I've downloaded and installed EECHAllMods, apache-cockpit-1.0 and eechsetup1.10.2 from EECH Central (as described in their install guide), now the game works without a problem, except for one thing:
When flying the Havoc, my framerate is low when i'm in the cockpit, but when i turn the cockpit off (ctrl-F1) or use external views everything is OK.
Same goes for the Apache cockpit which is used when you fly non-flyable US helicopters (Blackhawk, Kiowa, etc.). Also, the gauges in the Havoc have no dials.
The Commanche, Hokum and EECH Central Apache cockpit all work fine.
Now, I have powerful PC which runs newer games without problems. So I find it wierd that two cockpits cause a drastic fall in the framerate when the rest of the game works excellently.
While this isn't a major problem (I just use ctrl-F1 and turn the cockpit off), I'm really interested as to why it is happening.
Has anyone expirienced similar problems?