Nimbus 4DT accident 31 July 2000 in Spain.

Ian Johnston wrote:
On Tue, 5 Jul 2005 10:54:57 UTC, Bill Gribble
wrote:


As far as character is concerned, I'm pretty certain the last time I
launched an ASH25 (as signaller, at least) it was on a black link. Or it
would have been if that was what the pilot had asked for.


Would you launch a K8 on a black link if the pilot requested it? In
the old days, would you have signalled "all out" to the winch driver
if the pilot requested it and despite open brakes? Would you launch a
glider with a faulty back-release if the pilot said "Oh, that's OK,
just launch me."

I don't think /anyone/ on an airfield is entitled to overlook a clear
safety risk of this sort.

Ian

Experience at two clubs - one uses weak links, other not.

Tost weak links are expensive ,and difficult to come by in our backwater. But
both clubs have pretty much the same cost on weak links.

We launch our entire fleet on the Red link (although the book says some of our
ships are OK for Black)

In the last three yeast we have not had a single weak link failure. In both
cases the wire used is 1930Mpa class C, put a knot in it (unavoidable as it has
to connect to the parachute) and you have an automatic reduction in strength to
under the strength of a black link.

At the other club an engineer member with an enquiring mind put the various tost
links specified for the club and private fleet on a tensiometer attached to a
piece of wire with the standard four turn knot in it. Even the blue link
survived the test. Conversely, there were a number of dangerous launch failures
with the Twin Astir breaking weak links.
Subsequently said club has steadfastly refused to use weak links, for many
thousands of launches - with a powerful winch.

Bottom line is , if you keep the speed in the correct range, and have a sane
cable strength, you are unlikely to need a weak link. By the time the weak link
/ cable breaks your structure has already transmitted the load.

Personally I prefer having a weak link in place, but I don't really believe that
it helps much.

--
Bruce Greeff
Std Cirrus #57
I'm no-T at the address above.

Ian Johnston writes
Would you launch a K8 on a black link if the pilot requested it? In the
old days, would you have signalled "all out" to the winch driver if the
pilot requested it and despite open brakes? Would you launch a glider
with a faulty back-release if the pilot said "Oh, that's OK, just
launch me."

No, absolutely not. And I agree with you, to a point; I would consider
it a moral obligation to make my views known and then not participate in
a launch (or any other aspect of the flying operation) that I considered
unsafe.

I frequently fly a Ka8, so know that it takes a blue link. If somebody
asked for a black, I'd laugh at them and, on realising that they were
serious, refuse.

If I can see the airbrakes are unlocked, of course I'm going to stop the
launch, at it happens, irrespective of my role (or otherwise) at the
launch point.

Faulty back release? Again, being aware of it, no.

ASH25 on a black link? I wouldn't know any better, if that's what the
pilot asked for. Knowing now that it should be a brown link I'll likely
mention it to the pilot concerned if I come across such a situation in
the future, but if the pilot insists on black, I suspect I'd defer to
his judgement in such an instance and use black.

A black link instead of brown is a whole different magnitude to black
instead of blue, or open brakes or an obvious and known fault with the
back release.

I don't think /anyone/ on an airfield is entitled to overlook a clear
safety risk of this sort.

Obviously safety on the airfield is paramount and the responsibility of
all. The main point of my original answer to your "character test" was
to observe that, in our operation at least, the winch driver wouldn't be
aware of which link was being used at the other end of the field.
Moreover, the launch marshal would, in many instances, be reliant upon
the pilot to identify the correct link required.


--
Bill Gribble
http://www.scapegoatsanon.demon.co.uk
- Learn from the mistakes of others.
- You won't live long enough to make all of them yourself.

Is there any commonly known way to test a weak
link non-destructively (other than launching a glider)?

At 13:06 05 July 2005, Bert Willing wrote:
The book says it should be red. And as long as I'm
operating my private
ship, it's me who is responsible for which weak link
I ask for. Launch
marshals may comment on that, but not decide. Winch
drivers are told which
glider is on the other side of the rope, and when they
should start to pull.

I have seen (from the ground) quite a couple of critical
situations
resulting from fatigued weak link breakage, and I prefer
to watch angle of
attack and speed, and pull the knob myself if necessary.
And even if the
book doesn't like it, that even works while being launched
into thermals or
Mistral rotors.

--
Bert Willing

ASW20 'TW'


'Ian Johnston' a écrit dans le message de news:
dzZo7CxomoOm-pn2-DhT3lGVC8vpw@localhost...
On Tue, 5 Jul 2005 10:27:40 UTC, 'Bert Willing'
wrote:

I take of with my ASW20 on a black link. And it's
not the winch driver
who
decides about this.

If that is the correct link for the glider, then fine.
If it's not,
and I were either launch marshall or winch driver,
then I can assure
you that I, personally, would have nothing to do with
launching you.

The correct weak link for an ASH-25, as specified
by the designer and
manufacturer, is brown, 850dN.

Ian


--




Mark J. Boyd

On Tue, 5 Jul 2005 15:59:24 UTC, M B
wrote:

Is there any commonly known way to test a weak
link non-destructively (other than launching a glider)?

The Tost system uses two in parallel, one slightly longer than the
other. Whoever hooks up the glider should always check that both links
are intact and that only one is taking the load.

Ian

--

Ian Johnston wrote:

On Tue, 5 Jul 2005 15:59:24 UTC, M B
wrote:

Is there any commonly known way to test a weak
link non-destructively (other than launching a glider)?

The Tost system uses two in parallel, one slightly longer than the
other. Whoever hooks up the glider should always check that both links
are intact and that only one is taking the load.

Ian

--
We've gone to using a single TOST weak link. Over the years, the metal
sleeve gets dented, making inspection suspect without a time consuming
disassembly. A few times the links part without any warning that perhaps
the first may have failed previously. We have also had both fail at the
same time when going through a sharp wind gradient. We replaced both and
broke both on the very next launch through this sharp gradient. At the
price of the weak links, consuming one at a time, rather than two, just
makes more sense.

NDT would work if you jigged up an accurate test bed. I would be more
concerned with rope weak links used in aerotowing than TOST weak links if I
wanted to test something. From many years of observation I'm pretty
confident that the TOST links perform as expected.

Frank

On Tue, 5 Jul 2005 16:57:36 UTC, "F.L. Whiteley"
wrote:

NDT would work if you jigged up an accurate test bed. I would be more
concerned with rope weak links used in aerotowing than TOST weak links if I
wanted to test something. From many years of observation I'm pretty
confident that the TOST links perform as expected.

Me too. Tost aerotow weak links are pretty good as well - I thought
just about everyone had gone over to them in place of rope. Mind you,
I knew one club which put a good stout length of rope in parallel with
the Tost link "because they are so expensive if they break and we lose
half the connector."

Ho hum.

Ian


--

Ian Johnston wrote:

On Tue, 5 Jul 2005 16:57:36 UTC, "F.L. Whiteley"
wrote:

NDT would work if you jigged up an accurate test bed. I would be more
concerned with rope weak links used in aerotowing than TOST weak links if
I
wanted to test something. From many years of observation I'm pretty
confident that the TOST links perform as expected.

Me too. Tost aerotow weak links are pretty good as well - I thought
just about everyone had gone over to them in place of rope. Mind you,
I knew one club which put a good stout length of rope in parallel with
the Tost link "because they are so expensive if they break and we lose
half the connector."

Ho hum.

Ian


--
I don't recall having seen a TOST aerotow weak link in use in the US.
Perhaps some are using them.

Frank

"Ian Johnston" wrote in message
news:dzZo7CxomoOm-pn2-1IU6gvmrdIOd@localhost...
On Tue, 5 Jul 2005 15:59:24 UTC, M B
wrote:

Is there any commonly known way to test a weak
link non-destructively (other than launching a glider)?

The Tost system uses two in parallel, one slightly longer than the
other. Whoever hooks up the glider should always check that both links
are intact and that only one is taking the load.

Ian

To expand on what Ian wrote, the parallel weak-link system places only the
primary weak-link under load with a unloaded spare in place to take the load
should the first one fail below its rated strength as a result of fatigue
from repeated load cycles. If the failure is due to an overload, the spare
will fail a millisecond after the primary and the glider will be protected
from excessive cable force.

If the person hooking up the glider to the winch line shows these weak links
to the pilot, a crack in the primary will be obvious and can be quickly
replaced with a new one of the correct strength for the glider.

The Tost weak-link system is very well thought out and correct weak-link
color is universally referenced in German glider handbooks. It should be
used in every winch operation. I find it very comforting to know that the
glider will be protected from excessive loads while the weak-link itself is
backed up by a full strength spare.

Using either over or understrength weak-links is very hazardous.

Bill Daniels

On Tue, 5 Jul 2005 18:05:20 UTC, "Bill Daniels"
wrote:

If the person hooking up the glider to the winch line shows these weak links
to the pilot, a crack in the primary will be obvious and can be quickly
replaced with a new one of the correct strength for the glider.

It's also easy to check that under light tension one link is taking
the load and one is free to rattle around, which is an easy way to
make sure that the primary link hasn't stretched, or got elongated
holes. The downside is that the metal holder for the links does tend
to get rammed full of mud on grass airfields.

Ian


--

TOST WEAK LINKS.

The BGA now recommend as follows:

"The weak-link assembly incorporates a link to suit the glider being
launched (see Appendix E) and this remains with the parachute assembly.
(At some sites, a selection of weak-links, suitable for launching each of
the glider types in the club’s fleet, may remain permanently attached to the
parachute assembly. This is convenient, but calls for extra care in
ensuring that the correct link is chosen for each launch.)

"N.B. The Tost weak-link system is designed for use either with a single
link or with double links. If the double-link system is employed, it is
essential that the links are of different design (the main link having round
holes and the reserve link having slotted holes). Using two weak links,
each of the same design doubles the breaking load and renders the whole
assembly ineffective. Because of the risk of assembling two weak links
incorrectly, the single-link assembly is recommended as the more foolproof
system."

This is a quote from the BGA Winch Operators Manual , page 20,
http://www.gliding.co.uk/forms/clubm...t/winchops.pdf .

This recommendation was made after an Olympia 463 had structural failure
while being winch launched, and the pilot was killed. It was found that
there was weakness in the wings due to water ingress while in the trailer,
and a double strength weak link had been used; it was not established which
was the critical factor.

This accident was on 13th July 1996, BGA Ref: 79/96, AAIB Ref: EW/C96/7/5.

W.J. (Bill) Dean (U.K.)
Remove "ic" to reply.


"Ian Johnston" wrote in message
news:dzZo7CxomoOm-pn2-1IU6gvmrdIOd@localhost...

On Tue, 5 Jul 2005 15:59:24 UTC, M B
wrote:

Is there any commonly known way to test a weak
link non-destructively (other than launching a glider)?

The Tost system uses two in parallel, one slightly longer than the
other. Whoever hooks up the glider should always check that both links
are intact and that only one is taking the load.

Ian