In a default MH-6 or AH-6 pull about 80% Torque, lower the nose and let the aircraft accelerate. Let the airspeed stabilize and once it does roll the aircraft to the right or left and start pulling aft cyclic to tighten the turn. You notice you can hear the NR start to droop and if you persist you'll lose enough NR that the low Rotor RPM horn goes off and the aircraft begins to wallow. This is in fact the opposite of what should happen. Upon entering a high G turn in a helicopter the NR will if anything start to climb as the force of the tightening turn will cause the rotor RPM to increase. In a real helicopter one way to recover rotor RPM is to lower collective and either flare the aircraft slightly or enter a high g turn which will increase rotor RPM. In addition if the throttle is rolled off and the rotor is free wheeling you actually may have to add some collective to keep the rotor from overspeeding. However in Arma 3 the opposite occurs and even if you lower collective fully before rolling the aircraft and pulling aft cyclic the RPM still droops which is incorrect and should really be addressed.

In addition if you lower collective sharply in the Mohawk the NR overspeeds and if you raise it sharply it often droops. The aircraft simply doesn't react like this fortunately with a few tweaks to the blade inertia I expect this too can be corrected.

Conditions where the RPM will droop include but are not limited to when power required is greater than power available as in that case the RPM will drop as the rotor starts to cone and unless the collective is lowered the low rotor horn will come on and the aircraft will start to wallow, sink and if sufficient altitude isn't available crash. One example of this would be approaching a high altitude LZ or one downwind or at or near max gross weight. Often in these situations the power available is not sufficient to maintain a hover out of ground effect or even sometimes in ground effect. Often the pilot doesn't realize until he's out of translational lift. In very powerful aircraft like a chinook this is less of a problem where as in a R22 or a heavily loaded 206 it will undoubtedly result in a crash. Another example would be operating a max gross take off weight and trying to climb to high altitude eventually the amount of power required will exceed the power available and the blade RPM will start to droop. Again the only solution is to lower the power. If you require any additional info or clarification please let me know. In addition I'd be happy to discuss the parameters to adjust and flight test should you require it.

Also should you wish to confirm what I'm saying is correct you can check Transport Canada TP 2552 Helicopter Theory of Flight from April of 1980. As well as "The Art and Science of flying helicopters" by Shawn Coyle or "Principles of Helicopter Flight" by W.J. Wagtendonk.