Positive recovery arc vs. negative recovery arc

[Canuck 0]

No retort to the deep??

As for the other, I'm curious why you didn't quote the first part of what I said:

"I never said that canopies with short recovery arcs are safer, I said canopies with long recovery arcs are not less dangerous."

Nevertheless, lets take a shitty hypothetical situation. Person is flying a Stiletto loaded at 1.8, gets cut off, and whips a 180 at 600 feet. they get to say "oops, I turned too low." Under a Velocity at the same loading, they don't get to say anything before they hit the ground. Like I said, hypothetical situation, the point is not to discuss why they did a 180, or how much altitude you will burn at 1.8 under a Stiletto vs. a Velocity, or what kind of turn they made. The point is to highlight one situation where a fast recovering canopy can be safer than a slow recovering canopy. Can you buy that?

[mnischalke 0]

Sorry, I missed this:

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Why do you assume that it's possible to control the plane-out point only on canopies with long recovery arc?

Oh, I don't assume that at all. I do think that you have more time to control the variables under a canopy with a long recovery arc than under one with a short recovery arc.

mike

Girls only want boyfriends who have great skills--You know, like nunchuk skills, bow-hunting skills, computer-hacking skills.

[mnischalke 0]

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No retort to the deep??

sure, I never said deep, nor did I infer it.

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As for the other, I'm curious why you didn't quote the first part of what I said:

"I never said that canopies with short recovery arcs are safer, I said canopies with long recovery arcs are not less dangerous."

Because it seems you contradict that statement with the second. What exactly is your definition of tolerance?

btw, you did it again:

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The point is to highlight one situation where a fast recovering canopy can be safer than a slow recovering canopy.

To answer your question, I really don't buy it. Getting cut off and whipping a 180 from a lower altitude than what a pilot is used to is bad judgment in the first place. Continuing the turn with the same inputs when he already knows he's low is really bad judgment. Flying those controls into the ground is just stupid.

mike

Girls only want boyfriends who have great skills--You know, like nunchuk skills, bow-hunting skills, computer-hacking skills.

[Canuck 0]

You're right, you didn't say it, but unless you can deconstruct my argument, or at least pose a counter arguement better than "I didn't," then I don't think you can say that you didn't infer it. Lets leave that one alone - it's a no win situation.

I admit, there is contradiction in my statement. I (like you) see safety in the hands of the pilot, not the canopy, and thus, don't like to say that any canopy is safer than any other canopy. Pilots are safe, canopies are nylon. However, I can't think of a single situation where a slow recovering canopy would be safer than a fast recovering canopy. The opposite, however, I can, and described in my previous post. And again, you are right, it would take bad judement to whip a low 180 and hold that turn into the ground - but surely you are not going to say that skydivers don't sometimes exercise bad judgment? Almost all injuries and fatalilities are a result of it! You can buy that, can't you?

Again, no insult intended.

Canuck

[mnischalke 0]

Again, I never inferred it, nor did I mean it that way. "Deep" in the corner to me is where toggles are the only option.

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However, I can't think of a single situation where a slow recovering canopy would be safer than a fast recovering canopy.

How bout this one: 90 front riser right turn from at 300 ft. Get out of the turn too soon with no further input and the canopy planes out with no toggle or riser input and slow-speed stalls 30ft above the deck. After the stall, the canopy will surge into a dive. In the first part of the surge, your controls will be mush and will remain that way for a good portion of that dive. The flare will suck and the ground will hurt. Trust me, I know.

The cool thing about that canopy was that I had a ton of no, or little-toggle-input landings. That wouldn't be cool if I was planing out more than 6 feet off the deck.

Let's get to the root of the recovery arc debate. Wings being wings--something designed to create lift--with a common suspended weight, what is it that causes the recovery arc to be longer or shorter?

mike

Girls only want boyfriends who have great skills--You know, like nunchuk skills, bow-hunting skills, computer-hacking skills.

[relyon 0]

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Let's get to the root of the recovery arc debate. Wings being wings--something designed to create lift--with a common suspended weight, what is it that causes the recovery arc to be longer or shorter?

Brian made a few posts recently that addressed this. Here's a start.

Bob

[Canuck 0]

Fine, I'll accept that, but I would WAY rather hit the ground from 6 feet with a canopy over my head, than from 600 feet with a canopy in front of me...
Again, it comes down to which is safer, and that again, comes down to the pilot.

As per recovery arcs, as Relyon said, Brian has discussed this a few times. Line trim, line length, and airfoil design/shape all come into play.

Canuck

[marks 0]

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Again, I never inferred it, nor did I mean it that way. "Deep" in the corner to me is where toggles are the only option.

please take a canopy control course. if this is your belief then i think you will learn alot and it would be a very positive thing for you.

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How bout this one: 90 front riser right turn from at 300 ft. Get out of the turn too soon with no further input and the canopy planes out with no toggle or riser input and slow-speed stalls 30ft above the deck. After the stall, the canopy will surge into a dive. In the first part of the surge, your controls will be mush and will remain that way for a good portion of that dive. The flare will suck and the ground will hurt. Trust me, I know.

depends on the canopy. but if your canopy is doing this to that much of an extreame im willing to bet you got your brake lines a little too tight.

[mnischalke 0]

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please take a canopy control course. if this is your belief then i think you will learn alot and it would be a very positive thing for you.

So four canopy control courses wasn't enough? Damn, I better do more homework. If I have misinterpreted what I have been taught, I will surely be back to this thread with a correction.

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depends on the canopy. but if your canopy is doing this to that much of an extreame im willing to bet you got your brake lines a little too tight.

Not tight at all. There was about 4-5 inches of play to be able to use the front risers without deflecting the tail. Silhouettes at 1.1 can do that easily. Like I said, I had at least a dozen no-input landings with the toggles against the rings until I came to a stop. On another half-dozen or more, I was between a foot and eight feet off the ground when I came to a stop. And, also like I said, I had one that was about 30 feet off the ground. That was the one that really sucked.

mike

Girls only want boyfriends who have great skills--You know, like nunchuk skills, bow-hunting skills, computer-hacking skills.

[mnischalke 0]

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As per recovery arcs, as Relyon said, Brian has discussed this a few times. Line trim, line length, and airfoil design/shape all come into play.

Yep. So when you said a canopy with a shorter recovery arc is more tolerant, what exactly did you mean by that? Do you mean if you pass out in the turn? Do you mean the canopy is more responsive to corrective input?

Now, this is something I haven't talked to anybody about, but it has me thinking. From what I have learned, trim is a major player in determining a canopy's recovery arc. Is a canopy with a shorter recovery arc more susceptable to high-speed stalling with the same amount (distance pulled) of input as the canopy with the longer recovery arc? (all things being somewhat equal)

mike

Girls only want boyfriends who have great skills--You know, like nunchuk skills, bow-hunting skills, computer-hacking skills.

[mnischalke 0]

I forgot to ask something. What do you think I should I believe if I am wrong about

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"Deep" in the corner to me is where toggles are the only option.

From the Big Air Sportz Owners Manual by Brian Germain:

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If you are really low and really steep, hitting your breaks RIGHT AWAY is your only option for survival. Those who hesitate will inherit the earth.

I also found this from his manual to be interesting and quite relevant:

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Both the Samurai and Lotus are designed with a somewhat negative “Recovery Arc” when loaded at 1.3lbs/sf or higher. In other words, following a diving maneuver, the canopy will continue to loose altitude until the pilot provides some toggle depression to level out. This is a conscious design choice on our part, so that you will find it easier to hit the “surf-window”. In other words, if you are slowly descending to flare altitude with sustained airspeed, you merely have to wait for the right moment to apply the toggles in order to level off.

A wing that levels itself out after an airspeed-increasing maneuver will do so regardless of the altitude AGL. If you are at 30 feet when it chooses to level out, that’s where you stay until the airspeed runs out, and then you get an ankle-burner for a landing. Big Air Sportz canopies will afford you the opportunity to make final approach adjustments on all axes: up, down, and turns. You will learn to love this characteristic when learning how to “swoop”.

mike

Girls only want boyfriends who have great skills--You know, like nunchuk skills, bow-hunting skills, computer-hacking skills.

[AggieDave 6]

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the canopy will continue to loose altitude until the pilot provides some toggle depression to level out. This is a conscious design choice on our part, so that you will find it easier to hit the “surf-window”. In other words, if you are slowly descending to flare altitude with sustained airspeed, you merely have to wait for the right moment to apply the toggles in order to level off.

Isn't that what folks (SkymonkeyOne, Canuck, myself, etc) are saying, that Pro's don't intentially dig their canopies out, they pop for the plane out, but you were argueing against?

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

[mnischalke 0]

Wow, you got that from chuck's post?

I suggest you read his post again.

I'll save ya the clicking trouble. Canuck said:

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I tell ya what, you find one single person who competed at the Pro level in a PST sanctioned meet last year who will come on line and say that it is normal to dig out of the corner, not just "use rears to plane out" (your words), but actually "dig" (yup, your word again) and I'll stand corrected.

To which, SkymonkeyOne replied:

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Canuck, I can tell with every certainty that the E-line mod was invented for the purpose of avoiding a dynamic rear riser stall for times when a competitor feels he just "must" dig on rears as opposed to simply bailing to toggles. Is digging on rears the right thing to do? No, not in my opinion, but that does not mean that some people go to extraordinary lengths to stay on rears, regardless of dig. Your one high-tier name is: Jay Moledski, the creator of that mod. As competitors become more attuned to the stall limits on rears, they are willing to push it a bit further. I have, to date, not dynamically stalled my Velo on rears, but I have come damn close (one PST Panama City distance round) when I really got deep in the corner yet cranked it out on rears. Others have tried and failed in competition. Joe Bennet, Andy Anderson, and Andy Farrington have all dynamically stalled on rears in competition. When it's "all or nothing", some people are willing to risk such stalls in hopes of placing high. Likewise, competitors at the highest level are also pushing it to the opposite extreme, often getting "vertical extensions" and getting zeros on rounds because they were too lean; just barely missing the tops of the entrance gates in hopes of blistering down the course, right in the meat of the powerband. I have seen and continue to see both extremes in competition.

mike

Girls only want boyfriends who have great skills--You know, like nunchuk skills, bow-hunting skills, computer-hacking skills.

[AggieDave 6]

Ok, so I remembered what Chuck said incorrectly.

*shrug* it happens.

The rest of the post is still valid.

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

[mnischalke 0]

So what part of the post is valid?

I mean, are we talking about what some of the pros do?

Are we talking about the belief that a canopy with a shorter recovery arc makes a canopy more tolerant?

Are we talking about me needing more canopy training because what the three pro swoopers and one canopy manufacturer have taught me has been wildly misinterpreted in my twisted little brain?

I am beginning to get a little lost (trying to learn Premier and this rum&coke ain't helping) on what part of the post we're actually talking about. help a brother out, if you please.

mike

Girls only want boyfriends who have great skills--You know, like nunchuk skills, bow-hunting skills, computer-hacking skills.

[Canuck 0]

OK, this goes back a few posts now, but you're still asking me what I meant about a canopy with a short recovery arc being more tolerant. That question has already been answered - low turn, intentional or not, no attempt from the pilot to fix the situation. The fast recovering canopy is more likely to return to level or survivable decent rate than the slow recovering canopy. Think it doesn't happen? Read the fatality reports - there have been several where witnesses report no attempt to flare after a low turn, and I've seen it with my own eyes. We can't ask these people why they didn't flare, because they're dead...

Now, go to the PD website and watch all the videos of Heath, Jay, and Ian at the IPC World Meet. I just did, and there is not one single video which shows any of them doing anything that would resemble digging. Hell, half the time you can't even detect the rear riser input.

Funny how we interpreted Chucks post differently. I picked up on the parts where he said digging is not the right thing to do and how the e-line mod is there for those times when you absolutely have to dig but don't want to sacrifice the round by hitting the toggles.


Canuck

[alan 1]

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Sure, you'll give yourself a highspeed stall and you'll slam into the deck.

Good point. Just a bit of semantics, but I think the proper term is dynamic stall.

Your point does address the issue of a canopy with a shorter recovery arc, such as the Stiletto. I think the perceived advantage of the shorter arc in recovering and planing out quicker is offset by the tendency of most people trying to dig out of the corner and thereby inducing the stall you refer to. The Stiletto with the shorter recovery arc will also respond to a given toggle input more and make it a little easier (more likely ?) to induce a dynamic stall. I've seen it quite often, low turn, try to dig it out and a bad situation just got worse.

Some situations are not recoverable, but I have seen far too many that were, but instead of remaining calm and using smooth controlled toggle input, the pilot digs in a little and as he/she realizes it is not working, they panic and sharply dig in even more. The result is a dynamic stall and injury. Many of those would have been recoverable with a smooth application of brakes to some point far less deep than the hips.

alan

[alan 1]

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The Stiletto is probably the most notoriously short (negative for those who like to use the term) recovery arc canopy

Just a typo I expect, but short recovery arc equates to positive, not negative as stated above.

alan

[alan 1]

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Nevertheless, lets take a shitty hypothetical situation. Person is flying a Stiletto loaded at 1.8, gets cut off, and whips a 180 at 600 feet. they get to say "oops, I turned too low." Under a Velocity at the same loading, they don't get to say anything before they hit the ground.

I wouldn't be so quick to just accept this. Too many assumptions. Yes, the Velo has a longer recovery arc but it is also a more efficient airfoil, so if flown properly it can be made to recover to level flight very quickly after yanking the toggle to do that emergency 180. That is not to imply that you cannot accomplish the same thing with a Stiletto, they both do the same thing, just at different rates, so pilot reaction time and control are critical factors.

I can yank a toggle on my VX, do a 180, stop the turn, climb 25' or more and return to level flight or even do a barrel role with considerably less than 200' of altitude loss and never come close to any kind of stall.

alan

[alan 1]

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How bout this one: 90 front riser right turn from at 300 ft. Get out of the turn too soon with no further input and the canopy planes out with no toggle or riser input and slow-speed stalls 30ft above the deck.

You might want to review what a stall is and the correct terminology. I think what you are trying to refer to is a static stall when you say slow-speed. A stall by definition is when an airfoil exceeds it's critical angle of attack. The boundry layer of air flow separates from the surface of the airfoil and lift is lost. There is a little burble of turbulent air at the trailing edge of the airfoil and as the AOA increases, this burble moves toward the leading edge. When it gets near the thickest part of the airfoil, usually about 30% back from the leading edge along the chord line, The air delaminates and the airfoil loses all lift and stops flying. A stall can happen at any airspeed.

A static stall occurs when you gradually increase the AOA and make no other adjustments. The airfoil will settle into a new slower airspeed and static flight at the new AOA. Continued slow, smooth increases in the AOA will eventually get you past the critical angle and the airfoil will stall. It will usually give some warning by getting very mushy. You canopy scenario at 300' will result in a canopy that gets mushy and will momentarily "porpoise" a bit to seek a static state of flight with neutral control inlut. It will not stall, unless there is something else going on.

An accellerated stall happens when you keep increasing the AOA while trying to maintain your airspeed. The airfoil will still stall once it has exceeded it's critical angle of attack, which by the way is determined by the angle the relative wind hits the airfoil relative to the chord line. You have a higher airspeed, but the airfoil still stalls.

A dynamic stall is a whole new and dangerous beast. This type of stall appears when you effectively increase the wing loading of the airfoil by doing a manuever that adds a "G" force load to the airfoil. This means the airfoil is effectively supporting more weight and that reduces the AOA that it will stall at. So here we have a manuever at a relatively higher speed, inducing "G"s, meaning it is supporting a heavier wing load, with a shallower critical AOA. Now, during that manuever, a rapid jerky control input causes a rather abrupt and dramatic increase in the AOA of the airfoil that is now moving fast but supporting extra weight because of the induce G's. All of these factors combined result in a dynamic stall, what some are mistakenly referring to as a high-speed stall.

Bottom line is, the canopy scenario you give at 300' and recovers at 30' will just porpoise a little as it seeks to return to a static state of neutral flight, it will not "slow-speed" stall as you call it.

I'm not sure what they taught you in the four canopy classes you claim to have taken, but there seems to be an indication that there was some deficiency either on their part or yours, with respect to basic aerodynamics of canopy flight.

alan

[skysaintj 0]

Hi i have obviously ran accross this discussion and just feel that certain canopies are made for swooping and if you are a swoop addict you need to do your homework and see whats outhere...personal experience has shown me that cross braced canopies seems to be the better option example the velocity has a longer pendilum and because of this you can start your frontriser turn higher which i feel is already a safer option the canopy depending on size generates alot of speed because of the time that it is given to do so and the cross braced design is a much harder wing which makes recovery if needed easier ...toggle turns are just stupid , to much of a commitment etc...front riser turns are better because of the fact that you can let go of the riser halfway through the turn if you are to low and even if you end up going downwind you will walk away which means you can have another go at it....

If at first, the idea is not absurd, then there is no hope for it

[mnischalke 0]

Yeah, that was my bad for using the incorrect terminology (modifier) for the stall. I should have used the word static in place of the words slow-speed. Sorry if it was misleading.

Thanks for the correction.

mike

Girls only want boyfriends who have great skills--You know, like nunchuk skills, bow-hunting skills, computer-hacking skills.