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

Boeing 737 Operations Manual

Fire Protection

Chapter 8

Table of Contents

Section 0

8.0 Fire Protection-Table of Contents

Controls and Indicators

8.10.1

Overheat/Fire Protection Panel Switches

8.10.1

Overheat/Fire Protection Panel Lights

8.10.3

Cargo Fire Panel

8.10.4

Master Fire Warning Light

8.10.6

APU Ground Control Panel

8.10.7

Lavatory Fire

8.10.8

System Description

8.20.1

Introduction

8.20.1

Engine Fire Protection

8.20.1

Engine Overheat and Fire Detection

8.20.1

Engine Fire Extinguishing

8.20.2

Engine Fire Extinguisher Schematic

8.20.3

APU Fire Protection

8.20.4

APU Fire Detection

8.20.4

APU Fire Extinguishing

8.20.4

Main Wheel Well Fire Protection

8.20.5

Main Wheel Well Fire Detection

8.20.5

Cargo Compartment Fire Protection

8.20.5

Cargo Compartment Smoke Detection

8.20.5

Cargo Compartment Fire Warning

8.20.5

Cargo Compartment Fire Extinguishing

8.20.6

Cargo Fire Extinguisher Schematic

8.20.6

Lavatory Fire Protection

8.20.6

Lavatory Smoke Detection

8.20.6

Lavatory Fire Extinguisher System

8.20.7

Fire and Overheat System Tests

8.20.7

FAULT/INOP Test Detection

8.20.7

OVERHEAT/FIRE Test Detection

8.20.7

8.TOC.0.1

Boeing 737 Operations Manual

Fire Protection

Chapter 8

Controls and Indicators

Section 10

Overheat/Fire Protection Panel Switches

OVHT DET

WHEEL

BELL CUTOUT

L BOTTLE

R BOTTLE

WELL

DISCHARGE

ENGINES

NORMAL

DISCH

FAULT

DISCH

NORMAL

DISCH

ENG 1

ENG 2

OVERHEAT

APU DET

OVERHEAT

INOP

TEST

FIRE SWITCHES

APU BOTTLE

(FUEL SHUTOFF)

DISCHARGE

PULL WHEN ILLUMINATED

LOCK OVERRIDE: PRESS

BUTTON UNDER HANDLE

APU

AFT ELECTRONIC PANEL

Overheat Detector (OVHT DET) Switch

NORMAL - detection loop A and loop B are active.

A - detection loop A is active.

B - detection loop B is active.

Fire Warning BELL CUTOUT Switch

Push -

• extinguishes both master FIRE WARN lights

• silences the fire warning bell

• silences the remote APU fire warning horn (on the ground only)

• resets the system for additional warnings.

Extinguisher (EXT) TEST Switch

(spring-loaded to center)

1 or 2 - tests bottle discharge circuits for all three extinguisher bottles.

Fault/Inoperative (FAULT/INOP) and

Overheat/Fire (OVHT/FIRE) TEST Switch

(spring-loaded to center)

FAULT/INOP - tests fault detection circuits for both engines and the APU.

8.10.1

Fire Protection -

Controls and Indicators

Boeing 737 Operations Manual

OVHT/FIRE - tests overheat and fire detection loops on both engines and APU,

and wheel well fire detector

Note: See Fire and Overheat Detection System Fault Test in Section 20.

APU Fire Warning Switch

Illuminated (red) -

• indicates fire in APU

• unlocks APU fire warning switch.

Note: Master FIRE WARN lights illuminate, fire warning bell sounds, and in the

main wheel well the APU fire warning horn sounds (on ground only), and

APU fire warning light flashes.

In - normal position, mechanically locked if no fire signal.

Up -

• arms APU extinguisher circuit

• closes fuel shutoff valve, APU bleed air valve, and APU inlet door

• trips generator control relay and breaker

• allows APU fire warning switch to rotate.

Rotate (left or right) -

• discharges APU fire bottle.

Engine Fire Warning Switch

Illuminated (red) -

• indicates fire in related engine

• unlocks related engine fire warning switch.

Note: Master FIRE WARN lights illuminate and fire warning bell sounds.

In - normal position, mechanically locked if no fire signal.

Up -

• arms one discharge squib on each engine fire extinguisher

• closes fuel, hydraulic shutoff and engine bleed air valves

• disables thrust reverser

• trips generator control relay and breaker

• deactivates engine driven hydraulic pump LOW PRESSURE light

• allows engine fire warning switch to rotate.

Rotate (left or right) - discharges related fire bottle.

8.10.2

Fire Protection -

Controls and Indicators

Boeing 737 Operations Manual

Fire Warning Switch Override

FIRE SWITCH

LOCKED (NORMAL)

UNLOCKED

AFT ELECTRONIC PANEL

Fire Warning Switch Override

Push - unlocks fire warning switch.

Overheat/Fire Protection Panel Lights

OVHT DET

WHEEL

BELL CUTOUT

OVHT DET

L BOTTLE

R BOTTLE

WELL

DISCHARGE

FAULT

ENGINES

NORMAL

DISCH

NORMAL

DISCH

ENG 1

APU DET

ENG 2

OVERHEAT

INOP

TEST

APU BOTTLE

FIRE SWITCHES

DISCHARGE

(FUEL SHUTOFF)

PULL WHEN ILLUMINATED

LOCK OVERRIDE: PRESS

BUTTON UNDER HANDLE

APU

AFT ELECTRONIC PANEL

Engine (ENG) OVERHEAT Light

Illuminated (amber) - indicates overheat in related engine.

Note: MASTER CAUTION and OVHT/DET system annunciator lights

illuminate.

FAULT Light

Illuminated (amber) - with the overheat detector switch in NORMAL - indicates

both detector loops for an engine have failed.

Illuminated (amber) - with the overheat detector switch in A or B - indicates the

selected loop for an engine has failed.

Note: MASTER CAUTION and OVHT/DET system annunciator lights do not

illuminate.

8.10.3

Fire Protection -

Controls and Indicators

Boeing 737 Operations Manual

WHEEL WELL Fire Warning Light

Illuminated (red) - indicates fire in main gear wheel well

Note: Master FIRE WARN lights illuminate and fire warning bell sounds.

Engine BOTTLE DISCHARGE Light

Illuminated (amber) - indicates related fire extinguisher bottle has discharged.

APU Detector Inoperative (DET INOP) Light

Illuminated (amber) - indicates APU detector loop has failed.

Note: MASTER CAUTION and OVHT/DET system annunciator lights

illuminate.

APU BOTTLE DISCHARGE Light

Illuminated (amber) - indicates APU extinguisher bottle has discharged.

Extinguisher Test (EXT TEST) Lights

Illuminated (green) - EXT TEST switch is positioned to 1 or 2

and circuit

continuity is normal.

Cargo Fire Panel

EXT

DET SELECT

FWD AFT

NORM

DETECTOR

FAULT

FWD

AFT

DISCH

TEST

ARM

ARMED

FWD

AFT

DISCH

AFT ELECTRONIC PANEL

Extinguisher (EXT) Test Lights

Illuminated (green) - Cargo Fire TEST switch is pushed and fire bottle discharge

squib circuit continuity is normal.

8.10.4

Fire Protection -

Controls and Indicators

Boeing 737 Operations Manual

Detector Select (DET SELECT) Switches

NORM - detection loop A and B are active.

A - detection loop A is active.

B - detection loop B is active.

DETECTOR FAULT Light

Illuminated (amber) -

• Both loops in one or both cargo compartments have failed

Cargo Fire TEST Switch

PUSH - tests circuits for both forward and aft cargo fire detector loops and

suppression system.

Note: See Cargo Fire System Tests in Section 20.

Cargo Fire ARM Switches

[Option - Single Cargo Fire Extinguisher bottle]

PUSH -

• FWD ARMED - extinguisher armed for the forward cargo compartment

• AFT ARMED - extinguisher armed for the aft cargo compartment.

Cargo Fire (FWD/AFT) Warning Lights

Illuminated (red) -

• at least one detector in each loop detects smoke

• with power failed in one loop, at least one detector on the remaining loop

detects smoke.

Note: Master FIRE WARN lights illuminate and fire warning bell sounds.

Cargo Fire Bottle Discharge (DISCH) Light

Illuminated (amber) - indicates the extinguisher bottle has discharged

Cargo Fire Discharge (DISCH) Switch

PUSH - if system is armed, discharges the extinguisher bottle.

8.10.5

Fire Protection -

Controls and Indicators

Boeing 737 Operations Manual

Master Fire Warning Light

FIRE

WARN

BELL CUTOUT

GLARESHIELD

Master Fire Warning (FIRE WARN) Lights

Illuminated (red) - indicates a fire warning (or system test) in engine, APU, main

gear wheel well or cargo compartment

• fire warning bell sounds

• if on ground, remote APU fire warning horn sounds.

Push -

• extinguishes both master FIRE WARN lights

• silences fire warning bell

• silences remote APU fire warning horn

• resets system for additional warnings.

Note: Pushing fire warning bell cutout switch on overheat/fire protection panel

results in same actions.

8.10.6

Fire Protection -

Controls and Indicators

Boeing 737 Operations Manual

APU Ground Control Panel

A.P.U.

FIRE

CONTROL

1.PULL HANDLE DOWN

2.DISCHARGE BOTTLE

BOTTLE DISCHARGE

BOTTLE

HORN

DISCHARGE

CUTOUT

MAIN WHEEL WELL

APU BOTTLE DISCHARGE Switch

(spring-loaded to the right and saftied.)

Left - discharges APU extinguisher.

Note: Armed only if APU fire control handle is pulled at this panel.

APU Fire Control Handle

Up - normal position.

Down -

• arms APU BOTTLE DISCHARGE switch (on this panel only)

• closes APU fuel shutoff, bleed air valve and APU inlet door

• trips generator control relay and breaker.

APU Fire Warning HORN CUTOUT Switch

Push -

• silences fire alarm bell

• silences APU fire warning horn

• causes APU fire warning light to stop flashing but remain illuminated.

8.10.7

Fire Protection -

Controls and Indicators

Boeing 737 Operations Manual

APU Fire Warning Light

Illuminated (red flashing) - indicates fire in APU.

Note: Also, flight deck fire warning bell sounds and APU fire warning horn in

main wheel well sounds.

Illuminated (red steady) - indicates APU fire warning HORN CUTOUT switch

has been pushed following an APU fire indication.

Lavatory Fire

Lavatory Smoke Detection

[Option - Lavatory Smoke Light]

LAVATORY

SMOKE

FORWARD OVERHEAD PANEL

LAVATORY SMOKE Light

Illuminated (amber) -

• smoke has been detected in a lavatory

• a test is being conducted.

Note: MASTER CAUTION and OVERHEAD system annunciator lights

illuminate.

8.10.8

Boeing 737 Operations Manual

Fire Protection

Chapter 8

System Description

Section 20

Introduction

There are fire detection and extinguishing systems for:

• engines

• lavatories

• APU

• cargo compartments.

The engines also have overheat detection systems.

The main gear wheel well has a fire detection system, but no fire extinguishing

system.

Engine Fire Protection

Engine fire protection consists of these systems:

• engine overheat and fire detection powered by the battery bus

• engine fire extinguishing powered by the hot battery bus.

Engine Overheat and Fire Detection

Each engine contains two overheat/fire detector loops. Each loop provides both

fire and overheat detection. As the temperature of a detector increases to a

predetermined limit, the detector senses an overheat condition. At higher

temperatures, the detector senses a fire condition. Normally, both detector loops

must sense a fire or overheat condition to cause an engine overheat or fire alert.

The ENG OVERHEAT light or engine fire warning switch remains illuminated

until the temperature drops below the onset temperature.

An OVHT DET switch for each engine, labeled A, B, and NORMAL, permits

selection of either loop A or B, or both A and B, as the active detecting loops.

The system contains a fault monitoring circuit. If one loop fails with the OVHT

DET switch in NORMAL, that loop is automatically deselected and the remaining

loop functions as a single loop detector. There is no flight deck indication of single

loop failure. If both loops fail on an engine, the FAULT light illuminates and the

system is inoperative.

If the OVHT DET switch is positioned to A or B, the system operates as a single

loop system. The non-selected loop is not monitored. If the selected loop fails, the

FAULT light illuminates and the system is inoperative.

The indications of an engine overheat are:

• both MASTER CAUTION lights illuminate

• the OVHT/DET system annunciator light illuminates

• the related ENG OVERHEAT light illuminates.

8.20.1

Fire Protection -

System Description

Boeing 737 Operations Manual

The indications of an engine fire are:

• the fire warning bell sounds

• both master FIRE WARN lights illuminate

• the related engine fire warning switch illuminates

• all related engine overheat alert indications illuminate.

Engine Fire Extinguishing

The engine fire extinguisher system consists of two engine fire extinguisher

bottles, two engine fire warning switches, two BOTTLE DISCHARGE lights, and

an EXT TEST switch. Either or both bottles can be discharged into either engine.

The engine fire warning switches are normally locked down to prevent inadvertent

shutdown of an engine. Illumination of an engine fire warning switch or ENG

OVERHEAT light unlocks the engine fire warning switch. The switches may also

be unlocked manually.

Pulling the engine fire warning switch up:

• closes both the engine fuel shutoff valve and the spar fuel shutoff valve

• closes the engine bleed air valve resulting in loss of wing anti-ice to the

affected wing and closure of bleed air operated pack valve

• trips the generator control relay and breaker

• closes the hydraulic fluid shutoff valve. The engine driven hydraulic

pump LOW PRESSURE light is deactivated

• disables thrust reverser for the related engine.

• allows the engine fire warning switch to be rotated for discharge

• arms one discharge squib on each engine fire extinguisher bottle.

Rotating the engine fire warning switch electrically “fires” a squib, discharging

the extinguishing agent into the related engine. Rotating the switch the other way

discharges the remaining bottle.

The L or R BOTTLE DISCHARGE light illuminates a few seconds after the

engine fire warning switch is rotated, indicating the bottle has discharged.

8.20.2

Fire Protection -

System Description

Boeing 737 Operations Manual

APU Fire Protection

APU fire protection consists of these systems:

• APU fire detection powered by the battery bus.

• APU fire extinguishing powered by the hot battery bus.

APU Fire Detection

A single fire detection loop is installed on the APU. As the temperature of the

detector increases to a predetermined limit, the detector senses a fire condition.

The APU fire warning switch remains illuminated until the temperature of the

detector has decreased below the onset temperature.

The system contains a fault monitoring circuit. If the loop fails, the APU DET

INOP light illuminates indicating the APU fire detection system is inoperative.

The indications of an APU fire are:

• the fire warning bell sounds

• both master FIRE WARN lights illuminate

• the APU fire warning switch illuminates

• the APU automatically shuts down

• the wheel well APU fire warning horn sounds, (on the ground only), and

the wheel well APU fire warning light flashes.

APU Fire Extinguishing

The APU fire extinguisher system consists of one APU fire extinguisher bottle, an

APU fire warning switch, an APU BOTTLE DISCHARGE light, and an EXT

TEST switch. The APU ground control panel located in the right main wheel well

also contains an APU fire warning light, an APU BOTTLE DISCHARGE switch,

an APU fire control handle and APU HORN CUTOUT switch.

The APU fire warning switch is normally locked down to prevent inadvertent

shutdown of the APU. Illumination of the APU fire warning switch unlocks the

switch. The switch may also be unlocked manually.

Pulling the APU Fire Warning switch up:

• provides backup for the automatic shutdown feature

• deactivates the fuel solenoid and closes the APU fuel shutoff valve

• closes the APU bleed air valve

• closes the APU air inlet door

• trips the APU generator control relay and breaker

• allows the APU fire warning switch to be rotated for discharge

• arms the APU fire extinguisher bottle squib.

8.20.4

Fire Protection -

System Description

Boeing 737 Operations Manual

Rotating the APU fire warning switch in either direction electrically “fires” the

squib discharging the extinguishing agent into the APU. The APU BOTTLE

DISCHARGE light illuminates after a few seconds, indicating the bottle has

discharged.

Main Wheel Well Fire Protection

Main wheel well fire protection consists of fire detection powered by the No. 1 AC

transfer bus.

Note: The main wheel well has no fire extinguishing system. The nose wheel

well does not have a fire detection system.

Main Wheel Well Fire Detection

A single fire detector loop is installed in the main wheel well. As the temperature

of the detector increases to a predetermined limit, the detector senses a fire

condition. The WHEEL WELL fire warning light remains illuminated until the

temperature of the detector has decreased below the onset temperature.

The indications for a main wheel well fire are:

• the fire warning bell sounds

• both master FIRE WARN lights illuminate

• the WHEEL WELL fire warning light illuminates.

Cargo Compartment Fire Protection

Cargo fire protection consists of these systems:

• cargo compartment smoke detection powered by DC bus 1 and DC bus 2

• cargo compartment fire extinguishing powered by the hot battery bus.

Cargo Compartment Smoke Detection

The forward and aft cargo compartments each have smoke detectors in a dual loop

configuration. Normally, both detection loops must sense smoke to cause an alert.

These loops function in the same manner as the engine overheat/fire detection

loops.

Cargo Compartment Fire Warning

The indications of a cargo compartment fire are:

• the fire warning bell sounds

• both master FIRE WARN lights illuminate

• the FWD/AFT cargo fire warning light(s) illuminates.

8.20.5

Fire Protection -

System Description

Boeing 737 Operations Manual

Cargo Compartment Fire Extinguishing

[Option - Single cargo fire extinguisher bottle]

A single fire extinguisher bottle is installed in the air conditioning mix bay on the

forward wing spar. Detection of a fire in either the forward or aft compartment will

cause the FWD or AFT cargo fire warning light to illuminate. The extinguisher is

armed by pushing the appropriate cargo fire ARMED switch. Once armed, the

system is discharged by pushing the cargo fire DISCH switch. This results in the

total discharge of the bottle contents into the selected compartment. The cargo fire

DISCH light illuminates once the bottle is discharged. It may take up to 30

seconds for the light to illuminate.

Cargo Fire Extinguisher Schematic

Dual Loop Area

Smoke Detectors

Discharge Tubing/Nozzles

Fire

Bottle

FWD Cargo Compartment

AFT Cargo Compartment

Lavatory Fire Protection

Lavatory fire protection consists of these systems:

• lavatory smoke detection

• lavatory fire extinguishing (heat activated).

Lavatory Smoke Detection

The lavatory smoke detection system monitors for the presence of smoke. When

smoke is detected:

• an aural warning sounds

• the red alarm indicator light on the lavatory smoke detector panel

illuminates and the appropriate amber lavatory call light will flash

• the amber lavatory SMOKE light on the forward overhead panel

illuminates.

8.20.6

Fire Protection -

System Description

Boeing 737 Operations Manual

Lavatory Fire Extinguisher System

A fire extinguisher system is located beneath the sink area in each lavatory. When

a fire is detected:

• fire extinguisher operation is automatic

• flight deck has no indication of extinguisher discharge.

Fire and Overheat System Tests

The fire and overheat detection systems can be tested by pushing and holding the

FAULT/INOP and OVHT/FIRE TEST switch. Extinguisher continuity can be

tested by pushing and holding the EXT TEST switch. All test indications clear

when switches are released.

FAULT/INOP Test Detection

The fault detection circuits for both the engines and the APU are tested by pushing

and holding the FAULT/INOP and OVHT/FIRE TEST switch in the

FAULT/INOP position.

The indications for the FAULT/INOP test are:

• both MASTER CAUTION lights illuminate

• the OVHT/DET system annunciator light illuminates

• the FAULT light illuminates

• the APU DET INOP light illuminates.

OVERHEAT/FIRE Test Detection

The overheat and fire detection loops on both engines, the APU, and the fire

detector in the wheel well are tested by pushing and holding the FAULT/INOP and

OVHT/FIRE TEST switch in the OVHT/FIRE position.

The indications for the OVHT/FIRE test are:

• the fire warning bell sounds

• both master FIRE WARN lights illuminate

• both MASTER CAUTION lights illuminate

• the OVHT/DET system annunciator light illuminates

• both engine fire warning switches illuminate

• the APU fire warning switch illuminates

• both ENG OVERHEAT lights illuminate

• the WHEEL WELL fire warning light illuminates if AC power is

available

• on the ground, the wheel well APU fire warning horn sounds and the

wheel well APU fire warning light flashes.

8.20.7

Boeing 737 - 600/700/800/900. Operations Manual (1997 year) - page 38