A method of engaging a drive system with a rotating wheel of an aircraft landing gear is disclosed. A motor is operated to apply torque to a pinion so the pinion rotates and moved from a neutral position to a contact position in which it contacts a rotating driven gear at an initial contact time, the rotating driven gear being mounted to a rotating wheel of an aircraft landing gear. After the initial contact time the pinion is moved further to a meshing position where the pinion meshes with the driven gear. A centre-to-centre distance between the pinion and the driven gear reduces as the pinion moves to the contact position and to the meshing position. The driven gear contacts the pinion in a series of impacts as the pinion moves from the contact position to the meshing position, each impact induces a spike in electromotive force or angular velocity at the motor.