Revision ‘A’ 04 Oct 2013

DHC-8 (DASH 8)

SERVICE BULLETIN 84-32-122

Landing Gear - Nose Wheel Steering - Addition of Pull Down Resistors

to Pilot Hand Control (PHC) and Rudder Pedal Potentiometer - ModSum

4-126585

This page transmits Revision ‘A’ of Service Bulletin 84-32-122, pages 1 thru

14 dated 04 Oct 2013.

This service bulletin is re-issued in its entirety for the reasons that follow:

- the References section is revised to convey the latest revision of the service

bulletin and engineering documentation

- the Figures 3 and 4 are revised to add a NOTE stating that the figures were

taken from drawing 8Z9652 and to refer to the drawing for additional details.

The Compliance in the previous issues of this service bulletin is not affected

by this revision. No additional rework to the aircraft is introduced by this

revision.

Remove the previous revision of Service Bulletin 84-32-122 and replace with

attached.

Previous issue(s) of Service Bulletin 84-32-122:

Initial issue - Pages 1 thru 14 dated 28 Aug 2013

D

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SERVICE BULLETIN

Customer

Support

ATA SYSTEM: 3251 NUMBER: 84-32-122

SUBJECT: Landing Gear - Nose Wheel Steering - Addition of Pull Down

Resistors to Pilot Hand Control (PHC) and Rudder Pedal

Potentiometer - ModSum 4-126585

1. PLANNING INFORMATION

A. Effectivity

Aircraft Affected:

In-Service: DHC-8 Aircraft Models 401 and 402 Serial Numbers 4001 and

4003 thru 4448.

Production: ModSum 4-123898 will be installed before delivery on

applicable DHC-8 Aircraft at Serial Numbers 4449 and

subsequent.

NOTE: The instructions in this service bulletin are only applicable to the systems

and parts installed at the time of delivery on the aircraft or as changed by

Bombardier Aerospace Service Bulletin(s). Before you do this bulletin,

examine all STC or equivalent action changes to make sure this bulletin

can be completed.

Spares Affected:

None
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B. Reason

Problem: The possibility of uncommanded, un-annunciated and erratic steering

exists with the potential to cause runway/taxiway excursion.

Cause: If there is open circuit between the Pilot Hand Control (PHC) Potentiometer

and the Steering Control Unit (SCU) and/or between the Rudder Pedal

Potentiometer and the SCU, the fault may not detected and not

annunciated on the caution warning panel. With an open circuit in the

wiring between the PHC or Rudder and SCU, the nosewheel may rotate at

a high rate. It may rotate left or right over a 40 ̊ angle for the PHC and 8 ̊

for the Rudder and remain at that angle with the nose wheel not going into

free castor mode.

The root of the problem is inherent to the design of the SCU and test

has shown it takes excessive time for an open circuit to be detected by

the SCU. The voltage drop in the SCU circuitry may not be sufficiently

fast enough before the nose wheel rotates to a severe angle. A

sustained open circuit between the SCU and PHC or Rudder

potentiometer may cause an uncommanded, un-annunciated hard over

steering event. This may lead to loss of directional control and potential

taxiway/runway excursion. The intermittent steering may also occur and

is manifested by erratic steering input signal.

Solution: This service bulletin incorporates ModSum 4-126585.

The ModSum installs a pull-down resistor that effectively trips the PHC or

rudder range monitor, reverting to fail safe free-castor mode, in the event

there is an open circuit between the PHC and rudder pedal potentiometers

and the SCU.

C. Description

The procedures in this service bulletin give the instructions to do the tasks that

follow:

- all aircraft electrical power systems are selected to OFF

- the nose landing gear lock is engaged
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- the main landing gear lock pins are installed thru each main gear and main gear

door mechanism

- access panels 112AR and 122AR are removed

- flight crew oxygen cylinder is removed as necessary

- existing wires from connector pins of connector ends 3251-P1 and 9811-P2 are

removed

- continuity and resistance checks between pins are done before installation of new

harnesses

- new wire harnesses are installed

- continuity and resistance checks of wire harnesses between connector ends

3251-P1 and 9811-P2 are done

- functional test (open circuit test) of the nose wheel steering control system is done

- flight crew oxygen cylinder is installed if removed

- access panels 112AR and 122AR are installed

- close out.

D. Compliance

Bombardier Inc. recommends incorporation of ModSum 4-126585 at the earliest

opportunity unless otherwise directed by the operator’s airworthiness authority.

E. Approval

The technical content of this service bulletin has been approved under the

authority of the Transport Canada Civil Aviation (TCCA) Design Approval

Organization No: DAO #93-Q-02.

This service bulletin does not affect Airworthiness Limitations (AWLs) or Damage

Tolerance Inspections (DTIs).
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F. Manpower

It will take an estimated 5.5 man-hours to complete this service bulletin. The

breakdown of the man-hours is shown in the table that follows:

TASK MAN-HOURS

Job Set-Up 1.00

Procedure 3.00

Test / RTS 1.00

Close-Out 0.50

For any on-site labor assistance, please speak with a Fleet Services representative

for a quote. The Fleet Services group can be contacted via the Q Series Technical

Help Desk by telephone at 416-375-4000 or email at:

thd.qseries@aero.bombardier.com.

G. Material - Price and Availability

The ModKit required to do this service bulletin are listed in the table below:

Operators should submit a purchase order through the Customer Accounts Service

Team (CAST) at Bombardier Aerospace Regional Aircraft division specifying aircraft

serial number(s) to:

Bombardier Aerospace

Customer Accounts Services Team (Mail Stop N11-32)

123 Garratt Blvd.

Toronto

Ontario

Canada M3K-1Y5

Facsimile: (416) 375-3060

Telephone: (416) 375-3920

Facsimile:

International: (416) 375-3334
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European: (416) 373-5966

Americas East: (416) 373-5964

Americas West: (416) 373-5965

Telephone:

International: (416) 375-3706

European: (416) 373-3704

Americas East: (416) 375-3700

Americas West: (416) 373-5888

E-mail addresses:

International: cast.international@aero.bombardier.com

European: cast.europe@aero.bombardier.com

Americas East: cast.americaseast@aero.bombardier.com

Americas West: cast.americaswest@aero.bombardier.com

Kit Number Description

8MK4664 Rework Kit - NWS Addition of Resistor

H. Tooling - Price and Availability

None

I. Weight and Balance

A/C Type and Model Weight (Lb) Arm (Inches)

Moment

(Inches x Lb)

x 0.001

DHC-8 Model 401/402 +0.37 -108.70 -0.04

J. Electrical Load Data

Not affected
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K. Publications Affected

Maintenance Manual PSM 1-84-2 ................................

Wiring Diagrams Manual PSM 1-84-2W ............................

Dash 8 Illustrated Parts Catalogue PSM 1-84-4 ....................

ModSums Manual PSM 1-84-12 ..................................

Weight and Balance Manual (Imperial) PSM 1-84-8 ................

Weight and Balance Manual (Metric) PSM 1-84-8M ..................

L. References

Revision ‘A’ of this service bulletin was prepared to the engineering drawings and

related data that follows:

DRAWING SHEET REV

8MK4664 1 --

8Z9652 1 A

ModSum 4Q126585 Rev. ‘B’

ModSum 4-126585 Rev. ‘B’

ModSum 4Y123898 Rev. ‘B’

ModSum 4-123898 Rev. ‘B’

PCA 44578 Revision 0 (for internal reference only)

2. MATERIAL INFORMATION

A. Parts Required Per Aircraft

(1) Modification Kit 8MK4664-001
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(2) Detailed Kit Content:

Quantity Per Kit

-001

Part Number Description Remarks

3 B0816063-003 Solder Sleeve See NOTE below

14 B0816063-002 Solder Sleeve See NOTE below

23 B0816063-001 Solder Sleeve See NOTE below

1 8Z9652-013 Cable Assy

1 8Z9652-011 Cable Assy

NOTE: These are additional sleeves included in the kit which may be used in the

event existing sleeves are damaged during disassembly.

B. Parts Required to Modify Spares

None

C. Special Tools and Equipment Required

None

D. Existing Parts Accountability

None

3. ACCOMPLISHMENT INSTRUCTIONS

A. Job Set-Up

(1) Placard and select all aircraft electrical power to OFF. Obey all relevant

WARNINGS and CAUTIONS (refer to AMM TASKs 24-00-00-861-802 and

24-00-00-910-801).

(2) Make sure the nose gear ground lock is engaged.

(3) Make sure that lock pins are installed thru each main gear and main gear door

mechanism.

(4) Set wheel chocks in front and behind the landing gear tires.
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(5) Remove access panels 112AR and 122AR (refer to AMM TASK 06-41-00-992-801

for locations and to AMM TASK 53-11-00-000-801 for applicable instructions).

(6) For better access, remove the flight crew oxygen cylinder as necessary (refer to

AMM TASK 35-11-01-000-801 or TASK 35-11-01-000-802).

B. Procedure

(1) Locate connector ends 3251-P1 at the lower right side of the nose compartment

bay and 9811-P2 at RHS fwd pressure bulkhead (refer to Figure 2).

(2) Remove clamps. tie wraps and straps from existing wiring harnesses as

necessary.

(3) Remove the shield pigtails from backshell of connectors 3251-P1 and 9811-P2

and the wires from connector pins of connector 3251-P1 and 9811-P2 as follows

(refer to applicable instructions in WDM 20-12-10-201 and Figure 3):

From Pin Wire Code To Pin

3251-P1 35 W20A-22-6/BLK 9811-P2 A3251-P1 34 W20A-22-6/WHT 9811-P2 B3251-P1 36 W20A-22-6/RED 9811-P2 C3251-P1 27 W21A-22-6/BLK 9811-P2 D3251-P1 28 W21A-22-6/WHT 9811-P2 E3251-P1 29 W21A-22-6/RED 9811-P2 F-

(4) Tape and stow connector end 3251-P1 wire pins 27, 28, 29, 34, 35, 36 and

shield pigtail and connector end 9811-P2 wire pins A, B, C, D, E, F and shield

pigtail for future use.

NOTE: Do not damage or cut wire pins as they will be used for future

re-installation.
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(5) Before installation of the new cable assemblies, do continuity and resistance

checks between the connector pins with an ohmmeter to verify compliance with

the schematic wiring view shown on drawing 8Z9652, POST CONDITION NEW

WIRING.

NOTE: Continuity of a circuit is affected when a resistor is part of a circuit. When

checking continuity across a resistor the value of the resistor must be

observed. Per dwg 8Z9652, resistors R2 and R3 are at 2 megaohms +/-

1% tolerance.

(6) If the resistance exceeds 5 ohms from point to point (open circuit), recheck the

new and reworked wiring to make sure it is terminated to the correct connection,

check the wiring for mechanical damage, loose connector parts, bent pins and

corrosion. Correct the deficiency.

(7) Prior to installation of the new cable assemblies do an electrical continuity

measurement from shield pigtail at 9811-P2 to shield pigtail at 3251-P1 using a

low resistance digital multimeter (four wire bonding meter). Reading should be

less than 100 milliohms. If the reading exceeds 100 milliohms check the shield

continuity across shield splices of the wire.

(8) Insert new cable assembly pins to appropriate connector ends (refer to Figures

2 and 4 and applicable instructions in WDM 20-12-10-201).

NOTE: The individual wire shields are grounded by placing the jumper wire from

the solder sleeves, around the grounding adaptor ring of the backshell

per WDM 20-15-10-401.

(9) Reinstall clamps, tie wraps and straps as necessary to secure the wiring

harnesses (refer to applicable instructions in WDM 20-12-10-201).

NOTE: It is acceptable to increase clamp size to accommodate new cable

assemblies. Do not tie wrap or clamp over the middle of resistors R2 and

R3 due to longer flexible tube and make sure the splices are placed

against rigid surface or area. It is permissible to have end of tube under

clamp.
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(10) After installation, do continuity and resistance checks of the wire harnesses

between connector ends 3251-P1 and 9811-P2 with an ohmmeter to verify

compliance with the schematic wiring view shown on Figure 4, POST

CONDITION NEW WIRING.

NOTE: Continuity of a circuit is affected when a resistor is part of a circuit. When

checking continuity across a resistor the value of the resistor must be

observed. Per dwg 8Z9652, resistors R2 and R3 are at 2 megaohms +/-

1% tolerance.

(11) If the resistance exceeds 5 ohms from point to point (open circuit), recheck the

new and reworked wiring to make sure it is terminated to the correct connection,

check the wiring for mechanical damage, loose connector parts, bent pins and

corrosion. Correct the deficiency.

C. Close Out

(1) Do the functional test (open circuit test) of the nose wheel steering control

system in accordance with the instructions given in drawing 8Z9652.

(2) If removed, install the flight crew oxygen cylinder (refer to AMM TASK

35-11-01-400-801 or TASK 35-11-01-400-802).

(3) Install access panels 112AR and 122AR (refer to AMM TASK 06-41-00-992-801

for locations and to AMM TASK 53-11-00-400-801 for applicable instructions).

(4) Remove all tools and equipment from the work area.

(5) On incorporation of this ModSum, make an entry that conforms to local

regulatory requirements in the applicable logbook(s). Enter component serial

numbers if applicable. Enter this ModSum number only after complete and

functional incorporation of all work defined in this service bulletin.
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Area of Retrofit

Figure 1
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8Z9652-013

8Z9652-011

Area of Retrofit

Figure 2
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Existing Wiring Diagram

Figure 3

NOTE: This Figure was taken from Drawing 8Z9652. Refer to the drawing

for additional details.
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New Wiring Diagram

Figure 4

NOTE: This Figure was taken from Drawing 8Z9652. Refer to the drawing

for additional details.
Jan 2009

SERVICE BULLETIN (SB) --- RECORD OF INCORPORATION

--- Q SERIES DASH 8 AIRCRAFT

To: CMDB Focal

Facsimile: (1) 416 375 4538

E --mail: cmdb.requests@aero.bombardier.com

From:

Company:

Phone: Extn:

Facsimile: Date:

E --mail:

The data that you provide below will help us record the incorporation of this ModSum

and the aircraft effectivity in the maintenance manual.

Operator: Service Bulletin: __________________ Revision: _________

Aircraft Serial Number: Model Number: Date Bulletin Completed:

Aircraft Serial Number: Model Number: Date Bulletin Completed:

Aircraft Serial Number: Model Number: Date Bulletin Completed:

Aircraft Serial Number: Model Number: Date Bulletin Completed:

Aircraft Serial Number: Model Number: Date Bulletin Completed:

Aircraft Serial Number: Model Number: Date Bulletin Completed:

Aircraft Serial Number: Model Number: Date Bulletin Completed:

Aircraft Serial Number: Model Number: Date Bulletin Completed:

Aircraft Serial Number: Model Number: Date Bulletin Completed:

Aircraft Serial Number: Model Number: Date Bulletin Completed:

Aircraft Serial Number: Model Number: Date Bulletin Completed:

Aircraft Serial Number: Model Number: Date Bulletin Completed:

Fax this sheet to (1) 416 375 4538 or Email PDF to:

cmdb.requests@aero.bombardier.com
Feb 2009

SERVICE BULLETIN (SB) --- COMMENT SHEET --- Q SERIES DASH 8 AIRCRAFT

To: SB Focal (Toronto), Bombardier Aerospace Commercial Aircraft

Phone: (1) 416 375 4078 Facsimile: (1) 416 375 4538

E --mail: syed.rizvi@aero.bombardier.com

From:

Company:

Phone: Extn:

Facsimile: Date:

E --mail:

Select appropriate box(es) and add comments or suggestions you would like us to know

that may enhance the quality of our service bulletins.

Service Bulletin: Revision: ModSum:

1. PLANNING INFORMATION

V Effectivity V Reason V Description V Compliance

V Approval V Manpower V Material V Weight and Balance

V Electrical Load V Tooling V References V Publications Affected

2. MATERIAL INFORMATION

V Kit Content V Special Tools/Equipment V Parts to Modify Spares

V Consumables V Disposition of Existing Parts V Other

3. ACCOMPLISHMENT INSTRUCTIONS

V Job Set ---Up V Procedure V Close---Out V Test

V Illustration(s) V Other

4. COMMENTS, REMARKS, SUGGESTIONS

Fax this sheet to (1) 416 375 4538 or Email PDF to:

syed.rizvi@aero.bombardier.com