A helicopter blade assembly for permitting rapid forward flight in a helicopter having separate means for providing a forward impetus. The assembly has a set of rotatable blades attached to a substantially vertical mast. These blades slope downward near to their distal ends, thereby creating an inverted disk virtual air foil when the blades are rapidly rotated by the mast. In a preferred embodiment the camber of the blades and, therefore, the shape of the virtual air foil is controllable.