Boeing 737-800 - A and B Hydraulic Systems; A and B Hydraulic System Pumps

737 Flight Crew Operations Manual
Hydraulics -
System Description
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13.20.2 D6-27370-866-EGP
A and B Hydraulic Systems
Components powered by hydraulic systems A and B are:
A and B Hydraulic System Pumps
Both A and B hydraulic systems have an engine–driven pump and an AC electric
motor–driven pump. The system A engine–driven pump is powered by the No. 1
engine and the system B engine–driven pump is powered by the No. 2 engine. An
engine–driven hydraulic pump supplies approximately 6 times the fluid volume of
the related electric motor–driven hydraulic pump.
The ENG 1 (system A) or ENG 2 (system B) pump ON/OFF switch controls the
engine–driven pump output pressure. Positioning the switch to OFF isolates fluid
flow from the system components. However, the engine–driven pump continues
to rotate as long as the engine is operating. Pulling the engine fire switch shuts off
the fluid flow to the engine–driven pump and deactivates the related LOW
PRESSURE light.
The ELEC 2 (system A) or ELEC 1 (system B) pump ON/OFF switch controls the
related electric motor–driven pump. If an overheat is detected in either system, the
related OVERHEAT light illuminates.
Note: Loss of an engine-driven hydraulic pump and a high demand on the
system may result in an intermittent illumination of the LOW PRESSURE
light for the remaining electric motor-driven hydraulic pump. The flight
control LOW PRESSURE light, Master Caution light, and the FLT CONT
and HYD system annunciator lights also illuminate.
System A System B
• ailerons
• rudder
• elevator and elevator feel
• flight spoilers
(two on each wing)
• ground spoilers
• alternate brakes
• No. 1 thrust reverser
• autopilot A
• normal nose wheel steering
• landing gear
• power transfer unit (PTU).
• ailerons
• rudder
• elevator and elevator feel
• flight spoilers
(two on each wing)
• leading edge flaps and slats
• trailing edge flaps
• normal brakes
• No. 2 thrust reverser
• autopilot B
• alternate nose wheel steering
• landing gear transfer unit
• autoslats
• yaw damper.
March 27, 2014