Compressibility modelling

[Holtzauge]

Yes, getting at least some modelling of subsonic compressibility based on the Prandtl factor could have been a way to go to get at least something in there even though that would have affect all airplanes the same but if you look at wind tunnel data and results from flight tests then the different aircraft have significantly different drag characteristics in the M=0.5-0.85 range with some like the P-51 and Spitfire being better than others like the late war Me109's which suffered from an earlier onset of drag creep.

This report has some nice info on the P-51 and was one of the sources I used as input to the drag modelling.

http://ntrs.nasa.gov/search.jsp?R=19...20the%2520drag

In the IL2/C++ P-51 20 degree dive comparison the Cdo goes up from the low Mach Cdo of around 0.018 to about 0.034 at M=0.75 which is hardly negligible and explains the truncating effect on speed and why the Mach never goes higher in the C++ simulation. Since this increase in Cdo seems not to have been present in IL2 the speed increases unabated to 960 Km/h which seems a bit on the high side

Pity that this was not included in CloD when a lot of work seems to have been done in other areas such as damage modelling and improved graphics etc. Being familiar with IL2 I was hoping that CloD would also take a significant step towards better FM as well. If I had to choose between better graphics and better flight models then it would have been the latter no contest. On the other hand from a commercial perspective I guess better graphics wins the day over hard core simmers fancies so I can understand the priorities taken from that perspective.