Density Altitude, how to calculate?

[Guest Karl R Pettersen]

HiI'm working on a TAS 1000 gauge, and have troubles how to make myself a decent density altitude conversion by the available parameters in FS9. As far as I know, only pressure altitude and various temperatures are available, certain online calculators needed dew point as well to generate this.If dewpoint is missing, is it possible to calculate density altitude in a "worst case scenario", using outside air temperature as a replacement for dew point? Is this even a sensible thing to do, and if it is, how to do it? I have no ideas on this one, all I'm stuck with is conversion tables which I found rather hard to setup in xml.The best thing would have been an actual parameter describing density altitude, but I haven't found anything like this yet :-Anyone?

[Guest bartels]

Have you checed the "reference" source :http://williams.best.vwh.net/avform.htm#AltimetryFrom Aviation Formulary V1.41:The standard lapse rate is T_r= 0.0065C/m = .0019812C/ft below the tropopause h_Tr= 11.0km= 36089.24ftRelationship of pressure and density altitude: D_Alt=P_alt+(T_s/T_r)*(1.-(T_s/T)^0.2349690) (Standard temp T_s and actual temp T in Kelvin)An approximate, but fairly accurate formula is: D_Alt=P_Alt+118.6*(T-T_s) where T and T_s may (both) be either Celsius or KelvinArne Bartels

[Guest Karl R Pettersen]

Thanks, that seems to work very nicely. Using the approximate version, I get slightly higher results than by using other calculators, but it doesn't matter too much.Can FS9's Ambient Temperature (OAT) be used as a safe replacement for Static Air Temperature (SAT)? I guess SAT is the caclulated OAT based on total air temperature (TAT). Any ideas?That link was a goldmine - everyone grab it - NOW :)

[Varmint007 2]

>That link was a goldmine - everyone grab it - NOW :)Um, that site ROCKS! There's enough stuff there to make me seriously consider some features I was just going to blow off:)--Jon