Cristiano

No, the calculations are good. Just a desgn decision at the time, mostly from historical usage. There's no way any of this will be changed now -- too late, too many dependencies. Sorry. No problem. :) Is there any way to read the exact values? Cristiano

This is now done and available in the interim test version 3.507, see top announcement above. Could you try it and let me know if it works as you'd expect, please? The calculations seem good (also when the a/c is placed below the lowest temperature sample or above the highest and also when there is just one temperature sample). Thank you very much. I think you could be interested in a strangeness (a bug?) in the structure _NewTemp. When a temperature sample is negative, the member Alt is wrong (because it's an unsigned short). Try, for example, to place the a/c at KBWC (which is below the sea level) using the weather theme "Building Storms". You should see the lowest temperature sample = 214885 ft and the second sample = 4134 ft. A bit strange... :-) I think a float type for Alt would be the right choice. For the other members (Day, DayNightVar and DewPoint) why don't you use something like _NewTemp.DewPoint = dew_point * 256 (like with the new offset 0E8E)? Cristiano

Good! Then, have a nice holiday! :-) No, sorry, It represents many hundreds of hours of hacking through disassembled parts of FS, and has to be repeated for each FS release -- even the 9.1 patch needed further hacking.[...] No problem, we have your great UIPC. :) Bye bye Cristiano

Ooops! Sorry, by mistake (in my rush before going on holiday) I edited your message instead of adding a reply! Many apologies. I've posted the reply to your now lost message below. Pete

That could be interesting. I'll do more experiments. Nothing but what I said. :) I wrote a "panel" (no needles, just numbers) to see many parameters usually unavailable in the real planes. With my panel, I seen strange values for some parameters (TAT, dynamic density and pressure) and I seen that the air density doesn't care about the humidity. I just want to fix the strange parameters. Unfortunately, few parameters seem unavailable with FSUIPC (like CG_AFT_LIMIT and CG_FWD_LIMIT at the offsets 2F00 and 2F08), but it's not a problem, I'll use the FS panel lookup_var() function). With my fixes I hope to improve the simulation realism. Regards Cristiano

It works! :-) Writing, for example, a density 10 times bigger, the a/c (MD-11) has many problems to reach Vr (because of the incredibly big drag). It seems strange to me that the engines are not affected by the air density (while I know that the thrust should change with the density at least when the a/c is moving, but this could be a "bug" of the .air file). I use a Windows timer to call FSUIPC_Write with the parameter "Elapse" (the time-out value) = 1 ms and it seems to work fine without any noticeable effect on FS fps or fluctuation. Also 50 ms seem good. Do you have a sort of flag which can tell me when it's the time to write my calculated density? Regards Cristiano

Finally, I'm able to say that FS2004 gives the air density without any correction for the humidity (this leads to a density altitude which is lower than the expected and, in the real life, it could be a problem). Now that I have the corrected dry air density, I'd like to use it in FS. Do you know whether it is possible to write "my" density so that FS use it in all its calculations? Regards Cristiano

No, I still haven't checked it, but I'm not expecting that it is linear. I think it is linear between two samples (but I can be wrong). Your dew point seems to work fine. The density in 28C0 is about 3 or 4% smaller than I expected even with the correction for the vapor pressure. I need to investigate, but now it's time to do some sleep. :) Thank you very much for your valuable support Cristiano

Currently I'm interpolating the temperature read in the NewTemp structure, but I get a different temperature w.r.t. the OAT (as in 0E8C). I guess I get different OAT's because of the rounded values of altitude and temperature in that structure. But if you can interpolate the dew point using the accurate sample values, I guess that the interpolated dew point will be good. Do you confirm that you can read the accurate values of the altitude and dew point samples? I don't think it will be a problem. If you are able to get an accurate dew point at the a/c altitude, then that frequence will be good. Regards Cristiano

Yes, the dew point at the aircraft, exactly like the OAT in 0E8C; 1/256th of a degree would be very good. Thank you very much Cristiano

I'd like to have access to the accurate values of the dew point because I need to calculate the water vapor pressure (needed for the dry air density). But if it's not possible... :cry: Regards Cristiano

Hi Pete, thanks for the prompt reply, I just know how to calculate the dynamic parameters and the air density, but I don't know how FS2004 calculates them. According to my calculations, the dynamic values are inconsistent with the static values and with the dew point (from which I calculate the air and the dry air density). For that reason I asked whether the values in the structure NewTemp exactly match the FS values. I totally agree. I myself interpolate those values to calculate them at the plane altitude. My term "layer" is simply wrong. I now read your "later" Is there any way to read the exact values? Thank you Cristiano

1) I don't know much how FSUIPC works, so I'd like to know whether these offsets 0x11D0 (total air temperature) 0x30D8 (dynamic pressure) 0x28C0 (ambient air density) 0x28C8 (ambient air pressure) are directly calculated by FS2004 or by FSUIPC, because the dynamic parameters seem not in full agreement with the correction for the mach number. Also, the air density seems different from the expected one. 2) The structure NewTemp (in the header NewWeather.h) is formed by integer numbers (c short data type). I read, for example, that the second temperature layer begins from 12 meters and that the temperature is 25 °C. I'd like to know whether the altitude is exactly 12 meters and the temperature is exactly 25 °C. Thanks and sorry for my English :oops: Cristiano