Abstract: An aircraft flap drive system utilized a variable displacement motor (15) having a fluid pressure actuated device (23) to vary the displacement of the motor. The system includes a displacement control valve (41), and an electrohydraulic control means (55,67,85) operable in response to an electrical input signal (91) to communicate pressurized fluid from a source (11) to the motor. The displacement control valve (41) includes a load sensing arrangement (13,53,49) responsive to an increasing load on the motor to bias the displacement control valve toward a position whereby the motor moves toward its maximum displacement (minimum flow). One result is that the conventional fixed displacement motor, of a particular size and weight, may be replaced by a variable motor which is smaller and lighter.