So my suggestion is, don't break your weak link and it won't cause you any problems.
Would you tell that to Jonny Durand, who (among others) broke at least one weak link at Big Spring?
Even a 'perfect pilot' will break a 5 lb weak link. So where's the cut off breaking strength above which all weak link breaks become pilot error? Keep in mind that the tension on a weak link will vary depending on bridle configuration, glider, pilot/glider weight, and tug climb rate, so be sure to factor those in the computation.
If all weak link breaks are pilot error, perhaps you can point out the error here (password = 'red'):
https://vimeo.com/17472550
So my suggestion is, don't break your weak link and it won't cause you any problems.
Would you tell that to Jonny Durand, who (among others) broke at least one weak link at Big Spring?
Yes
Zack wrote:
Even a 'perfect pilot' will break a 5 lb weak link. So where's the cut off breaking strength above which all weak link breaks become pilot error? Keep in mind that the tension on a weak link will vary depending on bridle configuration, glider, pilot/glider weight, and tug climb rate, so be sure to factor those in the computation.
I "pro-tow" Sport 2 155, U2 160, and now a Climax 14. I've weighed between 195 and 230lbs over the past few years. I've towed behind The Dragon Fly (from 2 stroke to 4 stroke turbo, about 8 or 9 different ones.) Kolbs and a Challenger at Hang Glide Chicago, and a trike at our home field. I was towing behind the Challenger when I broke my last link. 4 minute tow to 900'
The white and green line that most places use is fine for the weight ranges I have been and the gliders I have flown behind the tugs that have provided my tows. I can't say much more for anyone else.
Zack wrote:
If all weak link breaks are pilot error, perhaps you can point out the error here (password = 'red'):
https://vimeo.com/17472550
Zack
Never said that they were pilot error. I just said don't break them and you won't have an issue.
Tom Noddy said "Bubbles will last forever if they don't break."
Heard him say that when I was about 7 or 8 and kind of liked it.
As far as the video.
Obviously an early morning tow. (Not much thermal activity yet I would guess) So the tow would have been a fairly smooth tow, or maybe there was some wind and mechanical turbulence. (The tuft on your nose wire doesn't seem to show much ground wind.)
I do see the tug move up a little, but not enough to warrant the large input you made. (Bar 18-20" forward, from abdomen to almost above your head.)
So since you asked for it, my opinion is YOU did cause the weak link to break. Don't be angry, you asked for my opinion and I gave it. I could very well be 100% wrong. _________________ Airborne Climax 14 (C1)
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Never said that they were pilot error. I just said don't break them and you won't have an issue.
I'm afraid your point is lost on me, then. Did you have one, or was the statement meant purely in jest?
CHassan wrote:
As far as the video.
Obviously an early morning tow. (Not much thermal activity yet I would guess) So the tow would have been a fairly smooth tow, or maybe there was some wind and mechanical turbulence.
It was actually around 3:30 PM. Thermal and mechanical turbulence (it was ridge soarable). After the break the tug pilot commented (as a possible explanation) that conditions were rowdy.
CHassan wrote:
I do see the tug move up a little, but not enough to warrant the large input you made.
The GoPro's wide angle distorts distances. I've found tug movements are greatly understated in shots like this. But what the tug is doing in the video, or whether the input was warranted, isn't important...what's important is if an input like this could ever be warranted in some set of circumstances.
CHassan wrote:
So since you asked for it, my opinion is YOU did cause the weak link to break.
I agree. That's why that was the last time I flew with 130 lb line. Inputs like the one exhibited in the video are common in rowdy conditions. I no longer worry about being dumped because of them.
You had a thing and it broke needlessly.
You didn’t want the thing to break needlessly.
You replaced the thing with a stronger thing.
Now the thing doesn’t break needlessly.
You had a thing and it broke needlessly.
You didn’t want the thing to break needlessly.
You replaced the thing with a stronger thing.
Now the thing doesn’t break needlessly.
And now the thing might not break when you need it to...
Given the choice, I'd rather it break when I don't need it than not break when I do... but I really don't want to open this can of worms.. A weaklink break should be a non-event, if it's an event, I'd say the problem is with the pilot not the "thing"
You had a thing and it broke needlessly.
You didn’t want the thing to break needlessly.
You replaced the thing with a stronger thing.
Now the thing doesn’t break needlessly.
Concise, logical and absolutely the correct thing to do.
However, if you had added ….
“And remove the pilots release at the same time”
frankly, that would have been sh**.
........
But the gentleman quoted above didn’t add that line so a pilot at the top end with his beefed up weak-link AND a release is going to suffer … what?
Is he not a perfect pilot able to release before he gets into trouble or does that logic not work at the top?
Surely a lockout can only be due to a crap pilot and is basically a non event.
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Can someone help 'dumb it down' for me? I cannot exactly follow the debate... too many words and not always on the point.
As far as I can tell, the two sides of the debate are:
1. Weak links should break during lockout, or other extreme towing circumstances, thus saving the pilot's bacon. Sure, a weak link that is weak enough to break during lockout may also break at random, unpredictable times but that is ok with me because I feel safer overall knowing that I have the weak link as a backup release mechanism.
and on the other side
2. Weak links should never break unless the glider and/or tug is about to fail structurally. This is because a weak link that is any weaker may break at random, unpredictable times and that is very dangerous. _________________ http://pjwings.blogspot.com/
You had a thing and it broke needlessly.
You didn’t want the thing to break needlessly.
You replaced the thing with a stronger thing.
Now the thing doesn’t break needlessly.
I started using a stronger link because I had finally arrived at an understanding of what a weak link is for and what it can and cannot do. It just so happened the break on video occurred around the same time.
ksykes wrote:
And now the thing might not break when you need it to...
Not a chance. It only needs to break before the glider, and the glider will never be anywhere near stressed with the weak link I'm using.
If you think the weak link might 'need' to break under some other circumstances, please tell us when a weak link should break and how you determine the breaking strength that will ensure it does in those circumstances.
I think you have the right general idea, but I have to correct and clarify some things. I say 'think' because I can only speak for the side I'm on. I have a hard time getting the other side to tell me when a weak link should break or what its breaking strength should be (as you might have been able to tell).
pjwings wrote:
Weak links should break during lockout...
Stronger weak links will still break during a lockout if the pilot doesn't release. It will just take slightly longer.
pjwings wrote:
Weak links should never break unless the glider and/or tug is about to fail structurally.
I wouldn't say 'about to fail'...they should break well below that to leave a safe margin. I'd say they should break well above anything that would normally be encountered on tow but well below what would break the aircraft. That allows a pretty big range.
pjwings wrote:
This is because a weak link that is any weaker may break at random, unpredictable times and that is very dangerous.
Weak link breaks are usually nothing more than inconveniences. But with just the right combination of factors they could be much worse.
pjwings wrote:
...a weak link that is weak enough to break during lockout...
Lockouts only matter near the ground (at altitude, the weak link, no matter how strong it is, will break and the glider recover if the pilot doesn't release). If a lockout occurs near the ground, you do not want to rely on any weak link to save you. If it's strong enough to get you to altitude, it's strong enough to permit a very bad attitude that could be catastrophic near the ground (as illustrated by the earlier video I posted). That's why they say the weak link isn't there to protect the pilot.
For any given lockout that ends in a weak link break, there's a breaking altitude below which the pilot will not be able to prevent a crash. If you use a stronger weak link, that altitude will be a little higher. Using the weaker weak link will only matter if the lockout occurs between those two altitudes, so you'd basically be gambling that at some point you'll need it to break in this range in exchange for a much greater chance of it breaking at a bad time.
Lockouts only matter near the ground (at altitude, the weak link, no matter how strong it is, will break and the glider recover if the pilot doesn't release). If a lockout occurs near the ground, you do not want to rely on any weak link to save you. If it's strong enough to get you to altitude, it's strong enough to permit a very bad attitude that could be catastrophic near the ground (as illustrated by the earlier video I posted). That's why they say the weak link isn't there to protect the pilot.
For any given lockout that ends in a weak link break, there's a breaking altitude below which the pilot will not be able to prevent a crash. If you use a stronger weak link, that altitude will be a little higher. Using the weaker weak link will only matter if the lockout occurs between those two altitudes, so you'd basically be gambling that at some point you'll need it to break in this range in exchange for a much greater chance of it breaking at a bad time.
This is GOLDEN for all of us that tow (I tow a lot on a PL rig). It holds true for ANY towing system. Zack you are doing a great job of shining the light on the weaklink issues. It's really that simple to me. I am going to start using 205 leech. I was using 4 strands of 130 kite string (standard AT stuff). Thanks
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The purpose of the weak link is the same for any tow method, but what you quoted is not entirely applicable to payout winch towing because it's tension controlled. While a weak link will eventually break at some point in the course of an aerotow lockout, this is generally not the case on a payout winch because the drum will just pay out faster rather than allow tension to increase. It thus makes even less sense to use lighter weak links with payout winch towing.
blindrodie wrote:
I am going to start using 205 leech. I was using 4 strands of 130 kite string (standard AT stuff).
For AT or PL? How many strands of 205? At the end of a V bridle or directly engaging the towline?
Four strands of 130 will break around 200 lbs (not the 520 often assumed).
Here in Houston we use four strands (two loops) of 205 leech line directly engaging the towline for platform towing. We've tested this configuration to break around 600 lbs.
Thanks Zack! That clarifies it well. Seems like a very subtle difference to raise such ire. Either way unplanned breaks are possible. Either way the weak link will pop long before the aircraft does. It just comes down to a matter of degree.... And which set of variables a pilot is most comfortable towing with. _________________ http://pjwings.blogspot.com/
Thanks Zack! That clarifies it well. Seems like a very subtle difference to raise such ire. Either way unplanned breaks are possible. Either way the weak link will pop long before the aircraft does. It just comes down to a matter of degree.... And which set of variables a pilot is most comfortable towing with. _________________ http://pjwings.blogspot.com/
I suspect nearly all pilots using a good release and following USHPA's weak link recommendation will never see a weak link break - just as in the sailplane world.
It thus makes even less sense to use lighter weak links with payout winch towing.
Exactly. I was going to say that with the payout you just keep on locking out as the weak link fails to pop. We are all about the PIC releasing BEFORE anything gets too out of whack. And if it does finally break you get a whip stall maybe or you just end up low, fast and going downwind!
Quote:
For AT or PL? How many strands of 205? At the end of a V bridle or directly engaging the towline?
For PL. At least three at the end of my 3 string release, directly engaging the towline loop.
Quote:
Four strands of 130 will break around 200 lbs (not the 520 often assumed).
Yes I have personal experience with that knowledge.
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The ideas below seem well stated. I use that greenstripe stuff, what is it, 130 pound test, for the weak links on a 3 point (shoulders and keel) aerotow setup. I'm fairly light and fly smaller gliders. I don't have a lot of time towing in REALLY rowdy air but all my weak link breaks have been in severe lockouts as far as I can recall. The most recent one, last winter, put a heck of a load on the glider, more than I would ever intentionally allow. The high G-load made it harder to for me to get my hand quickly to the release, and the glider rolled to quite a steep bank, and the loads rose much higher than I intended before I hit the handle. I thought I did release but the weak link must have broken just as I pressed the handle, because the weak link was found to be broken after landing. The weak link did its job. The glider didn't break. Down low, I would have initiated reaching for the release much sooner-I hope! - or else I would have slammed into the ground steeply banked either shortly before or after the weak link broke. A weak link should break in a lockout eventually, but if it is strong enough not to constantly breaking in turbulence, it seems unrealistic to expect it to break until the lockout is rather well along in progress.
Based on my cumulative experience so far I would opt for a SLIGHTLY weaker weak link (those loads got alarmingly high!). A heavier pilot towing with pro tow would need a somewhat heavier link for the same breaking load factor.
How to adjust for variations in pilot weight and glider size?
Perhaps best to simply adjust according to the max pilot weight allowed for the wing, and for style of tow bridle, and nothing else? On any given wing with a given weak link, a heavier pilot will tend to experience a weak link break at a lower g-load in turbulence, but turbulent gusts will also impose fewer g's on the heavier pilot, and with either pilot, the wing will end up being limited to the same total load as expressed in pounds rather than G-loading, it seems to me...
Zach wrote:
pjwings wrote:
Weak links should never break unless the glider and/or tug is about to fail structurally.
Lockouts only matter near the ground (at altitude, the weak link, no matter how strong it is, will break and the glider recover if the pilot doesn't release). If a lockout occurs near the ground, you do not want to rely on any weak link to save you. If it's strong enough to get you to altitude, it's strong enough to permit a very bad attitude that could be catastrophic near the ground (as illustrated by the earlier video I posted). That's why they say the weak link isn't there to protect the pilot.
For any given lockout that ends in a weak link break, there's a breaking altitude below which the pilot will not be able to prevent a crash. If you use a stronger weak link, that altitude will be a little higher. Using the weaker weak link will only matter if the lockout occurs between those two altitudes, so you'd basically be gambling that at some point you'll need it to break in this range in exchange for a much greater chance of it breaking at a bad time.
A weak link should break in a lockout eventually, but if it is strong enough not to constantly breaking in turbulence, it seems unrealistic to expect it to break until the lockout is rather well along in progress.
It is unrealistic to expect any weak link to break before a lockout is rather well along in progress. The pilot in the scenario below released - the weak link never broke.
But don't bet a stronger weak link will make that much of a difference anyway.
Quote:
deltaman, 5/25/2012
I miss opportunity to be aerotowed in my mountains but 2 months ago we spent 4 days teaching AT to 12 pilots in 2 points. All had 190kg weaklink (220kg on tug side).
One of them oscillate and start to lockout. I said by radio : (time to) release, he did it (JoeStreet release), but 1ms to late.. the weaklink was just blowed.
and no unexpected wl failure in 90 AT.
I'm confident in this way to think wl..
Once tension starts to spike in a lockout it will spike quickly. But near the ground you may already be past the point of survival by the time that happens - regardless of your weak link breaking strength. As much as we'd love to believe otherwise, there is no direct relationship between towline tension and desirability of being off tow. That is why we cannot expect the weak link to do anything other than protect the glider from overloading by excessive tension.
aeroexperiments wrote:
I thought I did release but the weak link must have broken just as I pressed the handle, because the weak link was found to be broken after landing.
What you're describing is not uncommon with spinnaker releases. The gate stresses the weak link during release, especially under high loads. It's likely it broke because you released.
aeroexperiments wrote:
The weak link did its job. The glider didn't break.
The weak link could have been far stronger and it still would have done its job. But you seem to think it has another job - that of a release.
aeroexperiments wrote:
A heavier pilot towing with pro tow would need a somewhat heavier link for the same breaking load factor.
Not that you stated otherwise, but a pilot towing one point ('pro tow') will need a weaker weak link than when he's towing two (three) point to achieve the same tension limit.
aeroexperiments wrote:
How to adjust for variations in pilot weight and glider size?
If you understand what a weak link is for, you would understand this question is flawed. You only need to adjust for variations in gliders' load capacity - just like the FAA tells you.
Now to the heart of this matter...
aeroexperiments wrote:
The high G-load made it harder to for me to get my hand quickly to the release...
aeroexperiments wrote:
Based on my cumulative experience so far I would opt for a SLIGHTLY weaker weak link...
Maybe you should instead opt for a release you don't have to reach for.
aeroexperiments wrote:
...all my weak link breaks have been in severe lockouts...
You haven't said why you didn't release before those breaks occurred. Assuming you actually desired being off the line, I can only think of two reasons: you couldn't get to your release in time or your release didn't work. Assuming either/both of these are the case (let me know if I'm wrong)...
You already know that a lockout near the ground can kill you if you wait for even a weak weak link to break. You're rolling the dice if you think any weak link might ever save you. Don't look at your cumulative experience - look at the worst case.
Having to reach for a release does more than increase the time between deciding to release and actually releasing. You need every bit of both hands to resist a lockout. Take a hand off the bar for an instant and your attitude will immediately worsen - raising the altitude below which survival is not possible.
And if you didn't survive when a better release might have saved you, the accident report will inevitably attribute the accident to pilot error and the pilot waiting too long to release (with no mention of the type of release used).
Dumbing down a weak link to compensate for an inadequate release is like lowering your vehicle's air bag trigger point to compensate for faulty brakes. Releases are absolutely critical to safe towing...and a weak link is not a release.
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