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#21
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Pirker Final Glide Theory
If you have lost height in a sink zone, your speed will need to be Lower
AFTER the sink zone. What you do in the sink is up to you (I suppose speed up.) At 12:09 12 February 2013, Naviter Info wrote: True. But while you're in sink you need to speed up. At least until you are flying the optimal speed for MC=0 for that sink. The AutoMC suggests you to slow down which is not ok any way you look at it. Andrej Kolar -- glider pilots use http://www.Naviter.com |
#22
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Pirker Final Glide Theory
On Tuesday, February 12, 2013 12:09:20 PM UTC, Naviter Info wrote:
True. But while you're in sink you need to speed up. At least until you are flying the optimal speed for MC=0 for that sink. The AutoMC suggests you to slow down which is not ok any way you look at it. Andrej Kolar -- glider pilots use http://www.Naviter.com I have been looking at it differently. For an area of strong sink the appropriate airspeed at the optimum MC0 setting for prioritising getting through sink with minimum height loss (rather than maximising XC speed) may well be higher than the optimum speed for cruising in still air at a positive MC setting. For example if, when cruising at MC3kts in still air, one encounters sink of anything greater than 3kts then MC0 will command a higher speed. So, if I encounter strong sink at an altitude low enough that I am concerned about dropping below a sensible operating band, I wind the MC back to zero (or small positive if final gliding into a headwind) temporarily. That is the one situation that I actually pay close attention to the speed command which will be telling me to speed up rather than slow down. In the case of a Required MC advisory reading, the calculation will presumably be related to optimising a final glide and it would be dropping the advised MC gradually as the reserve is eaten up, rather than winding straight back to zero as I do, so it is even more likely that the speed command would call for an increase in airspeed in strong sink rather than a decrease. John Galloway |
#23
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Pirker Final Glide Theory
At 14:25 12 February 2013, Peter Higgs wrote:
If you have lost height in a sink zone, your speed will need to be Lowe AFTER the sink zone. What you do in the sink is up to you (I suppose speed up.) At 12:09 12 February 2013, Naviter Info wrote: True. But while you're in sink you need to speed up. At least until yo are flying the optimal speed for MC=0 for that sink. The AutoMC suggests yo to slow down which is not ok any way you look at it. Andrej Kolar -- glider pilots use http://www.Naviter.com Either you're wrong or we have a different interpretation of what we mean by auto MC. The theory we are talking about (be it Pirker, Stocker or whoever), calculates a McCready setting that will give you the optimum glide path to get in, given either "dead air" or an averaged amount of lift and sink to fly through. Auto MC as I understand the term simply calculates that notional MC setting for you- it doesn't substitute for the MC ring, flight director, whatever you use, just tells you where to set it (or possibly effectively sets it for you). If you hit sink, the Auto MC value will go down, as you've dropped below the predicted glide path. If you aren't expecting to go through any further lift to put you back up again, then the correct speed to fly will be the speed commanded _for the sink rate you are in_, at the new McCready setting. This may or may not be faster than you were going before you hit the sink- either way it's the optimum speed. The only time you will fly at the MC=0 speed through the sink will be if the calculation, based on height and distance, says you can just reach your goal at MC=0; I'd suggest if that is the case then zero is indeed the best setting unless you are confident of finding another thermal and therefore aren't on final glide any more. It's still the MC speed for the sink you are in, so may still be fast. In the extreme case, if the auto MC reading winds down to zero, but you ignore it and continue to fly on a high MC setting you will definitely put yourself below glide path. Of course if you are still confident of flying through lift before reaching the goal, by all means keep the speed on. As I said, it's a judgement call. |
#24
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Pirker Final Glide Theory
My point of view on how AutoMC is actually working on LK.
1. Computer tell you that you can make it to the finish from the current position and altitude, wind considered, eventually considering also your current IAS, as an extra altitude if you pull up. This last extra altitude is optional and by default disabled, to leave some margins. 2. Computer tell you that you shall arrive 0 meters (at worst) over the desired destination's altitude with a certain MC setting, say 1.2 (I use m/s). It considers ballast. And if you dump ballast and it takes 3 minutes to do it, during those 3 minutes it will shift the polar for wing loading, adjusting all parameters. This is the same as in xcsoar . 3. You set the desired MC on your speed to fly instrument, or this value is sent automatically to it eventually, and you start following the pullup-pushdown commands seconding the airmass you travel in. 4. If the airmass is equally distributed in sinks and lift, you will be more or less flying at the desired MC. 5. If unfortunately you meet a large sink area, you will be commanded to speed up of course, following the STF indicator on the vario, which is still relative to the desired MC. 6. After some time, your average airspeed will not be anymore the one relative to the original MC, and of course the glidepath and the arrival altitude will change, even drastically, to a worst prediction. 7. In LK we use eMC, Equivalent MC , telling you what is the real MC you are flying it, no matter what you think you are doing. This eMC (widely used by paragliders, who cannot play with their instruments too much, not to mention hangglider pilots) can also be assigned automatically to MC, thus resulting in an accurate prediction based on what you are actually doing, concentrated on the airmass and not on the instrument. In still air, if you fly at MC 2 following the speed to fly indicator on your vario, the eMC will read 2, precisely. In sink air, if you try to fly at MC 1.2 but it has been some time since you have been speeding up to pass a neverending sink area, you may read eMC 3 ! 8. You decide what to do. Computer tell you what happen if you start flying again at the proper STF relative to desired MC 1.2, what happen if you keep flying like you do, at a real MC 3, and what if you slow down to MC 0. You want to make it over the finish, not below. Pilot can judge if he can speed up, slow down, or stop circling as soon as possible. No computer can estimate an airmass 2 km away, guessing if it is sinking or raising air. What we can do, is give clear informations about different scenarios, and the Equivalent MC helps a lot on this, because otherwise - like it currently happen on most flight computers, you still keep reading MC set to 1.2, while your arrival altitude gets lower and lower, and you have no clue on what you are actually doing. If you fly using MC, you ought to know what MC you are really flying with, no matter what you hope to have been using so far. EqMC stand to MC like CurrentGlide Ratio stand to Required Glide Ratio to get to a destination. The difference is that the latter does not consider wind, ballast, extra speed. paolo "Richard Brisbourne" wrote in message ... At 14:25 12 February 2013, Peter Higgs wrote: If you have lost height in a sink zone, your speed will need to be Lowe AFTER the sink zone. What you do in the sink is up to you (I suppose speed up.) At 12:09 12 February 2013, Naviter Info wrote: True. But while you're in sink you need to speed up. At least until yo are flying the optimal speed for MC=0 for that sink. The AutoMC suggests yo to slow down which is not ok any way you look at it. Andrej Kolar -- glider pilots use http://www.Naviter.com Either you're wrong or we have a different interpretation of what we mean by auto MC. The theory we are talking about (be it Pirker, Stocker or whoever), calculates a McCready setting that will give you the optimum glide path to get in, given either "dead air" or an averaged amount of lift and sink to fly through. Auto MC as I understand the term simply calculates that notional MC setting for you- it doesn't substitute for the MC ring, flight director, whatever you use, just tells you where to set it (or possibly effectively sets it for you). If you hit sink, the Auto MC value will go down, as you've dropped below the predicted glide path. If you aren't expecting to go through any further lift to put you back up again, then the correct speed to fly will be the speed commanded _for the sink rate you are in_, at the new McCready setting. This may or may not be faster than you were going before you hit the sink- either way it's the optimum speed. The only time you will fly at the MC=0 speed through the sink will be if the calculation, based on height and distance, says you can just reach your goal at MC=0; I'd suggest if that is the case then zero is indeed the best setting unless you are confident of finding another thermal and therefore aren't on final glide any more. It's still the MC speed for the sink you are in, so may still be fast. In the extreme case, if the auto MC reading winds down to zero, but you ignore it and continue to fly on a high MC setting you will definitely put yourself below glide path. Of course if you are still confident of flying through lift before reaching the goal, by all means keep the speed on. As I said, it's a judgement call. |
#25
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Pirker Final Glide Theory
On Monday, January 14, 2013 10:19:27 AM UTC-5, wrote:
Does anyone have a link to, or a copy of, an English language paper or explanation about Dr Herbert Pirker's final glide theory? I can't even locate one in German via Google. I can find snippets about it relating to implementation on StrePla in 2006vand I understand that a couple of the NavBoxes on LX 8000/9000 relate to this. http://www.strepla.de/StrePla4/engli...t_Winter05.htm Thanks, John Galloway John: send me your email by responding to |
#26
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Pirker Final Glide Theory
On Tuesday, February 12, 2013 11:19:06 AM UTC-5, Richard Brisbourne wrote:
At 14:25 12 February 2013, Peter Higgs wrote: If you have lost height in a sink zone, your speed will need to be Lowe AFTER the sink zone. What you do in the sink is up to you (I suppose speed up.) At 12:09 12 February 2013, Naviter Info wrote: True. But while you're in sink you need to speed up. At least until yo are flying the optimal speed for MC=0 for that sink. The AutoMC suggests yo to slow down which is not ok any way you look at it. Andrej Kolar -- glider pilots use http://www.Naviter.com Either you're wrong or we have a different interpretation of what we mean by auto MC. The theory we are talking about (be it Pirker, Stocker or whoever), calculates a McCready setting that will give you the optimum glide path to get in, given either "dead air" or an averaged amount of lift and sink to fly through. Auto MC as I understand the term simply calculates that notional MC setting for you- it doesn't substitute for the MC ring, flight director, whatever you use, just tells you where to set it (or possibly effectively sets it for you). If you hit sink, the Auto MC value will go down, as you've dropped below the predicted glide path. If you aren't expecting to go through any further lift to put you back up again, then the correct speed to fly will be the speed commanded _for the sink rate you are in_, at the new McCready setting. This may or may not be faster than you were going before you hit the sink- either way it's the optimum speed. The only time you will fly at the MC=0 speed through the sink will be if the calculation, based on height and distance, says you can just reach your goal at MC=0; I'd suggest if that is the case then zero is indeed the best setting unless you are confident of finding another thermal and therefore aren't on final glide any more. It's still the MC speed for the sink you are in, so may still be fast. In the extreme case, if the auto MC reading winds down to zero, but you ignore it and continue to fly on a high MC setting you will definitely put yourself below glide path. Of course if you are still confident of flying through lift before reaching the goal, by all means keep the speed on. As I said, it's a judgement call. Agree 100%. You can fly yourself into the ground before reaching your goal.. If you are really on final glide, you, by definition, are not going to stop and thermal. That, is final glide, by definition. If you are flying a MC value of four and fall below glide path, auto MC may tell you to slow down just enough to make your goal, at a lesser MC value. Auto MC continues to give you the speed to fly in sink. Auto MC really just resets the equation such that you can make it to goal without stopping to thermal. To make a point in argument, it is often helpful to push the situation to extremes to test the validity of arguments. If, for example, you are flying a MC value of 10 and you hit sink, your computer will tell you to speed up. Better judgement would be to reset MC value to a value of 3. Doing so gives you the added altitude for computations for making the final glide home. The computer will still give you speed to fly signals while flying through sink as well as through lift. If you are already flying a McCready of 0, then you are no longer on final glide if you hit sink and fall below glide path to make the goal home. |
#27
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Pirker Final Glide Theory
On Monday, February 11, 2013 5:39:29 PM UTC-8, Dave Nadler wrote:
On Monday, February 11, 2013 12:56:53 PM UTC-5, Richard Brisbourne wrote: The Stocker calculator as described by Reichmann (with instructions on how to make one) was substantially more complex. From memory you had a transparent disc with altitude spirals in one hemisphere and in the other hemisphere one set of curves corresponding to wind components and an intersecting set of curves corresponding to McReady readings. The latter set of curves depended on the polar of the glider. This disc was mounted on a map with the centre at the goal point and it could be rotated about that point. Above the disc was a linear cursor, also transparent marked with distances, rotated about the disc centre. To read the calculator, you rotated the disc so that the spiral corresponding to your altitude lay over your current position on the map. You then rotated the cursor so that the line also lay over that point; the other end of the cursor intersected the wind and McReady spirals; the correct setting for the wind could then be read off. Yep - First commercial gliding product I did was a version of this calculator, sold by Cambridge Aero in the early 80s (maybe late 70s). Still have a few in the basement I think ! Worked well but it was too large for USA sectionals and LDs of modern gliders. Anybody out there still have one ? I think Chip Bearden needs one. See ya, Dave "YO electric" I have one for a Libelle H-301 |
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