Safety Investigation Report 2018:1 Factual Information/1.6/1.6.8 Aircraft Systems/7
SAFETY INVESTIGATION REPORT MH370 (9M-MRO)
7) Hydraulics
There are three independent hydraulic systems using electrical, pneumatics or engine driven power source. They are identified as Left, Centre and Right. Each hydraulic system can independently operate the flight controls for safe flight and landing.
Each hydraulic system uses a Hydraulic Interface Module Electronics Card (HYDIM) for automatic control and indications. The three systems operate independently at 3000 psi nominal pressure.
The left system is powered by an engine driven pump (EDP) and an electric motor pump (ACMP). The right system is also powered by an EDP and ACMP. The centre system has two ACMP and two air driven pumps (ADP) and a ram air turbine (RAT) pump.
Hydraulic pumps control and indication are on the P5 overhead panel. During normal operation the flight crew will select the switches to the auto position before flight. The pressure and quantity indication is provided on the hydraulic synoptic page and the status page.
The primary pumps are the EDPs in the left and right system and the ACMPs for the centre system. These pumps operate continuously. The demand pumps are the ACMPs for the left and right systems and the ADPs for the centre system. These pumps normally operate only during heavy system demands. The operation logic is controlled and monitored by the HYDIM cards.
The RAT deploys automatically during flight when both engines are shutdown or for loss of all three hydraulic power. The RAT hydraulic pump supplies hydraulic power to some of the center hydraulic system flight controls. When the aircraft is operating on RAT power only, the flap drive hydraulic motor is isolated from the center hydraulic system and as a result the flaps will not respond to the cockpit flap handle inputs.