weak links
Martin Henry - 2009/04/26 16:23:56 UTC
Tad,
Its astonishing how manage to take a simple short little piece of string and and stretch it into an 11 page (and still going) thread
Like George says, your posts are getting better and there is some actual "content" , still, for some strange reason I can't help but click on your posts once in a while, like putting on some Abba tunes and never admitting I liked the music...
The reason I thought I would post is, well your very caught up in your end of the towline you seemed to be in a bit of a battle with the guy (or gal?) on the other end of the line. I have absolutely no challenge to your 1.4 mass weak link (Mainly because there is only so much time I can dedicate to string...) but... If the guy on the front end of the line does not like it, then I think you should respect their side of the argument?
Trike Tug pilots (most), Bailey Tugs with the smaller two strokes or anything that is simply underpowered have a pretty small margin of safety when it comes to the towing envelope. It's a complicated balance. I've heard the expression, "it's like flying two aircraft at once". Getting your tail hauled up, down, left and right buy less then cooperative customer can be down right nerve wracking. If your tug pilot wants you on a "weak" link, you should respect his wishes. If you don't like it, find a tug pilot that can handle the challenge. If he's a lousy tug pilot, he will sooner or later be out of business, If he's good, pilots will line up to be towed. My point there are two aircraft involved. If your being towed up by a big 914T your tug pilot might be able to muscle his way out of a problem, but if he's driving a wheeze two stroke he simply may not have the power to put up with much trouble caused by a strong weak link.
For a sad example of what can happen to a tug when things go wrong...
In Washington State a few years back a Sailplane operation had Tug go down. During the roll, the Spoilers "popped" open on the two seater sailplane (with student at the controls). The Tug pilot sensed a problem as the tow progressed... things where simply not happening as they should. He glanced back and saw the spoilers open. He should have given the glider the rope. He didn't, he powered hard into the tow and got on the radio and screamed at the student to get his spoilers closed. There was plenty of energy building and the student realized his error and slammed the spoilers shut. The glider, now with speed, ballooned rapidly and the student did not react fast enough to compensate, shooting way too high. The high tow position, Tug at full power (trying to power his way out of the problem) the glider was pitching the tug down. The rope/weak link failed. The Tug still low to the ground at full power, close to stall, nose down, drove straight into the rough ground off the end of the runway and the Tug pilot was killed.
Flying a Tug with a heavy customer at the end of the towline is a ballet dance with a fat lady, you have to do it right or somebody could get killed.
Now its back to my "Abba's Greatest Hits"...
Cheers
Martin
http://ozreport.com/forum/viewtopic.php?t=24846Tad Eareckson - 2009/04/26 20:05:29 UTC
Martin,
That short little piece of string (which - in my opinion - should not even be a short little piece of string) can/has/will kill people when it breaks at the wrong time, causes total havoc in flight operations, and is virtually NEVER required for the safety of a flight. (Notice the total dearth of posts from people with evidence to the contrary?)It's not mine. This is pretty much an aviation standard outside of the inbred little world of hang gliding.I have absolutely no challenge to your 1.4 mass weak link...I generally find that virtually no one in the sport on EITHER end of the line has enough of clue about the purpose of a weak link to BEGIN to present a hint of a side of a rational argument. The vast majority don't even have a clue as to the breaking strengths of what they're using or how these strengths translate to tow line tension.If the guy on the front end of the line does not like it, then I think you should respect their side of the argument?Sorry but - BULLSHIT. USHPA defines a safe upper limit of two Gs but was too stupid to define a lower end at which things become dangerous. I SAY anything much south of 1.4 is DANGEROUS to me and it's his job to make sure I don't get stuck with the rope in the event that things get really far outta hand - which ain't never gonna happen anyway.If your tug pilot wants you on a "weak" link, you should respect his wishes.
If you assume that the tug's release is rusted shut the back end bozos who can't get to their releases are the ones who present the biggest threat to both planes - but we never hear much about them 'cause majority tends to trump common sense.And this is pertinent to the discussion HOW?In Washington State...and the Tug pilot was killed.
In Washington State the planes are REQUIRED under federal law to be connected with a line and/or weak links which hold to a MINIMUM of 0.8 Gs. The part of your paragraph giving any indication that this situation either progressed above that tension or needed to to achieve the end result is completely absent.
The tug was killed, not as a consequence of anything above what needed to be and probably was only minimal tension, but as a consequence of how far out of position the sailplane was and how quickly it got there. If the rope was strong enough to get the sailplane aloft at all - it was also strong enough to let the glider kill the tug.
Now to this part of the paragraph...Once again with emphasis...He should have given the glider the rope.but...HE SHOULD HAVE GIVEN THE FREAKIN' GLIDER THE FREAKIN' ROPE.He didn't...http://groups.yahoo.com/group/skysailingtowing/message/4633http://www.dynamicflight.com.au/WeakLinks.html
In all aviation the pilot is usually the weakest link...
Weaklinks and aerotowing (ONLY)In sailplaning it's ALWAYS the tug that gets killed and NEVER the glider.Steve Kroop - 2005/02/10 04:50:59 UTC
Weak links are there to protect the equipment not the glider pilot. Anyone who believes otherwise is setting them selves up for disaster. The pilot activating his or her releases is their way to save themselves.
In hang gliding it's just the opposite 'cause the Dragonfly's control authority blows the glider's away and the latter can't get out of position fast enough to do any real damage.I'm NOT a heavy customer - I'm two hundred pounds under some of their tandems.Flying a Tug with a heavy customer at the end of the towline...
Take a chance on me...
Is this a joke ?
http://ozreport.com/forum/viewtopic.php?t=24846Zack C - 2011/08/31 02:45:17 UTC
Also...isn't it is not so much the magnitude of the tow force that endangers the tug (and glider) pilot but rather its direction? As a tug pilot, would you rather have 500 lbs pulling straight aft or 240 pulling straight up? Could not even a glider using a 130 lb Greenspot loop put the tug pilot in danger?
Is this a joke ?
And when I ask the question of Martin and Zack asks it of Rooney the response we get is EXACTLY the same.John Fritsche - 2011/08/26 06:07:24 UTC
I intentionally broke a weak link by severely and intentionally locking out on aerotow at about 2,000 feet. Why I did this is a long story. But the weak link served its purpose. As I was locking out, I was forcing the tail of the tug up and sideways in a big way, and the tug pilot said he was about to give me the rope when the weak link (at my end) snapped.
...