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On Tuesday, December 20, 2016 at 3:00:06 PM UTC-7, Don Johnstone wrote:
At 23:33 16 December 2006, Derek Copeland wrote: I thought that was exactly the point I was trying to make! Stick position is type dependent. Where you hold the stick and how much you have to pull back, or push forward, may be different to what you are used to, if you fly a different type of glider. It depends on the hook position, the exact c of g and centre of pressure, and the trim position. The advice I gave was to hold the stick in a position that gives the optimum angle of climb for your type of winch. Full stop, period! Real life winch launching takes place using different types of gliders in differing wind strengths. No one throttle setting can cover all cases. If you launched a slow glider (e.g. a K8) into a 45 knot headwind, you could stop the winch altogether once it has got airborne and allow it to launch like a kite. The wind would be providing the energy while the winch would just act as an anchor point on the ground. Conversely launching a heavy two seater on a still day with a moderately powerful winch might require absolutely full throttle. Derek Copeland Yep, what he said. If you take a winch launch with a really skilled winch driver you will experience a constant speed all the way up the launch. How is that done? There are a combination of things that can give clues to the winch driver, the bow in the cable, if it is wire, does not work so well with dynema/sky rope. Marked throttle settings as on a Skylaunch winch can help but it really is a matter of feel and experience. For most glass gliders 55-65kts seems to work best. I always reduce power at the top, back to idle once the glider gets near to the max angle, instigating a back release, this avoids the possibility of a loop if the cable is released under tension. It is absolutely essential to ensure that the power is cut, before the glider is vertically over the winch in nil/very low headwind conditions, it is very unpleasant to have 1000ftl of cable drop on top of the winch, it it can take a bit of time to get it off as well. If you know how to fly you can have exactly the airspeed you want all the way up the launch. The winch does not and, in fact, cannot control glider airspeed. The pilot is the only one who can do that. The winch merely controls power (think thrust). It works exactly as with airplanes, pitch controls airspeed and power (thrust) controls rate of climb. The pilot merely adjusts pitch attitude as necessary to maintain the desired airspeed. Reduce winch power and the rate of climb (angle) decreases but the airspeed is unchanged. Reduce it all the way to zero and the glider is left in a glide at the desired airspeed. Increase power and the rate of climb (angle) increases but the airspeed stays the same. Increase it too much and the weak link breaks - at exactly the desired airspeed - or the glider runs out of up elevator and the pilot must then ask for less power. It's really very simple. |
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