Carving and Wind

[skynole 0]

This past weekend I had an incident that spooked the shit out of me...

I set my line to come at the beer line at about a 45 degree angle, planning to carve past the beer line and then cross back over it into the landing area at about a 45 degree angle...basically a long, gradual ~120 degree carve, which I have done this exact swoop many times without incident.

That day, the winds were about 12-15 knots directly crosswind to the beer line - heading from the landing area to the hangar. I'm about halfway through the carve, putting me facing perpendicular to windline, and all of a sudden I lose all lift! I get off the rears and gave the toggles everything I had and just avoid femuring, but get slammed to the ground pretty good.

It was not due to a low turn, actually I was a bit high. It was not a rear riser stall...I have done this many times up high and unfortunately once during a swoop, and it's very distinctive feeling. Plus, I didn't have much input on the rears during the carve.

I have never experienced anything like this before...it was like my canopy just quit flying. A very experienced skydiver/HP pilot with over 5000 jumps watched the whole thing and he wasn't sure what happened either. He said that it looked like the bottom just dropped out from under me.

The only conclusion we could come to was that the point that this happened, I was at the steepest point in the carve, which exposed most of the top-skin to the crosswind. This puts the lift vector mostly in direct opposition with the wind vector, in which the wind vector won!! My question is this why this happened? Was the lift force not able to overcome the wind force?

[Hooknswoop 19]

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I set my line to come at the beer line at about a 45 degree angle, planning to carve past the beer line and then cross back over it into the landing area at about a 45 degree angle...basically a long, gradual ~120 degree carve, which I have done this exact swoop many times without incident.

That day, the winds were about 12-15 knots directly crosswind to the beer line - heading from the landing area to the hangar. I'm about halfway through the carve, putting me facing perpendicular to windline, and all of a sudden I lose all lift! I get off the rears and gave the toggles everything I had and just avoid femuring, but get slammed to the ground pretty good.

Which is why you shouldn't cross the beer line since you can't guarantee you can re-cross it. One side of the beer line is for skydivers, the other for spectators.

Derek

[diablopilot 2]

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The only conclusion we could come to was that the point that this happened, I was at the steepest point in the carve, which exposed most of the top-skin to the crosswind. This puts the lift vector mostly in direct opposition with the wind vector, in which the wind vector won!!

I don't buy it. I did the exact same thing this weekend (without the crash) and I will postulate that the crash came from your visual being different because of the "push" the wind was giving you.

Say the wind is blowing at a 90 degree angle to the ground. As you carve the canopy over, the only thing that will change with windspeed is your ground track. The canopy doesn't know a difference.

Either your visual perception was confused causing you to make an error, or some unknown force interupted your landing such as a thermal, pocket of turbulance, or dust devil. Any objects up wind to produce a rotor effect?

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You're not as good as you think you are. Seriously.

[ManBird 0]

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The only conclusion we could come to was that the point that this happened, I was at the steepest point in the carve, which exposed most of the top-skin to the crosswind. This puts the lift vector mostly in direct opposition with the wind vector, in which the wind vector won!! My question is this why this happened? Was the lift force not able to overcome the wind force?

I vote yes.

"¯"`-._.-¯) ManBird (¯-._.-´"¯"

Click

[headoverheels 334]

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The only conclusion we could come to was that the point that this happened, I was at the steepest point in the carve, which exposed most of the top-skin to the crosswind.

This make no sense, as the canopy doesn't "know" that it is drifting with the wind. One thing certainly changes with wind, and that is one's perception of the correct place to start the turn, and how steep to turn. If one did the same carve as on a no wind day, they would find themselves blowing down wind. They might mistakenly think they need to give more input to turn at their standard rate, but might actually be turning/diving much steeper.

Another possibility is a sudden gust or lull in the wind, or turbulence from trees or buildings. It could also be wind shear, where you had more wind at the higher altitude, and less in the last couple of hundred feet.

Do I understand correctly that you were using rear risers to make the carve? From your comment about "getting off the rears" it seems so.

[skynole 0]

I understand what you are saying and you are 100% correct...but that does not answer my question. The intention of the post wasn't to start a flamefest about crossing the beer line.

FYI, there is about 75ft between the beerline and the closest obstacle and there were no spectators in the area...slow day at the DZ and it was the last load of the day. Plus I barely cross the beerline, maybe 10ft at most.

Whether I had stated that I crossed the beer line or not is completely irrelevant to the question I have posed.

Yes, in hindsight I should not have tried that maneuver next to the beer line. I was just using that as a point of reference for my carve.

So please, unless you have something to say directly related about the question I have posed in my original post, please refrain from the BS flaming. Also, this is not directed at you HooknSwoop, but just a general comment for everyone to please respect.

Thanks.

[diablopilot 2]

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I vote yes.

You guys are believing in the same "phenomena" that novice skydivers try to believe in.

The "side gust".

"I caught a side gust and it made me crash."

Not.

Providing for a continuous air mass moving at the same velocity, the canopy will fly no differently in a high wind vs. low wind. Perception of what the canopy is doing IN RELATION TO THE GROUND is what will make things seem different. The canopy will not be doing anything different IN RELATION TO THE AIRMASS. Turbulent conditions which are often a function of higher winds will change how the canopy flies.

Lesson learned? Don't be as aggressive in turbulance.

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You're not as good as you think you are. Seriously.

[Hooknswoop 19]

No worries, had to say it.

The wind, in a steady state, doesn't hit the top skin counter-acting your lift vector. You are flying your canopy within a moving air mass. Look up the thread about 'Does a canopy dive more in wind'. Some people believe(d) that when diving a canopy when it is windy, the wind hits the top skin of the canopy, destroying lift, causing it to dive more. This simply isn't true, for a steady state wind.

For turbulence, gusts, etc, the canopy may dive more or may dive less.

Same thing here, your perception of what the canopy is doing is different from what he canopy is actually doing because you are referencing the ground, but the canopy is flying through (flying in reference to) a moving air mass. To get the canopy to track 90-degrees to the wind across the ground, the canopy must be actually crabbing into the wind. Your perception: the canopy is flying 90-degrees to the wind (ground reference). Canopy’s perception; it is flying through the air straight ahead (air mass reference)

A had gust of wind may have caused it i.e. turbulence, but if the wind was steady, then it wasn’t the culprit. Most likely you had to turn away from the beer line harder than normal through the air in order to get the same ground track as on a light-wind day. This required more energy and a higher angle of attack to get the harder turn resulting in a stall.

Derek

[skynole 0]

Yeah I didn't buy it at first either because it didn't make sense, but we couldn't really think of why this happened.

Our DZ has nasty rotors coming off the trees from time to time, but it's pretty obvious when you hit one...and it didn't feel like I hit one. Like I said I was in the middle of my carve and everything seemed familiar/normal and then the bottom just dropped from under me, no warning.

Headoverheels - yes I was using rears and harness in the carve.

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Lesson learned? Don't be as aggressive in turbulance.

Definitely.

[ManBird 0]

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You guys are believing in the same "phenomena" that novice skydivers try to believe in.

You're right. I misunderstood what was being said here. I though he was describing rotors, which can, indeed, drop you through dead air.

"¯"`-._.-¯) ManBird (¯-._.-´"¯"

Click

[diablopilot 2]

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Most likely you had to turn away from the beer line harder than normal through the air in order to get the same ground track as on a light-wind day. This required more energy and a higher angle of attack to get the harder turn resulting in a stall.

Exact-o-mund-o!

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You're not as good as you think you are. Seriously.

[skynole 0]

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A had gust of wind may have caused it i.e. turbulence, but if the wind was steady, then it wasn’t the culprit. Most likely you had to turn away from the beer line harder than normal through the air in order to get the same ground track as on a light-wind day. This required more energy and a higher angle of attack to get the harder turn resulting in a stall.

But I didn't do anything different than I usually do. If anything I was giving less input, just over longer period of time, because I had come out of my turn a bit high so I started my carve higher and just more gradual (does it make sense what I'm trying to say?)

I must have hit a pocket of turbulent air and the only affect I felt was the loss of lift. I didn't feel any "bumpiness" or surging....maybe because of the airspeed I had???

It was definitely turbulent that day, but I hadn't felt any under 1500'.

Oh well, lesson learned and I didn't break myself. Thanks for your guys responses.

[jmfreefly 0]

You are most likely still within the 'rotor zone' of the obstacle. And no, you may not have registered the 'bumpiness' when going into a downdraft, especially while the canopy is canted over.

Usually, the bumpiness is you getting abruptly stopped by your harness going into or out of an updraft or downdraft. If you are pulling g's with lift almost perpendicular to the downdraft, then you would most likely miss the 'bump', because the vector is not what you usually associate with bumpiness.

Just my opinion at least.

Carving and updrafts/downdrafts don't make for a good combination.

j