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#31
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"Bruce Greeff" wrote in message ... Hi Bill I respect your views but there are some differences in the way we see things he Firstly please note that I am not advocating underpowered winches. I do however maintain that power is not the most important safety issue in winch launching, and that - for our fleet where the highest wingloading is relatively modest, and the heaviest glider is a Blanik L13 - a winch with 220Hp is adequate. (maybe 250 would be better) Bill Daniels wrote: We have had several people writing that they have launched heavy glider X with a low powered winch. I have done it and so have many others, but this is still not a good idea. There are serious dangers involved. Too low power is dangerous, and we agree entirely that more power is desirable. Interestingly the most recent National Safety meeting addressed winch launching as the primary theme. There were 25 Safety Officers and at least ten Chief Flying Instructors as well as the SSSA Exco present. One thing that became apparent was that there is no optimal power winch. In particular - when launching old designs that are light, high wing with the hook at a considerable vertical displacement from the wing, there have been numerous dangerous launches where the initial acceleration exceeds the control authority on the glider. The example given was launching a Ka8 with the stick hard against the forward stop for most of the launch. Too much acceleration is as dangerous as too little. The best way to look at it is to consider power demand and supply. The winch engine should be able to supply all the power the glider demands. If the glider demands more power that is available by pulling up hard, the airspeed will decay quickly. If the pilot knows this is going to happen, he can manage it by controlling the pitch attitude carefully. If he doesn't expect it, the airspeed will decay so quickly that a very dangerous situation will develop. Agreed, and all of our pilots have to learn to control their demands on the winch before going solo. In this respect it would be safer and better to have more power for perhaps 30% of our fleet. Conversely, any piulot who relies on the generous power reserve of the winch to compensate for pulling back too hard is dangerous. I am all for the speed decay to warn the pilot. That way, when the winch falters, he will compensate automatically because he will be used to monitoring and controlling airspeed carefully. The attempt to launch gliders with a low powered winch gets into who is in control of the launch. I think it goes without saying that who controls the launch should not be in doubt. The majority view is clearly that the winch driver should be in charge. Here I differ, the pilot is always in control of his / her destiny. Our process is that the launch marshal controlls the launch process, and the winch driver and pilot must work together. A skilled winch driver is in control at all times within the parameters dictated by physics. If we have a pilot who over rotates and "bends the pole" a number of things will happen. With the exception of the Blanik with its flaps deployed the winch driver will be able to keep the glider above stall speed with full throttle. The winch driver is still in control and may decide that the probability of a maximum tension cable break is dangerously high and elect to reduce power until the pilot takes the pressure off the cable. (even if it results in a low release) If the pilot is being ham fisted the cable will probably break resulting in a dangerous recovery and the possibility of landing damage. This probability is directly proportional to the instantaneous force on the cable, here a powerful winch is a distinct liability. In any event an overzealous pilot is going to get a lecture from the CFI... With a low powered winch, the winch driver is in charge early in the launch but as the glider steepens the climb, the power demand exceeds supply and speed control shifts to the glider pilot who now must control airspeed with pitch since the winch is at full throttle. As the glider rises still further and power demands lessen, airspeed control shifts back to the winch driver who must reduce power to prevent over speeding the glider. There are lots of ways this scenario can go badly wrong. The other area where a low powered winch can cause problems is in the initial acceleration. The German Aero Club specifies the maximum distance that a glider can use to reach flying speed to determine the minimum winch power. Specifically, under all conceivable wind, density altitude and weight conditions, a glider must reach Vr (rotation speed) in 40 meters or less - there is no minimum specified. This is a very intelligent specification. The concern driving this spec is that should a glider's wing drop to the ground before reaching flying speed, the resulting ground loop will be very ugly and quite possibly fatal for the glider pilot. These concerns and the desire to get the highest launch possible, has driven winch horsepower higher and higher in recent years. Shortening the accelerate to Vr distance has a powerful effect on the launch height achievable. Many powerful winches have shortened this to less than 20 meters. IF we were launching twin Astirs, or K21s or other heavy two seater I would concur that you would want more power. But bear in mind that the Blue weak link is easily overcome by a 200-250Hp winch. If that is the heaviest weak link specified you are wasting your time on more power. Again I agree that more initial acceleration is desirable - I HATE slow acceleration launches in my Cirrus because the chance of a wing drop is higher. TO overcome this we use gearing on the winch that increases the effective torque available. To summarize, I am advocating generous power reserves to permit the winch driver to maintain control of the launch and to insure the glider reaches flying speed before a wing can drop. Bill Daniels Generous power reserves are desirable. I am just not convinced that the use of very powerful winches imnproves safety. My experience is that an adequately powerful winch that is tractable and predictable is safe, even if there are compromises on height and initial acceleration. In our mixed vintage and glass setting it would be challenging to have a super powerful winch. My conclusion is that it is desirable to have generous power reserves and good torque for fast acceleration of the heaviest aircraft on the fleet. It is also imperative that the control be adequately calibrated so that power output can be modulated easily for all of the gliders the winch could be expected to launch. Bruce Bruce, good points all. I probably should have emphasized that with large power reserves, it becomes imperative to have extremely precise control of that power. I am in absolute agreement that there are gliders with inadequate down elevator authority to cope with high initial acceleration. Your example of a K8 is a good one. If you would allow me, I will restate your objections thusly. 'Very powerful winches with inadequate power controls, launching lighter wing loading gliders possibly with inept winch drivers/pilots is a very dangerous situation.' 'Given this situation, a less powerful winch is safer.' 'With less power, the winch driver can just hold the throttle wide open and let the glider pilot control airspeed with pitch.' I agree with this. The only objection I can raise is that the launch will necessarily be sub-optimal in that the glider could have utilized more power had it been available and thus achieved a greater height. Let me dream a little. I think we all have noticed that once in a while, things just go perfectly and the glider achieves a launch height that is perhaps 25% higher than the norm. I'd like to make this the norm rather than a fortunate accident. To achieve the control precision needed with powerful winches the winch driver and pilot need more information. Just as a tow pilot controls the glider's airspeed by reference to the tug's airspeed indicator, a winch driver should have the gliders airspeed displayed as well as the glider's acceleration in G's. The pilot should have the cable tension, measured at the weak link, displayed on the panel. I know some will say that a good winch driver can judge the glider's airspeed by watching the cable sag. If Spectra is utilized instead of heavy steel it will be as straight as a bow string and provide no information to the winch driver. My goal is that the responsibility should be divided as follows. The winch driver should control the glider's acceleration and its airspeed throughout the launch by reference to panel displays in the winch. The pilot should control the cable tension with backpressure on the stick by reference to a tensiometer on the panel while monitoring the airspeed. In this scenario, the glider's initial acceleration and airspeed are held to the precise values requested by the pilot and the tension at the weak link is a precise value that the pilot feels comfortable with. The pilot is in complete control and the launch is totally optimized and very safe. If the pilot knows from experience that in a particular glider he can manage 1.1 G and feels that under the existing conditions, 60 knots would be optimum, then 1.1G and 60 knots it shall be. If, during the launch, he feels that a cable tension of 80% of the weak link breaking strength is safe, then 80% it shall be. If the pilot is flying a K8 and knows the maximum acceleration he can manage is 0.6 G and that 54 knots is optimum given a 15 knot headwind then so it shall be. Beyond this, there is nothing that could be done operationally that would improve the launch process. Bill Daniels |
#32
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Bruce and Bill,
these were very insightful contribution to this subject. I think that nobody in his right mind would set out to purposely build an underpowered winch. I think you cannot have too much power, as long as it is controlable. The ECU's of modern big rig diesels would allow you to have a preset power setting for each glider with an available override. I remember one incident where an L-Spatz took off and as soon as he rotated, the spoilers popped out. No radio and an oblivious pilot left the winch operator no choice than to 'floor'it. We had a 360cuin V8 powerplant, which fortunately was capable to jank the Spatz up even with the spoilers open. Had this been our K-21 or Janus-C, the outcome would have certainly been different. Don't get me wrong, I don't intend to design a winch capable of converting a glider into a dragster by puling the fuselage from between the wings, but power (read torque) is a good thing here. Keep the discussion going - we have two more winter months to cover ;-) Ulrich Neumann Bruce Greeff wrote in message ... Hi Bill I respect your views but there are some differences in the way we see things he Firstly please note that I am not advocating underpowered winches. I do however maintain that power is not the most important safety issue in winch launching, and that - for our fleet where the highest wingloading is relatively modest, and the heaviest glider is a Blanik L13 - a winch with 220Hp is adequate. (maybe 250 would be better) Bill Daniels wrote: We have had several people writing that they have launched heavy glider X with a low powered winch. I have done it and so have many others, but this is still not a good idea. There are serious dangers involved. Too low power is dangerous, and we agree entirely that more power is desirable. Interestingly the most recent National Safety meeting addressed winch launching as the primary theme. There were 25 Safety Officers and at least ten Chief Flying Instructors as well as the SSSA Exco present. One thing that became apparent was that there is no optimal power winch. In particular - when launching old designs that are light, high wing with the hook at a considerable vertical displacement from the wing, there have been numerous dangerous launches where the initial acceleration exceeds the control authority on the glider. The example given was launching a Ka8 with the stick hard against the forward stop for most of the launch. Too much acceleration is as dangerous as too little. The best way to look at it is to consider power demand and supply. The winch engine should be able to supply all the power the glider demands. If the glider demands more power that is available by pulling up hard, the airspeed will decay quickly. If the pilot knows this is going to happen, he can manage it by controlling the pitch attitude carefully. If he doesn't expect it, the airspeed will decay so quickly that a very dangerous situation will develop. Agreed, and all of our pilots have to learn to control their demands on the winch before going solo. In this respect it would be safer and better to have more power for perhaps 30% of our fleet. Conversely, any piulot who relies on the generous power reserve of the winch to compensate for pulling back too hard is dangerous. I am all for the speed decay to warn the pilot. That way, when the winch falters, he will compensate automatically because he will be used to monitoring and controlling airspeed carefully. The attempt to launch gliders with a low powered winch gets into who is in control of the launch. I think it goes without saying that who controls the launch should not be in doubt. The majority view is clearly that the winch driver should be in charge. Here I differ, the pilot is always in control of his / her destiny. Our process is that the launch marshal controlls the launch process, and the winch driver and pilot must work together. A skilled winch driver is in control at all times within the parameters dictated by physics. If we have a pilot who over rotates and "bends the pole" a number of things will happen. With the exception of the Blanik with its flaps deployed the winch driver will be able to keep the glider above stall speed with full throttle. The winch driver is still in control and may decide that the probability of a maximum tension cable break is dangerously high and elect to reduce power until the pilot takes the pressure off the cable. (even if it results in a low release) If the pilot is being ham fisted the cable will probably break resulting in a dangerous recovery and the possibility of landing damage. This probability is directly proportional to the instantaneous force on the cable, here a powerful winch is a distinct liability. In any event an overzealous pilot is going to get a lecture from the CFI... With a low powered winch, the winch driver is in charge early in the launch but as the glider steepens the climb, the power demand exceeds supply and speed control shifts to the glider pilot who now must control airspeed with pitch since the winch is at full throttle. As the glider rises still further and power demands lessen, airspeed control shifts back to the winch driver who must reduce power to prevent over speeding the glider. There are lots of ways this scenario can go badly wrong. The other area where a low powered winch can cause problems is in the initial acceleration. The German Aero Club specifies the maximum distance that a glider can use to reach flying speed to determine the minimum winch power. Specifically, under all conceivable wind, density altitude and weight conditions, a glider must reach Vr (rotation speed) in 40 meters or less - there is no minimum specified. This is a very intelligent specification. The concern driving this spec is that should a glider's wing drop to the ground before reaching flying speed, the resulting ground loop will be very ugly and quite possibly fatal for the glider pilot. These concerns and the desire to get the highest launch possible, has driven winch horsepower higher and higher in recent years. Shortening the accelerate to Vr distance has a powerful effect on the launch height achievable. Many powerful winches have shortened this to less than 20 meters. IF we were launching twin Astirs, or K21s or other heavy two seater I would concur that you would want more power. But bear in mind that the Blue weak link is easily overcome by a 200-250Hp winch. If that is the heaviest weak link specified you are wasting your time on more power. Again I agree that more initial acceleration is desirable - I HATE slow acceleration launches in my Cirrus because the chance of a wing drop is higher. TO overcome this we use gearing on the winch that increases the effective torque available. To summarize, I am advocating generous power reserves to permit the winch driver to maintain control of the launch and to insure the glider reaches flying speed before a wing can drop. Bill Daniels Generous power reserves are desirable. I am just not convinced that the use of very powerful winches imnproves safety. My experience is that an adequately powerful winch that is tractable and predictable is safe, even if there are compromises on height and initial acceleration. In our mixed vintage and glass setting it would be challenging to have a super powerful winch. My conclusion is that it is desirable to have generous power reserves and good torque for fast acceleration of the heaviest aircraft on the fleet. It is also imperative that the control be adequately calibrated so that power output can be modulated easily for all of the gliders the winch could be expected to launch. Bruce |
#33
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Marc Ramsey wrote in message .com...
Martin Gregorie wrote: If you have a diesel driving through a fluid flywheel you don't need that much power: we have a Supacat with a 245 hp Deutz V8 aircooled industrial diesel and torque converter (no gearbox). This can launch an ASH-25 or just about any Nimbus. With a 15 m glider, K-21 or Grob you'd expect 1200-1400 ft on a 1000m run in calm conditions and over 2000 ft if its blowing a bit. I think the difference is that Bill is considering operating at much higher density altitudes. In the western US, there are many glider operations where summer density altitudes are in the 8000+ foot range. Marc So? Our setup: 222kW (300hp) turbocharged diesel, 6 drums, 1000m of steel cable. This winch has handled everything including a 4DM. Even a slight tailwind and a ASH25 are no real problem. Samedan, the highest airport in Europe at over 5600ft MSL, has the same winch with four drums. No problems at all. It's heaven compared to the voluminous petrol monster they had before. BTW these winches use an average of 0.4 litres of Diesel per launch. |
#34
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Marcel Duenner wrote:
So? Our setup: 222kW (300hp) turbocharged diesel, 6 drums, 1000m of steel cable. This winch has handled everything including a 4DM. Even a slight tailwind and a ASH25 are no real problem. Samedan, the highest airport in Europe at over 5600ft MSL, has the same winch with four drums. No problems at all. It's heaven compared to the voluminous petrol monster they had before. BTW these winches use an average of 0.4 litres of Diesel per launch. How much petrol per launch did the previous winch use? Is there a big price difference between the two fuels? -- ----- change "netto" to "net" to email me directly Eric Greenwell Washington State USA |
#35
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#36
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"Craig Freeman" wrote in message om... (Ulrich Neumann) wrote in message om... Bruce and Bill, these were very insightful contribution to this subject. I think that nobody in his right mind would set out to purposely build an underpowered winch. I think you cannot have too much power, as long as it is controlable. The ECU's of modern big rig diesels would allow you to have a preset power setting for each glider with an available override. True today's electronic can be programed to various power outputs. However it is not possible to do this in a way that would be useful in the winch application. At least not through the engines computer. To reprogram the engine you first have to be trained and then have access to the OEM codes. Only dealers and certified shops get these codes and then it varies engine by engine as to specific results. Also to time consuming and not able to make small enough adjustments to be useful in winch launching. However an external system such as Bill has proposed could tell the engine "give me more or give me less". Until a system such as this is built and proven there is no substitute for the human bean, er brain. I have it on "pretty good" authority that these ECU's are simple to hack or reverse engineer. Several gray market operations have already done it and offer replacement ECU's with extensive user controls accessible through a serial port from a laptop running special software. The market demand seems to be coming from the participants in tractor pull competitions. I would tend to think that the maximum power setting of the ECU would be best used as a safety limit set to , say, 10% over the expected power demand. With 3000 + foot pounds of torque available on these large diesels, a winch driver sneeze at just the wrong time might produce interesting results. If we go to a "full authority" autolaunch system, having a separate power limiting safety net seems like a good idea. You know, there is another "feel good" thing about diesels. There is a rapidly expanding supply of renewable "biodiesel" fuel whose source is vegetable oils produced domestically. Since CO2 went into growing the crop that produced the oil, releasing it back into the atmosphere results in no net increase in atmospheric CO2. With biodiesel fuel, a diesel runs better, lasts longer and sure smells better. It's a little more expensive than petroleum based diesel but at .4 liters of fuel per launch, you aren't going to use much of it. Bill Daniels |
#37
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"Craig Freeman" wrote in message om... True today's electronic can be programed to various power outputs. However it is not possible to do this in a way that would be useful in the winch application. At least not through the engines computer. To reprogram the engine you first have to be trained and then have access to the OEM codes. Only dealers and certified shops get these codes and then it varies engine by engine as to specific results. Also to time consuming and not able to make small enough adjustments to be useful in winch launching. However an external system such as Bill has proposed could tell the engine "give me more or give me less". Until a system such as this is built and proven there is no substitute for the human bean, er brain. Craig- I am a parts person at an International Trucks (Navistar) dealer. We are full service dealers for International, Cummins, Detroit Diesel, and Caterpillar engines. It is certainly possible to reprogram the ECU's of these diesels. We do it every day. Simple and easy enough for high school drop outs to do. I sell the software for reprogramming the engines. Shrink wrap stuff, just like at the computer store. That said, it would probably be possible to just replace the TPS (Throttle Position Sensor, "electronic foot pedal") with a microprocessor circuit and get the thing to do what you need. I am not a computer nerd, so I don't know the details... -Bob Korves |
#38
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"Bill Daniels" wrote in message ... demand. With 3000 + foot pounds of torque available on these large diesels, 3000+ foot pounds?? Bill, you really are talking "big"! Is that just in case a Horsa, CG-4a, or Gotha 242 shows up looking for a tow? You know, there is another "feel good" thing about diesels. There is a rapidly expanding supply of renewable "biodiesel" fuel whose source is vegetable oils produced domestically. Bill Daniels International Trucks has "Green Diesel" technology that uses biodiesel. These vehicles are out there in small numbers in the field already throughout the U. S. and seem to work just fine. The exhaust smells like french fries. Off topic, perhaps, but a while back a prototype truck was in our dealership that had no camshaft. The valves were electronically controlled and hydraulically actuated, the same way that injectors are controlled on many newer engines. This system allows unlimited options of valve timing and different schemes of timing at different loads, running the engine on less than all cylinders, etc. The valves also had no springs -- they were both opened and closed hydraulically. -Bob Korves |
#39
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Have you ever smelt a diesel running on used vegetable oil?
It's just like standing in the local Fish and Chip shop! Ian "Bill Daniels" wrote in message ... "Craig Freeman" wrote in message om... (Ulrich Neumann) wrote in message om... Bruce and Bill, these were very insightful contribution to this subject. I think that nobody in his right mind would set out to purposely build an underpowered winch. I think you cannot have too much power, as long as it is controlable. The ECU's of modern big rig diesels would allow you to have a preset power setting for each glider with an available override. True today's electronic can be programed to various power outputs. However it is not possible to do this in a way that would be useful in the winch application. At least not through the engines computer. To reprogram the engine you first have to be trained and then have access to the OEM codes. Only dealers and certified shops get these codes and then it varies engine by engine as to specific results. Also to time consuming and not able to make small enough adjustments to be useful in winch launching. However an external system such as Bill has proposed could tell the engine "give me more or give me less". Until a system such as this is built and proven there is no substitute for the human bean, er brain. I have it on "pretty good" authority that these ECU's are simple to hack or reverse engineer. Several gray market operations have already done it and offer replacement ECU's with extensive user controls accessible through a serial port from a laptop running special software. The market demand seems to be coming from the participants in tractor pull competitions. I would tend to think that the maximum power setting of the ECU would be best used as a safety limit set to , say, 10% over the expected power demand. With 3000 + foot pounds of torque available on these large diesels, a winch driver sneeze at just the wrong time might produce interesting results. If we go to a "full authority" autolaunch system, having a separate power limiting safety net seems like a good idea. You know, there is another "feel good" thing about diesels. There is a rapidly expanding supply of renewable "biodiesel" fuel whose source is vegetable oils produced domestically. Since CO2 went into growing the crop that produced the oil, releasing it back into the atmosphere results in no net increase in atmospheric CO2. With biodiesel fuel, a diesel runs better, lasts longer and sure smells better. It's a little more expensive than petroleum based diesel but at .4 liters of fuel per launch, you aren't going to use much of it. Bill Daniels |
#40
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Bill Daniels wrote:
"Craig Freeman" wrote in message om... (Ulrich Neumann) wrote in message om... Bruce and Bill, these were very insightful contribution to this subject. I think that nobody in his right mind would set out to purposely build an underpowered winch. I think you cannot have too much power, as long as it is controlable. The ECU's of modern big rig diesels would allow you to have a preset power setting for each glider with an available override. True today's electronic can be programed to various power outputs. However it is not possible to do this in a way that would be useful in the winch application. At least not through the engines computer. To reprogram the engine you first have to be trained and then have access to the OEM codes. Only dealers and certified shops get these codes and then it varies engine by engine as to specific results. Also to time consuming and not able to make small enough adjustments to be useful in winch launching. However an external system such as Bill has proposed could tell the engine "give me more or give me less". Until a system such as this is built and proven there is no substitute for the human bean, er brain. I have it on "pretty good" authority that these ECU's are simple to hack or reverse engineer. Several gray market operations have already done it and offer replacement ECU's with extensive user controls accessible through a serial port from a laptop running special software. The market demand seems to be coming from the participants in tractor pull competitions. I would tend to think that the maximum power setting of the ECU would be best used as a safety limit set to , say, 10% over the expected power demand. With 3000 + foot pounds of torque available on these large diesels, a winch driver sneeze at just the wrong time might produce interesting results. If we go to a "full authority" autolaunch system, having a separate power limiting safety net seems like a good idea. You know, there is another "feel good" thing about diesels. There is a rapidly expanding supply of renewable "biodiesel" fuel whose source is vegetable oils produced domestically. Since CO2 went into growing the crop that produced the oil, releasing it back into the atmosphere results in no net increase in atmospheric CO2. With biodiesel fuel, a diesel runs better, lasts longer and sure smells better. It's a little more expensive than petroleum based diesel but at .4 liters of fuel per launch, you aren't going to use much of it. Bill Daniels Bill, I know one of the sources of raw material for biodiesel is useddeep-frier grease. What a great way to get teenagers into the sport. They follow the smell of french fries and find gliders instead! Cheers, Shawn |
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