What is a stationary winch?.
It is a powered winch that stays in one spot and which pulls line in under tension. All of the line on the winch is pulled out, then the far end of the rope is attached to the glider. On a signal, the winch pulls the line back in to make the glider climb. When the glider arrives over the winch, the pilot releases the towline. The tow tension is a function of the throttle setting of the engine powering it.
