IAS -> TAS air density model

[Alberich]

Hello,
this is my first posting here and I hope this is the right place to post and the subject was not discussed already. Searching the forums did not help me finding the desired information though.

I am interested in how IL2 1946 models the atmosphere, especially how the game derives TAS. Is, for example, air temperature (and its effect on air density) taken into consideration?

Right now I use the '2%-rule of thumb' to derive my TAS (from IAS and altitude above sealevel) which says that TAS increases by 2% every 300 meters of altitude. Well, that is just a rule of thumb...
When dropping bombs with the Pe-2 (OPB-1 bombsight, no bombsight automation) it looks like the error made by this rule of thumb leads to quite incorrect bombsight-angles.
Some information on this topic would be greatly appreciated!

Alberich