Angle of attack vs collapse of a canopy?

[AndyMan 7]

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if turbulance is bad enough to collapse a [inset non airlock canopy name here] I am not sure any airlock canopy (jedei, vengence, lotus, samurai) would fly through it. I havent flown one, but at best, i think thet would help in slightly marginal condition, but not in "shit hitting the fan" conditions.

From what I understand Airlocks will recover from the turbulance that much quicker because it's going to keep its' shape. You're still going to smack in if you catch a downdraft, but if the downdraft doesn't smack you in, you'll be in a better position to recover with an airlocked canopy - because it's still in the correct shape. It didn't collapse, it just rode the wind in it's inflated shape.
_Am
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[rendezvous 0]

Are there any books that cover aerodynamics as applied to
ram air parachutes. I would be quite interested in reading about it. May be a simplified version which is still technical enough.

[billvon 2,450]

>You need to do what aircraft do in turbulent air: INCREASE SPEED.
Uh, do you really exceed structural cruise in turbulent air? I've always slowed down below structural cruise in bumpy air - on the planes I fly, the POH says to.
-bill von

[billvon 2,450]

>I wonder what the IDEAL turbulence busting canopy is?
From best to worst from my experience:
Triathalon 135
Jedei 120
Sabre 150
Safire 129
PD190
Nova 150
-bill von

[rhino 0]

Yeagh.. The Triathlon is pretty shit hot in bumpy air..
Semper Fi .....
http:// www.aahit.com

[SkydiveMonkey 0]

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Nova 150

Weren't they the canopies that kept collapsing all the time and had to be withdrawn?
I'm not crazy - I'm a Skydiver

[markbaur 0]

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Uh, do you really exceed structural cruise in turbulent air? I've always slowed down below structural cruise in bumpy air - on the planes I fly, the POH says to.

When you slow down, you increase the angle of attack, which in turn makes it more likely the wing will stall in a vertical gust. In an airplane cruising at altitude, that's a good thing, because the alternative is bent metal. But with parachutes, we don't exceed the "structural cruising speed," so a lower angle of attack and faster speed can be used to make a canopy less likely to stall or collapse.
Mark

[diverdriver 5]

No, you are misunderstanding what I'm saying. On approach you have approach speed. In turbulent air you usually increase that speed by half the gust factor. That's been in every POH I've read too. I'm sure you've heard of that. The old teaching in turbulence and canopies was to ride half brakes. But, with modern canopies this can put you dangerously close to a stall. Hence, my comments on going at full flight in turblent air under canopy. Would you agree with that?
Chris

[airann 1]

#1 I am not reading all this cause I am an idiot and have no idea of what you say.
#2 Caopy shyt has happend to me TWICE
July 28th, landed in turbulance and high winds sorta..right nest to tall ass pine trees. 1st camera jump == 4.5 fractures, knee blown out, and some other stuff.
LAST Sunday- 21-23 mph ground winds. Jumped on 5 min call, put on rig over clothes. (explains my freeflying)..... =CAMERA HOUSING IS CRACKED UP, F**k
Concussion mild, neck compression, right knucke ding, right lower leg scraped and bruised, left ankle sprain, blah , blah...
I pulled, I started to the dz, I was hauling ass. I started to turn to the landing area and I sailed passed it losing altitude like a cemet truck. See the attached from my camera. Most are taken 5 frames apart then ONE frame apart, I felt it, just like July 28th and thats it, you are going in and thats the end of that. You will either get hurt or only damaged, but it could be bad. Thats all you think about.
Look at my helmet!
Dnag it you cant see anything good from this - I will fix it.
I have already fixed the idea of wind and building turbulance compounded by plain ole high windage turbulance. I will likely still jump in winds. I can back up and land off anyeay. But... you can see the results. Note* there are exceptions to stuff I will jump in. But then I did jump in hail...... No really, I am ok, and I dont jump in just anything.... I will and do pull off loads.
Ann ~ www.AirAnn.com
Levin in RW suit.. I have pictures!!!

[billvon 2,450]

>On approach you have approach speed. In turbulent air you usually increase that
>speed by half the gust factor. That's been in every POH I've read too.
Yes. So I guess the question becomes - what's more dangerous? The possibility of a stall due to turbulence (higher airspeed would help) or the possibility that increasing your turbulence penetration speed might result in bent metal, or in this case collapsed fabric? In that case a _lower_ airspeed would help, since turbulence seen by the canopy decreases with speed.
>Hence, my comments on going at full flight in turblent air under canopy.
>Would you agree with that?
It would depend on the canopy. On a larger canopy I'd go to 1/4 to 1/2 brakes, because they are nearly bulletproof in that configuration (less likely to collapse, faster reinflation if they do collapse) and they see less turbulence. In addition, if they do stall near the ground, that's a good position to land in (1/2 brakes.) On a smaller canopy that cannot survive a stall at low altitudes (like my Safire) I'd stay at full flight.
-bill von

[billvon 2,450]

>Weren't they the canopies that kept collapsing all the time and had to be withdrawn? (Nova)
Yeah, but I still got one, less than 100 jumps! Anyone want to buy it? Might make a good cutaway canopy - and it did land better than any other square I've ever jumped.
-bill von

[rhino 0]

Which of the 2 in this picture are more apt to handle turbulence? The one flying into the wind or the one flying down?
Semper Fi .....
http:// www.aahit.com

[HeatherB 0]

>Seriously.. If you were in the air and the shit hit the fan, what would you like to be flying over your head??
A Lotus!
I respect the limits of any canopy and won't jump in questionable conditions no matter what I'm jumping.
That said, I love how airlocks feel above my head...I have no desire to go back to an open-cell.
Blue Skies!
Heather
http://www.skydivewings.com

[diverdriver 5]

Rhino, you still don't understand how air flows around a wing. Your drawing is incorrect. The wind you should draw is opposite the direction of flight. It has nothing to do with the flow of air over the ground.
Chris

[rhino 0]

Draw one for me and tell me what you mean?
I was just quick sketching it as an example.. I'm curious as to air in the inlets and over/under the wing...
Semper Fi .....
http:// www.aahit.com

[billvon 2,450]

>Which of the 2 in this picture are more apt to handle turbulence? The one flying
> into the wind or the one flying down?
Neither one. As drawn, both will collapse, because they have negative angles of attack. No ram-air canopy can sustain negative angles of attack - that's one reason canopies collapse to begin with.
However, the situation you have drawn isn't a possible steady state condition. In a glide, a canopy has a positive angle of attack. The typical 4:1 glide gives you about a 14 degree angle of attack, and that's reduced by the trim angle of the canopy. The net result is a relative wind that seems to be coming from in front of, and slightly below, the chord line of the wing.
-bill von

[diverdriver 5]

Unfortunately I don't have the drawing ability on my computer. What you need to imagine is the air flowing around the canopy as the canopy passes through it. The angle it has with respect to the ground has no baring. So, when you draw your wind parallel with the ground hitting the top of the canopy it is not true to what is happening. Let me try and search the web for a picture of an aircraft wing.
Chris

[rhino 0]

so the forward speed of a canopy makes up for the steeper dive angle flying into a strong wind? Still seems like wind coming from in front of you could be dangerous if your canopy is trimmed at a steep angle. Is there a optimum glide angle for safety, and penetration in full flight? All the different inlet shapes, airlocks, makes it hard to figure out. I'm trying to understand the method to the madness.
Semper Fi .....
http:// www.aahit.com

[skycat 0]

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Might make a good cutaway canopy

Shhhhhhh.....Don't say that so loud or the current pile of canopy's in Derek living room may increase by one.

[diverdriver 5]

Ok I'll try to attach some good diagrams here. We're going to have to do a little imagining since I can't turn the picture the direction I want.
This one shows basic airflow over the wing. Now, if you turn the wing from the horizontal such as a canopy is trimmed down with respect to the horizon the airflow will be identical.

[quade 3]

Also see THIS discussion about angle of attack.
quade
http://futurecam.com

[billvon 2,450]

>so the forward speed of a canopy makes up for the steeper dive angle flying into
>a strong wind?
Winds simply do not matter. Again, you could get out of the plane at 13K, open your parachute, and fly around even if the uppers are 100kts. The winds won't "push on top of the canopy." If there's no turbulence, you won't even notice anything unusual. You can fly downwind, upwind, crosswind - all you will ever feel is your canopy's usual 20kts (or whatever) of airspeed hitting you from the same angle it always does.
-bill von

[diverdriver 5]

Now, here is a diagram of a wing with airflow. Shows the relative wind. This wing is climbing so what we need to do is turn it down and imagine it descending. Keep the horizon line where it is and just tilt the whole rest of the picture down so the wing is in a descending attitude. The airflow lines will be identical as they are now. Does this help finally? See how your picture does not show relative wind?
Now, let's talk turbulence. You might be saying, ok, but what about a rotor. My question still stands. Does a canopy trimmed down fly better in turbulence. The answer is, what kind of turbulence? Turbulence can come from any direction at any speed. So, no canopy (I think this has been said before) is capable of cutting through all turbulence. Some turbulence will collapse ANY canopy.
Hope this is helping.
Chris

[billvon 2,450]

>Shhhhhhh.....Don't say that so loud or the current pile of canopy's in Derek living room may increase by one.
Don't worry, I wouldn't even give that canopy away. I'd feel really bad to hear about someone getting killed under it, so I think it will stay in the gear room until the next time _I_ have to do an intentional cutaway.
-bill von

[psw097 0]

Try this link: http://www.afn.org/skydive/sta/highperf.pdf
It is a bit long for a quick read but very well written. Some of the diagrams quickly explain AOA, reletive wind, etc. I did not have time to extract the diagrams only. Plus, I think the whole thing is worth the read.
Paul Webster