http://www.shga.com/forum/phpBB3/viewtopic.php?t=4957
Wires
Ken Andrews - 2015/10/17 20:13:14 UTC
Site Admin - Pasadena
Stepping on side wires isn't enough
Hah! I finally found my misplaced copy of Dennis Pagen's "Performance Flying".
Hold on for a minute. I need to get the strips of mine out from the shredder basket and reassemble them.
On page 318, he says that the side wires are under 125 pounds of tension...
Right. Regardless of how much you're clipping into the glider and what you're pulling in the way of Gs the sidewires are under 125 pounds of pressure - I mean "TENSION". Sorry. (Pagen specifies one G.)
...and this number sounds more plausible to me than the 50-75 pounds that the Vimeo author quotes.
- The 50-75 pounds that the Vimeo author quotes are pounds of push force applied to the middle of the wire - asshole.
- The Vimeo author's quoting the Wills Wing owners' manuals - and so clearly states - asshole. And have you ever bothered to read one? Even if you've never flown one of their gliders ya live about thirty miles from their goddam factory ferchrisake.
Moreover, the loads can double in a steeply banked turn or when pulling out of a dive, and they increase even more in wire-slapping turbulence. Hence, I wouldn't go thinking...
Obviously.
...that his "step on it" test...
It's not HIS "step on it" test - asshole. It's the one specified in every manual for every glider by the biggest glider manufacturer on the fuckin' planet.
...is anywhere close to the normal flight loads that the side wires must handle.
Damn! You're right! Good reason not to do hang checks 'cause they only put about one G on the system. Totally awesome reason to keep skipping hook-in checks 'cause you can do those loading the system to under 0.05 Gs.
But let's make damn sure we never test any Industry Standard aerotow releases to more than twenty or thirty pounds direct load before we hook up to the 914 with the new two hundred pound fishing line that Davis has recently become happy with.
While I'm attacking this Vimeo guy...
Yeah, let's attack the Vimeo guy - "the moron in the video" as Doug Doerfler refers to him. He's made a volunteer effort to put a safety message out to the flying public. Are we gonna start tolerating shit like that? Allow these deeds to go unpunished?
...kinks in side wires make me really nervous.
Fly with more of them. That'll help you acclimate.
Such a kink gets pulled straight every time there's tension on the wire, and returns to its bent state when the tension is released. Each such cycle work-hardens the metal, weakening the wire. While a glider is set up on launch and moving around a little in the breeze, it could go through several cycles a minute, just as it does on every step when ground-handling.
Wow. Astonishing that we only see a couple hundred of these kink failures per season.
I'm certainly not against testing the side-wires by stepping on them...
Just FOR attacking the Vimeo guy.
...but it's not sufficient.
Quote me where he, the fuckin' manuals, ANYBODY ever suggested...
http://ozreport.com/forum/viewtopic.php?t=13132
Unhooked Death Again - Change our Methods Now?
JBBenson - 2009/01/25 16:27:19 UTC
I get what Tad is saying, but it took some translation:
HANG CHECK is part of the preflight, to verify that all the harness lines etc. are straight.
HOOK-IN CHECK is to verify connection to the glider five seconds before takeoff.
They are separate actions, neither interchangeable nor meant to replace one another. They are not two ways to do the same thing.
...it WAS.
Visual inspection is necessary..
Fuck that. If you step on a wire you're not allowed to look at it before any given launch. One or the other, dude. You could, however, step on one and visually inspect the other - if that would float your boat.
...and I believe that side wires should be replaced immediately if there are any kinks, and periodically even if there aren't.
What period? Months? Years? Flights? Hours? Loops? Setup/Breakdown cycles? Some number some manufacturer pulled out of his ass and specified in a manual? What's the data to support your period of choice?
Tangent Man - 2015/10/18 02:36:22 UTC
Ken,
If you do the trigonometry and work out the force vectors...
How's he gonna do trig and work out force vectors? He's functionally illiterate as far as the two dozen word text entries in the Vimeo guy's video are concerned and he's never heard of a glider owner's manual before.
...doing a 50# step-on test can produce several times that amount of pressure into tension on the side wires.
It's not like towing? Pressure from a hydraulic brake system or tug prop doesn't translate to towline pressure? You get TENSION?
It is best to pull full VG before performing the test on a topless glider.
Doesn't hurt for ground handling to launch position either.
The less, the side wire sags during the test for any given amount of pressure placed between the side wire and the leading edge...
Let's call it force. We're not so much dealing with PSI here.
...the greater the amount of tension load on the wires. The primary purpose of this test is to insure that the glider does not fold up immediately after launch and result in a serious or fatal accident such as the one up a Fort Funston recently.
The fucking genius at Funston referenced by the moron in the video at the nine second mark.
Perhaps you recall the incident about five years ago when a certain Sylmar pilot made a high speed pass over our LZ on high Litespeed that was equipped with overage 2mm side-wires? His right-hand side-wire failed when he pulled up resulting in loss of roll authority followed by a long spiral into the wash, broken bones and aluminum.
I'll bet the chicks were really impressed.
Had this pilot performed the simple side-wire stomp test before launching there is a good chance his compromised side-wire would have failed before he took to the skies.
But not an absolute guarantee. Therefore we really shouldn't be doing this check at all lest it give us a deadly false sense of security.
Yes, you are correct in assuming that visual inspections for kinks, corrosion, abrasion and other damage is very important.
DAMN straight! I nominate him for a u$hPa/NAA Safety Award! Maybe I could get a second from Dan DeWeese or Steve Exceptionally-Knowledgeable Wendt?
But not all damage is visible and can occur inside the Nico-press sleeve and elsewhere.
That's an old wives' tale. If you can't see any damage it obviously doesn't exist so why waste valuable time testing for it when you could be doing extra hang checks and making sure you have your backup loop and your carabiner's locked?
And so stressing the side-wire to 100 to 150# of tension during pre-flight by stepping on it is not a bad idea and only takes a few seconds.
So does buckling your helmet. Do you really wanna use those few seconds to check for a critically defective sidewire when you could be buckling your helmet?
This pre-flight check is in every Wills Wing owner's manual I have ever read and that is how it found its way into Jan's video...
Bullshit. It's in the moron in the video's video and that's how it found its way into every Wills Wing owner's manual you've ever read. Dontchya think that if it had been in every Wills Wing owner's manual you've ever read all along that everybody would be doing this already?
...even if he did not explain all the force vectors adequately.
You mean the way the Wills Wing manuals don't at all?
Jim Thompson - 2015/10/18 03:44:31 UTC
That certain pilot's wires probably would not have failed, if he had followed the prescribed maintenance interval. The wires were the same age as the glider: 6 years old.
Just PROBABLY? Not "No fuckin' way they could've failed with a Day One new glider right out of the bag."?
Even if the wires passed the 'stomp' test, I doubt any of us would put as much pressure on the side wires as we may encounter in flight.
SEE! Toldyaso. Nobody do the stomp test - EVER!
What do the manufacturers have to say about testing wires before flight?
RTFM - idiot.
How do manufacturers test wires before installation or release for replacement?
I dunno... How do manufacturers test downtubes and leading edges before installation or release for replacement?
Tangent Man - 2015/10/18 05:18:17 UTC
Those 2mm side wires were rated for 50 hours before replacement according to the Litespeed manual.
Based upon WHAT data? Are they bench testing two millimeter wires to failure at 49 hours and determining that that's the bottom end of the acceptable limit?
Even standard 3/32" side wires are recommended to be replaced each year.
Or for Moyes fifty hours or six months - whichever comes first. A great deal of these schedules is determined by which ass the numbers are being pulled from.
The stomp test is good enough to allow the pilot to launch and get far enough away from the hill to use his reserve in the event of a failure.
EX fuckin' ZACTLY. Now be prepared to get banned for injecting a little ten year old kid common sense into a Grebloville discussion.
Jim Thompson - 2015/10/18 16:15:41 UTC
The stomp test is good enough to allow the pilot to launch and get far enough away from the hill to use his reserve in the event of a failure.
That's very
comforting...
Yeah, like
knowing your .45 isn't loaded. Don't fall for this bullshit, Jim.
...Jonathan.
Oh. That's Jonathan.
I'm going to check with another source about manufacturer's testing.
Dumb shit. They're nine hundred pound wires doing a job that never gets up to a third of that capacity. The fuckin' gliders are certified to over six Gs and when gliders are blown up in blown aerobatics it's a cross spar or leading edge section that goes - NOT a non defective or damaged sidewire.
As I think you know, there have been failures of new wire sets, too.
- A "SET" does not blow. A single WIRE does - pretty much invariably at or near a nico as a consequence of shit glider manufacturer production and quality control or user abuse.
- There's NEVER been a failure of a properly swaged and unabused wire.
Anyway, both you and Ken are correct: check everything, be nice to your wires when packing up and adhere to mfgs. maintenance intervals.
But DEFINITELY *NOT* the relevant preflight procedure specified in the fuckin' owner's manual if the manufacturer is Wills Wing 'cause that would be inconsistent with attacking the Vimeo guy.
Note, people of varying ages, that neither Joe Greblo nor Rob McKenzie, both local Wills Wing dealers, nor anyone from Wills Wing itself has bothered to contribute two cents worth to this discussion.
So what would've been more likely to save Rafi from getting killed at Funston a couple months ago? A reprint of Mike Meier's "Why Can't We Get A Handle On This Safety Thing?" article? Or a new nuts and bolts article on this stomp test specified in all of his company's manuals and how this isn't just a casual suggestion that pilots should be able to take or ignore as they please?
My take...
"Setting up and preflight the glider and harness including familiarity with owner's manual(s)" is a fucking Hang One requirement. If someone's heading to launch on a Wills Wing glider after having omitted the stomp test he should have his rating suspended. But this is u$hPa hang gliding so you only get your rating pulled if you're caught in the setup area clipped in without a helmet buckled on. And you just hafta be FAMILIAR with the fuckin' manual - you can skip every check in it and just note your sail color to make sure you're not flying someone else's glider for your preflight.
