A340 / A330 Hydraulics General The hydraulic system provides isolation, redundancy, monitoring and segregation. 3 independent systems (GRN, BLU, YLO) have their own backed up EDPs with electrical pumps as further backup. Operating pressure is 3000±200psi. The electrical pumps are for surface retraction only and cannot replace EDPs; the pump flow is about 18% of the EDP capacity. GRN system is further backed up by a RAT, located in the #3 (FCOM’s wrong) right flap track fairing. The RAT flow varies between 15-45% of an EDP capacity dependent on airspeed. A hand-pump is provided for the YLO system. The system gives priority to hydraulic demands from the rudder, elevators, ailerons, spoilers, brakes and reversers. The system is monitored by the Hydraulic System Monitoring Unit (HSMU). Generation E/WD hydraulic reservoir indication is normally green, goes amber if the fluid level is less than the warning level and goes white if no fluid temperature compensation is available. GRN system has single white/double amber bar at 17ltr, which triggers the HYD G RSVR Underfilled ECAM on the ground. Hydraulic reservoirs are pressurised by engine bleed air from engine #2 / #1: if this is insufficient, crossbleed air is used. The fire shut off valves are positioned upstream of each EDP and may be closed by operation of the FIRE pb switch or, in the case of engine #1 and #4, may be closed automatically by the HSMU in the event of GRN reservoir low level warning, thus isolating a possible leak in the engine pylon. A330: the fire shutoff valves operate in both engines for a GRN low level warning. The GRN system might then be restored by the RAT in the event of a further BLU or YLO reservoir low level warning. When GRN/YLO electrical pb is OFF, the pump is OFF even for HSMU back-up operations. The GRN system is powered by 2 EDPs off engines #1 and #4 / both. It is backed up by an electrical pump which can be manually or on –300 auto controlled: the pump auto-runs in flight for 25secs when the gear lever is selected UP and engine #1 or #4 fails (either engine) or on the ground when engines #1 and #4 are stopped and engines #2 and #3 are running (A330, not applicable), thus providing braking and NWS. Post-mod 45191, a pb allows the electrical pump to be manually switched OFF or indicates FAULT. A guarded AUTO pb allows the electrical pump to be manually switched ON or allowed to auto-operate. After an electrical power interruption, the GRN electrical pump will not restart (ON light remains out). A RAT provides emergency GRN pressure (2600psi): when the RAT is powering GRN, the aileron, elevator and spoiler servo control operating speeds are reduced. Watch out for the GRN leak measurement pb being left off after the ETOPS EMER GEN ground test. The BLU system is powered by an EDP off engine #2 / #1. It is backed up by a manually controlled electrical pump which uses the same logic as GRN/YLO and is labelled STBY although it has no auto function on basic A330. On A330E, after an ENG 1 fail as well as a PRIM 1/3 fail, the BLU ELEC PUMP runs automatically in flight to ensure sufficient authority on the electrical rudder, thereby counteracting the yaw sideslip induced by asymmetrical thrust (it is still labelled STBY). If the BLU electrical pump operation suffers an electrical interruption, it will not restart. The YLO system is powered by an EDP off engine #3 / #2. It is backed up by an electrical pump which can be manually or –300 auto controlled: the pump auto-runs in flight until last engine shutdown if the flaps/slats are not retracted, speed > 100kt and engine #3 /#2 fails or on the ground during cargo door operation, but does not run if the GRN elec pump is running to assist gear retraction. The pb switch logic is as per GRN. After an electrical power interruption, the YLO electrical pump will not restart (ON light remains out). On the ground, the YLO electric pump is auto shut down after an overheat. A hand pump can be used in order to operate the cargo doors when no electrical power is available. The RAT may be extended at any time by depressing the RAT MAN ON pb or automatically by the HSMU in the event of 4 / 2 engines failing, when electrical power is lost when engine #1 and #4 are stopped as the RAT is required for EMER GEN operation or –300 a low level in the GRN and BLU reservoirs. The RAT is auto-deployed for both engines failed or a low level in either GRN and BLU or in GRN and YLO. Distribution & Protection & Warnings The system aims to maintain 3 fully independent hydraulic systems simultaneously with adequately balanced system usage and priority control. GRN normally supplies all main users, BLU supplies alternate brakes, flight controls and slats and YLO supplies flight controls and flaps. Leak measurement valves are positioned upstream of the primary flight controls and are for leak measurement of each system. They may be closed on the ground from the maintenance panel. The YLO system valve is auto closed during cargo door operations. If low pressure is detected, a priority and pressure maintaining valve saves pressure for the brakes, flight controls and reversers. Normal gear, flap, slat, pitch trim, and EMER GEN operation may be lost. Pilots cannot control OR monitor priority valve operation. All the pb FAULT lights extinguish when selected OFF except for an overheat: in this case the FAULT light remains on until the overheat conditions ceases. Overhead Panel various ENG # FAULT lights
GYB ELEC PUMP FAULT lights
Aura l CRC SC SC SC SC
SD display
ECAM message
as below LO AIR PRESS amber pointer OVHT 1400
SC
amber arrow
B+Y SYS LO PR, etc GYB RSVR LO AIR PR (<22psi) GYB RSVR LO LVL (<8/5/5ltr) GYB RSVR OVHT (>95°C) GYB ENG # PUMP LO PR (<1450psi) GYB ELEC PUMP FAULT RAT FAULT
info reservoir low level, overheat, low air pressure or pump low pressure
as above + pump overheat RAT not fully stowed with stowing pressure applied or RAT not stowed with RPM < 3000
c:\…\29HYD.doc - created: 17 January 1995 - last saved: 21 December 2008
