Originally Posted by
Cruiser1970
Slipstream swirl is a corkscrewing airflow that travels around the fuselage.
This airflow strikes the vertical stabilizer, increasing its AOA. The increase in AOA of the vertical stabilizer pulls the tail to the right and yaws the nose to the left.
This situation is more prevalent at high power settings and low airspeeds.
To compensate, right rudder is required.
You are probably right, the spiral slipstream has more influence than the P-effect during takeoff, but don't let Bryan Hebert hear you say that. He and his devotee's say it doesn't exist. I think what they really mean to say is that it doesn't affect our models. I believe it is the reason we add right thrust.
Jim O