Canopy flying downwind after opening - Was: Fatality Elsinore 11/11/2009

[LongWayToFall 0]

An open canopy is likely to bring you back towards the DZ, if the jump run was going into the wind. A check of the wind strength/direction, and where he was found, could probably tell you how far away he was from the suspected jump run and exit point.

[JohanW 0]

Canopies do *NOT* steer downwind relative to the ground without control inputs. They don't know about the ground. They go anywhere.

Johan.
I am. I think.

[airdvr 197]

Actually an open canopy will fly downwind with no input.

Please don't dent the planet.

Destinations by Roxanne

[JohanW 0]

Calling John Kallend, calling John Kallend ..

I'm not getting through here.

Canopies do not know which way the wind blows relative to the ground. They drift in a moving column of air and experience relative wind only. They appear to exhibit this behaviour because everybody always aims into the wind and can only be blown offcourse towards downwind, but this is an effect of your steering only.

Maybe we can get back to the actual incident and take this discussion to the existing thread? I definitely remember this being discussed before.

Johan.
I am. I think.

[RogerRamjet 0]

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Actually an open canopy will fly downwind with no input.

Seek help or a course in aerodynamics. Can't believe anyone still believes this...

-----------------------
Roger "Ramjet" Clark
FB# 271, SCR 3245, SCS 1519

[billvon 2,400]

>Actually an open canopy will fly downwind with no input.

No, it won't. It only appears that way to people because the time they are most concerned about heading (i.e. landing) ANY turning tendency makes the canopy turn downwind. But that's because any turn at all makes you turn downwind when you are headed into the wind. If you were headed directly downwind, the same tendency would try to turn you into the wind.

[pilot-one 0]

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No, it won't

Really? I think you may need a lesson in aerodynamics as well Mr. Billvon.

Your statement would only be true in a vacuum.

[GreenLight 5]

My question would be if there was a cut on jump run or not.

Green Light
"Harry, why did you land all the way out there? Nobody else landed out there."
"Your statement answered your question."

[JohanW 0]

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No, it won't

Really? I think you may need a lesson in aerodynamics as well Mr. Billvon.

Your statement would only be true in a vacuum.

Wingsuiting in a vacuum? Now that sounds impossible as well as unhealthy.

Can we get back to the accident now? Maybe I'll start a poll in GSD to see who needs the lesson in aerodynamics ..

Johan.
I am. I think.

[copland007 0]

Another article... http://www.pe.com/localnews/inland/stories/PE_News_Local_S_webskydiver.2681a13.html

[mdrejhon 8]

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No, it won't

Really? I think you may need a lesson in aerodynamics as well Mr. Billvon.

Your statement would only be true in a vacuum.

Wingsuiting in a vacuum? Now that sounds impossible as well as unhealthy.

Can we get back to the accident now? Maybe I'll start a poll in GSD to see who needs the lesson in aerodynamics ..

Personally, I think both of you may be right...for different reasons.

To avoid putting this talk in this thread, I have created a new thread in General:
Canoping tending to turn downwind

[billvon 2,400]

>Your statement would only be true in a vacuum.

Things don't fly in a vacuum.

Airplanes don't care what the wind is doing. That's why aircraft can fly in the jet stream at a given airspeed without breaking the sound barrier (even if their groundspeed is greater than 741mph.) That's why you can fly at a groundspeed of 20kts on jump run without stalling if the headwinds are strong enough. There is no magical link between the ground and the airplane; it doesn't care what the air at ground level is doing.

[davelepka 4]

I wonder if pilot-one is really a pilot? Hopefully he's just a guy who jumps an Aerodyne Pilot.

Now Bill, there are canopies that will always fly downwind, round ones. Downwind, everytime.

[kallend 1,623]

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Canopies do not know which way the wind blows relative to the ground. They drift in a moving column of air and experience relative wind only.

Correct in a UNIFORMLY moving body of air. HOWEVER, a wind shear IS detectable by a canopy and can, at least in principle, cause it to turn.

...

The only sure way to survive a canopy collision is not to have one.

[JohnRich 4]

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Canopies do *NOT* steer downwind relative to the ground without control inputs. They don't know about the ground. They go anywhere.

With an unconscious jumper hanging limp in the harness, it might well induce a slow turn from his weight that is shifted to one side in the harness. And then with a built-in slow turn, the canopy will indeed travel in a generally downwind direction as it spirals. See the attached illustration. Thus, the canopy does "steer downwind" - i.e. it travels downwind on it's own with no input.

[Andrewwhyte 1]

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Canopies do *NOT* steer downwind relative to the ground without control inputs. They don't know about the ground. They go anywhere.

With an unconscious jumper hanging limp in the harness, it might well induce a slow turn from his weight that is shifted to one side in the harness. And then with a built-in slow turn, the canopy will indeed travel in a generally downwind direction as it spirals. See the attached illustration. Thus, the canopy does "steer downwind" - i.e. it travels downwind on it's own with no input.

That is not what I understand to be a tendency to turn down wind. The question is whether there is a bias towards pointing downwind. Kallend says wind-shear will tend to turn a canopy. Now we know that a canopy facing upwind will always turn toward downwind, and likewise a canopy facing downwind will always turn towards upwind. The real question is what will a crabbing canopy tend to do?

[JohnRich 4]

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That is not what I understand to be a tendency to turn down wind. The question is whether there is a bias towards pointing downwind.

Yes, I understand what you're saying - that's why I put "steer downwind" in quotes. I'm just illustrating how some people might be thinking about this topic, and that there might be some confusion about exactly what we're talking about. I just wanted to point out one of those confusing interpretations. If that's not the topic here, then those who thought it was, can move their thinking on to the alternative topic. I'm just helping to define exactly what definitions were working with here, if only by process of elimination.

[napalmboy 0]

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induce a slow turn from his weight that is shifted to one side in the harness.

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Thus, the canopy does "steer downwind" - i.e. it travels downwind on it's own with no input.

If there's a weight shift in the harness, that's a harness input, so you can't say that the canopy is steering anywhere on its own. If there's input, it can cause a turn. If you put a perfectly balanced weight in the harness and opened a parachute, it's going to fly straight regardless of which way the wind is blowing.

Well, the door was open...

[Andrewwhyte 1]

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If you put a perfectly balanced weight in the harness and opened a parachute, it's going to fly straight regardless of which way the wind is blowing.

I would submit that there has never been a perfectly balanced person under a parachute.

[Tolgak 0]

I'm a pilot. I can tell you that wings, when flying, are unaffected by the direction of the wind relative to the ground. They will fly the same whether you are pointed upwind or down or at an angle or whatever. The only thing that changes is ground speed.

In an ideal world, with perfectly uniform winds and a perfectly symmetrical wing with perfect inputs, a stable glider or canopy, once in full flight, will continue on its merry way through the relative wind without turning. If there is wind shear, it could turn. Turbulence could do it too.

Thar be much crap science goin' 'round.

Dropzones are terrible places for inspiration. What does one think when one looks up for a sign only to see a bunch of people falling?