Weak Links and Tow Bridles

[hefalump]

I had posted this in another thread. It was buried in that thread and many peolpe may have lost interest in that particular thread. MarkC thought it was worth a new topic because it has a cautionary tale and may prevent other pilots from doing something dangerous if they are having weak link cuts.

I remember once at Quest Air Jim Rooney were going over the release procedure with a first time tandem instruction. I was just watching and I learned something that was missed in my Aerotow "training".

Jim showed the student the Primary release on the keel and pointed out the weak link on the bridle at that location. Jim described the function of the weak link. He demonstrated a normal release, then repeated the release procedure, but this time he simulated the bridle knotting it's self to the tow line. "No problem" he said, "now we are towing off the shoulders, either the second weak link on the shoulders will break" and he pointed to it "or we will release with the secondary release", a Bailey on the shoulder and he demonstrated.

At that moment, after towing for nearly 4 years I learned why we do things in a specific order and why the weak links are located where they are.

Now I'm going to tell a story of what happened at Fly In I went to in 2006. No one was hurt but I shutter to think of the "what if's". This is an example of how people trying to "improve" on a design can undo redundancy and safety.

A student was having trouble with his weak link breaking at his primary release at the keel. The release was made by the instructor and sold to the student. It looked just like the "Quest Air" style release with the spinnaker release except he had used the swivel loop on the back of the release to anchor the release to the keel. So the hinge on the spinnaker release was cutting the weak link. The "Quest Air" release, as you are aware solves this problem by off setting the anchor point so the weak link is rubbing against the smooth part of the gate.

The next thing that happened stunned me. The instructor reversed the ends of the "V"-bridle so now the shoulder line went through the weak link on the "V" bridle and the loop on the other end was in the Primary release with no weak link.

At this point I had to chime in, "that's a bad Idea" I said "the weak link is in the wrong place" The instructor snapped back "what's the difference ... there is still a weak link and up there it only gets cut by the release". Maybe I should not have challenged the instructor in front of the student, so I pulled the instructor a side and explained the virtues of the "Quest Air" release. I had mine in the car and said the student could borrow it for the Fly In. I rigged the student’s glider with it and pointed out the offset anchor point. The instructor agreed it was a better design.

The instructor then went off to do more tandem tows.

I tensioned the bridle system to simulate tow forces and said “OK the tow tug pilot just gave you the signal … Release”. He pulled the Bailey style release on his shoulder. I told him I was expecting him to release the primary … he said he did. His instructor said it was better to release from the shoulders first so that the long “V”-bridle would just trail behind the glider from the keel and you would not have to stow the “V”-bridle.

So think about this for a minute … had the instructor reversed the “V”-bridle with no weak link in the release at the keel … the student releases with the release on the shoulders and the “V”-bridle knots it’s self on the tow line. Now he is towing off the keel with no weak link. The nose of the glider would pitch down so fast and violent the student may never get a chance to hit the release on the keel or loose grip of the base tube all together. And with none of the tow forces directed through the pilots harness he would have little control over the glider.

I then ran through the release procedure with the student just as Jim Rooney did at Quest Air.

At the end of the weekend the student returned my release and thanked me. He said he thought about what I had said and he agreed that stowing the “V” bridle was no big deal.

That instructor has since retired … shortly after one of his students died after a training accident last year.

JD


Jim Rooney adds:

Jim Prahl took that idea to task one day too... he wanted to know what would happen if you took out the top weak link and the lines snagged. So he had someone tow him up to intentionally try it... he rigged things so they would snag and released from the shoulders first. What happened next is a bit scary (esp with your story in mind). A glider towing off the keel only goes negative instantly... you flap around in the wind with zero control.

[brianvh]

Good Lord....Prahl did this intentionally?! I guess he was on a strong glider with the tug pilot hair-triggered to give him the rope. Just thinking about the gutsiness of it makes me queasy.

[hefalump]

Without "Test" pilots trying these what if's under controlled conditions we may never know just how bad a mistake like misplacing the weak link could get.

I'm sure the Keel release was operational and he may have had some way to cut the tow line like a link knife for back up. If all else fails he gets the rope.

I wasn't there, but your right, Jim has some guts.

JD

[jimrooney]

It's not like he did it at 5 feet

It did take some cahonez though. I remember him saying that he didn't expect it to be as bad as it was. I'm sure too that it's not as violent as it sounds (but perhaps it was)... what I remember most clearly was "you have no control" and "if I hadn't been able to release, it would have folded the glider". He had -and used- the top release, he just used it second. Yup, there's the tug pilot release and the tug's weaklink too. Jim's not stupid.

If you ever wonder why Quest has a very strict weaklink policy, here's one of the reasons.

[Paul Tjaden]

I also remember talking to Jim Prahl about his "experiment" with tow releases. I recall he said everything went to #### REALLY fast. The reason that this subject came up is that a pilot from Wallaby named Mick flew up one day, landed at Quest and then decided to tow back up and fly home. His "normal" tow bridle was a very thin spectra line running from his keel (or carabiner, can't remember which) to a line on his harness at his chest where his primary release was a barrel on his chest line. Initially, I thought it looked like a pretty good way to use a V system without the need to install a tow release on the down tube but then Jim pointed out the flaw and told me of his experience. I talked to Mick about it later but he was undetered and said " Well, never had any problems with it yet." In fairness to Mick, he DID have a weak link at his keel but I'm not certain I'd want to trust that.

Paul

[Tad Eareckson]

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Having won their confidence, tomorrow I shall test the humor of these giant but gentle primates with a simple joy-buzzer handshake.
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Hey Bob. Think there are any bears in this old cave? ... I dunno, Jim. Let's take a look.
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Whoa! You mean to say that when one, in effect, moves the hang point a foot forward the glider will pass a cinder block on the way down? Who'da thunk.