Does angular momentum contributes in lifting a helicopter? I want to know whether it is possible to make a helicopter with blades that rotate counter-clockwise (CCW) seen from below. I have difficulty understanding the angular momentum in this situation.
As we may see in the picture below, the rotor rotates clockwise (CW) seen from the pilot seat look up. So far, the rotations I have seen. To extend this question: is it possible for a single engine airplane to have propeller rotating counter-clockwise (CCW) seen from the rear, looking in the direction of the nose (as so far, what I found is that every single engine airplane is rotating CW). As we know from physics, the angular momentum of a CW helicopter will be pointing up, and the angular momentum of a single engine with CW rotation is pointing forward. To be clearer: Is there any impact (i.e. power efficiency, etc) if a helicopter's blades rotate CCW (seen from below), or if a single engine plane's propellers rotate CCW? Of course their torques will be different, but it is not the case in my question as long as it is not affecting the performance (i.e. reduce the power efficiency, etc).


Picture source: Picture 1, Picture 2;
Well helicopters are designed with both types of rotor systems.  American built helicopters have main rotors which rotate counter clockwise whereas European built helos have clockwise turning rotor systems.  Near as I know there is no particular advantage to one over the other, though you do have to reverse anti torque pedal corrections for collective inputs on a CW turning rotor system vs a CCW system, transverse flow effects are reversed and LTE events are more likely from right vs left crosswinds.
Just to be clear, torque is VISUALIZED as a vector perpendicular to the plane of rotation; it is not a force.  If the latter were true, you could propel craft to the moon and beyond using just a gyroscope.