Drive system for aircraft landing gear

A drive system for rotating a wheel of an aircraft landing gear, the drive system comprising a pinion;

• a driven gear adapted to be mounted to a wheel of the aircraft landing gear;
• a motor arranged to rotate the pinion;
• an actuator which is arranged to move the pinion from a neutral position to a contact position in which it contacts the driven gear at an initial contact time;
• then after the initial contact time to move the pinion further to a meshing position where the pinion meshes with the driven gear, wherein 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 has Ngear teeth or rollers, and the pinion has Npinion teeth or rollers which mesh with the teeth or rollers of the driven gear when the pinion is at the meshing position;
• a sensor arranged to detect an angular velocity ωgear of the driven gear;
• a control loop which is responsive to a velocity demand input to control the motor so that it rotates at an angular velocity determined by the velocity demand input;
• and a controller arranged to determine the velocity demand input in accordance with a gear ratio (Npinion/Ngear), the angular velocity of the driven gear detected by the sensor, and a predetermined sync ratio, wherein the predetermined sync ratio is chosen so that the pinion is rotating at an angular velocity ωpinion at the initial contact time and ((ωpinion*Npinion)/(ωgear*Ngear)) is not 1.