Boeing 737 - 600/700/800/900. Operations Manual (1997 year)

Communications -

System Description

Boeing 737 Operations Manual

The flight deck crewmembers can make announcements using a PA handset or by

using any standard microphone and the related ACP. Flight Attendants make

announcements using PA handset located at their stations. The attendants use the

PA to play recorded music for passenger entertainment.

PA system use is prioritized. Flight deck announcements have first priority and

override all others. Flight Attendant announcements override the music system.

Call System

The call system is used as a means for various crewmembers to gain the attention

of other crewmembers and to indicate that interphone communication is desired.

Attention is gained through the use of lights and aural signals (chimes or horn).

The system can be activated from the flight deck, either flight attendant station, or

from the external power receptacle. Passengers may also use the system to call an

attendant, through the use of individual call switches at each seat.

The flight deck may be called from either flight attendant station or by the ground

crew. The ground crew may only be called from the flight deck. Flight Attendants

may be called from the flight deck, the other attendant station, or from any

passenger seat or lavatory. Master call lights in the passenger cabin identify the

source of incoming calls to the attendants.

Call system chime signals are audible in the passenger cabin through the PA

system speakers. The PA speakers also provide an alerting chime signal whenever

the NO SMOKING or FASTEN SEAT BELT signs illuminate or extinguish.

Location of Call

Called Position

Visual Signal at

Aural Signal at

Originator

Called Position

Flight deck

Attendant station

Pink master

Two-tone chime

call light

Flight deck

Nose wheel well

Horn in nose wheel

well

Attendant station

Flight deck

Blue flight deck

Single high-tone

call light

chime

Nose wheel well

Flight deck

Blue flight deck

Single high-tone

call light

chime

Flight deck

Passenger cabin

NO SMOKING or

Single low-tone

FASTEN BELT

chime

signs illuminate/

extinguish

5.20.4

Communications -

System Description

Boeing 737 Operations Manual

VHF Communications

Primary short-range voice communications is provided in the VHF range by three

independent radios. Each radio provides for selection of an active frequency and

an inactive

(preselected) frequency. Voice transmission and reception are

controlled at the related ACP.

[Option -Typical VHF control panel equipped airplanes]

VHF-1 control panel is located on the left side of the aft electronic panel, VHF-2

control panel is on the right and VHF-3 control panel is in the center. The VHF-2

and VHF-3 antennae are located on the lower fuselage, VHF-1 is on the upper

fuselage.

[Option - Typical for radio tuning panel equipped airplanes]

The VHF/HF RTP-1 is located on the forward left side of the aft electronic panel,

VHF/HF RTP-2 is on the forward right side and VHF/HF RTP-3 is on the aft

portion of the panel. The VHF-2 and VHF-3 antennae are located on the lower

fuselage, VHF-1 is on the upper fuselage.

Note: VHF antennae located on the lower fuselage are susceptible to multipath

interference from nearby structures or vehicles. This may disrupt VHF

communications. VHF antennae located on the upper fuselage are not as

susceptible to this interference.

HF Communications

[Option - Typical for radio tuning panel equipped airplanes]

The HF communication radio can be tuned by any radio tuning panel. HF radio

sensitivity can only be set on the on-side radio tuning panel.

[Option - Typical for HF control panel equipped airplanes]

The HF radio communications control panel allows for frequency selection and

adjustment of radio sensitivity.

The audio control panels are used to control voice transmission and receiver

monitoring. When an HF transmitter is keyed after a frequency change, the

antenna tunes. While the antenna is being tuned, a steady or intermittent tone may

be heard through the audio system (tuning takes a maximum of 15 seconds). The

antenna is located in the vertical stabilizer.

5.20.5

Communications -

System Description

Boeing 737 Operations Manual

Cockpit Voice Recorder

The cockpit voice recorder uses four independent channels to record flight deck

audio for 120 minutes. Recordings older than 120 minutes are automatically

erased. One channel records flight deck area conversations using the area

microphone. The other channels record individual ACP output (headset) audio

and transmissions for the pilots and observer.

ACARS System

The ARINC Communications Addressing and Reporting System (ACARS) is an

addressable digital data link system which permits exchange of data and messages

between an airplane and a ground-based operation center utilizing an onboard

VHF communications system.

The ACARS airborne subsystem provides for the manual entry of routine data

such as departure/arrival information. Also possible is manual entry of addresses

(telephone codes) of parties on the ground for voice communications.

The airborne system consists of a management unit in the E/E compartment, either

a interactive display unit or multipurpose control display unit (MCDU), and

frequently a printer. Data is entered and transmitted to the ground operations

center.

5.20.6

Boeing 737 Operations Manual

Electrical

Chapter 6

Table of Contents

Section 0

6.0 Electrical-Table of Contents

Controls and Indicators

6.10.1

AC and DC Metering Panel

6.10.1

Generator Drive and Standby Power Panel

6.10.5

Ground Power Panel and Bus Switching Panel

6.10.7

Ground Service Switch

6.10.9

System Description

6.20.1

Introduction

6.20.1

Electrical Power Generation

6.20.2

Engine Generators

6.20.2

APU Generator

6.20.2

External Ground Power

6.20.2

Ground Service

6.20.2

Electrical Power Schematic

6.20.3

AC Power System

6.20.5

Bus Tie System

6.20.5

Automatic Load Shedding (Engine Generators)

6.20.6

APU Automatic Load Shedding

6.20.6

AC Power Schematic

6.20.7

Electrical Power Controls and Monitoring

6.20.8

Generator Drive

6.20.8

AC Voltmeter, Ammeter and Frequency Meter

6.20.8

DC Voltmeter and Ammeter

6.20.8

Electrical Power Controls and Monitoring Schematic

6.20.9

DC Power System

6.20.11

Transformer Rectifier Units

6.20.11

Battery Power

6.20.11

Battery Charger Transformer/Rectifier

6.20.12

DC Power System Schematic

6.20.14

Standby Power System

6.20.16

6.TOC.0.1

Boeing 737 Operations Manual

Electrical

Chapter 6

Controls and Indicators

Section 10

AC and DC Metering Panel

[Option - Single battery with CAB/UTIL switch]

DC AMPS

CPS FREQ

DC VOLTS

AC AMPS

AC VOLTS

BAT

TR UNIT

ELEC

DISCHARGE

MAINT

TR1

APU GEN

BAT

TR2

GEN2

GEN1

BAT

GRD

TR3

INV

BUS

PWR

STBY

TEST

STBY

TEST

PWR

OFF

BAT

IFE/PASS

CAB/UTIL

SEAT

FORWARD OVERHEAD PANEL

6.10.1

Electrical -

Controls and Indicators

Boeing 737 Operations Manual

[Option - Dual battery with CAB/UTIL switch]

DC AMPS

CPS FREQ

DC VOLTS

AMPS

AC VOLTS

BAT

TR UNIT

ELEC

DISCHARGE

MAINT

AUX BAT

APU GEN

BAT

TR1

GEN1

GEN2

BAT

GRD

TR2

INV

BUS

PWR

STBY

TR3

STBY

TEST

PWR

TEST

PWR

OFF

BAT

IFE/PASS

CAB/UTIL

SEAT

FORWARD OVERHEAD PANEL

DC Ammeter

Indicates amperage of source selected by DC meters selector.

DC Voltmeter

Indicates voltage of source selected by DC meters selector.

AC Ammeter

Indicates amperage of source selected by AC meters selector.

Frequency Meter

Indicates frequency of source selected by AC meters selector.

6.10.2

Electrical -

Controls and Indicators

Boeing 737 Operations Manual

AC Voltmeter

Indicates voltage of source selected by AC meters selector.

Battery Discharge (BAT DISCHARGE) Light

Illuminated (amber) - with BAT switch ON, excessive battery discharge detected.

TR UNIT Light

Illuminated (amber) -

• on the ground - any TR has failed.

• in flight -

• TR1 failed; or

• TR2 and TR3 failed.

Electrical (ELEC) Light

Illuminated (amber) - a fault exists in DC power system or standby power system.

Note: Operates only with airplane on ground.

Maintenance Test (MAINT) Switch

Used by maintenance.

DC Meters Selector

Selects DC source for DC voltmeter and DC ammeter indications.

TEST - used by maintenance.

Battery (BAT) Switch

OFF -

• removes power from battery bus and switched hot battery bus when

operating with normal power sources available

• removes power from battery bus, switched hot battery bus, DC standby

bus, static inverter, and AC standby bus when battery is only power

source.

ON (guarded position) -

• provides power to switched hot battery bus

• energizes relays to provide automatic switching of standby electrical

system to battery power with loss of normal power.

AC Meters Selector

Selects AC source for AC voltmeter, AC ammeter and frequency meter

indications

6.10.3

Electrical -

Controls and Indicators

Boeing 737 Operations Manual

TEST - used by maintenance.

CAB/UTIL Switch

OFF - removes electrical power from cabin recirculation fan, fwd & aft door area

heaters, drain mast heaters, lavatory water heaters, all 115V AC galley busses,

logo lights, potable water compressor, and 115V AC shaver outlets when installed.

ON - supplies electrical power to recirculation fan, fwd & aft door area heaters,

drain mast heaters, lavatory water heaters, all 115V AC galley busses, logo lights,

potable water compressor, and 115V AC shaver outlets when installed.

CAB/UTIL Switch

OFF - removes electrical power from left & right recirculation fans, fwd & aft

door area heaters, drain mast heaters, lavatory water heaters, all 115V AC galley

busses, logo lights, potable water compressor, and 115V AC shaver outlets when

installed.

ON - supplies electrical power to left & right recirculation fans, fwd & aft door

area heaters, drain mast heaters, lavatory water heaters, all 115V AC galley

busses, logo lights, potable water compressor, and 115V AC shaver outlets when

installed.

IFE/PASS SEAT Switch

OFF - removes electrical power from installed components of the passenger seats

and in-flight entertainment systems including: 115V AC audio entertainment

equipment, 115V AC video entertainment equipment, cabin telephone equipment,

FAX machine, printer, 28V DC video equipment and passenger seat electronic

outlets.

ON - supplies electrical power to installed components of the passenger seats and

in-flight entertainment systems including:

115V AC audio entertainment

equipment, 115V AC video entertainment equipment, cabin telephone equipment,

FAX machine, printer, 28V DC video equipment and passenger seat electronic

outlets.

6.10.4

Electrical -

Controls and Indicators

Boeing 737 Operations Manual

Generator Drive and Standby Power Panel

STANDBY

PWR OFF

DRIVE

STANDBY POWER

DISCONNECT

BAT OFF AUTO

FORWARD OVERHEAD PANEL

Generator Drive (DRIVE) Lights

Illuminated (amber) - Integrated drive generator (IDG) low oil pressure caused by

one of the following:

• IDG failure

• engine shutdown

• IDG automatic disconnect due to high oil temperature

• IDG disconnected through generator drive DISCONNECT switch.

Generator Drive Disconnect (DISCONNECT) Switches (guarded)

Disconnects IDG if electrical power is available and engine start lever is in IDLE.

IDG cannot be reconnected in the air.

STANDBY Power Off (PWR OFF) Light

Illuminated (amber) - one or more of the following busses are unpowered:

• AC standby bus

• DC standby bus

• battery bus.

6.10.5

Electrical -

Controls and Indicators

Boeing 737 Operations Manual

STANDBY POWER Switch

AUTO (guarded position) -

• In flight, or on the ground, and AC transfer busses powered:

• AC standby bus is powered by AC transfer bus 1

• DC standby bus is powered by TR1 and TR2. TR3 is a backup source

• In flight, or on the ground, loss of all AC power

• AC standby bus is powered by battery through static inverter

• DC standby bus is powered by battery.

OFF (center position) -

• STANDBY PWR OFF light illuminates

• AC standby bus, static inverter, and DC standby bus are not powered.

BAT (unguarded position) -

• AC standby bus is powered by battery through static inverter

• DC standby bus and battery bus are powered directly by battery.

6.10.6

Electrical -

Controls and Indicators

Boeing 737 Operations Manual

Ground Power Panel and Bus Switching Panel

GRD POWER

AVAILABLE

GRD

PWR

OFF

BUS TRANSFER

TRANSFER

BUS OFF

SOURCE

OFF

GEN OFF

APU GEN

GEN OFF

BUS

OFF BUS

BUS

OFF

GEN 1

APU GEN

GEN 2

FORWARD OVERHEAD PANEL

Ground Power Available (GRD POWER AVAILABLE) Light

Illuminated (blue) - ground power is connected and meets airplane power quality

standards.

Ground Power (GRD PWR) Switch

Three position switch, spring-loaded to neutral

OFF - disconnects ground power from AC transfer busses.

ON - if momentarily moved to ON position and ground power is available:

• removes previously connected power from AC transfer busses

• connects ground power to AC transfer busses if power quality is correct.

TRANSFER BUS OFF Lights

Illuminated (amber) - related transfer bus is not powered.

6.10.7

Electrical -

Controls and Indicators

Boeing 737 Operations Manual

SOURCE OFF Lights

Illuminated (amber) - no source has been manually selected to power the related

transfer bus, or the manually selected source has been disconnected

• if a source has been selected to power the opposite transfer bus, both

transfer busses are powered.

Generator Off Bus (GEN OFF BUS) Lights

Illuminated (blue) - IDG is not supplying power to the related transfer bus.

Generator (GEN) Switches

Three position switch, spring-loaded to neutral.

OFF - disconnects IDG from related AC transfer bus by opening generator circuit

breaker.

ON - connects IDG to related AC transfer bus by disconnecting previous power

source and closing generator circuit breaker,

BUS TRANSFER Switch

AUTO (guarded position) - BTBs operate automatically to maintain power to AC

transfer busses from any operating generator or external power

• DC cross tie relay automatically provides normal or isolated operation as

required.

OFF - isolates AC transfer bus 1 from AC transfer bus 2 if one IDG is supplying

power to both AC transfer busses

• DC cross tie relay opens to isolate DC bus 1 from DC bus 2.

APU Generator Off Bus (GEN OFF BUS) Light

Illuminated (blue) - APU is running and not powering a bus.

APU Generator (GEN) Switches

Three position switch, spring-loaded to neutral.

OFF -

• APU generator powering both AC transfer busses

• moving a single APU GEN switch to OFF illuminates related

SOURCE OFF light. APU continues to power AC transfer busses

• subsequently moving other APU GEN switch to OFF disconnects

APU generator from tie bus and removes APU power from AC

transfer busses

• APU generator powering one AC transfer bus; IDG powering one AC

transfer bus

6.10.8

Electrical -

Controls and Indicators

Boeing 737 Operations Manual

• moving related APU GEN switch to OFF disconnects APU generator

from tie bus and AC transfer bus. IDG powers AC transfer busses.

ON -

• Neither AC transfer bus powered by IDG - moving a single APU GEN

switch to ON:

• connects both AC transfer busses to the APU generator

• disconnects external power, if connected

• opposite SOURCE OFF light illuminates until the other APU GEN

switch is moved to ON.

• Both AC transfer busses powered by IDGs - moving an APU GEN switch

ON:

• powers the related AC transfer bus from the APU generator

• other AC transfer bus continues to receive power from the IDG.

Ground Service Switch

GROUND

SERVICE

FWD ATTENDANT PANEL

GROUND SERVICE Switch

Momentary push-button switch.

Provides manual control of ground service busses. Enables servicing airplane

using external power without activating AC transfer busses.

Illuminated (white) -

• ON - connects external power to ground service busses

• OFF - disconnects external power from ground service busses.

6.10.9

Boeing 737 Operations Manual

Electrical

Chapter 6

System Description

Section 20

Introduction

Single Battery

[Option]

Primary electrical power is provided by two engine integrated drive generators

(IDGs) which supply three-phase, 115 volt, 400 cycle alternating current. Each

IDG supplies its own bus system in normal operation and can also supply essential

and non-essential loads of the opposite side bus system when one IDG is

inoperative. Transformer rectifier (TR) units and a battery/battery charger supply

DC power. The battery also provides backup power for the AC and DC standby

system. The APU operates a generator and can supply power to both AC transfer

busses on the ground or in flight.

There are two basic principles of operation for the 737 electrical system:

• There is no paralleling of the AC sources of power.

• The source of power being connected to a transfer bus automatically

disconnects an existing source.

The electrical power system may be categorized into three main divisions: the AC

power system, the DC power system, and the standby power system.

Dual Battery

[Option]

Primary electrical power is provided by two engine integrated drive generators

(IDGs) which supply three-phase, 115 volt, 400 cycle alternating current. Each

IDG supplies its own bus system in normal operation and can also supply essential

and non-essential loads of the opposite side bus system when one IDG is

inoperative. Transformer rectifier (TR) units and the main battery/battery charger

supply DC power. The main and auxiliary batteries also provide backup power for

the AC and DC standby system. The APU operates a generator and can supply

power to both AC transfer busses on the ground or in flight.

There are two basic principles of operation for the 737 electrical system:

• There is no paralleling of the AC sources of power.

• The source of power being connected to a transfer bus automatically

disconnects an existing source.

The electrical power system may be categorized into three main divisions: the AC

power system, the DC power system, and the standby power system.

6.20.1

Electrical -

System Description

Boeing 737 Operations Manual

Electrical Power Generation

Engine Generators

Primary power is obtained from two engine IDGs. The IDG maintains a constant

generator speed throughout the normal operating range of the engine. An integral

electro-mechanical disconnect device provides for complete mechanical isolation

of the IDG.

APU Generator

The APU generator can supply power to both AC transfer busses on the ground or

in flight. As the only power source, the APU generator can meet electrical power

requirements for all ground conditions and most flight conditions.

External Ground Power

An external AC power receptacle located near the nose gear wheel well, on the

lower right side of the fuselage, allows the use of an external power source. Status

lights on a panel adjacent to the receptacle permit the ground crew to determine if

external power is being used. When connected, external power can supply power

to both transfer busses.

Ground Service

For ground servicing, a ground service switch is on the forward attendant’s panel.

The switch provides ground power directly to the AC ground service busses for

utility outlets, cabin lighting and the battery charger without powering all airplane

electrical busses. The ground service switch is a momentary push button and is

overridden when both AC transfer busses are powered.

6.20.2

Electrical -

System Description

Boeing 737 Operations Manual

Electrical Power Schematic

[Option - Single battery]

EXTERNAL AC

RECEPTACLE

GEN

APU

GEN

DRIVE

GCB1

GCB2

AC TRANSFER BUS 1

AC TRANSFER BUS 2

BTB1

BTB2

GND SERVICE

RELAY

GALLEY

115V AC

GALLEY

BUS C & D

MAIN BUS 1

MAIN BUS 2

BUS A & B

115V AC GND

SERVICE BUS 1

SERVICE BUS 2

TR1

TR3

TR2

CROSS BUS

TIE RELAY

DC BUS 1

DC BUS 2

DC STANDBY BUS

BATTERY BUS

AC STANDBY BUS

HOT BATTERY BUS

INV

SWITCHED

BATT

HOT BAT BUS

CHGR

TO APU STARTER

BAT

Airplane Configuration - In Flight

Battery Switch

- ON

Standby Power Switch - AUTO

Bus Transfer Switch - AUTO

ENGINE GENERATOR CONNECTED TO RELATED BUS

6.20.3

Electrical -

System Description

Boeing 737 Operations Manual

[Option - Dual battery]

EXTERNAL AC

RECEPTACLE

GEN

APU

GEN

DRIVE

GCB1

GCB2

AC TRANSFER BUS 1

AC TRANSFER BUS 2

BTB1

BTB2

GND SERVICE

RELAY

GALLEY

115V AC

GALLEY

BUS C & D

MAIN BUS 1

MAIN BUS 2

BUS A & B

115V AC GND

SERVICE BUS 1

SERVICE BUS 2

TR1

TR3

TR2

CROSS BUS

TIE RELAY

DC BUS 1

DC BUS 2

DC STANDBY BUS

BATTERY BUS

AUX

AC STANDBY BUS

HOT BATTERY BUS

BATT

CHGR

INV

SWITCHED

BATT

HOT BAT BUS

CHGR

AUX BAT

TO APU STARTER

BAT

Airplane Configuration - In Flight

Battery Switch

- ON

Standby Power Switch - AUTO

Bus Transfer Switch - AUTO

ENGINE GENERATOR CONNECTED TO RELATED BUS

6.20.4

Electrical -

System Description

Boeing 737 Operations Manual

AC Power System

Each AC power system consists of a transfer bus, a main bus, two galley busses,

and a ground service bus. Transfer bus 1 also supplies power to the AC standby

bus. If the AC source powering either transfer bus fails or is disconnected, the

transfer bus can be powered by any available source through the tie bus with the

bus tie breakers (BTBs).

With the airplane on the ground and both generator control switches OFF, or with

both engines shut down, selecting the GRD PWR switch ON connects external

power to both transfer busses. Likewise, selecting either APU GEN switch ON

connects APU power to both transfer busses. Whichever source is selected last

powers both busses. It is not possible to power one transfer bus with external

power and one transfer bus with APU power.

The transfer busses can be powered from the engine generators by momentarily

positioning the related generator switch to ON. This closes the related generator

circuit breaker (GCB) and connects the generator to the transfer bus. Whenever

external power or APU is powering both transfer busses, and engine generator

power is applied to its onside transfer bus, external power or APU continues to

supply power to the remaining transfer bus.

In flight, each engine generator normally powers its own transfer bus. If an engine

generator is no longer supplying power, the BTBs automatically close to allow the

other engine generator to supply both transfer busses through the tie bus and

BTBs. The APU can power either or both busses through the BTBs.

The system also incorporates an automatic generator on-line feature in case the

airplane takes off with the APU powering both transfer busses. If the APU is either

shut down or fails, the engine generators are automatically connected to their

related transfer busses. This action occurs only once in flight and only under the

circumstances described above.

Bus Tie System

Either generator or the APU can supply power to both transfer busses. If the BUS

TRANS switch is in the AUTO position and the source powering the transfer bus

is disconnected or fails, the source powering the opposite transfer bus

automatically picks up the unpowered transfer bus through the BTBs.

6.20.5

Boeing 737 - 600/700/800/900. Operations Manual (1997 year) - page 33