Hydraulics -Controls and Indicators
Flight Control Panel (after Rudder System Enhancement Program (RSEP) modification)

FORWARD OVERHEAD PANEL

FLIGHT CONTROL Switches
STBY RUD – activates standby pump, opens standby rudder shutoff valve to
pressurize standby rudder power control unit, and illuminates amber STBY RUD
ON light.

OFF – closes flight control shutoff valve isolating ailerons, elevators and rudder
from associated hydraulic system pressure.
ON (guarded position) – normal operating position.

Hydraulics -Controls and Indicators 737 Operations Manual

Flight Control LOW PRESSURE Lights
Illuminated (amber) –
.  
indicates low hydraulic system (A or B) pressure to ailerons, elevator and
rudder

.  
deactivated when associated FLT CONTROL switch is positioned to
STBY RUD and standby rudder shutoff valve opens

.  
the A system light indicates A system pressure is low when full RPR
pressure is commanded.

Note:  The A system light will remain illuminated for approximately five seconds after A hydraulic system is activated.

STANDBY HYDRAULIC LOW QUANTITY Light
Illuminated (amber) –
.
indicates low quantity in standby hydraulic reservoir

.
always armed.

STANDBY HYDRAULIC LOW PRESSURE Light
Illuminated (amber) –
.
indicates output pressure of standby pump is low

.  
armed only when standby pump operation has been selected or automatic
standby function is activated.

ALTERNATE FLAPS Master Switch
OFF (guarded position) – normal operating position.
ARM – closes trailing edge flap bypass valve, activates standby pump, and arms ALTERNATE FLAPS position switch.

STBY RUD ON Light
Illuminated (amber) - indicates the standby hydraulic system is commanded on to pressurize the standby rudder power control unit.
Copyright . The Boeing Company. See title page for details.
13.10.6   December 5, 2003
737 Operations Manual
Hydraulics  Chapter 13 
System Description  Section 20 
Introduction 

The airplane has three hydraulic systems: A, B and standby. The standby system is used if system A and/or B pressure is lost. The hydraulic systems power the
following airplane systems:
.
flight controls

.
leading edge flaps and slats

.
trailing edge flaps

.
landing gear

.
wheel brakes

.
nose wheel steering

.
thrust reversers

.
autopilots

Either A or B hydraulic system can power all flight controls with no decrease in airplane controllability.
Each hydraulic system has a fluid reservoir located in the main wheel well area. System A and B reservoirs are pressurized by bleed air. The standby system reservoir is connected to the system B reservoir for pressurization and servicing. Pressurization of all reservoirs ensures positive fluid flow to all hydraulic pumps.
Hydraulic Power Distribution Schematic
AIR PRESSURE SYSTEM
A
ALTERNATE
BRAKES

AUTOPILOT A

M M
PTU CONTROL VALVE
NUMBER 1 THRUST REVERSER
INBOARD
FLIGHT SPOILER

NOSE WHEEL STEERING
GROUND
SPOILERS

STBY
SYSTEM

RUDDER
AILERONS
ELEVATOR AND
ELEV FEEL

LANDING
GEAR

LANDING GEAR
TRANSFER UNIT

M
POWER TRANSFER UNIT
AUTO SLATS
AND
LEADING EDGE
FLAPS & SLATS

NUMBER 2 THRUST REVERSER
OUTBOARD FLIGHT SPOILER
ALTERNATE NOSE WHEEL STEERING
1
AUTOPILOT B
AIR
SYSTEM
PRESSURE
B
YAW
DAMPER

NORMAL
BRAKES

TRAILING
EDGE FLAPS

As installed
Hydraulics -System Description 737 Operations Manual

A and B Hydraulic Systems
Components powered by hydraulic systems A and B are:
System A
.  
ailerons

.  
rudder

.  
elevator and elevator feel

.  
flight spoilers (one on each wing)

.  
ground spoilers

.  
alternate brakes

.  
No. 1 thrust reverser

.  
autopilot A

.  
normal nose wheel steering

.  
landing gear

.  
power transfer unit (PTU)

System B
.
ailerons

.  
rudder

.  
elevator and elevator feel