All helicopters and aircraft in A3 have a "Take controls" option for the co-pilot/gunner(when there's no (alive) pilot), that allows him to control the aircraft's movement. This includes the attack chopper Ah-99 Blackfoot. However, the gunner position of the Mi-48 Kajman (both black and camo version) doesn't have a Take controls option.
EDIT: Apparently the developers did not model flight controls for the copilot's seat and this is why this option is not available.
However, for the sake of balance(see the above and below text) it should be added, it is a fictional helicopter after all.
This option is pretty important if the pilot of the heli dies/disconnects, or if you want to fly solo. (Since using manual fire as a pilot, doesn't let you lock your weapon systems onto targets, if you don't have an AI as a gunner, made a ticket about it: http://feedback.arma3.com/view.php?id=9961)