Right thrust is used to attempt to minimise the effects of 'P' Factor and it occurs most pronounced at high deck angles at slow speeds and high power settings such as in a sustained climb or shortly after takeoff.

P factor is thrust disymetry caused by the desending propellor blade producing more thrust than the asecnding blade when at a high deck angle (relative wind to the propellor disc angle) causing a a yaw to the left with normal rotation engines.

This also affect full scale aircraft and many general aviation aircraft use right thrust. Its also the reason all full scale aircraft that do not have rudder trim must sustain right rudder imput during a climb (high deck angle, high power and slow speed).

John