Ceeeb, as you point out, Arma II does simulate autorotation (Whether intentionally or not intentionally), but that is Arma II. If I'm not mistaken, Arma III uses a different flight model. If you attempt this maneuver in Arma III, you will find the flight model is not sufficient to simulate it.

NodUnit, I think I remember one of the developers talk about how they weren't focusing on the vehicles too heavily early on in development which makes sense. Who knows if they are going to make changes to the flight model, etc.

Well, the first thing I did before I posted was specifically search for the term "autorotation" with no results. Unfortunately, this ticket is a duplicate. However, in the duplicate ticket (0006502), the moderator wrote that you could autorotate by holding the "collective lower" key. I have experimented and tried this with no change. Maybe I am missing something here?