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#41
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Winch Launch - Fatal
On Sunday, December 11, 2016 at 3:15:02 AM UTC-7, Peter Whitehead wrote:
On Tuesday, 6 December 2016 14:15:05 UTC, Jock Proudfoot wrote: Modern winches are powerful so the ground run is shorter, and it is this which allows greater height on launch (you are effectively lengthening the airfield compared to those with "anaemic winches"). The problem is the acceleration and reduction in time to sort out the problem with wing drop on the ground, and also a stall and wing drop (to inverted ) in the rotation (to climb).This can all happen too quickly for human responses. It kills "smart" people. Please do read and digest (and disseminate) the following link from experts in the field, the BGA. This programme of "safe winching" has shown reduction (evidence based) in accidents and fatalities in this mode of launching.. https://www.bfgc.co.uk/Documents/Winching.pdf Pete Whitehead I read every new issue of the BGA safe winching and note a slow movement toward scientific rationality such as the deletion of the ridiculous graphic showing a glider pitching up due to acceleration. There is NO time to "sort out problems" in the ground roll - the only option is to prevent them in the first place. 1. Balance the wing, not just level it. 2. Point the glider EXACTLY at the winch. 3. PRECISELY center all controls and don't wag the stick around in the roll.. 4. Above all, don't force a pilot to wobble along during an extended ground roll while struggling to keep the wings level. A normal winch acceleration is 19 knots per second (1G) which gets the glider to aileron control airspeed in less than a second and airborne in about two seconds. If rules 1 - 3 above are followed it's almost impossible to imagine a wing drop before the glider is airborne and out of danger. |
#42
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Winch Launch - Fatal
1. Balance the wing, not just level it. 2. Point the glider EXACTLY at the winch. 3. PRECISELY center all controls and don't wag the stick around in the roll. 4. Above all, don't force a pilot to wobble along during an extended ground roll while struggling to keep the wings level. I have an issue with points 2 and 3: you're of course right if the winch hook is on the center line of the glider. However, many gliders (e.g. Ka-6, ASK-13, ASK-21) have an off-centre winch hook. With a left of centre hook, the initial acceleration causes a marked yaw to the right. It is much better in this case to align the glider pointing slightly to the left of the winch, and giving left rudder at the start. |
#43
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Winch Launch - Fatal
On Sun, 11 Dec 2016 16:03:09 -0800, stephanevdv wrote:
1. Balance the wing, not just level it. 2. Point the glider EXACTLY at the winch. 3. PRECISELY center all controls and don't wag the stick around in the roll. 4. Above all, don't force a pilot to wobble along during an extended ground roll while struggling to keep the wings level. I have an issue with points 2 and 3: you're of course right if the winch hook is on the center line of the glider. However, many gliders (e.g. Ka-6, ASK-13, ASK-21) have an off-centre winch hook. With a left of centre hook, the initial acceleration causes a marked yaw to the right. It is much better in this case to align the glider pointing slightly to the left of the winch, and giving left rudder at the start. There was a discussion about this during my club's launch marshal meeting today. The consensus was that there is a potential problem with point 3 because many pilots think 'balanced turn' and also add some aileron, thus inviting wing drop, when leaving the ailerons centralised and just applying rudder is the correct course. Centralising all controls avoids this. I should add that we use SZD Juniors, which have a larger left hook offset than any of the gliders you mention and consequently a stronger tendency to swing right, especially if there is a cross-wind from the right! I start winch launches with controls centred regardless of whether I'm flying my Libelle or one of the club's fleet (Junior, ASK-21, Puchacz or Grob G103). In all cases you can get rudder on fast enough to control a swing if you're paying attention, and what are you doing as PIC if you aren't paying attention? -- martin@ | Martin Gregorie gregorie. | Essex, UK org | |
#44
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Winch Launch - Fatal
At 00:44 12 December 2016, Martin Gregorie wrote:
On Sun, 11 Dec 2016 16:03:09 -0800, stephanevdv wrote: 1. Balance the wing, not just level it. 2. Point the glider EXACTLY at the winch. 3. PRECISELY center all controls and don't wag the stick around in the roll. 4. Above all, don't force a pilot to wobble along during an extended ground roll while struggling to keep the wings level. I have an issue with points 2 and 3: you're of course right if the winch hook is on the center line of the glider. However, many gliders (e.g. Ka-6, ASK-13, ASK-21) have an off-centre winch hook. With a left of centre hook, the initial acceleration causes a marked yaw to the right. It is much better in this case to align the glider pointing slightly to the left of the winch, and giving left rudder at the start. There was a discussion about this during my club's launch marshal meeting today. The consensus was that there is a potential problem with point 3 because many pilots think 'balanced turn' and also add some aileron, thus inviting wing drop, when leaving the ailerons centralised and just applying rudder is the correct course. Centralising all controls avoids this. I should add that we use SZD Juniors, which have a larger left hook offset than any of the gliders you mention and consequently a stronger tendency to swing right, especially if there is a cross-wind from the right! I start winch launches with controls centred regardless of whether I'm flying my Libelle or one of the club's fleet (Junior, ASK-21, Puchacz or Grob G103). In all cases you can get rudder on fast enough to control a swing if you're paying attention, and what are you doing as PIC if you aren't paying attention? -- martin@ | Martin Gregorie gregorie. | Essex, UK org | You are absolutely right Martin and the point you make is crucial. Whatever the glider, the crosswind or any other factor the controls should all be centered, or in the case of the elevator, neutral to the trim setting or takeoff position (I find a T21 needs the stick well forward). The controls should only ever be used to correct a departure from the attitude required, or to select an attitude required, never, in the context of a winch launch, to anticipate a perceived or potential problem. If any force is needed by the wing tip runner to hold the wings level with the ailerons central this can be corrected by lifting or lowering the wing by a small amount to balance, a Bill has said. If however balance cannot be achieved with a small lowering or lifting then serious thought should be given as to if the launch should be attempted. |
#45
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Winch Launch - Fatal
On Sunday, December 11, 2016 at 5:03:12 PM UTC-7, wrote:
1. Balance the wing, not just level it. 2. Point the glider EXACTLY at the winch. 3. PRECISELY center all controls and don't wag the stick around in the roll. 4. Above all, don't force a pilot to wobble along during an extended ground roll while struggling to keep the wings level. I have an issue with points 2 and 3: you're of course right if the winch hook is on the center line of the glider. However, many gliders (e.g. Ka-6, ASK-13, ASK-21) have an off-centre winch hook. With a left of centre hook, the initial acceleration causes a marked yaw to the right. It is much better in this case to align the glider pointing slightly to the left of the winch, and giving left rudder at the start. Swing due to an offset hook is minimal if the acceleration is high. Acceleration increases the download on the tail wheel forcing the glider to roll straight. In any event a slight drift to the side is of no consequence - you're not trying to fly formation on a winch. |
#46
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Winch Launch - Fatal
On Tuesday, December 13, 2016 at 4:19:31 PM UTC+1, wrote:
On Sunday, December 11, 2016 at 5:03:12 PM UTC-7, wrote: 1. Balance the wing, not just level it. 2. Point the glider EXACTLY at the winch. 3. PRECISELY center all controls and don't wag the stick around in the roll. 4. Above all, don't force a pilot to wobble along during an extended ground roll while struggling to keep the wings level. I have an issue with points 2 and 3: you're of course right if the winch hook is on the center line of the glider. However, many gliders (e.g. Ka-6, ASK-13, ASK-21) have an off-centre winch hook. With a left of centre hook, the initial acceleration causes a marked yaw to the right. It is much better in this case to align the glider pointing slightly to the left of the winch, and giving left rudder at the start. Swing due to an offset hook is minimal if the acceleration is high. Acceleration increases the download on the tail wheel forcing the glider to roll straight. In any event a slight drift to the side is of no consequence - you're not trying to fly formation on a winch. I can confirm that to be correct! I have flown everything from the K6,8,13 and the ASW-15 with an off-set CG hook and there was never any condition that could not be corrected or controlled with rudder input. And before someone chimes in about the oh so dangerous L-13 Y-bridle CG hooks: no - launching on just one hook because the other one fell out does not cause a spectacular ground-loop, accident or male pattern hair-loss! ;-) Uli |
#47
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Winch Launch - Fatal
On Tuesday, December 13, 2016 at 1:32:58 PM UTC-6, AS wrote:
On Tuesday, December 13, 2016 at 4:19:31 PM UTC+1, wrote: On Sunday, December 11, 2016 at 5:03:12 PM UTC-7, wrote: 1. Balance the wing, not just level it. 2. Point the glider EXACTLY at the winch. 3. PRECISELY center all controls and don't wag the stick around in the roll. 4. Above all, don't force a pilot to wobble along during an extended ground roll while struggling to keep the wings level. I have an issue with points 2 and 3: you're of course right if the winch hook is on the center line of the glider. However, many gliders (e.g. Ka-6, ASK-13, ASK-21) have an off-centre winch hook. With a left of centre hook, the initial acceleration causes a marked yaw to the right. It is much better in this case to align the glider pointing slightly to the left of the winch, and giving left rudder at the start. Swing due to an offset hook is minimal if the acceleration is high. Acceleration increases the download on the tail wheel forcing the glider to roll straight. In any event a slight drift to the side is of no consequence - you're not trying to fly formation on a winch. I can confirm that to be correct! I have flown everything from the K6,8,13 and the ASW-15 with an off-set CG hook and there was never any condition that could not be corrected or controlled with rudder input. And before someone chimes in about the oh so dangerous L-13 Y-bridle CG hooks: no - launching on just one hook because the other one fell out does not cause a spectacular ground-loop, accident or male pattern hair-loss! ;-) Uli Uli and Bill D beat me to it: that's exactly my experience. The offset hook myth is just that, an old wifes tale, to be used for bedtime stories to scare your children. Herb |
#48
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Winch Launch - Fatal
On Tuesday, December 13, 2016 at 3:37:14 PM UTC-7, wrote:
On Tuesday, December 13, 2016 at 1:32:58 PM UTC-6, AS wrote: On Tuesday, December 13, 2016 at 4:19:31 PM UTC+1, wrote: On Sunday, December 11, 2016 at 5:03:12 PM UTC-7, wrote: 1. Balance the wing, not just level it. 2. Point the glider EXACTLY at the winch. 3. PRECISELY center all controls and don't wag the stick around in the roll. 4. Above all, don't force a pilot to wobble along during an extended ground roll while struggling to keep the wings level. I have an issue with points 2 and 3: you're of course right if the winch hook is on the center line of the glider. However, many gliders (e.g. Ka-6, ASK-13, ASK-21) have an off-centre winch hook. With a left of centre hook, the initial acceleration causes a marked yaw to the right. It is much better in this case to align the glider pointing slightly to the left of the winch, and giving left rudder at the start. Swing due to an offset hook is minimal if the acceleration is high. Acceleration increases the download on the tail wheel forcing the glider to roll straight. In any event a slight drift to the side is of no consequence - you're not trying to fly formation on a winch. I can confirm that to be correct! I have flown everything from the K6,8,13 and the ASW-15 with an off-set CG hook and there was never any condition that could not be corrected or controlled with rudder input. And before someone chimes in about the oh so dangerous L-13 Y-bridle CG hooks: no - launching on just one hook because the other one fell out does not cause a spectacular ground-loop, accident or male pattern hair-loss! ;-) Uli Uli and Bill D beat me to it: that's exactly my experience. The offset hook myth is just that, an old wifes tale, to be used for bedtime stories to scare your children. Herb Actually, just to be obstinate, there is a scenario where an offset hook will induce a swing to the side. That's under ridiculously low acceleration where the glider swings a bit each time the tailwheel bounces. Increase the acceleration to a normal 1G and the down-force on the tailwheel will keep the glider rolling straight. |
#49
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Winch Launch - Fatal
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#50
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Winch Launch - Fatal
On Tuesday, December 6, 2016 at 7:15:05 AM UTC-7, Jock Proudfoot wrote:
You're right, relying on the pilot pulling the release doesn't work simply because it takes too long for the pilot to react. I think there is just one cause of ground roll accidents and it's very simple - inadequate acceleration. A glider just wants to fly and with the wing incidence angle at about 10 degrees with the tailwheel on the ground it will do so in about 2 seconds at 1G. Unless things are badly set up beforehand, the wings will stay balanced for at least that long. Once airborne. there is no risk of a ground roll accident. The acceleration which worked with old wooden glider just doesn't get a heavy glass glider to aileron control speed and then airborne quickly enough. Don, you brought up the old pitch-up myth so I'll go there. Pitch-up on acceleration can only happen with the tailwheel in the air and that can only happen if the glider is slowly dragged into the air with feeble acceleration and THEN strong acceleration applied. It can't happen if strong acceleration is applied at the very start of the ground roll and maintained until the glider reaches the normal airspeed for rotating into the climb. I could go on at length about this but I wrote a long paper on it available here https://dl.dropboxusercontent.com/u/...celeration.pdf Rather than take my word for it, I very strongly suggest the BGA and other national clubs do their own investigation using tension loggers. What you will see may terrify you. |
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