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LX-Polar Program
On Sep 22, 2:08*pm, wrote:
On Sep 21, 8:49 pm, GM wrote: Hi all, does anybody have a usable, step-by-step decription of the LX-Polar program? The instructions that came with the manual of my LX-20-2000 are pretty useless. I have a polar curve for my glider and I am trying to calculate the factors a, b and c used to define the polar. Thanks, Uli Neumann Uli, Basically you just have to invoke the program. *It expects input in km/ hr and m/s, so if you are using American units you'll have to convert them first. *I had a devil of a time figuring this out with the LX5000 in our club 304C; the values for the coefficients didn't make sense. Finally I determined that they output the sink rate in m/s when fed the speed in 100s of km/hr (hectakilometers?). *9B's comments about wing loading, actual experienced polar, etc. all apply too Armed with that information I found that the 304 entry programmed into the unit must be the old Glasfluegel 304 from the 1970's with about a 36:1 glide ratio. *The 304C is closer to 42:1 and of course has a different wing loading (especially with me in it), so the glideslope info the unit spits out is not very useful for flying fast. *It was very disappointing to arrive at the finish line about 1000' high after my PDA cable went inop the last day at R5N, causing me to have to navigate the old fashioned way. Now that I know what the coefficients are, all I have to do is convince the unit to use them! Matt (sometimes AI) Hi all, thanks to all that responded. The problem was simply in the installation of LXe on my Laptop. For some reason or another, I could not insert the measured data pairs into the coordinate system. I wiped LXe from the computer , downloaded the latest version from the LX-Nav site and re-installed it. Now it works like a charm. I also got a short version step-by-step from Dr. Michael Seischab at LX-Navigation. Here is how to use LX-Polar: 1 if you have a polar curve for your glider (measured or calculated), make sure the speed is in km/h and the sink is in m/s 2- open LX-Polar 3- under tools, pick 'Insert'. The pointer changes from the arrow to a hand 4 - move the hand over the coordinate system to the X-Y position. The exact X-Y position is shown below the coordinate system 5- left-click to insert the point 6- repeat for each point beginning at # 3 7- if you misplaced a point, use the move function to correct the placement or the delete function to erase a point. 8- enter as many points as you like. 9- when done, hit F9 or select 'calcuate' from the Tools drop-down menue. The result are the three factors a, b and c displayed in the coordiante system and on the left side. The program also shows the max. L/D at what speed and sink rate. On my LX-20, I can enter these three points under the User-Polar. I will have to experiment a bit with this new polar before setting out on that record breaking flight ;-) Again, many thanks for all the responses. Uli Libelle 'GM' |
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