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jtravis121

Recovery Arc vs. Wind Speed

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After much research today, I have answered part one of my question.



No you haven't.

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After completion of a turn into a stronger wind, the canopy may still have a specific airspeed but it's actuall forward velocity decreases rapidly because of the headwind, causing the person (in my case a 205lb person) to have a much less change in velocity due to the wind and I swing under the wing faster than on a no wind day.



Sure, you come out of the turn with less forward velocity relative to the ground (which is still irrelevant btw, but even if we pretend to accept it your logic still doesn't work) - but when you were going through the turn you were hooming downwind (relative to ground) much faster than you would have been on a no wind day. In fact, you were faster downwind by the same amount you are now slower into wind.

So your change in velocity from downwind, to crosswind, to into wind is still the same, your swing back under canopy is the same, and the effect on your recovery arc is the same.
Do you want to have an ideagasm?

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I understand the dynamics of how it all works now.



Sorry, nope.

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You may swing the same speed under the canopy, but the canopies forward velocity has decreased much faster in a headwind



Nope. If you use airspeed as a reference (which you should) the velocities, and velocity changes, are all the same. If you use goundspeed as a reference (which you shouldn't) the downwind horizontal speed and upwind horizontal speed will be different, but the velocity change between the two will still be the same.
Do you want to have an ideagasm?

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This statement is incorrect because of the ratio of wind force to momentum that each the canopy and your body experience.



That statement is incorrect because it does not mean anything. It's a collection of unconnected words.

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A canopy and a person are not in a protected "bubble" that does not allow them to feel the effect of outside forces. If they were then a canopy would not collapse or feel turbulence.



But you're not asking about turbulence. You're asking about stable wind speed.

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Both the person and the canopy experience the same wind, if they are already moving in the same direction, a change in direction will affect the way a canopy and person experience new wind direction though, such as when you complete a turn to face into the wind. At this point the wind force on each is very different because of the different size of the wind contact area. The wind force will slow a canopy with much lower momentum much faster than it will slow a person with a much higher momentum.



No. Just no. There is no 'wind force' on the canopy at this point. There is no 'wind contact area'. Think about the situation you re describing - diving the canopy, about to plane out into wind. If there was such a thing as a 'wind contact point' where would it be? It would be the topskin of the canopy. What would happen if the wind was pushing on the topskin of the canopy? It would instantly collapse, and your recovery arc would turn into a plummet.

In stable wind conditions, the only aerodynamic forces acting on the canopy, whether flying straight, turning, diving, whatever(!) are the ones created by your weight powering it through the sky.
Do you want to have an ideagasm?

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A good way of putting it is to picture this: Sit in a rolling chair holding a GI Joe in your hand, close your eyes and have him execute your maneuver. Do it 10 times. If during one of those 10 times someone pushed the chair you're sitting in (eyes still closed), that's just like having a wind from a certain direction, but the maneuver in your hand doesn't change. If you were trying to place your roll-out at the same point on the ground and you have a head wind, you still don't change your maneuver, you're still the guy in the chair. You just have to adjust your setup so that you initiate at distance up wind equal to the horizontal distance travelled during the time it takes to execute the EXACTE SAME MANEUVER. The result will be a shorter roll-out. Tail wind, longer roll-out. Crosswind, you'll have to crab a bit during roll-out if your intention is to fly a specific straight line while crosswind.

Think about the closed-eyes-rolling-across the floor thing for a moment. It becomes very simple if you can grasp this.

To answer one of the questions:

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Which is why my question asked how/if wind speed effects lift during the recovery arc. If the wind speed does not effect lift, then why does it seem that my recovery is sooner (implicating more lift) than on low wind days.



Wind does not affect lift. Your canopy (and physics) doesn't care about how fast the wind travells along the ground. It's because you are probably reacting to your site picture. You're used being able to reach a certain point on the ground and you're likely accidentally changing your input. There's an opposite side to this too that has resulted in more than one ride to the hospital. Some people, reacting to their site picture, expect to see greater forward movement and hold their dive too long, thinking that they haven't reached the point in their maneuver when they need to pull out of it. This emphasizes the need to have your timing down as part of your muscle memory.
"I encourage all awesome dangerous behavior." - Jeffro Fincher

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NOW.......If you're talking about a normal landing pattern: Downwind, Crosswind, Final. You'll find that you have to crab your canopy on various legs to stay in a straight line.

A mental mistake that a lot of people make when they think they "feel the wind" when they turn onto final is because they have turned their head straight ahead now and can hear or feel the wind on their face more at exactly the same moment that they realize their speed across the ground has slowed significantly.
"I encourage all awesome dangerous behavior." - Jeffro Fincher

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Mate, just move your IP closer to account for the headwind, close your eyes and do your turn. You'll be 'reet. :D

I think you're coming out high because you get a steep sight picture with a strong headwind and it looks like you're going in. Conversely, you'll probably go low on strong down winds because it looks shallower than it actually is.

Edit: I skimmed this thread. Seems this has already been mentioned.

I have had canopy coaches tell me that a strong headwind will "hit the top of the wing" and force you to recover. I don't believe that. It's all perception...

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Get some Flysight data and I am sure that you will find that you fly the canopy differently in different wind conditions. I am not going to go into all the details on how you fly differently as it has either already been explained or has to be experienced first hand to fully grasp it.
One easy way to get a better understanding of this is to consider the wind and then try to figure out how different wind speed and wind directions makes you fly your wing differently (crabbing into a strong headwind for example) Once you have noticed how you fly your wing differently, then you will probably figure out how flying the wing differently will affect your turn and roll out. Next step is to think about how different wind speeds change your perception of the ground and you have another set of variables that will affect your turn and roll out.

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kuai43

Wow. Simply, wow.



Ahahahaha... you guys are still trying. "Horse.. water, horse.. water,
"No thanks, I'll just eat this dirt if it's ok with you." - jtravis

I'm going to stick with my original post. :D
Every fight is a food fight if you're a cannibal

Goodness is something to be chosen. When a man cannot choose, he ceases to be a man. - Anthony Burgess

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f94sbu

Get some Flysight data and I am sure that you will find that you fly the canopy differently in different wind conditions. I am not going to go into all the details on how you fly differently as it has either already been explained or has to be experienced first hand to fully grasp it.



Flysight data shows the path of you canopy, not how you fly it, just so all readers are on the same page. If you compare you maneuver from zero wind you should see no difference in vertical speeds but your horizontal speeds and over-all path will change depending on the wind direction. For the purposes of this conversation, I'm leaving out anything about your pattern. You'll fly your pattern according to your path across the ground to your initiation point which is related to wind speed and direction.
"I encourage all awesome dangerous behavior." - Jeffro Fincher

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I've held off with chiming in substantively, but now I feel it's time to help out. Don't listen to some of these fools... physics do play a large role in your recovery arc.

It is widely known that, due to the Coriolis effect, you will definitely recover faster from left-hand turns*. The larger and faster the turn and the higher windspeeds you jump in, the more strongly you will notice the effect. I recommend a minimum of a 270-degree turn and 25 mph winds.

*Please note that in the Southern hemisphere, this will be reversed, but the damn Kiwis and Aussies always do things bass-ackwards anyway. Hell, I heard from someone they even wipe with their left hands.

Also, keep in mind that advice you receive on the webtubes may or may not be entirely accurate. It's usually best to crack open a fortune cookie to ascertain valid content.
Every fight is a food fight if you're a cannibal

Goodness is something to be chosen. When a man cannot choose, he ceases to be a man. - Anthony Burgess

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I completely agree with Kuai43. The Coriolis effect is mentioned in flight one 205 and those who have taken this course should be familiar with this principle.

One of the main reasons we do 270s is to mitigate effects of the coriolis. By first turning into a downwind before facing into the wind the two forces effectively cancel each other out. This also works for down winders by first turning into the wind before finishing your turn and recovering with the wind to your back.

I hope this helps happy swooping bud.
Door! Green! Enjoy

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I heard from a very experienced swooper that a headwind will tend to keep a canopy diving for longer and must admit at first i did dismiss this due to the basic physics of a canopy having no idea of wind speed relative to the ground.
But I took the time to think about it and obviously we don't skydive in a vacuum - if we did we'd go very fast and only in one direction - and was trying to think of whether there is a genuine reason why this might be.
I don't think ground effect could be relevant except at very low altitudes but one thing that could be is wind friction. If the wind is slower nearer to the ground then as a canopy dives it moves into air travelling at a slightly different speed to what it was previously experiencing. It is not impossible to imagine that there should be some effect on its behaviour.
However it is telling that he spoke of a canopy diving longer and the OP speaks of a canopy recovering sooner so the likelihood is that it's all in the mind of the beholder and I just spent 2 minutes brainfarting. Oh well I've written it now so gonna click 'Post'

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What follows is my opinion only, of course, take it for what it is.
Mileage might vary.

If you have the concept of airspeed and groundspeed clarified, there are still reasons why your recovery arc might be affected by winds.
The reasons why wind profiles affect your recovery arc is that, even when the wind feels "smooth" is always bumpy to a degree, so this will always make your canopy recover faster, or in another word make your turn lose less altitude.
Another reason, wind profiles, I start my turn at over 700 ft, there winds are often 14-18 knots on a spicy day, and they might be next to 0 on the ground, as your canopy goes through this wind differential, so do your angle of attack, velocity vectors, etc. While it is true that for a perfectly constant wind, only ground speed is affected, when going through wind speed variations, inertia will make sure that your canopy does indeed reacts to this (dives more or "recovers" by itself), similar to what happens with gusts or when going behind an obstacle during a steady wind day, just more progressively.
Stronger winds and higher wind sheer do affect your canopy very differently depending on whether you go head to tail wind, or tail to head wind, and in some cases these effects can be catastrophic, if they interact poorly with your "overamping" inputs etc.
There is also a "human factor", say you're setting up for a 270, we instinctively (or deliberately) "fight" the winds, to set ourselves perfectly at 90 degree off the target, but in doing so, we use maybe harness inputs, which again, even if minimal they do affect the rest of the turn, it's not exactly the same as starting from a perfectly zeroed position: not only your weight distribution is different, your body position is off, but also your aerodynamic forces are different now, even if you are "zeroed" on the ground, you are have now a small slip angle wrt. to the airflow etc. It's like a plane landing with a bit of rudder to align itself up, yes for the most part it's the same, but it's clearly not *exactly* the same, performance wise.
When you put all of these together, yes, I do think that one can say that wind affects the recovery arc in more ways than one and enough that you need to adjust for it.
Then there is the pure perception element of course: your glide angle is greatly influenced by the winds, so that also plays a role.
I'm standing on the edge
With a vision in my head
My body screams release me
My dreams they must be fed... You're in flight.

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I like seeing all the different ways people have of describing this. Pretty cool how it gets us all thinking. The way I describe it is: There's a little bit of amplification to the whole process going on with the extra wind in your face.

Assuming we've established air speed vs. ground speed and how wind speed affects us, that we've discussed how the canopy doesn't really see or feel (if you know what I mean) any difference whether it's windy or calm, the canopy just goes through the air as it's designed to do, albeit with a flight that is now more compressed since it isn't traveling as far... well then that leaves us with just one other thing.

By amplification I mean I think that it's kind of like a moped going down a hill. Said moped can go 34 MPH on a flat surface but get it going down a big hill and it can get up to 43!! I think that's what is happening in a strong wind landing. A given wing with given wing loading given a pilot's consistent maneuver can achieve X speed and lift with no wind but in a strong head wind it can up the lift ante by an extra few percent because there's an extra bit of push that wasn't there before. The thrust on the wing (gravity) doesn't change but now the wing is getting more lift with that weight and maneuver than it would normally because the wind is giving it a little push that would not and could not be there otherwise.

Then if you do that same thing downwind you stretch the process out, one because you're traveling further and going faster and two because the extra speed and lift aren't increasing in a linear way in terms of flight like they were before, in fact it's kind of the opposite because while you're getting a lot more ground speed out of it your wing is actually flying less efficiently since it is cutting through a lot less air, the act of which is what gives us lift. That's where our perception of safety (headwind) vs. sketch (downwind) comes from. In my opinion
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The way I describe it is: There's a little bit of amplification to the whole process going on with the extra wind in your face.



Then the way you describe it is wrong. There is no extra wind in your face.

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By amplification I mean I think that it's kind of like a moped going down a hill. Said moped can go 34 MPH on a flat surface but get it going down a big hill and it can get up to 43!! I think that's what is happening in a strong wind landing.



That's nothing like what is happening.

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Then if you do that same thing downwind you stretch the process out, one because you're traveling further and going faster and two because the extra speed and lift aren't increasing in a linear way in terms of flight like they were before, in fact it's kind of the opposite because while you're getting a lot more ground speed out of it your wing is actually flying less efficiently since it is cutting through a lot less air, the act of which is what gives us lift.



Everything about this is painful.
Do you want to have an ideagasm?

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Jakee keeps the answer simpler but anway:

JasonYergin


By amplification I mean I think that it's kind of like a moped going down a hill. Said moped can go 34 MPH on a flat surface but get it going down a big hill and it can get up to 43!! I think that's what is happening in a strong wind landing. A given wing with given wing loading given a pilot's consistent maneuver can achieve X speed and lift with no wind but in a strong head wind it can up the lift ante by an extra few percent because there's an extra bit of push that wasn't there before.



Sorry, nope.
Curiously, some think there's "extra push" if going downwind, while you were suggesting there's and "extra push" of the wind against the canopy because it's going upwind.

The canopy doesn't see either. Remember the canopy is always in the same wind. It's not as if it is flying along and suddenly dropped into a headwind or tailwind.

This is of course for the basic case where the wind isn't changing over time or altitude. If there's a sudden change, sure the lift can change.

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