Semi-private forum for members contributing to the US Hawks Hang Gliding Training Manual
Forum rules
This forum is for contributing to a US Hawks Hang Gliding Training Manual. Posts in this forum may be moved around as the manual takes shape over time. Please feel free to comment on the organization (or reorganization) of the posts as needed.

Static Towing (ST)

Postby Bill Cummings » Tue Feb 18, 2014 7:49 pm

US Hawks Training Manual Project. (DRAFT)
Static Tow (ST) foot launching.

The first thing to do is to read everything you can get your hands on.
The second thing is to reread everything you can get your hands on.
Third thing is hook up with a USHPA instructor.
http://www.ushpa.aero/

The author started hang gliding towing in January of 1978. This was before the USHGA developed a towing manual. Back in those days of towing a pilot used a stainless steel control frame.
As the towing sport evolved towing went from attaching the tow bridle to the stainless steel control frame (Base tube and down tubes juncture) to using a Center of Mass, Skyting Tow Bridle.
The Skyting Bridle attached about 18” ahead of the heart bolt on the keel tube and the other part of the Skyting Bridle attached to the pilots body near the waist area passing underneath the base tube. The bridle was designed to apply one third of the tow force to the glider at the keel and the remaining two thirds tow force applied to the pilot. This tow force split was also referred to as a 2 to 1 or (2/1) bridle.
Later on pilots tried a 1/1 tow bridle. This will also get you into the air. The tow ratios look different so you can safely assume that the tow up will be different.

Towing from the control frame when compared to towing with the newer Skyting Bridle made controlling the glider comparable to steering a large truck with a blown power steering pump or controlling a car with power steering. The center of mass method made towing about four times easer.

For different reasons (And some not being very good.) pilots decided to alter towing bridles for reasons of parasitic drag, aesthetics, different towing methods like aero towing (AT), platform launching (PL), and static towing (ST).
Scooter tow training, also ST towing, has moved to towing in some areas of the world by attaching the combination tow/release bridle to the pilot over the base tube and in some cases both over and under the base tube.
Some have even hooked to the pilot only and under the base tube. This is not a good idea. (More on this later.)
With each modification of a tow bridle for different methods of towing a new tow pilot must realize that we always have to stay within an operational envelope.
Basically we understand that we should not fly too slow or too fast so that we are able to maintain good control.
How we hook a pilot and glider to a towline can alter which end of the operational envelope we will find ourselves.

For example, hooking directly to a single point release on the harness of the pilot after having passed the towline underneath the base tube of the control frame is the best method for platform launching. However if a pilot chose to run off the launch from the ground and not use the platform launch that would be choosing the worst attachment method for static towing alone or also incorporating a pay out winch/reel.
I will attempt to explain why but if it isn’t self evident to a beginning pilot at this point this will be one of many examples why you shouldn’t attempt to teach yourself how to tow launch. Having a knowledgeable instructor is of the utmost importance.

Most of us were taught that running across the street without looking both ways could really mess up our day. Having been taught that lesson and the ramifications of disregarding it we were more readily convinced that running with scissors or while looking through a hand held telescope was something also to avoid.

Not having a climb restricting “V” bridle, 2/1 Skyting bridle, or 1/1 bridle while Static Towing (ST) puts the pilot at the mercy of the tow operator and the wind.

Tow pilots refer to a term, “Being locked out over the top.” as a situation where the pilot can not shift their weight far enough forward to stop a climb while under tow. This can happen very easily if there is too much tow line tension or there is a steep wind gradient near the ground. Towing into a thermal can add to this lock out over the top.

Being locked out over the top also increases your odds of progressing into a lock out to the left or right. With a slow climb rate the “sweet spot,” down wind of the tow vehicle, is quite wide. The glider is able to move to the left or right of the tow vehicle much farther without getting locked out left or right. The more tension or the faster the climb the narrower the “sweet spot,” becomes.
I’ll add this left and right lock out example here then get back to the over the top lock out information.

For example if you have a slight cross wind from the left on your tow road and you hold your flight directly over the road this will be holding a position that has you closer to a lock out to the left. You may be doing just fine but if the wind is greater as you get higher and your tow vehicle (static) doesn’t slow down to maintain the same line tension the sweet spot will narrow. You will also be climbing faster due to having more line tension. The tow vehicle not slowing down to compensate for the greater wind speed at altitude can be the cause or your lock out to the left even though you are still holding position directly over the tow road.

In this situation a beginning tow pilot might think to themselves that they are locking out to the left now but I was still over the tow road and I didn’t do anything to cause this!
You didn’t do anything is correct. But -- when the headwind increased as you gained altitude that increased the line tension. You didn’t get the nose down to reduce the line tension. Your sweet spot narrowed. Even worse than that would have you using a tow bridle that would impede your effort to get the nose down.

Choosing from different bridles or attachment points can determine whether your pitch control is good, bad, or inadequate.

Going back to the over the top lock out now if you have a bridle that allows you to lower the nose to slow the climb rate you will have just widened your sweet spot. The sweet spot is the area left and right and downwind of your tow vehicle that you can safely operate in.

If however you are low to the ground and have too much line tension and are being towed under the control bar and the tow line is attached to the pilot only --
Well now, just the thought of this will send shivers up and down the spine of any instructor that knows what he is doing.

If this primer was news to anyone then take my word for it -- hook up with a tow instructor and don’t try towing a hang glider on your own. Oh, and don’t forget to look both ways!
Bill Cummings
User avatar
Contributor
Contributor
 
Posts: 2574
Joined: Wed Jul 13, 2011 6:20 pm
Location: Las Cruces NM 88005 (Region 4)

Re: Static Towing (ST)

Postby Bob Kuczewski » Fri Feb 21, 2014 12:43 pm

billcummings wrote:The first thing to do is to read everything you can get your hands on.
The second thing is to reread everything you can get your hands on.
Third thing is hook up with a USHPA instructor.
http://www.ushpa.aero/


Good advice Bill!!

I hope to someday have US Hawks instructors, but right now, your comment about getting with a USHPA instructor is still one of the best things a new pilot can do.

:clap: :clap: :clap: :clap: :clap:
Join a National Hang Gliding Organization: US Hawks at ushawks.org
Bob Kuczewski
User avatar
Contributor
Contributor
 
Posts: 4879
Joined: Fri Aug 13, 2010 2:40 pm
Location: San Diego, CA

Re: Static Towing & tow line recovery chutes.

Postby Bill Cummings » Wed Jun 22, 2016 6:56 pm

The fix for a tow line recovery chute causing a hang glider pilot to crash is becoming a lost art.
With the advent of YouTube one would think visuals would be getting the word out how to avoid problems but that doesn't look to be the case.
While towing, pilots have had towline recovery chutes blossom open and then the pilot overtook the chute and it became tangled either with the pilot or the glider and sometimes both.

Pilots overtaking their blossomed towline recovery chutes have ended up being towed by their helmets, lip boom microphone, vario, training wheel, reserve parachute safety pin, harness mounted radio, hall wind speed meter, GPS, downtube/basetube junction wing nut, the hook knife handle, the ballistic recovery chute handle and less often, several of these during one event.

The spectrum usually runs somewhere between, extremely unfortunate and dangerous to deadly.
On the low end would be tangling with your helmet. You could still basically be close to center of mass towing in this situation. However towing by the handle of your ballistic recovery parachute may be less desirable center of mass towing. It's a tough call. Which would you prefer?

On the other end of the spectrum towing from an instrument located at the corner of your control frame is way worse than a center of mass snag when tension is restored. (For sure it will progress into a lockout.)
The multiplying factor for this emergency depends on where your release and/or weak link is located.

There are ways to eliminate a blossoming line recovery chute and most readers have already thought of the 100% fix.
I prefer not to use one.
There are far better ideas being used than a towline recovery chute that stays collapsed because you are towing through it.
Just pause and think. What are all the possibilities that you can think of that could cause tension to come off of the towline while under tow? -------------
If you find yourself about to tow on a tow rig belonging to someone else that uses a towline recovery chute; has that owner done anything to mitigate the blossoming of the chute when tension comes off of the tow line before you release?
There are several different methods that are being used or have been used to fix this problem. At this time I want to pause and brainstorm on the Hang Gliding General thread for any new better ideas or revive some of the old ones then come back to this training thread with a list of the best ideas. There is no need at this time to be towing with ideas that have been tossed out, with cause, years ago.
Bill Cummings
User avatar
Contributor
Contributor
 
Posts: 2574
Joined: Wed Jul 13, 2011 6:20 pm
Location: Las Cruces NM 88005 (Region 4)

Re: Static Towing (ST)

Postby Bill Cummings » Thu Jul 20, 2017 9:09 pm

A lonely country road for static towing is nice to have close to home.
One vehicle passing by per hour can be annoying if you're broke down and need help
but if you're towing that same volume of traffic can be annoying on the other end of the scale.
The trick is to try and reduce as many obstructions as possible and get some airtime.
It doesn't seem to be that a perfect flying site exists anywhere. There is always room for improvement.
This post is about impediment mitigation as it relates to static towing (ST).
Many issues back the USHGA or was it in the USHPA magazine there was an article about
mitigating towline obstructions along a road in the form of state, county, or township road signs.
The concern was that the towline as a result of a crosswind to the road could cause the towline to come in
contact with a sign on the shoulder of the road. Some shapes like a warning sign would not create
as big of a problem with a towline as a rectangular speed limit sign; or stop sign.
sign #2.JPG
sign #2.JPG (31.17 KiB) Viewed 974 times

sign #3.JPG
sign #3.JPG (23.95 KiB) Viewed 974 times

Some shapes allow the towline to slide up and clear the sign while others would
catch the towline under it.
The article had the tow crew standing a piece of PVC up along side the sign to allow the towline to slide up the PVC and not catch under the sign. They cut a slot length wise in the PVC to allow the edge of the sign to slip into the slot. They taped the PVC to the sign. (I would use clear packaging tape.)
For the base of the PVC pipe they would pound a larger diameter steel pipe into the ground to leave there and be a socket for the PVC to be inserted down into the steel pipe. The socket pipe was pounded completely down so that its top was flush with the ground.
This could still end up with you getting a ticket by taping to a road sign but if you take the PVC and tape home with you at the end of each towing day you will probably get by.
Bill Cummings
User avatar
Contributor
Contributor
 
Posts: 2574
Joined: Wed Jul 13, 2011 6:20 pm
Location: Las Cruces NM 88005 (Region 4)

Re: Static Towing (ST) Draft

Postby Bill Cummings » Tue Nov 28, 2017 4:53 pm

Static Towing: by Bill Cummings
As of this date, November 28, 2017, The US Hawks Hang Gliding Association has not endorsed Static Towing (ST).
It has been suggested within the membership that towing be handled at the local club level when it comes to training, tow ratings, and possible insurance issues. The USHPA included towing as part of its training, rating, and safety endeavors so the US Hawks may choose not to reinvent this wheel.

Some of the senior pilots that have collected here at the US Hawks Hang Gliding Association were towing hang gliders before the USHGA/USHPA even thought about how much profit they could bring into their non-profit corporation by embracing towing.
The US Hawks Hang Gliding Association has this mission statement:
To Promote, Protect,and Serve Recreational Hang Gliding
It was due to spacing constraints that there is no period (.) at the end of the word, “Gliding” in our banner but I make believe that the sentence would go on to say, “...While Leaving Your Money In YOUR Pocket.”

The first time I allowed my USHGA membership to laps was when the organization delayed publishing of the second edition of the Skyting article by Donnell Hewett. For that reason I wouldn’t want the US Hawks to lose pilots that have decided that they want the information and don’t care if others feel that it would be bad for them.

Knowledge is knowledge whether you’ve paid too much for it at Yale, a suffer-able amount at the community collage or even paid less or next to nothing to get it off of the internet.

In your search for knowledge – if you’ve gotten this far – you now realize how cheap you really are.
But wait! You’re in good company. The US Hawks are all about having fun while hang gliding and at the same time teaching you that landing on a fat wallet may even prevent a puncture wound near a critical area.

The purist form of hang gliding is said, by some, to be foot launching off of a hill or better yet a mountain.

For those simply too far away from hills or mountains towing above the flat lands is an alternative to other exciting things like waxing the car, walking the dog, bible study, or cutting the grass. Life is full of difficult choices.

Years ago the biggest leap in towing ease and safety was given to the hang gliding sport by Dr. Donnell Hewett.
Reference: Donnell Hewett's original 12 criteria for a good tow system
at: http://nhgc.wikidot.com/donnell-hewett

The R&D progressed from his original criteria through the 1980’s. Several modifications were made in different places throughout the hang gliding towing world but with each change for the most part gave results like changing the salt measurement in the soup recipe. Where some pilots liked the changes others simply couldn’t tolerate them.

One personal change that I made for my towing operation was criteria #2 The tension in the tow line must remain essentially constant throughout every phase of the towed flight.

I prefer to not have a pressure/tension gauge or automatic regulating device at the tow vehicle. If I want to pull in on the control bar to reduce line tension to correct for a thermal induced wing over I don’t want the driver over ruling me simply because the driver is following a constant pressure/tension gauge criteria. I prefer pilot in command, constant radio transmission, during tow. (This of course is not done with students but only experienced tow pilots.)
Not always does one solution answer all variables.
No one should be able to call you fussy if you don’t want to have an auto pilot feature that doesn’t come with an off switch.
The big disappointment with an automatic pressure/tension limiting device is having the, “OFF Switch,” (If any,) hundreds to thousands of feet away in the tow vehicle. There probably are tow pilots that would still prefer constant towline tension through all phases of the towed flight. On the plus side knowing that the tension will remained constant during a flight path deviation would make things easier for the person filling out the accident report. (Less variables with all the built in consistency.)
Knowing that you will have a Controlled Flight Into Ground makes it easier to estimate how many minutes you will arrive at the impact zone ahead of the ambulance.
The author is doing his best not to impart any bias on the constant tension issue.
Bill Cummings
User avatar
Contributor
Contributor
 
Posts: 2574
Joined: Wed Jul 13, 2011 6:20 pm
Location: Las Cruces NM 88005 (Region 4)

Re: Static Towing (ST) Draft

Postby Bob Kuczewski » Sat Dec 02, 2017 5:34 pm

Bill Cummings wrote:On the plus side knowing that the tension will remained constant during a flight path deviation would make things easier for the person filling out the accident report. (Less variables with all the built in consistency.)
Knowing that you will have a Controlled Flight Into Ground makes it easier to estimate how many minutes you will arrive at the impact zone ahead of the ambulance.
The author is doing his best not to impart any bias on the constant tension issue.


The author might need to try a little harder not to impart any bias on the constant tension issue.    ;)

:srofl: :srofl: :srofl: :srofl: :srofl: :srofl: :srofl: :srofl:

Bill, your experience is well appreciated here. Thanks very much.

         :salute: :salute: :salute: :salute: :salute:
Join a National Hang Gliding Organization: US Hawks at ushawks.org
Bob Kuczewski
User avatar
Contributor
Contributor
 
Posts: 4879
Joined: Fri Aug 13, 2010 2:40 pm
Location: San Diego, CA

Re: Static Towing (ST)

Postby Bill Cummings » Sun Dec 03, 2017 6:26 pm

US Hawks Hang Gliding Association Training Manual (Draft)
Static Towing.
The Leader Line:

If you are already doing Static Towing (ST) or plan on starting to do it you may be interested to know that Static Towing of hang gliders as been around longer than some pilots have.
Older tow pilots found out that some fresh ideas to improve on equipment or methods had latent insidious, tightly wound misfortune, crouching and ready to spring forth and scream, SURPRISE!
There were so many new ideas tried and discarded that remembering and passing all the discarded information along to newer pilots was lost in the fog of memory. New pilots were doomed to repeat poorly thought out improvements. YouTube is proving it.

Before I forget, there was a problem when the weaklink broke while towing and the release hardware would snap back and injure the pilot. One idea was to put on a thicker, Leader Line, of about 50 to 75 feet ahead of the 2/1 Skyting Bridle and release. On the far end of the, Leader Line would be the weaklink. This would keep the release hardware from snapping back at the pilot when the weaklink broke.

It worked! The release hardware would not snap back at the pilot when the weaklink broke.
SURPRISE! The Leader Line was now dragging through the lurking, well rooted, corn stubble in the cornfield next to the road after the weaklink broke. This was a highly reliable way to stop the glider by slam dunking the nose plate of the glider into the corn field. It was like landing on an aircraft carrier with an arresting nose hook instead of a tail hook.

The Leader Line idea had a short life span. Although it put an end to the release hardware snapping back and hitting the pilot when a weaklink broke it created a bigger snagging hazard as it was drug on the ground.

What did work was making a tow bridle so robust that it would not snap back from any tension employed and removing the Leader Line forever.

A two to one (2/1) bridle with any elasticity is the same thing as putting your head in front and in line with a giant sling shot with enough tension to hurt you. With the elasticity problem solved the next concern is to shorten up the length of the tow bridle to as short as possible. We don’t want to be dragging a long tow bridle on the ground either.

When other things changed with the hardware used for static towing we were forced to revisit the 2/1 tow bridle even after we thought we were finished with its R&D. More on that on the next post.
Bill Cummings
User avatar
Contributor
Contributor
 
Posts: 2574
Joined: Wed Jul 13, 2011 6:20 pm
Location: Las Cruces NM 88005 (Region 4)

Re: Static Towing (ST)

Postby Bill Cummings » Tue Dec 05, 2017 6:48 pm

US Hawks Hang Gliding Association Training Manual (Draft)
Static Towing.
The insidious chain of events when changing each link.
By Bill Cummings

Some well known and respected Tow Tech’s have made blanket statements about towing, in general, which have mis-stated reality. One statement led pilots to believe that weak-links have the sole purpose of preventing the over-stressing of the hang glider while towing. It can also prevent damage to the pilot.

Example: If you are towing with a cheap length of 3/16” Polypropylene towline, you wouldn’t be able to damage a glider in tow flight. That is, not a hang glider that had been certified by the Hang Glider Manufactures Association (HGMA). The 3/16” towline would break before the hang glider did.
It would not be an informed assumption that the towline is two things in one. That we didn’t need to worry about installing a weak-link since the towline is also the weak-link. IT IS NOT!.
Just for practical, logistical sense alone, it would be desirable to have the line brake near the pilot and not someplace mid-point on the towline. It’s REALLY handy to have the weak-link break near the pilot before the towline breaks. The towline needs to be stronger than the weak-link and the weak-link needs to be near the pilot’s end of the towline.

Making a weak-link stronger leaves you with a strong, weak-link. This conjures up George Carlin’s comedy routine containing, “Jumbo Shrimp,” and “Military Intelligence.” (oxymoron’s.)
The weak-link has to be strong enough to do the job, but most other reasons to make the weak-link stronger will start a pilot down the chain of events that leads to misfortune.

Example: Your tow system is well engineered and working fine, but ‘Hey! Hey! Hey! Fat Albert shows up with his 195 sq’ Falcon and wants you to tow him. For sure he will need (I hate to say it!) a stronger weak-link to do the job. The towline is still stronger than the (oh this hurts.) stronger weak-link that Fat Albert is trying out. The first tow attempt with the stronger weak-link shows us that Fat Albert’s weak-link is still insufficient. Not only that, but the tow bridle, now stretched due to the extra tension, snapped back and also broke something on poor Albert’s face when the weak-link broke.

All tow bridles should be tested with the strongest weak-link that will ever be used with it. Hook the bridle and the release to the weak-link between two vehicles and slowly pull until the weak-link breaks.
If the release hardware snaps back and puts a hole in the oil pan use a heaver bridle that will not stretch.
Some pilots, after increasing the strength of their weak-link, have discovered that they could no longer activate their release.
The strength of a weak-link has far more importance than solely protecting the glider from being over- stressed. As described above, you can see that changing one link can affect more than just one thing.
Bill Cummings
User avatar
Contributor
Contributor
 
Posts: 2574
Joined: Wed Jul 13, 2011 6:20 pm
Location: Las Cruces NM 88005 (Region 4)

Re: Static Towing (ST)

Postby Bill Cummings » Mon Dec 11, 2017 9:41 pm

US Hawks Hang Gliding Association Training Manual (Draft)
Static Towing. Weak-links.
By Bill Cummings

On previous posts, attention was focused on the fact that changing the strength of a weak-link can make your tow bridle work differently. It could also cause your release to work differently, or not at all.
The best idea is to test your equipment at home and not above the airfield. If you are a recreational tow pilot, you should be breaking a weak-link regularly, since your main concern should be your safety.

If you are flying in competition, paying for flights at a business-minded flight park or airport, more than likely, you will not be breaking as many weak-links. The paid tow operator’s main concern is usually money ahead of safety. You see, every weak-link that breaks slows down the number of tow fees that change hands…….a decrease in “cha-ching, cha-ching”! To justify the business’s resulting push for your use of a stronger-than-necessary weak-link, you will be told scary stories about pilots crashing, just after lift off, due to their weight-appropriate weak-link breaking, thus causing a low altitude stall and nose-in. Such is bad advice, inspiring fear, and it is advise that is not in your best interest. Most air parks will insist that you use their “one-size-fits-all” weak-link, not necessarily safe for you, your glider or your launch. Such faulty advise regarding use of their “stronger” weak links, has probably been influenced by what works well for the business, so that all of the “SAFETY FIRST” signs, planted by the business are misleading propaganda.

Rather, if you mindfully conduct each flight of your tow operation as though you will lose tow rope tension at any second, then breaking a weak-link poses no additional hazard to you. It may result in an annoying sinking feeling since the hope was to tow as high as possible.

First, consider this:
Question: Besides breaking a weak link while you are under tow, what other causes are lurking that will reduce or stop tow tension?
Answer: Any number of things: 1) A towline break; 2) A premature or accidental release at either end of the towline; 3) Any unanticipated obstruction (ie: a dog, kid, deer, police, or skunk) appearing in front of the tow vehicle; 4) An unexpected oncoming vehicle, running out of gas, a fuel filter plugged, a motor seizure, a cell phone or wallet on the hood, a flat tire, a bad ignition switch, a bee-stung driver, something dropped on the driver’s lap; 5) Many other causes.

So putting on a strong weak-link for safety’s sake is poor logic.

A beefed-up weak-link will still not prevent all of the other innumerable towline tension-termination surprises. While you’re under an inappropriately strong weak link tow, blissfully rocketing away from the planet, smugly relying on your beefed-up weak-link to protect you from a hammer head stall near the ground….. SURPRISE!…….you’re suddenly pitched up and stalled…….tow tension lost due to reason #38, or maybe reason #166! If you’re not ready and able to handle loss of line tension during every second of the tow, you were doing something wrong before you lost towline tension.

As you do your beginning, under-tow running take off (launch), the best course of action is to keep your body upright until more than enough airspeed is attained, before you allow the glider to briskly lift you off. When your feet are lifted from the ground, you want to hold the glider low over the ground until your airspeed increases and the glider wants to climb, in spite of you holding the bar in. If you do this you will always allow yourself and your glider to gain enough energy (airspeed) to land safely, if tow tension is lost near the ground.

If you don’t hold in, and you allow the glider to wallow into the air, just a little above stall speed, your reaction time has to be exceedingly good to affect a satisfying landing when tension is lost or reduced.

Single surface training gliders have less energy retention than double surface gliders. They also have a stronger pitch positive design, due to reflex battens and luff line settings. When you use a stronger weak-link with a single surface glider, and while flying at a high airspeed, it’s easier to nose-up into a stall when excessive tension is lost.

When flying fast, parasitic drag increases. If a pilot selects a weak-link that will not stand up under those extreme conditions it will break before you can attain more airspeed beyond that of your weight shift range to prevent a nose high stall. Said differently, when the weak-link breaks you will be able to pull in, round off the climb, prevent the stall, and fly normally. More can be said about weak-links and will be in later posts.

The pilot who has been schooled into believing that a weak-link is for one purpose only, that is to keep from over stressing the glider in flight, will not be employing other available safety advantages that a weak-link can offer.
Bill Cummings
User avatar
Contributor
Contributor
 
Posts: 2574
Joined: Wed Jul 13, 2011 6:20 pm
Location: Las Cruces NM 88005 (Region 4)

Re: Static Towing (ST)

Postby Bill Cummings » Tue Jan 16, 2018 5:08 pm

US Hawks Hang Gliding Association Training Manual (Draft)
Static Towing: Weak-links breaking when you want them to or sooner.
By Bill Cummings

When a weak-link breaks, it releases you from the towline.

This may have inspired the invention of the Link-knife release, which ranks near the top of releases.

Pilots that think they’re in the know say, “You have to be using an infallible release.” But, SURPRISE!, no one is using one of those. This became evident through personal “infallible-release”-testing experience, towing with my buddy Don, on the frozen lakes of northern Minnesota. This testing can be likened to the way many car manufactures, still, today, test the efficiency of their vehicle products by using the punishing frozen conditions of Minnesota winters.

Our innumerable tests of various infallible-releases proved to us that NONE of the releases PASSED THE INFALLIBLE TEST! Various conditions existed to cause us to realize that anything could interfere with a safe release. For example, slushy snow would turn into ice at altitude, thus causing any and all releases to fail! While, obviously, most tow pilots weren’t given to testing their new release mechanisms fresh out of their freezers, the Minnesota tow pilots, more so out of happenstance than foresight, reached a conclusion: “Infallible,” releases didn’t exist - - - and more than likely they never would!

And, surprisingly, some of, what we thought, were our more reliable “infallible” releases even failed when tested during the subsequent summers.

You might be wondering about all these failed release situations and how it is that your author is still here to write this. Patience! Allow me to enjoy my captive audience. > This > way > captives. >>>>>

During summer towing, the infallible releases would, of course, no longer freeze up, but on more than one occasion with regards to the Link-Knife a small twig or piece of straw would somehow crawl into the Link-knife slot and position itself between the weak-link string and the two razor blades. The debris then served as a shield, protecting the weak-link string from the razor blades, resulting in a failure to release.

Other release failures occurred after pilots bought twisted 1/4” or 3/16” Polypropylene towline instead of the more desirable diamond braid. We found that, under tension, the twisted-braided rope became untwisted and, in doing so, twisted-up the 2/1 Skyting Tow Bridle, thereby capturing the release cord. Such action, in turn, created so much friction that release, as designed, was impossible.

Whether through such conditions of freezing, clutter, or capture, the “infallible” releases were deemed fallible.

Where release failures, in freezing conditions, may have a short list of causes, the list could get longer, depending on what type of infallible release was about to fail.

In addition to what we learned during our various release-test conditions, described above, we also learned that freezing or cold temperatures did not noticeably affect our weak-links.

While sitting in your living room holding your “infallible” release in both hands, consider where you might put a drop of Super Glue to make your release fail and mess up the success of your next in-flight release activation. The drop of Super Glue would take the place of that random icing problem described, previously.

This is not to say that the three categories listed have covered all the categories for “infallible” release failures. I know the term “infallible” release failures sounds foolish, but, so too, does towing with a strong weak-link.

I am personally aware of four different towing occasions in which various assistants to the pilot, or the pilots, themselves, hooked up a release incorrectly, so that it either didn’t release in flight, or it wouldn’t have if it hadn’t been noticed in time. Other failure events (sleeper cells) are patiently waiting. I guarantee there will be more surprises to be discovered.

Since there are no “infallible” releases, what is your next best course of action? One popular idea, in order to remedy the release failure, would be to pull out the hook knife and start cutting the tow bridle.
Actually, that isn’t the next-best course of action, even though that method is still being taught when using the Skyting Bridle, or even when using some of the newer supposedly improved tow bridles.

When one hand is busy with the hook-knife steering ability reduces by about 95%.

Others put aside the Skyting Bridle and “made improvements” that seemed to work okay with some of the faster gliders, but not so with the newer and slower single surface wings.

So, back into the time machine these re-designers went and, once again, found that they were repeating the same mistakes of the “olden days”. The results? Increasing incidents of lock-outs over-the-top! Until it underwent improvements, the Skyting Bridle, when used with the proper weak-link, actually had that pesky lock-out over-the-top problem sufficiently and effectively answered.

Those same back-in-time “bridle improvement” efforts proved just as ineffective and unsafe when
the towline was released, the weak-link broke, or was cut under pressure. Again we started seeing the wrap and capture, due to shorter tow bridles, resulting in the towline tangling with the nose wires, as experienced and remedied in the 1980s.

In a later post, the safest way of cutting away a Skyting Bridle will be explained.

The problem of little changes, made along the way to bridle “improvements”, simply allowed many of the other eliminated problems to resurface.

Let’s get back to the next-best course of action for when the “infallible” release fails.

Forget about grabbing the hook knife. There is a better course of action. When using the correct strength weak-link, a certain procedure, that of purposely breaking the weak-link, has been used by tow pilots since the early 1980’s. Of course, there are several things that play into this better course of action and they include:

1) The weak-link used with a Skyting Bridle should not stand up to the increased parasitic drag of a fully stuffed base-tube. Before you are forced to climb higher, you want the weak-link to break. You want it to break before you are pitched up into an unpreventable stall. Not so with the strong weak-link.

2) There is less energy retention with single surface gliders than double surface gliders.
A single surface glider will stall sooner than a double surface glider, reducing your time and ability to round off before a nose-high stall occurs when tow tension is lost for any reason.

3) A 2/1 Skyting Bridle gives better pitch authority than a 1/1 bridle. The 1/1 tow force bridle tends to have the pilot pushing out, under tow, which is less desirable when tension is lost abruptly.

4) A 1/1 bridle gives more pitch authority than a Pro-Tow bridle.

Also during a lateral (left or right) lock out, a push out of the base-tube will break the correct weak-link but wouldn’t if a strong weak-link was used.

Again the next-best idea to get rid of the towline, for occasions when the infallible release failed, was to break the weak-link on purpose, while keeping both hands on the control bar. Allowing for this additional application of a weak-link necessitated procedural mandates while static towing.

Never tow to the end of the runway, road, lake, or to any dead end. Always leave some runway ahead of the tow vehicle when you want to get off the towline. If the “infallible” release fails, tell the tow driver to “Break the weak-link.” To do that, the operation will need room ahead of the tow vehicle and a constant-transmit radio on the pilot for the entire tow.

If you are also using a pay-out reel, it must be able to be locked up immediately to allow the driver to break the weak-link. This would be another time where constant tension during all stages of the tow operation would be undesirable.

We know that some pilots endorse a one-size-fits-all weak-link, a strong weak-link, used, only, to protect the glider from being over-stressed. Tow techs, who say that a weak-link won’t save you from a lock-out, are 100% correct, if you’re using a strong weak-link. Sure, that type of weak-link will allow for a faster climb with increased tension, but when it breaks, if near the ground, you and your
glider may not recover from the stall before coming in contact with the ground.
Understanding these variables a weak-link CAN SAVE YOU from a lock-out over the top and allow a purposeful weak-link break.
If constant radio contact from the pilot is lost for any longer than three seconds, the driver must stop.
If the pilot doesn’t release at the prearranged place, where the vehicle is supposed to stop, short of the end of the runway, the driver is to break the weak-link.
Your static tow procedure and equipment has to be such that losing tension at any second of the tow operation for any reason will not pitch you into an unpreventable stall, but allow you to either fly or land safely.

More than likely the closest thing we will ever get to an infallible back-up release is the correct strength weak-link. They don’t freeze up, although they do break, sometimes before you want them to break.
But since we conduct our towing so that we are ready for loss of tension at any second, for any reason, what do we care?
If the exasperated pilot waiting in the queue for his tow complains about your, dialed in, weak-links popping tell the pilot where to go. When it comes to your personal safety usually it is you and not the pilot behind you that is the most concerned.
Bill Cummings
User avatar
Contributor
Contributor
 
Posts: 2574
Joined: Wed Jul 13, 2011 6:20 pm
Location: Las Cruces NM 88005 (Region 4)

Next
Forum Statistics

Who is online

Users browsing this forum: No registered users and 1 guest

Options

Return to US Hawks Training Manual Project