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Pasha

Canopy collapse

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It was my understanding that a canopy at a higher wingloading was more able to fly through turbulance then a lightly loaded canopy. Am I wrong?



Fly through it faster, yes, but when it is encountered in close proximity to the ground, then there is nothing you are going to do about it. At Raeford we have "the dragon". It is a phenomenon that happens when the wind blows over the tops of the tall trees in the packing area and over the restaurant. Rotors off the tops of the trees have grabbed parachutes and dropped people 50 feet to the ground before, so we have our beer line out far enough that most jumpers will not be affected. There is a similarly tall set of trees on the other side of the dropzone next to Gene Paul Thacker's house, but people don't land over there for fear of being shot by Miss Billie or GPT. ;)

Chuck

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I saw something pretty ugly this weekend but luckily nothing happened. Two jumpers from another DZ came and on their first jump one of them was chasing the other under canopy. At about 20 feet off the ground the canopy behind the other one lost air behind the canopy in front it and basically collapsed, did a 90 degree turn and it gained air again right before impact. She was alright but it was not a pretty sight and our S&TA had a little talk with them afterwords.[:/]

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yes, most high performance canopies are far less effected by minor turbulence than lightly loaded squares.

primarily because they are faster and more efficient.

sincerely,

dan <><>
Daniel Preston <><>
atairaerodynamics.com (sport)
atairaerospace.com (military)

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I saw a major collapse on a canopy once. A lightly loaded Sabre was hooked at about 1,000 feet and it collapsed and spun into severe twists. The guy chopped it and did not pull the silver and his cypres fired around 700 feet. His main landed on a power line and it started a brush fire. All the power in the vicinity was knocked out. The guy landed in the fire and burned his reserve canopy. Guy Manos (who filmed the movie Cutaway) was there and the guy came walking back to the hanger with his burnt reserve and his eyes as big as a deer in headlights. Guy Manos looked at him and said, “If I go get my camera can you do that again?” We all busted out laughing and the guy nearly pissed his pants.

Question is is it that easy to collapse a lightly loaded canopy like that?

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It was my understanding that a canopy at a higher wingloading was more able to fly through turbulance then a lightly loaded canopy. Am I wrong?



Fly through it faster, yes...



Do you think that wingloading or canopy type is more important in resisting turbulence? I've noticed that my (approximately 1.5 loaded) Stiletto appears to be far more susceptible to turbulence than my (approximately .65 loaded) Blackjack. I had always thought this was likely because the Blackjack was designed with stability as a base line parameter. What do you think?
-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com

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yes, most high performance canopies are far less effected by minor turbulence than lightly loaded squares.

primarily because they are faster and more efficient.



Uh . . . I guess it depends on your definition of "far less effected".

If by "far less effected" you mean that the skydiver will be less likely to suffer an injury, then I question that definition being applied to "high performance canopies".
quade -
The World's Most Boring Skydiver

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I think the big canopy is less danger for turbulence conditions, because lower speed in all conditions of the big canopys, and also the big canopy is better if the pilot have less experience.
But I think the um HP canopy is better for strong winds and turbulence conditions when driven for a good and experienced pilot and if the canopy is good and reliable.
I jump in demo jumps for tight places with accuracy Parafoil 252 light loaded and have no problems with turbulence conditions but I have problems with strong winds because the parafoil don't move forward.
With my atair HP canopys 75, 85 and 120 I don't have problems with strong winds and turbulences.
In my opinion the reasons because the HP canopys is more danger in turbulence conditions is:
Bad design of the canopy
Bad pilot control canopy technique and experience
Fast natural speed in all conditions of the HP canopys
Driving the HP canopy with lower horizontal speed in flying. It is good for student canopys and old and classic 7 cell canopys (driving the canopy with 20 to 50 % brake in turbulence conditions) but definitively it is poor and danger technique for HP or intermediate canopys.

Roq

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hey quade,

i was referring to "minor" turbulence whereby no accident resulted. definately a faster canopy can inflict more injury when crashing than a slower canopy, but also there is a point that most canopy collapses are lightly loaded canopies (many times in partial brakes) that are strongly effected by turbulence that higher wingloaded canopies dont even feel.

i think roq summed up everything pretty well.

sincerely,

dan
Daniel Preston <><>
atairaerodynamics.com (sport)
atairaerospace.com (military)

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I'll agree that a lightly loaded canopy will almost always feel as if it is being affected more than a more highly loaded canopy.

I was only objecting to the somewhat (and I'm sure inadvertantly) misleading phrasing you were using.
quade -
The World's Most Boring Skydiver

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The best analogy I've heard when talking about canopies and turbulance is one of airplanes and mass. 707s and such usually aren't effected too terribly much in semi-turbulant conditions near the ground, where as a c-172 would be tossed around like a rag doll. Similar with canopies, large, faily loaded canopies would be the best (i.e. Tandems) for handling turbulance, although something at a higher loading would be able to fly through the turbulant air with less of a problem then a lightly loaded canopy.

That make sense or am I off base?
--"When I die, may I be surrounded by scattered chrome and burning gasoline."

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Just for reference:
A B 707 has a gross wgt of 160,000lbs and a wing area of 2402 sq ft for a wing loading of 66.61 lbs/sq ft.
A C 172 has a gross weight of 2200 lbs and a wing area of 175 sq ft for a wing loading of 12.57 lbs/sq ft.
That being said, the analogy to parachute wing loading doesn't really work. It takes a hell of a lot more turbulance to make the boeing bounce around than it does the cessna. Blow on a peice of paper then blow on your monitor. Which one moves?
The jumper weight differences in contrast are almost negligible. If you're 200lbs out the door, it probably won't matter if you're flying a 90 or 200 sq ft canopy, you're going to get bounced around in the same turbulence. About the only difference I can see is that with the smaller parachute you'll get through it quicker (or get screwed into the ground quicker).
Of course, it's 3am and I may not know what the hell I'm talking about.

Lee

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But remember.
The 707 have: high wing load, high speed flying and landing, Big mass

The cessna 172 have: Low wing load, Low speed flying and landing, Lower mass

In gross analogy the 707 flying more close to HP canopy than big canopy

In my opinion the best gross comparison is:
Big canopys: lower loads, lower mass and lower speed flying and landings as like a Antonov AN2.
Small Hp canopys: high load, lower mass, high speeds flying and landings as like a style competition planes like a Sukoy or Pits

Roq

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hi aggie,

not sure you analogy quite works.

your 707 has drastically higher wingloading and speed than the 172.

the difference is weight from a boat canopy to a pocket rocket is only a few pounds. this can be discounted, inertia is mass times your speed. lightly loaded canopies have no speed. lift, skin tension, cell pressure, etc... are all proportional to speed.

tandems should not be much better than a lightly loaded sport in turbulence, yes, they have a large wingspan but primarialy i would say the difference in turbulence from a lightly loaded sport canopy, is probably the diference between a highly experienced pilot on the tandem and a not so experienced pilot on the lightly loaded sport canopy.

sincerely,

dan<><>
Daniel Preston <><>
atairaerodynamics.com (sport)
atairaerospace.com (military)

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Interesting discussion, though it all turned to the subject of canopy being affected by turbulence. However my question was about canopy collapsing because of the actions of the pilot. In the case I mentioned in the 1st post the pilot (presumably) was trying to escape hitting the fence which was in front of him. He did something to the canopy (heavily loaded eliptical) which resulted in its collapse, however it was not a low turn. My question was what action can result in such a bad outcome

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Here my opinions for don't collapse HP canopys:

Don't make radical or brutal inputs in your canopy in all conditions
Don't use canopy with bad design
Don't use new canopy without technical background or recognized technical quality
Don't use poor and inadequate technical pilot canopy control
Don't use HP canopys high loaded when you have low technique and or low experience
Keep the fast natural horizontal speed in all conditions of the HP canopys and intermediate canopys
Don't driving HP canopy with brakes for lower horizontal speed in flying.
Don't fly or landing to the crossed wind
Don't fly or landing close to natural or artificial obstacles, elevations or other canopys
Don't jump when have bad meteorological conditions

Roq

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-You can stall most canopies simply by holding both toggles down fully for too long. Then it will collapse and fall out of the sky but it will re-inflate if you have enough altitude. Generally, it happens gradually (the canopy has to lose some forward speed first)
-On any canopy, if you fly it as slow as possible without stalling it I suspect it will take very little bad air to collapse it. Some canopy whizz might correct me here if I'm wrong.
-On some canopies (not necessarily HP, I've done this on a PD170 loaded under 1.0) simply burying one toggle as deep as you can will induce line twists. If you fly in deep brakes just above the stall speed and then release one toggle completely you should get yourself in a right twisted up mess altogether !!
The more responsive the canopy and the heavier the pilot (and therefore, harder to get them turning to follow the canopy around) the easier this is to do.
Don't try any of this unless you've very high up (and preferably close to your next re-pack!)

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but people don't land over there for fear of being shot by Miss Billie or GPT



I can picture Chuckie telling this urban legend around the campfire, flashlight under his chin, scaring all the other monkeys! :P

As for me, I N-E-V-E-R land by Miss Billie and GPT's house! :)

[SP bows to the dragon]
Arrive Safely

John

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Pretty dang broad question. I had a crossfire 119 collapse on me at a wing loading of 1.6. I have only vague memories of what happened. I ended up with 21 seperate fractures throughout my person and was damn lucky to live. There have been problems with this canopy throughout its checkered past starting most notably with a skydiver that was killed at the ranch during an accuracy competition. The conditions that seem to be the same are turbulance and little or no radicle pilot input. Mine was a straight in landing, hand up, the whole right side folded and I went in like a really low hook turn.
Previosely (been in the sport since 92) I have only seen something like this happen once: it was a really blustery day and a guy came in on a lightly loaded huge 9 cell. The canopy started to collapse at about 75 feet, then 7 of the nine cellls reinflated and he landed hard but without injury. The cells that closed were then end cells on both sides.
Hope that helps.

Drew the healing
Drewfus McDoofus

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