Positive recovery arc vs. negative recovery arc

[grega 0]

I think i know what the differences are, but not to make a fool out of myself i won't say anything.

So what's a positive recovery arc and what's a negative recovery arc?

Some say that they need to pull a little toggles (or rear risers) to get their canopy out of the dive. Does that mean that they don't have a recovery arc but "recovery line " instead

"George just lucky i guess!"

[Spizzzarko 0]

I think when you are describing a positive recovery arc you are meaning a short recovery arc, and a negtive being a long arc. A short recovery arc is when your canopy has a tendency to pull out of a dive with little or no input and relatively little altitude loss. A long recovery arc is when the canopy doesnt really pull out of the dive or when it loses a lot of altitude in the dive. I hope this helps you out some.

[Canuck 0]

My sentiments exactly! Some arcs are shorter, some longer, but every canopy will eventually recover from the dive and return to its original flight path. I really dislike the usage of "positive" and "negative" - I think its very misleading and often nothing more than an excuse for people to dig out of their turns. "Oh I wasn't digging, my canopy has a negative recovery arc so I have to give it some toggles/risers to get it out of the turn."

Canuck

[jerry81 10]

Actually, me and Grega had a discussion some time ago on this and the conclusion reached was that canopies with a positive recovery arc will plane out or go into shallower glide by themselves after diving, while 'negative' recovery arc means that a canopy will simply go back into full flight some time after you let go of the front risers.

As for longer and shorter recovery arc- I was under the impression that a positive recovery arc invariably means it's shorter as well, but Grega says his Comp. Cobalt dives more and has a longer arc, but eventually starts planing out by itself.

So does that mean that recovery arcs can be either long or short and either positive or 'negative' (or neutral, for want of a better word), making for a total of four combinations, or are there less?

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[grega 0]

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but Grega says his Comp. Cobalt dives more and has a longer arc, but eventually starts planing out by itself.

I said it dives longer than atair impulse. and i still stand by that. but IMO it dives leeeeesss than velocitiy or similar.

And assuming that we were right about "positive and negative",i think the longer the recovery arc is the more negative it gets. and the shorter the recovery arc is the more positive it is.
Because it is somewhat logical.

Why is a recovery arc short? because the wing/canopy above our head is fairly "slow" and it slows down quite fast, you swing further forward and increase aoa (angle of attack) and the canopy starts flaring by itself, more or less. - Positive recovery arc

Why is a recovery arc long? the canopy is faster and it doesn't slow down so fast, so you don't swing so much forward. The aoa doesn't increase more than that at normal flight, so it doesn't start flaring. -Negative recovery arc


Swoop masters and canopy designers, please correct me if i'm wrong. it's just the thought that entered my mind couple of minutes ago

"George just lucky i guess!"

[PhreeZone 15]

Recovery arc is based on more then just airspeed.

Trim angle, placement locations of the line attachment points, cascade location, line length, airfoil chosen, nose design, and even weight shift in the harness all play a factor in the recovery arc. Look at the length of a Velocities lines and compare that to a Stiletto. The Stiletto is shorter and that results in a shorter arc, more responcivness and other factors.

Its is a difficult thing to design a canopy with all the factors playing into it, but a minor change like the H-Mod will alter the rest of the canopy too.

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And tomorrow is a mystery

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[grega 0]

I agree, but doesn't longer recovery arc mean more airspeed in a dive?
I mean if you turn a canopy so it's paralell to the horizon and then let go of both front risers, won't you gain more airspeed with a canopy that has longer recovery arc?

"George just lucky i guess!"

[prost 0]

This is a term that has been debated a lot. Part of the confusion comes from the name "negative recovery arc" that implies that it somehow will keep diving after a turn. Part of the problem comes from the characteristics being explained poorly and some of the problem comes from just plain bad info. Let's examine the way the term has been used. Most people say that the current crossbraced canopies and high performance non-crossed braced canopies have a negative recovery arc. The canopy that comes to mind that is not said to have a negative recovery arc is the Stiletto. What is different about the way a Stiletto reovers from a dive than the way an FX recovers from a dive? First off the Stiletto has a shorter recovery arc. If that were the only difference then there would be no reason for the term 'negative recovery arc". We could all just say short recovery arc. I think everyone that is fairly well educated in canopy control will agree that all canopies will eventually return to their normal flight attitude after a turn of any kind if no more control input is given. If you turn with a FX it will dive and then slowly lesson the angle of dive untill it reaches its normal glide rate. A Stiletto however will recover slightly differently. After a turn the canopy will decrease the angle of dive and will actually move to a shallower descent rate than normal and eventually settle back to its normal descent rate. This is why it is possible to do a front riser approach on a Stiletto and then plane out without touching any controls. A canopies wing loading will also effect this characteristic. I think the name "negative recovery arc" comes from the fact that other canopies have a "positive recovery arc". A more descriptive term for a canopy that recovers like an FX would be a "neutral recovery arc" but that just doesn't have much of a ring to it.

[AndyMan 7]

Thanks. This is the first explanation of "negative recovery arc" I've ever seen that actually makes sense.

_Am

__

You put the fun in "funnel" - craichead.

[PhreeZone 15]

Read the Big Air Sportz manual. Its a really great resource that explains this and shows with drawings the difference.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[Spizzzarko 0]

Let's get away for this use of the words "Positive, negative, and neutral" when it comes to rocovery arc. Look at it... We are talking about the distance that it takes for a canopy to return to the state of controlled flight, meaning how the canopy flies with no controll input, or full flight if you will. Distance is usually measured in increments being longer or shorter, and I'm not really sure what the hell you guys mean buy a "neutral" recovery arc. It sounds like a bad medical term, "My dog came down with the "Neutral recovery arc" and I had to put it to sleep."

Let's face the facts...
1. No two canopy's have the exact same recovery arc. Some are going to be longer, and some are going to be shorter.
2. Very few canopy's of the same make and model are set up exactly the same. Look at brake settings, line wear,ect., ect., ect... Some recovery arcs are going to be longer, some are going to be shorter.
3. Recovery arc is going to be dependant on many different factors. Namely, brake settings. If your brake lines are short then you are telling your canopy to creep out of the dive you have put it into because your lines are creating a controll input in the tail of the canopy. I cant tell you how many people I see flying around with their canopy's set up improperly due to short brake settings, twisted brake lines, and even line shrinkage.

[prost 0]

There is a diffence in that some canopies will briefly go to a flatter than normal glide after recovering from a turn.

[Spizzzarko 0]

I believe that comes from the canopy being set up improperly. If you canopy is "climbing" after you give it a controll input, then you have a serious line trim problem... Canopy's are meant to dive, If you made a canopy that climbed, you would successfully be one of the few people in this sport to actually make lots of money. Than we could phase out the airplanes. That would be good, because we wouldn't really have to deal with the FAA that much.

[AggieDave 6]

I disagree.

Every stiletto I've ever jumped (and myold Heatwave) would climb, begin to stall, then dive again after a front riser maneuver. Well, let me quantify that. Not every front riser maneuver, just one that would build more speed then the canopy could fly with. One of the strangest sensations I've had was a stiletto that I actually felt slow down about 2/3s of the way through a fairly agressive 270. It wasn't trying to recover yet, it just reach a point it couldn't go any faster and began to slow down.

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

[jerry81 10]

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I believe that comes from the canopy being set up improperly. If you canopy is "climbing" after you give it a controll input, then you have a serious line trim problem...

Did I misunderstand or are you saying that no canopy will, after control input (front riser turn), return to a glide flatter than its full-flight mode, if only for a short period of time, unless something is wrong with it?

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[Spizzzarko 0]

If you told this to PD they would tell you to send it in for line replacement. Let's get back on track with the original intent of the thread. Yes, stilletto's and heat waves have a notoriously shorter recovery arc than some of the canopy's that are popular today. Also with the stilletto, with a properly timed turn, it will plane out on it's own. That's how some people are getting the monster swoops out of these canopy's. Face it, a stilletto is about 11 years old, and back then many people where doing the toggle whips to final. Now it's more common for people to use front risers for landings. Look at the number of people posting in this forum with 50 jumps talking about fron riser use!!! 5 or 6 years ago, people with that low jump numbers using front's would probably be banned from a DZ, but that's another story. Now the canopy's on the market have a tendancy to dive quite a bit more, because the manufacturers are realizing that's what people want.

As far as your stilletto or heatwave (I have owned both) is concerned, I strongly believe the phenomenon that you are talking about is caused from your brake lines being to short, or your outside lines being shrunk from your slider. But should the canopy climb up or slow dramaticly down? Hell's no... That's a major defect in the canopy if you ask me. I think some people really don't realize is how IMPORTANT line trim becomes when you are wanting to wring tho most performance out of your canopy, and some people are making decisions about a canopy because of the poor performance of out of trim canopy's.

[AggieDave 6]

Well, the stiletto I was borrowing had a almost new lineset and I had let the brakes out to what I like, which gives no deflection to the tail during FR manuevers.

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

[Spizzzarko 0]

OK Stilletto swoop. You do you turn too high, the front riser pressure builds up and the canopy planes out on you (the shorter recovery arc thing). Your in full flight (toggles all the way up giving no input), but the canopy is still not losing altitude, but it is slowing down. The canopy slows to the point where it's airspeed can no longer create the required amount of lift to suspend our fat asses(mine being fatter than others). Now the canopy is starting to lose altitude and regain some of the speed it lost from it planning out (assuming you are not giving any controll input). This may feel like it's almost stalling, but trust me... It's nowhere near the stall point. It think this is what your describing, and it's maddening when your learning to swoop on these canopy's. As far as the canopy gaining altitude when this happens, that would be caused from improper brake settings or a canopy that's out of trim. I have seen people jumping the old "ragged" out stilletto's, and they do a low toggle turn and it dives a little and then with relativly no input it kind of pops up and then just sinks to a tip toe landing. They definatly needed new lines. I hope this clears up what I'm trying to get accross. Oh, BTW your friend Aaron, the Academy Cadet, is a very talented canopy pilot. He and I where doing some swoops on Saturday.

[prost 0]

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Let's get back on track with the original intent of the thread

Isn't the name of this thread "Positive recovery arc vs. negative recovery arc"

Spanking new Stilettos will do this as well as older ones and so will lightly loaded crossfires and I expect other "high performance elipticals" will do this at very light loadings. It used to be a big thing to plain out without using any inputs after a front riser approach. I even remember an article showing a member of the Golden Knights just after plain out and the article points out that he is not using any brakes (rear risers were not common then).

[prost 0]

No i have not seen one get close to the stall point or gain altitude. That is not my point. Only that it will briefly fly at a glide angle that is less steep than normal before returning to the normal glide angle. I have seen this extreme enough that a canopy will briefly maintain its altitude.

[Spizzzarko 0]

Looks like we are talking about the same thing then.
I love it when we see eye to eye.

[BrianSGermain 1]

Uh, let me chime in here for a sec...

There are plenty of wings that can and do achieve level flight following accelerated flight modes.

The issue is lift in proportion to suspended load.

Light wing loading, for example, will cause most canopies to fly with zero descent rate following a high speed approach; even when they are perfectly in trim. You are correct that short brake lines will significantly shorten the recovery arc. This is not, however the heart of the issue. It is the cause in this instance, but not the "root cause".

Lift is what we are talking about here folks.
It is a powerful force.


The parachute's lift has the ability to change the flight path. That is the center of the recovery arc phenomenon. If the airfoil is tall, the trim flat, or the wing loading low, the recovery arc will be such that the wing will be altered in it's flight path solely due to the lift.

When paragliding, I find that I climb following each turn, regardless of whether or not I am in the "lift band" or a "thermal". This is the extreme case, but it is exemplary. Many lightly loaded canopies, or those designed deliberately or inadvertently to have a "strong" recovery arc have the ability to go all the way to level flight, or even climb in some cases.

So, how about "strong" vs. "weak" recovery arc?

I doubt the mega-swoopers will like the idea of anything that they own being "weak" but the term is very descriptive.

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[grega 0]

So is it right to say:

-The longer the recovery arc is, more "negative" or "weak" it will be

-The shorter the recovery arc is, more "positive" or "strong" it will be.


Leave all the technical stuff like wing loading, design of a canopy, trim,... I know it all contributes to the recovery arc and how strong or weak it is. But let's say you are watching from 100m away, are those sentences above correct?

"George just lucky i guess!"

[BrianSGermain 1]

You've got it!

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[Bosveld 0]

I stand to be corrected, but

I am trying to learn this swoop thing, and learn it correctly. I have spoken to all the master swoopers I have ever seen and their response was all the same. Canopies that recover quicker means lower turns, which means less margin for error.

When your canopy recovers quickly it means almost going back to the committing toggle turn low to the ground that we used to see a lot. Your angle in the corner is smaller, so when you want to start doing low turns or swoops it means more danger.

If you have a long recovering canopy, it means higher turns and if you do these correctly it means by the time you get to the ground your canopy will be very close to recovery but with just as much speed. If you did this too low you will have more time to give input earlier than with committing quiker recovering canopies.

This is the reason people started using front rizers in the first place and moved away from toggles. Safer, longer swoops!

Whatever the mind can conceive and believe, will be true!