Counter-rotating propellers. . . .?

Question

To quote from Wikipedia: "In designing the Lockheed P-38, the decision was made to reverse the counter-rotation such that the "tops" of the propeller arcs move OUTWARDS, away from each other. Tests on the initial XP-38 prototype demonstrated greater accuracy in gunnery with the unusual configuration".

Obviously, had the "tops" of the propellers moved INWARDS, the accuracy of the Lightening's guns would have been not as good.

Why is this?

Answer 1

The guns on the Ligtning were in the central fuselage and ahead of the propeller arcs, so I don't think it was anything to do with the propellers affecting the path of bullets.



I would guess that it had something to do with the turbulence created by the props and the way that interacted with air flow over the wings. I think you would have to look at it in a wind tunnel to really understand why it happened.



Another possibility I just thought of: If the propellers were rotating tops-outward then the torque they created would tend to bend the wings upward slightly, creating a more pronounced dihedral angle. Generally the more pronounced the dihedral the more stable the aircraft is.

Answer 2

The tips of the propellers blades coming together close to the fuselage might have caused a momentary increase in air pressure, which might have had some effect on the path of bullets. They might have discovered in a wind tunnel that it worked better for the propeller blades to come together underneath than above. I'm just guessing.



I read somewhere that the RAF ordered a number of P-38s, but they wanted the engines and propellers to both rotate in the same direction, for ease of maintenance. These planes, they found, were much harder to fly, especially in takeoffs and landings, because the torque of the propellers added rather than cancelling each other.

Answer 3

Counter-rotating propellers, are got here upon on twin-engine, propeller-pushed plane and have propellers that spin in contrary guidelines. Counter-rotating propellers often spin clockwise on the left engine, and counter-clockwise on the suitable suited. the income of counter-rotating propellers is to stability out the effects of torque and p-component, removing the topic of the intense engine.Counter-rotating propellers should not be puzzled with Contra-rotating propellers.