This one can be done in a lab with windtunnel models. There is a theory that a propeller causes a spiralling stream of air over the airplane behind it that spirals in the same direction as the propeller's rotation.. The problem is that it is the only "theory" in aviation that is taught with out the mathematics to support it. See if you can use a smoke machine to catch this spiral. NOT the propeller tips produce a vortex ring around the plane too. That is NOT what I'd like you to try to capture Thanks
