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Wake turbulence and the Velocity

 

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phoenixlpr  (D 3049)

Mar 13, 2012, 12:31 PM
Post #26 of 43 (1053 views)
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Re: [wwelbon] Wake turbulence and the Velocity [In reply to] Can't Post


Nice example.


Premier billvon  (D 16479)
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Mar 13, 2012, 12:40 PM
Post #27 of 43 (1048 views)
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Re: [cpoxon] Wake turbulence and the Velocity [In reply to] Can't Post

>Full face helmets and AADs are mandatory for big ways. Why not specified wing loadings?

There were specified wing loadings for the last World Team event but they were largely ignored. (I up sized, although mainly for my own safety.)


Premier billvon  (D 16479)
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Mar 13, 2012, 12:41 PM
Post #28 of 43 (1047 views)
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Re: [Rdutch] Wake turbulence and the Velocity [In reply to] Can't Post

>Are you really comparing a Nova to the velocity? Velocities have a long history of
>being a good canopy . . .

They both have stability problems. The Nova was worse, although I have a Nova 150 that I never had any trouble with (and was the best flying square canopy I ever jumped.)

>Bring your pilot 150 and lets have a lift contest, Ill stay with you all day.

OK, next time we're at the same DZ.


theonlyski  (D License)

Mar 13, 2012, 6:11 PM
Post #29 of 43 (1009 views)
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Re: [billvon] Wake turbulence and the Velocity [In reply to] Can't Post

In reply to:
They both have stability problems. The Nova was worse, although I have a Nova 150 that I never had any trouble with (and was the best flying square canopy I ever jumped.)

I don't know, my 74 Nova handled pretty well, little sloppy but not bad.


DaVinciflies

Mar 13, 2012, 6:22 PM
Post #30 of 43 (1005 views)
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Re: [billvon] Wake turbulence and the Velocity [In reply to] Can't Post

In reply to:
>Are you really comparing a Nova to the velocity? Velocities have a long history of
>being a good canopy . . .

They both have stability problems. .

Do you have data to show that Velos are less stable than other canopies?

I have not flown one but the guys I know who do swear by them in less than favorable winds.


Premier billvon  (D 16479)
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Mar 13, 2012, 7:09 PM
Post #31 of 43 (981 views)
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Re: [DaVinciflies] Wake turbulence and the Velocity [In reply to] Can't Post

>Do you have data to show that Velos are less stable than other canopies?

Data? No. But a handful of videos showing collapses - some recoverable, some leading to cutaways. And a fair number more of stories about wake turbulence.

Keep in mind that Glide Path claimed there was no data to prove that the Nova was less stable either; they said any canopy could collapse (which is certainly true.) But they did seem a lot worse than other canopies.


Premier billvon  (D 16479)
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Mar 13, 2012, 7:10 PM
Post #32 of 43 (980 views)
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Re: [theonlyski] Wake turbulence and the Velocity [In reply to] Can't Post

>I don't know, my 74 Nova handled pretty well, little sloppy but not bad.

Yeah, mine never had a problem either. But I was pretty careful about the conditions I jumped it in.


theonlyski  (D License)

Mar 13, 2012, 7:29 PM
Post #33 of 43 (970 views)
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Re: [billvon] Wake turbulence and the Velocity [In reply to] Can't Post

In reply to:
>I don't know, my 74 Nova handled pretty well, little sloppy but not bad.

Yeah, mine never had a problem either. But I was pretty careful about the conditions I jumped it in.

I never had to jump it, just push it and pop the clutch.


(This post was edited by theonlyski on Mar 13, 2012, 9:43 PM)
Attachments: P1010018 (Medium).JPG (161 KB)


phoenixlpr  (D 3049)

Mar 13, 2012, 11:59 PM
Post #34 of 43 (925 views)
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Re: [DaVinciflies] Wake turbulence and the Velocity [In reply to] Can't Post

In reply to:
In reply to:
>Are you really comparing a Nova to the velocity? Velocities have a long history of
>being a good canopy . . .

They both have stability problems. .

Do you have data to show that Velos are less stable than other canopies?

I have not flown one but the guys I know who do swear by them in less than favorable winds.

Check the pilot's input.
This can happen with any other canopy in that situation.


Pulse  (D 16387)

Mar 15, 2012, 7:21 PM
Post #35 of 43 (817 views)
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Re: [billvon] Wake turbulence and the Velocity [In reply to] Can't Post

What do we know about turbulence?

1 - Speed increases pressure and possibly makes the canopy more resistant to turbulence induced collapse. The opposite is true with less speed.

2 - The higher loaded you are, the worse the results of a collapse are going to be.

I'm with the not believing it's Velocity issue crowd.

I had a Jonathan 136 collapse on me from wake turbulance at 3,000 feet. Half of the parachute was folded under and in the lines. It was 'violent' and had I been jumping something smaller it would've been even more so.

I got to test this theory years later on my Velo. Yes, it rocked me when I flew in wake turbulence. I was doing this on purpose, so I was very high. But in both instances I was flying in deeper than half brakes.

My conclusion is that flying any small canopy in deep brakes in turbulent air is risky. Even more so at low altitude. One reason I really don't care for the deep brakes to front riser method for setting up a swoop.

As far as the Velocity. Doesn't this canopy hold a good portion of the market? Meaning there's a lot of them out there. So in the few instances that this has happened the chances are probably pretty good that it's a velo. A friend of mine did have an FX collapse on him while in the pattern that resulted in line-twists. This was some 10-12 years ago.


Premier billvon  (D 16479)
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Mar 16, 2012, 12:32 PM
Post #36 of 43 (753 views)
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Re: [Pulse] Wake turbulence and the Velocity [In reply to] Can't Post

>1 - Speed increases pressure and possibly makes the canopy more resistant to
>turbulence induced collapse.

Speed also increases turbulence and makes the canopy less resistant to turbulence and collapse.

>2 - The higher loaded you are, the worse the results of a collapse are going to be.

Agreed.


Pulse  (D 16387)

Mar 16, 2012, 10:57 PM
Post #37 of 43 (710 views)
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Re: [billvon] Wake turbulence and the Velocity [In reply to] Can't Post

[replySpeed also increases turbulence and makes the canopy less resistant to turbulence and collapse.
?????

Are you talking wind speed?
A canopy traveling faster doesn't create more turbulence. If you're talking wake turbulence behind it, high AoA's (slow speed) create more turbulence.

Tell me if I'm reading you wrong.


5.samadhi

Mar 17, 2012, 4:00 AM
Post #38 of 43 (693 views)
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Re: [Pulse] Wake turbulence and the Velocity [In reply to] Can't Post

In reply to:
What do we know about turbulence?

1 - Speed increases pressure and possibly makes the canopy more resistant to turbulence induced collapse. The opposite is true with less speed.

2 - The higher loaded you are, the worse the results of a collapse are going to be.

I'm with the not believing it's Velocity issue crowd.

I had a Jonathan 136 collapse on me from wake turbulance at 3,000 feet. Half of the parachute was folded under and in the lines. It was 'violent' and had I been jumping something smaller it would've been even more so.

I got to test this theory years later on my Velo. Yes, it rocked me when I flew in wake turbulence. I was doing this on purpose, so I was very high. But in both instances I was flying in deeper than half brakes.

My conclusion is that flying any small canopy in deep brakes in turbulent air is risky. Even more so at low altitude. One reason I really don't care for the deep brakes to front riser method for setting up a swoop.

As far as the Velocity. Doesn't this canopy hold a good portion of the market? Meaning there's a lot of them out there. So in the few instances that this has happened the chances are probably pretty good that it's a velo. A friend of mine did have an FX collapse on him while in the pattern that resulted in line-twists. This was some 10-12 years ago.
You forgot to mention the planform which will greatly effect the result of turbulence. Its funny that you mention that Jonathan because when I read this topic I remembered how my Jonathan was particularly suceptible to collapse Unsure


Premier billvon  (D 16479)
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Mar 17, 2012, 10:11 AM
Post #39 of 43 (650 views)
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Re: [Pulse] Wake turbulence and the Velocity [In reply to] Can't Post

>A canopy traveling faster doesn't create more turbulence.

Correct. But a canopy traveling faster SEES more turbulence.

Turbulence isn't static; it's not just sitting there, waiting. All turbulence is is moving air. Wind is air all moving in the same direction; turbulence is wind that's moving in different directions depending on where you are. If you are standing still with respect to the average wind you feel very little turbulence. If you're moving you feel it as you move from one area of wind to another. The faster you go, the faster the winds change direction and the more turbulence you feel.

When airplanes encounter severe turbulence they slow down to avoid overstressing their flight surfaces. The slower the aircraft goes, the less change it sees per unit of time, and the less force that wind can apply to the aircraft. However, slowing down too much (say to near stall) also isn't a good idea - if you are 10 knots above stall, then flying into a region with a 12 knot gust from behind you will stall the airplane.

Canopies can't change their airspeed without distorting their airfoil shapes, and most modern canopies are most stable either at full flight or with very slight brakes applies. Thus it's generally better to be flying at full flight (or close to it.) But flying faster to "keep your wing pressurized" and/or "cut through the turbulence faster" doesn't work.


pchapman  (D 1014)

Mar 17, 2012, 10:58 AM
Post #40 of 43 (642 views)
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Re: [billvon] Wake turbulence and the Velocity [In reply to] Can't Post

Still, a given size of gust will cause a lower change in angle of attack for a wing at higher speed. In that sense one can 'cut through' turbulence -- less likely for a down gust to unload the front of the wing and collapse it.

On the other hand, more speed gives less time for the canopy to adapt to a new angle of attack and thus can 'get hit' by turbulence if flying faster instead of having time to react and adapt to the new conditions if flying slower. Which could be good or bad depending on the situation. (Eg if you get hit by some idealized upwards gust before hitting a following downwards gust -- the down gust isn't as extreme a change if the wing hasn't already reacted to the up gust. In that particular situation, more speed is again better. But if it is a down gust followed by more down gust, the wing moving with the conditions can be better.)

I think it will depend on the exact natures and scale of the turbulence, which factor wins out. Still, I think extra speed tends to win out as better. (At least as long as one doesn't actually have a collapse -- then slower can be better in many circumstances.)


Pulse  (D 16387)

Mar 17, 2012, 5:19 PM
Post #41 of 43 (611 views)
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Re: [billvon] Wake turbulence and the Velocity [In reply to] Can't Post

In reply to:
>A canopy traveling faster doesn't create more turbulence.

Correct. But a canopy traveling faster SEES more turbulence.

You're right. We're on the same page. I just wanted to be clear as to what you were saying.


Pulse  (D 16387)

Mar 17, 2012, 5:32 PM
Post #42 of 43 (608 views)
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Re: [5.samadhi] Wake turbulence and the Velocity [In reply to] Can't Post

[replyYou forgot to mention the planform which will greatly effect the result of turbulence. Its funny that you mention that Jonathan because when I read this topic I remembered how my Jonathan was particularly suceptible to collapse Unsure
Given that ellipticals are a bit more 'unstable', I assume you mean the results of turbulence can be more dramatic if you're not on it right away. I don't know how much planeform lends a canopy to be more prone to collapse or not.

I didn't feel my Jonathan was any more prone to collapse. I only had the one instance and that was the result of a few factors. Mostly my fault.

Just a point. There is a difference between collapsing and just getting blown around by turbulence. Most 'collapses' I've heard people talk about are usually the latter when I've seen them. That's not to say it matters much to the person under canopy, Since both experiences can be iffy. But all out collapses are pretty rare all things considered.


Premier billvon  (D 16479)
Moderator
Mar 17, 2012, 6:22 PM
Post #43 of 43 (595 views)
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Re: [pchapman] Wake turbulence and the Velocity [In reply to] Can't Post

>Still, a given size of gust will cause a lower change in angle of attack for a wing at
>higher speed.

But a greater force. Which is why aircraft generally slow down when encountering turbulence.

Aircraft, of course, have an advantage that we don't - their wings are rigid, and even the weakest rigid wing can withstand some negative G's. Which is why it's pretty important for us to avoid negative loading.


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