Concerning the validity of the C++ modelling, I just remembered we did a comparison of the C++ compressibility modelling and what was implemented in IL2 at the time (4.09m). As can be seen there is good agreement in the models as long as the speed does not start to reach into the compressibility range. The figure also shows that the lag between the compressibility and non-compressibility models following the pullout. As can be seen, the non-compressibility model means the P-51 will end up higher than it should. I think the effects should be less here in CloD though, since the Me109E and Spitfire Mk1 were not as fast, not as powerful and had a higher Cdo/weight factor so it took them longer to reach compressibility speeds.
I do not master devicelink so Wurkeri helped me with the IL2 data which he sent me in Excel format so I could get that into the graph. One graph shows the raw data (red) and the other (black) where I translated the data so as to be aligned with the C++ data. I think this figure gives a good illustration of the problem: The aircraft should not in a dive speed up to a "point" but rather have the top truncated by compressibility effetcs.
Doggles: If you do run a test in CloD and can get the Spitfire or Me109 data into an Excel sheet then that would be good because then I can include that together with the C++ results. However, If it is difficult to get continuous data out of CloD then I think a simple dive test down to 2.5 Km alt and reading off the speed there ( or a number of dives and averaging the result would be even better) could do to begin with to get a ballpark estimate.
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