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MathmatiC

Wake Turbulence

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Wake turbulence tends to sink and move downwind from its point of origin. So if you are worried about it stay above and beyond the person you are followings glad path, but do not put your self in a bad situation just trying to avoid it. ;)
Haven't seen any posts on this subject so I just thought it should be brought up.

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The wake off a canopy is not all that significant from my experience. It may cause you a little scare if you're in the middle of your flare, but otherwise, you'll just feel bump or two.

If you do encounter it in the middle of your flare, get ready to PLF, cause it'll probably drop you from there.

I suppose if you followed someone else's exact approach on a high performance landing, it could cause some serious problems, but that is very unlikely and conditions would have to be dead calm.



Dont f#%k up......

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it could cause some serious problems, but that is very unlikely and conditions would have to be dead calm.


Just ecause it's windy doesn't mean the wake turbulance is not there. It just moves with the wind. Have you ever seen big way's like 120+ ways? Watch the last people landing in the landing area after 100+ other canopy's land. They usually don't land very well, because the air is so turbulant.

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Right you are. I was just saying that if you were to follow in someone's else's exact path, say on a 270 front riser dive, in order for you to hit their wake, it would have to be calm. If it was any wind at all, chances are their wake would move from their approach path downwind.



Dont f#%k up......

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eventually you are going to hit it, assuming they are landing into the wind, and if you are close enough behind that person you are going to get the full brunt of it. Look at the pro dudes when they are doing team turns. One is higher and off to one side, so they clear each others turbulance.

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I dont think this should be speculated about, as people could walk away from this thread with oncorrect/bad info. I have limited experience in doing high performance team landings and the turbulance/wake effect. for What i have done i got some very specific coaching from regulars. like i said i only have about 20 of these type landings so take with pinch of salt, all were very tight and successful. i have also done many (150+) hop 'n pops at altitude and flown around with my buddies all on cross braced canopies varying from 111 s to 90 s. all were loaded from 1.8-2.4

what i have found is that in the immidiate proximity (up to 75 +feet) behind the 'lead' canopy, there is significant wake. this wake is SIGNIFICANT ENOUGH TO COLLAPSE A CANOPY. This happen to two people following me on seperate occasions. once in pahokee and once at z hills. (good to laugh at but not funny) in both instances it seemed that my wake was hit from an angle: ie cutting in behind me from one side or another.

however i have been following someone directly behind them at about 30 feet and been sitting on/in his wake and felt nothing other than a bit of a bumpy ride. so i GUESS that it depends entirely on HOW you hit the wake. i would also say that, how pressurised your canopy is, will play a part. flying half brakes/ full flight etc.

as for the question of where you willl find the wake.. again this is very limited and from my personal experience! but generally it has been above and behind whilst spreading slightly outwards like a flock of ducks following the leader. remember that the canopy is always decending and therefor the wake will be found in roughly the path the canopy has just passed through.

when setting up a team landing, i have found the air to be much cleaner if the following canopy is in line vertically but slightly lower on the horizontal plane. do not attempt this without proper training and instruction as there is huge potential for disaster.

if you look at the PD factory team they set the lead man up highest and the rest are lower behind him. sorry to contradict you SPIZZZARKO but just watch the factory team video. or come to a comp and see it in person.

I hope i have helped but again i re-ascert that my experience is far from the best.

PAUL

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Note: This perspective is not from swooping, but from CReW.

While it is true that wake turbulence might move down and behind an airfoil in a flow, you have to remember that your canopy is also descending faster than the wake turbulence, therefore your "effective" wake turbulence is high and above.

And yes, I think the angle at which you cross the wake is very important. Ofcourse, you have to remember that my statements are with respect to flying a PD Lightning, not high performance canopies (which will tend to exaggerate these effects). In CRW, you can ride the wake of a formation in front of you, it is bumpy, but if you stay in the wake, it will increase your descent rate (loss of lift due to turbulent air going over the airfoil). This is a trick many CRW video guys will use to stay down with stack formations (which descend much faster than an individual canopy for any given wing loading).

Crossing the wake at an angle has some pretty drastic effects, especially if you are already in any attitude other than steady flight. Your canopy will experience loss of lift, but not all at once, certain parts of the airfoil will lose lift first, and your canopy will dive and turn even harder as you cross the wake. It is not a huge deal in CRW, since Lightnings are stable in wake turbulence, and you can use the wake to your advantage to maneuver yourself into position. You just have to anticipate it and react before you fly through the wake. Again, this is in respect to a CRW situation, and not swooping.

My experience says that the wake extends straight behind a canopy, but rises at around a 15-30° angle (will most likely be shallower for a higher performance canopy, this angle is for a 7-cell lightning). It's effect probably extends about 6-8 canopy chord lengths. However, wake turbulence is fairly short lived, so a normal landing interval probably isn't going to affect much.

Edited to add: I have not noticed that wakes off canopies "V" out like ripples following a duck. You can fly in close echelon formation with other canopies and not feel turbulence effects. I will say that the turbulence is directly behind the canopy only, with the turbulence effects spreading out no more than several feet past the wing tips. Ofcourse you have to be careful flying there for the same reason I said before. If your end cell hits the turbulence, you will lose lift on that side. The higher lift on your other side will cause your canopy to turn and dive into the turbulence.

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We had someone hit wake turbulance at sunset over our pond. The lead canopy was a Jedei and the trailing canopy was an 84 Velo. It turned the Velo into a dishrag...absolutely destroyed it. I havent seen anything like it...thank god the velo pilot was over water because if he had been over land he would have been definately hopitalized. Nasty stuff.

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Quote

Note: This perspective is not from swooping, but from CReW.

While it is true that wake turbulence might move down and behind an airfoil in a flow, you have to remember that your canopy is also descending faster than the wake turbulence, therefore your "effective" wake turbulence is high and above.
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If you read my post correctly you will realise that i said the same thing. the wake is above and behind due to the decending canopy.

thanks

Paul

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True, the canopy has much more surface area, but it is meeting the oncoming air with, for the most part, the leading edge. It slices the air more cleanly than the pilot, who is essentially plowing through it.
***

I have done a fair amount of CRW video's and typically was docking last on my stiletto, it flew just fine behind a persons body, but went completely googly fuck in the turbulance of another canopy, the wake from a human body might have enough size to disrupt a single cell of a canopy, but since they are crossported it "shouldnt" be enough to cause any problems..

Roy
They say I suffer from insanity.... But I actually enjoy it.

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D22369 & Spizzzarko, How do you know exactly what was generating said turbulence? Was your canopy behind the canopy in front of you when it felt pronounced? Are you both saying that you were feeling much less turbulence when your canopy was behind the jumper's body that was in front of you?

Have you ever watched jumper with a smoke canister under a high WL canopy? If so, what was the smoke doing behind the jumper?

If you take 4X4 sheet of plywood and hold it edge first into oncoming wind (or even with a slight angle of attack), and then get your buddy to hold a 2x2 sheet with the flat side facing the wind, which do you think will generate more turbulence? I realize this model is not entirely accurate since plywood is neither an airfoil nor a person, but it should at least demonstrate that there is more to consider than just surface area.

And I realize that airfoils do create wake turbulence, but we're flying at maybe 25 mph in full flight. How much do you think they really generate? They don't even achieve true laminar flow at that speed. I would imagine a CRW formation would indeed generate a good bit of turbulence. There are several airfoils there, but there are several bodies, as well.

Lastly, assuming I was misinformed at Brian's canopy seminar, do you think then, that the effect of the jumper on wake turbulence is negligible?

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How do you know exactly what was generating said turbulence? Was your canopy behind the canopy in front of you when it felt pronounced? Are you both saying that you were feeling much less turbulence when your canopy was behind the jumper's body that was in front of you?
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YES

c'mon, think about the size differential here, a human body is approximatly the width of a 175ish canopy cell, there is no way the turbulance from a human body could rob another canopy of all its air. A canopy generating turbulance in the air and another canopy flying behind it is running into its wake, and even a small canopy is large enough to rob several cells of a larger canopy

I had my stiletto directly behind a jumpers body on many occasions doing dragplanes, and downplanes and also in freeflight (no one hanging on to my canopy)......it flew just fine.....,, I have had it act like it ran into a wall by flying behind another canopy.

**********

If you take 4X4 sheet of plywood and hold it edge first into oncoming wind (or even with a slight angle of attack), and then get your buddy to hold a 2x2 sheet with the flat side facing the wind, which do you think will generate more turbulence? I realize this model is not entirely accurate since plywood is neither an airfoil nor a person, but it should at least demonstrate that there is more to consider than just surface area.



Go measure your canopy....... width X depth, how many square feet is that? .... how many square feet are YOU total?.........

*********'


And I realize that airfoils do create wake turbulence, but we're flying at maybe 25 mph in full flight. How much do you think they really generate?
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Enough to rob another canopy of its controll........

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Lastly, assuming I was misinformed at Brian's canopy seminar, do you think then, that the effect of the jumper on wake turbulence is negligible?



I seriously doubt you were misinformed, I think a misunderstanding occured.

Roy
They say I suffer from insanity.... But I actually enjoy it.

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How do you know exactly what was generating said turbulence? Was your canopy behind the canopy in front of you when it felt pronounced? Are you both saying that you were feeling much less turbulence when your canopy was behind the jumper's body that was in front of you?


YES
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***

Okay, then. Would you agree with what has been posted previously about turbulence not being felt directly behind the parachutist creating it, but rather above and behind due to the fact that he is descending?

I do not dispute the fact that my canopy has quite a bit more surface area than I do. If it were meeting the relative wind with the bottom skin first instead of with the leading edge, I believe it would generate a significant amount of turbulence, but it wouldn't exactly be flying anymore. Again, I think simply making an assessment based on surface area alone fails to take into account all of the variables that are at work. I expect that flight mode(deep brakes, front riser dive) and airspeed come into play, as well. Did you know that how much drag your jumpsuit creates affects your recovery arc? And again I would ask, have you ever watched a HP pilot with a smoke canister? If so, what was the smoke doing behind the jumper?



I seriously doubt you were misinformed, I think a misunderstanding occured.
***

Hey, maybe you're right. I'm not going to put words in the man's mouth. I know who I'm going to believe, though.

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I have a bad habit of not articulating what I mean well enough for others to pick up on here....... I'll try again:)
***************


I do not dispute the fact that my canopy has quite a bit more surface area than I do. If it were meeting the relative wind with the bottom skin first instead of with the leading edge, I believe it would generate a significant amount of turbulence, but it wouldn't exactly be flying anymore.
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What I meant was the measurement from the bottom skin to the top skin multiplied by the span (side to side)

***************


Okay, then. Would you agree with what has been posted previously about turbulence not being felt directly behind the parachutist creating it, but rather above and behind due to the fact that he is descending?



honestly I cant comment on that, My canopy was 10' behind the other canopy, zipping around to get the sun behind my back, I was on level (our bodies were pretty much even) it happened in the blink of an eye, one second I had a great canopy, next the riser slapped the sh!t out of me through my helmet....

*****************
Did you know that how much drag your jumpsuit creates affects your recovery arc?
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I havent noticed any difference between my tight RW jumpsuit and my freefly suit..... but I will try to remember to notice any differences next weekend....

*************

have you ever watched a HP pilot with a smoke canister


Yes I have, but its been years ago, and I dont remember what the smoke was doing....other than smoking...... I never said a jumpers body didnt have turbulence behind them, Its just insignificant compared to an inflated canopy in my experiences.... but that isnt a fair assesment of whether a jumpers body has a lot of turbulence, to make it a fair comparison between the two, you would need to put a smoke cannister on the canopy itself, and I dont know about you.....I dont wish to prove my theory that badly.....


Roy
They say I suffer from insanity.... But I actually enjoy it.

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Ladies,

Yes the human body will put off some sort of wake turbulance. Yes, Smoke does travel around behind the pilot's burble. Is it more of a burble than a canopy's? NO. You have to realize that air does more than just flow from fore to aft on a canopy. There is some airflow that travels from center to endcells, and then vorticy's off the stabilizers. The lines themselves create drag, thus creating a disturbance in the airflow behind the canopy (quite similar to there being a disturbance in the force young paduoan learners). When doing crw is there not more buffeting when traveling behind a canopy, than there is when making a dock? That is all I have to say about that.

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lady's??? .... more like......"children":P
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When doing crw is there not more buffeting when traveling behind a canopy, than there is when making a dock? ***

Your point is all I was trying in my verbally inept way to say.... :S

Roy

They say I suffer from insanity.... But I actually enjoy it.

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