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On 22/02/2014 16:17, Alan wrote:
...You don't get kiting if you fly normal "high" tow behind the towplane, if you remain in control. If you don't remain in control, starting from low tow is not going to make a lot of difference. Experience (tens of thousands of aerotows) shows there is an enormous difference. The inadequate control and time to go from high tow to kiting is orders of magnitude different from that required to go from low tow to kiting. In fact, I've never heard of that ever happening. Even with low time students. Kiting from high tow, however, is apparently so common as to need a whole new system of electronic whizzbangery and gallons of bandwidth to stop. If the tug has just lifted off, being in low tow sounds a bit difficult, but that would be a particularly hazardous time. Yes. Liftoff is a time to be wary and we train accordingly. Nevertheless, all I can say is that low tow has prevented kiting accidents for many years. But don't take my word for it, keep this ridiculous discussion going with another screwball idea for pivoting, autoswivelling, pitch-sensing, stick-following nonsense. If the issue is serious - as it was in Australia - flying low tow will solve it. If it isn't - see my previous post. GC As for automatic methods to mitigate the problem, perhaps the solution is not to modify tow planes, but to modify gliders. If the glider is in a very high pitch attitude on tow, it might be a good time to automatically release. Another modification might be to attach the tow rope to the top of the glider. This would cause the tow force to pitch the glider down. Is this more of a problem when folks try to tow a slow glider like a 2-33 at high speeds? Alan |
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The time difference to go from low tow to kiting compared to high tow to
kiting is about 1 second - try it at safe altitude. As observed you can't take-off in low tow so the highest risk time, just after take off when the combination is accelerating, is exactly the same. The transition from normal tow to low tow, early in the climb, puts the glider into the turbulence of the prop-wash which may well cause the, less than one second, loss of control which is all that is needed to start the kiting. Finally, low tow on a glider with a C of G hook, leaves the rope wrapped around the side of the cockpit, not really a good idea and C of G hooks are where the danger lies. The cheapest mechanical solution is, fit a nose hook to any glider that is going to be aerotowed. My best estimate of low level kiting fatal/serious accident frequency is of the order of one in a million. "Tens of thousands of aerotows" is not a big enough sample to draw conclusions. At 07:58 22 February 2014, GC wrote: On 22/02/2014 16:17, Alan wrote: ...You don't get kiting if you fly normal "high" tow behind the towplane, if you remain in control. If you don't remain in control, starting from low tow is not going to make a lot of difference. Experience (tens of thousands of aerotows) shows there is an enormous difference. The inadequate control and time to go from high tow to kiting is orders of magnitude different from that required to go from low tow to kiting. In fact, I've never heard of that ever happening. Even with low time students. Kiting from high tow, however, is apparently so common as to need a whole new system of electronic whizzbangery and gallons of bandwidth to stop. If the tug has just lifted off, being in low tow sounds a bit difficult, but that would be a particularly hazardous time. Yes. Liftoff is a time to be wary and we train accordingly. Nevertheless, all I can say is that low tow has prevented kiting accidents for many years. But don't take my word for it, keep this ridiculous discussion going with another screwball idea for pivoting, autoswivelling, pitch-sensing, stick-following nonsense. If the issue is serious - as it was in Australia - flying low tow will solve it. If it isn't - see my previous post. GC As for automatic methods to mitigate the problem, perhaps the solution is not to modify tow planes, but to modify gliders. If the glider is in a very high pitch attitude on tow, it might be a good time to automatically release. Another modification might be to attach the tow rope to the top of the glider. This would cause the tow force to pitch the glider down. Is this more of a problem when folks try to tow a slow glider like a 2-33 at high speeds? Alan |
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On Saturday, February 22, 2014 1:58:28 AM UTC-6, GC wrote:
On 22/02/2014 16:17, Alan wrote: ...You don't get kiting if you fly normal "high" tow behind the towplane, if you remain in control. If you don't remain in control, starting from low tow is not going to make a lot of difference. Experience (tens of thousands of aerotows) shows there is an enormous difference. The inadequate control and time to go from high tow to kiting is orders of magnitude different from that required to go from low tow to kiting. In fact, I've never heard of that ever happening. Even with low time students. Kiting from high tow, however, is apparently so common as to need a whole new system of electronic whizzbangery and gallons of bandwidth to stop. If the tug has just lifted off, being in low tow sounds a bit difficult, but that would be a particularly hazardous time. Yes. Liftoff is a time to be wary and we train accordingly. Nevertheless, all I can say is that low tow has prevented kiting accidents for many years. But don't take my word for it, keep this ridiculous discussion going with another screwball idea for pivoting, autoswivelling, pitch-sensing, stick-following nonsense. If the issue is serious - as it was in Australia - flying low tow will solve it. If it isn't - see my previous post. GC As for automatic methods to mitigate the problem, perhaps the solution is not to modify tow planes, but to modify gliders. If the glider is in a very high pitch attitude on tow, it might be a good time to automatically release. Another modification might be to attach the tow rope to the top of the glider. This would cause the tow force to pitch the glider down. Is this more of a problem when folks try to tow a slow glider like a 2-33 at high speeds? Alan GC is making his point for low tows very convincingly - why is he immediately being ripped, Chris? Preparing and steering into low tow at a safe altitude, say 300', means to mentally and then practically pushing the stick forward and then holding in the low tow position. That's the opposite maneuver of what's leading to kiting. Drifting upwards takes you into the prop wash and again, it takes forward stick pressure to move into the safe spot. That feedback mechanism is correctly maintaining the intended safe spot while in the normal tow position only visual cues are being used. I think I'll give the low tow a try, if ever that polar vortex over Chicago makes like tree... Herb |
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Huh! Sounds good to me!
"GC" wrote in message eb.com... On 22/02/2014 16:17, Alan wrote: ...You don't get kiting if you fly normal "high" tow behind the towplane, if you remain in control. If you don't remain in control, starting from low tow is not going to make a lot of difference. Experience (tens of thousands of aerotows) shows there is an enormous difference. The inadequate control and time to go from high tow to kiting is orders of magnitude different from that required to go from low tow to kiting. In fact, I've never heard of that ever happening. Even with low time students. Kiting from high tow, however, is apparently so common as to need a whole new system of electronic whizzbangery and gallons of bandwidth to stop. If the tug has just lifted off, being in low tow sounds a bit difficult, but that would be a particularly hazardous time. Yes. Liftoff is a time to be wary and we train accordingly. Nevertheless, all I can say is that low tow has prevented kiting accidents for many years. But don't take my word for it, keep this ridiculous discussion going with another screwball idea for pivoting, autoswivelling, pitch-sensing, stick-following nonsense. If the issue is serious - as it was in Australia - flying low tow will solve it. If it isn't - see my previous post. GC As for automatic methods to mitigate the problem, perhaps the solution is not to modify tow planes, but to modify gliders. If the glider is in a very high pitch attitude on tow, it might be a good time to automatically release. Another modification might be to attach the tow rope to the top of the glider. This would cause the tow force to pitch the glider down. Is this more of a problem when folks try to tow a slow glider like a 2-33 at high speeds? Alan |
#5
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I hear you on the low tow, GC. It is another of those perceptions of "It isn't what we do, so it must be dangerous." Agree that it will change the dynamics involved, as well. Did Australia go to low tow to prevent kiting, or was it for some other reason and that was a side benefit? I know that high tow increases the trim drag on the towplane, and low tow reduces it, so on low powered towplanes, this can be the difference between climbing and not. With America tending to be a land of excess (horsepower in our towplanes), it is seldom an issue.
So, I am curious. Was the change made to improve climb rates and you just have not seen kiting events in Australia, or was there a significant kiting problem, and low tow was determined to be a solution? No, I am not being snide or snarky, I do not know and would like ot learn. Eyes and ears open, willing to learn. Steve Leonard |
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On Sunday, February 23, 2014 10:00:51 AM UTC-5, Steve Leonard wrote:
I hear you on the low tow, GC. It is another of those perceptions of "It isn't what we do, so it must be dangerous." Agree that it will change the dynamics involved, as well. Did Australia go to low tow to prevent kiting, or was it for some other reason and that was a side benefit? I know that high tow increases the trim drag on the towplane, and low tow reduces it, so on low powered towplanes, this can be the difference between climbing and not. With America tending to be a land of excess (horsepower in our towplanes), it is seldom an issue. So, I am curious. Was the change made to improve climb rates and you just have not seen kiting events in Australia, or was there a significant kiting problem, and low tow was determined to be a solution? No, I am not being snide or snarky, I do not know and would like ot learn. Eyes and ears open, willing to learn. Steve Leonard I'll speak for one operation in US using low tow. 1- Reduced trim drag- glider is on the thrust line of the tug. 2-Easier to fly and teach due to visual picture being good and getting near the wake gives feel of vertical tail touching the wake allowing minor correction to stay away. In high tow the fuselage and wing get in first acusing a bit more disturbance to the glider attitude. 3- Many students fly the tow without help on their first try. I doubt that happens much in high (normal) tow. 4- Almost never get slack rope because descending position is easily seen. We have to go out of our way to teach slack rope correction. 5- No broken ropes. 6- No affect on attitude of tug due to rope reduces tug pilot workload. 7- Glider is not in the wake on takeoff because ground effect dissipates the wake below about 1 wing span. 8- I have not heard of any dead tug pilots in low tow. Flame suit on UH |
#7
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I'm confused by a couple of statements in this thread...
1) "Low tow prevents kiting" Doesn't the kiting event often happen in early take-off, just as glider is leaving the ground, and before low-tow is established??? 2) "Nose hook prevents kiting" Didn't we have at least one fatal accident in USA with a nosehook (L-13 IIRCC)??? Others??? Anybody have any facts (Yes, I know, its RAS, but...)??? I'm not saying nose-hooks don't help, however... But then, I'm easily confused... Thanks, Best Regards, Dave |
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On 24/02/2014 02:00, Steve Leonard wrote:
I hear you on the low tow, GC. It is another of those perceptions of "It isn't what we do, so it must be dangerous." Agree that it will change the dynamics involved, as well. Did Australia go to low tow to prevent kiting, or was it for some other reason and that was a side benefit? I know that high tow increases the trim drag on the towplane, and low tow reduces it, so on low powered towplanes, this can be the difference between climbing and not. With America tending to be a land of excess (horsepower in our towplanes), it is seldom an issue. So, I am curious. Was the change made to improve climb rates and you just have not seen kiting events in Australia, or was there a significant kiting problem, and low tow was determined to be a solution? No, I am not being snide or snarky, I do not know and would like ot learn. The change was made well before my time in soaring (at least 30 years ago - in the era where K-6's were just disappearing) but I understand that kiting specifically and easier control on tow generally were the reasons for the change. Certainly, it was nothing to do with climb rates. Like the Western US and South Africa, Australia experiences strong, sharp-edged thermals which can be challenging to handle on tow. As Chris's experiments showed, low wing loading gliders are more susceptible to kiting and it was a real problem at the time. Low tow isn't a silver bullet (nothing in aviation is) but it certainly stops these problems becoming accidents in a way that apparently still happens in the UK and US. I believe that mandatory nose hooks for aerotow came in at the same time but I can't confirm that. As Kirk said, nose hook aerotow is probably the more important change but my instructing experience makes me think that both play an important part. I'm sure that what Australia did may well be overkill for the Eastern US and much of Europe but I entered the discussion simply to point out that no electronic solution was needed. A perfectly simple operational change would secure all the safety anyone wanted - if that was the point of the discussion. Otherwise it looked like a solution in search of a problem. ![]() I have nothing useful to contribute on low/high-powered tugs. I've never noticed any difference. I will say that I've never complained of excess power in any aircraft I've flown! GC Eyes and ears open, willing to learn. Steve Leonard |
#9
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GC, the GFA put out a safety poster around 30 years ago that actually had
line drawings, of the photos taken of the test I described, all superimposed on one another (if you can find a copy and make it accessible, that would help the discussion). I believe the banning of C of G hooks for aerotowing and the adoption of low tow at about that time were also, at least in part, the result of those tests. I think the banning of C of G hooks is the primary reason for Australia's good record on these sort of accidents, the use of low tow, whilst it may have other benefits does not, in my opinion, contribute significantly, if at all. When the weather improves in the UK and I can get some spare time, I plan to conduct some more tests, with another aircraft alongside to video them. I'll include a kiting departure on a C of G hook from low tow as one of the tests. It is possible to get tow plane upsets resulting from significant glider out of position events when on a nose hook. However they don't happen as fast and there is often time for one or other pilot to release and they don't become irrecoverable in the way that a kiting event is. At 04:17 24 February 2014, GC wrote: On 24/02/2014 02:00, Steve Leonard wrote: I hear you on the low tow, GC. It is another of those perceptions of "It isn't what we do, so it must be dangerous." Agree that it will change the dynamics involved, as well. Did Australia go to low tow to prevent kiting, or was it for some other reason and that was a side benefit? I know that high tow increases the trim drag on the towplane, and low tow reduces it, so on low powered towplanes, this can be the difference between climbing and not. With America tending to be a land of excess (horsepower in our towplanes), it is seldom an issue. So, I am curious. Was the change made to improve climb rates and you just have not seen kiting events in Australia, or was there a significant kiting problem, and low tow was determined to be a solution? No, I am not being snide or snarky, I do not know and would like ot learn. The change was made well before my time in soaring (at least 30 years ago - in the era where K-6's were just disappearing) but I understand that kiting specifically and easier control on tow generally were the reasons for the change. Certainly, it was nothing to do with climb rates. Like the Western US and South Africa, Australia experiences strong, sharp-edged thermals which can be challenging to handle on tow. As Chris's experiments showed, low wing loading gliders are more susceptible to kiting and it was a real problem at the time. Low tow isn't a silver bullet (nothing in aviation is) but it certainly stops these problems becoming accidents in a way that apparently still happens in the UK and US. I believe that mandatory nose hooks for aerotow came in at the same time but I can't confirm that. As Kirk said, nose hook aerotow is probably the more important change but my instructing experience makes me think that both play an important part. I'm sure that what Australia did may well be overkill for the Eastern US and much of Europe but I entered the discussion simply to point out that no electronic solution was needed. A perfectly simple operational change would secure all the safety anyone wanted - if that was the point of the discussion. Otherwise it looked like a solution in search of a problem. ![]() I have nothing useful to contribute on low/high-powered tugs. I've never noticed any difference. I will say that I've never complained of excess power in any aircraft I've flown! GC Eyes and ears open, willing to learn. Steve Leonard |
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