ATA 29 - HYDRAULIC POWER

• With the BLUE ELEC PUMP pushbutton set to AUTO, the electric pump operates from the moment the first engine is started until the last engine is shut-down.

• The PTU is inhibited during the first engine start and automatically tested during the second engine start. (PTU it is be directional and starts if pressure is 500 PSI less then normal 3000 PSI).

• Yellow system components are in the hydraulic compartment in the right belly fairing.

• The Blue system components are in the hydraulic compartment in the left belly fairing. (Y&B fwd of MLG)

• A sampling valve is provided on the HP manifold.

• The PRIORITY VALVE makes sure that all available hydraulic pressure is sent to the primary flight controls if pressure in the system is reduced.

• The PTU is inhibited during the first engine start and cargo door operation.

• Each hydraulic reservoir is pressurized by air at 50 psi (Reservoir low pressure switch sends a signal to ECAM when reservoir air pressure is less than 22 PSI, Overpressure valve opens at 77 PSI).

• The engine 1 HP compressor (usual operation) or GRD connection.

• Water separator: There are two drain valves which prevent freezing of the water in the RPU. One is an automatic drain valve which is opened after each engine or APU shutdown, the other one is a manual self- sealing drain valve.

• Because of that the CSM/G is automatically switched off when the landing gear is extended. The aircraft gets its supply of electrical power from the batteries. Thus, the RAT has only to supply hydraulic power for the flight controls. The RAT is available and will operate through all of the flight envelope, but it will stall if the airspeed is less than 130 knots.