canopy types and suitable wingloadings

[metalslug 36]

It wouldn't surprise me if this has been discussed somewhere before.. but a search of the posts came up empty.
So, my question is....

I notice on all the canopy manufacturers' websites that their recommended wingloading charts for fully ellipticals only consider the advanced and expert jumper.. with wingloadings recommended at around 1.4 or higher.
By contrast, the square canopies are more suited for the student or novice at much lower loadings, as low as 0.6 in some cases.
Yes, I have stated the obvious, but I'm going somewhere with this..

Now, I'm fine with this, and certainly intend to respect these guidlines.. but I am a little curious as to exactly why.. and "What if...".
I'd like to know what the flight characteristics of both types of canopies would be like if these wingloadings were swopped in an experiment.

Meaning:

(1)How would a square canopy behave when loaded above 1.4 ?
Could a canopy god fly it with the same margin of safety as an elliptical at the same loading?
How would it behave ? Would it sink like an anvil ..or even collapse ?

(2)How would a fully elliptical canopy behave at low wingloadings, (lower than 1.0) Would it not be able to hold its shape ? ..spin up much more easily and/or be especialy vunerable to gusts and cross-winds ? Would it have a total lack of forward speed and therefore virtualy no flare power on landing ?
..or would it simply fly like a 'twitchy' square ?
Has anyone experienced or witnessed the flight profile of a fully-elliptical loaded below 1.0 ?

If it is believed that no members here have been insane enough to attempt either.. then I'd also welcome speculation from anyone who is confident of their knowledge in this area.

[AggieDave 6]

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Has anyone experienced or witnessed the flight profile of a fully-elliptical loaded below 1.0 ?

I've flown the Sigma 370 tandem main doing a solo before (you have to for your TM rating). Its basically the same airfoil as a Vengence, just with out airlocks. I was loading it somewhere around 0.8:1. It flew fine, sluggish, but fine. No problem with inflation or anything.

The only problem is that since being a tandem canopy, it is a totally different animal, so that doesn't exactly scale properly for your question.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[livendive 8]

I've made plenty of jumps on a Triathlon loaded at a little over 1.8:1. It flew fine, if a little quicker than the average Tri. I've done CRW with a Lightning loaded a hair over 1.7 and it too flew fine. I've also made and watched solo jumps on Icarus tandem canopies at less than 0.7:1, and they are much easier to fly than their (larger) square counterparts. Nothing on any of these jumps suggested that the shape of the wing compromised safety at those loadings.

Blues,
Dave

"I AM A PROFESSIONAL EXTREME ATHLETE!"
(drink Mountain Dew)

[Ron 10]

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(1)How would a square canopy behave when loaded above 1.4 ?
Could a canopy god fly it with the same margin of safety as an elliptical at the same loading?
How would it behave ? Would it sink like an anvil ..or even collapse ?

A square would fly fine at a higher wingload. It would not be anymore dangerous to fly a Sabre at 1.8 than a Stiletto.

But most people who have the experience to fly at these wingloads find that the elliptical performs better over all Wingloads, so they jump an elliptical.

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(2)How would a fully elliptical canopy behave at low wingloadings, (lower than 1.0) Would it not be able to
hold its shape ? ..spin up much more easily and/or be especialy vunerable to gusts and cross-winds ? Would
it have a total lack of forward speed and therefore virtualy no flare power on landing ?
..or would it simply fly like a 'twitchy' square ?
Has anyone experienced or witnessed the flight profile of a fully-elliptical loaded below 1.0 ?

An elliptical at a low wingload is not less safe than at a high wingload....In fact a higher wingload is worse for tine twists.

Any canopy at a light wingload will have the same type of problems...

Planform Elliptical vs. Square is about performance at any wingload....Wingload effects both types about the same (with the exception of line twist on a highly load elliptical).

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If it is believed that no members here have been insane enough to attempt either.

Its not about insane...Most that can fly a high wingload just want to fly elliptical. And most that should be jumping a low wingload should not be on an elliptical either.

Ron

"No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334

[freakydiver 0]

My Sabre at 1.5 flys pretty similarly to a Stilletto 135 I fly at a DZ 4000 feet lower in alti. Not as quick in the turns, not as much overall lift, but I can really carve it in and feel perfectly safe under it.

-- (N.DG) "If all else fails – at least try and look under control." --

[rigging65 0]

Remember that being elliptical or square really has more to do with rate of turn, or what we commonly think of as the basic level of performance for a canopy. That isn't to say that rate of turn is the only factor is defining performance, but it's a major one...especially for younger folks in the sport.

With that said, most canopies will perform well within a very large range of wingloadings. The optimum wingloading (where you can expect to get the best characteristics out of the canopy) is most often higher for ellipticals than for squares, but that doesn't mean you can't fly squares loaded heavy...or fly ellipticals at light loadings.

You run into problems at the very heavy and very light ends of wingloading, regardless of canopy type, but in the middle is generally fine. You might not get everything out of the canopy that it has to offer, but it'll fly and fly safe (usually)...

"...and once you had tasted flight, you will walk the earth with your eyes turned skyward.
For there you have been, and there you long to return..."

[flyhi 24]

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I've flown the Sigma 370 tandem main doing a solo... I was loading it somewhere around 0.8:1.

Does that mean you are about 295 out the door? What do smaller TM's say about their experience. I bet there are some loading it at .5:1 or so.

Shit happens. And it usually happens because of physics.

[andy2 0]

I loaded my student canopy at ~.6:1. It was mighty sluggish, penetration sucked, but the canopy itself never showed any signs of collapsing, etc like the original post was inquiring about. It was great to learn landing on where I hardly even needed to flare to get a standup landing
I was in for a surprise when I jumped on a 1:1 WL!

---------------------------------------------
let my inspiration flow,
in token rhyme suggesting rhythm...

[AggieDave 6]

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Does that mean you are about 295 out the door?

Close, the tandem rig weighs about 50lbs. That and I am by no means a "small guy".

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[dragon2 2]

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I loaded my student canopy at ~.6:1. It was mighty sluggish, penetration sucked, but the canopy itself never showed any signs of collapsing, etc like the original post was inquiring about. It was great to learn landing on where I hardly even needed to flare to get a standup landing
I was in for a surprise when I jumped on a 1:1 WL!

Precisely my story!!


I 'load' a Manta at 0.55:1. I did one no-flare landing once: I had this routine for the first couple jumps: it's flare time so WAIT WAIT FLARE!! Only after 3 jumps I got it so it went like this: it's flare time so WAI- BAM! ankles-knees-teeth (I was still hanging in an X). Oooff, but no harm done.

Jumped a Manta again for my 300th, best SL exit I ever did, but I could NOT keep up (or rather, down) with the 2 other students (guys but not very heavy at all)... Tried fronts but the nose went all mushy... So I ended up hanging around a LONG time...

On landing I thought, how come I couldn't land this before??!! It's sooooo easy (except I needed to keep a way way bigger tab on the wind).

ciel bleu,
Saskia

[kansasskydiver 0]

I fly my Sabre 170 at 1.5:1 i have to keep in mind that A line stalls could happen in higher winds and hard toggle turns, but I haven't had a problem loading the ol Sabre.

<--- See look, pink dolphins DO exist!

[DrewEckhardt 0]

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A square would fly fine at a higher wingload. It would not be anymore dangerous to fly a Sabre at 1.8 than a Stiletto.

Provided that you cut away before landing and don't have a marginal spot.

Every canopy has a wing loading beyond which increases start to degrade the performance - the glide gets steeper, swoops shorter, and there's little lift left when you use it for something other than flaring after plane-out (this could lead to an injury). There are also wing loadings beyond which you will find the stall speed unacceptably high if you can't reduce it by partially unloading the canopy, especially with a slight tail wind on a hot summer day (this could lead to an injury if you opt not to slide in on your ass).

At elevation (4500-6000 feet MSL), I'll jump air locked and cross-braced canopies at 1.9 pounds/square foot but won't load a square beyond 1.5. Even at that point, larger squares or more efficient planforms are better (more enjoyable and safer) options. With a 200 pound exit weight, Monarch and Sabre 135s (1.48 lbs/foot) seem to stall with more speed than Stiletto 120s (1.67) and Samurai 105s (1.90). Their poor response to toggle input at that loading make it more difficult to be leveled out at ground level for a gradual weight transfer and slower stall, and there's little lift left if you use some to go arround an obstacle.

Having shrunk my belly+exit weight by 25 pounds and played with the canopies in question at different wing loadings, I suspect that up here squares seem to perform optimally at 1.3-1.4 pounds/square foot, Stiletto class canopies 1.6-1.7, and air-locked chutes more than 1.7 and less than 1.9 (ordered mine after my belly shrunk, and haven't played with lead yet). Down at sea level a size smaller would definitely be nice with the Sabre+Stiletto (don't know about the Samurai yet).

Those numbers aren't too out of line with the maximum loadings from PD (1.5 for the Sabre, 1.7 for the Stiletto, 1.8 for the Vengance) and Big Air (1.8 on the Samurai).

[Ron 10]

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Provided that you cut away before landing and don't have a marginal spot.

I have loaded a square at 1.8....It was fine.

Now I am in FL, and not at a high elevation.

But it can and has been done quite safely.

You bring up good points about density altitude...But it effects ALL canopies.

Yes a Xbraced, or airlocked would be BETTER at a hugh wingload...But his question was square vs elliptical.

Since both are non goodie canopies thay would both be about the same level af saftey at the same wingloads.

"No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334