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Question about coming back from a long spot

 

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Quagmirian  (A 110392)

Dec 8, 2012, 1:32 AM
Post #51 of 72 (2496 views)
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Re: [DocPop] Question about coming back from a long spot [In reply to] Can't Post

When people talk about about using brakes to 'improve your glide' when coming back from a long spot I've always struggled to understand whether this is purely because you stay in the air longer or if your canopy's glide ratio is affected at all.


pchapman  (D 1014)

Dec 8, 2012, 3:21 AM
Post #52 of 72 (2483 views)
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Re: [Quagmirian] Question about coming back from a long spot [In reply to] Can't Post

In reply to:
I've always struggled to understand whether this is purely because you stay in the air longer or if your canopy's glide ratio is affected at all.

No time for a careful answer but it can be "both". The canopy's descent rate is lower, which is the big thing. But forward speed is down too, the actual glide ratio (thru still air) is probably better, if one is comparing zero to moderate brakes. Somewhere in deeper brakes though, there the glide ratio might get worse. Even then, one might still be doing better in getting back, having a better glide ratio over the ground. (If it is windy enough, a piece of confetti will get back to the DZ, even though it's glide ratio is roughly straight down in still air...) As usual, things depend somewhat on canopy style, as to at what point adding brakes makes the glide ratio in still air worse and not better.

To really understand glide ratio in still air and the glide in wind, one needs to understand "glide polars" and how to shift them for wind. If one found some glider pilot resource on the web that would help, but I don't know of any site off hand.

In typical cases, what one loses in forward speed from going to brakes, is more than made up for by having lower descent rate, when there's a tailwind that's giving you "free forward speed" over the ground. But that's when it is fairly windy. When winds are lower the answers are less simple regarding what canopy controls will be best for your canopy that day.

In practice once can of course try to use the accuracy trick of seeing whether one's target of the DZ is moving up or down in one's visual field, and play with brakes or risers to see what works with the current conditions on your canopy.


davelepka  (D 21448)

Dec 8, 2012, 5:15 AM
Post #53 of 72 (2471 views)
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Re: [DocPop] Question about coming back from a long spot [In reply to] Can't Post

Quote:
What exactly was the context?

What was the context of your statement? You made the reference to swoopers using rears, and that it must be more efficient or they wouldn't be doing it, but I think you're only dealing with half of the story.

Rears can be an asset, but only to a point. When you pull down on the rears, there is a portion of the travel that will flatten out the trim without distoring the canopy. Essentially, the inflated wing pivots downward off the A line attachment points, which effectively flattens out the glide.

However, this only works (well) for a very small portion of the travel. What happens if you pull too hard, is that the B lines will being to slack, and a crease will form in the canopy. At this point, you're no longer simply re-trimming the canopy, now your bending it half and pulling the rear half down into the wind, aka creating drag.

When swooping, that first little bit of travel actually gets bigger becasue of airspeed. When the pressurization is up, like at the tail end of a big turn, your canopy will hold it's shape longer than when pulling the rears in slow flight. On top of that, you have the concept of control effectiveness going up with airspeed, so again, at the bottom of a big turn, a little goes a long way.

So when it comes to ultra-high speed flight, and for minor trim changes to level your canopy for a swoop, the rears are the ticket. Once you're into them for the swoop, it makes the most sense to fly them out to a degree, but as it's commonly known, you don't fly them out to 100% just before the stall before you transition, you need to dump them and go to toggles at about 80% of what they have to give.

When it comes to steady-state flight at slow speeds, the brakes are far more reliable in terms of efficiency, and more forgiving in terms of the jumpers need for accurate inputs (both being good things when trying to cover long distances over 'long' periods of time).


(This post was edited by davelepka on Dec 8, 2012, 5:16 AM)


DocPop  (C License)

Dec 8, 2012, 8:02 AM
Post #54 of 72 (2447 views)
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Re: [davelepka] Question about coming back from a long spot [In reply to] Can't Post

I agree with you Dave.

The context of what I wrote was that I was disagreeing with billvon's blanket statement about the drag induced by rears vs toggles:

Quote:
Pulling down part of the tail does indeed add some drag. Distorting the entire canopy with rear risers adds more drag.


I also gave the following caveat in my statement in post 44:

Quote:
To be clear, in the long spot scenario, I am talking about a "touch" of rears, not a full plane-out.

My point being that used correctly, rears will improve glide ratio with less drag than toggles (or "brakes" as the are also known for some bizarre reason!Wink)


muff528  (D 17609)

Dec 8, 2012, 8:29 AM
Post #55 of 72 (2445 views)
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Re: [Tuna-Salad] Question about coming back from a long spot [In reply to] Can't Post

In reply to:
My $0.02 if you are on a long spot immediately start looking for and select an alternate landing area. People get hurt when they "think" they can make it back but are not sure then end up being unprepared.

Yep. I've always tried to spot the landing area and try to see which direction it appears to be going. If it gives the illusion that it is "ascending" towards the horizon (or away from me), I know I'm not going to make it and I look for an alternate landing area. If it appears to be "descending" (moving down and away from the horizon but towards me) I'll probably make it OK. Also, I'm in the release-the brakes-and-check-controls-first camp. The outcome of the control check would probably influence other decisions I might have to make.


skyjumpenfool  (Student)

Dec 8, 2012, 11:01 AM
Post #56 of 72 (2418 views)
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Re: [muff528] Question about coming back from a long spot [In reply to] Can't Post

In reply to:
Also, I'm in the release-the brakes-and-check-controls-first camp. The outcome of the control check would probably influence other decisions I might have to make.

Agree and disagree. If I've pulled at normal pull altitude and the opening appears to have gone smoothly, I like to look around for traffic while harness turning towards the DZ before brake release. I can also check my slider and give the canopy a good look during this time.

Since this only takes 2-3 seconds, I should not have lost a lot of altitude (under a good canopy) in that time. If I have to go to EP's, I have a better understanding of where I, and others, are. Plus, I'm now flying in the correct direction while doing control checks.


muff528  (D 17609)

Dec 8, 2012, 11:29 AM
Post #57 of 72 (2409 views)
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Re: [skyjumpenfool] Question about coming back from a long spot [In reply to] Can't Post

In reply to:
....... I like to look around for traffic while harness turning towards the DZ before brake release. I can also check my slider and give the canopy a good look during this time.

Since this only takes 2-3 seconds, I should not have lost a lot of altitude (under a good canopy) in that time. If I have to go to EP's, I have a better understanding of where I, and others, are. Plus, I'm now flying in the correct direction while doing control checks.

Yeah, I agree with all that stuff immediately after opening. But then, for the flight back to the DZ, I agree with releasing the brakes first rather than leaving them stowed in hopes that that would help flatten the glide slope a little ...and then finding out, when the brakes are finally released, that there is a control problem.


D22369  (D 22369)

Dec 8, 2012, 1:07 PM
Post #58 of 72 (2391 views)
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Re: [Deimian] Question about coming back from a long spot [In reply to] Can't Post

maybe it is plainly a very stupid question?
Quote:

damned good question if ya ask me,
you have some great answers from others, only thing I can think of to add is to take it to the air with another person on a similarly loaded canopy and use them as a point of reference to see what full flight, brakes, rear risers and front risers will do for you. not saying to attempt a dock or anything *(crw) just just flying in proximity

I used to film those crazy CRW guys on my stiletto and found a use for each configuration - I learned a tremendous amount about each flight configuration in those first few jumps with them.

Roy


kallend  (D 23151)

Dec 8, 2012, 2:25 PM
Post #59 of 72 (2379 views)
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Re: [muff528] Question about coming back from a long spot [In reply to] Can't Post

In reply to:
In reply to:
....... I like to look around for traffic while harness turning towards the DZ before brake release. I can also check my slider and give the canopy a good look during this time.

Since this only takes 2-3 seconds, I should not have lost a lot of altitude (under a good canopy) in that time. If I have to go to EP's, I have a better understanding of where I, and others, are. Plus, I'm now flying in the correct direction while doing control checks.

Yeah, I agree with all that stuff immediately after opening. But then, for the flight back to the DZ, I agree with releasing the brakes first rather than leaving them stowed in hopes that that would help flatten the glide slope a little ...and then finding out, when the brakes are finally released, that there is a control problem.

There was a a fatality on a 124 way at Perris some nine years ago that is thought due to a common habit at that time on big ways of not releasing brakes until under 1,000ft. The jumper had her excess brake line hang up on a Slink connector. There is a long thread in the "Incidents" forum about it.

1,000ft is too low for a safe cutaway if you have a toggle or steering line or other steering related problem that only becomes apparent when you go to release the toggles.

You should be sure by your hard deck that you have a good, STEERABLE canopy over your head.


rmarshall234  (D 18793)

Dec 8, 2012, 9:49 PM
Post #60 of 72 (2324 views)
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Re: [Deimian] Question about coming back from a long spot [In reply to] Can't Post

I can tell you what Jonathan Tagle would say, from experience:

"I don't know. Go try it and find out."


jonathan.newman  (D 30644)

Dec 9, 2012, 7:43 PM
Post #61 of 72 (2248 views)
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Re: [pchapman] Question about coming back from a long spot [In reply to] Can't Post

Try this, Mr. pchapman, and from a Canuck website, with pictures, and animation, no lessWink http://avia.tion.ca/documentation/polar/

Once you understand the polar curve, come back and keep reading.

Our canopies actually have two different polar curves. One comes from using only riser input, and the other comes from using only toggle input. Full flight seems to be somewhere on the right side of the curve. If I pull front risers, I can increase my airspeed and increase my rate of descent -- thus moving to the right and down on the curve. If I pull rear risers or toggles, I will both slow my airspeed and my descent rate -- moving left on the curve. (this works up to the point where the wing begins to mush and then stalls)

So, if you can trust what the glider pilots believe, then if you are trying to make it back to the DZ with a tailwind, then use rear risers or brakes to increase your glide angle. And if you have a headwind, then picking up speed with front risers will get you farther.

That's great in theory, but since we have neither GPS nor variometers, and our airspeed is judged by our ears, we need some way to gauge how much toggle or riser input to provide.

That is where the "accuracy trick" comes into play.

Now, before anyone jumps on me to say that they took a canopy course and learned sumthin' different, let me say that I took a Flight1 course and was taught brakes with a tailwind, rears with a headwind. In theory, I disagree with that, and will try to play around with it while I'm jumping this week.


Premier slotperfect  (D 13014)

Dec 10, 2012, 2:51 AM
Post #62 of 72 (2218 views)
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Re: [jonathan.newman] Question about coming back from a long spot [In reply to] Can't Post

Quote:
Now, before anyone jumps on me to say that they took a canopy course and learned sumthin' different, let me say that I took a Flight1 course and was taught brakes with a tailwind, rears with a headwind. In theory, I disagree with that, and will try to play around with it while I'm jumping this week.

I will be very interested to hear the results of your experiment.

I used rear risers to recover from long spots for years. Then I took a Scott Miller course and learned that deep brakes work better - slowing the descent rate as much as possible to allow the tailwind to carry you for a longer time. I made two identical jumps using the same spot from the same altitude and was very surprised at the difference.

I used front risers to recover from being short (into a headwind) for years. Then I took a Flight-1 course and learned that a bit of rear risers and a small body position to reduce drag works better. Front risers work, but at the expense of more altitude loss, and they are more difficult to sustain over longer periods of time. I was skeptical of this at first (contrary to years of using another method), but when I got home and used this technique for real when I was in a pinch, I discovered that it really works.

The best way to see how rear risers work is flying side-by-side with another canopy. From the flight mode that matches your partner allowing you to stay in place, engage rears slightly and use a small body position and you should pull in front of your partner staying on level or climbing very slightly.

I use rears for crosswinds as well, or full flight (each with a crab), depending on how far off the wind line I am at the time.


Premier slotperfect  (D 13014)

Dec 10, 2012, 2:52 AM
Post #63 of 72 (2215 views)
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Re: [kallend] Question about coming back from a long spot [In reply to] Can't Post

Quote:
You should be sure by your hard deck that you have a good, STEERABLE canopy over your head.

+1 -- great advice.


Premier billvon  (D 16479)
Moderator
Dec 10, 2012, 9:00 AM
Post #64 of 72 (2154 views)
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Re: [DocPop] Question about coming back from a long spot [In reply to] Can't Post

>If that were the case then why would swoopers use rears to maximize their glide
>("swoop") and only switch to toggles when the airspeed drops to a point where extra
>lift (with its attendant drag increase) is needed?

Because recovering a canopy from an unstable dive to achieve maximum speed and/or distance just above the ground is different than maximizing L/D in steady state conditions.


dthames  (B 37674)

Dec 10, 2012, 10:29 AM
Post #65 of 72 (2132 views)
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Re: [slotperfect] Question about coming back from a long spot [In reply to] Can't Post

Slotperfect,

Quote:
I used rear risers to recover from long spots for years. Then I took a Scott Miller course and learned that deep brakes work better - slowing the descent rate as much as possible to allow the tailwind to carry you for a longer time. I made two identical jumps using the same spot from the same altitude and was very surprised at the difference.

Would the success of the "deep brakes" being better depend on how strong the tailwind is? I mean if your tail wind was pretty weak, wouldn't you be better off keeping the canopy's flying speed up? (rear risers)


linebckr83  (D 30571)

Dec 11, 2012, 6:28 AM
Post #66 of 72 (2030 views)
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Re: [dthames] Question about coming back from a long spot [In reply to] Can't Post

In reply to:
Slotperfect,

Quote:
I used rear risers to recover from long spots for years. Then I took a Scott Miller course and learned that deep brakes work better - slowing the descent rate as much as possible to allow the tailwind to carry you for a longer time. I made two identical jumps using the same spot from the same altitude and was very surprised at the difference.

Would the success of the "deep brakes" being better depend on how strong the tailwind is? I mean if your tail wind was pretty weak, wouldn't you be better off keeping the canopy's flying speed up? (rear risers)

Naturally yes. If your tailwind is basically nothing, floating in deep brakes will not be extremely effective as you are also slowing your airspeed down considerably while in brakes. In that configuration you are essentially "riding the wind". No wind, not much movement. Rear risers would be a better bet since you will have forward movement because of your airspeed.

What is the point where you switch gears from rear risers to riding in brakes? That's where differences in wind, windloading, and canopy trim/design come in to play. Your best best is to take yours up and play with it!


DocPop  (C License)

Dec 12, 2012, 2:38 AM
Post #67 of 72 (1955 views)
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Re: [billvon] Question about coming back from a long spot [In reply to] Can't Post

In reply to:
>If that were the case then why would swoopers use rears to maximize their glide
>("swoop") and only switch to toggles when the airspeed drops to a point where extra
>lift (with its attendant drag increase) is needed?

Because recovering a canopy from an unstable dive to achieve maximum speed and/or distance just above the ground is different than maximizing L/D in steady state conditions.

That is basically just you saying "because I said so", and is not satisfactory. I suspect you have no way to back up your original assertion.


potatoman  (Student)

Dec 12, 2012, 7:21 AM
Post #68 of 72 (1916 views)
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Re: [klippetop] Question about coming back from a long spot [In reply to] Can't Post

OK, back to the 45degree to the wind and zigzagging it, when going upwind, or wind into face to LZ.

I cannot help to think, never tried though, that it might be worthwile to do consecutive 45degree turns, rather sharply, and then still get penetration.

So, 22,5degree to the wind, do a sharp turn so you end up at 22,5 degree oposite side, BUT, increased speed from the turn should give you some penetration, once you feel penetration is now nearly over, do the same again to the other side.

I am not talking front risers, but toggles, and I know that would probably be 3steps forward two back...

I have to go and test this......


davelepka  (D 21448)

Dec 12, 2012, 7:31 AM
Post #69 of 72 (1912 views)
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Re: [potatoman] Question about coming back from a long spot [In reply to] Can't Post

Quote:
OK, back to the 45degree to the wind and zigzagging it, when going upwind, or wind into face to LZ.

The shortest distance between two points is a straight line. When dealing with a headwind, and the reduced glide it offers, you have a limited supply of 'distance' to work with. Zig-zagging will only make your trip to the LZ (or wherever you end up short of the LZ) that much longer.

On top of the that, the increase in speed you're counting on will come at the expense of altitude. Remember the limited supply of 'distance' mentioned above, your repeated turns will only wear that down even further.

It sounds more like one step back, followed by another step back.


(This post was edited by davelepka on Dec 12, 2012, 7:32 AM)


Premier slotperfect  (D 13014)

Dec 12, 2012, 8:14 AM
Post #70 of 72 (1896 views)
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Re: [dthames] Question about coming back from a long spot [In reply to] Can't Post

THe short answer is yes, but we are talking about wind conditions that provide a useful tailwind that can be harnessed. A very light or nonexistent wind does not provide a condition that allows for use of either technique. In that case, normal use of flight modes applies and you may have to pick an alternate for landing.


kallend  (D 23151)

Dec 13, 2012, 8:45 PM
Post #71 of 72 (1812 views)
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Re: [jonathan.newman] Question about coming back from a long spot [In reply to] Can't Post

In reply to:

So, if you can trust what the glider pilots believe, then if you are trying to make it back to the DZ with a tailwind, then use rear risers or brakes to increase your glide angle. And if you have a headwind, then picking up speed with front risers will get you farther.

Well, that is ONLY true IF the canopy is already trimmed for best glide. Most sport canopies, however, are already trimmed to fly steeper than best glide speed, so unless the headwind is really really strong (like you're backing up) front risers won't help.


Mac  (C 101464)

Dec 20, 2012, 3:06 AM
Post #72 of 72 (1681 views)
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Re: [slotperfect] Question about coming back from a long spot [In reply to] Can't Post

In reply to:
... and you may have to pick an alternate for landing.

Continue all along your flight to pick out alternative landing areas at each stage. Once you go over your current choice, reassess, and scope another. If you look to be putting yourself into a maybe/maybe not situation on making it back toward the end of the canopy flight, ensure you have an alternative landing zone already in the bag, do not attempt it if there isnt an alternative prior to making it back if you are still on a maybe/maybe not.

Better to land off then panic attempting to avoid something because your eye was slightly off or the conditions on the last few hundred feet changed.


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