A contra-rotating propeller has two sets of blades rotating in opposite directions, but on the same axis. I think I remember reading somewhere (correct me if I'm wrong) that the angular momentum of this arrangement is zero because it cancels itself out.
So now I'm considering two normal engines, not on the same axis, like one engine per wing. These normal engines are not contra-rotating (they have only one blade set), but the right wing engine spins clockwise and the left wing engine spins counter-clockwise.
Do their angular momentums cancel out? Why or why not? It seems odd to me that it might depend on where the axis is even though their rotation behavior and angular moment are the same.
This question arose from a related one on aviation.stackexchange after I got curious if gyroscopic forces were significantly restricting yaw and pitch, especially for takeoff pitch-up. Basically I want to know if two engines experience twice as much gyroscopic forces, or if they cancel out.