Commercial 

Airplanes 737

Service Bulletin

ALERT

Number: 737-31A1398

Original Issue: January 07, 2010

ATA System: 3126

SUBJECT: INDICATING/RECORDING SYSTEMS - Aural Warning System - Installation Of The

Cabin Altitude Warning System And Takeoff Configuration Warning System Lights

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Table of Contents

Summary ...................................................... 5

1. PLANNING INFORMATION ........................................ 7

A. Effectivity ................................................ 7

1. Airplanes ............................................. 7

2. Spares Affected ......................................... 7

B. Concurrent Requirements ....................................... 8

C. Reason ................................................. 8

D. Description ............................................... 8

E. Compliance .............................................. 8

F. Approval ................................................ 8

G. Manpower ............................................... 9

H. Weight and Balance Changes .................................... 9

I. Electrical Load Data .......................................... 9

J. References .............................................. 9

1. Existing Data .......................................... 9

2. Data supplied with this Service Bulletin ............................ 9

3. Installation Drawings Used in the Preparation of this Service Bulletin ............ 9

K. Publications Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

L. Interchangeability and Intermixability of Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2. MATERIAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

A. Material - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

B. Industry Support Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

C. Parts Necessary For Each Airplane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1. Kits/Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2. Parts and Materials Supplied by the Operator . . . . . . . . . . . . . . . . . . . . . . . . 11

3. Parts Modified and Reidentified . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4. Parts Removed and Not Replaced . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

D. Parts Necessary to Change Spares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

E. Special Tooling - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

F. Special Tooling Necessary to do this Service Bulletin . . . . . . . . . . . . . . . . . . . . . . . 11

3. ACCOMPLISHMENT INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

A. GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

B. WORK INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

FIGURE 1: WIRE BUNDLE W066 WIRE ROUTING . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

FIGURE 2: ACTIVATION OF THE CABIN ALTITUDE WARNING AND TAKEOFF CONFIGURATION

WARNING LIGHTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

FIGURE 3: REMOVE THE INOP MARKERS AT THE L1304 AND L1316 LIGHT ASSEMBLIES . . . 18

FIGURE 4: L1304 AND L1316 LIGHT ASSEMBLY REFERENCE . . . . . . . . . . . . . . . . . . . . 20

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Commercial 

Airplanes 737

Service Bulletin

ALERT

Summary Number: 737-31A1398

Original Issue: January 07, 2010

ATA System: 3126

SUBJECT: INDICATING/RECORDING SYSTEMS - Aural Warning System - Installation Of The

Cabin Altitude Warning System And Takeoff Configuration Warning System Lights

THIS BULLETIN IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH

1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS SERVICE BULLETIN TO

THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS SERVICE BULLETIN TO

THE NEW OWNER.

CONCURRENT REQUIREMENTS

None.

BACKGROUND

This service bulletin gives the instructions to activate the cabin altitude warning system and takeoff configuration

warning lights. Incorporation of this service bulletin will allow the operator to activate the cabin altitude warning

system and takeoff configuration warning lights. Activation of these lights will provide a visual indication to the

flight crew to be used in conjunction with the existing aural warning horn for cabin altitude and takeoff configuration

alerts. The visual warning lights are intended to provide additional notice to crews to prepare a correct takeoff

configuration, respond to excessive cabin altitude and avoid confusion between the takeoff configuration and

cabin altitude alerts. An unrecognized incorrect takeoff configuration or excessive cabin altitude could prevent

a continued safe flight and landing.

ACTION

Get access to the flight compartment. Remove the P2-2 panel to get access to the W066 wire bundle located

behind the panel. Change the wiring in the W066 wire bundle. Remove the INOP markers from the cabin altitude

warning system and takeoff configuration warning lights. Do an operational test of the cabin altitude warning

system and takeoff configuration warning lights.

EFFECTIVITY

737-400 Airplanes. Refer to Paragraph 1.A.1., Airplanes for the list of affected airplanes.

COMPLIANCE

The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service

bulletin. The Airworthiness Directive will make the compliance tasks and times given in this service bulletin

mandatory.

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Boeing recommends that the change given in this service bulletin be done within 36 months after the date of

this service bulletin.

INDUSTRY SUPPORT INFORMATION

Boeing warranty remedies are not available for the configuration changes given in this service bulletin.

MANPOWER

Airplanes Total Task Hours Elapsed Hours

PW234 1.75 1.75

MATERIAL INFORMATION

None.

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Commercial 

Airplanes 737

Service Bulletin

ALERT

Number: 737-31A1398

Original Issue: January 07, 2010

ATA System: 3126

SUBJECT: INDICATING/RECORDING SYSTEMS - Aural Warning System - Installation Of The

Cabin Altitude Warning System And Takeoff Configuration Warning System Lights

THIS BULLETIN IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH

1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS SERVICE BULLETIN TO

THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS SERVICE BULLETIN TO

THE NEW OWNER.

1. PLANNING INFORMATION

A. Effectivity

1. Airplanes

This service bulletin is for the airplanes shown below.

Refer to Service Bulletin Index Document D6-19567 Part 3 for Airplane Variable Number, Line

Number, and Serial Number data.

GROUP CONFIGURATION DESCRIPTION

Airplanes with Cabin Altitude Warning System and Takeoff

Configuration Warning System Lights installed and deactivated.

Accomplishment of Boeing Service Bulletin 737-31-1377 deactivated

the lights.

1 -

Airplane Models:

737-400

Variable Number Group

PW234 1

2. Spares Affected

None.

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B. Concurrent Requirements

None.

C. Reason

This service bulletin gives the instructions to activate the cabin altitude warning system and takeoff

configuration warning lights. Incorporation of this service bulletin will allow the operator to activate the

cabin altitude warning system and takeoff configuration warning lights. Activation of these lights will

provide a visual indication to the flight crew to be used in conjunction with the existing aural warning

horn for cabin altitude and takeoff configuration alerts. The visual warning lights are intended to provide

additional notice to crews to prepare a correct takeoff configuration, respond to excessive cabin altitude

and avoid confusion between the takeoff configuration and cabin altitude alerts. An unrecognized

incorrect takeoff configuration or excessive cabin altitude could prevent a continued safe flight and

landing

D. Description

Get access to the flight compartment. Remove the P2-2 panel to get access to the W066 wire bundle

located behind the panel. Change the wiring in the W066 wire bundle. Remove the INOP markers from

the cabin altitude warning system and takeoff configuration warning lights. Do an operational test of

the cabin altitude warning system and takeoff configuration warning lights.

The work in this service bulletin is done in the maintenance zone(s) given below.

Affected Maintenance Zones

Model Zone

737-400 101, 102

E. Compliance

The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to

this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in this

service bulletin mandatory.

Boeing recommends that the change given in this service bulletin be done within 36 months after the

date on this service bulletin.

F. Approval

This service bulletin was examined by the Federal Aviation Administration (FAA). The changes specified

in this service bulletin comply with the applicable regulations and are FAA approved, as well as European

Aviation Safety Agency (EASA)/Joint Aviation Authorities (JAA) approved for all EASA/JAA approved

airplanes listed in the service bulletin effectivity. This service bulletin and its approval were based on

the airplane in its original Boeing delivery configuration or as modified by other approved Boeing

changes.

If an airplane has a non-Boeing modification or repair that affects a component or system also affected

by this service bulletin, the operator is responsible for obtaining appropriate regulatory agency approval

before incorporating this service bulletin.

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G. Manpower

The table below shows an estimate of the task hours necessary to do this change for each airplane.

This estimate is for direct labor only, done by an experienced crew. Adjust the estimate with operator

task hour data if necessary. The estimate does not include lost time. These are some examples of lost

time:

• Time to adjust to the workplace

• Time to schedule the work

• Time to inspect the work

• Time to cure the materials

• Time to make the parts

• Time to find the tools.

Number of Per- Task Hours Elapsed Hours

sons

Task

Open Access 1 0.25 0.25

Change 1 0.50 0.50

Close Access 1 0.25 0.25

Test 1 0.75 0.75

TOTAL FOR EACH AIRPLANE 1.75 1.75

H. Weight and Balance Changes

None.

I. Electrical Load Data

Not changed.

J. References

1. Existing Data

a. Standard Overhaul Practices Manual (SOPM) 20-50-05

b. Standard Wiring Practices Manual (SWPM) 20-00-11, 20-10-11, 20-10-12, 20-10-19

c. 737-300/400/500 Wiring Diagram Manual (WDM) 21-33-01, 27-43-01

2. Data supplied with this Service Bulletin

None.

3. Installation Drawings Used in the Preparation of this Service Bulletin

None.

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K. Publications Affected

1. Publications:

Publication Chapter-Section

737 FAA Approved Airplane Flight Manual Section 2

737 Flight Crew Operations Manual 1-20, 15-10, 15-20

737 Maintenance Manual 31-51

737 Wiring Diagram Manual 21-33, 27-43

737 Illustrated Parts Catalog 31-11

2. Damage Tolerance Based Structural Inspections:

Boeing has evaluated the repairs and/or changes in this service bulletin for effects on Fatigue

Critical Structure (FCS) and for changes to Damage Tolerance Inspections (DTI) required in the

Maintenance Program. This service bulletin does not affect FCS, therefore DTIs are not necessary.

L. Interchangeability and Intermixability of Parts

Accomplishment of this service bulletin does not affect interchangeability or intermixability of parts.

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2. MATERIAL INFORMATION

A. Material - Price and Availability

None.

B. Industry Support Information

Boeing warranty remedies are not available for the configuration changes given in this service bulletin.

C. Parts Necessary For Each Airplane

1. Kits/Parts

None.

2. Parts and Materials Supplied by the Operator

None.

3. Parts Modified and Reidentified

None.

4. Parts Removed and Not Replaced

None.

D. Parts Necessary to Change Spares

None.

E. Special Tooling - Price and Availability

None.

F. Special Tooling Necessary to do this Service Bulletin

No special tools or equipment are necessary to do the change in this service bulletin. But, maintenance

and overhaul tools in the manuals given in Paragraph 1.J., References, can be necessary. Examine

operator tool supply to make sure all necessary tools are available.

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3. ACCOMPLISHMENT INSTRUCTIONS

A. GENERAL INFORMATION

CAUTION: KEEP THE WORK AREA, WIRES AND ELECTRICAL BUNDLES CLEAN OF METAL

PARTICLES OR CONTAMINATION WHEN YOU USE TOOLS. UNWANTED MATERIAL,

METAL PARTICLES OR CONTAMINATION CAUGHT IN WIRE BUNDLES CAN CAUSE

DAMAGE TO THE BUNDLES. DAMAGED WIRE BUNDLES CAN CAUSE SPARKS OR

OTHER ELECTRICAL DAMAGE.

NOTE: 1. The instructions identified in Paragraph 3.B., Work Instructions and the Figure(s)

give the recommended sequence of steps. The sequence of steps to do this service

bulletin can be changed.

2. Manual titles are referred to by acronyms. Refer to Paragraph 1.J., References, for

definition of the acronyms.

3. Obey all of the warnings and cautions given in the specified manual sections.

4. Refer to the SWPM 20-10-11 and SWPM 20-10-12 for the wire installation procedures,

and SWPM 20-10-19 for the wire separation requirements, as accepted procedures.

5. These work instructions refer to procedures included in other Boeing documents.

When the words "refer to" are used and the operator has an accepted alternative

procedure, the accepted alternative procedure can be used. When the words "in

accordance with" are included in the instruction, the procedure in the Boeing document

must be used.

B. WORK INSTRUCTIONS

1. Get access to the flight compartment.

2. Open the following circuit breakers and install DO-NOT-CLOSE tags:

Circuit Breaker NumberLocation (Panel/Posi- Name

tion)

P6-3 / C16 AURAL WARN C451

LAND LATCH & C129

PRESS WARN

P6-3 / C17

3. Change the W066 wire bundle in accordance with Figure 1, Figure 2, and Figure 4.

4. Remove the INOP markers on the P2-2 panel in accordance with Figure 3.

5. Close the circuit breakers opened in Step 2 above.

6. Do a test for activation of the TAKEOFF CONFIG and CABIN ALTITUDE warning lights:

a. Make sure the following circuit breakers are closed:

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Circuit Breaker Number

Location (Panel/Posi- Name

tion)

P6-3 / C16 AURAL WARN C451

LAND LATCH & C129

PRESS WARN

P6-3 / C17

b. Test the TAKEOFF CONFIG light activation:

(1) Make sure the parking brake is set.

(2) Move the thrust levers to the takeoff position (engines are not running).

(3) Make sure you hear the warning horn.

(4) Make sure the "Red" TAKEOFF CONFIG light on the P2-2 panel is ON.

(5) Move the thrust levers to the idle position.

(6) Make sure the warning horn stops.

(7) Make sure the "Red" TAKEOFF CONFIG light on the P2-2 panel is OFF

c. Test the CABIN ALTITUDE light activation:

(1) Open the forward access door and get access to the Cabin Altitude pressure switch S128.

(2) Remove the vent port screen from the cabin altitude pressure switch S128.

(3) Connect the pitot static system tester (No. 4 Union and O-ring) to the vent port in the

cabin altitude warning switch S128 (737-300/400/500 AMM 34-11-00).

(4) Operate the system by slowly increasing the vacuum and monitor the altimeter.

(5) Make a record of the altitude at which you hear the warning horn.

(6) Make sure you hear the intermittent warning horn at an altitude between 9,000 and 11,000

feet and make sure the "Red" CABIN ALTITUDE light on the P2-2 panel is ON.

(7) Push the switch for the ALTITUDE HORN CUTOUT on the P5-16 cabin pressure control

panel.

(8) Make sure the aural warning horn stops.

(9) Make sure the "Red" CABIN ALTITUDE light on the P2-2 panels stays ON.

(10) Slowly lower the altitude shown to approximately 1,700 feet below the altitude at which

you heard the horn.

(11) Make sure the "Red" CABIN ALTITUDE light on the P2-2 panel goes OFF.

(12) Increase the altitude.

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(13) Make sure the horn is again heard between 9,000 and 11,000 feet.

(14) Make sure the "Red" CABIN ALTITUDE light on the P2-2 panel comes ON.

(15) Decrease the altitude to the ground level.

(16) Make sure the "Red" CABIN ALTITUDE light on the P2-2 panel goes off and the aural

warning horn stops.

(17) Disconnect the pitot static system test equipment.

(18) Install the vent port screen.

(19) Close the forward access door.

7. Return the airplane to a serviceable condition

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FIGURE 1: WIRE BUNDLE W066 WIRE ROUTING

(SHEET 1 OF 1)

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REFERENCES: 737-300/400/500 WDM 21-33-01, 737-300/400/500 WDM 27-43-01.

FIGURE 2: ACTIVATION OF THE CABIN ALTITUDE WARNING AND TAKEOFF CONFIGURATION WARNING

LIGHTS

(SHEET 1 OF 1)

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The step numbers shown below agree with the numbers shown in the circle symbols in the figure. The QTY

numbers shown below are the number of parts necessary for this figure.

FIGURE 3: REMOVE THE INOP MARKERS AT THE L1304 AND L1316 LIGHT ASSEMBLIES

(SHEET 1 OF 2)

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STEP TASK NAME IDENTIFICATION QTY MORE DATA

Refer to SOPM 20-

50-05 as an accepted procedure.

1 Remove MARKER BAC27DCC2769 2

FIGURE 3: REMOVE THE INOP MARKERS AT THE L1304 AND L1316 LIGHT ASSEMBLIES

(SHEET 2 OF 2)

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FIGURE 4: L1304 AND L1316 LIGHT ASSEMBLY REFERENCE

(SHEET 1 OF 1)

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