http://www.hanggliding.org/viewtopic.php?t=33404
Rapid parachute deployment
Dave Jacob - 2015/09/11 17:01:05 UTC
Dave,
Fuck Dave.
The deployment time of the chute would not be effected...
Affected.
...as the activation load for the screamer can be set above the loaded needed to deploy.
No. It can't. The activation load is preset at what it takes to blow the first row of stitching. And there's no fuckin' way any chute can NOT fully deploy before ANY Screamer starts kicking in. (Two kiloNewtons for all of them.)
What it does is reduce any shock load above a certain point once the chute is open.
Not enough to justify installing it in the system.
If the deployment is gentle, the screamer won't activate.
450 pounds. Good luck.
I agree we are adding complexity which is not preferred.
No you don't. You're preferring to add complexity because you believe it would REDUCE likelihood of failure. And if the Screamer actually worked as claimed you'd be right.
Fuckin' parachute system itself is a HUGE increase in the complexity of the glider assembly. And I'd guess about half the deployments are inadvertent result in a lot of carnage. But I'm not hearing any of these KISS assholes advocating its removal or suggesting that inadvertent deployments are inevitable.
I think it's a personal decision...
Fuck personal decisions. If this sport had its shit together and Screamers actually did what they're supposed to they'd be in the same universal use that deployment bags and swivels are.
...but I would be willing to accept some additional complexity if it mitigates the risk of an event I'm not otherwise prepared for.
Just not when considering release systems that actually work with respect to the simple Industry standard ones.
Some will not and that's fine. I for one was glad to have a swivel installed on my parachute when I deployed as it provided a stable descent so I could maneuver my body to a safe position for impact.
- See? (And I hadn't read ahead on this one.)
- That's not what a swivel does. A swivel prevents spinning glider wreckage from twisting the shrouds and strangling the canopy. People used to die as a consequence of that phenomenon. (Fuckin' incredible that that's what it took to get The Industry thinking about swivels.)
Dave Jacob - 2015/09/11 17:16:23 UTC
That's a good point Red.
All of Red's points have been good since T** at K*** S****** was banned and unable to post that he's full o' shit and explain why.
I think we'd need a special umbilical anyway to do it your way as you are probably going to bar stitch an attachment loop into it.
I showed you how to do it already:
http://www.flickr.com/photos/aerotowrelease/8321440784/
But I failed to refer to it as a special umbilical so I guess it's not legitimate.
So perhaps the extra length isn't an issue. I certainly like that your approach keeps the Screamer from adding a new failure point.
Me too. Red's really excellent at proposing solutions to nonexistent problems.
Cool Breeze - 2015/09/11 18:20:00 UTC
The screamer is just tubular webbing sewn together in "rolling loops" the stitching needs to rip apart, and that's what absorbs the load.
In "theory".
So in theory...
See above.
...the screamer could be made of webbing that is stronger than the rest of the bridal- meaning that you would not have to use in tandem/parallel to the bridal.
- See? It's a bridal - not an umbilical.
- The weak link is the fucking parachute - not any of the fucking webbing. (But trying to explain the concept of a weak link to hang glider people...)
- After the Screamer's blown it's a loop of one inch tubular webbing - 5845 pounds. For a 250 pound payload that's over 23 Gs. What's the chute good for?
If the shock load is not severe enough... screamer does not activate. If the shock load is severe... it activates.
Severe. A little less than what I'd be pulling in a sixty degree banked coordinated turn.
One could design a screamer that could be x amount of feet long to get the job done...
Or one could just use a bigger chute that opened slower.
Red Howard - 2015/09/11 18:54:50 UTC
Cool Breeze,
CAUTION: Tubular webbing should not be used in a parachute bridle, due the the way it is made.
Tubularly.
This is an extremely serious design flaw, in older gear.
But the standard aerotow weak link wasn't. At least not one not worth worrying about. At least not until after one whipstalled Zack Marzec into a tumble at 150 feet.
Consult a parachute rigger or manufacturer for the right stuff.
Nah, do it right and consult Jeff Shapiro.
If an inspection reveals any tubular webbing in any HG reserve bridle, immediately have that webbing replaced with the correct modern webbing.
Or use your fucking brain and install it between the swivel and the parachute where it's not an issue.
Older parachutes may still be found with tubular bridles, so let the buyer beware.
And don't worry that everybody and his fucking dog is now using a Tad-O-Link in conjunction with a Bobby Fucking-Genius Bailey bent pin barrel release.
It may be possible to make a Screamer strong enough to meet our...
...idiot imaginary...
...needs, but until somebody...
...other than T** at K*** S******...
...steps up to say so publicly, I would not assume that any available units will do the job, for now.
Course not. That would require looking at specs and doing grade school level arithmetic. Why do that when we can just wait for somebody - preferably Jim Keen-Intellect Rooney or Ryan Instant-Hands-Free-Release Voight - to step up and say something publicly?
Cool Breeze - 2015/09/11 20:35:47 UTC
Scratch the word "Tubular", just think webbing. You old birds don't take kindly to fresh ideas.
Or intelligent decades old ones.
A screamer type device is the solution to our problem. Simple idea that works.
Like the Rooney Link with its huge track record. 'Cept without any track record.
2015/09/12 00:04:35 UTC - Sink This! -- NMERider
Brian Scharp - 2015/09/11 22:35:19 UTC
Fresh? A 2009 debunking is provided in the links above.
Huh? What? Thought I heard something. Must've just been the wind. Now where was I?
Dave Jacob - 2015/09/11 23:57:45 UTC
Hey Brian,
Are you referring to Jason's analysis from 12/29?
The one that shows that the Screamer doesn't actually do anything? Yeah, that one. But just ignore it 'cause we've just established that it's a simple idea that works.
Brian Scharp - 2015/09/12 00:53:05 UTC
Yes, and this one posted:
2009/11/28 19:52:17 UTC
Red Howard - 2015/09/12 01:59:22 UTC
Cool Breeze,
YOU dredge up a nightmare from our HG past, tubular webbing.
Bull fucking shit. Tubular webbing is ONLY problematic when it's under tension and within range of the flying wires.
I give a serious Caution on that stuff, and so I get "You old birds don't take kindly to fresh ideas"? REALLY? Then you dismiss that deadly concern, rather too casually.
You give serious Cautions at every opportunity to never do preflight stomp tests on the sidewires and then when a motherfucker gets killed right after launch 'cause he didn't do a preflight stomp test (ever) you're nowhere to be found.
If you re-read my posts here, I gave the Screamer concept some careful consideration, and suggested a way that it could help (if it works), and nothing goes bad if it does not. I see that scenario as the best of all possibilities.
Yeah? How 'bout rigging one up and taking some pictures so the rest of us can get things right - the way the sport did with the aerotow release Paul Hurless designed.
For the record, I DO take "kindly" to any new ideas that might improve the safety of my flying community.
I shudder to think where the sport would be without all of your endorsements of new ideas that might improve the safety of YOUR flying community.
Fair and frank discussion (including possible flaws or benefits of an idea) is what we do here.
"WE" certainly do. That's Jack's Living Room has always been such a cauldron of evolutionary progress for the sport. And you've still got time left over to jerk each other off at satisfactory intervals.
Not every idea meets instant approval...
Well, a standard aerotow weak link with a huge track record only comes along about once in a generation.
...but with a little tweaking of the operation, these things may become life-savers.
And ain't it great that we have an institution like The Jack Show to continually drive the sport forward - succeeding where all the equipment manufacturers have failed so miserably.
It can be your mission to present new ideas, and that is fine, but it is not your job to shoot down any "opposition" that you may perceive (wrongly, in this case).
'Course not. It's YOUR job to shoot down any "opposition" to any established Jack Show theology.
Dave Jacob - 2015/09/12 02:24:42 UTC
Hey Brian,
First of, thanks for digging up the threads. But I think 'debunked' is too absolute of a term for this case.
No it's not. It's totally on the money.
I realize its the best we can do in the absence of real data but correlating steady state loads to dynamic events can leave huge uncertainties. Further, every hand calc I saw in your links assesses existing products designed for rock climbers which rely on a dynamic rope (stretchy) and a much shorter fall than we'd experience.
So multiply your Screamer by ten. Then multiply that result by zero.
The concept of using load limiter is a correct approach for minimizing shock loading.
The concept of using a bigger chute and a longer bridle is the correct approach for minimizing shock loading. But then you have to figure out how to get yourself into an Adam Parer situation to justify the extra weight you'll hafta carry around on all the flights you don't get yourself into an Adam Parer situation and hope you don't get yourself into a low altitude situation in which you need to stop on a dime.
I spent six weeks recently analyzing a split rotor failure in a high speed turbine. The resulting torque spike was dropped by a factor of three with a crush zone that collapsed in three miliseconds. It got us down to something we could manage. I believe you are technical so you know system rigidity is the dominant driver in setting the shock load magnitude which in-turn is what causes the damage. The question is not so much whether a load limiter will work. The question is what are the loads and what is the proper design for the load limiter.
Here's another question... Where are the incidents that indicate that this load limiting bullshit is worth spending any time and energy on?
The problem as I'm beginning to understand it (thanks to the help of an unspecified manufacturer) is the relative obscurity of this type of failure (and we are still not sure what happened in Spain)...
One thing we're totally sure about with respect to what happened in Spain... Didn't have shit to do with any shock loading issues. Another thing we're totally sure about... Whatever it was a halfway decent preflight inspection would've handled the problem(s).
...does not justify pulling engineering resources off other programs which have a more significant impact on pilot safety.
Goddam fuckin' right. Preflight stomp tests, hook-in checks, belly landings, releases that don't stink on ice. And think how much better off Craig Pirazzi would've been if just one of the individuals involved in this useless discussion had donated a minute's worth of wire assistance to the launch.
In short, a pilot can add a Screamer or similar device. Assuming they do it properly, they will lower the maximum load provided the deployment generates enough force to activate the device.
And if the deployment DOESN'T generate the approximate two Gs needed to activate the device ya don't really need the device, do ya? ("Damn! Wish I'd been going eighty miles per hour faster so my device would've worked." ""Damn! Fuckin' airbag didn't inflate! Next time I'm heading for a tree I'm gonna stomp on the gas instead of the brake.")
But there is no guarantee it will sufficiently damp the system to avert a failure.
There are no guarantees of ANYTHING good happening after you've done a lot of stupid stuff in aviation.
Until a solution...
...to this nonexistent problem...
...is properly engineered, I think the best policy is to make sure you can get your chute out fast even if that means you have go with a less aerodynamic harness.
Oh! You mean we maybe SHOULDN'T use a harness with a frame that bends and chokes off the deployment port in a tumble? That we should maybe give some thought to properly engineered harnesses before going nuts about properly engineering Screamers? So maybe it would be better to get a chute out at forty miles per hour without a properly engineered Screamer than at two hundred miles per hour with a properly engineered Screamer?
Wow! The Jack Show really DOES have all the really great new ideas that might improve the safety of Red's flying community!
2015/09/12 02:32:39 UTC - 3 thumbs up - Red Howard
Yeah Red. Totally agree. Your flying community is the BEST!
