So why do we say “You have a weak link”? Well, actually, we don’t. What we say is “you have a [colour] link. But let’s start at the beginning. First, the cable isn’t JUST a cable it’s a cable, originally 4 or 6mm steel stranded, now more likely Dynema – a kind of super strong impregnated rope. Very light in weight and worth about an extra 300ft on the launch height (or about an extra minute and a half flying time to find your first thermal.
Next, attached to the glider end of the cable is a small drogue parachute and a shock rope. The ‘chute has a slatted design so it doesn’t deploy whilst the launch is in progress but does deploy when the cable is released at the top of the launch. It keeps some tension on the cable whilst the winch driver pulls it back to the winch and helps prevent “throwing loops” off the main drum onto the drive shaft.
Finally after the ‘chute comes the weak link. About two metres of stranded steel inside a coloured sheath, a special shackle arrangement and an in-line, special piece of metal, computer tested to a predetermined breaking strength, which is designed to protect the glider and the pilot from both environmental catastrophes and the pilot’s own stupidity. Each glider manufacturer specifies the type of weak link that should be used and the person attaching the cable to the glider will confirm to the pilot what colour weak link is attached. Unfortunately, there is insufficient data held in the .ACF file for X-Winch to determine the correct weak link to use. So until Laminar Research provide that data – or at least give the aircraft developers a slot in PlaneMaker for that data to be recorded, the X-Winch script saying “You have a weak link” is a compromise.
To find out more about Weak Links visit The TOST Website “Max Winch” (speed) and a “Max Aerotow” (speed) would be good numbers to have included in a future release of PlaneMaker since these numbers are on the cockpit placard of every glider ever produced. They are the result of strict testing and certification by EASA (in Europe) JAR in other countries. Again, the X-Winch target speed is 60 which is another compromise.