Al Hernandez - 2010/09/11
[HHPA] Question
1. When doing a platform tow as soon as the vehicle reaches speed, and the wind indecator reads 25, or 30 mph, the pilot pulls the release, the glider starts to go up shouldn't the pilot be pulled in just incase the weak link breakes??????
2. Or should the pilot just let the glider pop off and fly off the platform all the way up???? I myself think that as soon as the pilot pulls the release the pilot should be pulled in already, and have control of the glider in stead of just letting the glider pop off off the platform. I also think that the pilot should be pulled in till he or she get to a good altitued then the pilot should let the glider fly at trim and just correct all the way up.
Gregg Ludwig
I can provide a short answer now ..but the full answers are provided during hands on flight training. The forum is a great source of info but must be accompanied with flight training. Yes, pulled in slightly during initial climbout and be ready to compensate if the towline becomes disconnected. With my rack, like many, the glider will not lift off the rack without a slight pushout.
Bob Fisher - 2010/09/12
Al,
in a truck tow launch, you very definitely need to be pulled (a lot) in as you release. Not pulling in considerably increases your chance of a weak link break as the glider "pops up" since it significantly increases the speed of the "pop up" and subsequently the acceleration of the drum and this increases the load on the link as you pop up.
There is no equivalent loading on an aerotow launch - the weak link loads are steady.
Bobb Loper
Al, there are 3 things that determine the "pop up" during the launch of a platform tow:
a) The relative air speed. (Wind and truck speed)
b) Position of bar at release.
c) Attitude of nose. This attitude can be increased or decreased by length of the nose release line (angle of wing to horizontal)
In an open space like a runway, a gentle release with gentle climb at origin may be desirable, but there are other conditions where a rapid climb out of trouble may be best. At the Brookshire location, the narrow road was bordered on each side by a bar ditch with a barbed wire fence and in some cases, mesquite trees next to the fence. A gentle launch in a cross wind meant a longer time in the danger zone. If a glider is launched at a higher speed a broken safety link would still allow the glider to pop up high enough to clear the obstructions and land in the open field behind the trees.
Tad Eareckson - 2010/09/16
I got a question too.
1. You're flying an aircraft over which - even in free flight - you have mediocre control authority.
2. You're tying it to a rope - which makes it dangerously roll unstable.
3. You're ELECTING to use a release system which - in an emergency - requires you to always compromise, often fully surrender any of what may remain of your already pathetic level of control.
4. You're occasionally taking off in thermally crosswinds from a pencil thin runway bordered by ditches, barbed wire, and mesquite trees.
Why the hell are you throwing into that can of worms a weak link which blows a hair's breadth over your dialed in winch tension?
Does the adrenalin rush you get from quadrupling the ambient danger level work that much better to cure erectile dysfunction than all those spam remedies upon which I've been wasting my money?
If someone can give me a halfway intelligent rationale (i.e., something MUCH better than the above) for this insane tradition I'll immediately PayPal him a hundred bucks.
Dave Susko
Sooooo, your point is: Sport flying is dangerous????? Anyone who's been a free flight pilot for any length of time has probably figured out a way to rationalize away any of the danger. I don't even bring up hang gliding in casual conversation anymore. I'm tired of all the silly questions. "What happens if you launch and there's no air?" A wuffo in a bar once asked me. It's about managing risk. If you lose control and crash, there's quite likely something that you could have done as the pilot to prevent it, including simply deciding not to fly in the challenging conditions. Besides what else am I going to do? Lay in my bed in a bomb shelter with a lifetime supply of disinfectant and suck my thumb? I think this was quoted in the magazine recently, "Add years to your life by adding life to your years."
Henry Wise
If you launch and there's no air - you've got more problems than just flying! How did you get there, set it up, and launch without any air? I once was timed at 3.25 minutes for holding my breath, but that would be far too long!
Zack C
Tad, most pilots in this club use weak link configurations that have been tested to break at over 600 lbs. I'm not sure who 'you' in your post is meant to be, but I don't think it applies to anyone in this group.
Henry Wise
That's one (minor) reason why I prefer to foot launch off a hill. As far as the weak link's concerned - it's there for protection in case the winch locks up (been known to happen, all be it rarely).
Bobb Loper
Hi, Tad.
You asked, "Why the hell are you throwing into that can of worms a weak link which blows a hair's breadth over your dialed in winch tension?"
You did not quote any message so I conclude that with your mention of mesquite trees that you are referencing my recent post to a beginner explaining conditions that can warrant an increase in relative wind before platform launch.
I don't believe we have mentioned a "weak" weak link in our club discussions. I haven't and I have reason to think that our members are using links from 1 1/2 G to 2 G, but I have seen and experienced new 2 G links, tow lines and releases fail at any given moment during the launch.
In your past posts to this club, you have been very explicit in your belief of sturdier links, so that ground does not need to be re-ploughed and I have no further comments.
Thank you for your concern,
Bobb Loper
Member HHPA
Mick Howard
And it's there to protect your equipment from excessive loads. It seems that Tad is not a fan of towing. If it wasn't for towing most Houston area pilots would not get any airtime. We all strive to make towing operations as safe as possible but there is a risk to everything we do in life including hang gliding. Is towing more hazardous that mountain launching! Everything is relative. Personally I enjoy all forms of launching hang gliders including mountain flying which I would do more if we had flying sites closer to Houston.
Mark Moore
[HHPA] Tadd
Ahh. Isnt this site for HHPA members only? Why is my e-mail account getting bombarded with uneducated, obviously incompetant e-mails this morning. Forgot who is the moderator, but could you please eliminate this issue. Thanks in advance.
Bobb Loper
Tad is not uneducated. He has probably spent as much time as any pilot studying safety issues relative to platform towing. This site is not limited to HHPA members. Every pilot has questions that should be answered but once or twice through the question should be enough.
Michael Hoffman
I figured Tad was just having some fun on a rant about the way we get in the air. If I was inside on a beautiful day like today, I might have time to shoot out something to get you guys fired up. The shop calls.
Mark Moore
Really? His post doesn't read that way. "mediocre control authority" "erectile dysfunction". If he was harassing some of his buddies...My bad. I havent been able to fly for 7 or 8 weeks due to a neck issue, so I'm quite cranky.
Mark Moore
I just decided to check the USHPA membership roster to make sure I wasnt pissing off an H4/P4 who had fifty years and thousands of hours of flight time, and the only Tad I could find is a P2. Bob, is the pilot who has been studing safety issues relative to platform towing as much as any other pilot?
Charles Schneider
>
I got a question too.
1. You're flying an aircraft over which - even in free flight - you have mediocre control authority.
<
And your point is?
>
2. You're tying it to a rope - which makes it dangerously roll unstable.
<
I am taking medicine for my instability.
>
3. You're ELECTING to use a release system which - in an emergency - requires you to always compromise, often fully surrender any of what may remain of your already pathetic level of control.
<
I hold the tow rope in my teeth (what's left of them), therefore my pathetic flying abilities are exemplified, not compromised.
>
4. You're occasionally taking off in thermally crosswinds from a pencil thin runway bordered by ditches, barbed wire, and mesquite trees.
<
Yeah, but I always close my eyes. Besides, mesquite is the best for BBQ.
>
Why the hell are you throwing into that can of worms a weak link which blows a hair's breadth over your dialed in winch tension?
<
I can bite a lot harder that a hair's a**.
>
Does the adrenalin rush you get from quadrupling the ambient danger level work that much better to cure erectile dysfunction than all those spam remedies upon which I've been wasting my money?
<
About those spam remedies, do they really work?
>
If someone can give me a halfway intelligent rationale (i.e., something MUCH better than the above) for this insane tradition I'll immediately PayPal him a hundred bucks.
<
Since my rationales are at least half-way intelligent or less...SHOW ME THE MONEY!!!
Bobb Loper
MarkM,
I don't know his rate and it does not matter. I have read some of his comments on safety links and from my experience, he is right on money - maybe a little obsessive on safety - but that is not bad. If you go look up membership in USHPA, you will not find my name either. I have shifted my flying to trikes and USHPA does not offer any advantages to me. I still stay active in our local club and spend time with our aerotow club but refuse to spend your hard earned money (my social security) on an organization that will not offer insurance to trike pilots. Don't cut short any paraglider pilot that tows - well, his intelligence may be somewhat impaired by rag wing bias LOL.
Mark Moore
We differ in opinion thats for sure. But I have a great deal of respect for your opinion.
Tad Eareckson - 2010/09/17
Dave,
No, my point is not that sport flight is dangerous. Anybody who doesn't understand that hang gliding is dangerous should've had the tubes disconnected three months ago. My point is usually something along the lines of it's about ten times more dangerous than it needs to be.
Like you said, it's all about managing risk. Have we maxed things out in that arena?
Zack,
If ya'll are really using 600 pound weak links I have renewed hope for life on the planet. But in my neck of the woods they're using 125 pounders and calling them 520s.
Could I trouble you - or anyone willing - for a description of these weak links? (Material, knots, installation configuration...)
Bobb,
Just to be clear...
With the probable and possible exception of the release and weak link respectively, I have absolutely no problem with that tow launch scenario you described. I'd wager that it's about a dozen times safer running a glider out of the slot at Woodstock on a typical flying day.
But in all four of the initial posts this thread you hear a well founded concern about losing the tow just off the truck. In three of them the weak link is mentioned specifically.
And Bob Fisher brings up the issue of weak link versus drum acceleration.
Mick says the weak link is "there to protect your equipment from excessive loads." If, by "equipment" he means "glider", and doesn't add anything to the definition, he is (refreshingly) one hundred percent correct.
I think everyone's in agreement that in that launch situation...
1. You want lotsa power and climb rate to blast through the danger zone fairly quickly.
2. You really don't want the weak link to blow but you hafta maintain enough airspeed so that you're not totally screwed if it does.
So - as you point out - there's a bit of a tradeoff thing going on there.
OK, let's try an experiment...
1. Lose the weak link and make sure everything between the truck and your keel will hold to three thousand pounds.
2. Lose the wind to simplify the conversation.
3. Take the truck up to 40 mph and pull the pin.
4. Deliberately try to break the glider.
I'd predict that it would be physically impossible to get beyond a fraction of what it would take. (Ever see photos of what they do to gliders during ground testing for HGMA certification?)
So what I'm saying is that we've got plenty of things to worry about at launch and winch inertia doesn't hafta be on the list. And can you really blow a weak link about four times the set tow tension as a consequence of winch inertia?
>
...but I have seen and experienced new 2 G links, tow lines and releases fail at any given moment during the launch.
<
How is that possible?
You're setting the tension for - what - about 150 pounds?
Let's call a glider 250 pounds. Two Gs - 500 pounds.
I don't know what inertia can do to you. Can anyone give me a figure or an educated guess?
When these alleged two G weak links are blowing are the pilots FEELING two Gs? Feeling over three times normal tension? Or is everything going fine and all the sudden - POP?
There was a time in hang gliding - before Donnell came along - when people understood what losing the line could do to you and they took that stuff seriously.
It is one hundred percent inexcusable to have an uncommanded release actuation. That little malfunction can - even though it rarely does - kill you just as dead as a sidewire failure.
And, for the same reason, towline and weak link failures should be freak occurrences and regarded as strong evidence that people aren't doing their jobs very well.
Henry,
4:40 - but that was a long time ago.
>
As far as the weak link's concerned - it's there for protection in case the winch locks up (been known to happen, all be it rarely).
<
Lemme quibble with that statement.
Yes, on a payout system a winch lock-up should be a necessary prerequisite for a weak link failure. Assuming that the extra stress you get as a consequence of drum inertia is no threat to the glider - which I do - there's no other way the weak link should be able to blow.
And, yes, it's there for PROTECTION. But you haven't defined protection.
The vast majority of the bozos who tow hang gliders think it's there for THEIR protection. It ain't. It's there ONLY to protect the glider and ONLY to protect it from from positive overloading. It couldn't care less if the glider - and you - rocket up, whipstall, lock out, go inverted, tuck and fail negative, or dive vertically back into the runway. You can do all that stuff just fine with a half G weak link never breaking a sweat.
And just because the winch locking up is a prerequisite for blowing the weak link doesn't mean you should EXPECT the weak link to blow when it does. All a winch lock-up means is that you've instantly converted to static tow mode. And lotsa weak link "protected" folk have found themselves majorly screwed on static tow. Ask John Woiwode just how much damage you can do with tension remaining under 0.8 Gs after the line jams.
Charles,
>
And your point is?
<
If you're gonna take extra risks in hang gliding...
Do it by flying under bridges, pulling loops, and launching and climbing in violent thermal conditions.
Don't do it by not knowing what you're doing and/or using crappy equipment.
>
I hold the tow rope in my teeth (what's left of them)...
<
That sounds like a pretty good concept. You might, however, wanna think about incorporating some mechanical advantage device to step the tension down a bit.
>
About those spam remedies, do they really work?
<
I've tried scores of them - all totally USELESS! All combined they don't hold a candle to the Sears catalog - and that's free.
>
Since my rationales are at least half-way intelligent or less...
<
Sorry, the deal was for better than. I was saturated with or less decades ago.
Zack C
Tad, the standard configuration here is a loop of 205 leech line tied with a fisherman's knot and attached to the end of the release with a lark's head (with the knot at the attachment point).
The weak link loop is pulled through a loop at the end of the tow line and attached back at the release, creating four strands total.
One of our members tested various weak link configurations years ago and reported: "I posted a spread sheet in 2004 on this site (still there) which shows the results of tension testing the standard weak link material (205 leech line).
The break strength depends on age, type of knot used, cross sectional diameter of link and of course number of strands. In general the 3 strand link was good from 260 to 370 lbs, a 4 strand link broke above 600 lbs." I don't see the file anymore however.
I've not tested breaking strengths myself. Weak link breaks are very rare for us and generally only happen at the end of tows (when tension is higher). I don't think I've had a weak link break since I started flying with a radio and requesting pressure reduction when I felt tension rise.
Al Hernandez - 2011/06/25
On one of his not counted flight, Martin broke a weak link at low altitude, causing an 80 ft free flight on his glider, the left wing was up, flew off to the right side of the runway, glider flew over the airport fence, over trees, and house, for a little while, He managed to get his Falcon in control and landed safely back on the airport runway... WHAT A RUSH ! what can I say S#it Happens. Good maneuvering skills Martin.
Yeah Bobb, once or twice SHOULD be enough. But it almost NEVER is.
It especially never is when people are taught a lot of crap on Day One and continually bombarded with dangerous misinformation decade after decade after decade in classes, clinics, flight operations, competitions, magazines, textbooks, websites, discussion groups, and national regulations.
But I'm not hearing you get all bent out of shape when this message:
If you fail to maintain the correct tow position (centered, with the wheels of the tug on the horizon), the weak link will break before you can get into too much trouble.
is repeated untold tens of thousands of times with THESE:
2009/08/31
Approximately ten emergency vehicles were parked all over the runway.
The EMTs were carrying a (presumed) pilot out from under the wreckage of a hang glider next to the runway. They loaded the victim/stretcher into an ambulance, but didn't drive away. Stayed parked on the runway for at least a half an hour. I don't yet know what the outcome was.
Later heard that he was evacuated by helicopter because of a head injury.
Keith P. Skiles - 2011/06/02
I witnessed the one at Lookout. It was pretty ugly. Low angle of attack, too much speed and flew off the cart like a rocket until the weak link broke, she stalled and it turned back towards the ground.
kinds of results.
How come?
And I'm ALSO not hearing you speak up when it becomes blindingly obvious that once or twice WASN'T enough and people in your friendly and incestuous little club are continuing to put themselves in potentially lethal situations. So what the hell good are your friendly and incestuous little club and you actually doing?