ACMP C2 ACMP C1 Left EDP Nose landing gear actuation Nose landing gear steering TE flaps primary drive LE slats primary drive Thrust reversers Main landing gear steering Wing flight controls Tail flight controls Wing flight controls Tail flight controls Wing flight controls Tail flight controls Main landing gear actuation Brakes Left ACM ADP C2 ADP C1 RAT Right ACM Right EDP Flap/slat priority valve Autobrake priority valve ALTN EXT power pack Heat exchanger Heat exchanger Reservoir fill select valve Center system return Hand pump Left system Right system Pressure Return Supply Bleed air Center system return Left system return Right system return Right system return Left system return Center system 12-8 Figure 12-6.  Large commercial aircraft hydraulic system. Figure 12-5.  Hydraulic power pack. Hydraulic System Components Reservoirs leakage, and simplifies troubleshooting. Some power pack  systems have an integrated actuator. These systems are used  to control the stabilizer trim, landing gear, or flight control  surfaces directly, thus eliminating the need for a centralized  hydraulic system. Figure 12-6  is a typical example of a hydraulic system in a  large commercial aircraft. The following sections discuss the  components of such system in more detail. The reservoir is a tank in which an adequate supply of fluid  for the system is stored. Fluid flows from the reservoir to the  pump, where it is forced through the system and eventually  returned to the reservoir. The reservoir not only supplies the  operating needs of the system, but it also replenishes fluid lost through leakage. Furthermore, the reservoir serves as an  overflow basin for excess fluid forced out of the system by  thermal expansion (the increase of fluid volume caused by  temperature changes), the accumulators, and by piston and  rod displacement. is that there is no need for a centralized hydraulic power  supply system and long stretches of hydraulic lines, which  reduces weight. Power packs could be driven by either an  engine gearbox or electric motor. Integration of essential  valves, filters, sensors, and transducers reduces system  weight, virtually eliminates any opportunity for external 