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#11
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How to get maximum height on a winch launch?
Derek Copeland wrote: The exact position to hold the stick during a winch launch is very type dependent. Gliders with way back c of g hooks, such as the K21, K8 and Pirat will require the stick to be held neutral or even forward of neutral during the full climb. My Pirat will fly a very nice winch launch which is almost completely independent of anything the pilot chooses to do with the stick! It's not so much the fore-and-aft position of the hook, I think, as the vertical one: since it is at the bottom of a deep fuselage there is a considerable nose up pitching moment during the ground run. As soon as it takes off, therefore, it does a lovely rotation into full climb all by itself: full forward stick has no effect at all. Gliders with single 'compromise' hooks such as the Slingsby Skylark and the Bocian will need the stick to be held on the back stop if they are to climb at all steeply. All the Bocians I have ever flown had C of G and nose hooks. The Pirat manual specifically permits winching on the nose hook: using full back stick and forward trim from the "All Out", and warning that it will only give 60% of normal release height. I have never tried this, for several reasons, one being that I rather like having the back release there ... Ian |
#12
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How to get maximum height on a winch launch?
Dan G wrote: With a K21, which winch drivers here (which includes me) are told to give "full power all the way up" from our Oldsmobile V8. Then with all due respect, I think your club needs to think about its training policy for winch drivers. "Give full power all the way up" is a recipe for disaster - it should be "Give enough power all the way up, and don't assume that means full throttle". A good winch driver knows how much welly to give it by the bow in the cable, the speed of the drums and the appearance of the glider. Whacking in full throttle without a care is as bad as giving full back stick from the start of the launch. If your club is training winch drivers to think about throttle position without considering effects and training pilots to think about stick position without considering effects, it may have to do some fundamental thinking about flying and training. In both cases the principle should be "Know what effect you want and use the right amount of control to achieve it, monitoring the situation and varying inputs as required." I would be very cautious about an organisation which taught crude open-loop control in two separate safety-critical areas. Please don't take this personally, because it's not so intended. Ian |
#13
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How to get maximum height on a winch launch?
Ian,
winch launching my Calif over 8 years on a 280 hp winch was exactly "full power until release", and that was the only way to go. So, in some cases this type of instructions actually does work. Bert "Ian" wrote in message ps.com... Dan G wrote: With a K21, which winch drivers here (which includes me) are told to give "full power all the way up" from our Oldsmobile V8. Then with all due respect, I think your club needs to think about its training policy for winch drivers. "Give full power all the way up" is a recipe for disaster - it should be "Give enough power all the way up, and don't assume that means full throttle". A good winch driver knows how much welly to give it by the bow in the cable, the speed of the drums and the appearance of the glider. Whacking in full throttle without a care is as bad as giving full back stick from the start of the launch. If your club is training winch drivers to think about throttle position without considering effects and training pilots to think about stick position without considering effects, it may have to do some fundamental thinking about flying and training. In both cases the principle should be "Know what effect you want and use the right amount of control to achieve it, monitoring the situation and varying inputs as required." I would be very cautious about an organisation which taught crude open-loop control in two separate safety-critical areas. Please don't take this personally, because it's not so intended. Ian |
#14
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How to get maximum height on a winch launch?
"Bert Willing" wrote in message ... Ian, winch launching my Calif over 8 years on a 280 hp winch was exactly "full power until release", and that was the only way to go. So, in some cases this type of instructions actually does work. Bert Full power for the whole launch works when the winch is severely underpowered. As more powerful winches are introduced, you will find there are points in the launch where the driver must reduce power to maintain constant tension. Bill Daniels |
#15
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How to get maximum height on a winch launch?
Should say that it's "full power all the way up" the main climb, of
course we back off at the top. But there was some suprise at the launch point recently when a K21 waved off... the common thought was "K21s should be able to handle it". Maybe it could if it was no wind, but with a good headwind they just can't. So far the sole answer to my original question has been "look at the wingtips during the launch and find what stick position will hold them at about 45 degrees to the horizon AND give a safe speed. If you have a low powered winch you may have to adopt a lesser angle" from Derek. Does everyone agree with this? Dan |
#16
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How to get maximum height on a winch launch?
Dan G wrote: Should say that it's "full power all the way up" the main climb, of course we back off at the top. But there was some suprise at the launch point recently when a K21 waved off... the common thought was "K21s should be able to handle it". Maybe it could if it was no wind, but with a good headwind they just can't. Headwind makes a big difference. Our underpowered winch can overspeed the twins easily if the wind gets above about 15knots. If indicated airspeed is above 60knots, you're getting diminishing returns from the launch. Frank Whiteley |
#17
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How to get maximum height on a winch launch?
Ian wrote:
Martin Gregorie wrote: Dan G wrote: and for K21s winch drivers are briefed to give full throttle the whole way up (winch is c.300bhp). That sounds excessive to me. The only glider that gets full power all the way is an ASH-25. It shouldn't, since an ASH-25 is a brown weak link, not a black one. Many clubs, pilots and winch drivers ignore this, but at their peril. When I am driving I will refuse to launch an ASH-25 unless someone I trust will confirm to me that it has the right link in place. 60:1 does not bring immortality. Fair comment - I've never been in the winch or at that end when one was launched, but it certainly seemed to need a lot of grunt to get it moving and rotated into full climb. -- martin@ | Martin Gregorie gregorie. | Essex, UK org | |
#18
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How to get maximum height on a winch launch?
Martin Gregorie wrote: Ian wrote: It shouldn't, since an ASH-25 is a brown weak link, not a black one. Many clubs, pilots and winch drivers ignore this, but at their peril. When I am driving I will refuse to launch an ASH-25 unless someone I trust will confirm to me that it has the right link in place. 60:1 does not bring immortality. Fair comment - I've never been in the winch or at that end when one was launched, but it certainly seemed to need a lot of grunt to get it moving and rotated into full climb. Thanks. Yes, they are heavy (about 1600lbs max AUW, iirc) but the designers have specified a brown link and I respect that. It's not as if the damn things need to get high anyway! Ian |
#19
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How to get maximum height on a winch launch?
Bill Daniels wrote: Full power for the whole launch works when the winch is severely underpowered. As more powerful winches are introduced, you will find there are points in the launch where the driver must reduce power to maintain constant tension. It's the inflexibility of "full power all the way" which worries me. I've lobbed K21's off at Sutton Bank on windless days which needed full throttle, windy days on which a whisker over idle was quite enough and days when things changed from calm to windy half way up the launch. A driver who thinks "K21 - right, full power" is ... I was going to right "get himself into trouble oneday" but that isn't quite right. He's going to get two other people into trouble one day. Ian |
#20
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How to get maximum height on a winch launch?
Dan G wrote: Should say that it's "full power all the way up" the main climb, of course we back off at the top. But there was some suprise at the launch point recently when a K21 waved off... the common thought was "K21s should be able to handle it". Maybe it could if it was no wind, but with a good headwind they just can't. And that was a surprise? Find yourself another club, man, because if headwinds on a winch launch are unexpected your current lot are going to damage someone one day. So far the sole answer to my original question has been "look at the wingtips during the launch and find what stick position will hold them at about 45 degrees to the horizon AND give a safe speed. If you have a low powered winch you may have to adopt a lesser angle" from Derek. Does everyone agree with this? No. I think it's bad advice. Yes, you should aim to have a proper climb angle and air speed, but the stick position is irrelevant. Just use enough to do what's needed. How many inches of rudder movement would you use to balance a 20 degree per second roll into a turn? Or would you just aim to us enough to keep the string straight? Ian |
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