If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
How to get maximum height on a winch launch?
I'm interested in learning how to get the maximum possible height on a
winch launch, without compromising safety in any way. This question has two parts really - how should the pilot fly the launch (pretty much how should he operate the elevator during the launch), how fast should the glider fly, and how should the winch driver feed the power in? For the sake of argument, let's assume the glider is a K13. For reference, I fly from an airfield with a 3,300' long cable, and the maximum height I achieve repeatedly is 1,700'. Headwind typically goes from around 10kts at the ground to something like (I estimate) 20kts at height. |
#2
|
|||
|
|||
How to get maximum height on a winch launch?
1) Listen to your instructor.
2) Do nothing different, you are already acheiving beyond average heights, changing your current habits is maybe looking for a problem. If I could get 1700 feet on 3300 feet of cable I would change absolutely nothing. Look no further. Bob Dan G wrote: I'm interested in learning how to get the maximum possible height on a winch launch, without compromising safety in any way. This question has two parts really - how should the pilot fly the launch (pretty much how should he operate the elevator during the launch), how fast should the glider fly, and how should the winch driver feed the power in? For the sake of argument, let's assume the glider is a K13. For reference, I fly from an airfield with a 3,300' long cable, and the maximum height I achieve repeatedly is 1,700'. Headwind typically goes from around 10kts at the ground to something like (I estimate) 20kts at height. |
#3
|
|||
|
|||
How to get maximum height on a winch launch?
If you join the Yahoo group "winchdesign" and look in the files section,
there are a series of truely excellent papers in the folder "Winch Dynamics and Performance" by George Moore. (soargsm) Essentially what George determened is that the major sensitivities a 1.Field length 2. Headwind 3. Cable tension as a percentage of glider flying weight. 4. Weight & drag of the cable There is very little extra height to be gained by agressive technique beyond just hitting your target airspeed and holding it there with smooth control inputs. This gives an angle of attack just slightly greater than that for best L/D. If you want help with this, put some AOA strings on the canopy sides and calibrate them for L/D max and Vmin sink. Of course, it goes without saying that you should never put yourself in danger by rotating into the climb so quickly that a recovery from a rope break is impossible. Smooth and accurate flying are what you want. So, if you want to get higher, get a longer field with more wind, replace steel with high strength Dyneema and get a winch that can accurately hold tension at 80 - 90% of the weak link. Bill Daniels "Dan G" wrote in message ups.com... I'm interested in learning how to get the maximum possible height on a winch launch, without compromising safety in any way. This question has two parts really - how should the pilot fly the launch (pretty much how should he operate the elevator during the launch), how fast should the glider fly, and how should the winch driver feed the power in? For the sake of argument, let's assume the glider is a K13. For reference, I fly from an airfield with a 3,300' long cable, and the maximum height I achieve repeatedly is 1,700'. Headwind typically goes from around 10kts at the ground to something like (I estimate) 20kts at height. |
#4
|
|||
|
|||
How to get maximum height on a winch launch?
Thanks Bill, that document is very interesting.
There is one thing in particular I am unsure about however - how much up elevator I should be putting in. With the K8, I fly the launch at 50-55kts with the stick fully back for perhaps the last 30% of the launch after smoothly transitioning from full forwards on the ground run through neutral once in the full climb, until I feel the glider being pulled level, when I relax the aft pressure in anticipation of putting the nose down to reuce cable tension prior to releasing. (This later movement often results in quite an increase in speed, which I convert to height after releasing. Is this an indication I'm releasing back pressure too early, or the winch driver not backing off the throttle enough?) With a K21, which winch drivers here (which includes me) are told to give "full power all the way up" from our Oldsmobile V8. Climb speed is at lesst 65kts and I'm reluctant to pull back too hard. Why? A K21 launches on a black weak link (1,000kg). I imagine full up elevator in a K21 would produce enough lift to break that at well below max winch speed, 81kts. Is there a way to calculate how much lifting force full up elevator should produce for any given airspeed? Or should I not be putting full up in? If not, just how far should I bring the stick back, and when? Bill Daniels wrote: If you join the Yahoo group "winchdesign" and look in the files section, there are a series of truely excellent papers in the folder "Winch Dynamics and Performance" by George Moore. (soargsm) Essentially what George determened is that the major sensitivities a 1.Field length 2. Headwind 3. Cable tension as a percentage of glider flying weight. 4. Weight & drag of the cable There is very little extra height to be gained by agressive technique beyond just hitting your target airspeed and holding it there with smooth control inputs. This gives an angle of attack just slightly greater than that for best L/D. If you want help with this, put some AOA strings on the canopy sides and calibrate them for L/D max and Vmin sink. Of course, it goes without saying that you should never put yourself in danger by rotating into the climb so quickly that a recovery from a rope break is impossible. Smooth and accurate flying are what you want. So, if you want to get higher, get a longer field with more wind, replace steel with high strength Dyneema and get a winch that can accurately hold tension at 80 - 90% of the weak link. Bill Daniels "Dan G" wrote in message ups.com... I'm interested in learning how to get the maximum possible height on a winch launch, without compromising safety in any way. This question has two parts really - how should the pilot fly the launch (pretty much how should he operate the elevator during the launch), how fast should the glider fly, and how should the winch driver feed the power in? For the sake of argument, let's assume the glider is a K13. For reference, I fly from an airfield with a 3,300' long cable, and the maximum height I achieve repeatedly is 1,700'. Headwind typically goes from around 10kts at the ground to something like (I estimate) 20kts at height. |
#5
|
|||
|
|||
How to get maximum height on a winch launch?
Dan, your questions concern me. Full up elevator is dangerous on a winch
launch. All modern trainers like ASK 21's or Grob 103's will fly an almost perfect launch without the pilot touching the controls if trim and winch power are right. Demonstrating hands off launches is a good start to winch training. (The take home lession is the launch will be nearly perfect if the pilot doesn't screw it up.) You should be using just enough elevator to keep the airspeed where you want it. (Typically 55 - 60 knots, depending on the glider) The basic principle is that the winch driver controlls power and the glider pilot controlls airspeed. If it requires large amounts of up elevator to control airspeed, signal for less power. As you point out, some gliders with high CG locations like a K8 will need nearly full down elevator from the start to control the natural pitch up. It shouldn't need much up elevator at all later. The winch driver should be slowly backing off the power as the glider approaches the top of the launch. Take a good look at George Moores charts that show cable tension - tension is a direct function of winch power. In any event, there's very little additional height that can be achieved late in the launch. Pulling hard near the top just loads up the glider and may break the weak link. (You are using the correct Tost weak links, right?) Suggestion: Get a copy of a good glider flight simulator like Condor and practice lauches on a computer. There's a lot to learn with a good sim. I use Condor as an "animated white board" when I teach winch ground school. Bill Daniels "Dan G" wrote in message oups.com... Thanks Bill, that document is very interesting. There is one thing in particular I am unsure about however - how much up elevator I should be putting in. With the K8, I fly the launch at 50-55kts with the stick fully back for perhaps the last 30% of the launch after smoothly transitioning from full forwards on the ground run through neutral once in the full climb, until I feel the glider being pulled level, when I relax the aft pressure in anticipation of putting the nose down to reuce cable tension prior to releasing. (This later movement often results in quite an increase in speed, which I convert to height after releasing. Is this an indication I'm releasing back pressure too early, or the winch driver not backing off the throttle enough?) With a K21, which winch drivers here (which includes me) are told to give "full power all the way up" from our Oldsmobile V8. Climb speed is at lesst 65kts and I'm reluctant to pull back too hard. Why? A K21 launches on a black weak link (1,000kg). I imagine full up elevator in a K21 would produce enough lift to break that at well below max winch speed, 81kts. Is there a way to calculate how much lifting force full up elevator should produce for any given airspeed? Or should I not be putting full up in? If not, just how far should I bring the stick back, and when? Bill Daniels wrote: If you join the Yahoo group "winchdesign" and look in the files section, there are a series of truely excellent papers in the folder "Winch Dynamics and Performance" by George Moore. (soargsm) Essentially what George determened is that the major sensitivities a 1.Field length 2. Headwind 3. Cable tension as a percentage of glider flying weight. 4. Weight & drag of the cable There is very little extra height to be gained by agressive technique beyond just hitting your target airspeed and holding it there with smooth control inputs. This gives an angle of attack just slightly greater than that for best L/D. If you want help with this, put some AOA strings on the canopy sides and calibrate them for L/D max and Vmin sink. Of course, it goes without saying that you should never put yourself in danger by rotating into the climb so quickly that a recovery from a rope break is impossible. Smooth and accurate flying are what you want. So, if you want to get higher, get a longer field with more wind, replace steel with high strength Dyneema and get a winch that can accurately hold tension at 80 - 90% of the weak link. Bill Daniels "Dan G" wrote in message ups.com... I'm interested in learning how to get the maximum possible height on a winch launch, without compromising safety in any way. This question has two parts really - how should the pilot fly the launch (pretty much how should he operate the elevator during the launch), how fast should the glider fly, and how should the winch driver feed the power in? For the sake of argument, let's assume the glider is a K13. For reference, I fly from an airfield with a 3,300' long cable, and the maximum height I achieve repeatedly is 1,700'. Headwind typically goes from around 10kts at the ground to something like (I estimate) 20kts at height. |
#6
|
|||
|
|||
How to get maximum height on a winch launch?
Bill Daniels wrote:
Dan, your questions concern me. Full up elevator is dangerous on a winch launch. All modern trainers like ASK 21's or Grob 103's will fly an almost perfect launch without the pilot touching the controls if trim and winch power are right. You should be using just enough elevator to keep the airspeed where you want it. (Typically 55 - 60 knots, depending on the glider) The basic principle is that the winch driver controlls power and the glider pilot controlls airspeed. If it requires large amounts of up elevator to control airspeed, signal for less power. As you point out, some gliders with high CG locations like a K8 will need nearly full down elevator from the start to control the natural pitch up. It shouldn't need much up elevator at all later. The winch driver should be slowly backing off the power as the glider approaches the top of the launch. Take a good look at George Moores charts that show cable tension - tension is a direct function of winch power. In any event, there's very little additional height that can be achieved late in the launch. Pulling hard near the top just loads up the glider and may break the weak link. (You are using the correct Tost weak links, right?) We set the trim well forwards to give approach speed in the event of a launch failure (I am not going to stop doing that, but hypothetically where would you put the trim for best launch height?), and for K21s winch drivers are briefed to give full throttle the whole way up (winch is c.300bhp). I've also heard several pilots be admonished by instructors recently for "not pulling back" after somewhat low launches. Surely pulling back increases the lift the aircraft is producing, and therefore gives more height? If the airspeed is well below placard max winch speed, I would have thought it would not result in enough force to break the link. BTW we do, without fail, use the correct weak links (and not doubled-up or anything stupid either). That said, we do break weak links with some regularity. Suggestion: Get a copy of a good glider flight simulator like Condor and practice lauches on a computer. There's a lot to learn with a good sim. I use Condor as an "animated white board" when I teach winch ground school. Heh, I have Condor but find it much harder to fly than "real life", probably as my comp is rather weedy so it's a bit jerky. Thanks for the suggestion though! Dan Bill Daniels "Dan G" wrote in message oups.com... Thanks Bill, that document is very interesting. There is one thing in particular I am unsure about however - how much up elevator I should be putting in. With the K8, I fly the launch at 50-55kts with the stick fully back for perhaps the last 30% of the launch after smoothly transitioning from full forwards on the ground run through neutral once in the full climb, until I feel the glider being pulled level, when I relax the aft pressure in anticipation of putting the nose down to reuce cable tension prior to releasing. (This later movement often results in quite an increase in speed, which I convert to height after releasing. Is this an indication I'm releasing back pressure too early, or the winch driver not backing off the throttle enough?) With a K21, which winch drivers here (which includes me) are told to give "full power all the way up" from our Oldsmobile V8. Climb speed is at lesst 65kts and I'm reluctant to pull back too hard. Why? A K21 launches on a black weak link (1,000kg). I imagine full up elevator in a K21 would produce enough lift to break that at well below max winch speed, 81kts. Is there a way to calculate how much lifting force full up elevator should produce for any given airspeed? Or should I not be putting full up in? If not, just how far should I bring the stick back, and when? Bill Daniels wrote: If you join the Yahoo group "winchdesign" and look in the files section, there are a series of truely excellent papers in the folder "Winch Dynamics and Performance" by George Moore. (soargsm) Essentially what George determened is that the major sensitivities a 1.Field length 2. Headwind 3. Cable tension as a percentage of glider flying weight. 4. Weight & drag of the cable There is very little extra height to be gained by agressive technique beyond just hitting your target airspeed and holding it there with smooth control inputs. This gives an angle of attack just slightly greater than that for best L/D. If you want help with this, put some AOA strings on the canopy sides and calibrate them for L/D max and Vmin sink. Of course, it goes without saying that you should never put yourself in danger by rotating into the climb so quickly that a recovery from a rope break is impossible. Smooth and accurate flying are what you want. So, if you want to get higher, get a longer field with more wind, replace steel with high strength Dyneema and get a winch that can accurately hold tension at 80 - 90% of the weak link. Bill Daniels "Dan G" wrote in message ups.com... I'm interested in learning how to get the maximum possible height on a winch launch, without compromising safety in any way. This question has two parts really - how should the pilot fly the launch (pretty much how should he operate the elevator during the launch), how fast should the glider fly, and how should the winch driver feed the power in? For the sake of argument, let's assume the glider is a K13. For reference, I fly from an airfield with a 3,300' long cable, and the maximum height I achieve repeatedly is 1,700'. Headwind typically goes from around 10kts at the ground to something like (I estimate) 20kts at height. |
#7
|
|||
|
|||
How to get maximum height on a winch launch?
Responses interspersed.
"Dan G" wrote in message oups.com... We set the trim well forwards to give approach speed in the event of a launch failure (I am not going to stop doing that, but hypothetically where would you put the trim for best launch height?), and for K21s winch drivers are briefed to give full throttle the whole way up (winch is c.300bhp). Same as always. Set the trim for zero stick force. It has no effect whatever on release height. I've also heard several pilots be admonished by instructors recently for "not pulling back" after somewhat low launches. Surely pulling back increases the lift the aircraft is producing, and therefore gives more height? If the airspeed is well below placard max winch speed, I would have thought it would not result in enough force to break the link. I sounds like your winch may reach redline RPM just as the glider rotates into the climb. If the pilot doesn't rotate quickly enough, the winch driver will have to throttle down to save the engine. Pilots trained on aero tow will often resist pitching up into the climb and need to be admonished that this is not an aero tow and they need to climb. As they climb the engine RPM will diminish. I'm not saying pull hard, just pitch up smoothly to control airspeed. The very best height is achieved by flying the glider at just over the best L/D angle of attack. Pulling up harder and flying at a greater AOA will actually reduce height achieved. To repeat, fly the selected airspeed. You may improve things slightly by using an AOA indicator. Strings work fine. BTW we do, without fail, use the correct weak links (and not doubled-up or anything stupid either). That said, we do break weak links with some regularity. Whew! Thanks for that. Suggestion: Get a copy of a good glider flight simulator like Condor and practice lauches on a computer. There's a lot to learn with a good sim. I use Condor as an "animated white board" when I teach winch ground school. Heh, I have Condor but find it much harder to fly than "real life", probably as my comp is rather weedy so it's a bit jerky. Thanks for the suggestion though! It is harder than real life - but it's good training. Bill Daniels |
#8
|
|||
|
|||
How to get maximum height on a winch launch?
Hi Bill, Glad to see you are coming round to my way
of thinking, that the rotation into the full climb should be gentle and controlled, and should not put you in an unrecoverable position if the launch fails for any reason. 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. Gliders with slightly further forward hooks such as the K13 will need the stick held fairly well back, although probably not on the back stop. 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. The best advice I can give to Dan G is to 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. Derek Copeland At 15:18 13 December 2006, Bill Daniels wrote: Dan, your questions concern me. Full up elevator is dangerous on a winch launch. All modern At 15:18 13 December 2006, Bill Daniels wrote: Dan, your questions concern me. Full up elevator is dangerous on a winch launch. All modern trainers like ASK 21's or Grob 103's will fly an almost perfect launch without the pilot touching the controls if trim and winch power are right. Demonstrating hands off launches is a good start to winch training. (The take home lession is the launch will be nearly perfect if the pilot doesn't screw it up.) You should be using just enough elevator to keep the airspeed where you want it. (Typically 55 - 60 knots, depending on the glider) The basic principle is that the winch driver controlls power and the glider pilot controlls airspeed. If it requires large amounts of up elevator to control airspeed, signal for less power. As you point out, some gliders with high CG locations like a K8 will need nearly full down elevator from the start to control the natural pitch up. It shouldn't need much up elevator at all later. The winch driver should be slowly backing off the power as the glider approaches the top of the launch. Take a good look at George Moores charts that show cable tension - tension is a direct function of winch power. In any event, there's very little additional height that can be achieved late in the launch. Pulling hard near the top just loads up the glider and may break the weak link. (You are using the correct Tost weak links, right?) Suggestion: Get a copy of a good glider flight simulator like Condor and practice lauches on a computer. There's a lot to learn with a good sim. I use Condor as an 'animated white board' when I teach winch ground school. Bill Daniels 'Dan G' wrote in message roups.com... Thanks Bill, that document is very interesting. There is one thing in particular I am unsure about however - how much up elevator I should be putting in. With the K8, I fly the launch at 50-55kts with the stick fully back for perhaps the last 30% of the launch after smoothly transitioning from full forwards on the ground run through neutral once in the full climb, until I feel the glider being pulled level, when I relax the aft pressure in anticipation of putting the nose down to reuce cable tension prior to releasing. (This later movement often results in quite an increase in speed, which I convert to height after releasing. Is this an indication I'm releasing back pressure too early, or the winch driver not backing off the throttle enough?) With a K21, which winch drivers here (which includes me) are told to give 'full power all the way up' from our Oldsmobile V8. Climb speed is at lesst 65kts and I'm reluctant to pull back too hard. Why? A K21 launches on a black weak link (1,000kg). I imagine full up elevator in a K21 would produce enough lift to break that at well below max winch speed, 81kts. Is there a way to calculate how much lifting force full up elevator should produce for any given airspeed? Or should I not be putting full up in? If not, just how far should I bring the stick back, and when? Bill Daniels wrote: If you join the Yahoo group 'winchdesign' and look in the files section, there are a series of truely excellent papers in the folder 'Winch Dynamics and Performance' by George Moore. (soargsm) Essentially what George determened is that the major sensitivities a 1.Field length 2. Headwind 3. Cable tension as a percentage of glider flying weight. 4. Weight & drag of the cable There is very little extra height to be gained by agressive technique beyond just hitting your target airspeed and holding it there with smooth control inputs. This gives an angle of attack just slightly greater than that for best L/D. If you want help with this, put some AOA strings on the canopy sides and calibrate them for L/D max and Vmin sink. Of course, it goes without saying that you should never put yourself in danger by rotating into the climb so quickly that a recovery from a rope break is impossible. Smooth and accurate flying are what you want. So, if you want to get higher, get a longer field with more wind, replace steel with high strength Dyneema and get a winch that can accurately hold tension at 80 - 90% of the weak link. Bill Daniels 'Dan G' wrote in message ups.com... I'm interested in learning how to get the maximum possible height on a winch launch, without compromising safety in any way. This question has two parts really - how should the pilot fly the launch (pretty much how should he operate the elevator during the launch), how fast should the glider fly, and how should the winch driver feed the power in? For the sake of argument, let's assume the glider is a K13. For reference, I fly from an airfield with a 3,300' long cable, and the maximum height I achieve repeatedly is 1,700'. Headwind typically goes from around 10kts at the ground to something like (I estimate) 20kts at height. |
#9
|
|||
|
|||
How to get maximum height on a winch launch?
Dan G wrote:
We set the trim well forwards to give approach speed in the event of a launch failure (I am not going to stop doing that, but hypothetically where would you put the trim for best launch height?), Agreed - set the trim to suit the day. 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. We launch K.21s on a 240 hp diesel winch (Deutz air cooled V8) and never reach full power in normal circumstances. If an ASK-21 or G.103 is being launched the driver goes smoothly "through the stop" on "all out" and smoothly back to the stop when he sees the glider rotate into full climb. "Through the stop" means just that - not "on the end of throttle travel". After that it depends on conditions. In calm that setting can be kept most of the way up, but if there's a wind gradient the driver will be backing off as the glider gets into progressively stronger wind. The "stop" I mentioned is a spring loaded bar somewhere around (at a guess) 75% power. We use 3500 ft of cable and expect 1200 - 1500 ft from an ASK-21 flown two-up in normal conditions - 6 to 12 kts headwind. I'd endorse Bill's comment about hands-off trim. Our CFI regularly demonstrates this in an ASK-21. He claps slowly from just after lift-off to the top of the launch to show the student that he is flying hands off. -- martin@ | Martin Gregorie gregorie. | Essex, UK org | |
#10
|
|||
|
|||
How to get maximum height on a winch launch?
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. Ian |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Winch Launch Extreme 5200 ft | Walter Kronester | Soaring | 57 | December 14th 06 04:55 AM |
Winch operations | Edward Winchester | Soaring | 7 | April 13th 06 11:24 AM |
UAV's and TFR's along the Mexico boarder | John Doe | Piloting | 145 | March 31st 06 06:58 PM |
LIppmann reports a 950 meter winch launch with their Dynatec winch line - anything higher? | Bill Daniels | Soaring | 20 | December 27th 04 12:33 AM |
I need winch launch videos | Bill Daniels | Soaring | 21 | December 1st 04 06:41 PM |