Abstract This paper deals with combination controls, which present advantages of weight and cost saving which in recent years have been greatly enhanced by the dependability and ruggedness which can be built into them. Small electric motors, developed for aircraft-accessory operation, have permitted the construction of motor-operated valves. Both solenoid- and motor-operated valves now give the aircraft designer a wide choice of control characteristics. New methods and improvements in older types of follow-up systems for hydraulic controls are discussed in the paper.