Originally Posted by
flybymike
I know nothing whatsoever about gliding so can someone who does please explain to me the issues surrounding winch launches.
One sees cable warning information given on CAA half mil charts at varying heights up to and in excess of 3000 feet. Are there really many gliding sites with 1000 metre runways and 1000 metre cables? and at what point on the winch launch would the cable be released? Surely there must come a point during the launch (45 degrees?) where the cable begins to drag the glider back down towards the ground rather than up in the air, in which case a cable release at say 45 degrees would cut the height risk down to say only 1500 feet rather than 3000 feet? or am I being thick about this?
The best way to understand the dangers of flying into a winch cable is to visit a winch site and watch some launching. Considering that the MTOW of a K21 (twin-seat trainer) is 600kg and our winch will accelerate that to lift-off (approx 40 knots) in less than 5 seconds that should put the amount of energy into context.
TO put it another way, the cable speed is 60 knots or so, it's 1/2" circumference (approx) steel rope and makes a very effective saw. We accidentally tried ours out a low speed on the launch caravan and it cut straight through a cast aluminimum handle. I'm sure it will be equally effective on a Cessna or similar.
The heights given on the CAA charts are like all other information - the best / worst possible case (have you looked at how high it suggests Ben Nevis is?), depending on if you are in the glider or the other craft. Our site is cleared to launch to 2,000' and occasionally we manage it. On other days we barely get above 1,000', but using the information on the charts will make sure you are well clear of any cable-related activity.