ORIGINAL: opjose
Gyroscopic precession also contributes a great deal.
In one direction precession is ameliorating any pull to the belly, while in the other it exacerbates it.
The precession only occurs whilst the gyroscope is changing directions
While holding a steady attitude/line - there is no precession- It is basic physics
The prop running "out of square " that is slipping at some angle will cause it to try and move the craft of line
Just as a helicopter tilts the rotor slightly and whilst tilted the machine moves fore/aft/ left/right, due to the angle.
As the tilt is taking place (transitioning ) there is precession. Same on a fixed wing