Forums: Skydiving: Safety and Training:
Why a minimum wing loading requirement?

 


fibonacci  (D 30208)

Apr 11, 2011, 1:52 PM
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Why a minimum wing loading requirement? Can't Post

I have jumped a 139 sq ft Crossfire 2 a few times and loved it. I am getting ready to order one, but my wing loading for a 139 is about 1.37. Icarus recommends a minimum wing loading of 1.4. Is there a safety issue if I want to load it at 1.37? Thanks!


phoenixlpr  (D 3049)

Apr 11, 2011, 2:19 PM
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Re: [fibonacci] Why a minimum wing loading requirement? [In reply to] Can't Post

In reply to:
I have jumped a 139 sq ft Crossfire 2 a few times and loved it. I am getting ready to order one, but my wing loading for a 139 is about 1.37. Icarus recommends a minimum wing loading of 1.4. Is there a safety issue if I want to load it at 1.37? Thanks!

What kind of wing are you flying?
A RAM-Air canopy?
Your canopy is flying as long its pressurized.
An airfoil is designed with a minimum airspeed in mind.
If you go below that your canopy might not open properly or might not be stable in turbulence.

Under loading a semi-closed nose elliptical canopy might not be a good idea.


JohnRich  (D License)

Apr 11, 2011, 2:48 PM
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Re: [fibonacci] Why a minimum wing loading requirement? [In reply to] Can't Post

Wear 5 lbs. of extra weight, and then you're good to go.


Rugby82  (D 705310)

Apr 11, 2011, 11:54 PM
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Re: [fibonacci] Why a minimum wing loading requirement? [In reply to] Can't Post

1.37 should be OK.

The problem with Crossfires is that they can collapse in turbulence if you load it way too low (< 1.2). If you're that close to the minimum recommended wingload it should be fine.


floormonkey  (D License)

Apr 12, 2011, 7:32 AM
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Re: [Rugby82] Why a minimum wing loading requirement? [In reply to] Can't Post

Can you show me where the manufacturer says this? Or can you show documented instances of this?


fibonacci  (D 30208)

Apr 12, 2011, 11:12 AM
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Re: [floormonkey] Why a minimum wing loading requirement? [In reply to] Can't Post

In reply to post: "Can you show me where the manufacturer says this? Or can you show documented instances of this?"
-----------------------------------------------------------------------

The wing loading recommendation is on the following Icarus web page:
http://www.icaruscanopies.aero/crossfire-2


Scrumpot  (D License)

Apr 12, 2011, 12:11 PM
Post #7 of 23 (1608 views)
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Re: [fibonacci] Why a minimum wing loading requirement? [In reply to] Can't Post

In reply to:
In reply to post: "Can you show me where the manufacturer says this? Or can you show documented instances of this?"

I don't see anywhere it says that this canopy is prone to collapsing in turbulence, if "underloaded"! Mad - That is what your poster, to whom you are replying is asking about, and "challenging" his addressee to quantify.

So many people just plain "parrot" on here, something they've (or think they have) heard, and espouse it as if fact. I think that is (was) the point herein, trying to be made. FWIW.


(This post was edited by Scrumpot on Apr 12, 2011, 12:12 PM)


dragon2  (D 101989)

Apr 12, 2011, 12:36 PM
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Re: [fibonacci] Why a minimum wing loading requirement? [In reply to] Can't Post

I had more trouble with the occasional weird opening (inflation issues) when I underloaded my vengeance at 1.15-ish. Solution: gained a good amount of weight Pirate and now fly it at 1.4
Canopy opens a lot better now Angelic


phoenixlpr  (D 3049)

Apr 12, 2011, 1:19 PM
Post #9 of 23 (1558 views)
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Re: [Scrumpot] Why a minimum wing loading requirement? [In reply to] Can't Post

In reply to:
I don't see anywhere it says that this canopy is prone to collapsing in turbulence, if "underloaded"! Mad - That is what your poster, to whom you are replying is asking about, and "challenging" his addressee to quantify.
It was a light women, low WL, hot summer turbulent day and a Katana - restricted nose canopy. Her canopy collapsed <40m.

I've seen X-rays. Do they look convincing? She got a several corrective surgery, more than a year recovery and left the sport.


riggerpaul  (D 28098)

Apr 12, 2011, 5:23 PM
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Re: [floormonkey] Why a minimum wing loading requirement? [In reply to] Can't Post

In reply to:
Can you show me where the manufacturer says this? Or can you show documented instances of this?

As others have said, the manufacturer does not say that the canopy will collapse if loaded below their recommended wing loading.

But, really, does the manufacturer tell you not to toggle whip it into line twists? They do not.

Does that mean that you can toggle whip the thing and expect that nothing bad will happen? It does not.

I think it unlikely that the manufacturer is going to actually say it will collapse. It just isn't something any canopy manufacturer would like to say about his product.

Still, the manufacturer recommends a wing loading of at least 1.4 lbs/sq ft.

There is probably a reason.

Someone else posted his recollection of a Katana that was lightly loaded and collapsed in turbulence. Does that cover it? Or does it have to be a Crossfire2 to count?

Canopies use their airspeed to power the canopy pressurization.

Holding the size of a canopy constant, wing loading is directly related to the speed at which the canopy will fly.

More weight equals more speed. Less weight equals less speed.

Too little weight equals too little speed.

What do YOU think will happen to a canopy that is not flying fast enough?

Eventually it will stall. And with a stall comes the possibility of collapse.

And, of course, since turbulence means that the relative wind can shear - coming from different directions in rapid succession, flying too slowly in turbulence will risk a stall when you would least like it to occur.

Else why would the manufacturer recommend a wing loading minimum in the first place?


Scrumpot  (D License)

Apr 12, 2011, 7:17 PM
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Re: [phoenixlpr] Why a minimum wing loading requirement? [In reply to] Can't Post

The "reputation" of Crossfire's in particular, being prone in any way to collapse, comes from IIRC - an actual incident where a woman participating in a swoop competition, experienced radical collapse from tree-rotors right at gate-entry and went in. There was also a certain serial-# run that was re-called from (or for) line-trim settings concerns. This also begat a whole further debate with/on them, on the merits of assuring adequate loading of them too.

Not too long thereafter, Icarus released the XF-2, and "all hailed" it as "curing" all the above concerns. Most of this is anecdotal however, and my earlier post was more really, intended to point out that the wingloading range reccomendation chart is NOT what the poster was looking for.

The OP already had that, and he was looking for more of the "reasonings" behind what he heard.

Hopefully, my post here now, more adequately provides that. Although RiggerPaul is correct as well, that you probably no matter how hard you look - will not find the MFR anywhere actually stating to you, to load it at least at "X", lest it collapse.

One poster calling on another to provide your written proof, or "cite your documented references", and me then further chiming in upon that - calling on folks to simply not just "parrot" merely RUMOR or something they have (or think they have) heard "somewhere", should not be taken as my position or support that it is OKAY to under-load a clearly designed to be a "HIGH-PERF" canopy, so as to make it more docile, and that then makes it okay.

That would be a mistake.

FFI: see another thread already discussing this along similar lines, that can be found: HERE


floormonkey  (D License)

Apr 12, 2011, 8:06 PM
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Re: [riggerpaul] Why a minimum wing loading requirement? [In reply to] Can't Post

Oh, I'm more than aware of all these things. I'm also aware of what people "say the manufacturer says."

When I read the cf2 page, I see a manf who says "We recommend wing loadings from 1.4 psf to 2.1 psf."

I do not see a manufacturer who says "this canopy is to be jumped at no lower than a 1.4 wingloading."

These are 2 very different statements that mean very different things.

I often see/hear people say things and do not understand what they have heard/read.

As far as the Katana incident, does it not seem turbulence and a poor choice (jumping on a turbulent day while on a lightly wingloaded canopy) was a greater factor than wl? see PD's statement on minimum wingloading/wingloading in general: http://performancedesigns.com/..._Interpretations.pdf And as far as restricted nose goes, I believe both my VX and Velocity perform better in turbulence than a conventional nose canopy, though that is solely personal belief and I've never looked for research to confirm it.

And yes, I was looking for information specifically about a manufacturer recommendation or incident relating to a CF2, since that is what the OP is referring to. The recall was a line trim issue. http://www.nzaerosports.com/...ion/service-bulletin

Personally, I don't understand why someone would post in a forum where anyone can answer when they could easily email attila@nzaerosports.com, support@daedaluscanopies.com, support.chicago@icaruscanopies.aero, sales.usa@icaruscanopies.aero, icarusorders.eu@icaruscanopies.aero, or call (815) 434-6098 and have the manufacturer give them an answer that has plenty of validity behind it.

And while this manufacturer doesn't tell you you can toggle whip it into line twists (though others do), that is taught in AFF. I'll assume that someone with 800 jumps (the OP) probably knows that.


(This post was edited by floormonkey on Apr 12, 2011, 8:27 PM)


floormonkey  (D License)

Apr 12, 2011, 8:46 PM
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Re: [fibonacci] Why a minimum wing loading requirement? [In reply to] Can't Post

The other concern, however, is your reserve. It is generally recommended have a similarly sized main and reserve. Under your (what I assume is a) PDR176, you are at just over 20% difference in size. The actual important stat is the difference in the top of the leading edges, but just know you're getting close to those puppies not being comfortably compatable.

http://www.pia.com/piapubs/tb/TB-261.pdf


(This post was edited by floormonkey on Apr 12, 2011, 8:50 PM)


DocPop  (C License)

Apr 12, 2011, 9:11 PM
Post #14 of 23 (1451 views)
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Re: [floormonkey] Why a minimum wing loading requirement? [In reply to] Can't Post

In reply to:
It is generally recommended have a similarly sized main and reserve.

IMO this is not what is generally recommended these days. Most of the recommendations I have heard have been along the lines of "use the biggest reserve you can" in case of having to land one while unconscious or incapacitated.

I personally think these risks are greater than that of having an unstable two-out situation.


floormonkey  (D License)

Apr 13, 2011, 8:00 AM
Post #15 of 23 (1387 views)
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Re: [DocPop] Why a minimum wing loading requirement? [In reply to] Can't Post

USPA recommends it, PIA recommends it, and most riggers (real riggers, not just fluff n stuffers) that I have met recommend it. I teach it in AFF.

Please read the linked document for the reasons why.

Some people may say "use the biggest reserve you can", however, they should be saying "use the biggest reserve that's compatible".

Just because some people say to do it, doesn't mean they are right. The "experts" (read: the ones who have done the research) are the ones I prefer to follow.

With that said, I jump a VE90 with an OP143 reserve. The A-lines have a 2 inch difference, and inflated, there will be about a 6 in difference between my top leading edges. I decided the risk was worth it as I didn't feel the 126 was comfortably survivable for me.

I didn't say he shouldn't, I just want to make sure he's educated on the risks and can make that choice as an educated jumper, not as one who just does what he hears is safe around the bonfire.

How about the risk of landing a two-out in an unstable configuration while incapacitated?

Which happens more often, unconscious or two-out?

Which is more likely for this jumper? (does he like to pull low or do zoo dives, or does he pull high and always do solos?)

These are questions the OP should ask him/herself and evaluate.

If we educate our jumpers using facts instead of rattling off opinions, perhaps our jumpers will stop killing themselves.


dragon2  (D 101989)

Apr 13, 2011, 9:11 AM
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Re: [floormonkey] Why a minimum wing loading requirement? [In reply to] Can't Post

Meh, I've had a 2out with 2 very compatible canopies (student main and student reserve) and they still downplaned.

I also had a good number of reserve rides, both as real reserves and as mains.

I agree with "get the biggest reserve you can" because the chances of you flying just your reserve are way way higher than a 2out and even if you have a 2 out, no guarantees the 2 canopies will play nice together. F.i. I very very much doubt my vengeance will play nice with any size reserve.


mchamp  (D 32129)

Apr 13, 2011, 9:30 AM
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Re: [floormonkey] Why a minimum wing loading requirement? [In reply to] Can't Post

This was pretty much exactly what I was getting at in my recent post....guess I didn't quite word it properly lol


http://www.dropzone.com/...6;page=unread#unread


Premier billvon  (D 16479)
Moderator
Apr 13, 2011, 5:28 PM
Post #18 of 23 (1290 views)
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Re: [floormonkey] Why a minimum wing loading requirement? [In reply to] Can't Post

>It is generally recommended have a similarly sized main and reserve.

A very poor recommendation for someone who is jumping small mains.

>they should be saying "use the biggest reserve that's compatible".

This I agree with. Fortunately, manufacturers are starting to make large reserve/small main combinations for people jumping heavily loaded mains.


chuckakers  (D 10855)

Apr 13, 2011, 6:13 PM
Post #19 of 23 (1283 views)
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Re: [fibonacci] Why a minimum wing loading requirement? [In reply to] Can't Post

In reply to:
I have jumped a 139 sq ft Crossfire 2 a few times and loved it. I am getting ready to order one, but my wing loading for a 139 is about 1.37. Icarus recommends a minimum wing loading of 1.4. Is there a safety issue if I want to load it at 1.37? Thanks!

One word. "Nova".

I have over 1,000 jumps on one loaded the way it was designed to be loaded, many that were made after it was grounded because they were collapsing. I'm still alive.

Wing loading is relevant in stability. Some designs require more than others.


floormonkey  (D License)

Apr 13, 2011, 8:35 PM
Post #20 of 23 (1251 views)
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Re: [billvon] Why a minimum wing loading requirement? [In reply to] Can't Post

In reply to:
>It is generally recommended have a similarly sized main and reserve.

A very poor recommendation for someone who is jumping small mains.

>they should be saying "use the biggest reserve that's compatible".

This I agree with. Fortunately, manufacturers are starting to make large reserve/small main combinations for people jumping heavily loaded mains.

That's why I said generally. That's also why I provided a reference to the technical report that that recommendation is based on, so that the jumper could make his own decision based on facts.

This jumper (the OP the advice was meant for) is not jumping a small main.

As for myself, when the shit hits the fan, I want bigger. I've had to land my reserve in a very small, tight spot due to a bad decision, and that event made me decide to not downsize my reserve regardless of my main size.


(This post was edited by floormonkey on Apr 13, 2011, 8:52 PM)


Rugby82  (D 705310)

Apr 13, 2011, 11:39 PM
Post #21 of 23 (1230 views)
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Re: [floormonkey] Why a minimum wing loading requirement? [In reply to] Can't Post

In reply to:
In reply to:
>It is generally recommended have a similarly sized main and reserve.

A very poor recommendation for someone who is jumping small mains.

>they should be saying "use the biggest reserve that's compatible".

This I agree with. Fortunately, manufacturers are starting to make large reserve/small main combinations for people jumping heavily loaded mains.

That's why I said generally. That's also why I provided a reference to the technical report that that recommendation is based on, so that the jumper could make his own decision based on facts.

This jumper (the OP the advice was meant for) is not jumping a small main.

As for myself, when the shit hits the fan, I want bigger. I've had to land my reserve in a very small, tight spot due to a bad decision, and that event made me decide to not downsize my reserve regardless of my main size.

Now let's take my example. My exit-weight is around 250 Lbs. and I'm around 6"6'. My main canopy currently is a Crossfire2 - 139 but will eventually be around 110-120 sq. ft. X-braced because I love to swoop.

Looking at the PD-optimum chart I'll be looking at a 193 or 176 sq. ft. because of my weight. Any reserve which would be smaller will put me over the MSW. If I want to be able to land it unconscious and thus being in the intermediate-range I'll need a 235.

The point of having similar sized reserve and main canopies just doesn't work for me let alone finding a container that can fit a 235 sq. ft. reserve and a 110 sq. ft. main.


Premier billvon  (D 16479)
Moderator
Apr 14, 2011, 9:41 AM
Post #22 of 23 (1180 views)
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Re: [Rugby82] Why a minimum wing loading requirement? [In reply to] Can't Post

>My main canopy currently is a Crossfire2 - 139 but will eventually be around 110-120
>sq. ft. X-braced because I love to swoop.

>Looking at the PD-optimum chart I'll be looking at a 193 or 176 sq. ft. because of my
>weight.

Dang, that's just over the limits of the Mirage MOS (which is what I have.) That will take an Optimum 160/XF2 109. I keep hoping they offer that sort of spread in other sizes, but nothing yet.

However, it's not hard to modify a container to take a smaller main, via the use of padding. It should be something that a master rigger can do pretty easily.


floormonkey  (D License)

Apr 14, 2011, 11:08 AM
Post #23 of 23 (1153 views)
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Re: [Rugby82] Why a minimum wing loading requirement? [In reply to] Can't Post

So let's see...I said "generally".

Also, you weren't asking for advice, you were just repeating an unverified claim, which I merely asked for documentation of.

The OP, who the advice was written for, weighs 190lbs.

Also, since you are already jumping a Techno 155, you really have no dog in this fight except to prove me wrong.

You are right when you are talking about your situation.

I, however, was not talking about your situation.

Also, if you notice, I did not tell him not to do it, but just informed him of possible risks.

In conclusion, if you'd like to talk about compatible main/reserve sizes, let's start a new thread and talk about it there. The original question was talking about "why is there a minimum wingloading requirement?"



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