004, 825 posts, RR: 0
Reply 18, posted (9 years 2 months 2 weeks 4 days 13 hours ago) and read 7926 times:

I'm with the people that say the shape at the rear of the wing, the length of the wing, and the width of the wing can be altered to change exit flow characteristics while still giving the required lift. Lift is about air pressure differentials and not eddie generation. With flaps fully deployed on the A380 significant eddies would form behind the wing, but if a wing is designed with reducing wake turbulance in mind and only leading edge flaps are deployed then wake turbulance can be significantly reduced. As for the question, why not reduce wake turbulence before... probably because wake turbulence doesn't impact the economics of the aircraft in a negative way (it might actually reduce resistance behind the wing) and with the 747 already existing from a time where minimum separations were barely an issue, other aircraft built since then have only needed to match the wake turbulence of the 747. Nowadays minimum separation is a bigger deal because of the congestion at airports and the A380 probably didn't want to increase the separation or create more wake turbulence for safety reasons.

User currently offlineKeta From Germany, joined Mar 2005, 448 posts, RR: 0
Reply 19, posted (9 years 2 months 2 weeks 4 days 13 hours ago) and read 7924 times:

Quoting AeroPiggot (Reply 3):
Listen gentlemen, wake turbulence is pure physics, it cannot be avoided. The airplane must generate lift to fly, and as a consequence a downwash is produce from the wings, which dissipates into the surrounding airflow as wake turbulence. The A380 weighing over 1.2 million lbs, must generate at least this amount of lift in level flight, therefore the downwash and associated trailing vortices will be greater than other commercial aircraft. The A380 will have to have a greater separation distance than the B744 from trailing aircraft, which will limit the number of takeoffs and landing from departing or arriving airports.

You're an aerospace engineer? The wake turbulence of course is a function of weight, but not exclusively! The wing plays a big role. That's what I've read and I've been teached so far. I will tell you one thing: 757. It produces an enormous wake compared with its size (weight). So here you have the proof that it's not just about weight.

Quoting VSIVARIES (Reply 10):
Sorry but this is wrong. There are no absolutes in this area but what we do know for sure is that more weight = greater wake vortex

Only if the wing is the same.

Quoting DLKAPA (Reply 16):
Most of the lift is generated at the front of the wing, where the top of the wing rises sharply before tapering off

Be careful, modern jetliners use supercritical wings, and the shape of the airfoil has nothing to see with a normal airfoil. Supercritical wings are actually more bended on the bottom of the wing, the top is almost straight, and the shockwave is used to get lift.



Where there's a will, there's a way
User currently offlineBigFish From United States of America, joined May 2005, 39 posts, RR: 0
Reply 20, posted (9 years 2 months 2 weeks 4 days 8 hours ago) and read 6155 times:

Quote:
I guess that's why the 757 is treated by ATC as Heavy?

This is really sort of confusing, so I hope you're paying attention.
We do control the 57 as a heavy, but there are certain criteria that make it confusing. We control the 200 as a 757, and a 300 as a heavy due to the weight. The '57-200 has it's own rules that fit between heavy and large. The 300 is over 250k, thus the "Heavy" designation. There are 200's that have had the Max Gross Weight Takeoff increased to just over 250k, and that is reflected in their flight strip. So they will be controlled as a heavy, as well. Hope that clears that up.

Now, back to the topic. Why does everyone insist that there should be certain new rules, or allocations made for the A380? It's a big commercial airliner. However, on the scale of large aircraft, it's really not that big of a deal. THe C5 is still bigger, the AN225 is still a whole lot bigger, and there were no new rules created for them. We, as ATC, are going to apply standard heavy separation to the A380. In a radar room, he is a little green blip, with an H attached to it. And when we set him up for the final, he's going to have standard heavy separation attached to him. Unless there is something that rears its head like it did with the 757, nothing changes. And that's not my department.

Do I care what the wings are shaped like? No, not really. Do I care how it works? No, not so much. All I know is that I'm going to maintain 6 miles in trail for separation, or two miles laterally, and not put two little green blips together at the same altitude, so that I'm not responsible for killing enough people to make it look like I'm competing with the Grim Reaper. I don't see a 747, or a KC135, or a 757. I see green blips. And I seperate those green blips. So, to answer your question.. No new rules, and I'm in the business of keeping little green blips seperated, so that you can get to wherever you're going in that A380, with the really supercritical, super efficient, Bernoulli Principaled, wing fenced, vortex reducing wings. Enjoy your flight.


User currently offlineRayChuang From United States of America, joined Jun 2000, 7993 posts, RR: 5
Reply 21, posted (9 years 2 months 2 weeks 4 days 8 hours ago) and read 5928 times:

It will be very interesting to see what the wake turbulence of the A380 is.

You forget that besides the wing, the horizontal and vertical tail surfaces of the plane are very large. That could make the wake turbulence quite big, to say the least.


User currently offlineAsteriskceo From United States of America, joined May 2004, 454 posts, RR: 0
Reply 22, posted (9 years 2 months 2 weeks 4 days 6 hours ago) and read 5440 times:

I believe flap setting, wing length, and speed of the airplane also play a large role as factors of wake turbulence.

User currently offlineMd80fanatic From United States of America, joined Apr 2004, 2660 posts, RR: 9
Reply 23, posted (9 years 2 months 2 weeks 4 days 6 hours ago) and read 5266 times:

The wake created depends alot on a wing's airfoil thickness and average chord length. The 380 has the thickest and longest chord wing I have ever seen....and I imagine the wake will be proportional.

I think most of the "talk" about this subject is more in the realm of "salesman's pitch" than anything in reality. When flying through fluid (fluid dynamics) there will be a wake generated and there is no known way to reduce it substantially.

Besides....if this plane will carry the load of 2 then what is the problem with giving it a little more space to operate? If I were a measly yacht.....I would elect to keep my distance from the oceanliners if I could at all avoid it.


User currently offlineJayspilot From United States of America, joined May 2001, 298 posts, RR: 0
Reply 24, posted (9 years 2 months 2 weeks 4 days 5 hours ago) and read 4778 times:

it seems that this thread is a perfect example of people trying to be experts on stuff they are not. Aerodynamics is a very complicated, detailed science that has to do with a lot more then basic physics. some people on this thread have incorrectly stated statements saying they know how this wake will perform.
I am of the belief that airbus and the jaa,faa,caa ect will make sure that this plane is certified safely and that when it comes time to determine adaquate seperation requirements a lot of testing will be done on computers and real flight tests. Unless there is an aerospace engineer on this sight with real experience in wing design we are wasting our time typing.


25 Morvious : Airbus showed how the wake turbulence was created with images of a high speed camera. You could see where the wake was created. (at the end of the win
26 Post contains images AeroPiggot : You failed to mentioned where I went wrong in my statements above. Every thing I said is really basic aerodynamics, a subject I know a little about.
27 Jush : Airbus will do it i promise you... I not going to tell ya why but they will meet the 744 standards.
28 LongHorn2000 : There is an important distinction to be made here. There has been a lot of talk about the flow Fields around airfoils. This does create turbulence in
29 AeroPiggot : Quite true, this is a 3D finite wing effect, and airfoil theory may be a good starting point, but cannot in of itself completely explain the phenomen
30 Iwok : You are correct here. I recall seeing 737's flying through smoke to show the wingtip vortecies. I believe this is called downwash? Anyway, if all of
31 Eilennaei : Pardon my interupting, but the wing does not know the weight of the plane it is attached to. The wake turbulence stems from the propulsion of the engi
32 LongHorn2000 : Eilennaei, The weight is only entering the story in that the lift generated by the wings must be equal to the weight of the AC (for level flight of co
33 AeroPiggot : LongHorn, I too believe in modern CFD results, I continue to rely on it to accomplish much of my daily assignments. However wake vortex prediction is
34 Patrickj : Not necessarily true. The portion of wake turbulence that is to be avoided comes from the spanwise flow of high pressure air under the wing into the
35 Iwok : I was thinking about this wingtip problem all day at work today (I know, I need a life) and I had an idea regarding totally eliminating the wingtip v
36 RamerinianAir : Iwok, I like your idea . . . I don't know if it'll work but you are not the only one who draws silly crap like this at work or school. My design would
37 Post contains links Eilennaei : To those that posted on the Vortex: yes, I'm aware the forces have to be balanced for the a/c to fly (straight & level), but that is not the end of th
38 RichardPrice : Sounds very much like the Box Wing concept that the USAF has debated using for inflight refueling aircraft designs, in that it reduces wingtip drag h
39 Post contains images Iwok : Rich, thanks for the tip. I went ahead and took a look, and lo and behold the very idea that I "drew" up has already been proposed. I can see the adv
40 Eilennaei : That's one of the ways composites are changing the way planes are being built. Getting back to the Wright Bros. dimensions on the thickness of the win
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