Hovering in a Helicopter is affected by gravity at any given point.
Flying upside down in a helicopter would increase the speed at which it was falling to the ground.

In the A3 Alpha, the helicopter falls at the same speed upside-down as it would the correct way up.correct me if im wrong but the helicopter should be falling faster upside-down as the Rotor Blade(s) add more force, proppeling the Helicopter further to the floor.The helicopter would also lose force due to the blade facing the ground which also makes the helicopter fall faster.