I've made some tests with latest build and noticed issue with ceiling for several helicopters.
As I remember, when I've added flight model #2, helicopters ceiling in perfect conditions (almost empty fuel tank, no overtorque, positive forward speed) was pretty close to real performance values.
However, after your changes I was able to climb on AH-64D over 30 000 ft, and over 10 000 m on Mi-28.
Do you have time and interest to revise your air density changes? It may be something else - like dry weight calculation, lift forces issues etc. but I haven't checked latest commits yet so can't provide any clue.

Attached Files Untitled-2.jpgUntitled-1.jpg
Last edited by thealx; 02/14/20 12:08 PM.