Collapsed Canopies

[ILikePizza 0]

As a student, I have been reading a bit in the 'Incidents' forum to see what kinds of things happen to people, and how they reacted appropriately and inappropriately. I have seen a few posts about 'collapsed canopies' or canopies that have not responded well to turbulence.

What are some normal causes of collapsed canopies?

Will this primarily happen to smaller swooping canopies?

How do you respond?

How can you avoid this?

If it helps... I am still flying a 230 7 cell (I think ), either way it's a student rig, which puts me just under a 1:1 wing load (again, I think. I'm about 225 lbs w/o gear). And I'm not jumping anything over 14mph gusts.

p.s. I will definately ask the coaches and instructors at my DZ about this, but would love to hear other input as well.

...And I'm not gonna not get Randy Jackson's autograph...
Did we just become best friends?

D.S. #1000000

[JohnnyMarko 1]

Ask your instructors about this...you will get a mixture of real advice and dickhole comments on the interwebz

[phoenixlpr 0]

You can find good and valuable articles in Safety section.

[mmacro 0]

It also has to do with DZ location. I used to jum in El Paso, TX and they got strong Dust Devils in the afternoon. They can collapse just about anything.
It also has to do with flying styles. The more aggressive you fly your canopy the more likey it is to fold.
In the end it is a factor of weather, pilot activity and parachute type/design.

[burtonjm 0]

If you're 225 w/o gear, you are at more than 1:1 on a 230. Probably closer to 1.1:1

This shit, right here, is OK

[JohnnyMarko 1]

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If you're 225 w/o gear, you are at more than 1:1 on a 230. Probably closer to 1.1:1

Which would be high for a student, no?

[Heatmiser 0]

Any canopy can collapse. Get the air flowing from trailing edge to leading edge, or across the wing, instead of from the front, and it will collapse. Simplistic explanation, and these are not the only cause. Turbulent air, (think pockets of air moving at different speeds, in different directions), dirt devils, extreme stalls. Disrupt the airflow from front to back, and you can collapse. Also removing the tension between the jumper and canopy. Stalling a canopy in deep brakes, then rapidly letting up on toggles can cause a surge forward, and a momentary slack in line tension. This causes some collapse.

What you say is reflective of your knowledge...HOW ya say it is reflective of your experience. Airtwardo

Someone's going to be spanked! Hopefully, it will be me. Skymama

[Blamey 0]

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If you're 225 w/o gear, you are at more than 1:1 on a 230. Probably closer to 1.1:1

Which would be high for a student, no?

I am a similar size and was put on a 230 Navigator for my first jump and have used mostly the same size since.

If you look at Brian Gemain's chart, although it is on the low end, it is within the recommended canopy size for a larger student jumper.

[riggerrob 558]

Little risk of collapse under popular student canopies.
I can only remember one student killed by turbulence ... and that was a dust devil in Elsinore.

The reason that pro pond swoopers are at greater risk of collapse is that they routinely fly sensitive canopies close the edges of their envelopes and leave tiny margins for error.

So if you stick with lightly-loaded canopies, fly near the middle of their envelopes and avoid jumping when there are gusts or dust devils, your risk of collapse is minimal.

[west33freefall 0]

Bigger canopies are going to be more apt to collapsing due to the lower wing loading. The less wing load the less force (or change in force) by the air is required to make it collapse, or feel the turbulence. Think of aircraft. A fighter has an extreme high wingload, most can fly through pretty strong thunderstorms and be perfectly fine. Then think of a cessna 172, Not a whole lot smaller wing surface than an F-16 but a hell of a lot lighter. You can feel updrafts, wake tubulence, temperature inversions, wind changes caused by trees, buildings etc, in a 172. Thats why more experienced jumpers don't mind flying a 1.5-2.0 loaded canopy in heavier winds. However, you still have to be very conservative in the flying. Gusts are risky for any canopy, think if your canopy flies at 20mph and you have a 10 mph headwind with 10 mph gusts that means at any given second your head wind could change from a 20 mph head wind, which will cause you to have no forward drive, to a 10mph headwind, and your canopy will have to recovery its airspeed by increasing 10 mph and how do canopies gain airspeed, they dive! So gusts are dangerous no matter what you jump. Also think of tandems, huge canopies but usually moderate wingloads of 1.2-1.5 and they are usually not that apt. to colapsing. Its more in the wing loading than in the pure size of canopy.

[jsaxton 0]

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It also has to do with flying styles. The more aggressive you fly your canopy the more likey it is to fold.
In the end it is a factor of weather, pilot activity and parachute type/design.

I'd correct you, but even though I'm an internet asshole I'm just too tired right now.

[billvon 2,396]

> A fighter has an extreme high wingload, most can fly through pretty
>strong thunderstorms and be perfectly fine.

That's because the fighter's wing is stronger, relatively speaking. All canopies have about the same strength in the downward direction (i.e. close to zero.)

>Then think of a cessna 172, Not a whole lot smaller wing surface than an
>F-16 but a hell of a lot lighter.

Yep. And if severe turbulence is encountered during cruise, it is important to _reduce_ speed to prevent structural damage. We can't control our airspeed very much, so generally the wingloading sets our approximate speed.

Downward turbulence on any canopy will collapse it no matter what the wingloading. More experienced jumpers jump smaller canopies in turbulence for the same reason they jump smaller canopies - because their experience allows them to fly the more difficult canopy, even in turbulence. If there is an unrecoverable collapse, a smaller canopy will kill you a lot faster than a large one will.

[JohnMitchell 14]

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If there is an unrecoverable collapse, a smaller canopy will kill you a lot faster than a large one will.

A very well made point, Bill. Even canopy collisions were safer on the old canopies. Those fat, stable airfoils recovered quickly from turbulence or collision induced collapse. There were no unrecoverable modes, given enough altitude. What used to be just a scare or maybe minor injuries is often now a fatality.

[erdnarob 1]

Why a parachute (ram air) collapses ? When the angle of attack comes to zero or becomes negative, because there is no lift anymore and the wing starts stalling. In other words the wing doesn't support its own weight and the payload anymore resulting in a rapid descent (case #1). It can happen also if the wing slows down too much or stops moving since it takes an airflow passing above and below the wing to generate a lift (Bernouilli's law) (case #2).

The angle of attack is the angle between the wing chord and the relative air flow.
The relative airflow is the the air flow parallel and opposite to the flight path of the wing.

Causes:

Case # 1) if a sudden downward draft of air (eg. landing down wind with respect to an obstacle) or sometimes when a gust hits the wing (parachute), the angle of attack becomes negative and a stall happens

Case # 2) If suddenly you change the path of the wing (parachute) due to toggles downward move maintained for several seconds, you slows down the canopy with respect to the air or stops its forward motion and this is what happens, a stall.

Learn from others mistakes, you will never live long enough to make them all.

[timmyfitz 0]

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Why a parachute (ram air) collapses ? When the angle of attack comes to zero or becomes negative, because there is no lift anymore and the wing starts stalling. In other words the wing doesn't support its own weight and the payload anymore resulting in a rapid descent (case #1). It can happen also if the wing slows down too much or stops moving since it takes an airflow passing above and below the wing to generate a lift (Bernouilli's law) (case #2).

They are basically the same thing. In both cases, wind speed across the wing decreases and stalls the wing. A wing can stall at any indicated airspeed as long as the critical angle of attack has been exceeded.

[billvon 2,396]

>? When the angle of attack comes to zero or becomes negative, because
> there is no lift anymore and the wing starts stalling.

That's not a stall. On an airplane, that's a wing that is doing exactly what it was designed to do. If you had to do an emergency maneuver to avoid another airplane, and you pushed the nose hard over, the wing's angle of attack would go negative and it would push you downwards. Again, that is not a stall; it's just the wing flying in a different mode.

Canopies cannot resist downwards pressure since they have no rigid structure to them. This means the canopy will deform and collapse if there is negative lift present.

> It can happen also if the wing slows down too much or stops moving
>since it takes an airflow passing above and below the wing to generate a
>lift (Bernouilli's law) (case #2).

Again, that's not necessarily a stall. If a plane is parked on the tarmac, nose into the wind, and the wind is blowing at 5mph, the wing is not stalled; it is generating (a little) lift as designed.

In the air, you need to maintain X pounds of lift to keep the airplane (or canopy) in the air. To do that at low speeds you have to increase angle of attack. In an airplane this can lead to a stall because beyond a certain angle of attack (about 14 degrees) the airflow separates from the wing; lift decreases and drag goes up dramatically. That's a stall.

It is much harder to stall canopies because they are so stable in pitch. Generally you need either a very large input of brakes or a very severe change in windspeed (i.e. a wind shear) to accomplish it.

[DocPop 1]

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It is much harder to stall canopies because they are so stable in pitch. Generally you need either a very large input of brakes or a very severe change in windspeed (i.e. a wind shear) to accomplish it.

(or rear risers)

"The ground does not care who you are. It will always be tougher than the human behind the controls."

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