PURPOSE: To simultaneously realize cooling for an electronic control equipment, air-conditioning in an aircraft, and the supply of power for electric equipment used in the aircraft by providing a hydraulic pump driven by a prime mover and an air conditioner for a parking aircraft driven by the hydraulic motor on a movable truck.

CONSTITUTION: A truck loaded with a ground support device is self-run or pulled to the vicinity of an aircraft to be supported, and a connecting pipe 9 and a connecting wiring 10 are connected thereto. In such a condition, a hydraulic source 3 and an a.c. generator 4 are made no-load by fully opening a by-path valve 5 for controlling the discharge quantity and opening an electromagnetic switch 4b, and a prime mover 1 is started by a starting motor driven by a battery 12a. When the prime mover 1 comes to the rated rotating speed, the electromagnetic switch 4b is closed to start the supply of power to the aircraft, and oil pressure is supplied to hydraulic motors 6a-8a of the air conditioner AC, so that a compressor 6b, a blower 7b and a condenser fan 8b are respectively driven to supply air-conditioned air to the aircraft.