The Bob Show

[Tad Eareckson]

http://www.ushawks.org/forum/viewtopic.php?f=17&t=1081
Platform towing /risk mitigation / accident

Bill Cummings - 2012/07/20 05:11:46 UTC

When towing:
Where will I find the sweet spot? How big will it be? Does it change in size for any reason?

The towing sweet spot will be found downwind of the tow vehicle of course.
If the wind is right smack dab down the center of the runway/tow road being in the sweet spot is straight forward. Just stay directly behind the truck.

The sweet spot will be very narrow right after platform launching. In other words if you get just a little to the left or right of the tow vehicle with a short rope to the tow vehicle you can find yourself locked out in no time at all.

You're also pulling out line at a predetermined and constant tension so if you happen to stray a bit out of the sweet spot a lockout is a far from a foregone conclusion.

The more towline/rope that you have between the tow vehicle and your glider the wider, left and right, the sweet spot will be.

So maybe racing the vehicle away from the glider shortly after it launches isn't a totally terrible idea.

When you increase the towline tension the sweet spot narrows.

And the glider can climb more quickly and at a higher airspeed through the kill zone so there are some tradeoffs involved in that one as well.

At times a spool with too much rope on it will allow the towline to dig in and prevent the spool/reel from paying out rope. This will increase you line tension and narrow your sweet spot.
A warped disc brake can drag and change the line tension.
If a rag or glove blows in between the chain and sprocket of your rewind or in between your pulley and belt of a rewind this can lock up the winch/reel.
If the chain climbs a worn sprocket it can lock up the winch.
If you splash through a big puddle on the dirt road and get dirt on the disc that will increase your line tension by causing more friction between the disc and brake pads. Believe me there are many more things that can happen to increase the line tension and reduce the size of the sweet spot that you were enjoying.

How many that are unpredictable and/or unavoidable?

With enough time anything that can go wrong probably will.

Then maybe we really shouldn't be flying. Or maybe we should should go into Stuart Caruk mode and throw in a three quarter G weak link and assume that it'll solve whatever problem we may encounter - without causing any of its own in any circumstances we may encounter.

But we can all adopt procedures the will answer all of the known probabilities.

Hey, here's a thought...

- We use platform launch systems so the crew members - the guy under the glider and one(s) on the vehicle - can control the tow according to their judgment and decisions.

- When we have malfunctions which result in deviations from the flight plan - vehicle speed, airspeed, tow tension, tow angle, glider attitude, people can die (as Sam, Martin, and Terry so recently and definitively demonstrated). They can die just as abruptly and permanently as they can as a consequence of a sidewire failure or unhooked launch.

- Problems with warped disc brakes, loose rags and gloves, and worn sprockets can be at least as easily and totally taken out of the equation as sidewire failures.

- Ditto with respect to towline, weak link, and release failures.

- And it's not like puddles jump out in front of us without warning.

- So let's point these risks out, put them on the preflight checklist, and then not discuss them any more.

- Line dig - we can greatly mitigate that risk.

I have noticed operations that have strayed from good procedures.

Things that can be done to mitigate things that Murphy will throw at you follow.

With the possible the possible exception of a line dig, you haven't mentioned anything that Murphy's throwing at us that we can't stop him from throwing at us.

Murphy's Law states that anything that CAN go wrong WILL go wrong. And in aviation we can't afford to have things under our control going wrong 'cause we've got all the variation and unpredictability we need getting thrown at us by Ma Nature.

So if we can make the fuckin' one point bridle so short that it's incapable of wrapping...

http://www.hanggliding.org/viewtopic.php?t=14230
pro tow set-up

Jim Rooney - 2009/11/02 18:58:13 UTC

Oh it happens.
I have, all the guys I work with have.
(Our average is 1 in 1,000 tows)

...we make the fuckin' one point bridle so short that it's incapable of wrapping.

And there's a corollary to Murphy's Law that says that if something can go wrong it will go wrong at the worst possible moment.

Oh yeah... an other fun fact for ya... ya know when it's far more likely to happen? During a lockout. When we're doing lockout training, the odds go from 1 in 1,000 to over 50/50.

And the assholes at Ridgely are pretty good at proving that one right too.

I don't think accelerating through the launch window speed is a good idea.

I'm not particularly interested in what you...

Stuart Caruk - 2010/03

Most reliable sources believe that a weaklink should be sized so that it breaks at 75% to 100% of the inflight load.

...or anyone else thinks or believes. Gimme some numbers, data, logic, hypothetical situations.

At my altitude my launch speed with no wind is a steady 32 miles per hour (double surface glider not a Falcon). At that speed and not hooked to the towline I can launch and climb to thirty to fifty feet behind the truck, round off the climb and land on the road again as the truck goes away still at 32 mph. The Sweet Spot never even enters the equation.

Hooked to the towline I prefer to launch with low tension. Just enough to keep the winch from back lashing. When I stop climbing the preset tension is allowed to be applied to the towline. For the low tension launch I am almost totally in free flight. The towline has very little affect on me. Once the preset tension is applied I now have to concern myself with staying in the sweet spot. Which will be much broader with all the line I have pulled off of the winch/reel.

So it sounds like your doing and benefiting from some measure of what you're criticizing here:

Bill Cummings - 2012/07/18 05:45:32 UTC

And another thing, -- darn it!-- What is with all the Youtube video's of experienced tow people dashing out from under the glider and paying out rope until the tow vehicle has a fifteen degree angle on the tow line to the ground?

And I'll bet you're doing it and getting along just fine...

If you want to do that use a rope to the keel so it won't wallow and tip stall because of too much angle of attack. (AOA).

...without benefit of a two point configuration.

But are we seeing any launch incidents precipitated by people blasting off from the platform with lotsa speed under lotsa tension?

Zack C - 2011/03/04 05:29:28 UTC

As for platform launching, I was nervous about it when I started doing it. It looked iffy, like things could get bad fast. I've since logged around a hundred platform launches and have seen hundreds more. Never once was there any issue. I now feel platform launching is the safest way to get a hang glider into the air (in the widest range of conditions). You get away from the ground very quickly and don't launch until you have plenty of airspeed and excellent control.

Accelerating through the launch window can have me launching with too much speed if I miss the release the first time with some rigs.

1. If you miss the release the first time there's no one holding a gun to your head forcing you to launch with too much speed.
2. What? People can't even design nose releases for the rig which can be reliably blown at will?
3. There've been a lot of people who've missed tow releases the first time who didn't get chances for second shots in time for them to matter.

I prefer to radio to the tow vehicle, "Clear!" Have them trip the nose release. Then when I see that I'm free of the nose release I rock back anytime and launch. You need hand holds for this to keep you in the launch yokes.

It 12:02 am here in Minnesota so I'll try to finish this after my road trip. (Second try first attempt didn't work.)

That's OK, Bob's entire little organization experiment isn't really working either.

[Tad Eareckson]

http://www.ushawks.org/forum/viewtopic.php?f=17&t=1081
Platform towing /risk mitigation / accident

Sam Kellner - 2012/07/21 02:09:24 UTC

OK Bill,
Say a pilot is in this position, "to the right or left", just after platform launch.

WHY is the "pilot" in this position, "to the right or left", just after platform launch?
- Was he blown there?
- Did he fly there to find out what would happen?
- Or is he just unable to fly a glider under anything resembling adequate control?

Now, one of the bits of advice I was given, by email, before I ever PL towed, was " don't try to out fly the vehicle".

1. Who sent it to you?
2. Must've known you pretty well to realize you needed a bit of advice like that.
3. Did he also give you a bit of advice not to roll the glider into a vertical dive?

Say in addition to being "to the right or left", say the pilot "trys to outfly the vehicle", and that reduces the climb.

Say, why would anyone be towing a "pilot" who, in addition to being "to the right or left", "tries to outfly the vehicle" and reduce the climb?

A pilot being in this position would be on the fringe of the "sweet spot", if that, I'd say.

A "pilot" being in this position would be so far out of the fringes that it wouldn't even be worth talking about. But that shouldn't have come to any great surprise of anyone who knew Terry and the Southwest Texas Hang Gliders anyway.

How would this effect the chances of a lockout or loss of control?

Why I have absolutely no idea, Sam.

http://farm9.staticflickr.com/8143/7462005802_bbc0ac66ac_o.jpg


What do you think?

Thanks for the help.

Yep. Better late than never.

[Zack C]

So, to be clear, the answer to my question is 'nothing'? I guess I was confused by your response of "Fine. Then don't tow low airtime pilots using that technique" to his "It [low towline angle] will stall a tip easy with a low airtime pilot"...I thought that might have been a validation of his statement. Anyway, the only disadvantage I'm aware of using a low angle is eating up runway/road quickly.

It's a no brainer that an absolute minimum of ten percent of all aerotows terminate in standard aerotow weak link failures...

I've talked about this before, but our operation is nowhere near that...maybe two percent.

Zack

[Tad Eareckson]

So, to be clear, the answer to my question is 'nothing'?

I'm gonna say yes.

I guess I was confused by your response...

You're right. It was poorly/not thought out. My excuses...

- Bill's got his shit together about a hundred times better than your average asshole in this game and I dropped my guard. Shoulda jumped on that one.

- I've gotten rusty with respect to the vector diagrams I packed into my head when I was debunking all of Donnell's assumptions, diagrams, and explanations.

But I just scribbled some more vector diagrams to help rethink things and I'm gonna say that:

- Angle of attack and pitch attitude will be identical for one point and two point with the top end anchored at the hang point - or at any point on the suspension.

- For the above conditions:

-- angle of attack will be the same as it would at for free flight but airspeed will be higher 'cause the glider is effectively heavier; and, of course

-- pitch attitude will be higher 'cause effective gravity is partially forward.

- Under two point, angle of attack doesn't decrease / airspeed doesn't increase until the anchor point is moved fore of the hang point and some of the tow tension is used to effect negative pitch control force.

If you ever get bored enough at Columbus...
- Stitch a couple of webbing loops to the halves of your hang strap just below the sail.
- Anchor your two point release to them.
- Crank a GoPro tight to a wing and zoom it in to get rid of the fisheye.
- When you're nice and high let the glider trim.
- Take another flight one point behind the same tug and driver.
- Compare horizons.

It would be a good complement to your adverse yaw video.

...maybe two percent.

Let's compromise - six percent.

This:

http://ozreport.com/forum/viewtopic.php?t=24846
Is this a joke ?

Jim Rooney - 2011/08/28 19:39:17 UTC

The frustration of a weaklink break is just that, frustration.
And it can be very frustrating for sure. Especially on a good day, which they tend to be. It seems to be a Murphy favourite. You'll be in a long tug line on a stellar day just itching to fly. The stars are all lining up when *bam*, out of nowhere your trip to happy XC land goes up in a flash. Now you've got to hike it all the way back to the back of the line and wait as the "perfect" window drifts on by.

I get it.
It can be a pisser.

is what I remember and smolder remembering from Ridgely.

- Going out on stellar days and getting blown out of the sky when my 260 pound standard aerotow weak link improved the safety of the towing operation.

- Going out on stellar days after debunking 260 pound standard aerotow weak links and spending them baking in line while those assholes kept putting 260 pound standard aerotow weak linkers back in front of me...

http://ozreport.com/9.033
Why weaklinks?

Davis Straub - 2005/02/08

Competition pilots are driven to use strong links because breaking a weaklink causes them to go to the back of the line as well as the problems that come with broken weaklinks low. If we want to use weaklinks, we need to be sure that we are not penalized if our weaklink breaks.

...to reward them for their superior judgment with respect to the safety of the towing operation.

[Tad Eareckson]

Oops. Missed a spot.

Anyway, the only disadvantage I'm aware of using a low angle is eating up runway/road quickly.

Isn't there some trick they use to get more out of the runway in the wind?

Spitting a bunch of line out early by flooring it then slowing down and cranking up the pressure when the glider climbs through the gradient and creeping along letting the wind do the work?

[Zack C]

Isn't there some trick they use to get more out of the runway in the wind?

Yes...this technique is described in Towing Aloft under 'Slingshoting' (page 194). It does seem like we're able to achieve higher altitudes using it, but there's a lot of guesswork involved in attempting to optimize the tow, especially since both the ideal parameters and the resulting altitude depend so much on conditions (which can vary between successive tows).

Zack

[Tad Eareckson]

This is why God gave us aerotowing. (If only he hadn't given us a flock of hellbound total douchebags to implement and control it for all eternity.)

[Tad Eareckson]

http://www.ushawks.org/forum/viewtopic.php?f=17&t=1081
Platform towing /risk mitigation / accident

Bill Cummings - 2012/07/23 19:37:34 UTC

Only have a few minutes here in Topeka.
When a pilot overflies the vehicle they are usually holding on too much speed.

Do ya think?

This high speed can induce adverse yaw.

"Adverse yaw" - of which Donnell has an extremely imaginative understanding - is his explanation for why when a glider with his two to one "center of mass" bridle is pointed in the wrong direction the sideways force tends to pull the pilot over to the correct side to make the it turn naturally in the proper direction.

(If you find that your glider doesn't autocorrect when you're headed in the wrong direction try anchoring your Hewett Bridle's upper attachment to your cross spars junction - that's a lot closer to the glider's center of mass than the usual keel attachment and should take care of the problem.)

PIO will exacerbate the loss of control.

Do ya think?

Pushing out to slow down will pull more line off of the winch and stop the adverse yaw.

Adverse yaw my ass. Towed hang gliders - no matter how you hook them up - are roll unstable.

The loss of control can be more a result of over speed and not so much out of the sweet spot in the situation you describe.

Once the adverse yaw gets you way off to the side...

Yeah Bill, the ADVERSE YAW. Sweep has no effect in checking adverse yaw when you're on tow and seems to affect people who can't fly a lot more than it does those who can.

...then the lock out will not be preventable. Release is then the next thing to do.

So what's the next thing to do after you release? Oh, right...

Hang Glider Lock-Out!
http://www.youtube.com/watch?v=fnrh9-pOiq4
MorphFX - 2011/03/20
A hang glider pilot learning to aerotow starts a mild PIO that leads into a lock-out.
dead
02-00319
http://farm8.staticflickr.com/7523/15601000807_705ab49977_o.png


http://farm6.staticflickr.com/5606/15600335029_3c234e6828_o.png
14-03708
http://www.kitestrings.org/post6995.html#p6995

So what's the next thing to do after you stall if all this happens early in the tow? Oh, right...

http://farm9.staticflickr.com/8143/7462005802_bbc0ac66ac_o.jpg


Never mind.

Did I stay on track with your question?

A lot better than the Southwest Texas Hang Gliders seem to be able to stay on track with a platform tow.

I may be off line for a while---

Then how are you planning on experiencing the incomparable thrill of free flight?

I think anybody who wants to experience the incomparable thrill of free flight should get on line as soon as possible. There's really not all that much to it and the people at both ends of the string can usually wing it well enough.

And hell, if not, the people who were on the front end of the string can use the flight as a topic for productive discussions like this one.

[Tad Eareckson]

http://www.ushawks.org/forum/viewtopic.php?f=2&t=788
P2SPG and P2SHG Partial Second Surface

Rick Masters - 2012/07/25 03:03:46 UTC

Bob, I simply ran out of money and closed my Mythology of the Airframe web site.
No paraglider pilots ever contributed to its upkeep.
They don't want to hear the truth.
That's very important to them.

No people who had experienced tragic loss contributed.
It was too late.
I fully understand this.

A few hang glider pilots did help, and I appreciate that.
They understood that it was really, really important.
But when only a handful realize this, it doesn't matter.

And a green power paraglider pilot who had never experienced freeflight contributed an impressively large amount when he realized that what he was getting into was a whole hell of a lot more dangerous than he had been told.

And you don't think that's EXACTLY what's been happening in hang gliding...

R.V. Wills - 1976/10

Because there was some feeling that people involved in hang gliding, and people observing the sport from outside, should become preoccupied with accidents and fatalities, the editor of Ground Skimmer asked me to refrain from submitting accident summaries on an every-issue basis.

...almost from its birth?

Like many others, he thanked me for saving his life.
I feel sad that this limited amount of funding couldn't keep the site going.

A lot of other people thanked me for saving their lives.
But they didn't help with the expenses.
Life is cheap.
Paragliding makes this clear.

And lemme congratulate you on all of your efforts to try to save Terry's life. You were SO close.

I wish I had some skin in the game but I stopped flying in 1987.
I've given all I can.
It wasn't enough.
Paragliding will destroy hang gliding.
You guys FUCKED YOURSELVES.
And now you have been fucked by the people you turned your sport over to.
It was the greatest sport that had ever been created by man.
I firmly believe that.
It's too bad that most of you don't get it.
Many of you helped engineer the entire debacle.
And my opinion of most of you freeflight pilots these days is pretty low.
The pilots I flew with in the 80's would never have allowed this to pass.
When you hang glider pilots gave away negative loading to welcome in the paraglider, you sacrificed every gain we've fought for since the 1970s.
HOW COULD YOU DO THAT????
That was stupid and unforgivable.
You threw away your sport.
You need to fight to live.
It's Darwinian.
Don't you understand?
It's not like you don't deserve what's coming.
You have my condolences.

Bob Kuczewski - 2012/07/25 16:08:25 UTC

A lot of other people thanked me for saving their lives.

That's a pretty big deal, Rick. That's worth continuing the effort.

Yeah Bob, and I've always had the greatest respect for your tireless pursuit of improving safety in hang gliding.

It was the greatest sport that had ever been created by man.
I firmly believe that.

I do as well. When I'm having a great flight, I will often thank the people who helped me learn to fly and those who built the sport. I may not know all their names, but my thanks goes out to them just the same.

And isn't it just wonderful how they got everything so perfect that there really hasn't been left worth improving on in the past quarter century.

You threw away your sport.

It's not fair (or even correct) to lump all hang gliding pilots into one group. There are those who are passive and "threw away" the sport, and there are those who are fighting to save the sport. Which group would you like to help?

Before I answer, Bob, why don't you tell me which group you're counting yourself amongst and give me a list of names of the central people in it.

[Tad Eareckson]

Hey Bob,

I heard you deleted a post Al Hernandez entered in the Hang Gliding General forum critical of Sam for his making a good decision in the interest of Terry's safety.

What will keep the US Hawks from becoming another USHPA or HGAA?

You will ... hopefully. The price of freedom is eternal vigilance. Everyone has to do their part once in a while. If you see something that's not being done correctly, then it's your duty to speak out. One big difference between the US Hawks and other organizations is that the US Hawks really does honor the free speech of its members.

Any comment?