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.