Of course, a pilot could deliberately produce a stalled break at 200 lbs...the glider simply drops its nose to the free flight attitude and continues flying.
It works best in a lockout situation... if you're banked away from the tug and have the bar back by your belly button... let it out. Glider will pitch up, break weaklink, and you fly away.
in between.But if he is trying to limit his climb rate...
He PERSONALLY appreciates my EFFORTS and thanks me for keeping this issue before the hang gliding COMMUNITY then when his fuckin' hang gliding community goes into lynch mob mode he's never heard of me before.Donnell Hewett - 2008/11/05 21:23:39 UTC
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Let me begin by saying that I personally appreciate Tad Eareckson's efforts to improve the SOP of aerotowing as well as his suggestion to update the Skyting Criteria. It is through efforts like his that progress is made toward safer towing.
...
I believe that the first of these two conclusions is perfectly consistent with the point that Tad has been trying to make. And I thank him for keeping this issue before the hang gliding community.
Have ya stepped back and looked at the historical pattern?2019 Big Spring Nationals - 2019/07
Weaklinks of 140 and 200 pounds will be available and provided by the organizers. Weaklinks provided by the organizers must be used by the competitors.
...the LAST thing you wanted to have happen on a tow - even with uncertified and uncertifiable gliders, frame-only bridles, and easily reachable releases - was a weak link success of any kind at any time.Manned Kiting
The Basic Handbook of Tow Launched Hang Gliding
Daniel F. Poynter
1974
"The greatest dangers are a rope break or a premature release." - Richard Johnson
...everyone and his dog is using weak links just over sustainable tow tension for lockout protection. They'd successfully calculated that if you only killed twenty guys in stalls for the one weak link that blew during a lockout at two hundred feet or up then that was a good thing.Donnell Hewett - 1980/12
Now I've heard the argument that "Weak links always break at the worst possible time, when the glider is climbing hard in a near stall situation"...
All we know about them is that we've gotta use the ones provided by the organizers.Bart Weghorst - 2018/09/14 17:58:16 UTC
Please understand that the use of weak links does not prevent a lockout. They could help but they really serve a different purpose. I don't like to explain all this here because I think this forum is not a good medium to teach hang gliding subjects like these. When in doubt, consult an experienced AT operator and attend an AT course.
The 140 is obviously 130. Davis never could keep any numbers straight worth shit. He'd done that before with the 130. There are still thousands of AT assholes convinced that the chances of them surviving a smooth air tow up two hundred feet through the kill zone with a loop of 131 are about one in a thousand. But Davis said 140 so we'll use 140 'cause now his lowest allowable minimum for anybody is eight percent over his long-time maximum (and minimum) for anybody.2019 Big Spring Nationals - 2019/07
Weaklinks of 140 and 200 pounds will be available and provided by the organizers. Weaklinks provided by the organizers must be used by the competitors.
Yeah Cragin. The advancements we're making - 'specially now well into the Information Age - are truly astounding.Cragin Shelton - 2011/09/03 23:57:33 UTC
Nice Reference CitationDo you REALLY think that there has been no progress in knowledge about the practical applied physics and engineering of hang gliding in 37 years? OR that an early, 3+ decade old, information book written by a non-pilot is a solid reference when you have multiple high experience current instructors involved in the discussion?Manned Kiting
The Basic Handbook of Tow Launched Hang Gliding
Daniel F. Poynter
1974
"A bad flyer won't hurt a pin man but a bad pin man can kill a flyer." - Bill Bennett
"The greatest dangers are a rope break or a premature release." - Richard Johnson
How 'bout now, Zack? After another seven years of experience and evolution?Zack C - 2012/06/02 02:20:45 UTC
I just cannot fathom how our sport can be so screwed up.
Donnell Hewett - 2008/10/14 00:49:34 UTC
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In the case of hang gliders, platform towing is the only mode that consistently pulls downward throughout the whole flight when performed properly. All other forms of towing use forward pull at least during the early part of the flight. Therefore, they should all use a forward-pull weak link. Even platform towing can revert to forward pull if done improperly. I have seen cases where the glider would launch and the vehicle would race forward at high speed to lengthen the towline before the glider could gain significant altitude. This converted the down-pull into a forward-pull even while using a down-pull weak link. The glider climbed out at a 45 to 60 degree angle at low altitude. If the payout winch had jammed for some reason, the down-pull weak link would have broken, the glider would have whip-stalled, and the pilot would have been killed. I was appauled at such an operation. But it was SOP for that group. They had done it many, many times without a mishap.
http://www.hanggliding.org/viewtopic.php?t=36471Tad Eareckson - 2019/10/05 21:13:32 UTC
1. Yeah, I've seen that technique quite a few times. Probably was the subject of it a handful of times.
2. Before the glider COULD gain significant altitude? The whole idea was to get a lot of line out and it was nobody's intention for the glider to gain significant altitude during that phase.
3. The idea, if I recall / can reconstruct correctly, was to get the launch off safely, get a lot of line out, crank up the tension and slow down to slingshot the glider into the headwind gradient and have it climb steeply for the remainder of the tow and maximize efficiency for the limited runway length. And I believe this to be totally valid.
When I flew a lot of platform at Waverly, Ohio the truck would radio up for your release altitude and record it. So I believe they TOTALLY knew what they were doing on this and had the data to back it up.
KeLe - 2019/09/16 17:51:07 UTC
Hi to all again.
It seems, that we finaly have finished the construction and we are going to test the winch in the following days. We will travel to our friends to Hungary to do this. As I said before, they have a lot of experience on other types of winches but none on a payout winch. We plan to make some training on their winch first and than try some foot launch on our payout winch. If everything goes well, we will try platform towing too. Now I have a questions about the way to apply the towing force on platform launch. Should we apply the total force from beginning, or take off with a smaller force and set it bigger at a certain altitude?
Jim Gaar - 2019/09/16 18:17:09 UTC
Typically, for our system we start at a pre-set force (in our case it's 65-68 psi on the pressure gauge) on the brake of the tow rope drum and increase pressure towards the end of the tow, depending on conditions of the tow and requests from the pilot. We also slow down the speed of the tow vehicle as the drum pressure increases.
For us, the idea is to "pay out" as much line as possible in the beginning of the tow and then "sling" the hang glider and pilot up as the tow nears an end.
We also watch the speed of the line coming off the drum and attempt to keep it at a relatively constant rotation. You should hear from others as well on their particular methods. Good luck and let us know how you did!
Dallas Willis - 2019/09/16 18:41:18 UTC
I am a firm believer in the "slingshot" method. Set the tension low enough that the truck can tear off down the road at 50mph and the glider hovers around 100-200' above the ground. Once the truck has reached the halfway point of the road, it begins to slow down and continues to slow down until the winch is rotating as slowly as possible but does continue to rotate. The first half of the tow is just paying out line, the second half is when the glider begins to climb. This keeps the tension on the glider constant and low. It produces the same altitudes as cranking up the tension and driving slower but is far easier on the equipment (on both sides of the rope) and the human attached to the glider which is also far far safer overall.
Dallas Willis - 2019/09/16 18:42:43 UTC
Yeah what Blindrodie saidYou can search this forum for "slingshot" and you'll see other posts from the both of saying the same thing in other ways too.
Mike Bomstad - 2019/09/16 18:45:10 UTC
Start with a set tension. Foot launching or using the platform (We can take a rap on the rope and give it a couple of hard jerks to get it to pay out, rough idea of the initial tension if you dont have a gauge or don't know what the pressure means yet)
You dont want it too soft as the glider will lift off then lag behind the vehicle not climbing. (low and slow is no good)
Have an airspeed indicator on the front of the rig with clean air flow.
For us- a single surface flex about 25 mph, topless 30mph, rigid about 35 mph for take off airspeed.
As blindrodie said We also watch the speed of the line coming off the drum and attempt to keep it at a relatively constant rotation.
Donnell Hewett - 2008/10/14 00:49:34 UTC
6686
In the case of hang gliders, platform towing is the only mode that consistently pulls downward throughout the whole flight when performed properly. All other forms of towing use forward pull at least during the early part of the flight. Therefore, they should all use a forward-pull weak link. Even platform towing can revert to forward pull if done improperly. I have seen cases where the glider would launch and the vehicle would race forward at high speed to lengthen the towline before the glider could gain significant altitude. This converted the down-pull into a forward-pull even while using a down-pull weak link. The glider climbed out at a 45 to 60 degree angle at low altitude. If the payout winch had jammed for some reason, the down-pull weak link would have broken, the glider would have whip-stalled, and the pilot would have been killed. I was appauled at such an operation. But it was SOP for that group. They had done it many, many times without a mishap.
- And in all of hang gliding, nay all of any and every form of towed aviation on the planet, only the great Dr. Lionel D. Hewett, PhD is qualified to determine whether or not something's being done PROPERLY.In the case of hang gliders, platform towing is the only mode that consistently pulls downward throughout the whole flight when performed properly.
- What if the forward pull flight locks out immediately upon launch and the pull is virtually instantly identical to a properly performed platform launch relative to the wing? What weak link would we wanna adjust to if we had the ability to succeed soon enough to permit safe recovery?All other forms of towing use forward pull at least during the early part of the flight.
And sailplanes too of course.Therefore, they should all use a forward-pull weak link.
If it CAN...Even platform towing can revert to forward pull if done improperly.
...it WILL. It's only a matter of time. So then obviously for an Infallible Weak Link to be TRULY Infallible on platform it needs to be a forward-pull.Donnell Hewett - 2008/10/14 00:49:34 UTC
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But I still believe, "Anything that can go wrong will go wrong." It is only a matter of time.
- Then let's dial it down until it succeeds one out of four times - like we do for plain vanilla surface and aero. Problem solved.I have seen cases where the glider would launch and the vehicle would race forward at high speed to lengthen the towline before the glider could gain significant altitude. This converted the down-pull into a forward-pull even while using a down-pull weak link.
After they dialed up the tension with lotsa line out and the glider was cruising along at 75 feet. It would've been SO much safer if he'd just blasted off the truck bed at a 45 to 60 degree angle with his downward-pull weak link.The glider climbed out at a 45 to 60 degree angle at low altitude.
What reason? A zillion passenger jets a day blast of from runways too short for a total power failure on rotation to be survivable. The engines and relevant systems are a zillion times more complex than the fuckin' payout winch can ever dream of being. Yet such power failures are virtually nonexistent. And when we DO get incidents it was because of negligence somewhere up the line and somebody's head ends up on o platter. We can manage all this OK without Infallible Weak Links but we're incapable of running a drum with some rope on it that won't jam at or near takeoff?If the payout winch had jammed for some reason...
Well then. By this point in time they've obviously killed scores of pilots. How do you figure they're running the cover-ups so effectively? And if they're so effective at running the cover-ups then how is it that they so totally suck at keeping their payout winch running smoothly?...the down-pull weak link would have broken, the glider would have whip-stalled, and the pilot would have been killed.
And if you were appauled at such an operation it's a no fuckin' brainer that you never hopped on the back of the truck yourself. So how many flavors of towing have you actually engaged in? I'm guessing nothing beyond foot launch fixed and payout with a winch or truck. That's got everything totally covered...I was appauled at such an operation.
...under everything defined by the Skyting Criteria.Zack C - 2011/03/04 05:29:28 UTC
As for platform launching, I was nervous about it when I started doing it. It looked iffy, like things could get bad fast. I've since logged around 100 platform launches and have seen hundreds more. Never once was there any issue. I now feel platform launching is the safest way to get a hang glider into the air (in the widest range of conditions). You get away from the ground very quickly and don't launch until you have plenty of airspeed and excellent control.
But Skyting Theory tells us...But it was SOP for that group. They had done it many, many times without a mishap.
...that something WILL go wrong so they need to get out there and do more tows until they're able to achieve a malfunction in which an Infallible Weak Link will kick in to allow a safe recovery. Until that point it can't be considered legitimate Skyting Criteria towing.Donnell Hewett - 2008/10/14 00:49:34 UTC
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But I still believe, "Anything that can go wrong will go wrong." It is only a matter of time.
...does the polar opposite of what your theory tells us it will and that you need actual pilots at both ends of the line preflighting equipment, controlling power, pitch, roll optimally at all times, capable of avoiding and/or responding to any of the crap Mother Nature's capable of throwing at us on sane flying days.Donnell Hewett - 1982/09
In addition to the above mentioned roll and yaw tendancies, there is some sideways force on the pilot due to the body line. This is illustrated below:
As can be seen, this sideways force tends to pull the pilot over to the correct side to make the glider turn naturally in the proper direction.
Got that? EVERYTHING you WERE TRYING to achieve, the PRACTICAL implementation of your theory. The implications being that Donnell HADN'T achieved what he'd been "TRYING" to and his implementation WASN'T practical. And it obviously wasn't just HIS theory 'cause these two approaches had been derived totally independently from each other. And by the mainstream at this point it's unknown who started getting their shit together first. And neither of them had actual THEORY down anyway 'cause:March Wings! - Donnell, I believe this is everything you were trying to achieve, the practical implementation of your theory. - Bob Fisher - 5-19-82
Donnell Hewett - 1982/09
In addition to the above mentioned roll and yaw tendancies, there is some sideways force on the pilot due to the body line. This is illustrated below:
As can be seen, this sideways force tends to pull the pilot over to the correct side to make the glider turn naturally in the proper direction.
they both had bogus totally BACKWARDS hypotheses. And that wasn't caught by the mainstream arguably...Bill Brooks - 1982/03/15
HIGH degree of roll control on tow, that INCREASES with line tension. You can go more than 45 degrees off line and get back on again at full tension, and launch safely 30 degrees off wind. In addition, the bridle tends to pull the pilot over to the correcting side of the control frame to give recovery. Control is again very similar to normal flight and feels more positive.
...EVER.Ryan Voight - 2015/02/22
As with all hang gliding, it's important to encourage a light touch.
069-25104
http://c2.staticflickr.com/2/1572/26142964830_289bc3f2cb_o.png
If you teach them how to pull the glider with the harness they'll learn to steer the glider through weight shift simply by running toward their target.
once and in parentheses.Donnell Hewett - 1983/01
You are not the only one who has expressed an interest in air-to-air towing (tuging), but as of this date, no one has reported to me their experiences on this subject. Skyting No. 3 discusses my opinions on this topic, primarily from the theoretical point of view. In essence, I believe that there is no reason that "tuging" cannot be accomplished safely by using a skyting system. In fact, I would never attempt ultralight towing with anything except the skyting bridle. (Or possibly the Brooks Bridle. See Skyting No. 2.)
Yes, now I see the importance of not labeling this as a front view.Hope that helps clear things up.
So we fixed the lockout. Donnell mailed his articles in 1980/12 at which point the autocorrecting Center Of Mass Bridle had rendered the lockout history.Gil Dodgen - 1983/05
Editorial
A NOTE ON TOWING
The early days of hang gliding were marred by numerous towing accidents. During this period this aspect of our sport established a hopelessly bad reputation. And, indeed, last year, as you may have noted in Doug Hildreth's recent accident review, there was a towing fatality by a totally inexperienced Texas pilot.
Some time ago I received a series of four articles on a new towing system from Texas experimenter and inventor Donnell Hewitt. I ran the first in the series of four articles. Editors learn from experience and if I could roll back the calendar I would run all four at once in condensed form. In fact, what happened was that the first article - which made seemingly outrageous claims without outlining the actual technique or hardware - inflamed the then towing establishment. It seems that today's innovators become tomorrow's conservatives so I was bombarded with calls, some from the USHGA Board, telling me that this Mr. Hewitt was totally inexperienced, that he didn't know what he was talking about, and that I was contributing to the possible injury and death of unknown multitudes of innocent hang glider pilots.
I am not a tow pilot, and although Donnell's system made sense to me I was forced to discontinue the series. The essence of his system was a double bridle that connected to the glider and to the pilot. This system would thus pull the pilot back on line in the event that the glider was inadvertently turned off course from behind the vehicle. This would produce a self-correcting system avoiding the infamous "lockout" the factor which seemed to make towing so dangerous.
Well, it appears that Mr. Hewitt's system not only works but, as I've been told by pilots who have made literally thousands of land tows with it, it works beyond all the most optimistic expectations. One pilot told me, "It is virtually impossible to lock out even if one tries."
Gil's comment is three and a half years later and Donnell NEVER...Donnell Hewett - 1982/09
In addition to the above mentioned roll and yaw tendancies, there is some sideways force on the pilot due to the body line. This is illustrated below:
As can be seen, this sideways force tends to pull the pilot over to the correct side to make the glider turn naturally in the proper direction.
...disabuses himself - let alone anyone else - of his roll autocorrecting Skyting Bridle.Donnell Hewett - 1984/01
Hang Gliding Magazine has just completed a series of four articles about "Skyting," a relatively new method of towing hang gliders (April, 1981, August - October, 1983). These were the original articles on skyting and described the theoretical foundation and practical aspects of skyting as it existed back in December 1980. Since the information in these articles is now almost three years out of date, I am sure you are wondering how much of it is still valid today and how much is totally obsolete.
Actually, very little of this material is totally obsolete even though significant advances have been made in skyting since these articles were written. The fundamental principles and theory of skyting are just as valid today as they were then, and most of the equipment and techniques described in these original are also being used today.
Stalls - at any altitude - are virtually ALWAYS consequences of Infallible Weak Links or drivers making good decisions in the interest of your safety. And by the time we had HGMA certified gliders with washout struts and reflex bridles we could handle stalls given enough altitude and if we didn't let things get overly ridiculous. If we say fuck the pro toads - as we should - we're not much worried about straight and level AT stalls after we've cleared the cart. Standard inconvenience crap.Doug Gordon and Donnell Hewett - 1988/03
5) Avoid low altitude stalls.
For towing as well as for free-flight, low altitude stalls are responsible for the vast majority of accidents resulting in serious glider damage, bodily injury, and/or death. Never forget that stalling on takeoff or when landing is statistically the most dangerous maneuver you can perform on a hang glider.
Donnell Hewett - 2005/02/08 23:28:13 UTC
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The sole purpose and function of this weaklink is to limit the towline tension to a manageable level, i.e. a level such that the pilot can still maintain control of the aircraft in the event that the weaklink breaks.
He's not talking about the garden variety LOCKOUT...Donnell Hewett - 2008/10/14 00:49:34 UTC
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In my opinion, the sole purpose of a weak link is "to allow the aircraft to recover safely when the weak link does break".
The one of which we're all scared shitless every time we launch in thermal conditions 'cause we've all heard about them and lots of us have experienced at altitude. He's talking about textbook straight and level but steeply climbing STALLS. And he's gonna use his Infallible Weak Link to address them.Bill Bryden - 2000/02
Dennis Pagen informed me several years ago about an aerotow lockout that he experienced. One moment he was correcting a bit of alignment with the tug and the next moment he was nearly upside down. He was stunned at the rapidity. I have heard similar stories from two other aerotow pilots.
