Hi, and welcome to the Outerra community!
The Apache flight dynamics model (FDM) which is currently in Outerra is very old, and kind of a hack. You should still be able to fly it, however for some reason throttle and collective are still swapped. I thought we fixed that issue, but apparently not. By default, PageUp and PageDown keys should be Throttle, however they will actually act as collective control, because of an issue with the FDM. What is happening is that the engine isn't a turbine in this version, it is actually a fixed horsepower output electric motor, and the rotor has an RPM governor, both are hack. I have a new FDM working with a turboshaft engine and better flight characteristics, however it hasn't been released yet. I do apologize for this, it does need to be fixed. I've been working with another community member KW71 to improve the AH-64, you can visit our thread here:
http://forum.outerra.com/index.php?topic=3253.0I haven't had much time lately due to my job, but as soon as I do it should only take a weeks work to finish the FDM and the rest of the code, and we plan on releasing an alpha version at that point. If I have some time in the next couple weeks to work on the FDM, maybe I'll release a patch for the current Apache to demonstrate the new flight model.
Looks like you are into game development! Just let us know if you need any help getting started. There are a ton of resources here, although the information is fragmented throughout many threads. At some point I hope to put together some structured tutorials for newcomers who wish to import models and build mods, but it is surprisingly straight forward.
Again, welcome to the community!
Regards,
Uriah