Jonathan Slater - 2005/06/22 08:25:52 UTC
Cambridgeshire, England
Release under tension
I've only ever been towed up behind a vehicle, so I don't know if this applies generally to all forms of towing, but my instructors (very experienced people) are very much against releasing the tow line while under tension. Even with no tension the release should only take a brief tug, and there is no chance of upsetting the stability of the wing or of getting struck by a high speed release.
Jim Reich - 2005/06/22 15:00:00 UTC
Woodside Mountain, British Columbia
Vehicle towing - fixed line! DON'T DO IT!
I have experience behind ATVs using fixed tow lines and even experts can run into problems.
Payout or pay-in systems offer the ability to release tension rapidly when the pilot "fucks up" either by using too much brake or not staying on the tow line.
Pat Chewning - 2005/06/22 15:15:44 UTC
Portland, Oregon
I prefer to reduce the tension in the tow line and then release from tow. Placing a foot at the "Y" junction of the split tow harness (towmeup type) helps to release when there is no tension.
I once released under very high tension and the ends of the tow bridle smacked me in the face. So I really want the tension off when I release.
You might not always have that option.
Another benefit: You don't get as much pendulum motion if you are momentarily flying without tension and then release.
Paul van den Berg - 2005/06/22 15:52:59 UTC
Foot of the eastern Jura, Switzerland
I have done some seventy tows in the beginning of my flying career (when I lived in the flatlands). It can be a bit spooky, but then again, it is a comfortable and fast way to get up (the ride up to some mountain sites is much spookier and definitely much less comfortable! If only the flats produced the same thermals...)
I think you'll find people setting world records over the flats just fine.
I have done quite some step towing as well, I never felt unsafe with it but sometimes it seems it's not worth it (height gain not outweighing the extra time spent).
I have witnessed one case of a line jam on a step tow (pilot flying away and winch paying out). After the pilot almost made a somersault in the harness (frightening), the weak link gave and the glider continued with just a little surge.
So what was stopping him from releasing prior to the weak link blow?
If you step tow, have a good weak link and the winch man should be able to cut the line immediately.
Yes. Have a good weak link which will blow only when it senses that you would be in danger by staying on tow. Wanna say anything about the G rating?
How 'bout having a good release so you don't hafta wait/pray for your weak link to blow or your winch man to find and use the hook knife?
The last time I towed was more than seven years ago so some info might be outdated.
Nah, once somebody figures out a way to do something that results in a crash fewer than one flight out of five in these sports the technology and procedures tend to immediately grind to permanent halts.
Roger Wolff - 2005/06/23 07:41:11 UTC
the Netherlands
I am mostly alone in thinking (but convinced I'm right) that you cannot stall a wing by applying too much tow force.
It tends to be very lonely in these sports for people who have clues as to what they're talking about.
Here in Holland we have tow releases that will automatically unlock when the tow force becomes abnormally high, or not straight. I dislike them.
Check out Peter Birren's Pitch and Lockout Limiter sometime when you get a chance.
Like any safety system in towing (like a weak link) when it releases at the wrong point in time, you're screwed.
Getting people screwed as much as is humanly possible is most of what these sports are about. And the assholes who do it best are virtually always revered as gods.
The problem is that we live in a wet (low!) country. Large areas are not meadows because the Dutch dug canals every sixty meters or so. So the fields are often nine hundred by sixty meters. This means that we have a problem with crosswind.
With the proper technique it is still quite possible to launch and fly safely. However, the winch will be pulling at you at 45 degrees at one point in time. Those "safe" release systems will then unhook you when you're two or three meters above the ground flying crooked. Auch.
I once accidentally released under high tension (I was the passenger on a tandem ride). I still have the mark on my leg to prove it.
I've had a cable break at one meter from my tow release. That smacked me in my face. I lost the glass in my glasses on that one.
Beats having your eye replaced with glass - the way Mike Robertson got it after the weak link on the glider behind his boat improved the safety of his towing operation.
I've had a cable break at five meters from my tow-release. It smacked my passenger in the helmet.
Are you using polypro and nylon instead of Spectra and Dacron?
Lessons: Use a helmet with a chin protector, wear sturdy glasses if you can, keep your head outside the area where the cable would go if it would break. I now sometimes place my feet on the cable to make the cable hit my shoes if it should break at that point in time. (I do this especially when I feel vulnerable because it is aimed straight at my head at that point in the tow.)
How 'bout THIS lesson:
Manned Kiting
The Basic Handbook of Tow Launched Hang Gliding
Daniel F. Poynter
1974
"The greatest dangers are a rope break or a premature release." - Richard Johnson
Don't tow with stuff that breaks or releases prematurely.
I would like to add my two cents into this discussion.
I have towed paragliders on static lines (yikes!), payout winches, scooter tows, and a true hydraulic driven ("pay-in") winch. The hydraulic winch is by far the smoothest, and requires very little of the operator once the pressure is set, unless you lock out or blow the launch.
It is absolutely possible to stall a paraglider by towing too hard. It's called "overtowing" and is essentially a high speed stall.
Bullshit. You don't stall the glider until you LOSE the tension.
As you load the wing with tow force it angles back farther behind the pilot, increasing the angle of attack.
It doesn't increase the ANGLE OF ATTACK. It increases the PITCH ATTITUDE.
If you have a sufficiently high tow force the point WILL COME where the angle of attack meets the stall point.
Ever actually seen that happen?
While I am familiar with the typical tow bridle used on paragliders, I am at a total loss as to why a "v" bridle with a central release is used. It puts the release essentially out of reach...
You mean like the:
- tow release on a sailplane?
- elevators on a sailplane?
- engines on a 747?
Yeah Dan, as much of a bitch as this aeronautical engineering game is, sometimes ya just gotta take the time and effort to do things right when people's lives are always - or even occasionally - certain to depend upon them.
...and puts all the hardware where it is likely to do the most damage in a line break or high pressure release.
- Yes. A high PRESSURE release.
- You mean the way all these hang gliding platform launchers are always getting disemboweled by their three-strings?
- It's only gonna do damage if you're using elastic materials (read nylon) aft of the separation point.
I've been towing for the last two years with a release mounted at my right carabiner, and a two to three foot bridle that threads through a loop at the end of the towline (which is formed by a small piece of aluminum tube threaded over a loop in the tow rope)...
It's called a tow ring.
...and attaches to a simple barrel type release on the left side.
A simple one? Or something with the requisite curved pin that everyone in these idiot sports finds so aesthetically pleasing?
This way I have a secondary if anything goes wrong with the main release.
Like WHAT? If you're flying with a primary release with which there's a possibility of anything going wrong you're an asshole. Bear in mind that when the shit really hits the fan NOBODY - and I mean NOBODY - lives long enough to get to a secondary release. Lotsa people don't even live long enough to blow the primary.
The advantage is:
1) vastly less mass in front where it can hit you; and
Just how much mass do you need to incorporate in the design of a paraglider release?
2) you have a secondary release if something goes wrong...
I don't do "if something goes wrong". There's zero excuse for that kind of bullshit. If it's too much trouble to get that much right then find another hobby.
...(like when my release line broke, I didn't have to fumble with finding the pin - which was reachable - I just hit my secondary).
- You're not talking about a SECONDARY release. You're talking about a BACKUP release.
- LIKE WHEN YOUR RELEASE LINE BROKE? Just how hard were you pulling on it before it broke? You can't even do the engineering for a lanyard that won't break when you try to release?
- Your LANYARD broke but your WEAK LINK didn't?
A secondary is completely standard with most hang gliding aerotow releases...
- Yeah, take a lesson from hang gliding aerotowing. Hard to go wrong with any of those models.
- A secondary CAN'T be COMPLETELY standard with MOST hang gliding aerotow releases.
- Nobody in aerotowing with an IQ up into double digits or more uses a secondary release as backup.
- And you're not saying anything about the one legitimate reason for having and using a secondary.
- And when you release from:
-- between the bridle apex and the tow ring you don't have a possibility of a bridle wrap
-- one end of a bridle you introduce the possibility of a bridle wrap
...(my local field won't let you fly without one).
- Who's your local field? Cloud 9 / Tracy Tillman? Guess we know fer sure what shape pin you're using - as if we didn't already.
- If you're flying two point, what field DOES let you fly without one?
- If you're flying one point with one of those stupid overlength bridles I know you're using, what field requires - or even encourages - you to fly with one?
I don't understand why this isn't standard in paragliding.
There's an astronomical amount of stuff about this game that you don't understand, Dan.
It also isn't very hard to arrange an "auto release" function for step towing so that if the line is pulled back hard (drum snags) you will release (although making it not release inadvertently might be harder).
And it's even easier to arrange a "manual release" function for step towing so that if the line is pulled back hard (drum snags) you will release the damn thing yourself and won't hafta worry about it inadvertently releasing. The Koch isn't a bad option.
Finally, while I understand that this is controversial, someone needs to explain to me just exactly how a weak link makes towing paragliders safer for anything other than step towing.
Wow. A controversial statement about weak links in Rogallo based glider towing. Who'da thunk?
Lemme tell ya how a weak link makes towing paragliders - or ANYTHING ELSE - safer for EVERYTHING including STEP TOWING:
Tost Flugzeuggerätebau
Weak links protect your aircraft against overloading.
It protects your aircraft against overloading.
And if you're stupid enough to try to use it for ANY OTHER PURPOSE you're gonna get people killed.
One of the most dangerous things I have witnessed is a weak link break in the first thirty feet of a tow.
Please note that the weaklink *saved* her ass. She still piled into the earth despite the weaklink helping her... for the same reason it had to help... lack of towing ability.
Did you consider what could've happened to the guy if the weak link HADN'T broken in the first thirty feet of a tow?
THE REAL danger on a tow is a lockout...
No it's not.
Manned Kiting
The Basic Handbook of Tow Launched Hang Gliding
Daniel F. Poynter
1974
"The greatest dangers are a rope break or a premature release." - Richard Johnson
The REAL danger on a tow is a STALL. Always has been, always will be.
And saying the REAL danger on a tow is a stall is pretty much the same thing as saying the real danger on a tow is a weak link - which is pretty much what you just said.
...but a properly rated weak link...
What the hell do you mean a "PROPERLY RATED WEAK LINK"? None of you motherfuckers has breathed a single syllable on the subject of actual RATING so far.
...WILL NOT BREAK IN A LOCKOUT (otherwise they should be impossible with regulated tow force systems like payout winches or hydraulic winches, yet they are certainly possible on such systems).
So a properly rated weak link is apparently something over the tension you're setting on the winch. Or, in hang glider aerotowing, about the same as normal tow tension.
We had six weaklink breaks in a row at Zapata this year.
Or a bit less if you really wanna keep things safe.
If you have a system that regulates pressure, and an operator who is not asleep, what does a weak link do except increase the chance that a momentary surge in tow force causes an inadvertant release close to the ground, right as you have gotten whacked?
Lemme try again.
Weak links protect your aircraft against overloading.
I have towed hang gliders for well over a decade, and EVERY SINGLE CLOSE CALL I HAVE EVER HAD WAS FROM A WEAK LINK BREAK.
Did it ever occur to you to beef them up a little bit? Or, if that's way beyond your capacity, just eliminate the goddam things altogether?
I have NEVER seen a weaklink "save" anyone from anything.
Weak links are there to protect the equipment not the glider pilot. Anyone who believes otherwise is setting them selves up for disaster.
It's not SUPPOSED TO "save" anyone from anything. It's just there to make sure the glider doesn't break up.
When aerotowing, it is a must to protect the tug pilot...
Bullshit. It's only there to protect the tug if and when the alleged "PILOT" is too fuckin' stupid and incompetent to do keep himself safe. The weak link doesn't give a rat's ass about protecting the tug pilot.
Dick Reynolds - 1992/11
Rising Fawn, Georgia
I took my eyes off the indicator to watch the hang glider's progress when the engine abruptly seized. I can distinctly remember taking my hand off the throttle to wave the hang glider off, and it was at that point that I fully realized there was no time! I pulled the release and pushed the stick forward.
All this occurred somewhere around fifty feet. The combination of high nose angle plus the pull exerted by the climbing hang glider brought me to a screeching halt, so to speak. I believe my response time was less than a second, but this still me just hanging with very little elevator authority. The nose fell through the horizon to 30 degrees negative and the ground rapidly rushed toward me. I attempted to pull up at approximately 25 to 30 feet, with no response. My feet, butt, and gear impacted simultaneously.
I consider myself fortunate in that my friends were there to immobilize me. The doctors tell me that I'll be walking in a year or so, but that I shouldn't plan on winning any foot races.
(And I'm not saying this guy was stupid and incompetent - but he screwed the pooch looking out for somebody else who didn't need looking out for instead of prioritizing threats and looking out for himself.)
...but even then I have known tug pilots (I am one) to release a glider too far out of whack much more often than the weak link does it for them.
- Have you ever known a tug driver who would've been unable to safely lose a glider using the release even if there had been no weak link anywhere in the system? I'm not hearing you cite any incidents.
- The purpose of the weak link IS NOT to release a glider too far out of whack. If that were true and the weak link could do it then it would be impossible to lock out and crash. And it's not.
- And anyway... All you fuckin' Dragonfly morons are too fuckin' stupid to follow regulations...
The United States Hang Gliding and Paragliding Association, Inc.
Standard Operating Procedure
12. Rating System
02. Pilot Proficiency System
10. Hang Gliding Aerotow Ratings
-B. Aero Vehicle Requirements
05. A weak link must be placed at both ends of the tow line.
...or even apply a few milligrams worth of common sense and configure your systems so that the fuckin' weak link...
Towing Aloft - 1998/01
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!
Tracy Tillman - 2001/05/16 15:14:55 UTC
Cloud 9 Sport Aviation
Webberville, Michigan
We (and many others) do not recommend using a second weaklink on the non-released end of the bridle.
...does you any good on the almost unmeasurably rare occasion when you actually DO need one.
P3, H4 Observer
What the fuck are you observing? You're seeing and experiencing all this dangerous crap...
One of the most dangerous things I have witnessed is a weak link break in the first thirty feet of a tow.
...what does a weak link do except increase the chance that a momentary surge in tow force causes an inadvertant release close to the ground, right as you have gotten whacked?
I have towed hang gliders for well over a decade, and EVERY SINGLE CLOSE CALL I HAVE EVER HAD WAS FROM A WEAK LINK BREAK.
I have NEVER seen a weaklink "save" anyone from anything.
...and you just keep doing the same idiot bullshit over and over and over and over and over and over. Are you expecting the results to get better? What the hell good is OBSERVING anything if you're totally incapable of LEARNING anything and DOING anything to fix the problems.
A tug pilot and/or aerotow operator has every right to inspect the use and quality of the weaklink used by a hang glider pilot, and has a duty to him/her self and the hang glider pilot to make sure that it is not too strong for its primary purpose. Concurrently, the hang glider pilot has a duty to understand and respect the well-founded concerns of the tow pilot and/or aerotow operator.
If you see Tracy, tell him to go fuck himself for me.
Mark "Forger" Stucky - 2005/06/26 04:11:50 UTC
Palmdale, California
A weak link is there to help you for the very rare mechanical failure such as the tow rope getting tangled on the drum or something "downstream" of the disk brake, the tow pressure somehow getting cranked too high, disk brake locking up, etc.
- PURE UNADULTERATED BULLSHIT.
- The fuckin' weak link is there for ONE PURPOSE and ONE PURPOSE *ONLY*.
Tost Flugzeuggerätebau
Weak links protect your aircraft against overloading.
It protects your aircraft against overloading.
- It is not there to help you:
-- for the very rare mechanical failure such as the tow rope getting tangled on the drum or something "downstream" of the disk brake
-- when a:
--- tow PRESSURE somehow gets cranked too high
--- disk brake locks up
-- with any et ceteras
- It is not there to help YOU - PERIOD.
It may or may not blow in the course of anything you can cook up and you may or may not still be alive after it does or doesn't.
- If you're too fucking stupid to be able to tell the difference between TENSION and PRESSURE then shut the fuck up and don't write any books on towing.
Depending on the winch, a weak link may save your ass at extreme lateral rope angles where there is a lot of tension but it isn't parallel to the winch drum so the brake isn't releasing...
And it may not. And even if it does your ass's prospects won't be all that great with respect to the ensuing stall recovery attempt.
...(I know, a good operator should dump it before it gets that far).
The assumption being - of course - that there's no fuckin' way the glider's gonna be able to release himself with the crap the good operator has sold him and/or allowed him to hook up with.
A weak link is just another layer of protection...
BULLSHIT. It's a necessary evil to protect against equipment overload and you better not let yourself get into a situation in which you need it 'cause you may not be around for very long after it does the job that you just made necessary.
...it should not be a hazard.
It bloody well IS a hazard - especially when you assholes dumb it down to try to get it to do jobs for which it's not designed.
If surge from a low altitude weak link break is too severe then you are launching with too much tow pressure.
Fuck you.
- You hit a gust or thermal right after launch the plane's gonna pitch up no matter what PRESSURE you're using and you can stall the next time the air does something different. And you can REALLY stall if you suddenly subtract the tow tension vector at about the same time. Which is EXACTLY what's most likely to happen with this crap you assholes are trying to use to do the job of the pilot and release.
- Sometimes the guy whose ass is on the line DOES get launched with too much tow PRESSURE by some bozo on the other end. And there's not a goddam thing he can do about it other than ride it out and pray that his fucking little loop of fishing line doesn't suddenly improve the safety of the towing operation.
- Aerotowed hang gliders ALWAYS launch with too much tow PRESSURE. The tugs need to fly faster than we like to go. So we've always got one thing working against us before you start throwing in Ma Nature and a bunch of lunatic theories and opinions about weak links.
If you really need that much pressure then wait until 200 feet agl before you crank it up to the "full" pressure.
- Are you sure we should be using AGL? Wouldn't MSL work a little better?
- And, of course, the assumption is that you won't ever get hit on a runway with the same shit you get hit with after you launch off a ramp with the advantage of the ground dropping away from you.
- Do you wanna say anything about G RATING? Just kidding.
- We DON'T "NEED" it, asshole. But we DO "NEED" to be able to DEAL with it WHEN it happens.
- Did you hear ANYTHING Dan JUST SAID?
- Have you been living in a fucking CAVE for the past quarter century while gliders towing under Doctor Hewett's wonderful safety criteria have been raining out of the sky?
Bonus points if you can guess the strength of the weak link at the end of the tow rope in the avatar.
Now try asking these assholes if they can guess the strengths of the weak links that they're all putting on their own and everybody else's gliders. Talk to Steve Kroop and Paul and Lauren Tjaden if you want some really expert opinions.
My issue with weak links is that they typically fail at the worst possible moment. I don't tow with a lot of pressure down low, but on tow you are anchored to a system with some inertia (not the same as free flying). It is not that hard to be pitched up relatively steeply by a sharp gust.
Even with a hydraulic winch, the mass of the drum, and the drag of the line lead to a delay in the system's relieving of the added tow pressure. This short burst of increased tow pressure doesn't present a danger unless the damned weak link breaks (which it is very likely to as it has no "delay" to match the lag in the system) and you are low to the ground.
How many times have you had the pads lock up on your payout winch? How often have you seen the line catch on some part of the winch - WHILE IT WAS UNDER TOW. I have towed hang gliders a lot more than paragliders, but I have had two low level weaklink breaks on paragliders, and TEN on hang gliders, about half of which very pretty exciting (just getting upright in time in the hang glider required fast reflexes). These always happened right as I got whacked by some gust/thermal, and the sudden, unexpected release of tow pressure didn't make the situation easier to deal with, quite the contrary.
As I stated earlier, in my entire flying career (towing for about fifteen years) I have NEVER SEEN A WEAKLINK SAVE ANYONE FROM ANYTHING! I have seen a number of crashes, and the weaklink didn't break till they hit the ground (by which point the tow pressure was off already). In that same period I PERSONALLY have been endangered a dozen times by sudden, unexpected, total release of tow pressure right as I am being pitched up by a gust/thermal.
If you can control your wing, the line is your friend. If it is so bad you can't, release! If you can't release, there is some small chance that the weak link MAY release for you (but not in a "normal" lockout), but I personally would much rather rely on the winch operator in such a rare occurrence, than the random release of the line provided by a weak link.
For a weak link to provide the critical measure of safety, you have to have:
1) the kind of mechanical failure described; combined with
2) poor/inadequate response from the winch operator: AND
3) somehow be unable to release yourself.
HAS THIS EVER HAPPENED IN THE ENTIRE HISTORY OF TOWING PARAGLIDERS?
Would using a release system that included a secondary means of release make such an occurrence almost impossible?
I have twice had a "mechanical" failure of the pressure system. Once, static towing a PG with my dad, he simply floored it when "the pressure needle kept bouncing around so I ignored it", and again - static towing - when the line hooked under a runway light and the pressure suddenly shot up. I RELEASED.
I had an incompetent tow operator plus no observer the first time (STUPID), and my weaklink DIDN'T release as I locked out as I let go of the brakes to reach for the release on my "standard" style "v" bridle (the weak link was probably a little too strong, but with a static line, it simply snapped every time as you pulled up the glider otherwise). The second time, the tow car was just reacting to the problem as I released (but static towing paragliders sucks no matter what).
Again, I'm not talking theory, I'm asking other pilots to recount how often they've been dumped off, low, in a "tight spot" by a weak link break, versus the number of times they've PERSONALLY WITNESSED or have experienced being "SAVED" by a weak link break. I figure it has to have happened somewhere, somewhen, but does it remotely compare to the DAILY OCCURRENCE (if you are launching in thermals), of unnecessary, unneeded weak link breaks that actually add to the danger if they happen close to the ground?
If you are using a decent tow system (not static line) with a competent operator isn't it possible that it is safer to tow without a weak link? This has certainly been my personal experience and observation.
Well, I can recall a time when having a weaklink was very useful for me, here. If you come off the cart early and hit the ground, you'd like the tow rope to break so that you are not pulled along the ground anymore than necessary.
And other examples....
Of course, there are always exceptions.
Sometimes there are road accidents where having NO seatbelt saved a life, a body flung from a burning vehicle for example.
The outcome of the above weaklink example could have been completely different, better or worse, if the weaklink had snapped an instant earlier, later or not at all.
A weaklink is not there to help your crashes, although sometimes it might, sometimes it might not.
Any tow flight takeoff, where you are teetering on the edge of losing the line, without warning, during this most critical time and while at this most abnormal glider attitude, has the potential to kill or hurt you.
Unlike a crash, a lockout or all the other random examples people give for a weak weaklink being better for you,
YOU SUBJECT YOURSELF TO THIS RISK EVERY TIME YOU TAKE OFF.
The fact that this risk is PUT THERE BY DESIGN I find almost unbelievable.
I have my own theories, based on my own experiences in the UK, as to how this teetering dangerous practice seems to have gained worldwide adoption and it has nothing to do with safety or some carefully worked out formula designed to offer the maximum protection.
Most of the time a weaklink break has a mild or insignificant outcome, and can be described as a non event.
Sometimes the outcome is described as a non event ONLY BECAUSE AT THE TIME THE PILOT HAD SUFFICIENT HEIGHT TO SURVIVE. This is definitely NOT a non event.
I would consider our club to be a very safety conscious outfit and yet on 2 occasions this year so far I have witnessed weaklink breaks where the outcome would have been very different for want of 30 or 40 feet.
Next time at the towfield count the number of lockouts, the number of falling off the cart instances, the number of times a pilot is dragged down the runway or any other instance where a weaklink break might be said to affect the outcome. The chances are this will be zero.
Then look at every launch, look at the first dozen feet or so and imagine a weaklink break at that critical point, see how many hits you get.
The vast majority of pilots fly without question with whatever their club/organisation give them. However, there are more then a few pilots not happy with the generally adopted weaklink values inherited from the '80s, although there are none quite a vocal as Tad.
In the future pilots will look back at this era and wonder why we were all so blind when it comes to weaklink values, just as we now look back and wonder why we ever flew without tip sticks or other dive recovery devices.
My issue with weak links is that they typically fail at the worst possible moment.
Yeah...
Donnell Hewett - 1980/12
Now I've heard the argument that "Weak links always break at the worst possible time, when the glider is climbing hard in a near stall situation," and that "More people have been injured because of a weak link than saved by one." Well, I for one have been saved by a weak link and would not even consider towing without one.
Funny how that works.
- You use device which - in REAL aviation - is used to...
Tost Flugzeuggerätebau
Weak links protect your aircraft against overloading.
...protect your aircraft against overloading.
- You come up with some ABSOLUTELY *LUNATIC* "THEORY" about using it to...
The system must include a weak link which will infallibly and automatically release the glider from tow whenever the tow line tension exceeds the limit for safe operation.
...protect the pilot from lockouts and stalls.
- You ignore any experience, evidence, information, data, ten year old kid common sense thinking...
Manned Kiting
The Basic Handbook of Tow Launched Hang Gliding
Daniel F. Poynter
1974
"The greatest dangers are a rope break or a premature release." - Richard Johnson
...that indicates that your lunatic theory is total crap.
- You dumb down the weak link accordingly such that its maximum allowable rating barely overlaps the minimum legal rating for aircraft with much higher lift to drag ratios and speed capabilities and much lower tow tension requirements.
- And then you're surprised when every time the tow tension gets a little over normal the glider pitches up, the Hewett Link blows, and the glider stalls and crashes.
I don't tow with a lot of pressure down low, but on tow you are anchored to a system with some inertia (not the same as free flying). It is not that hard to be pitched up relatively steeply by a sharp gust.
It's actually a bit difficult NOT to be - on tow or not.
Even with a hydraulic winch, the mass of the drum, and the drag of the line lead to a delay in the system's relieving of the added tow pressure. This short burst of increased tow pressure doesn't present a danger unless the damned weak link breaks (which it is very likely to as it has no "delay" to match the lag in the system) and you are low to the ground.
Yeah...
"The greatest dangers are a rope break or a premature release." - Richard Johnson
Pretty basic concept of ten year old kid kite flying.
How many times have you had the pads lock up on your payout winch? How often have you seen the line catch on some part of the winch - WHILE IT WAS UNDER TOW. I have towed hang gliders a lot more than paragliders, but I have had two low level weaklink breaks on paragliders, and TEN on hang gliders, about half of which very pretty exciting (just getting upright in time in the hang glider required fast reflexes).
Good thing too. If there had been a narrow dry riverbed with large rocks strewn all over the place you'd have been ready for it.
Nothing like using one dangerous lunatic hang gliding convention...
These always happened right as I got whacked by some gust/thermal, and the sudden, unexpected release of tow pressure didn't make the situation easier to deal with, quite the contrary.
I'da thunk you'd have learned to expect it by this point.
As I stated earlier, in my entire flying career (towing for about fifteen years) I have NEVER SEEN A WEAKLINK SAVE ANYONE FROM ANYTHING!
Tost Flugzeuggerätebau
Weak links protect your aircraft against overloading.
But I'll be you've seen a lot of aircraft being protected from overloading...
I have seen a number of crashes, and the weaklink didn't break till they hit the ground (by which point the tow pressure was off already). In that same period I PERSONALLY have been endangered a dozen times by sudden, unexpected, total release of tow pressure right as I am being pitched up by a gust/thermal.
Got any thoughts about how you might be able to widen your safety margins a bit? Maybe I could get my old buddy Bob Kuczewski to walk you through the relevant Navier-Stokes equations.
If you can control your wing, the line is your friend.
Kinda like the Rotax is your friend if you can control your Dragonfly?
If it is so bad you can't, release!
The PILOT should use his RELEASE to release? How's he gonna get to that lever on the downtube when the shit hits the fan? Betchya didn't even think of that, did ya?
If you can't release...
Why should you not be able to release?
- Name a single release failure in the entire history of hang or para gliding that wasn't easily predictable on the ground.
- If you can't preflight your release system to the extent that you're one hundred percent confident in its integrity and reliability what makes you think you can preflight the rest of the aircraft?
...there is some small chance that the weak link MAY release for you...
If it's loaded to its breaking strength - a little issue that NOBODY'S EVEN *MENTIONED* YET - there's a one hundred percent chance that the weak link will release you - or maybe just one end of your bridle if you're a Dragonfly driver or some other flavor of total moron. But that's the only prediction you can make about weak link performance.
...(but not in a "normal" lockout), but I personally would much rather rely on the winch operator in such a rare occurrence, than the random release of the line provided by a weak link.
What? Don't you think the weak link could go through a training program to improve its decision making skills?
For a weak link to provide the critical measure of safety, you have to have:
1) the kind of mechanical failure described; combined with
2) poor/inadequate response from the winch operator: AND
3) somehow be unable to release yourself.
HAS THIS EVER HAPPENED IN THE ENTIRE HISTORY OF TOWING PARAGLIDERS?
No. But if this ever happens just once fifteen years from now all of the clogged launches, crashed gliders, and broken downtubes, arms, necks will instantly become WORTH IT!
Would using a release system that included a secondary means of release make such an occurrence almost impossible?
Using a release that didn't include a secondary and wasn't slapped together by some flight park shit would make such an occurrence TOTALLY impossible. Well, for hang gliding you'd need a secondary to deal with a bridle wrap but the chances of you needing to use it in an emergency are pretty much zilch.
I have twice had a "mechanical" failure of the pressure system. Once, static towing a PG with my dad, he simply floored it when "the pressure needle kept bouncing around so I ignored it", and again - static towing - when the line hooked under a runway light and the pressure suddenly shot up. I RELEASED.
Shouldn't you have gone for your hook knife first - just to be on the safe side?
I had an incompetent tow operator plus no observer the first time (STUPID), and my weaklink DIDN'T release as I locked out as I let go of the brakes to reach for the release on my "standard" style "v" bridle...
Can you maybe see a problem or two with that procedure under a certain set of circumstances?
...(the weak link was probably a little too strong...
English or metric too strong?
...but with a static line, it simply snapped every time as you pulled up the glider otherwise).
Oh. So a little too strong is something that doesn't simply snap every time as you pull up the glider. So just right is something that DOES simply snap every time as you pull up the glider. Glad we clarified that. Can you express that in Gs so we can get it standardized for all tow operations?
The second time, the tow car was just reacting to the problem as I released (but static towing paragliders sucks no matter what).
But you're willing to do it anyway. But so far you HAVEN'T been willing to up your weak link ten or fifteen pounds.
Again, I'm not talking theory...
Don't worry...
Larry West - 2012/02/20 14:49:54 UTC
He was connecting his paraglider tow bridle to his harness (Z5) shoulder loops and I thought that was weird, and asked him about it. He told me "that's how I towed all week" so I asked him if he was going to tow with it over or under his basetube and he replied "I did both and it doesn't make any difference."
This scared me, so I asked him how much theory Mark taught, and my buddy said "None. We just flew a lot." I laughed and said "That's cool, but they had you take a written test, didn't they?" and he got mad (he was already stressing) and said "Larry, we just flew and those guys said I was flying like a Hang 3.", at which point I just walked away and waited for something bad to happen......which it did 5 minutes later.
So I don't give much credence to something that someone doesn't agree with about what we do for some theoretical reason.
Take this weaklink nonsense.
What do I "advocate"?
I don't advocate shit... I *USE* 130 test lb, greenspun cortland braided fishing line.
It is industry standard.
It is what *WE* use.
If someone's got a problem with it... we've got over ONE HUNDRED THOUSAND TANDEM TOWS and COUNTLESS solo tows that argue otherwise. So they can politely get stuffed.
As my friend likes to say... "Sure, it works in reality... but does it work in theory?"
Hahahahhaa... I like that one a lot
There's not much use for theory in these sports.
I'm asking other pilots to recount how often they've been dumped off, low, in a "tight spot" by a weak link break, versus the number of times they've PERSONALLY WITNESSED or have experienced being "SAVED" by a weak link break. I figure it has to have happened somewhere, somewhen, but does it remotely compare to the DAILY OCCURRENCE (if you are launching in thermals)...
Jim Rooney - 2011/08/28 19:39:17 UTC
Weak links break for all kinds of reasons.
Some obvious, some not.
The general consensus is the age old adage... "err on the side of caution".
The frustration of a weaklink break is just that, frustration.
And it can be very frustrating for sure. Especially on a good day, which they tend to be. It seems to be a Murphy favourite. You'll be in a long tug line on a stellar day just itching to fly. The stars are all lining up when *bam*, out of nowhere your trip to happy XC land goes up in a flash. Now you've got to hike it all the way back to the back of the line and wait as the "perfect" window drifts on by.
I get it.
It can be a pisser.
But the "other side"... the not cautions one... is not one of frustration, it's one of very real danger.
Better to be frustrated than in a hospital, or worse.
No exaggeration... this is the fire that the "other side" is made of. Best not to play with it.
I've personally refused to tow a flight park owner over this very issue. I didn't want to clash, but I wasn't towing him. Yup, he wanted to tow with a doubled up weaklink. He eventually towed (behind me) with a single and sorry to disappoint any drama mongers, we're still friends. And lone gun crazy Rooney? Ten other tow pilots turned him down that day for the same reason.
This has certainly been my personal experience and observation.
What about other pilots?
I dunno... Let's ask one.
Jim Rooney - 2011/08/26 02:44:10 UTC
Zach, you can nit pick all you like, but I'll put a 100,000+ flight record over your complaints any day of the week.
Let me see if I can clear up a few things for ya.
A lot of this I sent to Steve btw...
The "purpose" of a weaklink is not in question. Your semantics are.
The "purpose" of a weaklink is to increase the safety of the towing operation. PERIOD.
There are many ways in which it accomplishes this.
You're nit picking over what you call the "true purpose"... but all you're griping about is a definition... and an erroneous one at that.
Again, The weak link increases the safety of the tow.
Now, how it does this also provides a telling answer to one of the most hot button topics surrounding weak links... lockouts.
People will rail up and down that weaklinks do not protect against lockouts... which they don't.
But this is a half truth.
The whole truth is that while they don't prevent them, they help.
Where this discrepancy comes from is truck towing.
See, in truck towing, a weaklink does next to nothing for you (unless the line snags).
This is because you're on a pressure regulated system... so the forces never get high enough to break the link.
This is not the case with an aerotow.
This is why the weaklink exists.
The forces of an aerotow can get high enough to tear the wings off the glider.
This is no exaggeration... it can be done.
So think about it.
How is this accomplished?
Simply put... lock out.
So, in a lock out, the forces can very rapidly get so high as to destroy the glider?
So then, weaklinks do not help in a lock out situation?
You can see what I'm getting at here can't you?
Argue all you like about the "true" purpose of a weaklink... but it's only you that's arguing.
I find no disagreement in the professional community as to such.
I only find a disconnect when they're talking to the general public, and it always boils down to semantics.
See, we're not confused.
You're searching for an argument and only finding it within yourself.
This btw is one of the main reasons that most of the professionals do not bother with the forums.
Cuz it's generally a bitchfest around here.
Instead of looking for an argument, you may consider listening instead.
Perhaps I should start a separate thread, but I am really curious as to two issues I raised that aren't based on theory, but on my actual experience. Those issues are:
1) Why don't we generally place our releases at our carabiner, use a short threaded bridle, and a secondary release on the other side? This seems measurably safer in a number of ways, has worked well for me for years, yet I've never seen anyone else use such a release on a PG (a version of this is quite common in aerotowing hang gliders).
There is a theoretical possibility of the tail of the bridle somehow wrapping around the towline, but I've never seen it happen. This includes a decade of aerotowing hang gliders with usually a much longer threaded bridle. If it were to ever happen, wouldn't the secondary release work? In the meantime, you can easily reach your release, and you get the mass away from your face.
2) While I understand the theoretical benefit of weaklinks for towing a PG, my practical experience is that it actually raises the risk by dropping all line pressure just as you are being pitched up by a gust/thermal (pretty exciting near the ground), and I have never witnessed an occasion where it "helped". What are other pilot's real world experiences with added safety versus added problems with their weaklinks?
Perhaps I should start a separate thread...
Don't worry, there are hundreds of separate threads on these issues - all with the same concerns and conclusions. The problem is that low life motherfuckers like your buddy Tracy...
I'm Tracy Tillman, on the USHPA BOD, on the Tow Committe, and I am an Aviation Safety Counselor on the FAA Safety Team (FAAST) for the Detroit FSDO area. As a rep of both the USHPA and FAA, I would like to help you, USHPA, and the FAA improve safety in flying, towing, and hang gliding.
The FAA gets a lot of letters of complaint from a lot of yahoos...
...are always around make sure that nothing ever happens to fix the problems we identify.
...but I am really curious as to two issues I raised that aren't based on theory...
EVERYTHING in aviation is based on THEORY. It's what we all need to use to protect us from stupid motherfuckers like Tracy.
...but on my actual experience.
Fuck your actual experience.
- You do the theory, the theory will account for anything in your and anybody else's actual experience.
- You don't continue by looking at your actual experience. You continue by understanding Murphy's Law and modeling hypothetical worst case scenarios.
- Next you do the research on the incident reports and accounts...
Towing Aloft - 1998/01
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!
...which prove Murphy right.
- Then you do what should've been done in the first place...
A weak link must be placed at both ends of the tow line.
...and put a fuckin' weak link on the front end of the fuckin' towline or - better yet - on BOTH ends of the fuckin' bridle. You don't wait for another towline to snag in the trees and kill a Dragonfly and write it off as a freak "accident".
Why don't we generally place our releases at our carabiner, use a short threaded bridle, and a secondary release on the other side?
But I've had it once where the pin had bent inside the barrel from excessive tow force. My weaklink was still intact. The tug pilot's weaklink broke so I had the rope. I had to use two hands to get the pin out of the barrel.
Grade school science THEORY and common sense tell us they won't work under load.
- You have to take one hand off your controls to hit the primary release. That's asking for trouble right there.
- Your secondary release is a mirror image.
- In a worst case scenario your primary release will be very iffy and your secondary will be there just for show. It'll be like an extra fire extinguisher on the Titanic.
This seems measurably safer in a number of ways, has worked well for me for years, yet I've never seen anyone else use such a release on a PG (a version of this is quite common in aerotowing hang gliders).
The barrel release wouldn't work because we had too much pressure on it.
The Herald on Sunday - 2009/01/10
Hurt hang glider pilot joked bravely with friends after a crash landing, unaware that his injuries were fatal.
There is a theoretical possibility of the tail of the bridle somehow wrapping around the towline, but I've never seen it happen. This includes a decade of aerotowing hang gliders with usually a much longer threaded bridle.
Oh yeah... an other fun fact for ya... ya know when it's far more likely to happen? During a lockout. When we're doing lockout training, the odds go from 1 in 1,000 to over 50/50.
If it were to ever happen, wouldn't the secondary release work?
ASSUMING:
- you could afford to take the other hand off the other control;
- the tow tension were light enough such that when it got it's load doubled it wouldn't lock up;
- you still had the time to get to it...
Yeah, probably. But that wouldn't necessarily mean you'd still be alive three seconds later.
In the meantime, you can easily reach your release...
Holly is doing as well as can be expected after fifteen hours of surgery. The doctors came to see us around 10:45 last night. They said everything went fine. Once into surgery, they found many more fractures than were evident on the CT scan. Holly's face wasn't just cracked in a few places, it was shattered into many pieces over large areas. Piecing everything together and securing it in place was meticulous, time-consuming work.
How 'bout we prioritize our threats a little better?
While I understand the theoretical benefit of weak links for towing a PG...
You don't have a fuckin' CLUE.
Tost Flugzeuggerätebau
Weak links protect your aircraft against overloading.
You haven't EVEN ONCE MENTIONED ANYTHING about its actual PURPOSE. You haven't even once mentioned anything any number regarding Gs or even pounds.
...my practical experience is that it actually raises the risk by dropping all line pressure just as you are being pitched up by a gust/thermal (pretty exciting near the ground), and I have never witnessed an occasion where it "helped".
The weak link at the glider end must have a breaking strength that will break before the towline tension exceeds twice the weight of the hang glider pilot and glider combination.
- The bottom end of USHGA's allowable range for weak link strength is ZERO Gs.
- The top is TWO Gs.
- Try moving from where you are - which is pretty close to the bottom - towards the other end and see what happens.
- Idiot.
What are other pilot's real world experiences with added safety versus added problems with their weaklinks?
- You get tens of thousands of total morons trying to use load limiters as lockout preventers the real world experiences are gonna be pretty much the same.
I once locked out on an early laminarST aerotowing. went past vertical and past 45 degrees to the line of pull-- and the load forces were increasing dramatically. The weaklink blew and the glider stalled--needed every bit of the 250 ft agl to speed up and pull out. I'm alive because I didn't use a stronger one.
If you fire enough bullets into enough crowds you're gonna hit a Davis, Jack, or Rooney every now and then. That don't mean you're justified in firing bullets into crowds.
Furthermore, when a weak link HAPPENS TO BLOW in time to keep some bent pin / easy reach asshole like Marc it sends the very dangerous message that it's OK to keep flying with the kind of crap you guys are using so the slobs who participate in these sports are even LESS motivated no fix the problems.
When you're trying to get kids to buckle their seat belts you don't focus on the two or three idiots you can find who would've drowned or burned to death if they hadn't been thrown clear of the car before it went over the cliff.
Stu Caruk - 2005/06/28 21:03:57 UTC
Ridgefield, Washington
Since towing just happens to be my favorite means to get aloft, I feel somewhat compelled to make a few comments to this thread. I've done hundreds of towed launches from Scooter, Static, and Payout systems. I also run TowMeUp.com and we build a wide assorment of different style tow bridles and towing accesories, as well as probably one of the finest, smoothest operating Payout systems available. I am also an anal retentive type and I choose to not just accept comments as being factual information, but I typically tet most theories out myself.
But you're not much on spelling, spell checks, or proofreading, are ya Stuart?
As a result, we have load cells in house to break most anything we want to test. We use finite element analysis to calculate the loads and various forces involved on all our products and we have conducted extensive inflight and simulated tests.
One of the comments that really bugs me is those related to weaklinks. I started off with the mantra that you always needed to use a weaklink. Then I noticed during a lot of our early scooter towing adventures that weaklinks were breaking early on in the flight right after liftoff and causing probably more problems than they solved. Some pilots felt they were so dangerous that they refused to use weaklinks.
What ratings were you using and why?
We also had problems with several pilots gliders sufering from stretched lines. Observing the tow vehicle rear end bouncing on the ground during a tow... yes, they towed the pilot to a position directly overhead the vehicle...what can I say, it was the early days... I figured that having a weaklink was the BEST way to absolutley guarantee an upper limit on the tow forces involved.
BULLSHIT.
- It's physically impossible to tow a glider straight over a vehicle. He can fly over the vehicle if he wants after you pull him up but if he's straight up and still under tension you're not pulling him up - you're just making him heavier.
- You didn't stretch any lines because of any vehicle bouncing. It would've been totally irrelevant at low tow angles and at high tow angles there'd have been a couple thousand feet of line out and the sag would've dampened out any short tension spikes - which wouldn't have been any big fucking deals anyway.
- How come it was just SEVERAL gliders that got stretched?
- And the pilots were feeling loading that was pushing the limits of their gliders' capacities and not releasing? Bullshit.
- And, in any case, you're not putting gliders straight over the vehicle anymore.
I usually used one myself, but if one wasn't available, I felt safe enough towing without one. That is until the day I was testing a prototype pocket winch mounted to a jetski. In our haste to test the system, I had forgotten to include weak links, and the lake was to far away to run back toi the shop to grab some, so I skipped them. A fairly serious winch malfunction caused a huge surge which I was able to compensate for.
Sadly, as the glider surged a second time the tow tech nailed the thottle (he had seen the glider out in front of me when he looked back and figured I could do with even more tension). The resulting surge let the glider hit the towline so I released, only to have the drogue catch the glider and tangle it up. A reserve toss was the only quick soluion that came to me. If I had been bright enough to use a weak link, it would have been a non event, as the link most certainly would have broken on the first surge.
- You had the OPTION to RELEASE upon the first surge.
- Your DECISION as the PILOT was to compensate, recover, and remain on tow.
- Your driver then screwed the pooch at his end of the line.
- And how the hell are you so goddam CERTAIN that the weak link would've blown on the first surge?
- And so now you wanna use a weak link to override your decision as a pilot to stay on tow because that might keep you from getting tangled with a retrieval chute if your driver screws you over a wee bit later.
- Shithead.
Tow techs can't always drop the pressure.
- But they can always NOT NAIL THE THROTTLE.
- And the pilot can always release.
- And if the pilot CAN'T always release you've got more important things to be doing than writing a bunch of clueless crap about weak links.
I have seen vehicles drive over the tow line that runs from a scooter tow to the pilot standing in a field, catch the line, and drive off blissfully unaware of the situation. I've seen boats catch the towline, I've seen towlines that snagged under logs, or rocks that would tend to pull the pilot through them if they got airborne, I've seen towlines catch on bolts, cabin structures and the sides of truck canopies, as well as a host of times when it would be virtually impossible for the normal reduction of line tension to occur.
- So what:
-- the hell does ANY of that hafta do with weak links?
-- is stopping the PILOT from effecting an emergency reduction (elimination) of line tension?
I also note that most of the opponnets of the use of weak links come from the hang gliding community.
Really Stuart? You know how long I've been fighting weak links which improve the safety of the towing operation - PERIOD - and what the costs and my successes have been?
While I have the deepest respect for all the lessons the hang gliders pilots have taught us as paragliders...
- Yeah, that would explain a lot of things.
- All the lessons any of us ever needed to learn about towing our stuff was established by the sailplane people at the beginning of time. And there isn't much to that either.
...one thing I've learned is that towing hang gliders and towing paragliders are completely different operations.
BULLSHIT. The principles are IDENTICAL.
Hang gliders typically like far more tension on launch than is required to tow a paraglider.
Bullshit. We're heavier and faster but you're draggier. The tensions are about the same - and not all that critical anyway.
This is in fact one of the main things that I needed to unlearn from how I was taught to tow. Early on we were taught to let the tow tech crank up the line tension and resist the forward pull as long as was phsically possible, and then allow the tech to pull us into the air. Of course we also broke an inordinate number of weak links during the launch phase as well.
- Of course you did. Do we get to hear anything about pounds of tension and weak link strengths?
- So the only problem you were having with those launches was that you were blowing weak links. Do please tell us what strategies you used to address that issue.
It took a while to figure this out, but there is really no good reason to have your weaklinks break on, or shortly after launch. If they do, It is almost always a tow tech problem, compounded by a pilot who is too lazy to put forth the effort to ensure their glider comes cleanly overhead. Occasionally the glider is trimmed to slow due to age, or design, which compounds problems as well.
Bullshit. None of those issues is a blip on the tow tension range radar. The ONLY reason weak links break on or shortly after launch is because they're about a third the strength they should be.
Breaking a weaklink off launch with a hang glider can be a very serious problem...
No. It ALWAYS improves the safety of the towing operation. PERIOD.
...and like certain paraglider activities, it might be preferable to keep the pilot on line a bit longer to attempt to solve the problem.
Manned Kiting
The Basic Handbook of Tow Launched Hang Gliding
Daniel F. Poynter
1974
"The greatest dangers are a rope break or a premature release." - Richard Johnson
Do ya think?
I'll agree that weaklinks don't provide any protection from lockouts. They provide even less protection from a line jam during the downwind phase of a step tow.
NEITHER of those is the job of the weak link. So big surprise.
Weak links serve but one purpose, and only one purpose. Weaklinks ONLY ensure that a certain specific tow force can never be exceeded. If you use a link that breaks consistently at say 200 pounds, it means that if you exceed 200 pounds of tow tension the weaklink should break, and nothing more.
BULLSHIT.
The one purpose of the weak link is to...
Tost Flugzeuggerätebau
Weak links protect your aircraft against overloading.
...protect your aircraft against overloading.
And if you're using a two hundred pound weak link you are no way in hell using it to protect your aircraft against overloading.
I'm a big guy, and I clip in at 350 pounds or so. I use a weaklink line tied in such a manner that it consistently breaks at 284 pounds.
Idiot. We're talking 0.8 Gs before we throw in the glider, reserve, and rest of the equipment.
I never need to see tow forces over 140 pounds, and that's enough for me to hit over 450 FPM up, which frankly any more than that is just uncomfortable to tow with and unneccesary in our operations. I haven't broken a weak link in the last hundred or so tows, and of those times I can recall a link breaking, it's always been for a specific reason (usually overtowing, a line dig, etc).
- Of course you don't NEED to see tow forces over 140 pounds. And I don't NEED to see a twenty mile per hour crosswind gust low on final. But I've gotta be ready to deal with it if it happens.
- So what you're saying is that you're totally cool with blowing a 284 pound weak link if an overtow, line dig, etc. occurs right after launch while you're going up like a rocket.
- Good thing for your stupid ass that you do most of your towing over water.
Since we build a large number of winches a year, we also train quite a few tow techs. One of the cool parts about our Payout system is that I can limit the maximum towforce that our winch can achive to a value just above what I like to tow at (if it will tow me, it will tow most anybody). THis precludes the tow tech from greatly overtowing me on launch, and I have yet to break a weaklink on launch with one of our systems with even the most hamfisted tow tech.
Oh. They can and do blow at altitude but since you haven't yet blown one on launch that simply isn't an issue worth being concerned about.
I would suggest that if you are routinely breaking weaklinks, that you ascertain the true reason for the break, before discarding the use of the linek. After all if it breaks at a consistent calibrated force, and you remove it from the system you then have to figure out what the next weakest link is. You just might not want to find out the answer the hard way.
What if you didn't just throw it out of the system? What if you replaced it with something that would give you a sane margin?
One thing I'm fairly certain of though is that if your weaklinks are breaking consitently on launch, it is because the tow tech is adding far to much tension before the glider comes completely overhead.
We don't need any more assholes in these sports who are fairly certain of stuff, Stuart - we got tons already. We need people who know what the fuck they're talking about.
The glider hangs back, essentially flying almost constant stalled or in parachutage. The glider may not be able to come overhead without a reduction in tow force, which never seems to happen. In reality the tow tech simply sees the glider not climbing, and adds more tow force until something breaks. Usually it's the weak link...
It's ALWAYS the weak link. If it isn't the weak link isn't the weak link. And if the weak link isn't the weak link the tow operation is being run by total assholes and nobody should be going up in the first place.
...and depending on the height achieved, the pilot will pendulum in or pound in, or might get lucky damp the surge and land.
In other words, if you're not using shit equipment and everything holds...
Manned Kiting
The Basic Handbook of Tow Launched Hang Gliding
Daniel F. Poynter
1974
"The greatest dangers are a rope break or a premature release." - Richard Johnson
...the system can handle a few things going wrong at once and nobody gets killed.
Either way, it means the entire system of launching the pilot needs to be critically looked at, since in reality, it takes very little tow force to actually launch a paraglider pilot and get them climbing out.
Yeah Stuart. If you're blowing perfectly good three quarter G weak links, you should really look things over and see what you're doing wrong. And if your pet leopard keeps eating neighborhood kids you should probably see if they're wearing T-shirts of colors and/or patterns suggestive of a Thompson's Gazelle.
Certain devices help a lot. A tow assist (gee, we make a really nice one at http://www.TowMeUp.com) helps reduce the potential by trimming the glider faster automatically on launch if needed, and removing the trim when its not. What we really need to do though is take a critical look at how we are towing, and what precautions we have in place to minimixe excess towline tensions. Doing this allows the use of a weaklink.
Shithead.
If you're to lazy to look at your system, I'd prefer to see the use of a slightly stronger weaklink than none at all.
Yeah. Go totally nuts. Crank it up to 0.2 Gs over the legal minimum for sailplanes if you want.
There comes a point where you simply have to say "the maximum tension I ever want to see is XXX pounds --- kilos to most of the world" and use a weaklink to limit it to that value.
And you base that on the load capacity of the glider - NOT on what the most tension you'd PREFER to have on a launch.
As to where and how to hook up the bridle... there are dozens of ways. Id say use whatever works consistently for you. A pice of weak link line and a hook knife is probably the cheapest option...
Sounds like a plan to me!!! And if it's good enough for Matt Taber...
...ranging all the way up to some pretty elaborate and complicated solutions.
No! For the love of God!!! Not elaborate or COMPLICATED!!!
I'd be careful about stringing things up in your glider. The more complex you make things, the easier they fail. I've seen far too much of this stuff... simple is always better.
Stay with the hook knife and string. Can't beat something like that for simplicity and the resultant reliability!
If you carry a hook knife, which all paraglider pilots should, I'd find it hard to find a malfunction you can't solve.
Stuart, it is very interesting that you went from an unquestioning use of weaklinks, to at least questioning their validity, to using them all the time.
All without the slightest clue what their purpose was or what strength they should be.
While I have been towing some form of glider (if you count sailplanes)...
Yeah. Let's count sailplanes. Let's compare what THEY'RE doing to what WE'RE doing. And whenever we find a discrepancy let's assume that we're doing it WRONG.
...for over thirty years, I certainly haven't towed paragliders anything like the amount you have (there must be few in the US who have).
Hang glider aerotow operations throw so much stuff in the air so fast that Stu's a drop in the bucket. But it doesn't make any difference. The aerotow people are even stupider now than when they started out over two decades ago.
So I'll take your advice in the hopes of avoiding repeating your personal "learning curve" (that's the point of these discussions, isn't it?).
- When you're taking someone's advice that means that you don't have a clue what the issue is.
- That's also an excellent indication that the person from whom you're taking the advice doesn't have a freaking clue what he's talking about either 'cause if he did he'd be able to explain it to you and you'd understand the issue and wouldn't need to be taking anybody's advice.
Most of my experience with paragliders and weaklinks was on static lines where it was brutally difficult to regulate the pressure properly as you brought up the canopy.
What the hell does that have to do with any issues concerning weak links?
The only other problems were with scooter tows with an operator more used to hang gliders. We have experienced no troubles at all with gliders stalling on launch, but I think that much of that relates to the fact that we are towing with a fixed hydraulic winch set to a reasonable load (140-160 pound line tension).
In other words, you're not stalling gliders because you're not breaking weak links.
If the glider isn't flying, the winch won't launch it, and there is nothing the operator can do to "force it" into the air (unlike most scooters or payout winches - yours excepted). The rest of my troubles with weak links have come when towing hang gliders with payout winches and aerotowing. I solved these problems, as you suggested, by moving to a stronger weak link till I stopped getting "random" breaks (and my towing certainly seemed safer for it).
Wow. You beefed up the weak links and you're problems started going away. Who'da thunk? (Keep moving in that direction and you can start cutting down on some of the worst case scenario fatalities.)
It is a problem for our sport that we all figure these things out in fairly small, local groups, and stick with what seems to work even if we don't understand the mechanics as well as we think we do.
- You figure them out in fairly small, local, inbred, terminally stupid groups in which the people who fly the most are the people most revered and sought after for their expertise.
- The people who fly the most are the tug drivers.
- The reason tug drivers are tug drivers is because they're too stupid to be doing anything else.
- When you put a piece of equipment up five times in a row without killing anyone it seems to work.
- If it kills someone on the sixth tow it was due to pilot error and the equipment was not an issue because it was Industry Standard and had a perfect track record.
- And of course it STILL has a perfect track record 'cause the fatality was due entirely to pilot error.
I've towed in roughly a dozen different places (if you count hang gliders and paragliders) and NO TWO PLACES USED THE EXACT SAME PROCEDURES.
Don't worry. The aerotow people will all get on the same page with the worst equipment and procedures that each one has to offer.
In fact, some of the "RULES" flatly contradicted each other. Everything from tow forces, to bridles, to weak link issues, to launch procedures have varied wildly. Yet, I believe that there is a best, safest way to do this.
There is - but ya need to have a foundation in theory to really understand WHY what's working best IS working best.
You go to sailplaning anywhere in the world the instruction, procedures, equipment is all gonna be pretty much the same and nobody's gonna be going to "EXPERTS" for "ADVICE". Everything's in the fuckin' manual and the fuckin' manuals are all gonna say the same thing.
I take it that this is what the Towing Committee of the USHGA is all about, but I wonder if I would find some of their recommendations (rules) run so counter to my own experience that I wouldn't want to follow them?
FUCK the Towing Committee.
Doug Hildreth - 1991/06
Pilot with some tow experience was towing on a new glider which was a little small for him. Good launch, but at about fifty feet the glider nosed up, stalled, and the pilot released by letting go of the basetube with right hand. Glider did a wingover to the left and crashed into a field next to the tow road. Amazingly, there were minimal injuries.
Comment: This scenario has been reported numerous times. Obviously, the primary problem is the lack of pilot skill and experience in avoiding low-level, post-launch, nose-high stalls. The emphasis by countless reporters that the pilot lets go of the glider with his right hand to activate the release seems to indicate that we need a better hands-on way to release.
I know, I know, "If they would just do it right. Our current system is really okay." I'm just telling you what's going on in the real world. They are not doing it right and it's up to us to fix the problem. Think about it.
Luen Miller - 1996/10
We have two more fatalities because of a glider that couldn't be released from tow.
I am strongly recommending formal review and analysis of releases and weak link designs for all methods of towing by the Towing Committee, and that recommendations on adoption or improvements be generated.
I believe that from preflight through release we should have more standardized procedures in towing.
I'm Tracy Tillman, on the USHPA BOD, on the Tow Committe, and I am an Aviation Safety Counselor on the FAA Safety Team (FAAST) for the Detroit FSDO area. As a rep of both the USHPA and FAA, I would like to help you, USHPA, and the FAA improve safety in flying, towing, and hang gliding.
The FAA gets a lot of letters of complaint from a lot of yahoos...
Ask yourself this...
If the Towing Committee weren't now and hadn't always been a heap of useless shitheads and evil scumbags who didn't give a rat's ass about anything beyond preserving their shitrigged equipment monopolies and immunizing themselves from liability would you be going to any two separate tow operations and finding fifteen or twenty contradictory sets of procedures?
It's the problem - not the solution.
Well, in any case, I appreciate other experienced pilots willingness to engage in these discussions, and the avoiding of "Muuriesque" flames and put downs.
- You don't want EXPERIENCED PILOTS in these discussions. You want people who know what they're talking about. Experienced pilots are mostly people really experienced at doing things wrong with the skills and reflexes to be able to get away with it just about all the time.
- You need flames and put downs. You actually need heads on pikes 'cause civility doesn't work with the scum that's running these shows.
Again, I've flown PG's, and towed for quite a while, but I still have definitely learned things from this thread.
Mark "Forger" Stucky - 2005/06/29 07:30:08 UTC
Palmdale
I appreciate Stu taking the time to speak up.
I'd have appreciated it a lot more if he'd taken the time to figure out what the hell he was talking about before he started running his mouth.
For what it's worth, I can't access the PG forum at work (anything with forum in the title seems to be blocked).
Maybe you could get a blocker that just does Stuart.
Since my family doesn't appreciate it when I come home from a long day at work and bury my nose in the computer, I don't get to this forum much anymore.
Anyway, the weaklink should function as a fuze. If it's blowing too readily then something is wrong.
Yeah. Maybe you're using the wrong fuse.
What's the manufacturer say...
Wills Wing
Always use an appropriate weak link with a finished length of 1.5 inches or less.
...about the rating?
Just as you shouldn't bypass an electrical fuze, you shouldn't get rid of a weaklink. You should however, fix the problem.
WHAT PROBLEM? There's nothing wrong with the glider, pilot, or driver. Maybe you're using the wrong the weak link.
One problem that you might encounter (if you don't have a smoothly running hydraulic winch like Stu makes) is tension spikes due to mechanical deficiencies in tow system. Pressure spikes can be caused by various reasons such as differences in static and dynamic friction of the winch brake, bumpy roads, gusty air, etc.
Maybe the problem is that you're not using a weak link that can handle tension due to mechanical deficiencies in tow system and pressure spikes caused by various reasons such as differences in static and dynamic friction of the winch brake, bumpy roads, gusty air, etc.
Modern low drag towlines have much less line stretch and hence much less shock absorption...
We're towing through AIR - pinbrain. Air has an astonishing degree of shock absorption. Ask around amongst people who use nothing but Spectra for any kind of towing you wanna name and see how many of them report feeling a SHOCK on tow.
We don't need shock absorption. We need tension (or pressure) CONTROL. And elasticity sends your tension control straight to hell.
...than the water ski ropes used in the old days...
The accident was produced by a Home-Made towing device, its seems that the towing line used (yellow nylon rope) breaked at the launching phase, producing a big surge at low, but fatal altitude. Peace to his soul...
...not so old days.
...(not that I'm advocating switching back).
Yes you are.
Such tension spikes could easily shockload a weaklink to failure.
- Could they shockload a glider to fail? (Moron.)
- Yeah. These tension spikes which you just invented could easily shockload a weak link with a capacity just over normal tension to fail. Would it also be likely to fail if a gust hits the glider and stands it on its tail just after launch?
If that is a problem with your tow system then you may want to try adding a length of nylon or polyproplyene rope to the glider end of the tow rope.
Yeah. Let's add some STRETCH to the system. Gotta take care of those shockloads which keep blowing our poor defenseless weak links.
A 2000 foot length of spectra might have only 20 foot of stretch prior to your weak link failing.
That statement is totally meaningless unless we know the breaking strengths of the towline and weak link. And you haven't given us the slightest hint of EITHER.
If you are using a payout winch then you might only have a couple feet of "give" shortly after lift off.
A couple of feet too goddam much.
Adding 50 feet of high-stretch rope would provide significant damping during the critical launch phase.
Are you related to Davis?
The tow rope in the avatar was a thousand foot length of three quarter inch diameter vectran (tensile strength of 60,000 pounds). To increase the damping we spliced a fifty foot length of nylon webbing into the center section of the rope.
Yeah, let's make our towline out of the lowest stretch fiber on the planet. But just to be safe let's add a length of the highest stretch fiber on the planet. Good thinking.
It significantly reduced tension spikes...
It also significantly reduced the tug driver's ability to control the situation and significantly increased lags and surges.
...and I never broke the weaklink inadvertantly.
How many times did you break the weak link advertently?
The weaklink was rated at 24,000 pounds which was 80% of my gross weight.
The absolute bottom of the FAA's legal range for towing sailplanes, forty percent of the top end, and a figure that was putting you so close to getting blown off that you had to be very careful flying in smooth air if you wanted to keep going up.
I think the same percentage is a good starting point for hang glider and paraglider weaklinks for ground-based towing.
BASED ON WHAT?
You picked a number, you found that that number was real marginal for the AERO towing you were doing, you didn't fly with any other numbers, so now you THINK that the same percentage is a good starting point for hang glider and paraglider weak links for GROUND based towing?
Manned Kiting
The Basic Handbook of Tow Launched Hang Gliding
Daniel F. Poynter
1974
"The greatest dangers are a rope break or a premature release." - Richard Johnson
What part of:
The greatest dangers are a rope break or a premature release.
are you having so fucking much trouble understanding?
Mark "Forger" Stucky
co-author "Paragliding -- A Pilot's Training Manual" (it even includes a chapter on towing!)
Oh GAWD - you DID write a book on towing. I swear that hadn't registered when I wrote:
If you're too fucking stupid to be able to tell the difference between TENSION and PRESSURE then shut the fuck up and don't write any books on towing.
I was only thinking of the other two coauthors too fucking stupid to be able to tell the difference between TENSION and PRESSURE who wrote a book on towing.
Mike Dufty - 2005/06/29 07:40:40 UTC
Western Australia
I have witnessed a situation where a weak link saved someone. They messed up the launch and tripped and the driver didn't realise and kept driving a short while. The weak link broke and saved the pilot from being dragged along the ground excessively.
- What's the G rating of a weak link that blows to keep a pooch screwing pilot from being dragged by a pooch screwing driver along the ground "excessively" but doesn't blow when a competent pilot being pulled by a competent driver gets nosed up by gust?
- Why couldn't the guy abort the tow? Couldn't get to the release you assholes keep pretending is safe?
It is also convenient to have a weak link that breaks before the towline does, as it's a lot quicker to replace the weak link than find the lost piece of line and repair it.
Please explain to me how a weak link that DOESN'T break before the towline does is a weak link?
May not be a problem with some winches, but most I have used have had a problem with line breaking, probably being too stingy in the line purchase.
I wouldn't call the motherfuckers stingy...
Manned Kiting
The Basic Handbook of Tow Launched Hang Gliding
Daniel F. Poynter
1974
"The greatest dangers are a rope break or a premature release." - Richard Johnson
Robert V. Wills
1977/09/25 - M. Horvath - 38 - Lake Eppalock, Victoria
Boat tow. Line broke or was released prematurely. Dived in from two hundred feet.
The accident was produced by a Home-Made towing device, its seems that the towing line used (yellow nylon rope) breaked at the launching phase, producing a big surge at low, but fatal altitude. Peace to his soul...
Towing Aloft - 1998/01
If a rope begins to break with a degree of regularity, inspect the line and replace all splices. If the line continues to regularly break, it is time to replace it.
Towing Aloft - 1998/01
As the towline wears from abrasion and UV exposure, its breaking strength diminishes. Typically pilots continue using a line until it begins to break on a regular basis at normal tow tensions. Given the general tendency by pilots to save money, it is probable that you will experience a line failure during a towing career.
I'd call the motherfuckers criminally negligent.
And I'd also call you guys a bunch of irresponsible useless douchebags for tolerating crap like that.
