The A380 and wake turbulence

For the militant Airbus types, I have a question. How much wake turbulence does the A380 generate? Is it going to require greater separation for aircraft in the pattern? If so, won't that negate some of its advantages by reducing the number of planes that can land etc?

I'm curious what do you mean by ' wake turbulance ' and how would this reduce the nubers of aircraft that can land ?

Wake Turbulence kind of like what we call jet wash. An example of this in the movie top gun. FredT I think it will increase the time between landings which overall will affect the number of jets landing per day. I�ll get back to you on how much wake turbulence it produces.

Originally posted by FredT
For the militant Airbus types, I have a question. How much wake turbulence does the A380 generate? Is it going to require greater separation for aircraft in the pattern? If so, won't that negate some of its advantages by reducing the number of planes that can land etc?

- Doesn't wake turbulence depend on things like 'frontal area'?

IIRC this would mean that the frontal area of an A380 is almost no different to a Boeing 747 as the frontal area is similar due to the 747's hump-back forward section.

I wouldn't worry too much Fred, do you think you're the only one to have thought of this?

Originally posted by mad scientist
I'm curious what do you mean by ' wake turbulance ' and how would this reduce the nubers of aircraft that can land ?

Aircraft that generate large air wakes (The 757 is really bad We were in the chopper on a transport and we were bounced around by a 757 3 miles ahead) and some aircraft require a certain amount of separation or distance between them to minimise thier effects. I believe that the American Airlines A300 that crased into Queens after 911 was hit by the wake of a 747.

Thanks for the explanation FredT, now I understand what you're talking about.

Originally posted by sminkeypinkey
- Doesn't wake turbulence depend on things like 'frontal area'?

There are many things contributing to wake turbulence.

www.asy.faa.gov...

Good image of turbulence caused by plane:


www.cnn.com...


I think there were studies going on how wake turbulence could be made smaller.

All aircraft produce wake turbulence, which consists of wake vortices formed any time an aerofoil is producing lift. It's not a function of "frontal area", but a product of required lift. i.e., a larger aircraft flying clean (flaps and gear up) at a slow airspeed requires a higher angle of attack, increasing the pressure on the underside of the wing while decreasing it on the upper side, forcing the air to curl up and over the wing, thus creating more violent wingtip vortices which flow out away and down from an aircraft. When in close proximity to the ground and requiring high lift such as in take off or landing configuration, the vortices have nowhere to go but to the ground, thus requiring more time to dissipate. They sometimes bounce around, so to speak. Ground effect and a nice 3 to 5 know cross wind can cause them to dissipate quicker, although it can also keep the up wind side on the runway longer. Usually the larger the aircraft, the more wake turbulence it generates, but not always. The C-5 is the largest US military aircraft, but the C-17 has the tendency to produce such violent wake turbulence that paratroopers jumping out have been literally doing loop-de-loops in their harnesses under canopy! The static lines had to be lengthened to keep troopers for being injured.

Each aircraft is tested to see what its wake turbulence characteristics are, and how it responds to flying through another aircraft's wake. The biggest problems are usually induced roll and yaw, which can be really hairy if you don�t know what is happening. Wait times between take-off's, usually 2 to 3 minutes for commercial aircraft, are adjusted accordingly. You wouldn't send a Cessna 172 down the runway 30 seconds after a 757!!!

Originally posted by Affirmative Reaction
It's not a function of "frontal area", but a product of required lift.

- Then I stand corrected. Ta.

(I had thought it a function of frontal area leading to certain characteristics with the resultant displacement of the air.)

Each aircraft is tested to see what its wake turbulence characteristics are, and how it responds to flying through another aircraft's wake.

- Yes, I was pretty sure this would be so. Particularly as this is a recognised potentially dangerous phenomenon.

The Wake turbulence from a Vulcan bomber was so bad that microlights couldn't fly in the same airspace until 24 hours later.

Originally posted by Cjwinnit
The Wake turbulence from a Vulcan bomber was so bad that microlights couldn't fly in the same airspace until 24 hours later.

Ummm...could I ask where you got that information????

Originally posted by WestPoint23
Wake Turbulence kind of like what we call jet wash. An example of this in the movie top gun. FredT I think it will increase the time between landings which overall will affect the number of jets landing per day. I�ll get back to you on how much wake turbulence it produces.

Wake turbulence and jet wash are two different things. One is a property of aerodynamics and one is a property of engine exhaust.

Please do some research before you post.

Originally posted by COOL HAND

Wake turbulence and jet wash are two different things. One is a property of aerodynamics and one is a property of engine exhaust.

You are mostly correct, Cool Hand, but "jet wash", or "prop wash", which ever the case may be, does contribute slightly to the severity of wake turbulence in that it can add to the rotational force of the vortices created on the side of the aircraft where the forces match direction, and decrease it on the side where they oppose. Wake turbulence vortices oppose each other on each side, (counter clock wise on the left - clockwise on the right - as seen from the aft of the aircraft) where as most aircraft's engines rotate in the same direction, creating prop or jet wash that is consistent.

Originally posted by Affirmative Reaction
You are mostly correct, Cool Hand, but "jet wash", or "prop wash", which ever the case may be, does contribute slightly to the severity of wake turbulence in that it can add to the rotational force of the vortices created on the side of the aircraft where the forces match direction, and decrease it on the side where they oppose. Wake turbulence vortices oppose each other on each side, (counter clock wise on the left - clockwise on the right - as seen from the aft of the aircraft) where as most aircraft's engines rotate in the same direction, creating prop or jet wash that is consistent.

I was just trying to make sure that WP did not just go off of the TOP GUN answer, which is where he seemed to be going with it. In that case the jet wash was the exhaust coming out of the back of the Mig-28's (Ha Ha) or Iceman's Jet.

I was always told that the amount that the engine can affect the wake turbulence was dependent on the size engine, location of the engine (with respect to the vorticies), and the size of the wing itself.

Originally posted by COOL HAND

I was just trying to make sure that WP did not just go off of the TOP GUN answer, which is where he seemed to be going with it. In that case the jet wash was the exhaust coming out of the back of the Mig-28's (Ha Ha) or Iceman's Jet.

I was always told that the amount that the engine can affect the wake turbulence was dependent on the size engine, location of the engine (with respect to the vorticies), and the size of the wing itself.

Yeah, Top Gun was a comedy of errors, almost as bad as Iron Eagle. Simply flying through the jet wash of another fighter won't put you into a flat spin as depicted. If it did, the Blue Angeles and Thunderbirds would loose a bird every time they flew!

You are correct about the rest, but another factor that many people are unaware of is the MAC (Mean Aerodynamic Chord) of the wing, as well as camber. Any time the airflow is forced to increase speed over the top of the wing, the vortices will increase in strength. It�s all about high pressure vs. low pressure, which is the basic principal of lift.

Ooh, Top Gun! I'm immediately reminded of the shot of Maverick flying inverted over the 'MiG 28' with the canopies inches apart, like the fins on both planes just don't exist! Never mind the airflow between the two planes.

Well, that's not nearly as bad as trying to get people to believe that a Lt. Col could sneak his kid up in an F-16 on a regular basis for flight time, let alone walk right in to the simulator for as much stick time as he wants.

Of course, another fav from Iron Eagle is the 400 pound Orderly Room woman...sorry, they don't make uniforms that big. Had to be a hand made job by Omar the tent maker....

Originally posted by Affirmative Reaction

Originally posted by COOL HAND

I was just trying to make sure that WP did not just go off of the TOP GUN answer, which is where he seemed to be going with it. In that case the jet wash was the exhaust coming out of the back of the Mig-28's (Ha Ha) or Iceman's Jet.

I was always told that the amount that the engine can affect the wake turbulence was dependent on the size engine, location of the engine (with respect to the vorticies), and the size of the wing itself.

Yeah, Top Gun was a comedy of errors, almost as bad as Iron Eagle. Simply flying through the jet wash of another fighter won't put you into a flat spin as depicted. If it did, the Blue Angeles and Thunderbirds would loose a bird every time they flew!

You are correct about the rest, but another factor that many people are unaware of is the MAC (Mean Aerodynamic Chord) of the wing, as well as camber. Any time the airflow is forced to increase speed over the top of the wing, the vortices will increase in strength. It�s all about high pressure vs. low pressure, which is the basic principal of lift.

The bad thing about jetwash as opposed to wake turbulence is that jetwash is preheated, and can cause huge problems within the engine if ingested, as it cant be expanded as much as cold air.

This actually causes huge problems with the Harrier, because if the engine ingests hot air it can cause engine failure or loss of power. The Boeing contender for the JSF had problems with this as well, as demonstrated on several occasions.

Originally posted by RichardPrice

Originally posted by Affirmative Reaction


Simply flying through the jet wash of another fighter won't put you into a flat spin as depicted.

The bad thing about jetwash as opposed to wake turbulence is that jetwash is preheated, and can cause huge problems within the engine if ingested, as it cant be expanded as much as cold air.

This actually causes huge problems with the Harrier, because if the engine ingests hot air it can cause engine failure or loss of power. The Boeing contender for the JSF had problems with this as well, as demonstrated on several occasions.

I can see where this might cause a problem with a possible compressor stall, but only if the trailing bird was flying directly in the jet wash of the lead bird for an extended period of time, at least several seconds. Simply passing through the wash would not be enough to cause a compressor stall, especially of both engines as depicted with the F-14. Single engine aircraft might have a slight "hiccup", but the minute time frame of quick fly through exposure would not cause a catastrophic engine failure.

Originally posted by Affirmative Reaction
Well, that's not nearly as bad as trying to get people to believe that a Lt. Col could sneak his kid up in an F-16 on a regular basis for flight time, let alone walk right in to the simulator for as much stick time as he wants.

Of course, another fav from Iron Eagle is the 400 pound Orderly Room woman...sorry, they don't make uniforms that big. Had to be a hand made job by Omar the tent maker....

You forgot the part where the daughters got to get their hands on classified aerial recon. Not exactly the AF's best moment.