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#41
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Winch Launch Safety Study
Bill,
I also wonder if you have considered gusts and turbulence on elevator authority. The winch RPM speed is not affected by this and will continue accelerating if that 's what you want, when gusts or turbulence affect the elevator. Even Tension controlled winches may not be able to reduce tension quickly enough if this happens. That's why the initial tension should not be too high to begin with. I would like to hear your description of how winch settings should be with some metrics. I know you advocate high initial tow acceleration launches. But that doesn't really tell me the specifics. |
#42
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Winch Launch Safety Study
As far I can find out, Bill has only done a few hundred launches on rather
underpowered and overgeared old US Gehrlein type winches, plus a couple of launches on his 'US Superwinch' in a Grob G103 before the drum was crushed by the synthetic cable, something else I warned him about! The G103, being low winged and quite heavy, is not prone to over-rotation accidents anyway, as identified in the Aerokourier report. I have personally witnessed several vastly overpowered launches involving K6 and K8 gliders, and have sat through 3 myself, in a K8, a Standard Cirrus and a DG101. They really do go into a near vertical climb, often despite the best efforts of the pilot to control the rotation. Particularly in the DG case I was lucky not to join the accidents statistics, as I slipped back up the seat as the glider rotated and was only able to keep the stick just off the backstop with my fingertips. Just about everyone in Europe, where we we have a lot of winch launching experience, disagrees with Bill's views. As to engineering data, I have seen none whatsoever from Bill, whereas I have supplied quite a lot plus illustrative videos on the Yahoo Winch Design Group. If you know the position of the belly hook and the centres of gravity and pressure in a given glider, it should be possible to calculate the rotational couple for various levels of pull, and at what level it will overpower the elevator. Derek Copeland At 01:24 22 March 2009, bildan wrote: On Mar 20, 7:00=A0am, Derek Copeland wrote: As I have tried to explain to Bill on numerous occasions, and on various forums, the uncontrollable over-rotation you get from an over-powered winch launch is caused by the pull line to the belly hook being below the glider's centre of gravity and centre of pressure. This causes a rotation for mechanical rather than aerodynamic control reasons. This is why high winged gliders, such as the K6 and K8 are most at risk. If you get such a launch, even holding the stick hard forward all the tim= e from 'take up slack' will not prevent the over-rotation, although it might slightly reduce your chances of instant death from a flick spin. Such events can be easily avoided by by controlling the winch so that the ground run acceleration is not more than about 1.0g (or less for the type= s mentioned above). This will still get you airborne and climbing within about 3-4 seconds, which most pilots find quite fast enough! It will also make very little difference to the achieved height. Derek Copeland At 22:41 19 March 2009, bildan wrote: As the glider leaves the ground, the inertial rotation will begin but if the acceleration continues, the elevator effectiveness will also continue to increase with the square of the airspeed. =A0Rotation can't happen instantly because the glider has mass and rotational inertia. In fact, the pilot has to start backing off the down elevator to allow the glider to rotate into the climb. Now, contrast this with a slow acceleration. =A0The glider staggers into the air and the nose-up inertial couple starts the rotation but the low speed and acceleration doesn't provide adequate control. =A0The nose rises as the pilot struggles to control it with inadequate airspeed..... I've collected stories on this type of accident for decades and they ALWAYS happen with slow acceleration. And just as often I've challenged you to produce ANY engineering data to support your mere opinion. You have not and I believe you cannot. |
#43
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Winch Launch Safety Study
Can anyone tell me more about how a Standard Cirrus handles when
winched? We use a GMC V8 325 HP petrol engine with standard automatic gearbox. No problems until now with K8, K6 and Astir Jeans. I plan to fit my Cirrus with a CG hook. Cirruses imported to France where all equipped with a nose hook. Willy VINKEN OO-ZNY On 22 Mar 2009 10:00:06 GMT, Del C wrote: As far I can find out, Bill has only done a few hundred launches on rather underpowered and overgeared old US Gehrlein type winches, plus a couple of launches on his 'US Superwinch' in a Grob G103 before the drum was crushed by the synthetic cable, something else I warned him about! The G103, being low winged and quite heavy, is not prone to over-rotation accidents anyway, as identified in the Aerokourier report. I have personally witnessed several vastly overpowered launches involving K6 and K8 gliders, and have sat through 3 myself, in a K8, a Standard Cirrus and a DG101. They really do go into a near vertical climb, often despite the best efforts of the pilot to control the rotation. Particularly in the DG case I was lucky not to join the accidents statistics, as I slipped back up the seat as the glider rotated and was only able to keep the stick just off the backstop with my fingertips. Just about everyone in Europe, where we we have a lot of winch launching experience, disagrees with Bill's views. As to engineering data, I have seen none whatsoever from Bill, whereas I have supplied quite a lot plus illustrative videos on the Yahoo Winch Design Group. If you know the position of the belly hook and the centres of gravity and pressure in a given glider, it should be possible to calculate the rotational couple for various levels of pull, and at what level it will overpower the elevator. Derek Copeland |
#44
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Winch Launch Safety Study
At 18:22 22 March 2009, Willy VINKEN wrote:
Can anyone tell me more about how a Standard Cirrus handles when winched? We use a GMC V8 325 HP petrol engine with standard automatic gearbox. No problems until now with K8, K6 and Astir Jeans. I plan to fit my Cirrus with a CG hook. Cirruses imported to France where all equipped with a nose hook. Willy VINKEN OO-ZNY As long as you don't get an overpowered winch launch it's fine. The ailerons are slightly ineffective at low speed, so try to choose a fit looking wing runner if you can. If it's one of the all-flying tailplane versions, just hold the stick about two-thirds forward and leave it there until you are established in the full climb. Just concentrate on keeping the wings level and the glider running straight during the ground run and rotation. If there is any chance of dropping a wingtip onto the ground, pull off immediately. It will naturally rotate quite enthusiatically after lift off, but avoid ramming the stick hard forward to contain this, as this is what can stall the tailplane. Don't try to winch launch on a nose hook, because it will give a very poor launch, and there is no back release mechanism on a the type of nose hook fitted to this type. The Standard Cirrus doesn't have the best positioned shoulder strap mountings, so make sure you do your safety harness up as tightly as possible to avoid slipping back up the seat, due to the acceleration. Derek Copeland |
#45
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Winch Launch Safety Study
At 18:22 22 March 2009, Willy VINKEN wrote:
Can anyone tell me more about how a Standard Cirrus handles when winched? We use a GMC V8 325 HP petrol engine with standard automatic gearbox. No problems until now with K8, K6 and Astir Jeans. I plan to fit my Cirrus with a CG hook. Cirruses imported to France where all equipped with a nose hook. Willy VINKEN OO-ZNY We operated a Standard Cirrus for 3 years on the winch and found no handling problems provided the elevator was moved progressively. The AMT is quite powerfull and has been known to stall on full down deflection , but we never experienced it . On 22 Mar 2009 10:00:06 GMT, Del C wrote: As far I can find out, Bill has only done a few hundred launches on rather underpowered and overgeared old US Gehrlein type winches, plus a couple of launches on his 'US Superwinch' in a Grob G103 before the drum was crushed by the synthetic cable, something else I warned him about! The G103, being low winged and quite heavy, is not prone to over-rotation accidents anyway, as identified in the Aerokourier report. I have personally witnessed several vastly overpowered launches involving K6 and K8 gliders, and have sat through 3 myself, in a K8, a Standard Cirrus and a DG101. They really do go into a near vertical climb, often despite the best efforts of the pilot to control the rotation. Particularly in the DG case I was lucky not to join the accidents statistics, as I slipped back up the seat as the glider rotated and was only able to keep the stick just off the backstop with my fingertips. Just about everyone in Europe, where we we have a lot of winch launching experience, disagrees with Bill's views. As to engineering data, I have seen none whatsoever from Bill, whereas I have supplied quite a lot plus illustrative videos on the Yahoo Winch Design Group. If you know the position of the belly hook and the centres of gravity and pressure in a given glider, it should be possible to calculate the rotational couple for various levels of pull, and at what level it will overpower the elevator. Derek Copeland |
#46
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Winch Launch Safety Study
At 19:30 22 March 2009, Del C wrote:
At 18:22 22 March 2009, Willy VINKEN wrote: Can anyone tell me more about how a Standard Cirrus handles when winched? We use a GMC V8 325 HP petrol engine with standard automatic gearbox. No problems until now with K8, K6 and Astir Jeans. I plan to fit my Cirrus with a CG hook. Cirruses imported to France where all equipped with a nose hook. Willy VINKEN OO-ZNY As long as you don't get an overpowered winch launch it's fine. The ailerons are slightly ineffective at low speed, so try to choose a fit looking wing runner if you can. If it's one of the all-flying tailplane versions, just hold the stick about two-thirds forward and leave it there until you are established in the full climb. Just concentrate on keeping the wings level and the glider running straight during the ground run and rotation. If there is any chance of dropping a wingtip onto the ground, pull off immediately. It will naturally rotate quite enthusiatically after lift off, but avoid ramming the stick hard forward to contain this, as this is what can stall the tailplane. Don't try to winch launch on a nose hook, because it will give a very poor launch, and there is no back release mechanism on a the type of nose hook fitted to this type. The Standard Cirrus doesn't have the best positioned shoulder strap mountings, so make sure you do your safety harness up as tightly as possible to avoid slipping back up the seat, due to the acceleration. Derek Copeland I concur with Derek. I brace my right arm against my thigh and hold the stick part way down so any bumps on the ground run will have much less effect. (I learnt on a UK hill site). Mine has a all flying tail and I do what Derek describes. I don't need to adjust the position of the stick (in terms of pitch) until well into the climb and that is just fine tuning. Yes, tighten the straps before launch and press firmly back on the pedals before launch to compress parachute/back rest arrangements (I have 50mm of dynafoam behind me) to ensure you don't slip back on launch. No problems with a V8 power Tost winch. Fitting winglets last season made the ailerons more responsive at low speed. Read the flight manual about launching (which basically says what Derek and I have). Also look at the Standard Cirrus website http://www.standardcirrus.org and also look at the Std Cirrus Forum. There is a search facility so look for 'launch'. The Std Cirrus hook is well protected by 2 parallel metal strips. Practice getting the cable on yourself so you can describe to helpers how they should fit the cable. They tend to get a bit confused because they can't see the hook like K8s and Astirs etc. As my first CFI says: Its a glider - go any fly it as you would a glider! Gavin Std Cirrus, CNN now G-SCNN, #173 LSV Viersen, Keiheuvel, Belgium |
#47
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Winch Launch Safety Study
In addition to what Gavin and Derek said I think it is also important
to know that the location of your Centre of Gravity has a significant influence on the winch launch characterisitics of the Standard Cirrus. Make sure it is no-where near the rear end of the allowable range. I can't remember the figures but recall having it close to mid-range and always felt comfortable. To prevent sliding into the baggage compartment I always took the pedals right back and trapped myself between pedals and rear canopy rim during winch launch. Marcel Dünner |
#48
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Winch Launch Safety Study
Some of you might be interested in the latest British Gliding Association
(BGA) Winch Launching Safety Campaign, which includes some frightening simulations of what can go wrong if you approach winching in a too cavalier manner. Taking off with the stick hard back, possibly as a result of sliding back up the seat, is one of them, and has been responsible for several fatal accidents in the UK. See: http://www.gliding.co.uk/bgainfo/saf...nch-safety.htm Derek Copeland At 12:45 24 March 2009, MaD wrote: In addition to what Gavin and Derek said I think it is also important to know that the location of your Centre of Gravity has a significant influence on the winch launch characterisitics of the Standard Cirrus. Make sure it is no-where near the rear end of the allowable range. I can't remember the figures but recall having it close to mid-range and always felt comfortable. To prevent sliding into the baggage compartment I always took the pedals right back and trapped myself between pedals and rear canopy rim during winch launch. Marcel D=FCnner |
#49
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Winch Launch Safety Study
...... and do the quiz .....
chris On 24/03/2009 1:45 PM, Derek Copeland wrote: Some of you might be interested in the latest British Gliding Association (BGA) Winch Launching Safety Campaign, which includes some frightening simulations of what can go wrong if you approach winching in a too cavalier manner. Taking off with the stick hard back, possibly as a result of sliding back up the seat, is one of them, and has been responsible for several fatal accidents in the UK. See: http://www.gliding.co.uk/bgainfo/saf...nch-safety.htm Derek Copeland At 12:45 24 March 2009, MaD wrote: In addition to what Gavin and Derek said I think it is also important to know that the location of your Centre of Gravity has a significant influence on the winch launch characterisitics of the Standard Cirrus. Make sure it is no-where near the rear end of the allowable range. I can't remember the figures but recall having it close to mid-range and always felt comfortable. To prevent sliding into the baggage compartment I always took the pedals right back and trapped myself between pedals and rear canopy rim during winch launch. Marcel D=FCnner |
#50
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Winch Launch Safety Study
On Mar 21, 9:00*pm, wrote:
Bill, Aside from your rude remarks and your inability to admit your mistakes on several points (an automatic transmissions do not operate like a cruise control), etc..... I didn't say anything remotely like that. I said they ASSIST the driver in maintaining speed by increasing torque multipication when climbing hills. Now let me ask you a question for once: What rope tension, measured in g do you recommend for the first seconds of the launch? Or do you advocate RPM controlled winches over tension controlled ones? I advocate tension controlled winches and the tension should be the maximum safe value. |
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