Kite Strings

[This thread continues a discussion that began on the HHPA group.]

Tad,

Sorry for the delay getting back with you. Life got in the way and I wanted to do some research (including reading Dynamic Flight's articles and much of your 4144 Review document and skimming the 'Mousetraps' article and your photos).

Tad Eareckson wrote:I believe we were discussing weak links when so rudely interrupted. (And it was your move).

I think you've got me checkmated. No matter what I say you have a response and at this point I've got nothing left...I have no choice but to accept your position. I've seen so much fallacy from the people that push the universal 130 lb loop that I no longer doubt there isn't a good reason we use them. My hope for weaker links was aborting lockouts in the event of a release failure, but my thinking now is that if a lockout occurs low enough to end in a ground impact, it's likely this will occur before tension increases enough to break a 130 lb loop, and 130 lb loops are at risk of breaking at dangerous times. So yeah, having a better release is a much better idea.

Earlier I said that it seems every week something happens relevant to this discussion. I was at Lookout Thanksgiving weekend and experienced a weak link break at 700'. It happened after the tug climbed above me and I pushed out to follow...the same thing that happens many times through the course of any aerotow in thermic conditions. You can see it on video here (password = 'red'):
http://vimeo.com/17472550

2-1306
http://farm8.staticflickr.com/7258/13851486814_77efdf1004_o.png

I said I never had a weak link break since I started replacing them before each flying day, but my streak is now over - that weak link was brand new. When Bill found no variance in breaking strength between my unused and lightly used weak links (combined with reports of people using the same weak link for years), it made me wonder if replacing them was really the reason I wasn't breaking them. I'm now pretty sure it isn't.

You asked some questions about our experiment:

Tad Eareckson wrote:What glider(s) - model and size?

Sport 2 155 and Falcon 3 170. I hook in around 200 lbs.

Tad Eareckson wrote:Are the launch dolly tires properly inflated? Or are they totally flat like the bozos at Ridgely always leave them?

Properly inflated (as were the ones at Lookout two weekends ago). We check tire pressure at the beginning of each flying day.

Tad Eareckson wrote:Is the air smooth or turbulent?

Most of the tows were conducted in mid-day thermic conditions.

I think there may be some other factors. With the exception of one (the one that made me start replacing weak links religiously), all aerotow weak link breaks I've ever had have been at Lookout (I flew there almost exclusively my first two years of flying before moving to Houston). Lookout's tugs are more powerful than our trike, the tow rope they use is considerably shorter, and launches there are performed on grass (and sometimes slightly uneven terrain) as opposed to the paved runway at Columbus. I don't know what impact if any these factors have, but your description of operations at Ridgely, combined with some of Davis's comp reports and my own experiences at Lookout, indicate that our operation at Columbus is experiencing far fewer weak link breaks than some other operations, whatever the reason may be. But it's happened to me at Lookout enough that I'm tired of it. It's time to upgrade.

I've looked at your Shear Links and they look really nice. If I'm following the pictures, you've configured them at the end of a tow line as well as part of the bridle itself...is this correct? At any rate, I might be able to construct them and I don't think it would be too much trouble once I got proficient at it and have all the details figured out, but getting to that point is going to require a large enough time investment that I think for now I'm going to stick to string and just use something stronger. I'm not crazy about using two loops of 130 lb...I seem to recall you tested that to break around 200 lbs and I'd prefer something in the 260 lb range (1.4 Gs for my S2's max load if I did that right: 310 * 1.4 * .6), plus I've read that more strands means more variability in breaking strength. You can buy the same Cortland Dacron trolling line in a 200 lb flavor...I might get some and see what a loop breaks at. Also, Gregg gets weak link material from http://www.towmeup.com/weaklink.html, so I might try them out too. Naturally, whatever I use will have to be tested.

Zack

Sorry for the delay getting back with you.

No problem. I'd so much rather go with quality than speed.

Life got in the way and I wanted to do some research (including reading Dynamic Flight's articles and much of your 4144 Review document and skimming the 'Mousetraps' article and your photos).

Worth the wait.

There's some stuff in the FAA letter that's wrong that I've gotta revise. Subsequent to writing it I figured out that the whole "center of mass" thing is bullshit.

I think you've got me checkmated.

Damn. It's SO much more fun when some idiot challenges me on this issue (130 pound Greenspot). But - briefly - just for the benefit of the not yet enlightened...

In 1981 a Hang One by the name of Donnell Hewett got one halfway good and a whole can full of insane ideas about towing. One of the most lethal was that:

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.

This magic weak link - one G or 200 pounds - whichever is lower - would automatically ensure that the glider never got too far out of position, pitched up too steeply, rolled too far, was towed too fast, locked out, stalled, or fried in a violent electrical storm. And because he was - and is - a physics professor and your average hang glider pilot has about a quarter the understanding of the dynamics of towing as a Box Turtle, people swallowed this crap hook, line, and sinker.

The idea was to get the weak link down to a hair's breadth over ambient smooth air tow tension so you could go up with the most insanely dangerous release systems any lunatic ever dreamed about configuring for an aircraft with some sort of living thing on board.

And since the more forward you were pulling the less tension was required you should knock another third off of aerotow weak links.

And then the idiots in Florida reared their ugly heads. Even though I have you on the wagon I'd still like you to take this quiz I posted for you on the Houston forum just shy of a month ago:

This, until very recently, was up at Quest's website and had been for eons:
-
Weak Link

The strength of the weak link is crucial to a safe tow. It should be weak enough so that it will break before the pressure of the towline reaches a level that compromises the handling of the glider but strong enough so that it doesn't break every time you fly into a bit of rough air. A good rule of thumb for the optimum strength is one G, or in other words, equal to the total wing load of the glider. Most flight parks use 130 lb. braided Dacron line, so that one loop (which is the equivalent to two strands) is about 260 lb. strong - about the average wing load of a single pilot on a typical glider. For tandems, either two loops (four strands) of the same line or one loop of a stronger line is usually used to compensate for nearly twice the wing loading. When attaching the weak link to the bridle, position the knot so that it's hidden from the main tension in the link and excluded altogether from the equation.

IMPORTANT - It should never be assumed that the weak link will break in a lockout.
ALWAYS RELEASE THE TOWLINE before there is a problem.
-
Read it carefully and tell me how many incredibly stupid things wrong with that picture. I get into double digits. And this is the model that all the stupid clones who participate in this sport blindly follow.

So yeah, having a better release is a much better idea.

It's the ONLY idea. Dumbing down the weak link to compensate for a crap release makes even less sense than packing your air bag system with more explosive and lowering the actuation point so you can drive around with defective brakes and steering and no seat belt.

I was at Lookout Thanksgiving weekend and experienced a weak link break at 700'.

- I know where you were - I was spying on you on Jack's nasty little forum. Do you know or did you meet John Stokes on the ground? He and Dale are a couple of my absolute favoritist people in hang gliding. Spent some quality time with them and their raptor buddies when I was down there a year and a half ago. I'd really like to know if they concur with the Broad-Wings diagnosis I made regarding your mystery birds question. If not I would definitely defer.

- Right. And what do you think would've happened to you in a Dennis Pagen (low and rocketing up in a thermal) or Danny Brotto (low, rolled, and stalled) scenario? (Rhetorical question.)

- Those assholes oughta be stood up in front of a wall for allowing that kind of bullshit. I'm guessing you were seeing 175 pounds of towline tension MAX when that blew. Assuming that was the Sport (?)... Glider - 60, hook-in - 200, into weak link... Two freakin' thirds of a G. If you had twice that you'd still be on the anemic side.

- And that was the same weak link those assholes at Ridgely had ME flying all those horrible years - and my flying weight is sixty pounds over yours. They were saying the weak link held for 520 pounds of towline tension while it was frequently blowing at 125. May they rot in hell.

- And I'm guessing the thermals weren't all that violent a couple dozen days shy of the winter solstice with all those long afternoon shadows.

- That release configuration you're using is EXTREMELY dangerous. There'd be a really big body count if the stuff that usually just happens high - 'cause of the freedom of air to move vertically unimpeded by the ground - happened anywhere near as much low. I'll address it on the "Releases" thread - hopefully before your next opportunity to kill yourself.

Sport 2 155 and Falcon 3 170. I hook in around 200 lbs.

Tost #s 8 and 9 respectively. Table at:

http://www.energykitesystems.net/Lift/hgh/TadEareckson/index.html

Lookout's tugs are more powerful than our trike...

http://www.chgpa.org/forums/viewtopic.php?f=2&t=3661
Flying the 914 Dragonfly

Jim Rooney - 2008/12/06 20:01:49 UTC

You will only ever need full throttle for the first fifty feet of a tandem tow. Don't ever pull a solo at full throttle... they will not be able to climb with you. You can tow them at 28 mph and you'll still leave them in the dust... they just won't be able to climb with you... weaklinks will go left and right.

Yeah Jim. It's a whole extra thirty pounds of tension. And don't even dream about getting the weak link up anywhere near a G.

...paved runway at Columbus.

That alone would make me wanna quadruple my weak link strength.

It's time to upgrade.

It was time to upgrade thirty years ago.

I've looked at your Shear Links and they look really nice.

There are some high profile people using them... Sunny Venesky, Campbell Bowen, Rich Cizauskas, Steve Kinsley to name a few.

If I'm following the pictures, you've configured them at the end of a tow line as well as part of the bridle itself...is this correct?

The ones at the (glider) end of the towline have not been tested to see how they hold up to dragging - especially on a paved runway. They'd be fine for the tug end but for the back I'd be very inclined to go with Tost. And don't forget that Ken Hammond:

k.hammond209
at
btinternet
dot
com

can provide great tolerance / more finely tuned inserts for that setup.

The Shear Links I do for a primary / two point bridle are built in. I call it a Ribbon Bridle and it's EXCELLENT but labor intensive. Takes me over a day of joyless, tedious work to punch one of them out and I'm left two thirds blind when I'm finished.

The secondary / one point weak link is also the bridle - a Bridle Link. It's pretty quick and easy. Also very suitable for platform tow. I could be leaned on to produce a few copies.

I'm not crazy about using two loops of 130 lb.

I'm not either BUT... It's gonna blow between four and a bit over five hundred pounds of towline tension and there isn't a glider of any size that's safe to free fly that's gonna be bothered in the least by that kind of tension. A double loop of Greenspot isn't a bad-one-size-fits-all and you could live happily enough ever after using one.

310*1.4*.6

For a two point bridle... Yeah.

...plus I've read that more strands means more variability in breaking strength.

Fer sure. I'm too anal to be happy with something like that but it's not that big a deal if you don't go over a double. And when you start using thicker line you start getting bigger Fisherman's Knots and those don't help bridle ends feed through things smoothly.

http://www.towmeup.com/

That's Stuart Caruk. We don't like each other all that much but we know that the other one of us knows what he's talking about. He's really good on weak links. I'm a little better. And you're probably not going to find anybody even close in the surface towing, winches, affiliated hardware departments. And I got nuthin' there.

Naturally, whatever I use will have to be tested.

If you get something from Stuart it doesn't need to be tested. He does his homework.

Tad,

Tad Eareckson wrote:Subsequent to writing it I figured out that the whole "center of mass" thing is bullshit.

Can you elaborate? The 'center of mass' thing never made sense to me, but I figured Donnell knew what he was talking about being a physicist, and I don't think anyone doubts the benefits of attaching the tow line to the pilot.

Tad Eareckson wrote:Even though I have you on the wagon I'd still like you to take this quiz I posted for you on the Houston forum just shy of a month ago...

If you insist...

Quest wrote:The strength of the weak link is crucial to a safe tow.

The implication is that weak links need to break over a fairly small tension range for a tow to be safe. I'd say a rather large range is acceptable as long as it starts at 1 G.

Quest wrote:It should be weak enough so that it will break before the pressure of the towline...

'Pressure of the towline'...?

Quest wrote:...reaches a level that compromises the handling of the glider...

This was a new one for me. Considering we surface tow with higher tensions without handling issues, I don't know what they're talking about. Maybe they mean that higher tensions will only occur after handling has already been compromised (due to a lockout).

Quest wrote:...but strong enough so that it doesn't break every time you fly into a bit of rough air.

Does that mean it's OK if it breaks only some of the time? At any rate, it needs to be strong enough to tolerate a lot more than a 'bit of rough air'.

Quest wrote:A good rule of thumb for the optimum strength is one G, or in other words, equal to the total wing load of the glider.

Since they don't explain why one G is optimum, I can't really say anything here.

Quest wrote:Most flight parks use 130 lb. braided Dacron line, so that one loop (which is the equivalent to two strands) is about 260 lb. strong - about the average wing load of a single pilot on a typical glider.

This is the most incriminating statement of your excerpt. I can't believe how many people just assume that two strands of a line break at twice the rating of the line. (The authors of towing aloft do this almost immediately after stressing the importance of testing weak links to know their breaking strength.) But if that's not enough, they completely ignore the fact that the weak link doesn't see the entire line tension since the force is split in the bridle configurations used by 'most flight parks'.

Quest wrote:For tandems, either two loops (four strands) of the same line or one loop of a stronger line is usually used to compensate for nearly twice the wing loading.

Again the assumption that breaking strength is the single strand strength multiplied by the number of strands.

Quest wrote:When attaching the weak link to the bridle, position the knot so that it's hidden from the main tension in the link and excluded altogether from the equation.

IMPORTANT - It should never be assumed that the weak link will break in a lockout.

Can't disagree with any of that.

Quest wrote:ALWAYS RELEASE THE TOWLINE before there is a problem.

Why would you release if there's no problem?

It's stuff like this, including Wallaby's version and some of the stuff in Towing Aloft, that prompted my statement "I've seen so much fallacy from the people that push the universal 130 lb loop that I no longer doubt there isn't a good reason we use them."

Tad Eareckson wrote:Do you know or did you meet John Stokes on the ground?

I've known him for years. I met up with John and Dale breaking down after our flights Saturday and spoke briefly with them. John always seems to find me and say hello every time I go to Lookout. I haven't seen their raptor show yet.

Tad Eareckson wrote:I'd really like to know if they concur with the Broad-Wings diagnosis I made regarding your mystery birds question.

I didn't think to ask them about it. I haven't seen any more gaggles of the birds and I don't think I've seen individuals either. But when I see hawks now I wonder if they're Broad-Wings...I used to always assume all hawks were Red-Tails. Sometimes their red tails are really noticeable, but other times they're not.

Tad Eareckson wrote:That [paved runway] alone would make me wanna quadruple my weak link strength.

Can you explain? I figured towing off a runway would mean less initial resistance and thus less weak link stress. And we're not dragging weak links on the pavement.

Tad Eareckson wrote:Those assholes oughta be stood up in front of a wall for allowing that kind of bullshit.

At least they don't mandate 130 lb loops for everyone like some places. When I trained there I was told they recommend two loops for heavier pilots.

Tad Eareckson wrote:And that was the same weak link those assholes at Ridgely had ME flying all those horrible years....

Did they ever let you use your own weak links? Just wonderin' if you got to test them in the air.

Tad Eareckson wrote:And I'm guessing the thermals weren't all that violent...

It was around 3:30. The air was a bit rowdy getting out (a combination of thermal and mechanical turbulence) but relatively tame at the time the weak link broke. The tug pilot talked to me about it afterwards and did acknowledge the rowdiness, but I didn't think it was that bad.

Tad Eareckson wrote:I could be leaned on to produce a few copies.

Thanks, but I won't trouble you for now. I'd have to have a lot of extras to break in testing to ensure they have a consistent breaking strength (not that I doubt your work, but for something safety-critical I'm not just going to accept your word that they perform as described). I'd also like to stick with two-point bridles for now.

Tad Eareckson wrote:[Two 130 lb loops will] blow between four and a bit over five hundred pounds of towline tension...

I'd be happy with that...am I wrong about their breaking strength being 200 lbs? 200/.6 is only 333. What is the best way to configure two loops, anyway? Can it be done without tying the string directly to the bridle?

Tad Eareckson wrote:And when you start using thicker line you start getting bigger Fisherman's Knots and those don't help bridle ends feed through things smoothly.

Good point. I didn't think about that.

Tad Eareckson wrote:If you get something from Stuart it doesn't need to be tested.

I disagree. His weak links are rated for single strand breaking strengths in sewn configurations. I'll still have to test a tied loop's breaking strength (ideally with my own release and bridle).

A couple of questions...what is your recommendation for the strength of the weak link at a shoulder connection point of a two-point (V) bridle? I would think using the same thing as at the keel would be fine, but I want to be sure.

What weak link breaking strength do you recommend for the tug end of the line?

It seems to me that Tost weak links would be the best thing for the tug end...would you agree?

Zack

The 'center of mass' thing never made sense to me...

Then you were way ahead of me 'cause I was buying it until this year when I started dissecting the Skyting newsletters.

...but I figured Donnell knew what he was talking about being a physicist...

PRE-FREAKING-CISELY. Because he was a physics professor with a PhD after his name everybody and his dog - Yours Truly included - figured he knew what he was talking about and bought into it hook, line, and sinker. And, overgeneralizing a bit, he didn't have a freaking clue what he was talking about, hang gliding didn't have the critical mass of intelligence to catch him, and the damage he did to it is off the scale beyond description.

He's almost the entire reason we're having this little discussion right now. If he had had a different hobby and the Norfolk line of evolution hadn't been hacked off at ground level we'd probably be decades ahead of where we are now.

...and I don't think anyone doubts the benefits of attaching the tow line to the pilot.

But he had to have the tow force split between the pilot and the glider - proportional to the masses of each - which, as we can most easily see by the record of aerotowing, accomplishes NOTHING. If you ever see anyone using a Hewett two to one bridle - rest assured - you can safely assume he doesn't know what he's doing or talking about.

Can you elaborate?

Oh boy, another book... A book I currently have under construction but don't know if I'll ever finish. But briefly, for the time being...

- Throw out pilot control input, which - for a properly trimmed glider towing straight in smooth air is negligible anyway.

- And assume you're truck towing or aerotowing one or two point. If you're towing two point anchor the upper end of the bridle at the carabiner or on the keel at the hang point.

- All the glider knows is the resultant vector of the forces transmitted to/through the hang point. It's feeling down due to the weight of the pilot and forward for aerotowing or some combination of down and forward for truck towing. It thinks that gravity has increased and shifted forward to some degree and trims accordingly.

- It doesn't know anything or give a rat's ass about centers of mass or what the tow tension is or isn't being routed through before it gets to the hang point.

- Route all the tow tension through the pilot or bypass the pilot entirely and connect directly and only to the hang point.

- Suspend the pilot two or a hundred feet below the keel.

- The glider will respond EXACTLY THE SAME to the tow tension or any fluctuation.

- For truck or one point aero towing think of the pilot only as a heavy bulge in the towline.

- And it makes no difference whatsoever at what point on the towline that heavy bulge is located.

Quest weak link quiz...

The implication is that weak links need to break over a fairly small tension range for a tow to be safe. I'd say a rather large range is acceptable as long as it starts at 1 G.

I'd go with starting at 1.4 and throwing in the towel at 2.0.

But saying that:

The strength of the weak link is crucial to a safe tow.

is like saying that a parachute is crucial to a safe flight or an air bag is crucial to a safe drive to the mall. These are good things to have along for the ride but if they come into play the situation has already gone a hundred miles south of "safe". Generally speaking they're never gonna come into play for a halfway competent pilot or driver.

And you REALLY don't want any of these things to kick in when you don't want them to kick in.

All that's crucial to a safe tow is a good pilot, a good driver, and a good bridle/release system.

'Pressure of the towline'...?

Yes, it would inspire more confidence if we understood the meanings of the words we're using, wouldn't it?

Considering we surface tow with higher tensions without handling issues, I don't know what they're talking about.

Well that's reassuring 'cause they obviously don't either.

Maybe they mean that higher tensions will only occur after handling has already been compromised (due to a lockout).

No. Stay with they don't know what they're talking about. Starting with zero and extending up to a couple of Gs you can't make any predictions correlating tension with control. Two may save you, zero may kill you. Flip it and/or take anything in between.

You can be in good shape in a Porsche doing 140 on the interstate in the desert or about to die doing 15 on an icy mountain road.

And please bear in mind that - even in aerotowing - tension can DROP in the course of a lockout.

At any rate, it needs to be strong enough to tolerate a lot more than a 'bit of rough air'.

It bloody well does. I can't tell you what a great feeling it is to be able to plow through a bit of nasty turbulence without having to worry about the fucking Greenspot sending you back to the line.

Since they don't explain why one G is optimum, I can't really say anything here.

One G is a figure Donnell pulled out of a hat in 1980. Everybody always cites it 'cause everybody else always cites it. It's completely without foundation and totally meaningless.

And...

...the total wing load of the glider.

What the hell does that mean?

This is the most incriminating statement of your excerpt. I can't believe how many people just assume that two strands of a line break at twice the rating of the line.

Most people don't assume it - they just trust that the idiots running these flight parks know what they're talking about. I hate admit how many years I bought into this crap 'cause of what I was told on the first weekend of Ridgely's operation in 1999.

(The authors of towing aloft do this almost immediately after stressing the importance of testing weak links to know their breaking strength.)

Towing Aloft is probably the second greatest disaster to ever hit hang gliding - a heavy sprinkling of really good information to get people to drop their guards and a foundation of total crap. Bill Bryden's so far south of clueless it defies description. Just what USHGA really needed for an Accident Review Committee Chairman.

This business about isolating the Fisherman's Knot inside the Double Lark's Head to take it out of the equation... Crap. Doesn't make enough difference to be worth mentioning. I've tested weak links with the Fisherman's Knot on the protruding loop and still had them fail where one of the strands exits the bridle.

But if that's not enough, they completely ignore the fact that the weak link doesn't see the entire line tension since the force is split in the bridle configurations used by 'most flight parks'.

Yeah. Absolutely ASTOUNDING. And what's possibly even more astounding is that no one ever catches that. Even Brian Vant-Hull. Real smart guy, former high school physics teacher, PhD in meteorology... I had to walk him through it after repeated attempts.

I usually don't point that out to people 'cause by doubling BOTH the actual strength of the weak link AND the actual load to which it's subjected the idiot mistakes cancel each other out and your typical hang glider pilot might try to use that as evidence of some level of intelligent life in central Florida.

And, of course, they're dictating use of the weak link for a "typical" 260 pound glider. Like a shoe store from which everyone leaves with Size 8 Mediums.

Again the assumption that breaking strength is the single strand strength multiplied by the number of strands.

Yeah. And I'm sorry but "wing loading" is measured in pounds per square foot and is about the same for any glider.

Can't disagree with any of that.

Yeah - but THEY do. They've just finished telling you that it'll blow before you get out of control and will land your glider at the front of the launch line for you.

Why would you release if there's no problem?

Hell, why take the chance? Just assume there WILL BE a problem and don't launch.
Failing that... Is release a survivable option for addressing the particular problem?

Wallaby's version...

Oh yeah. What a FIELD DAY!

If you fail to maintain the correct tow position (centered, with the wheels of the tug on the horizon), the weak link will break before you can get into too much trouble.

...and...

Remember: it is almost impossible to stall under aerotow. The induced thrust vector makes the glider trim at a higher attitude. It is OK to push way out; you will climb, not stall.

Put those together and watch what happens next. I went to one of those funerals - and then we had to get a new Director for Region 9.

That was originally an article by Austin Scott Collins that appeared in the 1998/02 issue of Hang Gliding magazine - so EVERYBODY could read it. And that was year and a half AFTER Bill Bennett and Mike Del Signore were killed side by side.

Can you explain? I figured towing off a runway would mean less initial resistance and thus less weak link stress. And we're not dragging weak links on the pavement.

Yeah. I'm just scared shitless of landing on any surface that can leave me worse than grass stained. I've seen what happens to people on taxiways when they flare a wee bit late.

At least they don't mandate 130 lb loops for everyone like some places. When I trained there I was told they recommend two loops for heavier pilots.

- OK, some movement in the direction of common sense. But...

- Did they tell you the breaking strength of either of those loops? I kinda doubt it 'cause when I was down there a year and a half ago Matt had me and my test rig:

http://www.flickr.com/photos/aerotowrelease/8317889807/


doing his job for him.

- Did anyone say anything about Gs?

- I tried to get Matt to use Tost weak links. You go to the launch area, check the chart to see what your glider takes, hook up and go. And I had to listen to a couple dozen total bullshit reasons why something like that would only work in Europe. Something to do with the Coriolis effect.

- What's a "heavier pilot"?

- It's bloody irresponsible, dangerous, and negligent to ALLOW anyone to tow with the weak link you were using.

Did they ever let you use your own weak links?

http://www.chgpa.org/forums/viewtopic.php?f=2&t=2467
weak links

Brian Vant-Hull - 2007/07/21 13:00:33 UTC

I don't think there's any argument that weak length strength should scale with total mass (and I'd like to see your contraption for scalable strength weak link), and again you are honest in not having a strong theoretical argument for what the number of g's should be.

I'll be lazy and ask if any of your references give a physical reason for the 0.8 to 2 g range they quote as safe. If not, constructing a reasonable physical argument could be a major contribution. You clearly have the physics down well enough (as good as anyone else in the world) to do so.

I rarely break weak links - probably because I'm light, but I don't feel my safety has been threatened by having a proportionally stronger link than a bigger guy (purely intuitive). Is anyone else worried about my proportionally stronger weak link? Scale everyone's up to match my g ratio and I think we all could be happy?

Note that since I wouldn't have to change anything, I'm automatically happy.

Tad Eareckson - 2007/07/22 12:38:12 UTC

It doesn't matter. Anything to keep you on tow and blow before the glider does. Huge freakin' range.

Well, not really. One real world consideration I haven't mentioned before... You don't want to overload your release mechanisms. I'm recommending that they be able to easily handle one and a half times the maximum tension the weak link will allow so let's get back down to the 0.8 to 2.0 ballpark.

In addition to the references I've cited - FAA, USHGA, and Modern Airmanship - I've come across a passage from Davis citing Donnell Hewett as recommending 0.5, 1.0, and 2.0 Gs for new, experienced, and aerobatic pilots respectively. I'm not sure I buy that 'cause, as has been said ad nauseam, very low Gs are aerobatic enough to slam you into the ground and kill you.

The USHGA and FAA references only state the limit(s), I already quoted everything Modern Airmanship had on the subject - which was both hardly anything and all encompassing, and Towing Aloft views weak links as a secondary release system - the concept through whose heart I'm currently trying to drive a stake.

My take on it is that - I now know what Dragonfly tow tension is and that I was able to drive through a small batch of pretty nasty shit with 1.12 Gs keeping me connected. I'm happy with a bit more than that.

Jim Rooney - 2007/07/22 22:30:28 UTC

Hahahahahahahahaha
Oh that's just rich!
Riiiiiight... it's my attention span at issue here....
and I'm the one that's arrogant!
HAHAHAHAHAHAHAAHAHA

No, I'm not being nice. No, I do not feel the need to be nice. You're trying to convince people to be less safe. I don't want to be on the other end of the rope when someone listening to this drivel smashes in.

I've heard it a million times before from comp pilots insisting on towing with even doubled up weaklinks (some want no weaklink). I tell them the same thing I'm telling you... suck it up. You're not the only one on the line. I didn't ask to be a test pilot. I can live with your inconvenience.

Please tell me again what's wrong with the wheel? Why you keep trying to reinvent it?

Yes, please fall back on the "I'm just saying they could be stronger" bull when you've made it quite clear that anything lower than cable (1200lb) is acceptable.

The simple fact is that you're not improving the system.
You're trying to make it more convenient and trying to convince yourself that you should be towing with a stronger weaklink.

Enjoy your delusion.
Jim

- THOSE assholes "trained" THAT asshole.

- Jim's too stupid to understand:

-- that his employers have for the previous eight years been operating on the Quest theory of Greenspot loops (260 and 520);

-- that Sunny, one of his trainers and employers, had been flying one of my Shear Links since the beginning of that season 'cause he understood that I was right;

-- that the weak link on the glider doesn't strengthen the weak link on the tug;

-- that he tows tandem gliders with double loops anyway - so he won't hafta be a "TEST PILOT";

-- that if the tug pilot is asleep at the switch a glider can kill him just fine with a single loop;

-- how to do the math to calculate the G rating for a particular glider in either two or one point configurations; or even

-- that different people with different gliders have different flying weights and therefore will not all be towing at 1.0 Gs using the same single loop of Greenspot.

- I told Jim he could go fuck himself and towed with my one and a half G Shear Links and equipped a few very grateful local and visiting East Coast Championship pilots.

However...

- Since none of the Ridgely tug jockeys could ever conceive of a situation in which there could be any downside whatsoever to a glider blowing off tow - with or without 250 feet of Spectra towline - they used whatever the hell they felt like on the front end. And that was known to blow before a single loop at the back end.

- And of course there's no REQUIREMENT of a hundred pound safety margin in the USHGA SOPs - just a suggestion.

So, when faced with the choice of having me around trying to bring some level of sanity and safety to their operations or removing me from the conversation, they did what the Capitol Hang Glider Association, Skysailingtowing, Hang Gliding Dot Org, the Paragliding Forum, the Oz Report, and the Houston Hang Gliding & Paragliding Association have done. So they just keep on doing things the way they've always done things 'cause that's the way everybody's always done things - for twenty years.

Just wonderin' if you got to test them in the air.

You can't test weak links in the air - 'cept if they break they're too light. Kinda like asking someone how that High Energy parachute he got last year has been working out for him. Unless he's had something freakishly ugly happen he's gonna tell you he has no idea.

All you can tell about a weak link is how close to spec it blows and whether it fatigues and degrades in response to pushing the limit. And you can't do that in the air and expect to stay healthy over the long term - you're either gonna screw up on the requisite aerobatics or get the crap beaten out of you by the tug pilot after one too many drills.

The tug pilot talked to me about it afterwards and did acknowledge the rowdiness, but I didn't think it was that bad.

Did the tug pilot have a comment on the advisability of towing people with that weak link? (Rhetorical.)

I'd have to have a lot of extras to break in testing to ensure they have a consistent breaking strength (not that I doubt your work, but for something safety-critical I'm not just going to accept your word that they perform as described).

As much as I admire in pilots and scientists the quality of mistrust...

- WEAK LINKS ARE NOT SAFETY-CRITICAL. IN FACT THEY ARE NEITHER SAFETY NOR CRITICAL.

YOU HAVE TO STOP THINKING OF THE WEAK LINK AS SAFETY DEVICE.

http://groups.yahoo.com/group/skysailingtowing/message/4633
Weaklinks and aerotowing (ONLY)

Steve Kroop - 2005/02/10 04:50:59 UTC

Weak links are there to protect the equipment not the glider pilot. Anyone who believes otherwise is setting them selves up for disaster.

Ya' got that? It's not there for YOUR safety and it doesn't give a rat's ass about either you or the glider after it kicks in. Thanks in no small part to all the crap Donnell started publishing thirty years ago, your brain is hardwired WRONG. And it's a total bitch to rewire it to understand and accept Steve's statement. It took me a couple of years and a lot of hard thinking.

There's a kid over on the org - Axel Banchero - who got it like THAT! Blew me away how quickly he got the concept.

You have to totally stop thinking of it as a crutch for a crappy pilot and/or release.

http://www.chgpa.org/forums/viewtopic.php?f=2&t=2467
weak links

Danny Brotto - 2007/05/16 23:15:19 UTC

Weak links are not a secondary release system...

Thinking about a weak link as something that's gonna bail you out of a tight situation is like thinking about what you're gonna do five seconds off the Lookout ramp to climb back into the control frame. It's a waste of the time you should be spending thinking about ways to make sure you NEVER have a need to exercise some such stupid plan.

They are not critical. Remember you've been flying for your entire AT career on 130 pound Greenspot on the ragged edge or sustainability and zilch in the way of low end predictability. You've never had a necessary or desired pop (Correct?) and you've never been in a situation in which your glider was a third of the way to the buckle point. There's a pretty wide range in which to play around between what you've been doing and what you will be.

And don't forget that even if you have no weak link whatsoever it's a pretty good bet that the guy on the other end has something dangerously flimsy 'cause, no matter what's about to happen to the glider, the tug is ALWAYS better off without one hanging on his tail.

- If these were ten dollar a pop Tost inserts you'd probably trust that the manufacturer and the national regulatory agencies knew what they were doing.

- Did you buy an extra cross spar so you could take one out of your Sport and test IT to failure? Or did you trust the certification process?

- It's a pain in the ass to meticulously restitch one of these things.

- I spent a winter developing these things and testing the crap out of them so people like you wouldn't have to and because I'm one of the very few tow equipment people who gives a shit about other people's safety and my reputation. When Steve Wendt half kills one of his customers on shit equipment he just writes up the "accident" report and blames everything on the heavily sedated pilot.

http://www.hanggliding.org/viewtopic.php?t=17404
Aerotow barrel release - straight or curved pin?

Holger Selover-Stephan - 2010/05/28 22:16:33 UTC
Portland, Oregon

I ordered and received a few barrel releases from Blue Sky. They have straight pins, not the curved ones I'm used to. Steve at Blue Sky tells me this:

...they [the curved pins] don't release with as little tension on them as the straight pins. Otherwise, there is no difference. It makes it hard to put just a rope on the barrel end, which encourages a weak link. Just a good idea. That's why we've been shifting that way, as are many other manufacturers of these releases.

Anybody got an opinion on this matter? Thanks!

http://www.chgpa.org/forums/viewtopic.php?f=2&t=3107
I have a tandem rating!!!

Lauren Tjaden - 2008/03/23 22:20:15 UTC

When Jim got me locked out to the right, I couldn't keep the pitch of the glider with one hand for more than a second (the pressure was a zillion pounds, more or less), but the F'ing release slid around when I tried to hit it. The barrel release wouldn't work because we had too much pressure on it.

Anyhow, the tandem can indeed perform big wingovers, as I demonstrated when I finally got separated from the tug.

Yeah, Holger buddy, as a matter of fact I DO have an opinion on this matter...

BULLSHIT.

And how 'bout asking him why he thought that Holly - just before her little trip to shock/trauma - would've had any better luck with hers than Lauren did.

- I can give you a spreadsheet with the results of about 175 Shear Link tests.

I'd be happy with that...am I wrong about their breaking strength being 200 lbs? 200/.6 is only 333.

- Yeah, that's a little light but the tug's probably gonna screw you over and make it academic anyway.

- You can get a TREMENDOUS range of variation on breaking strengths depending upon the type and diameter of the material on which you're installing the Greenspot. I've got a pretty steady progression from 115 pounds on 5/64 to 215 on quarter inch Dacron.

- But I think 200 pounds for a double is pretty good rule of thumb for a minimum and - since for your glider that's just a wee bit over a G - you have a LONG way to go before you start bumping up against the USHGA/FAA limit.

- And while it may not be ideal... Truth is that a lot of the smarter solo guys are doubling them up and not having problems. Even the tandems don't seem to be having problems.

What is the best way to configure two loops, anyway? Can it be done without tying the string directly to the bridle?

Yeah, just make a big loop with the usual Fisherman's Knot, double it, then install it like you would for a single. Double Lark's Head, center the Fisherman's Knot to make it look pretty. Wouldn't hurt to seat it slowly and carefully with an eye on the relative loop sizes to keep things even (and thus evenly loaded).

His weak links are rated for single strand breaking strengths in sewn configurations. I'll still have to test a tied loop's breaking strength (ideally with my own release and bridle).

OK. But I'm finding that you can to pretty well most of the time by making a loop and assigning it the manufacturer's rated breaking strength (N*2/2=N).

A couple of questions...what is your recommendation for the strength of the weak link at a shoulder connection point of a two-point (V) bridle? I would think using the same thing as at the keel would be fine, but I want to be sure.

If you fly with a two point bridle you accept a risk of it not clearing the tow ring. You can minimize that risk with a well designed bridle. I compromised on one design and made a small, easily remedied mistake on another and experienced wraps on both (my only two ever).

Even when releasing at normal tow tension there are such abrupt and pronounced changes in the speeds of the two birds that the jolt is absolutely brutal. If you have a weak link at the bottom end of the bridle 120 percent of the strength of the top one you don't need to be worrying about your secondary releases.

http://www.flickr.com/photos/aerotowrelease/sets/72057594141352219/detail
Aerotow Release System

Check out the:
http://www.flickr.com/photos/aerotowrelease/8313782786

Bridle Link - Installation
...and...
http://www.flickr.com/photos/aerotowrelease/8312900703/

Break Link - Secondary
photos which show arrangements at the Primary/Secondary Bridles junction.

Nevertheless, configure your secondary bridle / release / weak link system as if you were going to tow one point so that you'll be in proper shape if you decide to go that route or that route is decided for you. Same G rating.

And, as I'm sure you know, the same weak link on the end of a one point bridle will give you a somewhat higher G rating than it will on the end of a two - but not enough of a difference to worry about.

What weak link breaking strength do you recommend for the tug end of the line?

I'd like to see it fifty pounds over one and a half times the heaviest solo glider. Guess I could live with 500 pounds.

It seems to me that Tost weak links would be the best thing for the tug end...would you agree?

They'd be fine but, for that end of the towline, since nothing's getting dragged, I'd go with the Shear Links 'cause they're a lot lighter - and might even hold up better.

I haven't seen any more gaggles...

"Kettles" please. A gaggle is a concentration of geese with their wings folded. Was never entirely happy with that term being being applied to gliders.

...of the birds and I don't think I've seen individuals either.

Which lends credence to my call of Broad-Wings.

But when I see hawks now I wonder if they're Broad-Wings.

Don't. The Broad-Wings have pretty much all been in South America since October or so. They tend to migrate en masse fairly early in the season. I called them Broad-Wings 'cause the time and place were about right and you recorded a kettle with just one flavor of bird.

I used to always assume all hawks were Red-Tails.

Bad idea - especially in South Texas.

Sometimes their red tails are really noticeable, but other times they're not.

And until they swap out their first year plumage their red tails are brown.

Think I just discovered the reason Axel was such a quick study on the issue of one-size-fits-all 130 pound Greenspot.

http://www.hanggliding.org/viewtopic.php?t=5089
The Good-The Bad-The Ugly....

Socrates Zayas (DocSoc) - 2008/01/14 05:22:38 UTC
Fort Lauderdale

Florida Ridge Flight Park

Yesterday was a very emotional day for me and my household. My better half did something that I really didn't expect from a medical student/mother/busy no time to waste...

This would be the final flight of the day, just in front of her was a student tandem flight about to launch, so I was headed back to the car to finalize the packing up when I heard the tug make the familiar sound it does when a weak link breaks.

So why is this such a familiar sound? Are the tug drivers, pilots, and equipment so crappy that flights are so totally out of control as to require pops as routine events?

I looked back to see the tug circle around and saw a wing turned up in a WHACK configuration. I was like "wow". Then I noticed it wasn't the tandem but Sherb-Air's Falcon 170.

When I got there her nose was lacerated and her lip was bleeding (yeah, she had a full face helmet) and the dolly's left wheel was missing.

The radiography showed acute multiple fractures around the top and head of the humerus. Her nose didn't break but she may have hairline fractures to the septum. She had a hard time remembering the date, day, names of her kids, number of kids, and other basic things...

The dolly had hit a huge hole and she went left shoulder into the ground at 25+ mph. The weak link did its job and may have saved her life.

Bullshit.
- The job of the weak link is:
-- NOT to:
--- save the pilot's life.
--- blow in the course of a blown launch on a dangerous runway nobody's bothered to check since last weekend.
-- ONLY to protect the glider from being subjected to excessive positive flight loading and ONLY when the tow force is being routed to the hang point.
- The trauma to Sher was virtually entirely a result of a sudden sudden stop.
- The weak link - in this situation - was what permitted the sudden stop.
- In this situation if there hadn't been a weak link at all then something else would have been the weak link the instant that glider assumed WHACK configuration and the results would've been IDENTICAL.
- Pilots who are dragged in the course of blown launches always come out smelling like roses - relative to what happened to Sher.

http://www.hanggliding.org/viewtopic.php?t=6911
Sunday flying at Florida ridge. -

Axel Banchero - 2008/05/19 00:53:19 UTC
Miami Beach

Today I flew for the first time at the Florida Ridge.

Being a new pilot, I had to take more tandem flights because they will not let you fly until you show the staff you know how.

I wasn't expecting this because tandems mean more empty in your wallet, but then I understood that if you are new to a flying site, you must show your skills first for security reasons.

Bullshit. The only thing you should've had to take out of your wallet was your rating card - which had an AT signoff from Wallaby. That's the purpose of the rating card. You got screwed.

Then Doc Soc took off. His weak link broke.

He took off again, and the weak link snapped one more time. He got an incident after this.

For a grand total of THREE incidents. Two totally needless weak link failures, the second of which precipitated a cartwheel crash and a concussion.

Nope - just one. Forgot that in hang gliding frequent power failure on takeoff is a GOOD thing - a sure sign of a safe, conservative operation. I was thinking of REAL aviation. Sorry.

Rafael Castro - 2008/05/19 15:46:04 UTC
Florida

I can attest to the winds both Saturday and Sunday at the Ridge. First time I have towed in such strong/gusty winds especially Sunday morning.

New Experiences:

-Had a weak link break just after leaving the cart at about forty feet.

GREAT! Maybe next time you can make it all the way up to FIFTY feet! So how badly out of control were you when this thing popped and why hadn't you released long before things got that ugly?

-Learned to be careful turning back towards the wind on landing since the Falcon has such low penetration, plus you lose major altitude on a turn back into high winds (hindsight).

No, actually you lose exactly the same altitude you do in a dead calm. Who's teaching you this crap?

Socrates Zayas - 2008/05/21 23:53:23 UTC

At 10:30 Eric came out to tow me to the southwest with the wind SSW. That put me right over the right side of the hangar and parking lot. This is a short section of the field but not all that bad as long as you have an exit strategy. I decided I would NOT continue to double the weak link after seeing my wife eat it a few months ago.

SMART MOVE! If you fly a weak link that can't support you on tow nobody'll hafta check the runway for armadillo holes once a week and if you hit one you'll only get fucked over as bad as Sher - 'stead of twice as bad.

It broke at about ten seconds after hitting 800 fpm lift off the LZ!!! Hell of a cycle. The tug and I went up like rockets. But instantly at 200 feet it wasn't all that bad. I flew the U2 into a nice foot landing right by the cars.

You and the tug were going UP like ROCKETS?!!! That must've been TERRIFYING! I can't begin to imagine. Thank GOD your weak link blew. And thank Him also for allowing you a nice foot landing right by the cars between the cycles during which that stuff was breaking off.

Second try:

This time the wind seemed H&V (heavy and variable) and we decided to take off to the southeast. But this gave us a short runway and an orange orchard in front of us and we decided to take off with a bit more speed.

The cycle was nice, nothing out of the ordinary, but just as the tug flew over the fence line of the orchard the weak link broke. It was as if it didn't even break - Eric and I both thought it was a release malfunction. But Axo, Ralph, and I found the release and confirmed otherwise.

I was flying nice with good speed and climbing. I thought "Shit. It broke again. Damn, I don't want to land between those trees, they don't even have the keys to the gate anymore." So I turned to the right cross wind toward the RVs and campfire spot. Unfortunately just to the right of those things are 75-100 foot trees and I was just not anticipating the rotor.

My left wing was raised to about 80 degrees and I was sent into a right slip at 40-50 feet.

Axel Banchero - 2008/05/22 04:19:39 UTC

Doc's body wasn't moving and we were shitting our pants until he started talking confused. The first thing I saw was his eye bleeding and swollen the size of an 8 ball. There was sand and dirt inside. Looked like he lost it at first until he could open it a little bit.

Bill Jacques - 2008/05/22 12:53:45 UTC
Boca Raton

I don't think going straight was an option for Doc after the break (as I recall no low altitude reachable bailout as there's a shitload of trees over there).

I guess one of the things that we can all learn from this experience is to imagine what we should do BEFORE it happens. Based on the conditions that everyone reported here, another weak link break could have been expected.

Were the weak links breaking because of the conditions? Has anybody in the entire history of 130 pound Greenspot ever gone up in ANY conditions - or lack thereof - NOT expecting another weak link break?

Jack Axaopoulos - 2008/05/22 15:07:45 UTC

This is the kind of stuff you gotta think of BEFORE you start your tow. Like Doc said, FLIGHT PLAN. I think of it more as a "WORSE CASE PLAN"

The wind was described as heavy and variable and passing through 75-100 foot tree's a the end of the field.

Now.... youre planning to tow straight towards those trees and clear them.

The "WORST CASE PLAN" would make me ask questions like:

1) What would I do if the wink link broke while I was near those trees? Would I have the altitude to turn and glide away from the rotor while still above it?

2) What would happen if I got towed right over those tree's, and the week link broke after I was deep over the trees? Would I be squeaking it back in and diving into deep rotor to land IN A TAIL WIND ???

Landing cross wind, in rotor coming through 75ft+ tree's in a scary situation, and depending on the wind/gust strength, no amount of speed could save you.

I'm part of the wuss party. If conditions make me nervous, id much rather sit out and fly another day. You may end up fine, but if you plan on rolling the dice many times in this sport, be sure to only roll them when the odds are in your favor.

What would happen if hang glider pilots were smart enough to write at a second grade level, understand punctuation, capitalization, didn't misspell "weak" two different ways in the space of two consecutive sentences? The possibilities boggle the mind.

Sheryl Zayas (sherb-Air) - 2008/05/22 16:46:25 UTC

Yes, Doc's crash was acrobatically superior to mine, however his injuries are MIRACULOUSLY benign. (Knock knock knock on wood...) No broken bones, which has amazed several doctors so far. A little brain swelling; but he definitely has the thicker skull of the two of us. And a black eye with a laceration that is so small he probably will exaggerate the number of stitches. I have to admit, the man was made to take a hit. I am NOT complaining.

Socrates Zayas - 2008/05/22 23:25:22 UTC

I've had hundreds of good tows and broken tows. I first soloed at LMFP in 2007! I trained there for a week of hell from the first to second week of May and began my trek around the US in June... Ellenville, Pennsylvania, Wallaby, FRFP, HG Chicago, and Elsinore.

Does "broken tow" mean what I think it does? What's your batting average?

Rafael Castro - 2008/05/23 19:52:57 UTC

We all watched his weak-link break, it was non-event something that happens all the time, the tug and he were already about 150-200 feet AGL - way above the citrus orchard.

Bill Jacques - 2008/05/23 20:51:33 UTC

If nothing else, an earlier weak link break(s) and pilots being grounded could have been indicators that conditions were unsafe.

Did ANY of the reported weak link breaks occur with the glider the slightest bit out of position or anything much beyond normal tow tension? Were ANY of the breaks necessary or desired? If so, how come nobody - at either end of the line - was hitting - or attempting to hit a release?

Was anybody locking out? Was anybody even reporting the slightest problem maintaining position behind the tug?

The winds were maxing at around 15 - which, in the mountains, is child's play - and he HAD a better bailout option which he passed up because the retrieval might have been inconvenient.

So didn't the Greenspot itself dwarf the other potential hazards of the day?

Rafael Castro - 2008/05/23 21:15:21 UTC

I flew just before Doc's incident and the tow up was not a bronco ride like midday stuff.

Bill Jacques - 2008/05/24 00:28:41 UTC

Regardless of what people remember or how bad the rotor was or wasn't, there is no doubt that the takeoff pattern was relatively short and the bailout had to be back around some trees. Combine that with two weak link breaks, the fact that some pilots were grounded for adverse conditions, and it's apparent conditions were not the greatest...

It's usually not what's "high up" in the sky that kills you. It's the takeoff or the landing. Anything that interferes with those critical events is important. A 15 mph wind, a relatively short runway, with trees causing a potential rotor at the end, and little "bail out" potential.. all would interfere with a safe takeoff.

Hey Bill, how 'bout the weak link breaks themselves? How 'bout weak links that blow under normal tow tension with absolutely nothing going on? Might something like that conceivably be added to the list of things that might interfere with the critical event of takeoff where the glider's low and extremely vulnerable?

Nah. Just kidding. Carry on with your discussion.

There were 73 posts in that DocSoc postmortem and NOT ONCE did ANYONE whisper anything questioning the sanctity of 130 pound Greenspot. The depth of stupidity of this sport is completely beyond comprehension.

http://www.hanggliding.org/viewtopic.php?t=12403
weak link table

Axel Banchero - 2009/06/10 19:30:18 UTC

I assume they know what they are doing if they have been in the business for around thirty years.

http://www.hanggliding.org/viewtopic.php?t=12536
standard operating procedures

Axel Banchero - 2009/06/18 15:42:14 UTC

Tad... Thanks for the links to the Dynamic Flight reads on lockouts and weaklinks. I must confess I was one of those expecting the weak link to break in case of an ugly lookout before reading that.

'Cause that was the crap you were being fed during your "training" at Wallaby?

The info on that site is very clear and makes a lot of sense.

For me it also makes sense now.

I have had one weak link break during launch and I feel "lucky" everything went well and just landed a bit hard on the wheels.

But I also saw a world class pilot having exactly the same problem and breaking the link at the same altitude. But he broke the downtubes on his Litespeed and looked to be in pain in one of his wrists. He was fine though.

I saw more weak links break at low altitude and it is always a few seconds of anguish and uncertainty about what's gonna happen to the pilot.

I would like to improve my weak link setup so I am better than now at avoiding a low altitude break during launch and I want to start releasing sooner when I get into a lockout position as now I know the weak link won't do shit to save me.

By now, I haven't seen any of those Tost or any other setups in a hang glider yet. I would be open to use a system like that if the park owners also approve it after learning the benefits and increased security.

"Park owners" and "learning" in the very same sentence. How charmingly naive.

http://www.hanggliding.org/viewtopic.php?t=14230
pro tow set-up

Jack Axaopoulos - 2009/11/09 14:44:23 UTC

Tad, your continual bashing in general and bashing of HG schools has gotten really old. AT parks have solid safety records, so what you say and reality seem to be quite far apart.

You dominate the ignore report here.

http://www.hanggliding.org/ignorereport.php

Ever ask yourself why???

ONLY about three dozen hang gliding people too stupid to be able to not read something without a digital tool? On a forum you "moderate"?

No. I just look at the numbers on stuff like my "Aerotow release options?" thread. It's picked up over six thousand hits since you locked it down on 2009/07/04 'cause people started agreeing with me and taking on your moronic position.

You do nothing but bring negativity here. My finger is on the ban button. This is your last warning.

If you continue rubbing everyone the wrong way with your harsh, know it all tone, you are out of here.

http://www.hanggliding.org/viewtopic.php?t=14312
Tow Park accidents

Adi Branch - 2009/11/10 20:50:50 UTC
UK

For what it's worth, I think Tad spoke a lot of sense.

http://www.hanggliding.org/viewtopic.php?t=17092
Crash at Questair

Alfie Norks - 2010/06/03 12:24:40 UTC
Brazil

Speedy recovery to the pilot in question.
It could have been worse. It could have happened at...the other place (but nothing happens there. ) Good luck if it does. No 911 calls allowed. My friend was lucky, the nurse on hand convinced the owner not to move him, this after he snatched and threw her phone away. She was trying to dial 911. My friend suffered lower back injury.

http://www.hanggliding.org/viewtopic.php?t=14312
Tow Park accidents

Jack Axaopoulos - 2009/11/10 13:36:53 UTC

I still dont know if I buy into the stronger weak link hypothesis.
Ive broken weak links on purpose at altitude by banking up and pushing out abruptly. That is a mechanism I want to keep, not give up.
The downside is, you will get more weak link breaks while near the ground, early in a tow, or whatever.
BUT... you should be maintaining proper airspeed anyway, then its not an issue.

Yeah. Right.

Tad,

Thanks for the 'center of mass' debunktion. I've always felt the glider is easier to control (more stable) when towing two-point, but I suspect that's just because it dampens pilot input or something. I've never used a Skyting bridle but I've heard they 'tow nicely', but again, I suspect it's just because they provide a more optimal amount of dampening than a 1:1 bridle.

So if you were towing two-point with the top bridle attachment at the carabiner or hang point and you released from the bottom and had a wrap, I take it you wouldn't be at any more risk of tucking than before you released? Not that you'd be in a particularly good situation then...

Tad Eareckson wrote:Starting with zero and extending up to a couple of Gs you can't make any predictions correlating tension with control.

While I know that it's possible to experience a lockout without tensions being high, I'm not sure about the reverse. Is it possible to experience, say, a 1.5 G line tension on an aerotow in a situation that's not a lockout?

Tad Eareckson wrote:Did they tell you the breaking strength of either of those loops?

Nope.

Tad Eareckson wrote:Did anyone say anything about Gs?

Nope.

Tad Eareckson wrote:What's a "heavier pilot"?

Someone frequently breaking single 130 lb loops.

Tad Eareckson wrote:You can't test weak links in the air...

While I mostly agree with you, I'd still feel better using a weak link type/configuration that's been used in flight. A weak link might demonstrate a consistent breaking strength on the ground but might have, for example, a high probability of causing a wrap when it goes through the tow ring. It's unexpected problems related to the mass and volume of a new weak link type, not its breaking characteristics (assuming it's tested), that concern me. Also, it's impossible to simulate on the ground the exact tension fluctuations a weak link sees in flight. Maybe rapid tension changes stress a link more than a gradual buildup. It's good to know that a weak link that's not supposed to degrade has survived a large number of flights (especially if it's breaking strength is then measured to match its rating).

Tad Eareckson wrote:YOU HAVE TO STOP THINKING OF THE WEAK LINK AS SAFETY DEVICE.

You compared them to airbags and parachutes...are they not safety devices? Yes, the weak link is there to protect the equipment, but does protecting the equipment not protect the pilot? To me, something that's designed to prevent a structural failure is a safety device.

But what I really meant with regards to them being safety-critical is that if they break prematurely they could be a safety hazard. I think you'd agree with that.

Tad Eareckson wrote:You have to totally stop thinking of it as a crutch for a crappy pilot and/or release.

I don't think I said anything in that post to indicate I did. I'm on board with you on this.

Tad Eareckson wrote:If these were ten dollar a pop Tost inserts you'd probably trust that the manufacturer and the national regulatory agencies knew what they were doing.

I'd actually still test at least one Tost. But that's a bit different. Those things are machined and mass produced. Shear Links are hand-made and from your description of making them it sounds like breaking strength can suffer if they're not stitched properly.

Tad Eareckson wrote:Did you buy an extra cross spar so you could take one out of your Sport and test IT to failure?

Apples and oranges. Weak links are called 'weak' links for a reason. They're designed to break (at a point)...it's their purpose. Cross spars are designed NOT to break.

Tad Eareckson wrote:I can give you a spreadsheet with the results of about 175 Shear Link tests.

Wow...you are obsessive (which in this case is a very good thing). Still, forgive me if I'd want to test at least one. But again, I want to tow two-point, so this is kinda moot.

Tad Eareckson wrote:Yeah, just make a big loop with the usual Fisherman's Knot, double it...

By 'double it', do you mean put a twist in the loop (resulting in a figure 8) and fold it in half? Sorry, I'm kinda dense about stuff like this.

Tad Eareckson wrote:You can minimize that risk [wraps] with a well designed bridle.

I thought bridles were pretty straightforward. What characteristics minimize the risk of wraps?

I think I experienced a bridle wrap once (long time ago at Lookout). I had a weak link break but upon landing found that the weak link that broke was at my shoulder. I thought that was odd being that that weak link was only seeing around half the tension of the top one. But then I found that my top bridle was completely missing even though the release was closed. Never did find it. At the time I had no idea what happened. I'm now thinking the top weak link broke, the bridle wrapped, and the bottom weak link broke immediately after. It all happened so fast I didn't realize what happened.

Tad Eareckson wrote:Even when releasing at normal tow tension there are such abrupt and pronounced changes in the speeds of the two birds that the jolt is absolutely brutal. If you have a weak link at the bottom end of the bridle 120 percent of the strength of the top one you don't need to be worrying about your secondary releases.

So you're saying that the shoulder weak link will always break in the event of a wrap? I would think this would also apply then if the wrap occurs after a release from the bottom instead of the top, right?

Tad Eareckson wrote:Check out the...photos which show arrangements at the Primary/Secondary Bridles junction.

Some terminology first...is a 'secondary bridle' the one attached to the pilot's shoulders, with the 'primary bridle' being attached to the keel? If I'm following the pictures, the shoulder bridle runs through a metal ring at the end of the top bridle, correct?

You seem to very knowledgeable about birds. Thanks for the info.

Tad Eareckson wrote:

Zack C wrote:I used to always assume all hawks were Red-Tails.

Bad idea - especially in South Texas.

Besides migrating Broad-Wings, what other hawks (buzzards?) appear in this area? From what I've read about 'true hawks' it sounds like they like to stick to wooded areas...do they ever thermal in the open? Also, Red-Tails have a very distinct call...do any other species sound similar?

Zack

Thanks for the 'center of mass' debunktion. I've always felt the glider is easier to control (more stable) when towing two-point, but I suspect that's just because it dampens pilot input or something. I've never used a Skyting bridle but I've heard they 'tow nicely', but again, I suspect it's just because they provide a more optimal amount of dampening than a 1:1 bridle.

What I didn't cover in the debunktion was pilot control issues.

In truck towing you're making the pilot heavier and shifting apparent gravity forward and the glider trims accordingly. The towline angle (ignoring sag as a consequence of weight and wind resistance) remains constant - pulling forward and down - and the pilot is positioned normally/properly with respect to the control frame. It takes more muscle per inch of control input but you're getting more authority. Pretty simple.

It aerotowing the towline angle is (hopefully) forward constantly. No matter how you distribute - or don't distribute - the tension at any point(s) between the pilot and hang point (at the keel) the glider will respond exactly the same to tow tension and fluctuation. BUT...

If you go all to a point about halfway up the suspension you're close enough to the centers of mass (lower) and drag (higher) that the pilot's gonna stay in good position in relation to the control frame. This is how Bill Brooks and Howard Edwards addressed the issue - independently in England - in maybe early 1981. The Brooks Bridle was freaking historic and is still better than a lot of the deadly crap flying today - there'd be a lot more AT pilots still around today if everyone were using it.

Donnell's two to one Skyting Bridle also accomplished the same thing - with a bunch of deadly Rube Goldberg crap all over the place. Under his "theory" you had to distribute the tow tension to the centers of mass of the pilot and glider in proportion to the masses - or you would be killed instantly by a violent pitch up or down or lockout. But the effect was the same as the infinitely superior Brooks Bridle - the thrust line went through a point about a third of the way up the suspension.

If you go all to the hang point the glider tows the same but you're gonna be left behind - the basetube is gonna be way in front of you.

If you go all to the pilot you're gonna leave the glider behind - the basetube is gonna trim way back and if you stuff it you won't really have stuffed it. Normally this isn't a big issue but if you're going up like a rocket and the tug isn't - à la Pagen... Also, you weigh more than usual and the glider's gonna be more responsive to control input - à la Holly Korzilius.

But if you tow two point you're in about the right position with respect to the control frame and the handling will be similar to what it is in free flight. And since tugs like to fly faster than gliders you can make the tow easier by moving the upper anchor point fore on the keel - which is analogous to moving your hang point forward - for a faster trim speed. The higher the lift to drag ratio of your glider the less of an issue this is.

So if you were towing two-point with the top bridle attachment at the carabiner or hang point and you released from the bottom and had a wrap, I take it you wouldn't be at any more risk of tucking than before you released?

Correct.

Not that you'd be in a particularly good situation then...

Correct. Assuming you released from the bottom, not because you are a complete idiot but only a partial idiot and flew with a primary release which doesn't work, you would then be dependent upon the kindness of strangers and the absence of things that could snag your towline on the ground.

Is it possible to experience, say, a 1.5 G line tension on an aerotow in a situation that's not a lockout?

With the weak links the bozos are using at the front end? No. Otherwise, fer sure. If Bill Bennett and Mike Del Signore - 1996/07/25 - could've been hit with and held a couple of Gs even pretty late in the game they'd have had an opportunity to learn from a lot of mistakes.

Nope.
Nope.

Someone frequently breaking single 130 lb loops.

Yep. Great way to run an airline.

While I mostly agree with you, I'd still feel better using a weak link type/configuration that's been used in flight.

You've BEEN using a weak link type/configuration that's been extensively used in flight. How's that been working out?

It's unexpected problems related to the mass and volume of a new weak link type, not its breaking characteristics (assuming it's tested), that concern me.

- Those would not be unexpected problems. Those would be obvious and predictable problems.
- With a secondary weak link and/or a secondary release trigger in your teeth those aren't particularly serious problems either.

Maybe rapid tension changes stress a link more than a gradual buildup.

- If that were the case sailboat people would have big problems.

- Everybody's flying with Greenspot right on the edge to begin with. We're not seeing a correlation.

- Line fails when the fibers on the outside of a bend are stressed more than the fibers on the inside.

- The fibers on the outside of a bend of nylon dental floss don't have to travel much farther than the ones on the inside - and nylon stretches real well.

- If you really wanna get a line to fail take it up to about four fifths of its rated breaking strength - with the knot figured in - a few times.

- I've taken my Shear Links up very close to their predicted/rated breaking strengths multiple times, tested them to failure, and had them do what they're supposed to.

- I've measured normal tow tension at about 125 pounds. For your glider 1.5 Gs - max loaded - is 434 pounds. Your weak link is never gonna be sweating things anyway.

It's good to know that a weak link that's not supposed to degrade has survived a large number of flights (especially if its breaking strength is then measured to match its rating).

They have. There've been a few people flying them a lot. They're not breaking in flight. I haven't tested them after a lot of use but they're not getting any stronger and our experience with the Greenspot tells us we can almost always get away with weak links on the ragged edge.

You compared them to airbags and parachutes...are they not safety devices?

Nah, they're last ditch, hail Mary, EMERGENCY devices. They're you've-already-screwed-the-pooch and you'll-be-lucky-to-survive-this-one POST safety devices.

Yes, the weak link is there to protect the equipment, but does protecting the equipment not protect the pilot?

Not necessarily. It may not protect the equipment from structural failure under positive loading before it and you are in lotsa little pieces on the runway. And just 'cause the glider has been saved from structural failure under positive loading at considerable altitude doesn't mean it's gonna start flying again anytime soon. It also doesn't mean it won't whipstall, tuck, and break negative. This is the point Steve Kroop is trying to get across.

You could be in a situation in which you'd rather take your chances with the POSSIBILITY of structural failure over the CERTAINTY of what's gonna happen when you lose the tow. This is all about tradeoffs and there's no one right answer until you know what the situation is. If you're trying to punch back out towards the valley in a strong wind with nothing but injun country behind you, you probably wanna be flying a T2. If you're trying to park in a tight field a Falcon (or paraglider) is your better bet.

To me, something that's designed to prevent a structural failure is a safety device.

To me it's a necessary evil. Try this on...

You CAN break a glider under positive loading in free flight - there's no weak link to protect you from doing that. There's not a much better excuse for breaking one on tow. If you need a weak link to keep that from happening you probably shouldn't be towing - or flying. There's virtually no excuse for needing a weak link to do your job for you.

I don't think I said anything in that post to indicate I did. I'm on board with you on this.

OK, great. But I know how difficult it is to rewire on this issue. After over forty years I went qwerty to Dvorak in a matter of weeks but after something around twenty-five it took me two years to retool from thinking of the weak link as an emergency release.

Shear Links are hand-made and from your description of making them it sounds like breaking strength can suffer if they're not stitched properly.

- Yeah, they can, but if you shoot for 1.5 you're not gonna get below 1.2 even if you do a crappy job. And a solid 1.2 is still pretty reasonable figure. You shoot for the bull's-eye but the target's pretty big.

- I'd hazard a guess that the Tosts might run into more of a problem due to metal fatigue (but you can and should back them up).

- Your real big problem is trying to get the tug to do its job so this other stuff doesn't really matter all that much.

Apples and oranges.

Yeah, I knew that wasn't the greatest of analogies - but weak link analogies are real hard to do. Nevertheless, when you clip into a brand new glider you're trusting your life to the integrity of a lot of tubes, bolts, wires, and threads and the word of the people who make them and put them together. And it would be virtually impossible for you to verify everything on the ground and very dangerous to try to do it in the air.

By 'double it', do you mean put a twist in the loop (resulting in a figure 8) and fold it in half?

Exactly.

I thought bridles were pretty straightforward. What characteristics minimize the risk of wraps?

As you know, you don't want it getting thicker, heavier, stiffer, or irregular as you approach the ends.

I'm now thinking the top weak link broke, the bridle wrapped, and the bottom weak link broke immediately after.

That's exactly what happened - and why bridle wraps tend not to be the BFDs the Skyting disciples make them out to be.

So you're saying that the shoulder weak link will always break in the event of a wrap?

Probably. But you can move your odds way up with a weak link at the bottom end of the primary bridle just safely stronger than the one at the top.

I would think this would also apply then if the wrap occurs after a release from the bottom instead of the top, right?

http://ozreport.com/forum/viewtopic.php?t=11591
Where to put the weaklink - the HGFA rules

Rohan Holtkamp - 2008/04/21

Once again history has shown us that this thread-through system can hook up and the hang glider remains being towed by the keel only, with the bridle well out of reach of even a hook knife. I know of just one pilot to survive this type of hook-up, took him some twelve months to walk again though.

Don't count on it. When the top goes there's a massive pilot down there whose inertia is gonna keep him from accelerating very fast. When the bottom goes there's a very light wing which is gonna have much less objection to the proposition.

Some terminology first...

Yeah. Primary, two point. The first one you blow. Secondary, one point. The one you may have to let go if the primary fails to clear the tow ring.

If I'm following the pictures, the shoulder bridle runs through a metal ring at the end of the top bridle, correct?

Right. A sailmaker's thimble. Something hang glider people would use if they had one percent of the common sense sailors do.

You seem to very knowledgeable about birds. Thanks for the info.

I pale in comparison to John and Dale. Make them take you to their place and show you all their buddies next trip.

Besides migrating Broad-Wings, what other hawks (buzzards?) appear in this area?

Gawd, what other hawks and buzzards DON'T appear in that area?

From what I've read about 'true hawks' it sounds like they like to stick to wooded areas...do they ever thermal in the open?

They generally like to HUNT in wooded and scrubby areas - but they all go places. And they all go places the same way we do - 'cept way better.

Also, Red-Tails have a very distinct call...do any other species sound similar?

In the movies and on television ALL species of raptors sound EXACTLY like Red-Tails - particularly Turkey Vultures - particularly when someone is near death from thirst underneath a blazing sun in the desert three to five minutes before rescue. I even heard a gull that sounded like one a couple of months ago (We Shall Remain - PBS). Out in the field however, it's a lot easier to tell what's around with your eyes closed.

---
1996/07/25 - Bill Bennett / Mike Del Signore

Dave Farkas - 1996/08/02

I was checking the glider in the mirror as we climbed out and it appeared a little low, but not way off. Mike seemed pushed out, but not all the way. The glider never dipped below my view in the mirror and seemed to stay about in the same place and stable. I can't remember for certain, but I may have eased the bar out slightly to try to get a little better rate of climb and get away from the ground a little quicker.

Luen Miller - 1996/10

The glider hit the ground hard at a steep angle, left wing first. One pilot was apparently killed on impact, the other died a short time later.

---

Hang Gliding - 1998/02

The Wallaby Ranch Aerotowing Primer for Experienced Pilots

by Austin Scott Collins, USHGA Aerotow Pilot. Based on instructional information developed by David Glover and Malcolm Jones, USHGA Advanced Tandem Instructors.

Welcome to Wallaby Ranch, the first and largest Aerotow Hang Gliding Flight Park in the World! We're the aerotowing (or "AT") professionals; no-one knows AT like we do; it's all we do, and we do it everyday, year-round. This primer will teach you the basics of AT theory and technique. Our instructors have fine-tuned this system over the course of many years, while teaching thousands of people how to aerotow hang gliders. Careful study of this material will make your transition to AT faster, easier, less expensive, and safer. When done properly, AT is your gateway to longer, higher, hassle-free flights, and more airtime with less effort than ever before.

Equipment

A weak link connects the V-pull to the release, providing a safe limit on the tow force. If you fail to maintain the correct tow position (centered, with the wheels of the tug on the horizon), the weak link will break before you can get into too much trouble.

Flying Under Tow

The three most common mistakes for pilots new to aerotowing are:

1. The pilot comes off the cart and rises too quickly above the tug, breaking the weak link.

2. The pilot fails to anticipate the tug's quick climb-out after launch, gets low, and then doesn't push out far enough to climb up. Remember: it is almost impossible to stall under aerotow. The induced thrust vector makes the glider trim at a higher attitude. It is OK to push way out; you will climb, not stall.

3. Over-controlling and over-correcting. Make only small, relaxed, conservative movements and corrections. Should you find yourself low behind the tug, you may need to actually push out on the control bar forcefully, resulting in a "past normal" bar position, that in non-towing situations would lead to a stall. However, because of the "pull" of the tow line, this action will result in a CLIMB, and not a stall. Stay with the tug using pitch input. If you are low, PUSH OUT!

---
1998/10/25 - Jamie Alexander / Frank Spears

Bill Bryden - 1991/01

At a point just before things went bad, the tug climbed and the glider got low behind the tug.

One pilot was apparently killed on impact, the other died a short time later.

---
2005/09/03 - Arlan Birkett / Jeremiah Thompson

http://www.chgpa.org/forums/viewtopic.php?f=2&t=988
Another HG tragedy

Paul Tjaden - 2005/09/05 23:55:24 UTC

One witness said the glider fluttered and spun to the ground from two hundred feet up like a wounded bird... The student was said to be fairly experienced and just about ready for solo flight.

http://ozreport.com/forum/viewtopic.php?t=865
Tandem pilot and passenger death

Mike Van Kuiken - 2005/10/10 18:44:27 UTC

I watched the glider come almost straight down from about 250 feet. I saw that Jeremiah was doing the takeoff right from the start and I watched him get pretty low on the tow as the tug crossed the road at the end of the runway.

Mike Van Kuiken - 2005/10/13 19:47:26 UTC

The weak link broke from the tow plane side. The towline was found underneath the wreck, and attached to the glider by the weaklink. The glider basically fell on the towline.

Chicago Sun-Times - 2005/10/06

"They're 200 feet in the air, and while normally they would glide to the ground, this hang glider nose-dived to the ground," attorney Matthew Rundio said. "We need to find out why that happened."

---
http://www.ushpa.aero/advisory.asp?id=1
USHPA - Safety Advisory #1

USHGA - 2006/03/15

Safety Notice

HG Tandem Aerotow Operations

It was noticed over a number of years there have been a number of fatalities to participants in hang glider aerotow instruction. The president of the USHPA, therefore, formed an Ad Hoc Joint Committee of the chairs of Safety and Training, Tandem and Towing to investigate this, appointing the Chair of Safety and Training to preside. Tandem instructors Matt Taber and David Glover were invited to participate.

This committee reviewed a number of possible causes for aerotow tandem fatalities. One particular possible cause stood out as predominate. This was the common belief that when a glider gets low on tow the pilot can safely push out and let the glider climb up to the level of the tow plane safely because the glider will not stall under tow.

This issue is so important that this committee and the towing committee have recommended that the following message be sent to all aerotow pilots and all Aero-Tug pilots with a particular emphasis to aerotow tandem pilots.

Experiences in hang glider tandem flight using aero-tow launch along with analysis of accidents and incidents that have occurred during such flight strongly suggest, for safety reasons, the following cautions be observed.

If the pilot of the tandem glider finds that he/she is too low behind the tug and slow enough that the glider will not climb without pushing out pass trim, then the pilot should pull in and release rather than trying to push out and climb to the tug altitude. Though pushing out to climb to the tug altitude has been a common practice usually accomplished without incident, there is a deep underlying danger in doing this. Should the tandem glider become unattached from the tug during this maneuver, the nose high attitude of the tandem glider attained while doing this will cause a very abrupt stall which will result in a much greater altitude loss than one would expect (possibly more than 750 feet). The most extreme cases may result in structural failure of the glider.

Towing tandems requires extra awareness on the part of the tug pilots, particularly in the early part of the tow to help the tandem pilot avoid the development of critical situations. Prior to the start of the tow, proper tow speeds based on the gross weight of the tandem glider should be determined. Greater total weight will require correspondingly higher tow speeds. It is CRITICAL to understand that the towed hang glider is at risk when the tow is slow and the glider is low. When towing a tandem glider, the tug pilot should fly the appropriate airspeed to keep the tandem glider in the proper position and if there is any doubt the tug pilot should fly slightly faster and avoid flying slightly slow. The tug pilot should avoid pulling up abruptly and leaving the tandem glider low. If the glider is low on tow, the tug pilot should attempt to speed up and to descend to the altitude of the towed glider, releasing the tow rope only as a last resort.

These points are crucial to the safety of aerotow tandem flight. However, this letter is addressed to all aerotow rated pilots and tug pilots, not just to tandem pilots. This is because in consulting with pilots about this issue, we found that this problem is exhibited under the same circumstances with solo gliders as well. Because of the lighter wing loading of the solo gliders, the reaction of a solo glider is not as severe, but can still be violent.

To insure that all AT rated tandem pilots are notified, we are asking that the AT-rated tandem pilots sign on to the USHPA web site (http://www.ushga.org) and fill out a form that states that they have read and understand the safety notice. If you are an AT-rated tandem pilot and do not have computer access (ie. no email address) you will be sent the form to fill out and sign, and a USHPA addressed, stamped envelope. Understand that we are not asking if you agree with the safety notice, but that you have read it and understand what it says. You will need to do this in order to have your tandem rating renewed.

Flying with a tandem passenger is a special privilege which the FAA allows us to grant to qualified pilots. These pilots are supposed to be highly skilled. We expect tandem flights to be safer than solo flights, not more dangerous. Safety records do not currently seem to support this expectation. We expect tandem flights under the rules of the USHPA to be conducted in such a way that this expectation is realized.

David G. Broyles, Chairman of Safety and Training Committee
Steve Kroop, Chairman of Tow Committee
Paul Voight, Chairman of Tandem Committee

I was checking the glider in the mirror as we climbed out and it appeared a little low, but not way off.

At a point just before things went bad, the tug climbed and the glider got low behind the tug.

I watched him get pretty low on the tow as the tug crossed the road at the end of the runway.

THE TUG CLIMBED AND THE GLIDER GOT LOW BEHIND IT??? NO SHIT? REALLY?

Reality 101...

Vertically speaking, a glider can only go one direction with respect to the air around it - DOWN. Like a brick, but slower - usually.

A tug, by way of contrast, can go in two directions - down and up. But - thanks to the gravity thing - it's still A LOT easier for it to go DOWN. Even left unattended it will eventually do that - as has been confirmed time and time again in the 107 year history of powered human aviation.

Therefore, gliders never ever ever ever get low behind tugs - 'cept temporarily and briefly when the two planes are in different parcels of air. Tugs get high in front of gliders ONLY because their drivers don't know or care what they're doing. And tug drivers - as sure as gravity - can ALWAYS immediately and effortlessly get back down to where they should've been staying in the first place.

Furthermore... Nobody who's ever flown a glider more that once is ever gonna dive it below a tug. For starters the tug typically flies faster than the glider wants to. And the glider is doing everything he can to stay level and in position since he's constantly aware that his life may be entirely dependent upon his doing so. If a glider is low behind a tug it means one thing - he's slow and wanting the tug to come down and give him some tension.

Dave Farkas didn't know what he was doing and had obviously had his mind rotted out by a decade and a half's worth of hang gliding culture bullshit about solving every tow problem - no matter how large or small - by reducing or dumping tension.

I have no idea what - if anything - was going through the minds of the other two conspicuously unnamed tug drivers.

And, just for the record, Jeremiah didn't get any lower on the tow than Arlan did.

So after half a dozen deaths of glider pilots who "got low behind the tug" - the way a kid on a bicycle on the side of the road gets slow in front of a Hummer - and because there's a lawsuit, USHGA for maybe the second and undoubtedly the last time in its worse than useless existence gets some flimsy half-baked advisory down on paper.

An Ad Hoc Joint Committee will investigate and reach the startling conclusion that when you abruptly kill the thrust on a plane that's low and slow and has its nose pointed up it's gonna stall, crash, and kill whoever happens to be attached to it at the time. Whoa! Who'da thunk! Now on to a serious review of the Warren Commission report.

And who's invited to participate? Matt we-do-not-warrant-this-gear-as-suitable-for-towing-anything Taber and Dave If-you-are-low,-PUSH-OUT! Glover.

And who forms the core of the Committee?

The father of Ryan Pitch-Up-And-Roll-To-Blow-The-Weak-Link Voight.

And Steve...

http://groups.yahoo.com/group/skysailingtowing/message/4633
Weaklinks and aerotowing (ONLY)

Steve Kroop - 2005/02/10 04:50:59 UTC

Davis,

Your weak link comments are dead on. I have been reading the weak link discussion in the Oz Report with quiet amusement. Quiet, because weak links seem to be one of those hot button issues that brings out the argumentative nature of HG pilots and also invokes the "not designed here" mentality and I really did not want to get drawn into a debate. Amusement, because I find it odd that there was so much ink devoted to reinventing the wheel. Collectively I would say that there have been well over a 100,000 tows in the various US flight parks using the same strength weak link with tens of thousands of these tows being in competition. Yes I know some of these have been with strong links but only the best of the best aerotow pilots are doing this.

...Kroop.

The ONLY reason the unanimous finding of this blue ribbon Ad Hoc Joint Committee was NOT to further dumb down the weak link to keep the tow better within the safe limits of control - à la Donnell post Howard Haig, Davis post Robin Strid, and the BHPA in general - was Dave Broyles.

So let's take a look at THIS paper thin slice of Swiss cheese...

One particular possible cause stood out as predominate. This was the common belief that when a glider gets low on tow the pilot can safely push out and let the glider climb up to the level of the tow plane safely because the glider will not stall under tow.

Yeah Dave (Glover)?

Remember: it is almost impossible to stall under aerotow. The induced thrust vector makes the glider trim at a higher attitude. It is OK to push way out; you will climb, not stall.

Where do you think people could've gotten an idiot idea like that?

If the pilot of the tandem glider...

The TANDEM glider? The dynamics of tandem towing are somehow different from solo? I've had an asshole dump tension on me when I needed and made the mistake of expecting the opposite and I can tell you than solo gliders stall and crash just fine.

...finds that he/she is too low behind the tug...

Bullshit. A glider doesn't FIND that he's too low behind the tug. He appropriately adjusts his pitch to compensate for a driver who gets a little high in front of him on the occasionally lethal assumption that the driver knows what he's doing. When the driver continues on his merry way the glider instinctively pushes out a little more. And when the driver stays out to lunch the glider is screwed. Yeah, hindsight is great - but you're addressing the wrong end of the rope.

Should the tandem glider become unattached...

Should the tandem glider BECOME unattached? Bullshit. The gliders doesn't BECOME unattached. Either some idiot on the front end releases it...

http://groups.yahoo.com/group/skysailingtowing/message/6726
Give 'em the rope? When?

William Olive - 2005/02/11 08:59:57 UTC

I give 'em the rope if they drop a tip (seriously drop a tip), or take off stalled. You will NEVER be thanked for it, for often they will bend some tube.

...or the "proper one-size-fits-all weak link"...

Collectively I would say that there have been well over a 100,000 tows in the various US flight parks using the same strength weak link with tens of thousands of these tows being in competition.

...mandated by some asshole - quite often the same one driving the tug - will blow for no remotely valid reason whatsoever.

The most extreme cases may result in structural failure of the glider.

It's not the extreme altitude loss that causes the structural failure - it's the tuck and tumble that results from the whipstall. And you might wanna say something about checking the adjustment of the reflex bridle once a year or so.

Towing tandems requires extra awareness on the part of the tug pilots, particularly in the early part of the tow to help the tandem pilot avoid the development of critical situations.

Yeah. Real tough job. Don't outclimb the glider.

Prior to the start of the tow, proper tow speeds based on the gross weight of the tandem glider should be determined. Greater total weight will require correspondingly higher tow speeds.

Or... Don't outclimb the glider.

It is CRITICAL to understand that the towed hang glider is at risk when the tow is slow and the glider is low.

No shit? Flying low and slow is dangerous? Wasn't there something about that on the Hang One test?

If the glider is low on tow, the tug pilot should attempt to speed up and to descend to the altitude of the towed glider, releasing the tow rope only as a last resort.

Releasing the tow rope only as a LAST RESORT? What the hell does that mean? "Well, nothing else has worked to get him out of mush mode - let's see what happens when I dump him." Your freakin' job is to keep him flying. You don't EVER dump him unless the tug is endangered.

This is because in consulting with pilots about this issue, we found that this problem is exhibited under the same circumstances with solo gliders as well.

Did you ever notice how quiet it gets the instant you pin off from a normal tow? How much consulting did you hafta do to reach that startling conclusion?

Because of the lighter wing loading of the solo gliders...

A Wills Wing Falcon 3 Tandem at the middle of its weight range loads to 1.81 pounds per square foot. A T2 154 does 2.02. So tell me again about the lighter wing loading of solo gliders?

To insure that all AT rated tandem pilots are notified, we are asking that the AT-rated tandem pilots sign on to the USHPA web site (http://www.ushga.org) and fill out a form that states that they have read and understand the safety notice.

The primary problem here is the tug drivers. So how come you're not targeting those assholes so we don't hafta tow with this:

http://www.chgpa.org/forums/viewtopic.php?f=2&t=2467
weak links

Jim Rooney - 2007/08/01 13:47:23 UTC

Whatever's going on back there, I can fix it by giving you the rope.

Jim Rooney - 2007/08/01 19:49:30 UTC

It's more of this crappy argument that being on tow is somehow safer than being off tow.

kind of threat?

Understand that we are not asking if you agree with the safety notice, but that you have read it and understand what it says.

GREAT!!! Hang gliding's never been about physics, standards, regulations, and safety. It's all about personal choice and opinion. So if you don't agree that the angle of attack goes through the roof when you kill thrust you can do and teach whatever the fuck you feel like.

We expect tandem flights to be safer than solo flights, not more dangerous.

Sorry, I'd MUCH rather see a tandem pilot and his passenger - along with the tug driver, as a bonus - killed than myself. So let's compromise. Let's maximize the standards for EVERYBODY.

This advisory is OBVIOUSLY a defensive reaction to the lawsuit filed because of the gross negligence which cost Jeremiah Thompson his life. That whipstall wouldn't have happened if the weak link hadn't blown. And that was the FRONT end weak link which is SUPPOSED to be a hundred pounds heavier than the one on the glider. But, like this piece of shit advisory, that's just a SUGGESTION within the useless SOPs. And INCREDIBLY we didn't hear a single hint of the strengths - Gs, pounds, descriptions - of the weak links involved in that cluster fuck.

If the glider is low on tow, the tug pilot should attempt to speed up and to descend to the altitude of the towed glider, releasing the tow rope only as a last resort.

So what the hell is the use of even that stupid statement if y'all are too stupid, useless, and/or gutless to establish a minimum weak link value?

Dave Broyles - 1990/11

I talked to a lot of pilots at Hobbs, and the consensus was that in the course of Eric Aasletten's accident, had a weak link break occurred instead of the manual or auto release that apparently did occur, the outcome would have been the same. Under the circumstances the one thing that would have given Eric a fighting chance to survive was to have remained on the towline.

The weak link breaking strength should be between 100% and 150% of the combined weight of the glider and pilot being towed, but each pilot should be totally responsible for his own weak link.

EIGHTEEN YEARS between Eric and Jeremiah, Dave. How the hell can a pilot be responsible for his own weak link with a stupid useless organization, stupid useless committee chairmen, and stupid useless instructors, flight park operators, and tug drivers allowing and forcing people to tow at well under a G?

http://www.hanggliding.org/viewtopic.php?t=16265
weaklinks

Kinsley Sykes - 2010/03/18 19:42:19 UTC

In the old threads there was a lot of info from a guy named Tad. Tad had a very strong opinion on weak link strength and it was a lot higher than most folks care for. I'd focus carefully on what folks who tow a lot have to say. Or Jim Rooney who is an excellent tug pilot. I tow with the "park provided" weak links. I think they are 130 pound Greenspot.

...regardless of glider weight.

http://www.chgpa.org/forums/viewtopic.php?f=2&t=2467
weak links

Jim Rooney - 2007/07/19 14:50:52 UTC

And yes, get behind me with a "strong link" and I will not tow you.

Jim Rooney - 2007/07/22 22:30:28 UTC

I've heard it a million times before from comp pilots insisting on towing with even doubled up weaklinks (some want no weaklink). I tell them the same thing I'm telling you... suck it up. You're not the only one on the line. I didn't ask to be a test pilot. I can live with your inconvenience.

How can he be responsible when he's towing behind a tug driver too stupid and useless even to understand that his release lever and stupid useless weak link make the one on the glider completely irrelevant?

http://www.wallaby.com/aerotow_primer.php
Aerotow Primer for Experienced Pilots

The Wallaby Ranch Aerotowing Primer for Experienced Pilots - 2011/01/16

Welcome to the one and only Wallaby Ranch!

The First Fulltime Aerotow Hang Gliding Flight Park in the World! Open Seven Days a Week since 1991.

If you fail to maintain the correct tow position (centered, with the wheels of the tug on the horizon), the weak link will break before you can get into too much trouble.

Remember: it is almost impossible to stall under aerotow. The induced thrust vector makes the glider trim at a higher attitude. It is OK to push way out; you will climb, not stall.

Cowboy Up Hang Gliding - 2011/01/16

A weaklink connects the V-pull to the release, providing a safe limit on the tow force. If you fail to maintain the correct tow position (or impending lockout), the weaklink is designed to break before you can get into too much trouble.

Your job is to do whatever it takes (push out or pull in, maybe even aggressively) to match the tug's ascent/climb.

http://ozreport.com/3.066
Weaklinks

Davis Straub - 1999/06/06

During the US Nationals I wrote a bit about weaklinks and the gag weaklinks that someone tied at Quest Air. A few days after I wrote about them, Bobby Bailey, designer and builder of the Bailey-Moyes Dragon Fly tug, approached me visibly upset about what I and James Freeman had written about weaklinks. He was especially upset that I had written that I had doubled my weaklink after three weaklinks in a row had broken on me.

I told him that I would be happy to publish anything that he wrote about weaklinks, but I never received anything from him or anyone else at Quest.

A few weeks later I was speaking with Rhett Radford at Wallaby Ranch about weaklinks and the issue of more powerful engines, and he felt that stronger weaklinks (unlike those used at Wallaby or Quest) were needed. He suggested between five and ten pounds of additional breaking strength.

To compensate for the greater power of the 619 engine that Rhett has on his tug, he deliberately flew it at less than full power when taking off or in anything other than absolutely smooth conditions. He started doing this after he noticed that pilots towing behind his more powerful tug were experiencing increased weaklink breakage.

A number of the pilots at the US Nationals were using "strong links" after they became fed up with the problems there. These "strong links" were made with paraglider line and were meant to fool the ground crew into thinking that the pilot had a weaklink.

The problem with strong links (neither Bobby Bailey nor I was aware at the time of the US Nationals that pilots were doing this) is that they endanger the tug pilot. If the hang glider pilot goes into a lock out, and doesn't break the weaklink (because there isn't one), they can stall the tug. I assume that Bobby Bailey won't hear about the use of strong links at the US Nationals until he reads it here.

http://www.questairforce.com/aero.html
Aerotow FAQ

Quest Air Hang Gliding

Weak Link

A good rule of thumb for the optimum strength is one G, or in other words, equal to the total wing load of the glider. Most flight parks use 130 lb. braided Dacron line, so that one loop (which is the equivalent to two strands) is about 260 lb. strong - about the average wing load of a single pilot on a typical glider. For tandems, either two loops (four strands) of the same line or one loop of a stronger line is usually used to compensate for nearly twice the wing loading. When attaching the weak link to the bridle, position the knot so that it's hidden from the main tension in the link and excluded altogether from the equation.

http://ozreport.com/5.126
Flytec Dragonfly

USAFlytec - 2001/07/14

Steve Kroop - Russell Brown - Bob Lane - Jim Prahl - Campbell Bowen

The tail section of the Dragonfly is designed so that it can accept in-line as well as lateral loads. Furthermore the mast extension, which is part of the tow system, is designed to break away in the event of excessive in-line or lateral loads. The force required to cause a breakaway is roughly equivalent to the force required to break the double weaklink used on the tail bridle. More simply put, the mast would break away long before any structural damage to the aircraft would occur.

http://groups.yahoo.com/group/skysailingtowing/message/4633
Weaklinks and aerotowing (ONLY)

Steve Kroop - 2005/02/10 04:50:59 UTC

To:
Davis Straub; Tow Group
Cc:
Rohan Holtkamp; Paris Williams
Subject:
Weaklinks and aerotowing (ONLY)

Davis,

Your weak link comments are dead on. I have been reading the weak link discussion in the OR with quiet amusement. Quiet, because weak links seem to be one of those hot button issues that brings out the argumentative nature of HG pilots and also invokes the "not designed here" mentality and I really did not want to get drawn into a debate. Amusement, because I find it odd that there was so much ink devoted to reinventing the wheel. Collectively I would say that there have been well over a 100,000 tows in the various US flight parks using the same strength weak link with tens of thousands of these tows being in competition. Yes I know some of these have been with strong links but only the best of the best aerotow pilots are doing this.

You are completely correct about weak links and lockouts. If I can beat the horse a little more: Weak links are there to protect the equipment not the glider pilot. Anyone who believes otherwise is setting them selves up for disaster. The pilot activating his or her releases is their way to save themselves. A perfect analogy is the circuit breaker in your home, it is there to protect the wire not what you plug into the wall socket. If anyone does not believe me they can plug their car retrieve 2-way radio into the wall socket and watch it go up in flames with the circuit breaker cumfortably remaining in the on position (I hope no one really tries this ;-).

A discussion of the strength of weak links is incomplete without a discussion of the tow bridal. I hear (read) strengths quoted with respect to the combined pilot and glider weight yet this is meaningless info with out knowing what bridal configuration is used and where it is placed in the bridal system. For example, a 200# weak link can allow between 200# and 800# of towline force depending on where it is placed within the various popular bridal configurations.

On the tow plane we use 1-1/2 loops (3 strands) of 130# line. The weak link is placed in the top of a V-bridal which would yield a maximum nominal towline tension of around 780#. However, due to the fact the knots (two are required since there are three strands) are not "buried" the maximum towline tension is greatly reduced. I do not know the exact tow line tension required to break this weak link but the value is somewhat moot since the weak link is not too strong so as to cause any damage to the tow plane and it is not too weak to leave the glider pilot with the towline.

Summary

Do not attempt to aerotow unless you have received proper training
Do not attend an aerotow comp if you do not have considerable experience flying a comp class glider in comp class conditions
Weak links are there to protect the equipment
Weak links do NOT prevent lockouts and no amount of weak link rules will prevent lock outs
In the event of a lock out releases are there to save the pilot

Best regards, Steve - Flytec USA

http://www.chgpa.org/forums/viewtopic.php?f=2&t=3600
Weak link question

Jim Rooney - 2008/11/24 18:54:27 UTC

I'm confused. I never said the tug's ass was endangered. That's why we use 3strand at the tug's end. Using 4 strand can rip things off (it's happened). When forces are achieved that do break a 3 strand, your tail gets yanked around very hard, which does have implications as to the flight characteristics and flightpath. AKA, I have no desire to allow you to have the ability to have that effect on me when I tow you... esp near the ground.

http://ozreport.com/12.081
Weaklinks - the HGFA rules

Davis Straub - 2008/04/22 14:47:00 UTC
Hughenden Airport, Queensland

What material should be used for weaklinks?

From section 3.4 of the 1999 Hang Gliding Federation of Australia Towing Manual:

Recommended breaking load of a weak link is 1g. - i.e. the combined weight of pilot, harness and glider (dependent on pilot weight - usually approximately 90 to 100 kg for solo operations; or approximately 175 kg for tandem operations).

Each pilot should have his/her own weak link of appropriate strength.

It is recommended that a new weak link is used for every launch; or a fabric sheath is used to cover the weak link to protect it as it is dragged along the ground.

Testing weak links tied from "No 8" builders string line has shown that the type of knot used does not greatly affect the breaking strain of the weak link.

Here is the requirement from the 2007 Worlds local rules (which I wrote) for weaklinks:

Pilots must use weaklinks provided by the meet organizers and in a manner approved by the meet organizers. All weaklinks will be checked and use of inappropriate weaklinks will require the pilot to go to the end of the launch line to change the weaklink.

Weaklinks will consist of a single loop of Cortland 130 lb Greenspot braided Dacron Tolling line and should be placed at one end of a shoulder bridle.

At the 2008 Forbes Flatlands Greenspot for the first time was used as the standard weaklink material (thanks in large part to the efforts of Bobby Bailey). We applaud these efforts to improve the safety of aerotowing by using a better weaklink material.

CHGA Incident Report

Ralph Sickinger - 2000/08/28 18:18:20

2000/08/26 - Under sled conditions, I decided to borrow Brian Vant-Hull's glider instead of setting up my own, since we both fly the same type of glider. Brian's release is a different style, but I tested it twice during preflight to make sure I was familiar with it. After towing to altitude, Sunny waved me off; I pulled on the release (hard), but nothing happened! After the second failed attempt to release, I thought about releasing from the secondary, but before I could move my hand the tug stalled and started to fall...

Dick Reynolds - 1992/11

Lookout Mountain Flight Park had acquired a new Moyes aerotug and I was the pilot - claiming 200 plus tows to date. At 11:00 AM on May 17, 1992 I had decided to take two more tows and then call it quits for the day.

The conditions on this particular morning were very light - great for towing. Takeoff went smoothly, with the glider then the tug lifting off, thus increasing my angle of climb. My airspeed was four mph above stall. 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.

http://www.dynamicflight.com.au/WeakLinks.html
Weak Links - Dynamic Flight Hang Gliding School

James Freeman - 2005

Weak Links

In all aviation the pilot is usually the weakest link...

The purpose of a weak link is solely to prevent the tow force from increasing to a point that the glider can be stressed close to or beyond its structural limits. Lockouts can and do occur without increasing tow tension up until the point where the glider is radically diverging from the direction of tow. At this point tension rises dramatically and something will give - preferably the weak link. Given that a certified glider will take 6-10 Gs positive a 1.5 G weak link as opposed to a standard 1 G weak link should not significantly increase the risk of structural failure. It will however significantly decrease the probability of an unwanted weak link break.

http://www.chgpa.org/forums/viewtopic.php?f=2&t=229
Quest Friday, shoulder towing

Paul Tjaden - 2005/03/05 13:26:19 UTC

I also feel it may be easier to pin off in case of a lockout because you have a Bailey (for me, two of them, one on each side) and they are much closer to your center of gravity. Reaching that handle way out to the side can be challenging in a hard turn. The Bailey is right there.

I would welcome hearing more expert opinions, as well.

http://www.chgpa.org/forums/viewtopic.php?f=2&t=3380
Lauren and Paul in Zapata

Lauren Tjaden - 2008/07/21 14:27:04 UTC

Zapata has delivered as promised, day after day with howling winds and good lift, where flights of over 100 miles (and much more) are possible.

Yesterday I chased Paul again. The tow rope weak link broke when Paul locked out and the weak link he got from Tad did not break. Russell said it was about the worst he has ever had his tail pulled around. Anyhow, I would advise against those weak links, though Tad's barrel releases do seem better able to release under stress. After Russell got a new rope and Paul recovered, he was late leaving and got trapped under some cirrus.

http://www.chgpa.org/forums/viewtopic.php?f=2&t=3391
More on Zapata and weak link

Paul Tjaden - 2008/07/22 04:32:22 UTC

The lockout Lauren mentioned was precipitated by my attempt to pull on more VG while on tow. I have done this before but this time the line wouldn't cleat properly and while I was fighting it, I got clobbered and rolled hard right in a split second. There was a very large noise and jerk as the relatively heavy weak link at the tug broke giving me the rope. I recovered quickly from the wingover and flew back to the field to drop the line and then relaunched after changing to a normal weak link. I have never had a lockout situation happen so quickly and dramatically and had no chance to release as I have always thought I could do. Had the tug's link not broken, things could have gotten very ugly very fast. I still don't like weak links breaking when they shouldn't, but the one I was using was way too strong.

http://www.chgpa.org/forums/viewtopic.php?f=2&t=3648
Oh no! more on weak links

Carlos Weill - 2008/11/30 19:24:09 UTC

On June of 2008 (2008/06/02) during a fast tow, I noticed I was getting out of alignment, but I was able to come back to it. The second time it happen I saw the tug line 45 deg off to the left and was not able to align the glider again I tried to release but my body was off centered and could not reach the release. I kept trying and was close to 90 deg. All these happen very quickly, as anyone that has experienced a lock out would tell you. I heard a snap, and then just like the sound of a WWII plane just shut down hurdling to the ground, only the ball of fire was missing. The tug weak link broke off at 1000ft, in less than a second the glider was at 500ft. At that point I realized I had the rope, so I drop it in the parking lot.

-----

A few days after I wrote about them, Bobby Bailey, designer and builder of the Bailey-Moyes Dragon Fly tug, approached me visibly upset about what I and James Freeman had written about weaklinks. He was especially upset that I had written that I had doubled my weaklink after three weaklinks in a row had broken on me.

- Dragonfly is one word, Davis.

- Nevertheless Davis displays a brief glimmer of reptilian level intelligence by responding to a problem with an actual common sense solution.

Pilots must use weaklinks provided by the meet organizers and in a manner approved by the meet organizers. All weaklinks will be checked and use of inappropriate weaklinks will require the pilot to go to the end of the launch line to change the weaklink.

http://ozreport.com/9.011
2005 Worlds

Davis Straub - 2005/01/13

Tom Lanning had four launches, and two broken weaklinks and a broken base tube. He made it just outside the start circle.

- A solution which, of course, Davis being Davis, denies to everyone else.

For tandems, either two loops (four strands) of the same line or one loop of a stronger line is usually used to compensate for nearly twice the wing loading.

- But if Davis and James had gone up together on the same glider and used a double loop that would've been totally cool - 'cause that way the glider weak link doesn't override the tug weak link, right Bobby?

- Right Davis?

A few weeks later I was speaking with Rhett Radford at Wallaby Ranch about weaklinks and the issue of more powerful engines, and he felt that stronger weaklinks (unlike those used at Wallaby or Quest) were needed. He suggested between five and ten pounds of additional breaking strength.

- Grow a pair, Rhett. Go nuts and jack 'em up an extra fifteen.

http://www.chgpa.org/forums/viewtopic.php?f=2&t=3661
Flying the 914 Dragonfly

Jim Rooney - 2008/12/06 20:01:49 UTC

Don't ever pull a solo at full throttle... they will not be able to climb with you. You can tow them at 28mph and you'll still leave them in the dust... they just won't be able to climb with you... weaklinks will go left and right.

And ignore the fact that you're using the same weak link on 200 and 350 pound gliders - and calling it one G for everyone.

To compensate for the greater power of the 619 engine that Rhett has on his tug, he deliberately flew it at less than full power when taking off or in anything other than absolutely smooth conditions. He started doing this after he noticed that pilots towing behind his more powerful tug were experiencing increased weaklink breakage.

- Yeah, protect the 130 pound Greenspot at all cost - it's Sacred, ya know.

- Increased breakage over a rate of WHAT?

A number of the pilots at the US Nationals were using "strong links" after they became fed up with the problems there. These "strong links" were made with paraglider line and were meant to fool the ground crew into thinking that the pilot had a weaklink.

- Such BLATANT disregard for THEIR OWN SAFETY!!! Imagine - competition pilots wanting control over their own tows!

http://groups.yahoo.com/group/hhpa/message/11155
Question

Shane Nestle - 2010/09/17 22:17:50 UTC

So far I've only had negative experiences with weak links. One broke while aerotowing just as I was coming off the cart. Flared immediately and put my feet down only to find the cart still directly below me. My leg went through the two front parallel bars forcing me to let the glider drop onto the control frame in order to prevent my leg from being snapped. Fortunately, I fly with solid wheels on the glider, so me, the glider, and the dolly all rolled safely to a stop with no damage to anyone or anything. All other weak link breaks have been during boat towing, and were uneventful and unwarranted.

The problem with strong links is that they endanger the tug pilot. If the hang glider pilot goes into a lock out, and doesn't break the weaklink (because there isn't one), they can stall the tug.

- If the glider goes into a lockout his strong link will simultaneously take the tug's weak link out of the loop and render releases on both ends inoperable and both pilots will find themselves helpless and doomed.

After the second failed attempt to release, I thought about releasing from the secondary, but before I could move my hand the tug stalled and started to fall...

The combination of high nose angle plus the pull exerted by the climbing hang glider brought me to a screeching halt, so to speak. 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.

- Whereas a proper flight park approved weak link will automatically free the tug whenever it senses it's in danger.

A good rule of thumb for the optimum strength is one G...

- Yeah, right.

The force required to cause a breakaway is roughly equivalent to the force required to break the double weaklink used on the tail bridle.

- So people who had absolutely no freaking clue as to the effects of knotting, the maximum breaking strength of a loop of 130 pound Greenspot, how that strength translated to tow tension on either one or two point bridles, what the Dragonfly normally delivered by way of normal tow tension, the range of variation in turbulence and through maneuvers, or even the purpose of a weak link decided that the Sacred Loop of 130 pound Greenspot put all gliders - regardless of their flying weights - at exactly one G and that exactly one G is the perfect rating for an aerotow weak link.

- And since a doubled weak link must obviously be twice the strength of a single and any tandem glider is obviously twice the weight of any solo glider the double loop is just perfect for putting all tandems at precisely one G.

More simply put, the mast would break away long before any structural damage to the aircraft would occur.

- That's the purpose of the weak link - you freakin' morons. You put the weak link between the plane and the towline so that neither the plane nor the towline breaks. You don't design part of the plane to break at the same tension as the weak link you're using - especially when you "THINK" that a double loop of 130 Greenspot blows at 520 pounds.

- So now I need to keep my weak link below whatever the hell a double loop of 130 translates to on a tug whose driver never bothers to change it until it blows and leaves some poor clown with 250 feet of Spectra to try to avoid being that poor clown left with 250 feet of Spectra.

That's why we use 3strand at the tug's end. Using 4 strand can rip things off (it's happened).

- No shit. You design the mast to blow at the same tension that the weak link does and do you think maybe you'll blow the mast instead of the weak link about half the time? After the mast fatigues a bit maybe all the time?

- So now, in order to keep the mast from blowing before the designated weak link that was ASSUMED to be appropriate for the task, you've gotta dumb down the weak link to what you ASSUME will be three quarters of that figure.

- But you're still using double loops on the tandems so you're upping the likelihood of leaving it with the Spectra draped over the basetube.

- And since I wanna fly at one and a half Gs - about 480 pounds - you're gonna screw me over real good too.

Your weak link comments are dead on.

- Those aren't Davis's comments. That's Davis quoting Rohan. A moron like Davis will never have the slightest clue what this issue is all about.

I really did not want to get drawn into a debate.

- Yeah Steve, if you let yourself get drawn into debate with someone who knows what he's talking about you'd get your freakin' head handed back to you on a platter after about fifteen seconds.

Amusement, because I find it odd that there was so much ink devoted to reinventing the wheel.

- Yeah, you Florida 130 pound Greenspot junkies totally NAILED IT on your first and only effort.

Collectively I would say that there have been well over a 100,000 tows in the various US flight parks using the same strength weak link with tens of thousands of these tows being in competition.

- With no problems whatsoever. You can use the crap releases with which you guys flood the market and those weak links will always blow "before you can get into too much trouble", they'll never blow when you don't want them to, and they'll always hold in an emergency to prevent you from whipstalling.

Yes I know some of these have been with strong links but only the best of the best aerotow pilots are doing this.

- It's not the best in terms of high competition points - as you mean it. It's the best in terms of intelligence. And there's not a lot of overlap in those two subsets.

The weak link is placed in the top of a V-bridal which would yield a maximum nominal towline tension of around 780 pounds. However, due to the fact the knots (two are required since there are three strands) are not "buried" the maximum towline tension is greatly reduced.

- Yeah, that's the ASSUMPTION - but none of you guys have actually gone to the trouble to actually test it, right?

I do not know the exact tow line tension required to break this weak link...

- Right. You actually don't even have the foggiest clue what the towline tension would be.

...but the value is somewhat moot since the weak link is not too strong so as to cause any damage to the tow plane and it is not too weak to leave the glider pilot with the towline.

- Yeah. Totally moot. As long as everyone lives within the bounds of your proper one-size-fits-all Utopia, all discussion of pounds and Gs is stifled, and the tug driver gives a flying fuck about the stuff at his end.

The tug weak link broke off at a thousand feet, in less than a second the glider was at five hundred.

- It's a bridLE, by the way.

Do not attempt to aerotow unless you have received proper training

- And where the hell is anybody gonna be able to get THAT?

In the event of a lock out releases are there to save the pilot

---

One moment he was correcting a bit of alignment with the tug and the next moment he was nearly upside down.

After the second failed attempt to release, I thought about releasing from the secondary, but before I could move my hand the tug stalled and started to fall...

I just kept hitting the brake lever for a few seconds in WTF mode, and the instructor used the barrel release.

Robin's own release failed to release. Do not use a 'Wichard' or 'spinnaker' release directly connected to a string or rope. This type of metal release has a metal knob on the opening arm that a rope will catch on, even when the release is activated and open.

I tried to release but my body was off centered and could not reach the release.

When Jim got me locked out to the right, I couldn't keep the pitch of the glider with one hand for more than a second (the pressure was a zillion pounds, more or less), but the F'ing release slid around when I tried to hit it. The barrel release wouldn't work because we had too much pressure on it.

I have never had a lockout situation happen so quickly and dramatically and had no chance to release as I have always thought I could do.

---
- Any more brilliant ideas? Or are you still content to read the discussions in quiet amusement while the wheel reinvention discussions are locked down by total assholes like Davis?

I'm confused.

- You've never had enough brains to be confused. You've always been dead certain of everything your fellow assholes at Ridgely taught you on Day One.

When forces are achieved that do break a 3 strand, your tail gets yanked around very hard, which does have implications as to the flight characteristics and flightpath.

- Pick one to max out:
-- four strander straight aft
-- two strander straight up

(PLEASE pick the latter.)

I NEVER play Russian roulette with anything heavier than .22 caliber. A .38 can kill you so much deader.

AKA, I have no desire to allow you to have the ability to have that effect on me when I tow you... esp near the ground.

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 doctors tell me that I'll be walking in a year or so, but that I shouldn't plan on winning any foot races.

- Obviously the problem there was that the glider was using a "strong link". Everyone knows that a proper single loop of 130 will blow before anyone can get into too much trouble.

- What's stopping you from squeezing a lever while the glider's trying to move the back end of a 250 foot line sideways enough for you to even notice at the front end?

- Aren't you using a weak link on your end light enough to protect the junk you're flying?

At the 2008 Forbes Flatlands Greenspot for the first time was used as the standard weaklink material (thanks in large part to the efforts of Bobby Bailey). We applaud these efforts to improve the safety of aerotowing by using a better weaklink material.

Due to the rough conditions weak links were breaking just about every other tow...

Tom Lanning had four launches, and two broken weaklinks and a broken base tube.

- Yeah Bobby, great job. Thanks. Do us all a big favor... Stick to designing tugs and stay out of releases and weak links.

Given that a certified glider will take 6-10 Gs positive a 1.5 G weak link as opposed to a standard 1 G weak link should not significantly increase the risk of structural failure.

- Given that a certified glider will take 6-10 Gs positive an extra half G will have no bearing whatsoever on the issue of structural failure.

- How the hell did one G get to be the "STANDARD" weak link anyway?

Reaching that handle way out to the side can be challenging in a hard turn.

- Or totally ineffective - ask Lauren or Axel. Or physically impossible - ask Carlos.

I also feel it may be easier to pin off in case of a lockout because you have a Bailey (for me, two of them, one on each side)...

- I may have been the first person to put barrel releases at both shoulders. I got mocked at Ridgely for doing so.

The Bailey is right there.

Yeah, everything is always right there - until you get into a situation in which it matters.

I would welcome hearing more expert opinions, as well.

- Wanna listen to me, Paul? There's no such thing as "an easy reach" - ANYWHERE - when the shit hits the fan.

- Don't wanna listen to me?

Manned Kiting
The Basic Handbook of Tow Launched Hang Gliding
Daniel F. Poynter
1974

"Never take your hands off the bar." - Tom Peghiny

Got that? Did you catch the date? Is this message EVER gonna sink in?

I have never had a lockout situation happen so quickly and dramatically and had no chance to release as I have always thought I could do.

- Yeah, that's when it's REAL nice to have a string between your teeth. It that had happened in the kill zone you might have still been dead but your chances would've been WAY better. But don't worry, Paul, it'll probably NEVER happen to you in the kill zone.

The lockout Lauren mentioned was precipitated by my attempt to pull on more VG while on tow. I have done this before but this time the line wouldn't cleat properly...

- So you're at the time and place where people specifically go to set world records, in some of the most potentially violent thermal air you've ever been in, and...

Never take your hands off the bar.

...you take one of your hands off the bar for something you really don't need to be dicking around with right now.

In all aviation the pilot is usually the weakest link...

...and while I was fighting it, I got clobbered and rolled hard right in a split second.

- This is not an unprecedented situation.

One moment he was correcting a bit of alignment with the tug and the next moment he was nearly upside down.

There was a very large noise and jerk as the relatively heavy weak link at the tug broke giving me the rope.. I recovered quickly from the wingover and flew back to the field to drop the line and then relaunched after changing to a normal weak link.

- RELATIVELY heavy... NORMAL weak link. Relative to WHAT? Normal for WHOM? Lauren? Karen? Ayesha? You wanna tell us something about pounds? Or Gs? Of course not. 'Cause you don't have any more of a freakin' clue than the people who "trained" and are flying with and towing you.

Had the tug's link not broken, things could have gotten very ugly very fast.

- Things DID get very ugly very fast. And if you had been at a hundred feet playing with a string instead of flying the glider with a Bailey release on your shoulder you'd have been dead no matter what was being used for a weak link on either end.

Today is a very sad day for WWHGC members. Our good friend and fellow pilot Roy Messing passed away this afternoon as a result of a hang gliding accident this past Monday. Roy had released after entering into a mild lock-out but did not regain control in time to set up for a proper landing.

And that was in dead morning air with a single loop of 130 pound Greenspot on a Falcon 3 with both hands on the basetube and a lever under one of them. He wasn't lucky enough to have enough air to recover from a wingover like you did.

...until the point where the glider is radically diverging from the direction of tow. At this point tension rises dramatically and something will give - preferably the weak link.

- Had the "relatively heavy weak link at the tug" NOT broken the rate of increase was so freakin' unreal that you'd have never known or felt the difference. That's what James Freeman, Steve Kinsley, and I understand, you don't, and shitheads like Jim Rooney and a lot of the people you fly with never will.

http://www.aviationbanter.com/archive/index.php/t-40965.html
Are Weak Links really Necessary for Aero Tow?

Bill Daniels - 2006/09/18 14:30

I would like to add, however, that at least my reading of accident reports suggest that a fatal glider accident is more likely when the towline fails prematurely. For that reason, I like to stay near the stronger end of the FAR 80-200% range.

- I gave you something at or just under 1.5 Gs. Try asking Russell to translate his end into pounds or Gs. He's just doing what you are - the same as everybody else without a clue as to why.

I still don't like weak links breaking when they shouldn't, but the one I was using was way too strong.

- Yeah Paul. You're like everybody else. You don't want it breaking when it shouldn't - just when in "SHOULD". And by "SHOULD" you mean you want "a weak link which will infallibly and automatically release the glider from tow whenever the tow line tension exceeds the limit for safe operation" so you can pretend you're safe flying with one hand on a VG cord and the other flailing around for a Bailey release. The problem is that that's a totally mythical animal fabricated by Donnell thirty years ago.

- Bullshit. The only thing you know about the strength of that weak link from that flight was that:

-- It didn't do this...

...but at 400 feet my pussy-##s weak link broke.

-- The "relatively heavy" weak link at the tug broke before yours.

-- Your glider didn't.

- That weak link was half a G under what USHGA and the FAA say it can be so if it is "way too strong" why aren't you doing anything to change the regulations?

Russell said it was about the worst he has ever had his tail pulled around.

- "ABOUT" the worst? What were some of the other related amusing anecdotes? What weak links were involved?

- Was that the only time Russell had ever had his "relatively heavy" weak link blow?

- How long had it been since Russell had replaced or even checked his "relatively heavy" weak link?

- How much of a lateral vector was he feeling? A loop of 130 on a one point bridle can deliver up to 260 pounds. Was his tail being pulled sideways to the tune of 260 pounds?

When Jim got me locked out to the right, I couldn't keep the pitch of the glider with one hand for more than a second (the pressure was a zillion pounds, more or less), but the F'ing release slid around when I tried to hit it. The barrel release wouldn't work because we had too much pressure on it.

Anyhow, the tandem can indeed perform big wingovers, as I demonstrated when I finally got separated from the tug.

- Yeah, you had too much PRESSURE on it.

- What was going on with Jim Prahl's Dragonfly over the course of that cluster fuck?

...when I finally got separated from the tug.

- When you FINALLY got separated. Not "when the weak link blew" but probably after Dustin got hold of the lever then on the far side of the right downtube. (Always nice to have lotsa air and four hands in a lockout emergency, isn't it?) So what weak links were you guys using that made this tow so much safer than Paul's?

Anyhow, I would advise against those weak links...

- Did you advise anyone not to use Quest and Bailey releases after your little roller coaster ride? Or is it OK to use and take passengers up on shit equipment because everyone else does and your cherished friends at Quest and Ridgely make and sell it?

- What about the weak links you were using? Aren't they supposed to blow before you get out of control?

- Paul flies in violent thermal air, Carlos flies in smooth air.

- Paul flies a Bridle Link (one point) - 432 pounds, about the same as the double loop of 130 pound Greenspot that many fed up pilots try to sneak by the Launch Line Nazis, the same as Campbell Bowen flew before he switched to one of my Bridle Links - which puts his glider at a bit under 1.5 Gs. Carlos flies a single loop on a two point bridle which blows at anywhere between 125 and 243 pounds of tow tension.

The lockout Lauren mentioned was precipitated by my attempt to pull on more VG while on tow.

I tried to release but my body was off centered and could not reach the release.

- Paul tries to fly a glider on tow with one hand, Carlos tries to fly a glider on tow with one hand.

I got clobbered and rolled hard right in a split second.

I kept trying and was close to 90 deg. All these happen very quickly, as anyone that has experienced a lock out would tell you.

- Paul locks out in a heartbeat, Carlos locks out in a heartbeat.

I have never had a lockout situation happen so quickly and dramatically and had no chance to release as I have always thought I could do.

I tried to release but my body was off centered and could not reach the release.

- Paul can't get to his release, Carlos can't get to his release.

There was a very large noise and jerk as the relatively heavy weak link at the tug broke...

I heard a snap...

- Paul hears a very large noise and feels a jerk as the relatively heavy weak link at the tug broke, Carlos hears a snap as the relatively heavy weak link at the tug broke.

Russell said it was about the worst he has ever had his tail pulled around.

- Paul's driver reports his tail being pulled around about the worst he's ever had it as his "relatively heavy" standard Dragonfly weak link blows, we have no report from Carlos's driver as his "relatively heavy" standard Dragonfly weak link blows.

...giving me the rope.

...At that point I realized I had the rope...

- Paul gets the rope, Carlos gets the rope.

I recovered quickly from the wingover...

...and then just like the sound of a WWII plane just shut down hurdling to the ground, only the ball of fire was missing. The tug weak link broke off at a thousand feet, in less than a second the glider was at five hundred.

- Paul recovers quickly from the wingover, Carlos goes into a screaming dive and loses five hundred feet - half his altitude - before being able to pull out.

...and flew back to the field to drop the line...

At that point I realized I had the rope, so I drop it in the parking lot.

- Paul returns the towline, Carlos returns the towline.

...and then relaunched after changing to a normal weak link.

Anyone who wants recommendations for their towing or training, you have a great pool of knowledge in the tow parks especially from the ones that do it regularly and have the experience in the tug and behind the tug.

- Paul goes right back up into the washing machine with the same release crap that he just found completely useless when the shit hit the fan, Carlos goes right back up with the same release crap that he just proved can be completely inaccessible when the shit hits the fan.

- Carlos sings the praises of the assholes who set him up with the crap that would've killed him if the shit had hit the fan 510 feet lower.

- Paul changes back to a "NORMAL" one-size-fits-all weak link...

One broke while aerotowing just as I was coming off the cart. Flared immediately and put my feet down only to find the cart still directly below me. My leg went through the two front parallel bars forcing me to let the glider drop onto the control frame in order to prevent my leg from being snapped.

...like Carlos was using so that next time, instead of recovering quickly from the wingover, he'll go into a screaming dive and lose five hundred feet before being able to pull out.

- Since Carlos was flying Flight Park Mafia gear with a Flight Park Mafia approved weak link his incident never even makes it into the collective memory.

- But Paul was using a "strong link". Not only a "strong link" but something that came out of Tad's black magic workshop. So watch what happens over time...

I recovered quickly from the wingover...

Janni Papakrivos - 2008/11/05 23:03:26 UTC

And let's not forget Paul Tjaden who would have been screwed by a stronger weak link.

I recovered quickly from the wingover...

Lauren Tjaden - 2008/11/21 12:38:21 UTC

It was a pretty scary incident.

I recovered quickly from the wingover...

Lauren Tjaden - 2008/07/21 14:27:04 UTC

Russell said it was about the worst he has ever had his tail pulled around.

Lauren Tjaden - 2008/11/20 22:50:53 UTC

Russell quoted afterward that he'd never had his tail pulled around so violently.

I recovered quickly from the wingover...

Janni Papakrivos - 2008/11/21 16:56:55 UTC

...as did Paul when he almost stretched the sail of his $10,000 glider to the point where he'd have to consider competing with Falcon pilots.

I recovered quickly from the wingover...

Lauren - 2008/11/20 22:50:53 UTC

Luckily, Paul's glider was not stressed to the point of failure...

I recovered quickly from the wingover...

Patrick Halfhill - 2009/06/21 23:22:23 UTC

Another pilot that was convinced at the ECC that he needed a stronger weaklink, took his to Texas and I believe through it away after a near death experience.

I recovered quickly from the wingover...

http://groups.yahoo.com/group/skysailingtowing/message/7067
AT SOPs - proposed revisions

Subj: Re: [Tow] AT SOPs - proposed revisions
Date: 2009/05/10 02:08:52 UTC
From: cloud9sa@aol.com
To: skysailingtowing@yahoogroups.com
cc: GreggLudwig@aol.com, lisa@lisatateglass.com

Hi Tad.

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. For best effect, I suggest that you describe in your letter (and also post to the skysailingtowing group and share with the USHPA Tow Committee) your areas of expertise (if any) related to this issue, and list your qualifiications, logged hours, and currency in certain categories, such as:

1. hang glider pilot rating and logged hours
2. hang glider aerotow rating, logged hours, and logged number of tows
3. hang glider tug pilot rating, logged hours towing, and logged number of tows
4. hang glider aerotow administrator appointment date
5. hang glider aerotow supervisor appointment date
6. hang glider tanderm instructor rating, logged hours of aerotow tandem instruction, and logged number of instructional flights
7. airplane pilot license ratings and logged number of hours
8. airplane tow pilot endorsement date, logged number of hours towing with airplane, logged number of tows
9. sailplane tow pilot license ratings, logged number of hours, logged number of tows.
10. sailplane instructor license date, logged number of hours of instruction, logged number of instructional tows
11. any other flying or engineering-related credentials that you may have as evidence of your competence to make these claims.

(BTW, if you have an AT hang glider rating or above the you would/should have received the USHPA Aerotow Guidelines as part of your instruction from the person who taught you to aerotow and/or gave you your AT rating, and you should currently have access to them via the packet that is accessible to you on the USHPA web site, if your AT or higher AT-related ratings and appointments are current.)

It would also be good for the FAA and USHPA to know what kind of ultalight or sport plane tug and airplane you use for towing hang gliders and sailplanes with at your operation (if any), along with a general description of your towing operation or who you provide towing and instructional services for (if any).

Additionally, if you want to really present a convincing argument, you should also: (a) get other experts to co-sign your letter, such as those who have some or most of the aerotowing-related credentials listed above, who have been doing this for many years with many students, and who support your argument; and (b) present reliable data based on valid research showing that there is a significant difference in safety with the changes that you recommend. Supportive comments from aerotow experts along with convincing data can make a difference. Otherwise, it may seem as if your perception of "the sky is falling" may not be shared by most others who have a wealth of experience and who are deeply involved in aerotowing in the US.

This information would also be very helpful in convicing the USHPA and others to take your complaint seriously. Most of the individuals who serve on the USHPA Towing Committe have most of the credentials listed above, so it will be great for you to let them know about your similar credentials and depth of experience, too. If you do not have those credentials, it will be a simple matter for the USHPA Tow Committee to respond to the FAA to discount your complaint, so it will be very important for you to present this information in your letter to the FAA and to others now.

The best way to make change is to get involved, and join the Tow Committee at its meetings. That's what people who really care do to make change. Such is the nature of the great opportunities we have to make a difference in the US (although it means having to spend time, money, and effort, compared to the ease of just sitting in front of a computer.)

Good luck with your endeavor, and regards,

Dr. Tracy Tillman
USHPA Director, Region 7
FAA Detroit FSDO FAAST Aviation Safety Counselor

http://groups.yahoo.com/group/skysailingtowing/message/64
Dolly

Tracy Tillman - 2001/02/05 15:17:09 UTC

All the various factors combined can put more pressure on the weak link and cause a premature break.

http://groups.yahoo.com/group/skysailingtowing/message/547
High Wire Act World News

Gustav Kühn - 2001/05/16 14:18:58 UTC
Capetown

The bridle is about 3 m of 7 mm hollow ski-rope. The red colour is easier to find in long grass/brush
The tow rope is 650 m of twisted polypropolene, the dealer sells it by weight, I have 20 kg of it.
On weak links, in a previous post someone mentioned that it is a problem if the WL is on the released end of the bridle, how stupid of me not to see the potential problem here, during a snag on the tow rope ring.
I will now attach another weaklink to the other end of the bridle, where it attaches to my leg straps, the towing force should be the same there.

http://groups.yahoo.com/group/skysailingtowing/message/549
Weaklinks/bridles; was: high wire act world news

Tracy Tillman - 2001/05/16 15:14:55 UTC

We (and many others) do not recommend using a second weaklink on the non-released end of the bridle. That weaklink is just as likely to break as the one on the other end. If the lower weak link breaks, the bridle could get caught in the towline ring, and pull the glider from the 'biner or keel, causing it to tuck. The other weaklink (on top) may not break prior to the tuck.

The weaklink should be on the released end of the bridle, and the bridle should release from the top. That way, if the bridle does get caught on the ring, it is pulling from the body, rather than from the glider, and the glider may still be controllable--in which case you can use your secondary release (or hook knife if that fails) to release.

http://groups.yahoo.com/group/skysailingtowing/message/612
hang gliding Comments on outlandish release/bridle/weak link

Tracy Tillman - 2001/05/25 01:01:56 UTC

We normally use 130 lb., but we now also have 150 lb. on hand for heavier pilots in draggier gliders. I use 150 lb. for pro-towing, but Lisa still uses 130 lb. for pro-towing. I use 130 lb when using my regular towing bridle.

http://groups.yahoo.com/group/TUGS/message/199
hang gliding DRAGONFLY Climbing-rates

Tracy Tillman - 2001/10/02 11:17:24 UTC

Michael Derry - 2001/10/01 15:38:42 UTC

The climb rate for the 914 is mind blowing !!!!!!!! I wonder how much extra tension is pulling the hang glider say in KG's?

I don't know--there is some.

Do pilots who are used to say a 582 tow, break many weak links when they first encounter a 914?

Some do, mostly because they are used to re-using old weaklinks, and because they use pre-tied weaklinks, in which the knot itself weakens the line. We use a wrap tying method, so that the knot does not pull into the line. Still, we do encounter a few more (but not many) weak link breaks in heavy turbulence, if the pilot is not able to fly smoothly through it. Still, it is probably better than towing through heavy turbulence behind some trikes, where the tow line repeatedly slackens and tightens up.

In some cases, such as for very heavy pilots, and/or draggy gliders (Fledge), we use 150 lb, rather than 130 lb weak link line. I use 150 lb. line for shoulder-only towing, whereas Lisa uses 130 lb. Otherwise, I use 130 lb. for towing from the carabiner/keel. I double that for tandems.

http://groups.yahoo.com/group/skysailingtowing/message/4592
Weaklinks

Tracy Tillman - 2005/02/08 19:16:10 UTC

Unfortunately, many hang glider pilots do not appreciate or understand the significant risks repeatedly taken by tug pilots and aerotow club or flight park operators, on behalf of hang glider pilots so that the hang glider pilots can have safe tows and have fun. Most tow pilots experience many more tows under a much wider variety of conditions, pilots, and equipment, and than even the some of the most experienced and advanced hang glider pilots. It is interesting to note (or so it seems) that when hang glider pilots try being tow pilots, the most don't last long.

The sailplane guys have been doing this for a long time, and there are many hang glider pilots and quite a few tug pilots who don't understand what the sailplane guys have learned over the years. It certainly would help if hang glider towing methods and training were standardized to the degree that they are in the sailplane world. Maybe the Sport Pilot regs will eventually help hang gliding in this regard. It helps a lot when a hang glider pilot gets a little training in sailplanes, and even more so if they experience sailplane towing at different locations and encounter very similar systems and techniques.

Both sailplanes and aerotowed hang gliders use properly-rated weaklinks at both ends for a very good reason. It is not primarily to prevent a lock out. It is a fallicy to think that weak links will reliably prevent a lock out. In engineering terms, the weaklink is not a robust design--it will not break consistently in a wide variety of conditions. If it is a lower-rated weak link, it may or may not break prior to or during a lock out--and it is also more likely to break in the heavy turbulence experienced by advanced pilots. Therefore, an advanced hang glider pilot may opt for a stronger weaklink, with some additional risk. Conversely, use of a weaker link in turbulance may cause a premature weaklink break, which can also entail some risk. Therefore, the use of a stronger weak link may be warranted.

If an advanced pilot wishes to use a stronger weak link, the degree of extra strength must be limited. Primarily, the use of a weak link is to save the tug pilot's behind, by preventing structural and/or control failure--and it should also help to prevent structural and/or control failure of the vehicle being towed. Secondarily, a lower-rated weaklink may or may not help to prevent a full lockout--just don't count on it.

The following recommendations are based on our experience over the last 10 years. We use 4-stroke powered Dragonflies, and our spring/early summer air is very turbulent.

Whether pro-tow or 3 point tow, we use and recommend a single stand loop of 130 lb weaklink for general pilots, which is not pre-tied, but uses the 4/5-loop-then-tie method for attachment. Pre-tying is less robust, meaning it does not break as consistently as the 4/5-loop-then-tie method. We use a single strand of 150 lb weaklink, again not pre-tied, for heavier, more advanced pilots in very turbulent air. We use a double loop of 130-lb weaklink for tandems, Scot Maue (big, VERY big), and at the other end for the tug. Also, the hang glider pilot should only use one weaklink, at the upper attach point in a 3 point bridle system, to prevent tucking should the bridle release at the low end and snag the ring. We have had excellent results using that system.

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.

Regards,

Tracy Tillman
Draachen Fliegen Soaring Club
Cloud 9 Field
11088 Coon Lake Rd. W.
Webberville, MI 48892

http://groups.yahoo.com/group/skysailingtowing/message/4730
Instruments on the base tube

Tracy Tillman - 2005/02/22 21:41:30 UTC

We can't make this activity perfectly safe, but we should never stop trying to make is safer.

I love it when idiots repeatedly write stuff that keeps confirming and reinforcing the takes you had on them to begin with.