RVDT
your are right and exact in the most points, but
Never use a line that will stretch - many before you have tried. Most of them aren't around to tell you anymore. If you are using a line constantly under hard conditions it will wear. I prefer wire crane cable (as opposed to wire rope) or chain.
Your are out of the last century to use an undamped steel system! It's correct to avoid systems with high stretching factor, but no stretching (steel)) means no damping and this could be dangerous due to load peaks and undamped kind of inputs, flutters and oscillations to the line, hook(s), loads and helicopters. If you use a steel line and the line breaks inform your life insurance. High risk situation to find your resiled steel line around the M/R. As an experienced longliner you will know that load peaks much higher than the load weight (know the difference between weight and force
) allways appear. The need of a damping part is important.
You were friendly enough to mention Switzerland, but here and in all the other Alps "longline countries" we have much more modern and safer systems.
DYNEEMA and other fibre lines determine the standards. And the weight! of the line is much lower. Compared the 50m long and 16mm diameter steel line counts 50kg, in the same length the DYNEEMA rope 24mm diameter with much higher breaking loads in force peaks is only 10kg. Both for around 25kN steady workload
Means modern fibres are 5 times lighter than steel, elegant in flight - slowly in swing, no elongation ( < 2%), and with a damping factor. No breaks or damages on sharp edges.
And important: One-man-handling on the ground! Seems to me if you use "longline steel chains"
your ground staff have to be all bodybuilders?
@headshed and collegues
Around longline, mountain flying and so on it's easy to find more than enough threads (means thousends of inputs) on PPRUNE search. Use your brain and search, not 3 minutes typing a question and wait to be feeded.