Helicopter armed with LRM/Arrow IV(if copter big enough), and waiting some target to be Tagged to unleashed a volley of missile from anywhere.
Helicopter (who are part of the VTOL familly) are mobile support unit (fire support, recon), trading armor for more mobility.
They are easily shot down by AA since they are a lot slower than Aircraft, but they can get behind cover, pop over it, unleash its ordnances, then hide back. Not a frontline unit, that's official, but in the hands of a good player, they can be dangerous.