Once again-Lightly loaded high performance canopy issues

[billvon 3,085]

>Wouldn't a higher airspeed induce a greater airpressure within
>the cells . . .

Yes.

>which would force a greater change in airspeed (gust) to be necesary
>before a collapse could occur?

I believe the answer is no. The "air mattress effect" is a very minor one. Consider what would happen if you lose the outermost three line groups on the right side. Would the canopy keep flying along, remaining rigid? Nope, it would fold up instantly - because what gives a canopy most of its rigidity is lift acting against the lines, not the "air mattress effect."

Now, turbulence can rip the wings off airplanes, primarily because they go fast, and any given turbulence is magnified by the speed at which it is penetrated. We go a _lot_ slower (and we avoid bad weather more reliably) so we don't see turbulence as severe. I have never heard of anyone, for example, having their canopy damaged by turbulence. The lines/fabric are designed to handle several-G openings, and are very, very strong relative to what they have to be in normal flight.

However, that same turbulence, acting above the canopy, will collapse it downwards easily, which is what we call "canopy collapse." It will offer no more resistance to this than a partially inflated air mattress. Put another way, if you can fold a just-landed Jedei over with just your hand, turbulence will have no problem at all doing the same thing.

Now, increasing air pressure inside will have some effect, although small; the canopy will stay more rigid if the turbulence is sufficiently mild. But there's a second issue. As I mentioned before, apparent turbulence _increases_ the faster you go. So you have a slightly more rigid wing, but stronger turbulence. It may still collapse your canopy - but now you're dropping a lot faster when your canopy does collapse.

Brian Germain once did an experiment where he removed some of the airlocks from a canopy and flew it in turbulence. It seemed about as rigid, even though the air could now vent out of the canopy more easily. That argues that structure (including the additional nose bracing created by the airlocks) has more to do with canopy stability than pressure inside.

A long winded way of saying that I think letting the canopy fly is the best option in turbulence. If it's really bad, and the canopy is actually collapsing, 1/4 to 1/2 brakes is the best position to fly in - that's the brake setting the canopy was designed to (re)inflate in.

[AFFI 0]

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Have there been instances of swooper's canopies collapsing due to turbulence?

Affirmative

Mykel AFF-I10
Skydiving Priorities: 1) Open Canopy. 2) Land Safely. 3) Don’t hurt anyone. 4) Repeat…

[Squeak 17]

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Have there been instances of swooper's canopies collapsing due to turbulence?

Affirmative

and causing a few deaths

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