Got bored towards the end of last season and started doing a lot of archive searches along the lines of "weak link broke" with respect aerotowing to see if any of the little bits of string served any function more useful than do the sacred back up suspension straps and hook knives.
Short answer - no.
In more depth... Most of them happen for no reason whatsoever or 'cause somebody approached the tow line with a piece of fuzz. The minuscule percentage of breaks desired should not have been necessary.
Also did enough research in the tow discussion group archives to now be one of about half a dozen pilots of the hang glider flavor who understands what a weak link is (after all these years working on these systems).
News flashes...
The allegedly overstrength weak links of Mike/Bill and Robin had nothing to do with their accidents.
and
Holly had a weak link and it worked fine.
The sole purpose of a weak link is to keep the planes at the ends of tow line from breaking up. None of the tugs sustained any damage and all three gliders were in great shape all the way to the ground.
A really flimsy weak link can easily transmit enough tension override your control authority enough to slam you into the runway and stay intact all the way to that point. And you can use that same weak link to put the tug out of control.
A weak link may fail in a lockout but there's supposed to be a pilot controlling the aircraft who should have released long before things got to that point. If you're low and waiting for that safety feature to kick in you're playing Russian roulette - kinda like waiting for the air bag to inflate instead of hitting the brakes.
Let's pretend we're sailplanes and have to fly under government standards. The FAA says we gotta have either a tow line (see Holly above) or weak links at both ends of one that fail at between eighty and two hundred percent of payload (the weight of the stuff at the back end of the tow line). Expressed another way that's about 1.40 plus or minus .43 Gs. (The USHGA AT Guidelines specify the same top end but, consistent with the junk we use, say nothing about the bottom.)
Right now if a Karren/Ayesha sort of person approaches a flight line and asks for a weak link she gets a little loop which, when installed on a two point Spectra bridle fails when the tow line tension hits about 240 pounds.
If I make the same request I get the same piece of string and end up off the bottom end of what the FAA defines as the safe range - as does anyone else who suits up, clips in, steps on the bathroom scales, and sees a number larger than 305 on the left side of the needle. What I really want is something that blows when the line tension hits 620.
So the situation is that we're using chintzy weak links as compensation for chintzy releases that we can't get to in time and may not work even if we do (see Robin above) and gumming up flight lines for relaunches during prime time with one of the Dragonflies out of commission.
We should be breaking weak links at about the same frequency as do sailplanes and that we throw parachutes - never. And if a weak link is broken it should be because someone really screwed up.
Placement...
Weak links don't belong on the end of the bridle. All two point bridles can wrap. Every one point bridle I've ever seen 'cept for the ones I've made is way too long and can wrap. Bridles are most likely to wrap when released under high loading, i.e, when it's likely to be the least convenient and the highest loading possible is at weak link failure.
If you have a weak link at the top end of your two point bridle and/or one between your aerotow (shoulder) loop and an end of your secondary/one point bridle (as, insanely, is recommended in the USHGA Guidelines) you have one or two "maybe links".
The fact that Holly had no secondary weak link was inexcusable (that's cultural - not individual). If she had been using a two point bridle and it had wrapped she would have been in exactly the same position - towing one point and using 5 G weak link.
Weak links belong on the ends of the tow line. You can pick up a safety advantage by supplementing them with links on the bridle(s) but... this is way too long already.
Here's a quote from "Towing Aloft" (Page 349)...
"I witnessed a tug pilot descend low over trees. His towline hit the trees and caught. His weak link broke but the bridle whipped around the towline and held it fast. The pilot was saved by the fact that the towline broke!"
Lesson learned - Rather than reconfigure to a system that actually works when you really need it, just keep on doing things the same way and maybe you'll keep on getting lucky.
weak links
Moderator: CHGPA BOD
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Tad Eareckson
- Posts: 304
- Joined: Wed Feb 09, 2005 8:50 am
Thanks for the response, Chris.
I stand partially corrected. I checked back and although there were a couple of early reports that the tow line broke, the later and most reliable one from Steve stated that Tex let go. I plead guilty to locking in to first impressions and am glad to have learned that the tug pilot took appropriate and timely action.
I have to modify Holly's accident category a bit but my point still stands - if the tug landed and the glider was intact before it hit the ground, the weak link was not a legitimate factor.
What is consistent with all the reports is that her primary/two point bridle didn't make it to launch. One of the points I'm trying to make is that, even if it had, she was gambling that it wouldn't wrap and, if it did, she wouldn't be needing a weak link at her end of the line. She needed to have at least one on one end of her secondary bridle.
A couple more quotes from "Towing Aloft"... Page
045
"The towline release is a critically important piece of equipment. It is the device that frees you from the towline and it must be failure-proof."
338
"The most common release emergency is when your release doesn't work."
Anybody else see a major disconnect (or, actually, lack thereof)? That was at the beginning of 1998 but we're still using the same crap.
Here's a quote in reference to 2005/06/08 at Ridgely...
"Yesterday I was LUCKY that my weak link broke on my first launch (the next two pilots after me broke theirs at the same place, a thermal breaking off at the end of the field)."
I think the Russian roulette analogy is a bit generous. I don't think you're gonna be lucky an average of five outta six times. We need to have pilot control of these situations. In accordance with USHGA Guidelines, you need to release immediately at low altitude if:
you're pointing more than 20 degrees away from the tug;
you're rolled past 45 degrees; and/or
your oscillations are getting worse.
I stand partially corrected. I checked back and although there were a couple of early reports that the tow line broke, the later and most reliable one from Steve stated that Tex let go. I plead guilty to locking in to first impressions and am glad to have learned that the tug pilot took appropriate and timely action.
I have to modify Holly's accident category a bit but my point still stands - if the tug landed and the glider was intact before it hit the ground, the weak link was not a legitimate factor.
What is consistent with all the reports is that her primary/two point bridle didn't make it to launch. One of the points I'm trying to make is that, even if it had, she was gambling that it wouldn't wrap and, if it did, she wouldn't be needing a weak link at her end of the line. She needed to have at least one on one end of her secondary bridle.
A couple more quotes from "Towing Aloft"... Page
045
"The towline release is a critically important piece of equipment. It is the device that frees you from the towline and it must be failure-proof."
338
"The most common release emergency is when your release doesn't work."
Anybody else see a major disconnect (or, actually, lack thereof)? That was at the beginning of 1998 but we're still using the same crap.
Here's a quote in reference to 2005/06/08 at Ridgely...
"Yesterday I was LUCKY that my weak link broke on my first launch (the next two pilots after me broke theirs at the same place, a thermal breaking off at the end of the field)."
I think the Russian roulette analogy is a bit generous. I don't think you're gonna be lucky an average of five outta six times. We need to have pilot control of these situations. In accordance with USHGA Guidelines, you need to release immediately at low altitude if:
you're pointing more than 20 degrees away from the tug;
you're rolled past 45 degrees; and/or
your oscillations are getting worse.
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Danny Brotto
- Posts: 709
- Joined: Mon Feb 14, 2005 9:29 pm
Weak links are not a secondary release system...
... they help and hurt under various circumstances.
http://www.dynamicflight.com.au/Reading/WeakLinks.html
Danny Brotto
http://www.dynamicflight.com.au/Reading/WeakLinks.html
Danny Brotto
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Flying Lobster
- Posts: 1042
- Joined: Fri Feb 25, 2005 4:17 pm
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Tad Eareckson
- Posts: 304
- Joined: Wed Feb 09, 2005 8:50 am
Thanks very much for that link, Danny. I feel so much less alone now. Wish I had known about this James Freeman person before I duplicated a lot of the typing he had done two years prior.
Still needs some evolution though. A small percentage of the AT crowd has figured out that the weak link belongs on the end of the tow line, but I only know of one other individual (Marco Vento in Portugal) who has figured out that a weak link is not a cheap piece of knotted string.
He's using Tost sailplane weak links which I had checked out but shied off from 'cause, while you can get inserts for whatever failure point you want, the base structure is really overbuilt for the range in which we're interested.
I subsequently developed a color coded system based upon two leechline elements stitched together, the number of stitches determining the strength rating, with a tolerances within plus or minus twenty percent. My predictions are that these things will last forever - will not wear out or degrade with use - and undesired (i.e., all) weak link breaks will become a thing of the past.
They will probably be adopted at Ridgely - we're currently working out a few options. A 400 pound weak link will keep solo gliders from 250 pounds up within specs and leave tandems no worse off than they are now. We can temporarily pop something on the end of the heavy stuff for the Karren/Ayesha sort of person.
If/when this stuff flies although you'll still be able to use your little loop of Greenspot, there will hopefully be a penalty for having your fuzz give up the ghost immediately or shortly after the Dragonfly gets loud. If you would prefer to be in charge of the decision as to when to terminate the tow, lose the fishing line and make sure the bridle eye is big enough to clear the spinnaker shackle if you're still using that crap.
This new technology is an adaptation of a concept I developed for integration with my primary and secondary bridles and started using last season. About a month ago I got slapped really hard and was able continue on behind the tug. No way I'd have survived that with a conventional weak link. It's a really good feeling to know you're not riding up on the brink of disaster the whole time.
Still needs some evolution though. A small percentage of the AT crowd has figured out that the weak link belongs on the end of the tow line, but I only know of one other individual (Marco Vento in Portugal) who has figured out that a weak link is not a cheap piece of knotted string.
He's using Tost sailplane weak links which I had checked out but shied off from 'cause, while you can get inserts for whatever failure point you want, the base structure is really overbuilt for the range in which we're interested.
I subsequently developed a color coded system based upon two leechline elements stitched together, the number of stitches determining the strength rating, with a tolerances within plus or minus twenty percent. My predictions are that these things will last forever - will not wear out or degrade with use - and undesired (i.e., all) weak link breaks will become a thing of the past.
They will probably be adopted at Ridgely - we're currently working out a few options. A 400 pound weak link will keep solo gliders from 250 pounds up within specs and leave tandems no worse off than they are now. We can temporarily pop something on the end of the heavy stuff for the Karren/Ayesha sort of person.
If/when this stuff flies although you'll still be able to use your little loop of Greenspot, there will hopefully be a penalty for having your fuzz give up the ghost immediately or shortly after the Dragonfly gets loud. If you would prefer to be in charge of the decision as to when to terminate the tow, lose the fishing line and make sure the bridle eye is big enough to clear the spinnaker shackle if you're still using that crap.
This new technology is an adaptation of a concept I developed for integration with my primary and secondary bridles and started using last season. About a month ago I got slapped really hard and was able continue on behind the tug. No way I'd have survived that with a conventional weak link. It's a really good feeling to know you're not riding up on the brink of disaster the whole time.
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Flying Lobster
- Posts: 1042
- Joined: Fri Feb 25, 2005 4:17 pm
Tad--I've said it in the past--I really admire anyone that seeks to improve safety in towing (becuase it is necessary)--but I really don't have the slightest idea what the frig you are talking about!
You toss around load limiting figures without any real asociation to breaking strengths and desired load limitations. Just because a weaklink on liftoff breaks doesn't mean it has failed to do what it's supposed to do. If you go out and get slammed in turbulence on lift-off and the weaklink breaks--the failure is not in the weaklink--but in the pilot's judgement for going at that time in those conditions and/or not responding quickly enough to unload the pressures. Them's the breaks, so to speak.
You have a predilication for using scare tactics and pure speculation in some of your accident interpretations. You seem to expect that people to accept your equipment and ideas based on your convictions before they're proven.
Please get in touch with Peter Birren and get some info on development and implementation of safety systems. When you have a safe system based on meaningful quantitative test results--then present it in a positive way. I promise I'll be the first to adapt when and if it passes muster.
marc
marc
You toss around load limiting figures without any real asociation to breaking strengths and desired load limitations. Just because a weaklink on liftoff breaks doesn't mean it has failed to do what it's supposed to do. If you go out and get slammed in turbulence on lift-off and the weaklink breaks--the failure is not in the weaklink--but in the pilot's judgement for going at that time in those conditions and/or not responding quickly enough to unload the pressures. Them's the breaks, so to speak.
You have a predilication for using scare tactics and pure speculation in some of your accident interpretations. You seem to expect that people to accept your equipment and ideas based on your convictions before they're proven.
Please get in touch with Peter Birren and get some info on development and implementation of safety systems. When you have a safe system based on meaningful quantitative test results--then present it in a positive way. I promise I'll be the first to adapt when and if it passes muster.
marc
marc
Great Googly-moo!
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Tad Eareckson
- Posts: 304
- Joined: Wed Feb 09, 2005 8:50 am
Marc, the archives are littered with examples of you not having the slightest idea what the frig people are talking about.
If you bother to read my previous posts in this thread and run some grade school arithmetic you will note that I haven't tossed around any figures. Those are FAA and USHGA figures.
I've been flying at Ridgely since its first weekend of operation. I've seen and heard of a lot of weak link breaks at takeoff but none of them has involved somebody getting slammed at that point so hard and fast that his glider was in danger of failing and he didn't have time to get to a release either ('specially if that anybody is Steve or me). John Dullahan hit the classic worst case scenario about a year ago with a release actuator mounted in the worst possible location and still did what he needed to.
Define "proven". Is the equipment you use "proven"? By whom? What standards? Where's the documentation? What muster did it pass? Do you have a clue as to the tow line tension required to break your weak link? Do you have a clue as to how much tension you're normally dealing with behind a tug?
You're not using your equipment because it passed muster. You're using it 'cause a long time ago somebody at the only shop in town tossed together a half baked idea and sold lotsa them.
Where do you come off with the assumption that I DON'T "have a safe system based on meaningful quantitative test results"? I've offered several times on this server in the past couple of years to provide documentation to whomever wants it. It's up to 117 pages now. I don't recall any requests from you (or Jim, for that matter). The late Reverend Falwell made much more powerful arguments preaching from and to points of ignorance.
You still in the Skysailingtowing group? Did you bother to read my posts or download the file I put up last winter (he asks rhetorically)?
It appears that Peter Birren is the only one who did.
And yeah, I've read Peter's stuff and corresponded with him. I got turned onto the closed bridle way of doing things by him. His system takes care of some vulnerabilities inherent in our opening bridles but you gotta reach for the lanyard and I can make a pretty good case that in the real world my system is safer. We've both perfected things as good as they're gonna get in our respective fields and we're not gonna learn anything more from each other.
By the way - I don't do speculation and convictions. I do accident reports and physics. If you have evidence to the contrary please cite it.
If you bother to read my previous posts in this thread and run some grade school arithmetic you will note that I haven't tossed around any figures. Those are FAA and USHGA figures.
I've been flying at Ridgely since its first weekend of operation. I've seen and heard of a lot of weak link breaks at takeoff but none of them has involved somebody getting slammed at that point so hard and fast that his glider was in danger of failing and he didn't have time to get to a release either ('specially if that anybody is Steve or me). John Dullahan hit the classic worst case scenario about a year ago with a release actuator mounted in the worst possible location and still did what he needed to.
Define "proven". Is the equipment you use "proven"? By whom? What standards? Where's the documentation? What muster did it pass? Do you have a clue as to the tow line tension required to break your weak link? Do you have a clue as to how much tension you're normally dealing with behind a tug?
You're not using your equipment because it passed muster. You're using it 'cause a long time ago somebody at the only shop in town tossed together a half baked idea and sold lotsa them.
Where do you come off with the assumption that I DON'T "have a safe system based on meaningful quantitative test results"? I've offered several times on this server in the past couple of years to provide documentation to whomever wants it. It's up to 117 pages now. I don't recall any requests from you (or Jim, for that matter). The late Reverend Falwell made much more powerful arguments preaching from and to points of ignorance.
You still in the Skysailingtowing group? Did you bother to read my posts or download the file I put up last winter (he asks rhetorically)?
It appears that Peter Birren is the only one who did.
And yeah, I've read Peter's stuff and corresponded with him. I got turned onto the closed bridle way of doing things by him. His system takes care of some vulnerabilities inherent in our opening bridles but you gotta reach for the lanyard and I can make a pretty good case that in the real world my system is safer. We've both perfected things as good as they're gonna get in our respective fields and we're not gonna learn anything more from each other.
By the way - I don't do speculation and convictions. I do accident reports and physics. If you have evidence to the contrary please cite it.
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Flying Lobster
- Posts: 1042
- Joined: Fri Feb 25, 2005 4:17 pm
Tad--you have in fact made many erroneous statements concerning accidents--mostly to back up your convictions of the faulty nature of towing. The simple fact is that hundreds of thousands of tows using weaklinks in their present configuration successfully bely your contentions that we're all crazy for towing that way.
Simply put, your statements are irresponsible and are based on your personal interpretations.
I am a tow operator--as well as a "towee." I also do aerotow tandems. Using greenline or similar line, which generally tests at 125 lbs +- 50 lbs is widely accepted because it simply works well and relatively predicatably for the enormous range of conditions and applications in towing. If this weren't true, then accident rates would be much higher and these kinds of weaklinks would have been abandoned along time ago.
A 400lb load limit for a solo tow is absurd. You claim in-depth knoweldge of what you're doing--but do you know what kind of stitching your using, what kind of tack, and how it affects the integrity of the join you're doing?
Last year's jihad was against releases--now you're going after weaklinks.
Everyone supports you making efforts to improve things--but in the process you trash the present methods as somehow being an accident waiting to happen. You might not actually say it--but the implication is that both the operators and towed pilots are being irresponsible for using faulty equipment and practices.
Do pilots need to constantly review their tow systems? yes. Do weaklinks--being the weakest link in the system, after all--need to be carefully inspected and frequently changed? yes. Do we need to constantly try to improve things? yes. Do we need to scare the daylights out of pilots with doomsday scenarios and suggest punative action for using widely accepted practices before something better comes along? Definitely not.
My apologies to the list for waking this sleeping giant.
marc
Simply put, your statements are irresponsible and are based on your personal interpretations.
I am a tow operator--as well as a "towee." I also do aerotow tandems. Using greenline or similar line, which generally tests at 125 lbs +- 50 lbs is widely accepted because it simply works well and relatively predicatably for the enormous range of conditions and applications in towing. If this weren't true, then accident rates would be much higher and these kinds of weaklinks would have been abandoned along time ago.
A 400lb load limit for a solo tow is absurd. You claim in-depth knoweldge of what you're doing--but do you know what kind of stitching your using, what kind of tack, and how it affects the integrity of the join you're doing?
Last year's jihad was against releases--now you're going after weaklinks.
Everyone supports you making efforts to improve things--but in the process you trash the present methods as somehow being an accident waiting to happen. You might not actually say it--but the implication is that both the operators and towed pilots are being irresponsible for using faulty equipment and practices.
Do pilots need to constantly review their tow systems? yes. Do weaklinks--being the weakest link in the system, after all--need to be carefully inspected and frequently changed? yes. Do we need to constantly try to improve things? yes. Do we need to scare the daylights out of pilots with doomsday scenarios and suggest punative action for using widely accepted practices before something better comes along? Definitely not.
My apologies to the list for waking this sleeping giant.
marc
Great Googly-moo!
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Tad Eareckson
- Posts: 304
- Joined: Wed Feb 09, 2005 8:50 am
Marc, let's take the weak link you described - 125 +/-50 - and put it on the end of a one point bridle. Its top end is 175 which doesn't happen until the tow line hits twice that which is 350. That makes it a (350/300=) 1.17 G weak link.
I'm talking about a 400 pound weak link THAT GOES ON THE END OF THE TOW LINE where it benefits from no force split and is thus a (400/300=) 1.33 G weak link.
So you and I are talking about a tow line tension difference of fifty pounds or a third of a G.
And I'm still 200 pounds or two thirds of a G below the limit specified by USHGA and the FAA. (If you've got a problem with that figure take it up with your Regional Director - not me.)
Let's look at the bottom end - same glider, same bridle. 75 times two is 150 pounds which is half a G and .30 below what the FAA says is safe to tow a glider under their jurisdiction. And it gets worse if you put it on the end of a two point bridle.
I see you still haven't bothered to look at my documentation which answers the questions about my weak links but they don't deviate more than 21 percent up or down. You seem to be quite content with a tolerance of 39 percent. (I also note that you continue to be content to throw out broad accusations without citing any evidence.)
If hundreds of thousands of tows have been completed successfully then tens of thousands of attempts haven't.
Here's some stuff off the wire from the local crowd (none of which coursed from my pen)...
***
-
NEVER TRUST A WEAK LINK!
Expect two things from your weak link:
(1) It will break unexpectedly at the most inopportune time, with no warning adn no indicaiton of a flight problem.
(2) It will hold strong and fast whenever you move into a lockout.
-
Then I switched to the falcon and the birds were singing in tune again. Until the brand new weak link vaporized at about 1000 feet for no apparent reason.
-
At 840 feet I noticed the tug was high and rising so I pushed out a bit to catch up. Broke the weaklink and stalled since I was so nose-high.
-
First try was a notably short flight, with a weak link break moments after lifting from the launch cart. The wind had shifted, so I had a down-wind landing, rolling in. I succeeded in dragging a knee instead of a toe on one side, so I earned a nice strawberry scrape.
-
I got five launches with three full flights on the US. Two weak link breaks. Both were non-issues.
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Got to Ridgley after 12, late as usual and was one of the last to launch. Broke a weak link. From now on I use a new weak link every time since they're giving us dental floss now.
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Kristen attached me to the plane and I rose briefly in the air. Pop! My weak link broke. (...The bad part is that sometimes the links just break, for no particular reason.)
-
Just a quick story with good educational value for other tow pilots. Yesterday I was the second of 3 off cart weak link breaks behind a 914 tug. Turbo was kicking in too quick says Bo.
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I bent one this year when I had a weak link break right off the cart...
-
I had a weak link break at maybe 50 feet. I thought I was going to have to land in the soybeans -- the very tall soybeans -- when I looked at my angle. But, my glider stalled quite dramatically almost instantly (hard not to stall when you have a break), and dove towards the ground (a bit disconcerting from so low).
-
...I hit enough turbulence to break my weak link. #%*&!
-
Steve had a weak link break on his first launch just after leaving the cart and rode it in on the asphault.
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A second later, we are horrified to see her weak link has broken. We know she has been well prepared, but we want her first flight to be perfect.
-
...but at 400 feet my pussy-##s weak link broke.
-
I had a late start due to a weak link break.
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Being a "large and tall" pilot (6' and 225lbs) on a big glider, I don't get pushed around as much by thermals...but then again, I'm pushing the weak link that much closer to it's breaking point (since everyone tends to use the same test-strength line for the link).
-
I've only had one weak link break while aerotowing and it happened while I was still very low and over the runway. I was happy that I automatically pulled in as soon as I heard the snap and got slow.
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One of the more interesting and poinient ones is the smooth air break. Towing up in smooth air, in position and you have a good weaklink... just towing along straight and level, nice and smooth... when the weaklink breaks. There's no appearent reason. No rough air, no rough glider inputs... it just breaks.
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Broke the weak link at 100' this time. The tow was a little rowdy, but not that bad. Don't know what caused the break.
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This time the link broke at 900'. Damn.
-
Broke the weak link at 1000'. And it was a fairly mellow tow.
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I was in line early but had a green tow pilot. My weak link broke after an extremely fast 350 feet.
-
Anyway, on my first tow, Tex entered a thermal at just over 1100 AGL, and I failed to track properly behind him. I got turned away from him (not badly) and as I was about to get back into position the weak link broke at 1200 AGL.
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I could feel a huge gust hit right as I came off the cart. Uh oh. I was right behind the tug at maybe 100 feet when my link broke. (Kev said yesterday the weak link might have also broken because of the very powerful tug, which throttled back yesterday.)
-
My weak link broke for no obvious reason at ~2,000' as Zack was pulling me in a wide turn to get back into a thermal he had found earlier.
-
***
And, somehow, after all these years, I've never heard anyone say, "Thank gawd my weak link broke! My crossbar was about to go!"
We're too close to and often off the bottom end on this crap. This stuff doesn't happen to sailplanes and they couldn't afford it. We've just accepted it 'cause we think that's the way it's gotta be.
This isn't about trying to make everyone think that he's gonna die 'cause his weak link popped at twenty feet. This is about trying to put the decision regarding termination of the tow in the hands of the pilot - where it belongs.
I'm talking about a 400 pound weak link THAT GOES ON THE END OF THE TOW LINE where it benefits from no force split and is thus a (400/300=) 1.33 G weak link.
So you and I are talking about a tow line tension difference of fifty pounds or a third of a G.
And I'm still 200 pounds or two thirds of a G below the limit specified by USHGA and the FAA. (If you've got a problem with that figure take it up with your Regional Director - not me.)
Let's look at the bottom end - same glider, same bridle. 75 times two is 150 pounds which is half a G and .30 below what the FAA says is safe to tow a glider under their jurisdiction. And it gets worse if you put it on the end of a two point bridle.
I see you still haven't bothered to look at my documentation which answers the questions about my weak links but they don't deviate more than 21 percent up or down. You seem to be quite content with a tolerance of 39 percent. (I also note that you continue to be content to throw out broad accusations without citing any evidence.)
If hundreds of thousands of tows have been completed successfully then tens of thousands of attempts haven't.
Here's some stuff off the wire from the local crowd (none of which coursed from my pen)...
***
-
NEVER TRUST A WEAK LINK!
Expect two things from your weak link:
(1) It will break unexpectedly at the most inopportune time, with no warning adn no indicaiton of a flight problem.
(2) It will hold strong and fast whenever you move into a lockout.
-
Then I switched to the falcon and the birds were singing in tune again. Until the brand new weak link vaporized at about 1000 feet for no apparent reason.
-
At 840 feet I noticed the tug was high and rising so I pushed out a bit to catch up. Broke the weaklink and stalled since I was so nose-high.
-
First try was a notably short flight, with a weak link break moments after lifting from the launch cart. The wind had shifted, so I had a down-wind landing, rolling in. I succeeded in dragging a knee instead of a toe on one side, so I earned a nice strawberry scrape.
-
I got five launches with three full flights on the US. Two weak link breaks. Both were non-issues.
-
Got to Ridgley after 12, late as usual and was one of the last to launch. Broke a weak link. From now on I use a new weak link every time since they're giving us dental floss now.
-
Kristen attached me to the plane and I rose briefly in the air. Pop! My weak link broke. (...The bad part is that sometimes the links just break, for no particular reason.)
-
Just a quick story with good educational value for other tow pilots. Yesterday I was the second of 3 off cart weak link breaks behind a 914 tug. Turbo was kicking in too quick says Bo.
-
I bent one this year when I had a weak link break right off the cart...
-
I had a weak link break at maybe 50 feet. I thought I was going to have to land in the soybeans -- the very tall soybeans -- when I looked at my angle. But, my glider stalled quite dramatically almost instantly (hard not to stall when you have a break), and dove towards the ground (a bit disconcerting from so low).
-
...I hit enough turbulence to break my weak link. #%*&!
-
Steve had a weak link break on his first launch just after leaving the cart and rode it in on the asphault.
-
A second later, we are horrified to see her weak link has broken. We know she has been well prepared, but we want her first flight to be perfect.
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...but at 400 feet my pussy-##s weak link broke.
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I had a late start due to a weak link break.
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Being a "large and tall" pilot (6' and 225lbs) on a big glider, I don't get pushed around as much by thermals...but then again, I'm pushing the weak link that much closer to it's breaking point (since everyone tends to use the same test-strength line for the link).
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I've only had one weak link break while aerotowing and it happened while I was still very low and over the runway. I was happy that I automatically pulled in as soon as I heard the snap and got slow.
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One of the more interesting and poinient ones is the smooth air break. Towing up in smooth air, in position and you have a good weaklink... just towing along straight and level, nice and smooth... when the weaklink breaks. There's no appearent reason. No rough air, no rough glider inputs... it just breaks.
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Broke the weak link at 100' this time. The tow was a little rowdy, but not that bad. Don't know what caused the break.
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This time the link broke at 900'. Damn.
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Broke the weak link at 1000'. And it was a fairly mellow tow.
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I was in line early but had a green tow pilot. My weak link broke after an extremely fast 350 feet.
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Anyway, on my first tow, Tex entered a thermal at just over 1100 AGL, and I failed to track properly behind him. I got turned away from him (not badly) and as I was about to get back into position the weak link broke at 1200 AGL.
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I could feel a huge gust hit right as I came off the cart. Uh oh. I was right behind the tug at maybe 100 feet when my link broke. (Kev said yesterday the weak link might have also broken because of the very powerful tug, which throttled back yesterday.)
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My weak link broke for no obvious reason at ~2,000' as Zack was pulling me in a wide turn to get back into a thermal he had found earlier.
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***
And, somehow, after all these years, I've never heard anyone say, "Thank gawd my weak link broke! My crossbar was about to go!"
We're too close to and often off the bottom end on this crap. This stuff doesn't happen to sailplanes and they couldn't afford it. We've just accepted it 'cause we think that's the way it's gotta be.
This isn't about trying to make everyone think that he's gonna die 'cause his weak link popped at twenty feet. This is about trying to put the decision regarding termination of the tow in the hands of the pilot - where it belongs.
One thing in all of these quips that you cut/paste from our posts that you haven't mentioned is that not all of these weaklink breaks are from brand new weaklinks. A couple of those posts were mine and I don't tie a new weaklink every time I fly. Usually I go 10 or more tows before I decide to retye it or it breaks and I have to anyway. I always check my weaklink visually, but if it breaks, I pull in and make my decision on where to land. If you are getting into a lockout and blaming it on a weaklink, than your decision ability is flawed in the first place. If you get out of position on tow, it should be the pilots decision to use his release and go around for a second time than blame a lockout on the weaklink NOT breaking.
I agree with Marc (scary!) Last year we listened to rant after rant about the releases. Are we going to have to revisit this new topic each week until that vein in someones head begins to pulse rapidly and they decide to beat you silly with a broken downtube?
In all seriousness, we all care about safety ... and none of us will beat you with a downtube, but we will all fantasize about it if you keep this up!
I agree with Marc (scary!) Last year we listened to rant after rant about the releases. Are we going to have to revisit this new topic each week until that vein in someones head begins to pulse rapidly and they decide to beat you silly with a broken downtube?
In all seriousness, we all care about safety ... and none of us will beat you with a downtube, but we will all fantasize about it if you keep this up!
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Tad Eareckson
- Posts: 304
- Joined: Wed Feb 09, 2005 8:50 am
When I make the decision to sacrifice a day and pump into the atmosphere the CO2 it takes to get to the bridge and beyond, I don't want to stand around cooking in my harness while the soaring window evaporates - even on the rare occasions when there's more than one tug running - 'cause people with unreliable weak links get connected to the tow line in front front of me - and then go back in line in front of me with my lift ticket subsidizing the expenses.
I've been to Ridgely twice this season and have twice been subjected to same already from gliders within a couple of positions of my place. Both times the pilots were using antique weak links which had been near or off the bottom end of the scale even on their first flights.
Someone with a weak link below a .8 G capacity on the end of his bridle is not prepared to fly. I don't even want him near the tow line while I'm stuffing battens if he's affected the length the line will be by the time I cross the taxiway.
Selfishly - I wouldn't even want him paying Highland for the extra tows 'cause I want him up there marking thermals for me. (I need all the help I can get - all the sailplanes are gone and the vultures have been absolutely negligent so far this year.)
Chris, neither you nor anybody else is forced to read anything with my name on it - you don't even have to delete it from your mailbox anymore. But the only time your decision to fly with a questionable weak link (and all of them are questionable now) doesn't have a negative effect on everyone else is when it pops and you claw your way up anyway.
The last two sentences of your first paragraph are a reiteration of what I and the author of the link referenced by Danny have been saying.
Marc's statement about the reliability of Greenspot weak links is nonsense.
The bottom end of a Falcon 140 is less than half of a Talon 150. And they and everything in between get the same string?
Weak link ratings are not selected as a function of the range of conditions. They exist solely to protect the airframe. As you said Chris, they do and can not ensure your control or protect you from a lockout.
You're not going to be seeing much of an effect in terms of accident rates as a result of shoddy weak links. You will see a higher per day rate of landings and takeoffs. We see them.
The statement that things are just great 'cause if they weren't we'd have done something better is like saying that the water couldn't possibly be hot 'cause all those frogs would've jumped out by now if it were.
I was, by the way, well aware of the fact that you and lotsa people don't bother changing their weak links when they should but that's irrelevant 'cause -
A. That happens to be the temperature of the water; and
B. We all know from personal experience (yours truly included) that you can have a brand new loop of Greenspot break straight and level fifty feet up in glassy air for no reason whatsoever.
There just aren't any AT weak link breaks in situations in which our six G airframes are being threatened. A weak link goes 'cause a tug is climbing too fast? Was a cross spar about to blow? And Lauren doesn't even weigh anything. This is bullshit.
Here's what I'm proposing - and I've shifted to another flavor implementation since starting this thread.
You find out how much you and your stuff weighs. If need be you step on the bathroom scales out at the flight line.
When you get your preflight check you say "250 pounds."
The launch person hands you a Gray/Blue 360 pound shear link with a tow ring incorporated in its aft eye which puts you at right about the middle (1.44) of the FAA's .8-2.0 G range and everybody's ass is covered.
You can see what one of these things looks like at:
http://www.flickr.com/photos/aerotowrelease/
As for me, 310 pounds, I'm gonna sign the waiver and use 600 pound/2 G shear link with an error could spill me a hundred pounds into the red zone 'cause I'm not worried about my glider breaking up. (Actually, that probably won't happen 'cause the Dragonfly tail may be a limiting factor.)
You run your bridle through the tow ring and connect the bridle to your release.
You get to launch and the launch person unclips the previous shear link from the carabiner and replaces it with you.
This weak link will only fail when you want it to which, as you pointed out, Chris, will only be well into a lockout and long after you should have tested the functionality of your release.
If it does fail, which should happen at a frequency less than that at which your parachute is deployed, you are requested to secure the back half of the shear link before releasing and stowing your two point bridle.
So, Chris, if you're absolutely positive that there is no room for or possibility of any improvement in these systems, just click on by. Otherwise, critique what I'm saying.
I really do appreciate efforts to correct me when I've made an error like the Holly/tow line thing. (I'm still waiting for Marc to provide a single quotation supporting his accusations.)
I've been to Ridgely twice this season and have twice been subjected to same already from gliders within a couple of positions of my place. Both times the pilots were using antique weak links which had been near or off the bottom end of the scale even on their first flights.
Someone with a weak link below a .8 G capacity on the end of his bridle is not prepared to fly. I don't even want him near the tow line while I'm stuffing battens if he's affected the length the line will be by the time I cross the taxiway.
Selfishly - I wouldn't even want him paying Highland for the extra tows 'cause I want him up there marking thermals for me. (I need all the help I can get - all the sailplanes are gone and the vultures have been absolutely negligent so far this year.)
Chris, neither you nor anybody else is forced to read anything with my name on it - you don't even have to delete it from your mailbox anymore. But the only time your decision to fly with a questionable weak link (and all of them are questionable now) doesn't have a negative effect on everyone else is when it pops and you claw your way up anyway.
The last two sentences of your first paragraph are a reiteration of what I and the author of the link referenced by Danny have been saying.
Marc's statement about the reliability of Greenspot weak links is nonsense.
The bottom end of a Falcon 140 is less than half of a Talon 150. And they and everything in between get the same string?
Weak link ratings are not selected as a function of the range of conditions. They exist solely to protect the airframe. As you said Chris, they do and can not ensure your control or protect you from a lockout.
You're not going to be seeing much of an effect in terms of accident rates as a result of shoddy weak links. You will see a higher per day rate of landings and takeoffs. We see them.
The statement that things are just great 'cause if they weren't we'd have done something better is like saying that the water couldn't possibly be hot 'cause all those frogs would've jumped out by now if it were.
I was, by the way, well aware of the fact that you and lotsa people don't bother changing their weak links when they should but that's irrelevant 'cause -
A. That happens to be the temperature of the water; and
B. We all know from personal experience (yours truly included) that you can have a brand new loop of Greenspot break straight and level fifty feet up in glassy air for no reason whatsoever.
There just aren't any AT weak link breaks in situations in which our six G airframes are being threatened. A weak link goes 'cause a tug is climbing too fast? Was a cross spar about to blow? And Lauren doesn't even weigh anything. This is bullshit.
Here's what I'm proposing - and I've shifted to another flavor implementation since starting this thread.
You find out how much you and your stuff weighs. If need be you step on the bathroom scales out at the flight line.
When you get your preflight check you say "250 pounds."
The launch person hands you a Gray/Blue 360 pound shear link with a tow ring incorporated in its aft eye which puts you at right about the middle (1.44) of the FAA's .8-2.0 G range and everybody's ass is covered.
You can see what one of these things looks like at:
http://www.flickr.com/photos/aerotowrelease/
As for me, 310 pounds, I'm gonna sign the waiver and use 600 pound/2 G shear link with an error could spill me a hundred pounds into the red zone 'cause I'm not worried about my glider breaking up. (Actually, that probably won't happen 'cause the Dragonfly tail may be a limiting factor.)
You run your bridle through the tow ring and connect the bridle to your release.
You get to launch and the launch person unclips the previous shear link from the carabiner and replaces it with you.
This weak link will only fail when you want it to which, as you pointed out, Chris, will only be well into a lockout and long after you should have tested the functionality of your release.
If it does fail, which should happen at a frequency less than that at which your parachute is deployed, you are requested to secure the back half of the shear link before releasing and stowing your two point bridle.
So, Chris, if you're absolutely positive that there is no room for or possibility of any improvement in these systems, just click on by. Otherwise, critique what I'm saying.
I really do appreciate efforts to correct me when I've made an error like the Holly/tow line thing. (I'm still waiting for Marc to provide a single quotation supporting his accusations.)
>"Got bored towards the end of last season and started doing a lot of
> archive searches along the lines of "weak link broke" with respect
> aerotowing to see if any of the little bits of string served any function
> more useful than do the sacred back up suspension straps and hook
> knives. "
Gee, Tad, I've used my hook knife and been glad I had it.
Don't feel qualified to comment on weak links. What follows is pure gut opinion and therefore not subject to argument. Have to admit I don't know of a case where someone was clearly saved by one. I popped 5 in a row once while trying to learn how to tow a K2. Really don't know whether the breaks saved me or not, but clearly I wasn't handling it smoothly and could have been getting myself in trouble. Whether or not it's true I always feel comforted by the thought that something is designed to pop before the forces get too large, and feel better with something weaker rather than stronger. Pure untested psychology.
I think you'd want them breaking every now and then just so you know they CAN break. Is 1 break every 50 tows an acceptable number? I think right now we're hitting about 1 in 20.
> archive searches along the lines of "weak link broke" with respect
> aerotowing to see if any of the little bits of string served any function
> more useful than do the sacred back up suspension straps and hook
> knives. "
Gee, Tad, I've used my hook knife and been glad I had it.
Don't feel qualified to comment on weak links. What follows is pure gut opinion and therefore not subject to argument. Have to admit I don't know of a case where someone was clearly saved by one. I popped 5 in a row once while trying to learn how to tow a K2. Really don't know whether the breaks saved me or not, but clearly I wasn't handling it smoothly and could have been getting myself in trouble. Whether or not it's true I always feel comforted by the thought that something is designed to pop before the forces get too large, and feel better with something weaker rather than stronger. Pure untested psychology.
I think you'd want them breaking every now and then just so you know they CAN break. Is 1 break every 50 tows an acceptable number? I think right now we're hitting about 1 in 20.
Brian Vant-Hull
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Tad Eareckson
- Posts: 304
- Joined: Wed Feb 09, 2005 8:50 am
Hi Brian,
I didn't state that very well. I do still have a hook knife available above my parachute container but, since I'm never flying near bodies of water more formidable than the upper reaches of the Choptank and Tuckahoe I find myself asking myself why with increasing frequency lately. Could come in handy in a tree but that ain't likely flying from Ridgely either - even for me.
If I ever heard of your hook knife incident I've forgotten - unless it involved falling out of a tree at High Rock. Can you fill me in?
If you used your hook knife as a means of leaving a tow line behind please REALLY fill me in 'cause my contention is that the only way that can happen is if your release and bridle system REALLY sucks to begin with.
There are a set of USHGA AT Guidelines which REQUIRE you to have a hook knife but RECOMMEND that you have a secondary release. Major priorities crisis.
A little aside - I don't think you can learn to tow a K2.
Here's the deal about weak links. I don't think you get it. Don't feel bad. I JUST got it within the past few weeks - months after reading a post on the towing list from somebody who gets it. The guy on the link Danny cited gets it.
THE WEAK LINK IS NOT THERE TO SAVE ANYONE. THE WEAK LINK IS ONLY THERE TO SAVE THE PLANE.
The RELEASE is there to save you (and I commend you for being a member of the minority of pilots who appreciate the importance of having a hand on the actuator at all times).
You only need to have the weak link go a bit before the cross spar (I'm ignoring the tug for the purpose of this discussion). We've never been anywhere close to that.
Even a flimsy weak link at the bottom end of the acceptable range (.8 Gs) can hold enough to put and keep you in a lockout. In a lockout you - by definition - have NO control of the glider. The only way to regain enough control to live, if you're anywhere near the ground, is to release.
The weak link might go soon enough to let you live, or it might not go until after you're dead. You can't afford to wait and find out.
Your confidence must be in your abilities to make a correct and fast decision to release and physically implement it. Steve and I can handle the latter requirement by relaxing our jaw muscles.
We're asking the weak link to function as an emergency release to save the pilot. It cannot do that. We've dumbed them down so much that if you get waked by a migrating Monarch you're blown off tow.
I've been doing some testing lately and it's looking like the maximum tension the tow line/weak link/glider normally experiences happens while Bob is running next to you saying, "Have a good flight!" And I've got an educated guess that says that the standard weak link experiences some degradation during this acceleration and in the course of the flight - even before it gets chewed up by the notch on the end of the spinnaker shackle gate.
In the weak link I've developed the critical element is isolated and protected and, in theory, will not degrade and will last forever. It either survives unscathed or it explodes at pretty close to the point you ask it to.
We don't want them breaking at a rate of 1:20 or 1:50. We want them to break at the rate sailplane weak links break - never. If we can't control the glider we should have released long before they break. (I'm gonna use your one in twenty guesstimate until somebody comes along with something better.)
If we want to be sure they break we don't want to test them in the air. We want to verify that on the kitchen table using the 776 pound capacity tester I built last winter. But I've done that already on a range from zilch up to 636 pounds. They work.
I didn't state that very well. I do still have a hook knife available above my parachute container but, since I'm never flying near bodies of water more formidable than the upper reaches of the Choptank and Tuckahoe I find myself asking myself why with increasing frequency lately. Could come in handy in a tree but that ain't likely flying from Ridgely either - even for me.
If I ever heard of your hook knife incident I've forgotten - unless it involved falling out of a tree at High Rock. Can you fill me in?
If you used your hook knife as a means of leaving a tow line behind please REALLY fill me in 'cause my contention is that the only way that can happen is if your release and bridle system REALLY sucks to begin with.
There are a set of USHGA AT Guidelines which REQUIRE you to have a hook knife but RECOMMEND that you have a secondary release. Major priorities crisis.
A little aside - I don't think you can learn to tow a K2.
Here's the deal about weak links. I don't think you get it. Don't feel bad. I JUST got it within the past few weeks - months after reading a post on the towing list from somebody who gets it. The guy on the link Danny cited gets it.
THE WEAK LINK IS NOT THERE TO SAVE ANYONE. THE WEAK LINK IS ONLY THERE TO SAVE THE PLANE.
The RELEASE is there to save you (and I commend you for being a member of the minority of pilots who appreciate the importance of having a hand on the actuator at all times).
You only need to have the weak link go a bit before the cross spar (I'm ignoring the tug for the purpose of this discussion). We've never been anywhere close to that.
Even a flimsy weak link at the bottom end of the acceptable range (.8 Gs) can hold enough to put and keep you in a lockout. In a lockout you - by definition - have NO control of the glider. The only way to regain enough control to live, if you're anywhere near the ground, is to release.
The weak link might go soon enough to let you live, or it might not go until after you're dead. You can't afford to wait and find out.
Your confidence must be in your abilities to make a correct and fast decision to release and physically implement it. Steve and I can handle the latter requirement by relaxing our jaw muscles.
We're asking the weak link to function as an emergency release to save the pilot. It cannot do that. We've dumbed them down so much that if you get waked by a migrating Monarch you're blown off tow.
I've been doing some testing lately and it's looking like the maximum tension the tow line/weak link/glider normally experiences happens while Bob is running next to you saying, "Have a good flight!" And I've got an educated guess that says that the standard weak link experiences some degradation during this acceleration and in the course of the flight - even before it gets chewed up by the notch on the end of the spinnaker shackle gate.
In the weak link I've developed the critical element is isolated and protected and, in theory, will not degrade and will last forever. It either survives unscathed or it explodes at pretty close to the point you ask it to.
We don't want them breaking at a rate of 1:20 or 1:50. We want them to break at the rate sailplane weak links break - never. If we can't control the glider we should have released long before they break. (I'm gonna use your one in twenty guesstimate until somebody comes along with something better.)
If we want to be sure they break we don't want to test them in the air. We want to verify that on the kitchen table using the 776 pound capacity tester I built last winter. But I've done that already on a range from zilch up to 636 pounds. They work.
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Flying Lobster
- Posts: 1042
- Joined: Fri Feb 25, 2005 4:17 pm
If the maximum force truly is largest right when the tug starts to pull you (and this seems eminently reasonable during a normal flight), and a lockout never approaches this force (don't know if this is true), then your contention that our weak links are entirely too weak rings true.
How have you been testing the forces? Could you (hehe) do us a favor and test it during a lockout?
I used my hook knife to get free of the glider while in the tree at HR.
I really like the idea of a mouth actuated release for the first 30 seconds of tow...been too lazy to put it into practice.
How have you been testing the forces? Could you (hehe) do us a favor and test it during a lockout?
I used my hook knife to get free of the glider while in the tree at HR.
I really like the idea of a mouth actuated release for the first 30 seconds of tow...been too lazy to put it into practice.
Brian Vant-Hull
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Flying Lobster
- Posts: 1042
- Joined: Fri Feb 25, 2005 4:17 pm
Ain't no device going to mitigate the fact towing in turbulence is riskier and takes more piloting skill. Changing your breaking pressures is only going to shift the bar on the decision set that the pilot must make in those split seconds during initial tow. Tad is correct in one statement--the weaklink does protect the plane, especially during roll-out and liftoff. Upping the load limit means more trust will be placed in the towed pilot in doing the right thing. keeping the line under higher pressure at initial lift-off, IMO, will increase the probability of lock-outs over the broad range of pilots and conditions, while increasing the risk to the tug as well.
When Tad succeeds in convincing one single very experienced commercial aerotow tug pilot that his system is better and safer, then I'll start taking his ideas seriously. Tow operators are the ones who really have it on the line, so to speak, and if and when a better idea comes along they will adapt if it improves the safety or efficiency of their operations. Untill then, your still a test pilot.
marc
When Tad succeeds in convincing one single very experienced commercial aerotow tug pilot that his system is better and safer, then I'll start taking his ideas seriously. Tow operators are the ones who really have it on the line, so to speak, and if and when a better idea comes along they will adapt if it improves the safety or efficiency of their operations. Untill then, your still a test pilot.
marc
Great Googly-moo!
risk management
People who calculate risks and returns often use a quantitative technique. They multiply the expected probablility of an event times the "value" of it's consequence. The premise is that if the consequence is relative modest you can tolerate a realitively higher probability. In our sport unfortunately the consequences can be extreme, therefore it is prudent to lower the probability of a serious consequencal event as much as possible. While I am sure it has happened I have yet to see a serious outcome from a premature weakling break. On the other hand a weak link that doesn't function when it should can amd oftem has led to a catastrophic result. It seems that the lesson is to err conservatively, better to break too early than too late.
Last year Tad carefully looked over my harness while sitting under the canopy with nothing else to do. he found a significantly frayed line that could have resulted in a serious accident for me. I was at first reluctant to listen to him since he always seems to be such an alarmist, but upon inspection confirmed that he was right. I took two lessons away that day, one preflight your harness as well as your glider, and two don't discount someone's observations based upon your own preconceived notions.
Dan T
Last year Tad carefully looked over my harness while sitting under the canopy with nothing else to do. he found a significantly frayed line that could have resulted in a serious accident for me. I was at first reluctant to listen to him since he always seems to be such an alarmist, but upon inspection confirmed that he was right. I took two lessons away that day, one preflight your harness as well as your glider, and two don't discount someone's observations based upon your own preconceived notions.
Dan T
links
A funny thing occured to me while flying this weekend......
I can't recall a weak link breaking on launch or climb-out
in the mountains......
Flying both affords me the chance to relax my brain......LOL
Hope to see ya'll soon
'Til then, mike
I can't recall a weak link breaking on launch or climb-out
in the mountains......
Flying both affords me the chance to relax my brain......LOL
Hope to see ya'll soon
'Til then, mike
Mike Lee
How 'Bout That
How 'Bout That
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Tad Eareckson
- Posts: 304
- Joined: Wed Feb 09, 2005 8:50 am
Marc,
Thank you for contributing something halfway responsible to the conversation - for a change. It would be nice if you acknowledged a few things with respect to your previous posts which you made without bothering to read and/or take the time to understand what was being discussed but I'll take what I can get.
However...
First off, since USHGA specifies an upper - 2.0 Gs - but, for some bizarre reason, not a lower weak link limit, can we agree that at some point there is a safety compromise by using and excessively feeble weak link?
Yes? Good.
Now, can we determine a value for that lower limit? The FAA sez 0.8. Any objections to that figure? No? Good. Zero point eight it is.
OK Marc, listen good. THE WEAK LINK ABSOLUTELY DOES NOT PROTECT THE GLIDER AT ROLLOUT AND LIFTOFF. That's the one point of the flight at which it is the least part of the safety equation. IT ABSOLUTELY DOES NOT PREVENT A LOCKOUT. It can limit the extent of a lockout up high but down low you're in deep shit unless you're climbing.
No weak link can enhance your control of the glider in turbulence. You will be totally out of control, i.e., LOCKED OUT, before its strength becomes a factor.
The weak link keeps the glider from breaking up in the air. It may accidentally function to prevent the glider from slamming into the ground but provides no guarantee. If you start trying to ask it to perform a dual function you compromise its ability to get you SAFELY clear of the ground and up high enough to stand a reasonable chance of finding lift.
Like James Freeman said - "None of this is rocket science. It is basic physics combined with elementary mechanics."
There are only two things you've gotta consider with respect to a weak link - what strength and where to put it.
If you listen to PETER BIRREN (http://www.birrendesign.com/LKAero.html) (Marc) or me, you put the weak link BETWEEN THE TOW LINE AND THE BRIDLE. That way you don't have to worry about the bridle wrapping at the tow ring (carabiner) if the weak link fails. He suggests a quadruple loop of 130 pound Greenspot which, assuming a quadruple loop is twice as strong as a double loop of the stuff I tested, translates to FOUR HUNDRED AND FOUR POUNDS (Marc).
I interpret your second paragraph to mean that you will never, under any circumstances, review the data and attempt to understand the science yourself? You'll just follow the lead of someone with enough brains to do it for you? Fine. I'd just prefer not to hear anymore about equipment that passes muster when your definition of that is just a matter of what most of the rest of the sheep are doing.
Dan,
Thanks for crediting me with the catch but I think the most I saved you from was some awkwardness and discomfort. The stuff that kept you connected to the glider was OK.
Brian,
Thanks very much for the positive contribution to the discussion. Nice to be talking to someone for whom physics is not a totally alien and irrelevant concept. I knew there was intelligent life out there somewhere. Eternal gratitude for taking the first step in rescuing the conversation from the gutter to which, I feared, the Usual Suspects would once again manage to drag and leave it.
Last fall I developed a device based on the strength per stitch principle in which there are graduated sequences of stitches. You install it between the tow line and the glider. When the tug rolls sequences fail up to the holding point and the pilot can see (thanks, Sunny, for the idea of putting it on the proper end of the tow line) what is or isn't happening when. The gauge goes back down with the tug where it is retrieved and examined.
Only have a few tests to date but I myself went up behind it on my last outing and got something with which I'm pretty happy (dolly tires properly inflated, conditions and glider weight and configuration (full VG) recorded). Max load of about 160-175 pounds occurred at launch and was not exceeded in flight.
Recently I adapted a hydraulic cylinder and one and two point bridle/release configurations so's you can get constant readings in flight. (Hint: If you try this at home don't stare at the gauge too long or you'll have a real hard time finding the tug when you finally look up.)
With the 914's turbocharger kicked in (like they do for tandem) I got about 155 pounds. I'm calling the normal solo power setting 125 but I had trouble holding steady early in the flight and will need to go back up to get something with which I am really satisfied. A little pitch input translates to a lot of needle swing.
I'm guessing, at this point, that the in flight tension is only a function of engined setting, i.e., solo and tandem will be the same but the latter will be going up slower.
If you want more extensive info on the gauges lemme know and I can send you a PDF (149 K) (there's a schematic of the max tension recorder).
I once asked Sunny if they train students using induced lockouts but he pointed out that if you brought the bridle in contact with a nose wire and the top end wrapped you could have real serious structural problems real fast (oh, yeah).
However...
If you pop one of my links on the end of the tow line... I'd have absolutely no problem doing that at altitude and it could be a useful training tool.
We wouldn't be learning anything about tow tension though. As of a week ago we know about what steady state is, we know that the graph is going up as we roll away from the tug, and we know about where conventional weak links fail.
We could, however, experiment with different weak link strengths and get a subjective feel of the glider at failure.
I'm delighted to hear that you're interested in joining the Steve/Tad/Eastern Europe fraternity of folk who can release without doing anything.
Steve's three-strings are effective and free but the grommet/webbing interface needs work. My four strings are stronger and more versatile but are labor intensive and go out as part of a full secondary assembly (barrel release on the port side).
Take a look at the pitchurs -
http://www.flickr.com/photos/aerotowrelease/
and lemme know if you have further interest. I really like the confidence it gives me and I feel extremely bulletproof while I'm putting a safe distance between me and the grass.
Thank you for contributing something halfway responsible to the conversation - for a change. It would be nice if you acknowledged a few things with respect to your previous posts which you made without bothering to read and/or take the time to understand what was being discussed but I'll take what I can get.
However...
First off, since USHGA specifies an upper - 2.0 Gs - but, for some bizarre reason, not a lower weak link limit, can we agree that at some point there is a safety compromise by using and excessively feeble weak link?
Yes? Good.
Now, can we determine a value for that lower limit? The FAA sez 0.8. Any objections to that figure? No? Good. Zero point eight it is.
OK Marc, listen good. THE WEAK LINK ABSOLUTELY DOES NOT PROTECT THE GLIDER AT ROLLOUT AND LIFTOFF. That's the one point of the flight at which it is the least part of the safety equation. IT ABSOLUTELY DOES NOT PREVENT A LOCKOUT. It can limit the extent of a lockout up high but down low you're in deep shit unless you're climbing.
No weak link can enhance your control of the glider in turbulence. You will be totally out of control, i.e., LOCKED OUT, before its strength becomes a factor.
The weak link keeps the glider from breaking up in the air. It may accidentally function to prevent the glider from slamming into the ground but provides no guarantee. If you start trying to ask it to perform a dual function you compromise its ability to get you SAFELY clear of the ground and up high enough to stand a reasonable chance of finding lift.
Like James Freeman said - "None of this is rocket science. It is basic physics combined with elementary mechanics."
There are only two things you've gotta consider with respect to a weak link - what strength and where to put it.
If you listen to PETER BIRREN (http://www.birrendesign.com/LKAero.html) (Marc) or me, you put the weak link BETWEEN THE TOW LINE AND THE BRIDLE. That way you don't have to worry about the bridle wrapping at the tow ring (carabiner) if the weak link fails. He suggests a quadruple loop of 130 pound Greenspot which, assuming a quadruple loop is twice as strong as a double loop of the stuff I tested, translates to FOUR HUNDRED AND FOUR POUNDS (Marc).
I interpret your second paragraph to mean that you will never, under any circumstances, review the data and attempt to understand the science yourself? You'll just follow the lead of someone with enough brains to do it for you? Fine. I'd just prefer not to hear anymore about equipment that passes muster when your definition of that is just a matter of what most of the rest of the sheep are doing.
Dan,
Thanks for crediting me with the catch but I think the most I saved you from was some awkwardness and discomfort. The stuff that kept you connected to the glider was OK.
Brian,
Thanks very much for the positive contribution to the discussion. Nice to be talking to someone for whom physics is not a totally alien and irrelevant concept. I knew there was intelligent life out there somewhere. Eternal gratitude for taking the first step in rescuing the conversation from the gutter to which, I feared, the Usual Suspects would once again manage to drag and leave it.
Last fall I developed a device based on the strength per stitch principle in which there are graduated sequences of stitches. You install it between the tow line and the glider. When the tug rolls sequences fail up to the holding point and the pilot can see (thanks, Sunny, for the idea of putting it on the proper end of the tow line) what is or isn't happening when. The gauge goes back down with the tug where it is retrieved and examined.
Only have a few tests to date but I myself went up behind it on my last outing and got something with which I'm pretty happy (dolly tires properly inflated, conditions and glider weight and configuration (full VG) recorded). Max load of about 160-175 pounds occurred at launch and was not exceeded in flight.
Recently I adapted a hydraulic cylinder and one and two point bridle/release configurations so's you can get constant readings in flight. (Hint: If you try this at home don't stare at the gauge too long or you'll have a real hard time finding the tug when you finally look up.)
With the 914's turbocharger kicked in (like they do for tandem) I got about 155 pounds. I'm calling the normal solo power setting 125 but I had trouble holding steady early in the flight and will need to go back up to get something with which I am really satisfied. A little pitch input translates to a lot of needle swing.
I'm guessing, at this point, that the in flight tension is only a function of engined setting, i.e., solo and tandem will be the same but the latter will be going up slower.
If you want more extensive info on the gauges lemme know and I can send you a PDF (149 K) (there's a schematic of the max tension recorder).
I once asked Sunny if they train students using induced lockouts but he pointed out that if you brought the bridle in contact with a nose wire and the top end wrapped you could have real serious structural problems real fast (oh, yeah).
However...
If you pop one of my links on the end of the tow line... I'd have absolutely no problem doing that at altitude and it could be a useful training tool.
We wouldn't be learning anything about tow tension though. As of a week ago we know about what steady state is, we know that the graph is going up as we roll away from the tug, and we know about where conventional weak links fail.
We could, however, experiment with different weak link strengths and get a subjective feel of the glider at failure.
I'm delighted to hear that you're interested in joining the Steve/Tad/Eastern Europe fraternity of folk who can release without doing anything.
Steve's three-strings are effective and free but the grommet/webbing interface needs work. My four strings are stronger and more versatile but are labor intensive and go out as part of a full secondary assembly (barrel release on the port side).
Take a look at the pitchurs -
http://www.flickr.com/photos/aerotowrelease/
and lemme know if you have further interest. I really like the confidence it gives me and I feel extremely bulletproof while I'm putting a safe distance between me and the grass.
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Tad Eareckson
- Posts: 304
- Joined: Wed Feb 09, 2005 8:50 am
Gotta extract foot from mouth. Peter sez four strands - not loops. So a double loop of 130 at 200 pounds.
For me - 310 pounds - a "larger pilot" - a double loop of 150, extrapolates to 230 pounds. .74 Gs. Off the bottom end of what we all just agreed was the safe lower limit so I don't feel so bad.
I, for the purpose of this discussion, want to be smack dab in the middle of the safe range - 1.4 Gs so I do, in fact want 434 pounds which is between quadruple loops of 130 and 150.
Another correction - Shoulda read - less than half of the top end of a Talon 150.
For me - 310 pounds - a "larger pilot" - a double loop of 150, extrapolates to 230 pounds. .74 Gs. Off the bottom end of what we all just agreed was the safe lower limit so I don't feel so bad.
I, for the purpose of this discussion, want to be smack dab in the middle of the safe range - 1.4 Gs so I do, in fact want 434 pounds which is between quadruple loops of 130 and 150.
Another correction - Shoulda read - less than half of the top end of a Talon 150.
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Tad Eareckson
- Posts: 304
- Joined: Wed Feb 09, 2005 8:50 am
Here's part of a report from Joe in the 2004/09 issue of Hang Gliding.
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Highly experienced mountain pilot aerotowing a newly-purchased glider experienced a lockout at low altitude. Witness reports indicate that the glider began oscillating immediately after leaving the launch dolly. The weak link broke after the glider entered a lockout attitude. Once free, the glider was reportedly too low (50-65' AGL, estimated) to recover from the unusual attitude and impacted the ground in a steep dive. The pilot suffered fatal injuries due to blunt trauma. There is no evidence that the pilot made an attempt to release from tow prior to the weak link break, the gate was found closed on the Wallaby-style tow release...
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It's a real good bet that he was using a loop of the same understrength crap that "we" all swear by on the top end of his two point bridle. It didn't do anything to prevent or limit the extent of the lockout enough to keep him alive.
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Highly experienced mountain pilot aerotowing a newly-purchased glider experienced a lockout at low altitude. Witness reports indicate that the glider began oscillating immediately after leaving the launch dolly. The weak link broke after the glider entered a lockout attitude. Once free, the glider was reportedly too low (50-65' AGL, estimated) to recover from the unusual attitude and impacted the ground in a steep dive. The pilot suffered fatal injuries due to blunt trauma. There is no evidence that the pilot made an attempt to release from tow prior to the weak link break, the gate was found closed on the Wallaby-style tow release...
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It's a real good bet that he was using a loop of the same understrength crap that "we" all swear by on the top end of his two point bridle. It didn't do anything to prevent or limit the extent of the lockout enough to keep him alive.