suspension

[Tad Eareckson]

A continuation of the discussion that was so threatening to HHPA's culture that it found it necessary to silence me on 2010/11/19 by a two to one ratio of the 27 club members who voted to determine who the 140 forum members would be allowed to hear.

Henry Wise supported the ban so it's highly unlikely he'll ever come around here to attempt to bolster his statements.

Charles Schneider understood and supported the principles and value of First Amendment freedoms and will hopefully show up for some more constructive dialogue.

So anyway...

Henry,

http://groups.yahoo.com/group/hhpa/message/11613
Safety - Hook-in Incident

Henry Wise - 2010/11/10 15:13:31

I had a chance to look at Tad's paper on hooking in that he posted last time. While there are many good points, my impression is that he's about 25 years in the past on at least one very important item. He says locking carabiners can't be relied upon to ensure that you're hooked in.

No, what I said was that a locking mechanism on a carabiner does absolutely nothing to enhance the safety of a suspension system and, in fact, actually makes it more dangerous.

I believe his article is written from the point of view that we're still using non-locking carabiners.

I wish. I am quite aware that just about everyone is using absurdly overbuilt locking steel carabiners.

First he talks about taking off when the hang strap is half in and half out of the carabiner (resting on top of the gate). This can only happen if you're not using a locking carabiner.

Oh yeah?

Doug Hildreth - 1991/08

1991/05/17 - Lynn Smith - 37 - Novice - 70 flights, 11 mountain flights - Pacific Windcraft Vision - Lookout Mountain

After two prior flights that day, the pilot returned for his 12th flight at this site. Winds were light. The pilot hooked in and did a hang check. The straps were not straight, so he unhooked, straightened them and rehooked. Reportedly a least three different hang checks were done with at least one unhook. The pilot launched, popped the nose slightly, dove to recover, and about halfway through the pullout, after about ten seconds of flight, the pilot fell from the glider. Fall was over 100 feet. He was killed on impact, with major head, face, and chest injuries. The carabiner was found intact and functional. The gate was not locked. Both hang straps on the glider were normal.

It can only not happen with a locking carabiner if you actually lock the carabiner. It can much more easily not happen on a locking - or nonlocking - carabiner if you listen for the click and/or look at the connection.

A locking carabiner can't lock if something like the hang strap is in the way.

But a nonlocking carabiner can snap shut if something like the hang strap is in the way?

Once the locking carabiner is locked, it's not going to open on it's own.

As opposed to a nonlocking carabiner which will?

That's why everyone went to them in the first place.

Right. 'Cause of the huge problem we were having previously with nonlocking carabiners opening up in flight and allowing the pilot to disconnect.

The only exception to this would be if you're in a situation where you don't lock your carabiner, which should only be over water.

Let's see...

You need to use:
- a locked carabiner over land so you won't fall out of your glider
- an unlocked carabiner over water so you won't drown.

At what altitude does the type of surface you slam into make no difference whatsoever? Wanna call it two hundred feet?

So if you're flying over water with an unlocked carabiner do you hafta stay below a hundred feet to give yourself a better chance of survival WHEN (not if - WHEN) your carabiner opens up and spits you out?

In that case, you should make a precursory check just prior to running.

Whereas if you're using a locking carabiner on a ramp in the desert four hundred feet over the jagged rocks you should assume you're hooked in, skip the precursory check, and start running - just like everyone does at Packsaddle, Hearne, and the Barker Dam?

There have been cases where the carabiner unhooked by itself after a hang check, but those were in the days of the non-locking carabiner use.

Can you either cite an incident or simulate such a failure - without resorting to power tools?

Charles,

Charles Schneider - 2010/11/11 10:39:38

There is one important thing to remember about carabiners. They are strong when pulled from either end length wise. However, if the stress is appied across the width of the biner they are not very strong at all. The only strength left in them at that point is a couple small pins.

I took a look at a Black Diamond nonlocking oval ALUMINUM carabiner. It's rated for eighteen kiloNewtons major axis, seven minor. For a 250 pound hook-in weight that's over six Gs. That's about twice what you need to pull a loop and about the point at which you need to start worrying about your glider breaking up. Is that your definition of "not very strong at all"?

That is why some sort of retention device (a rubber band cut from bicycle tubing) aroung the biner to hold the hang strap of your hang glider securely in the bottom of the biner is a very good idea. This greatly increases the odds that the biner will pull from end to end, not across the gate.

Get a needle and some dental floss and stitch the eye of the harness suspension closed to the point at which installing the carabiner starts becoming a pain in the ass. It'll never accidentally rotate minor axis after that.

Another potentially serious problem is that many setups only use the biner to attach the glider hang loop, the harness hang loop and the parachute hang loop. Therefore, if the biner breaks (which they do) you will not only be detached from your glider, you will also be detached from your parachute.

- When was the last time time you saw an aluminum carabiner connecting anyone to a glider?
- Back it the days when everyone and his dog WERE using aluminum carabiners what was the ratio of carabiner to sidewire failure?
- Steel carabiners DO NOT FAIL in hang gliding operations - major or minor axis - locked or un - open or closed - EVER - PERIOD.

Some folks use two biners or a biner and a metal weak link to separately attach the chute bridal. The problem with this is that you have now given the main biner something hard to bend across and break.

Most folk who fly hang gliders are idiots who have no business modifying critical systems they don't have a snowball's chance in hell of understanding.

One last note, climbers hate to hang from one biner. Only the fact that the biners we now use for HG are Steel makes this palatable at all.

How many keels are we hanging from, what are they made of, and at what percentage of the strength of the carabiner do you think they're gonna fold in half?

Henry,

Henry Wise - 2010/11/11 14:17:38

Tad's article didn't address that and I was comenting on Tad's article. If you use any of the methods to make sure you're hooked in 2 seconds prior to running, you'll never know if your carabiner is sideways or not.

- Tad's article was written for USHGA's useless magazine so Tad tried to keep it relatively short and didn't go into a lot of detail on issues of no practical concern.

- As far as I know there's never been a consequential minor axis issue in the entire history of hang gliding.

- The best way I know to put and keep a carabiner minor axis is to use a locking carabiner and backup suspension.

http://ozreport.com/forum/viewtopic.php?t=17990
parachute bridle attachment

Photos on the third page.

- The next online edition of the article WILL address the minor axis issue.

- A carabiner ain't all that great a piece of hardware for connecting a person to a glider he's staying attached to for a while anyway. If you don't need to be clipping in and out frequently and/or quickly...

one inch speed link

http://www.flickr.com/photos/aerotowrelease/8321197179/


http://www.flickr.com/photos/aerotowrelease/8322255878/

http://www.flickr.com/photos/aerotowrelease/sets/72057594066212198/detail

...near the end of the series.

- Two seconds prior to running you're in launch mode. Ensuring that the carabiner is properly aligned is a relatively insignificant preflight issue. Dicking around with stupid preflight issues in the seconds approaching launch time is a really excellent way to get killed.

http://groups.yahoo.com/group/hhpa/message/8934
Martin Apopot Status

Henry Wise - 2010/01/18 13:24
HHPA Safety Director

Since scooter towing involves a standing start, rather than a prone position as in truck or aero towing, we should be performing a mountain-style hang check. At Pack the standard list is:

* Hooked in
* Biner locked
* Lines straight
* Leg loops
* Chin Strap
* Instruments on

In addition, you should pull the straps tight against the glider, either by pulling up on the glider until you can feel them get tight, or walking forward with the control bar on the ground until they get tight.

- Five steps between hooked in and the launch window, four of which are virtually useless.

- No mention whatsoever of anything along the lines of "just prior to launch" so the five minute delay between the check and John Seward's last (short) flight at Packsaddle on 2010/06/26 was perfectly OK by HHPA "standards".

- A SUGGESTION of a hook-in check whenever anyone feels like it. Last time I looked at the USHGA SOPs a hook-in check "just prior to launch" was MANDATORY for every flight for every rating.

Let's institute this list and hopefully never have this problem again!

Yeah, NEVER AGAIN! Just 293 days from Martin's ambulance ride to HHPA's next wake-up call. That's pretty close to never for a typical hang gliding club. Keep up the good work!

More unfinished business to come when I can get around to it.

[Tad Eareckson]

When we're designing stuff to go on planes we're trying to keep things light and CLEAN - one of the many reasons I despise Wallaby, Quest, and Lookout releases. You're putting a bunch of crap into the airflow which needs to be available for three minutes, fulfills its function in an instant (if you're lucky), and sucks glide point out of your plane for the next three hours.

Zack,

The stuff between your keel and harness is driving me nuts.

- Get some truck tow loops on your harness. Use a needle and dental floss and stitch a couple of light one inch webbing tabs on at your hips. If I'm really anal I can get 40 millimeters worth of stitching to hold 2000 pounds. You don't need all that bridle crap going all the way up to your carabiner.

- I think prior to the 2005 season I was questioning things like the importance of backing up the connection between my parachute bridle and my harness - in case my carabiner failed. Some perlon came off immediately. Then I started thinking about the number of reports I'd heard about people dropping into their backup suspension after the primary failed. Bye-bye backup.

Then towards the end of that season I got this correspondence forwarded to me from some Delaware glider buddies.

Mike Meier - 2005/08/~18

It shouldn't matter whether the backup is in front or behind, because it should be longer than the main such that it is always slack in flight. An argument could be made that IF the main hang loop broke, you'd rather have the backup in front because the most likely scenario in which you'd break the main would be pulling high positive G's, and in that case you'd rather have the pitch trim become more nose down than become more nose up, but on a Falcon 2 that's not really a consideration. As far as where the backup "usually" goes, we usually put it behind the main because that's usually where there's room for it. If the main is properly maintained, and periodically replaced, it is never going to fail anyway, so the backup is sort of pointless. Years ago we didn't even put backup hang loops on our gliders (there's no other component on your glider that is backed up, and there are plenty of other components that are more likely to fail, and where the failure would be just as serious), but for some reason the whole backup hang loop thing is a big psychological need for most pilots.

In other words...

Backup suspension is just a holdover from the days when people were using wraps of cotton clothesline to attach their swing seats to their bamboo keels. And whenever I see someone with a slack backup fluttering in the breeze - or even using something integral and relatively clean - I know I'm looking at someone who really doesn't understand his aircraft.

I had a very different mindset too back then and trusted the people that made my equipment. Since then I've realized (largely due to this discussion) that while I can certainly consider the advice of others, I can't trust anyone in this sport but myself (and maybe the people at Wills Wing).

Lose the backup off your Falcon. It's just complicating your suspension and making it more dangerous. When it's gone people will be totally freaked out and it might get one or two of them thinking.

Looking at your Sport... I'm not seeing separate backup - but you've got a wrap around your carabiner. That's OK if you're borrowing or demoing a glider for a hop or two but it's not a great long term solution. You really oughta get something that fits properly.

And, if you're gonna do that, the webbing really oughta be low stretch - Dacron or Spectra - just like nobody's doing it. All nylon does is eat up some of your climb rate. That's another conversation I need to have with Wills Wing.

[Zack C]

Get some truck tow loops on your harness.

Already got some:

I run the lines from my carabiner through these loops. Why? Gregg suggested I do so to reduce stress on the harness and provide a more comfortable tow by reducing pressure on the hips. He set me up with the release/bridle. I've never tried towing just from the loops so I'm not sure if it would be an issue for the harness. I doubt it, being that that's what the loops are for.

Regarding backup hang loops...

A couple of years ago at a Lookout Wills Wing Demo Days QA session with Steve and Mike, I asked what the benefits of curved wing tips were. Steve's response surprised me: "They look good." He said they didn't provide any aerodynamic benefit and they only put them on their gliders because people want them. Either he or Mike (don't remember) then went on to state that they put backup hang loops on their wings for the same reason. I was impressed by their candor, but disappointed that consumer demand could override sensible engineering even in the realm of aircraft design.

So yeah, at this point I don't really see the need for backup hang loops. But unlike curved tips, I don't see any disadvantage to having them either, and they do provide some small benefit. You say they make the suspension more dangerous...how?

The backup loops on all modern Wills gliders (including my S2) except the Falcon are integrated with the primary. Since both loops are going to be loaded in flight, I've always wondered how much sense that made...it seemed to me like almost an acknowledgement that the backup isn't important.

I have to put wraps in the hang loops on both gliders. My harness lines are (supposedly) DHV length and I requested DHV length loops from Wills in both cases. I agree that I should get appropriately lengthed loops, but the wraps don't really bother me so I never went through the trouble of figuring out exactly how long they need to be.

At any rate, I don't spend enough time at high speeds for minimizing parasitic drag to be a high priority at this point in my flying career. If it was, I'd be using a race harness (among other things).

Zack

[Tad Eareckson]

A picture! Cool. Didn't think we could do that.

Gregg suggested I do so to reduce stress on the harness and provide a more comfortable tow by reducing pressure on the hips.

(Thanks Gregg.)

- Do you want to be flying a harness that you hafta worry about when using a six hundred pound weak link?

- I don't know what harness that is but they're supposed to be designed for towing that way - as well as for fairly brutal parachute opening shocks.

- Do the geometry. The squeeze factor is EXACTLY the same. The only way to reduce it - barring a spreader bar - is to increase the length of the bridle between you and the towline.

- If you still MUST go to the carabiner at least use your line efficiently. You've got those huge loops at the tops of the halves of those yellow bridle lines that are doing nothing for your strength and a lot to you in the way of drag.

I was impressed by their candor, but disappointed that consumer demand could override sensible engineering even in the realm of aircraft design.

BULL'S-EYE. (And all barrel releases must have bent pins (including Rob's).)

Didn't know about the tips. But at least they're not doing any harm and let you put the glider in a shorter bag. Maybe they save a bit of weight too but they don't make setup any easier.

But I've always been greatly disappointed that they catered to the dregs of the sport on the backup issue.

http://www.chgpa.org/forums/viewtopic.php?f=5&t=2809
hook-in failures

Jim Rooney - 2007/10/31 13:31:04 UTC

I've yet to meet the pilot dumb enough or arrogant enough to fly without a backup loop. Perhaps you'll be the first then?

Thanks, I needed a laugh

(And it doesn't even matter that you've shown them the quote from Wills Wing.)

You say they make the suspension more dangerous...how?

At launch - aside from the weather - there's only ONE THING you really need to be worrying about.

Every freakin' prelaunch checklist on the planet includes the item:

Main and backup.

That's one more thing you need to be worrying about that you don't need to be worrying about. It's nothing but a complication, a distraction.

Luen Miller - 1994/11

After a short flight the pilot carried his glider back up a slope to relaunch. The wind was "about ten miles per hour or so, blowing straight in." Just before launch he reached back to make sure his carabiner was locked. A "crosswind" blew through, his right wing lifted, and before he was able to react he was gusted sixty feet to the left side of launch into a pile of "nasty-looking rocks." He suffered a compound fracture (bone sticking out through the skin) of his upper right leg. "Rookie mistake cost me my job and my summer. I have a lot of medical bills and will be on crutches for about five months."

You add totally - make that worse than - useless junk to a critical system and a critical procedure and do enough repetitions you're gonna kill people.

You put an extra strap up there at best you've got something that can put you lower than you wanna be. At worst you've got something else you can partially hook in to.

http://ozreport.com/forum/viewtopic.php?t=17990
parachute bridle attachment

Third page, Steve Rathbun, second photo.

http://ozreport.com/forum/files/binerturn3_197.jpg


And don't forget to check out Steve's first photo to see how much safer locking carabiners make things.

http://ozreport.com/forum/files/binerturn1_154.jpg

Wills Wing Technical Bulletin
TB20061019

On the most recent T2 type hang loop the back up portion is secured around the keel, and over the top of the sweep wire and VG ropes with a quick link. After installation, the quick link should be finger tightened, and then tightened not more than one quarter additional turn with a wrench. (The purpose of routing the backup loop over the top of the sweep wire and VG ropes is that this will provide an additional means of connection between the pilot and glider in the event of a failure in flight of the keel tube.)

Do you REALLY wanna stay connected to what used to be your glider after the keel fails?

Adam Parer - 2009/11/28

Someone of considerable experience commented a few days ago that we should be very concerned that a harness came away from the glider. I can tell you that the loads during the spin were so great I had absolutely no doubt something would have to break eventually. No equipment could have endured much more 'G' before my harness failed. I cannot describe in words how big this 'G' force was. And I am lucky something did fail because i would not have survived much more 'G' force which seemed to be building with every rotation. Besides this I could not move my arms in to get the parachute out and i would not have survived hitting the ground with this sort of spin.

Since both loops are going to be loaded in flight, I've always wondered how much sense that made...

It's so you won't separate from the glider until you hit 120 Gs. Makes perfect sense to me.

I agree that I should get appropriately lengthed loops, but the wraps don't really bother me so I never went through the trouble of figuring out exactly how long they need to be.

Next time you go flying go into hang check mode - with the wrap - and have someone measure from one end of the one inch webbing, through the carabiner, and to the other end. That's the length minus the wrap. That's what you want.

No big deal but you're getting a little more abrasion and having to work a little harder.

If it was, I'd be using a race harness (among other things).

Just clean up what you've got. You've paid good money for the faired stuff making up your control frame and a lot of that's getting neutralized.
---
2012/12/12

Pictures are in now (obviously).

[Zack C]

Do you want to be flying a harness that you hafta worry about when using a six hundred pound weak link?

I'm just worried about the loops failing (after many tows), not the entire harness. It's a Lookout (GT) model. Although the loops are designed for surface towing, they don't do much surface towing over there, so I don't know how much testing the loops have gotten.

Do the geometry. The squeeze factor is EXACTLY the same.

That was what my intuition told me, but multiple pilots experienced with platform launching have said otherwise. Seems possible...with the lines attached to the carabiner, they're just squeezing your hips, but if they're attached to the harness, they're pulling on the harness itself. I don't think I'm going to be convinced either way until I try it both ways.

Didn't know about the tips. But at least they're not doing any harm...

There's been discussion about curved tips leading to tip flutter. Like:
http://www.hanggliding.org/viewtopic.php?t=7674
Of course, Bob Trampenau (as well as Kamron Blevins) would argue the benefits of curved tips. Not sure how much of that is marketing. Aeros's Combat seems to do just fine without them.

That's one more thing you need to be worrying about that you don't need to be worrying about.

If you're going to visually check your main loop, it's not really any more complicated to check the backup as well.

Third page, Steve Rathbun, second photo.

I think my backup loop is too long for that to happen.

Do you REALLY wanna stay connected to what used to be your glider after the keel fails?

Maybe. Less than a week before you posed that question you stated:

There have been a lot of people who've recovered well enough to continue flying careers after being extracted from the wreckage of gliders which broke or disassembled aloft and came down without benefit of silk.

Yes, becoming separated from his wing probably saved Adam's life, but that's just one case.

Anyway, backup loops may not be necessary, but you haven't convinced me that they're a problem.

Zack

[Tad Eareckson]

I'm just worried about the loops failing (after many tows), not the entire harness.

- Those loops are:
-- OBSCENELY overbuilt
-- stitched in to the extent that you'd rip out chunks of your harness before the stitching failed
- Look at your weak link and:
-- look at ONE of those loops. Which one do you think is gonna blow first?
-- think about TWO of those loops.

That was what my intuition told me, but multiple pilots experienced with platform launching have said otherwise.

ALL AT pilots use Bailey releases, four foot long secondary / one point bridles, and 130 pound Greenspot loops. Failing anything better, go with your intuition.

http://groups.yahoo.com/group/hhpa/message/11598
on "Tad"

Zack C - 2010/11/10 01:18:31 UTC

Aviation is pure science. I'm not saying feel and intuition aren't important - in fact I believe they are, but ONLY because they compensate for a lack of understanding of the science.

Kite Strings

A forum devoted to the scientific advancement of hang gliding

Given the mission here, let's go with scientific advancement.

- All pilot weight and tow tension is going to the hang point (through the hang strap).

- That total force/tension is first going to the carabiner through your harness suspension and - as you are presently configured - the halves of your tow bridle.

- The carabiner doesn't know or care whether the tow tension is being transmitted by separate lines or webbing (let's call everything line) going around your harness or if those two lines are tied off at your hips to other lines which continue on up from there to transmit that tension (along now with your weight).

- You're getting squozen EXACTLY THE SAME whether it's a continuous line or a line tied to another line.

- Remember vector diagrams from high school geometry and/or Dennis's books? Do 'em. You can't really understand physics and aviation without them.

Seems possible...with the lines attached to the carabiner, they're just squeezing your hips, but if they're attached to the harness, they're pulling on the harness itself.

That pull can be broken down into two vectors as it's routed to the carabiner - downish and in. The downish vector will add to the load on the harness suspension if the bridle is anchored at the loops - but that has no bearing on the squeeze. It's the in vector that gets you and that's exactly the same whether you're going to or through the loops. The shorter the distance between you and the carabiner and the shorter your bridle the greater that vector is. (Just like the shorter your two point bridle the more you're gonna load the weak link(s) at the end(s)).

I don't think I'm going to be convinced either way until I try it both ways.

Einstein didn't need to hop in a starship to figure out what happens as you approach the speed of light. Some things you just hafta think through.

If you need to put it in the air to understand that you start down the slippery slope that bottoms out here:

http://www.chgpa.org/forums/viewtopic.php?f=2&t=939
Weak link breaks?

Jim Rooney - 2005/08/31 23:46:25 UTC

As with many changes in avaition, change is approached with a bit of skepticism. Rightfully so. There's something to be said for "tried and true" methods... by strapping on somehting new, you become a test pilot. The unknown and unforseen become your greatest risk factors. It's up to each of us to individually asses the risks/rewards for ourselves.

You take control of the sport from the scientists and engineers and give it to a bunch of stupid plane drivers and artists. In REAL aviation those assholes don't get to touch the plane until the until the people with the brains are through with it.

There's been discussion about curved tips leading to tip flutter.

Think I'll stay square and maybe be a little more disappointed in Wills Wing.

If you're going to visually check your main loop, it's not really any more complicated to check the backup as well.

Why bother? If you've checked your main you don't NEED to check - or have - a backup. If you don't have a backup you can spend the three seconds you'd otherwise waste on it checking your main only more thoroughly or doing something else that actually matters.

I think my backup loop is too long for that to happen.

The longer it is the more it flutters in the breeze, turns your faired downtubes into round ones, and reduces your ability to make a safe field. If parasitic drag doesn't bother you that much, at least spend it on something useful like pneumatic wheels.

Less than a week before you posed that question you stated...

That was in the context of what you're better off keeping - wheels or silk - not whether or not it's best to stay with broken, spinning wreckage when you try to deploy the silk.

I imagine there are a few instances in which pilots who died after ejecting would've stayed healthy if they had gone down with the jet fighter but ya gotta play the numbers - and the numbers are probably pretty clear on that issue.

Yes, becoming separated from his wing probably saved Adam's life, but that's just one case.

My default if the keel snaps is that I wanna get the hell away from the glider. That may not always be the best option but, barring a crystal ball...

Anyway, backup loops may not be necessary, but you haven't convinced me that they're a problem.

Years ago we didn't even put backup hang loops on our gliders (there's no other component on your glider that is backed up, and there are plenty of other components that are more likely to fail, and where the failure would be just as serious), but for some reason the whole backup hang loop thing is a big psychological need for most pilots.

A backup loop makes the pilot look stupid. It's a flag that announces, "I don't really understand the physics and engineering of my aircraft." It's like a four foot one point bridle, a Bailey release, a loop of 130 pound Greenspot, or a suspension carabiner turned backwards for anchoring an AT release. Whenever I see that crap I instantly know I'm looking at someone who really doesn't know what the hell he's doing.

Again, if you take yours off you will freak people out and hopefully get some critical thinking going on.

And a guy just got killed a couple of weeks ago a couple of states the other side of you 'cause there was no critical thinking going on at that operation. He HAD a backup loop. He DIDN'T HAVE a tow ring or a secondary release. And he NEVER had the slightest need of the fucking backup loop.

[Zack C]

I agree that the horizontal components of the pull forces are the same regardless of whether the bridle is anchored to the hips or the carabiner. However, are those forces not distributed over a wider area (the pilot's sides) when anchored to the carabiner? At the very least, it seems like this would cause a different sensation to the pilot.

I'm not an Einstein or an aerospace engineer. Yes, some people wouldn't need to experimentally verify this, but I'm not one of them. I'll try it out and see if I notice a difference. There's nothing unscientific about testing a hypothesis...models don't always cover all the variables.

The longer it is the more it flutters in the breeze, turns your faired downtubes into round ones...

I only have a separate backup on my Falcon, which has round downtubes.

A backup loop makes the pilot look stupid.

Have you ever seen another pilot go without one?

If you take yours off you will freak people out and hopefully get some critical thinking going on.

I'm skeptical. If I told them I don't have one so as to reduce drag and the number of things I have to check they'd just think I was a whack job. I'd much rather get them thinking critically about weak links, bridles, and releases.

Zack

[Tad Eareckson]

However, are those forces not distributed over a wider area (the pilot's sides) when anchored to the carabiner?

- If the tow loops are in line with your harness mains - no.
- Otherwise - yes, but the tow tension is gonna try to tilt (pitch) you one way or the other.

There's nothing unscientific about testing a hypothesis...models don't always cover all the variables.

OK, but...

- People have been towing off of platform launch tow loops for decades and you notice you've never heard anything on the issue? Just Gregg making a recommendation 'cause he THINKS that it MIGHT be an issue?

- Let's say there IS a small squeeze discrepancy between the two configurations. How's it gonna compare to THIS:

http://groups.yahoo.com/group/hhpa/message/11170
Question

Zack C - 2010/09/18 21:27:16

The last time I had a weak link break (February) we were towing in strong winds resulting in a great deal of line being paid out. I could feel tension steadily increase throughout the tow until it got the point where I anticipated a weak link break. Was it three times the starting tension? Subjectively, I'd say that was entirely possible. I would certainly hope the weak link would break with the amount of tension I was feeling.

I only have a separate backup on my Falcon, which has round downtubes.

Then you can even less afford to be throwing extra parasitic drag into your airflow. Your move.

A backup loop makes the pilot look stupid.

Have you ever seen another pilot go without one?

Exactly.

I'm skeptical. If I told them I don't have one so as to reduce drag and the number of things I have to check they'd just think I was a whack job.

- Then tell them you don't have one 'cause they're useless, stupid, and dangerous. Print the quote from Mike Meier on a three by five card and keep it in your harness.

- Ask them about the last time they heard about somebody dropping from his failed main into his backup.

- Ask one of them who flies without wheels if he's ever heard of anyone who got creamed 'cause he flew without wheels.

- They're gonna think you're a whack job anyway when you verify your connection status at the front of the ramp when you just did a hang check five minutes ago at the back of the ramp.

- They're gonna think you're a whack job anyway when you start talking about aerotow weak links in terms of Gs and use barrel releases with straight pins.

- Get used to it.

I'd much rather get them thinking critically about weak links, bridles, and releases.

Hit 'em all at once with everything. Keep them off balance. Hell, I kept them off balance for two months and softened up a couple of them for you. You should be able to manage them for a weekend or two.

Ooh! Another cool thing about losing your backup...

When people are checking you onto the tow flight line or ramp - watch how many of them will confirm "Main and backup." without noticing that you don't have a backup.

[Tad Eareckson]

http://www.energykitesystems.net/Lift/2011/2011MAY.html

Joe Faust - 2011/05/02

Hang-line shock-absorption?

The majority of hang gliders in use employ a tether set (set of hang lines or risers) that couples the resistive pilot mass with the system's wing (a kite system).

Respecting that solutions will differ per type of hang gliding activity, how much hang-line shock absorption would be good to meet purposes of

safety?
utilization of lift?
life of the hang glider?

What studies have been made?

This is hang gliding, Joe. People don't study - or think about - anything. They just do it the way they've always done it.

We use nylon webbing (and carabiners) 'cause people originally thought about the suspension in terms of climbing and skydiving in which the goal is to absorb/dissipate energy. We wanna do just the opposite.

We have all the shock absorption we want/need in our airframe tubing. Everything else - sail and wires mostly - is low/zero stretch. There's a reason for that.

When we climb in thermals and accelerate in surges our suspension stretches and contracts an we're converting what would have been climb rate back into heat. There's a reason that the only nylon (elastic) line you find on a sailboat is the stuff they use to tie it to an anchor or dock.

In 2008 I used some webbing from my stash I couldn't identify to replace my harness and glider suspension. I later identified it as Dacron and immediately realized this was what I (and everybody) should be using anyway.

You extend the lives of the pilot and glider by not crashing them and keeping them out of the sun - not by doing something stupid with the suspension.

P.S. I wrote about this issue on the local forum:

http://www.chgpa.org/forums/viewtopic.php?f=2&t=3477

[Tad Eareckson]

http://www.hanggliding.org/viewtopic.php?t=22787
safety

John Stokes - 2011/08/10 13:24:04 UTC

Steel carabiner!!! About fifteen years ago, I was at Wallaby Ranch and saw a fellow who was making some harness adjustments. He had hooked his harness into a hang loop that was connected to a Live Oak limb. As soon as he laid down with all of his weight on the harness, his aluminum carabiner disintegrated!!! Dennis Pagen was there as well and he has mentioned several times in articles about that incident. It was fortunate that the fellow did the hang check at that point in time because he was going to fly later that morning.