weak links

[Flying Lobster]

I don't pay much attention to the Tad freak-show, but I do disagree with Steve's comment about towing being really safe compared to mountain flying. The mere fact that there are so many more variables and mechanics involved in towing a hang glider than in launching off a mountain make towing a more complicated, and potentially, more dangerous process. There are no other humans involved when you launch of a mountain. So when you add the human-factor, the possibilities of mechanical failure, and the other variables involved, I believe towing is more dangerous. Having said that, I do both and consider the risks of both types of flying acceptable in comparison to the rewards involved.

JR

JR dude--I used to think the same way--but after 11 years of aerotowing I really wonder if the frequency of launching aerotow versus Ft launching really supports that arguement that one method is inherently more dangerous than the other. I strongly suspect not--but I can't prove it.

marc

PS: You're wrong about a short-pack revision to the Sport 2 coming out any time soon. See all the trouble you caused on the OzReport!

I didn't say they were making a short-pack version of the Sport 2. I simply reported a conversation I had with Steve Pearson at the 2006 WW Wallaby party in which he told me that was his next project. Maybe it got moved to back-burner or wasn't feasible, but he really did tell me that.

I have aero-towed, off and on, since the late 80's. First with Bill Bennett and John Pattison behind a trike that flew way too fast and then later at the Wallaby/Quest flight parks (and now Highland, too). I still believe that the added complexity, mechanical and human variables tend to permit more things to go wrong and, therefore, towing is somewhat more dangerous than foot-launching, but I have no statistics to prove that and consider them both acceptable risks. I used to have this discussion/debate with Bill Bennett all the time. Then he went and got himself killed to prove my point.

JR

Jeez--I wonder if Bill knew his accident would be supporting so many points of view he'd be rolling over in his grave. But I'm going to leave that one lie, thank you.

I agree that towing in general is more complex and thus requires "more checks and balances" to ensure safety margins are maintained. But the added elements of complexity and human interaction do not in and of themselves make the method more dangerous--by that line of reasoning flying commercial airlines would be a preposterously risky activity. And the probability of launching unhooked is certainly far less when aerotowing.

As for Steve at WW--you know he is always working on improving everything in Wills Wing's line up. As soon as someone "lets the cat out of the bag" the rumors fly and you get stuff like that guy who thought his sport 2 would be worthless and felt he was being ripped off. What the heck--I guess the still benefit from the publicity anyway.

marc

[XCanytime]

Marc,
At one time flying commercial airlines was a helluva lot more dangerous than it is today. Of course you can do the statistics, so statistically you may be more likely to die from a lightning strike or a car crash than a commercial airline crash. So by that logic, flying a commercial airliner is "safer" than driving. But here is another way of looking at it: when sh*t hits the fan with a commercial airliner, like Sao Paulo, survival is highly unlikely versus a car crash or getting killed by lightning.
Applying that logic to towing versus mountain flying, let's say sh*t hits the fan right on launch (which is where sh*t does hit the fan!!) with the two methods of getting airborne. Lockout at low altitude cratering in versus (around here) getting treed or otherwise. Which is safer? Don't really know. The statistics (I don't have them) would show one way statistically is safer than the other. But what has to happen in both methods to get out of the bad scenario? Towing depends on a few more things than just maybe a simple weight shift and pull-in (the simplest correction in mountain flying). A release has to work if things get past the point of no return (if the pilot's release doesn't work the tug pilot's release better work) and there has to be sufficient altitude to recover from a bank angle that is undesirable. And the ground generally does not fall away from you at a towing location like it does on a mountain slope (quickly giving you vertical distance between yourself and solid objects).
I am not saying one method is better to get airborne than the other. It's just another choice facing the local pilot.

Bacil

[Tad Eareckson]

What Tad has consistently has recommended has been that EVERY qualified AT pilot tow, not at one end or the other, but DEAD CENTER IN THE MIDDLE OF THE 0.8 TO 2.0 SAFE RANGE - 1.4 Gs. The highest number anyone will be able to quote is 1.44 which, in the example cited, allowed a negligible amount of slop dictated by steps of available graduation.

(Tad responded to a question Brian posed on theory but immediately qualified his answer. That obviously was not a recommendation but has been disingenuously portrayed as such in a tactic similar to the one which resulted in a headline reading "How can 57 million Americans be so stupid?")

The only other deviation from that high water mark has been towards or possibly beyond the low end of that range, as recommended by Donnell Hewett for a pilot new to towing or (as in Hugh's case) a mode thereof.

Jim has left the impression that if a 350 pound comp glider with a two point bridle shows up he will refuse to tow him with anything heftier than a 0.7 G weak link but is perfectly OK hauling a skinny Hang II kid on a little Falcon at 1.5 Gs.

Tad has specifically and repeatedly said that unnecessary weak link breaks will NOT kill you. They can, have, and will result in broken downtubes, minor injuries, ruined flying days, lines lengthened enough to lock people out of windows, lowered competition scores, pissed off pilots, wasted fuel, and higher towing costs.

Tad has not attacked, just counterattacked. Find some of Tad's nastiness and check what preceded it. Check Jim's first couple of posts for examples of tact and interest in establishing and maintaining an academic discussion. I did have a conversation at Ridgely with a reader who had been stunned by the rudeness with which I was treated as this thread started rolling.

Tad has not called anyone names. The only name calling I recall in this thread was something about a "missing link".

Yep. When a glider goes down on tow Tad does the NTSB thing and sucks up every shred of information he can get his hands on and occasionally winds up with some insights that a lot of other people don't have. Tad also welcomes any discussion or debate on the issues of a higher caliber than the Tad's-full-of-shit sort of thing.

Tad has an old glider in nice condition that thermals with the best of them and gets killed at bar pulling time. But Tad has it fitted with tow systems which are eons ahead of anything out there. They are efficient light, strong, clean, and oozing with redundancy and can be actuated with little more than a thought. Tad doesn't have any problems with his towing - Bill, Mike, Mike, Robin, Holly, Arlan, Jeremiah, and anyone who has ever reached for a secondary or popped a weak link do.

Tad was a Basic Instructor back, what, before Jim was born? Tad's got about three and two thirds hundred hours of airtime, a handful of dune flights in excess of an hour (or two), and was a Smithsburg site record holder (before Marc cracked it). Tad was at Ridgely its first day of operation and was looking down at the runway from over eight grand two days later, has made it out 37 miles, has punched the clouds a few times, and has stayed up long enough to start falling asleep. (Tad was also at the tow farm long enough to see a Dragonfly flip on its back (and thus prop) in an incident precipitated by a chintzy secondary bridle disintegrating.)

And none of that has the slightest bearing on this issue 'cause this has nothing to do with flying skill and everything to do with physics.

Donnell Hewett was not a tow pilot. He was/is a physicist. He had enough brains to look at the tow systems and figure out how to do them right. He got attacked and censored. It's a pretty good bet that people died who didn't have to. Les King - of the USHGA BOD at the time - was big enough to say (to me at Sport Flight) "We were wrong."

None of what the aforementioned or I have done requires ANY ability to fly a glider or anything else. And no amount of flying experience automatically qualifies anyone to evaluate these systems.

Marc, when you say "we say it's fine where it is." - is that the Royal We? 'Cause Jim just cited something between a hundred and a million comp pilots who definitely don't say it's fine where it is - and have been denied the right to do anything about it.

This is not "weird" science - this is simple and solid. Only one calculation requires a bit of trig and for that you can substitute:

tow line tension equals twice bridle tension over 1.15

Now it's all grade school arithmetic.

I really appreciate your comments on my systems and there do happen to be a few people using them. But at the rate folk are catching on I'm gonna have been dead a long time before anything significant snowballs. So I'm not gonna shut up and go away as long as people are reading, questioning, and challenging.

I also appreciate it when you raise a legitimate concern or disagreement. But if I come back with the logic, numbers, data and/or question I'd like to hear it acknowledged, answered, countered. And when a statement is attributed to me I wanna see quotation marks - encompassing all relevant content.

This hasn't been a lot of fun and it needs to be a two (or twelve, whatever) way street.

With respect to weak link implementation...

1. If you put the weak link between the tow line and a two point bridle you only need a few of them to run the operation and the bridle can't wrap after a weak link break.

2. It's not worth it to use this concept on a bridle which is engaged by a spinnaker shackle 'cause it'll get chewed up.

3. If you tow one point you can use the shear link cheap and easy and keep it with you.

These weak links maintain a reliable rating indefinitely and do not wear with use - 'cept for maybe the ones on the back end of the tow line as a result of dragging.

Yeah, I can get a bottom end Falcon down to 0.78 Gs. With a loop of Greenspot on the end of a two point bridle you're looking at 1.50.

But, like Brian said, we don't seem to be killing a lot of Karen/Ayeshas with the 1.4 target I'm shooting for so - why bother?

Yeah Brian, fabrication of the version of this thing that goes on the tow line is labor intensive. But you've only gotta do it once. Cutting a length of Greenspot and tying it in a loop is a relative non issue. But you gotta do zillions of them. And when a tug has to do a go-around, a glider has to be recovered (and, occasionally, repaired) and restaged, and there are a bunch of people who've already killed a third of the day making it to the line baking in their harnesses, the construction inconvenience/expense consideration fades pretty fast.

Yeah, my fuse has been a bit short through a good chunk of this but I've had a lot of things coming at me from a lot of different directions. (I've also had a backlog of a few items not on this thread.) And you've been too tied up lately to do moderator duty.

Yeah Steve, I'm pushing hard for what I think you need, but I can be worn down. Case study - PK...

I tried to wear him down and got close once or twice. He managed to temporarily get rid of me by saying that he's light and isn't breaking stuff very often. I think he's 250 and the Greenspot on his one point gives him 1.12.

I can compromise and put him more reliably at that rating with the next to lowest link of that flavor.

I'd just as soon not go too far down from 1.4 'cause I've got the plus/minus twenty percent tolerance thing to worry about.

(Steve, what did I give you? Black/Orange? And what do you weigh? Gimme that and I can tell you tow line tension and Gs. I guess you must have gotten port and starboard equalized since we last crossed paths?)

[Tad Eareckson]

More on the Royal We thing.

"Tad says we go to the upper end, we say it's fine where it is."

Again, Tad says go to the middle, but...

It's fine where it is FOR WHOM? Karen, me?

Let's say that using a 1.40 G weak link is as insanely dangerous as Jim contends and 0.79 is is perfect.

SO YOU'RE GONNA KILL KAREN AND LEAVE ME UNSCATHED?! Let's take a poll - naw, don't bother. Reality check time.

Jim also makes the point that the glider driver isn't the only one on the line and he didn't ask to be a "TEST PILOT" and subject himself to gawd knows what unpredictable horrors might await him as a result of a double loop of Greenspot on a bridle. But, hey, as long as there are two people dangling behind that configuration, no problem, do it thirty times a day, hardly notice when the thing pops...

Right?

That's some of what's wrong with the wheel.

When I first kissed the Greenspot bye-bye, I figured I'd just carefully duplicate its strength with the more reliable version. Can't get in trouble that way, right? It would have put me at around the bottom of the range and I cheated an extra stitch or two.

As I started figuring that, as Steve just expressed, that there was no way I would be counting on the weak link as an emergency release (which no one can afford to do anyway), goal number two was to take the strength up as high as I could and still leave the weak link near the front end of the tow line intact. So I flew at 1.12 Gs for a while.

Stage three, I said "Screw this, I want a 1.4 G weak link and what's up front is not my problem. I'm just responsible for this aircraft."

So as things stand, if I exceed about 1.29 Gs I'm gonna end up with 250 feet of Spectra. OK, happens with the tandems every now and then, I'll deal with it. But I don't expect that to happen 'cause I've gotten off tow at under 0.8 Gs in a lockout before and I'm real confident that I can do it again.

I'd like to see the strength up front go up closer to what folk thought it was to begin with but that hasn't happened yet.

The tug driver doesn't really have to worry about what's on the glider 'cause he's got his aircraft protected with whatever he wants and, if he doesn't like the reflection in the mirror, he's also got a lever to take care of that problem.

Marc, from you...

>
Ain't no device going to mitigate the fact towing in turbulence is riskier and takes more piloting skill. Changing your breaking pressures is only going to shift the bar on the decision set that the pilot must make in those split seconds during initial tow. Tad is correct in one statement--the weaklink does protect the plane, especially during roll-out and liftoff. Upping the load limit means more trust will be placed in the towed pilot in doing the right thing. keeping the line under higher pressure at initial lift-off, IMO, will increase the probability of lock-outs over the broad range of pilots and conditions, while increasing the risk to the tug as well.
<

Yeah, getting slammed in in those first split seconds is the nightmare scenario. I've thought and worried about it for years.

OK, if there's no turbulence it's not worth going up, so we're going to be towing in turbulence.

I don't think anything catastrophic has ever happened in the first split seconds - 'cept maybe having your bridle routed under the cart tubing (a finger on the trigger is about the only thing that might help you with that problem). The bad stuff happens in the course of seconds.

And, I said this at the time but again... The probability of a lockout cannot be increased by beefing up the weak link - only the extent.

The tug is always protected by its weak link, independent of your selection.

And both pilots have the ability to actuate the release long before the weak link can kick in - once somebody makes a decision.

Yeah, the towed pilot has to do the right thing - just like an untowed pilot often has to make instantaneous reflexive corrections clearing the slot or putting it down in the primary at Woodstock.

[Flying Lobster]

Marc,
At one time flying commercial airlines was a helluva lot more dangerous than it is today. Of course you can do the statistics, so statistically you may be more likely to die from a lightning strike or a car crash than a commercial airline crash. So by that logic, flying a commercial airliner is "safer" than driving. But here is another way of looking at it: when sh*t hits the fan with a commercial airliner, like Sao Paulo, survival is highly unlikely versus a car crash or getting killed by lightning.
Applying that logic to towing versus mountain flying, let's say sh*t hits the fan right on launch (which is where sh*t does hit the fan!!) with the two methods of getting airborne. Lockout at low altitude cratering in versus (around here) getting treed or otherwise. Which is safer? Don't really know. The statistics (I don't have them) would show one way statistically is safer than the other. But what has to happen in both methods to get out of the bad scenario? Towing depends on a few more things than just maybe a simple weight shift and pull-in (the simplest correction in mountain flying). A release has to work if things get past the point of no return (if the pilot's release doesn't work the tug pilot's release better work) and there has to be sufficient altitude to recover from a bank angle that is undesirable. And the ground generally does not fall away from you at a towing location like it does on a mountain slope (quickly giving you vertical distance between yourself and solid objects).
I am not saying one method is better to get airborne than the other. It's just another choice facing the local pilot.

Bacil

Interesting argument--but sorry, I think your points are, like mine, subjective at best.

I've heard speculation about this low-level lockout stuff while aerotowing and not being able to release--I think this event is incredibly rare and suspect that pilots get gusts and PIOs mixed up as lockouts--but whatever.

I could easily argue that aerotowing is a FAR more reliable way to set proper AOA and necessary airspeed than footlaunching. The fact that your launch area and LZ are one and the same (and generally flat and very large) I could also argue is FAR safer than crashing through the trees into a steep mountain slope in case the glider takes off and gusted putting it into a roll and turn into the mountain. I've seen this happen to MANY pilots--including the best--and it has KILLED and injured many pilots over the history of our sport. I have NEVER seen a lockout aerotowing while lifting off in the first 100 ft or so.

I agree with Jim's basic premise that there are inherently more items to check when aerotowing--so at some level there is a greater risk of human error being introduced into the system if all people involved are not absolutely careful and professional about what they do. And I have seen aerotow operations--big ones even--that can be lax about maintaining that degree of care. But if those systems are being operated carefully and professionally--then the actual method of aerotowing as a means of getting a glider into the air I do not believe is any less safe than footlaunching. And many pilots might, like Steve, feel its actually safer. In truth, the biggest factor influencing the safety of a launch--whether it be aerotowing or footlaunching--I believe is THE PILOT.

Lets talk about something else not based on opinions--like wheels, full-face helmets, or even weaklinks, eh?

marc

[jimrooney]

We've descended into FL vs AT and Tad is no referring to himself in the 3rd person?! Hahahahaha
Wow, this is really turning into a freakshow.
Ok, it's always been a freakshow, but it's taken on a whole new level.

I'm with Marc... hrm... lets see what else....
Wheels vs no Wheels
FLPHG vs FL
Insurance
USHGA vs USHPA
Fullface vs Saladbowl
Double hangstrap vs Single
Zero pressure releases
Marketing
Accident statistics
Rigid vs Flexie
Drogue Chutes!

Be creative.
There's so much to piss and moan about! Why get bogged down on just one?

HAHAHAHAHAHAHAAHAHAHAHA

[Flying Lobster]

We've descended into FL vs AT and Tad is no referring to himself in the 3rd person?! Hahahahaha
Wow, this is really turning into a freakshow.
Ok, it's always been a freakshow, but it's taken on a whole new level.

I'm with Marc... hrm... lets see what else....
Wheels vs no Wheels
FLPHG vs FL
Insurance
USHGA vs USHPA
Fullface vs Saladbowl
Double hangstrap vs Single
Zero pressure releases
Marketing
Accident statistics
Rigid vs Flexie
Drogue Chutes!

Be creative.
There's so much to piss and moan about! Why get bogged down on just one?

HAHAHAHAHAHAHAAHAHAHAHA

You forgot paragliders--the biggest crisis facing the world next to global warming.

marc

[deveil]

More on the Royal We thing.

"Tad says we go to the upper end, we say it's fine where it is."

Again, Tad says go to the middle, but...

It's fine where it is FOR WHOM? Karen, me?

Let's say that using a 1.40 G weak link is as insanely dangerous as Jim contends and 0.79 is is perfect.

SO YOU'RE GONNA KILL KAREN AND LEAVE ME UNSCATHED?! Let's take a poll - naw, don't bother. Reality check time.

Jim also makes the point that the glider driver isn't the only one on the line and he didn't ask to be a "TEST PILOT" and subject himself to gawd knows what unpredictable horrors might await him as a result of a double loop of Greenspot on a bridle. But, hey, as long as there are two people dangling behind that configuration, no problem, do it thirty times a day, hardly notice when the thing pops...

Right?

That's some of what's wrong with the wheel.

When I first kissed the Greenspot bye-bye, I figured I'd just carefully duplicate its strength with the more reliable version. Can't get in trouble that way, right? It would have put me at around the bottom of the range and I cheated an extra stitch or two.

As I started figuring that, as Steve just expressed, that there was no way I would be counting on the weak link as an emergency release (which no one can afford to do anyway), goal number two was to take the strength up as high as I could and still leave the weak link near the front end of the tow line intact. So I flew at 1.12 Gs for a while.

Stage three, I said "Screw this, I want a 1.4 G weak link and what's up front is not my problem. I'm just responsible for this aircraft."

So as things stand, if I exceed about 1.29 Gs I'm gonna end up with 250 feet of Spectra. OK, happens with the tandems every now and then, I'll deal with it. But I don't expect that to happen 'cause I've gotten off tow at under 0.8 Gs in a lockout before and I'm real confident that I can do it again.

I'd like to see the strength up front go up closer to what folk thought it was to begin with but that hasn't happened yet.

The tug driver doesn't really have to worry about what's on the glider 'cause he's got his aircraft protected with whatever he wants and, if he doesn't like the reflection in the mirror, he's also got a lever to take care of that problem.

--------------------------------------------------------------------------------------
so, i pretended that i was an editor and rewrote some things, believing that i did not *materially change* anything and expanded some things to include that which *i* thought was self evident, implied, and that you would agree with.

however, that then left this statement/conclusion inexplicable.

"That's some of what's wrong with the wheel."

----------------------------------------------------------------------------------------



"i, tad, say we go to the upper end ,others say it's fine where it is."

Again, Tad says go to the middle, but...It's fine where it is for whom?

Let's say that using a 1.40 G weak link is as problematic as some contend and 0.79 is a good, working compromise.

i contend that that compromise puts lighter weight pilots at greater risk, a risk that i believe to be unnacceptable and unneccessary.

a tug pilot arguably(?) is more frequently exposed to the risks of towing - he's always the guy on the other end of the line. doing this as a business requires that other people have confidence in him. thus he's probably (justifiably?) very wary of subjecting his reputation, himself or others to ideas/techniques/equipment of which he doesn't have confidence.

*That's some of what's wrong with the wheel.*

When I first kissed the Greenspot bye-bye, I figured I'd just carefully duplicate its strength with the more reliable version. Can't get in trouble that way, right? It would have put me at around the bottom of the range and I cheated an extra stitch or two.

As I started figuring that there was no way I would be counting on the weak link as an emergency release (which no one can afford to do anyway), goal number two was to take the strength up as high as I could and still leave the weak link near the front end of the tow line intact. So I flew at 1.12 Gs for a while.

Stage three, I said " I want a 1.4 G weak link and what's up front (with the tug pilot referenced above) is not my problem. I'm just responsible for this aircraft." - not the whole business of running a tug with people on a line behind me (again, see tug pilot referenced above).

So as things stand, if I exceed about 1.29 Gs I'm gonna end up with 250 feet of Spectra. OK, happens with the tandems every now and then, I'll deal with it. But I don't expect that to happen 'cause I've gotten off tow at under 0.8 Gs in a lockout before and I'm real confident that I can do it again.

I'd like to see the strength up front go up closer to what folk thought it was to begin with but that hasn't happened yet.

The tug driver doesn't really have to "worry" about what's on the glider ("worry" is in quotes because of course he does worry, it's part of what people count on him to be doing, otherwise he'd have to be pathological (to not worry)) 'cause he's got his aircraft protected with whatever he wants and, if he doesn't like the reflection in the mirror, he's also got a lever to take care of that problem.


-------------------------------------------------------------------------------------


'did this as an exercise to explore the idea of what other people "hear" you writing is not the same as what you "hear" you writing.

not trying to be tricky here. am vowing to myself that i'll not follow up with anything, regardless.

(still gotta press the 'submit' button . . . gulp . . .

[deveil]

shit! my dog lunged at the keyboard! i wasn't gonna do it! shit! come here you damn dog . . . !

[XCanytime]

"In truth, the biggest factor influencing the safety of a launch--whether it be aerotowing or footlaunching--I believe is THE PILOT."

I have to disagree with you Marc. With aerotowing the pilot is one link in the chain. The chain has 5 links: (1) the tug pilot (2) the tug pilot's release (3) the weak link (4) the tow pilot's release (5) the tow pilot. If chain link #5 is having a bad day at low altitude, then chain links #4, #3, and #2 better work, in that order. There is more influencing the safety of what is going on than just the pilot. Forgot a 6th link: the tug engine, another variable affecting the safety. Mountain launching has one chain link: the pilot. It's all on the pilot to determine the safety of the launch.

Bacil

[Flying Lobster]

"In truth, the biggest factor influencing the safety of a launch--whether it be aerotowing or footlaunching--I believe is THE PILOT."

I have to disagree with you Marc. With aerotowing the pilot is one link in the chain. The chain has 5 links: (1) the tug pilot (2) the tug pilot's release (3) the weak link (4) the tow pilot's release (5) the tow pilot. If chain link #5 is having a bad day at low altitude, then chain links #4, #3, and #2 better work, in that order. There is more influencing the safety of what is going on than just the pilot. Forgot a 6th link: the tug engine, another variable affecting the safety. Mountain launching has one chain link: the pilot. It's all on the pilot to determine the safety of the launch.

Bacil

Didn't I already agree that there are more factors involved in aerotowing that can potentially introduce human error? If I didn't, I'll say it again--yes. But that still doesn't prove that just because the potential is there that ON AVERAGE AEROTOWING IS MORE DANGEROUS THAN FOOTLAUNCHING. It simply means more people are involved that have to work together as a team to see to it that things go safely. I could even flip your argument and say the probability of a contentious tow operator preventing you from flying in dangerous high winds is better at a towpark than it would be, let's say (hypothetically speaking of course ), if the same pilot decided to go to a mountain launch and fly in high, gusty winds on a low performance glider where he is the only decision maker. But I think your last sentence is in agreement with what I'm trying to say.

Me personally--I don't care--my favorite method of launching is the one that gets me into the air--and it's the most dangerous. I hope I never have to blame someone else or my equipment for my lack of abilities (although that might be why I keep buying new gliders ).

marc

[XCanytime]

Marc,
The first part of your flip will remain hypothetical because it will never happen. And I did not say that on average one method was safer than the other. All I said was that I disagree with you stating that the pilot is the main determinant of the relative safety in aerotowing. That is all. Nothing more, nothing less. Only mathematical analysis of failure rates of the mechanical links in the aerotowing chain will determine the overall MTBF rate of the aerotowing system, and where the real "weak link" really is. And the MTBF has nothing to do with human error.

The main thing that allows pilots to fly another day is to always leave yourself an out, whatever that out may be.

Bacil

[Flying Lobster]

Marc,
The first part of your flip will remain hypothetical because it will never happen. And I did not say that on average one method was safer than the other. All I said was that I disagree with you stating that the pilot is the main determinant of the relative safety in aerotowing. That is all. Nothing more, nothing less. Only mathematical analysis of failure rates of the mechanical links in the aerotowing chain will determine the overall MTBF rate of the aerotowing system, and where the real "weak link" really is. And the MTBF has nothing to do with human error.

The main thing that allows pilots to fly another day is to always leave yourself an out, whatever that out may be.

Bacil

I think we're playing word games here. I said the biggest factor determining safety for any launch method is the pilot--you say it isn't in the case of aerotowing. By this, I take it that the other factors in this chain of links in aerotowing, either singly or collectively, are a bigger factor in determining a pilot's safety (if you meant something else it isn't clear to me what that is). Tugs must all be FAA registered, N-numbered and annually inspected by a licensed inspector to certify their airworthiness. I don't think the same can be said of most hang glider pilot's gliders. Most reputable aerotow operations are in business because they have a vested interest in maintaining high standards of safety and easy access to launching--at every link of the chain.

We've expended a whole lot of angst over this whole towing safety thing--starting with Tad's weaklink jihad. I'd like to ask--when having problems with landings--doesn't it make sense to look at your gear, adjust it properly, then go out and practice your landings to improve? Wouldn't it make just as much sense to go out and practice releasing at various stages of a tow--including rolled hard (while high, of course) or low down just to see what it's like and get better at dealing with those potential "safety weak links?"

marc

[jimrooney]

Ha
We do that with all our students.
You can't solo till you've been through the ringer.

[Flying Lobster]

Marc,
The first part of your flip will remain hypothetical because it will never happen. Bacil

What, that tow operators will advise/prevent you from launching even if you want to? Happens all the time. If you mean flying a low performing glider in the mountains in strong conditions--that happens all the time too." (I know I've flown my Falcon in 35 mph winds up here! )

marc

[XCanytime]

"I said the biggest factor determining safety for any launch method is the pilot--you say it isn't in the case of aerotowing. By this, I take it that the other factors in this chain of links in aerotowing, either singly or collectively, are a bigger factor in determining a pilot's safety."

Marc,

Exactly ! That was the point I was trying to get across. As for the hypothetical situation you described in the first part of the flip, it will never happen to me specifically, but that's by choice.

And Tad is trying to improve the MTBF of the aerotowing system with his reliable releases, right Tad ? Oops .

Bacil

[Flying Lobster]

I've cored sink. Time to pull VG and go on glide!

marc

[Tad Eareckson]

Sorry, took a bit of time off to work on photos of the new bridle/weak link designs. They're up at:

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

I'm calling them "Ribbon Bridles". I'd prefer not to admit how long it takes to stitch together three or four ten foot strands of low stretch line but I've got a pretty good idea that it will be impossible to wrap these things.

From Marc, near the beginning of the discussion:

>
You toss around load limiting figures without any real asociation to breaking strengths and desired load limitations.
<

Odd, coming from someone in the faction which has so steadfastly maintained precisely that approach.

Jim actually has no idea when I thought of putting the weak link on the tow line instead of the bridle. I didn't think of the idea at all - I, however, had been aware of but quickly discarded the concept years before Jim ever got a carabiner anywhere near a glider. Until last year I had assumed that a weak link had to be a loop of string and didn't like the idea of dragging and degrading something that could determine the duration of my tow.

Jim doesn't define who "us simpletons" were and why they rejected the configuration. Peter Birren, the individual Marc recommended for checking my arithmetic, is a strong advocate and I'm pretty sure Donnell Hewett is so rigged when he gets behind a tug.

Somewhere there's a photo of the 2004 edition of Charlotte Baskerville taken immediately after a hop with Sunny at the wheel. Let's use Photoshop to replace the latter with Adam. So now we're getting to the neighborhood in which a tandem glider with a light pilot and seven year old passenger might weigh less than a bladewing heading for Ocean City.

So I'm wondering why it's insanely dangerous for a heavily loaded solo glider to use a double loop of Greenspot but not a lighter kitecyle built for two.

A single loop on the end of a two or one point bridle might buy you around 243 or 280 pounds of tow line tension respectively.

The following is a list of known rabid maniacs who tow with "strong links" listed in order of and along with their maximum tow line tensions in pounds (sorry guys).

323 - Tom
348 - Victor
350 - Sunny
351 - tandems
378 - Steve Padgett
400 - Christian
420 - Hugh
420 - Steve Kinsley
470 - Tad

(Note the inverse relationship between pounds and IQ.)

Tom gets an asterisk. I think he was using a loop of 150 but has run out of that flavor of string.

For all the work I've put into this stuff, a double loop of Greenspot (as I just wrote the latter Steve who recently had another single pop for no reason at half a grand) ain't a bad one-size-fits-all solution.

The respective two and one point ranges are around 174 and 200 to 435 and 500 pounds. But if you have the opportunity to hit the middle...

I think one reason that the concept of a weak link having to be something on the ragged edge of failure under normal tow loading has been able to metastasize for so long is the availability of the USHGA Aerotowing Guidelines.

Go to the national organization's web site and try to locate that information. I've been sucking up everything I can find for years and it wasn't until half past April when I registered and was cleared for membership in an obscure tugs discussion group that I was able to get my hands on a PDF file. Prior to that I figured we should be duplicating sailplane specs.

No oops, Bacil. Well, a little oops. I'm not trying to increase the MTBF - I've done it - often with, of course, the help of others whose concepts I've ripped off and expanded upon. Now I'm just making the presentation.

The F, of course, doesn't have to be a Fatality or Fracture. It can just be an "Aw, Fuck - back in line."

One easy way to increase the MTBF is to increase the airtime to launch/landing ratio. On 2007/06/07 Yuriy Koziy had to come down prematurely. The lift, not the weak link, gave out but it just as easily could have been a case of string fatigue. "Landed" - in the wrong place - two faired downtubes, a smashed Flytec case, and hurt enough to end his participation in the ECC.

Gotta disagree with you about the chain links thing - you're making it too complicated.

For the purpose of this discussion, lemme cheat a little and throw out landing in tug wake.

The stuff that you don't own can't hurt you. To reiterate the list - everything from the tow ring forward - the tug and its pilot, engine, release, weak link, tow line, and ring. If you crater in it won't be 'cause the tug fell apart, the driver decided to kick in the turbocharger, dump power, and/or fly under the power lines, the engine ran out of gas or seized, the tow line or weak link broke or didn't, or the tow line wrapped or carabiner hooked on to your wires.

It'll be 'cause you screwed the pooch.

If you screw up just off the side of a mountain - you're on your own.

If you screw up just off the cart - the tug can do things to compensate and maybe bail out your sorry ass but it's not responsible for the predicament into which you put yourself.

Bill and Mike didn't die because of "an inexperienced tug pilot who dumped power when he shouldn't have". They died because they stalled the glider.

The tug is just there so you can have fun. If the fun starts dissipating there's no reason you have to keep following it.

[jimrooney]

Here we go again with more of the "you're better on tow in a bad situation" BS.

Your assumptions about what we're doing on the tug end are wrong.
The #1 thing I can do for you just off the ground is GIVE YOU THE ROPE.

Whatever's going on back there, I can fix it by giving you the rope. Any work I do is to save the tow and get you back in line... not to save you. I do this only when I think it's safe to do so. When I give you the rope, I've determined that continuing the tow is putting either you or me (or both) in jeopardy and I'm trying to save you (or me).

[brianvh]

Once again I see no contradiction between what the two of you are saying. Tad said:

"If you screw up just off the cart - the tug can do things to compensate and maybe bail [you] out .... but it's not responsible for the predicament into which you put yourself.

The tug is just there so you can have fun. If the fun starts dissipating there's no reason you have to keep following it."

Translation: If something's going wrong, the HG pilot should get off tow.

Jim said:

"Whatever's going on back there, I can fix it by giving you the rope. Any work I do is to save the tow and get you back in line... not to save you. I do this only when I think it's safe to do so. When I give you the rope, I've determined that continuing the tow is putting either you or me (or both) in jeopardy and I'm trying to save you (or me)."

Translation: If something's going seriously wrong, the TUG pilot will get off tow.

Sounds like the same thing from opposite ends of the rope. Nobody's counting on the weak link anyway.

I've already restated the whole argument as whether the link should be on the high or the low end of the broad spectrum we've been happily using for years. And once again, since nobody's been worrying about lighter pilots, I think Tad is right to aim for the high end, BUT ONLY if we start scaling the weak link strength for total mass. I didn't come to this realization until fairly late in the thread, and wouldn't have if I wasn't such a lightweight.

Unless there's something particularly amusing to comment on, as far as I'm personally concerned the argument and thread is done. Somebody might flame me back into posting...that's just another form of amusement.

[deveil]

form of amusement?

well, any excuse to put off doing what i've been doing.

[jimrooney]

Not we're not saying the same thing.

Tad's saying that I can fix things without giving you the rope.

I'm saying that I can lessen the effects of your screwups. I don't "fix" anything, I just keep you from smashing into the ground by lengthening the time between you and lockout. You have to "fix" things, I just give you a second (from my bag of safety!) for you to do it in.

It sounds similar, but there's a world of difference.
Ya'll need to think long and hard about cutting into my margin of safety... cuz that's what you're talking about.

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

[Tad Eareckson]

I so do love it when I see quotation marks around a statement which is pretty much the opposite of something I've written.

Thank you, Brian, for actually reading what I've said before commenting and for restating same.

There was a glaring omission from a sentence in my previous post which I will now repair with an amendment.

If you crater in it won't be 'cause the tug fell apart, the driver decided to kick in the turbocharger, dump power, and/or fly under the power lines, the engine ran out of gas or seized, the tow line or weak link broke or didn't, the tug's release was or wasn't actuated or jammed, or the tow line wrapped or carabiner hooked on to your wires.

(...the tug's release... - to save the trouble of going back for a comparison)

Now lemme say some more of what I'm saying...

Yes, there most assuredly are bad situations in which one REALLY needs to stay on tow and not have someone on the other end of the line whose knee-jerk response to every undesirable situation is to squeeze a lever.

Bill/Mike.

At some point during that tow that glider entered the living-on-borrowed-time envelope. It was low and slow. Assuming that the trike was running with a full head of steam - and I'm pretty sure it was - the action that its driver needed to take was to pull in and maintain said steam. That didn't happen.

If tow line tension gets reduced or lost because:

the tug trades in some speed for altitude
the RPMs diminish or stop advertently or in-;
a lever or lanyard is hit or pulled; or
a weak link pops

the glider goes from having an angle of attack way too high to having one way way too high. Need I continue?

1996/05/11. Rerun - but apparently one needs to say things over and over.

Four glider pilots - one of them cringing behind a piling, another running full tilt for shore, a third locked out and about to slam into the dock right where Ray Dunmyer is cowering and yours truly had been standing, a fourth applying full throttle to the winch.

Contrary to what the crowd present is anticipating, the glider is able to benefit from the reduced AOA provided by Jonny Thompson enough to get the starboard wing tip flying more on par with its mirror image and Lawrence Battaile not only survives but is able to get up and make a few passes soaring the tree line at Colington Island.

Neither a cut engine, flimsy weak link, three-string release, hook knife, nor philosophy of a rope donation being a panacea would have been been a positive contribution to the situation.

[brianvh]

Now THAT's interesting enough to suck me back in.

Jim...I concede that Tad's saying that staying on tow is sometimes healthier than getting off. Wasn't expecting that, you read it right I read it wrong.

But I see what he's saying. We tow-launch with a nose angle that in nearly all other circumstances would send us into a stall. The only thing that keeps us going is a tug that obstinately refuses to let the increased drag slow us down so much we lose lift. We're going fast enough when we release from tow that we recover from stall before we drop below 1 g of lift, so don't go into a dive.

Maybe if the nose gets too high releasing from tow is dangerous?

I leave this up to the very experienced tow-meisters to weigh in on. Except for the normally high nose angle I'd say being off tow is safer too.

[jimrooney]

Maybe if the nose gets too high releasing from tow is dangerous?

No.
If you're that high on tow, you've put ME in harms way. You're high, you've got altitude to save yourself with... you're driving me into the ground (at near stall speeds for me btw).

This is one of the prime situations where I will pass out ropes. The other is low level lockout, in case you're interested.

Rest assured, if you get the rope, you've scared the hell out of me. I don't want to smash into the earth, and I don't want you to smash in either.