De Havilland Canada Service Bulletin 84-55-09

TxLtrSB84-55-09Revision‘B’17Feb2023 AS Page1of2 DHC-8 (DASH 8) SERVICE BULLETIN 84-55-09 Empennage – Horizontal Stabilizer – Rear Spar Elevator Powe r Control Unit (PCU) Brackets (Fittings) Replacement and Inspection of the E levator Front Spar Web – ModSum 4-113983 This page transmits Revision ‘B’ of Service Bulletin 84-55-09, pages 1 thru 34, dated17Feb2023.

Thisservicebulletinis re-issuedinitsentiretyforthe re asonsthatfollow:

– The Description Part – B (Rectification) sectionisrevisedtoaddthesteps relatedtotheremovalandinstallationofelevatortorquet ubesandhydrauliclines – The References sectionisrevisedtoconveythelatestrevisionoftheservi ce bulletinandengineeringdocumentation – The Procedure Part B – Rectification sectionisrevisedtoaddthe stepsrelatedto theremoval andinstallationofelevatortorque tubes andhy drauliclines – Updatedthephonenumbersandtheaddress.

The Compliance in the previous issues of this service bulletin is not affected by thisrevision.Noadditionalreworktothe aircraftisintro ducedbythisrevision.

Remove the previous revision of Service Bulletin 84-55-09 a nd replace with attached.

PreviousissuesofServiceBulletin84-55-09:

Initialissue–Pages1thru32dated07Jun2018 Revision‘A’–Pages1thru32dated10Jan2020

SERVICE BULLETIN 84-55-09 TxLtrSB84-55-09Revision‘B’17Feb2023 AS Page2of2 This Page Intentionally Blank

S.B. 84-55-09 Page 1 of34 07 Jun 2018 AS Revision ‘B’17 Feb 2023

SERVICEBULLETIN ATASYSTEM: 5510 NUMBER: 84-55-09

DE HAVILLAND AIRCRAFTOFCANADALIMITED(DHC)CONSIDERS

URGESOPERATORSTOPROMPTLYEVALUATETHECONTENTS

THISSERVICEBULLETINTOBEPARTICULARLYSIGNIFICANTAND SUBJECT: Empennage–HorizontalStabilizer–RearSparElev atorPowerControl Unit (PCU) Brackets (Fittings) Replacement and Inspection ofthe ElevatorFrontSparWeb–ModSum 4-113983

1. PLANNING INFORMA TION A. Effectivity Aircraft Affected:

In-Service: DHC-8 Aircraft Models 401 and 402 Serial Number s 4001, 4003 thru 4580.

Production: ModSum 4-180055 will be installed before deliv ery on applicable DHC-8 Aircraft at Serial Number 4581 and subsequent.

NOTE: The instructions in this service bulletin are only applicab le to the systems and parts installed at the time of delivery on the aircraft or as changed by DHC Service Bulletin(s). Before you do this bulle tin, examine all STC or equivalent action changes to make sure thi s bulletin can be completed.

SERVICEBULLETIN 84-55-09 S.B. 84-55-09 Page 2 of34 07 Jun 2018 AS Revision ‘B’17 Feb 2023 Spares Affected:

The following is a list of spares affected by this change. Review spares and procurement systems to determine the existence of any listed parts. See Paragraph 2.D., Existing Parts Accountability,fordisposition.

PartNumber Description 85517347-001 PCU FTG Assy, LH 85517347-002 PCU FTG Assy, RH B. Reason Problem: In five separate events, an operator has reported cracked elevator PCU brackets(fittings).Inonecasethecrackgrowthresultedi ndetachmentof the PCU fitting during pushback.

AdetachedPCUfittingcanimpedeelevatormovement.Multip ledetached PCUfittingsintheaircraftcancauselossofelevatorcontr ol.Therearesix fittings per aircraft supporting six elevator PCUs, four ofwhich are active and twoare standby.

There have also been tworeports of Elevator Front Spar cracking.

Cause: Current PCU fittings do not account for force-fightl oads from mis-rigged elevator PCUs. Force-fight loads from mis-rigged elevatorPCUs, when superimposed with fitting flange installation preload maybe sufficient to cause the fatigue cracking.

Solution: ThisservicebulletinintroducesModSum4-11398 3.TheModSuminspects and replaces any existing PCU fittings with redesigned PCU fittings, if found cracked.

Redesignedfittingshaveimprovedfatiguelifewhensubjec ttohigherthan anticipated force fightand installation pre-loads.

This SB also conducts inspection of the elevator leading edge front spar and H-stab rear spar in the areas adjacent to PCU fittings andcollects sampling data.

SERVICEBULLETIN 84-55-09 S.B. 84-55-09 Page 3 of34 07 Jun 2018 AS Revision ‘B’17 Feb 2023 C. Description The procedures in this service bulletin give the instructions todothe tasks that follow:

- The nose landinggear lock is engaged

- Themainlandinggearlockpinsareinstalledthrougheachm aingearandmaingear doormechanism

- Pressure from the hydraulic systems is removed

- Aircraft electrical power is removed

- Wheel chocks are setin front and behind the landing gear tires

- Work scissor lift(s) or platforms are set as required to gain access to horizontal stabilizer

- Access panels are removed to gain access to the elevatorPCUfittings

- Elevator leading edge panels removed as necessary

- If necessary, elevators are removed.

Part–A(Inspection –ForCracks)

- PCU’s are disconnected, if necessary

- Elevator PCU fittings are inspected forcracks ordamages

- Horizontal stabilizer rear spar and elevator front spar around the PCU fittings are visually inspectedforcracking

- Ifcracksordamagearefoundonthehorizontalstabilizerr earsparortheelevatorfront spar around the PCU fittings, contact the Q Series TechnicalHelp Desk by telephone at 1-855-310-1013 or 1-647-277-5820, email at: thd@dehavilland.com for approved disposition/action/repair

- Ifnocracksordamagearefound,allsixPCUsareriggedand closeout iscompleted

- ResultsandfindingsarereportedtoDHCperTableattheend oftheservicebulletin.

SERVICEBULLETIN 84-55-09 S.B. 84-55-09 Page 4 of34 07 Jun 2018 AS Revision ‘B’17 Feb 2023 Part–B(Rectification)

- If cracks ordamage are found only on PCU fittings, elevators are removed

- Elevator PCU’s are removed, if required

- Elevator torque tubes are removed, if required

- Hydrauliclines are removed, if required

- Cracked PCU fittings are replaced with redesigned fittings

- The hydraulic lines are installed, if removed

- The elevatortorque tubes are installed, if removed

- Removed PCU’s are installed

- Elevators are installed

- Systems functional tests are completed

- Close-out

- ResultsandfindingsarereportedtoDHCperTableattheend oftheservicebulletin.

D. Compliance De Havilland Aircraft of Canada Limited highly recommends that ModSum 4-113983 be incorporated at the earliest opportunity unless otherwise directed by the operator’s airworthiness authority.

Transport Canada Airworthiness Directive CF-2018-34 has been issued.

E. Approval The technical content of this service bulletin has been approved under the authority of the Transport Canada Civil Aviation (TCCA) Design ApprovalOrganization No: DAO #93-Q-02.

This service bulletin does not affect Airworthiness Limitations (AWLs) or Damage Tolerance Inspections (DTIs).

SERVICEBULLETIN 84-55-09 S.B. 84-55-09 Page 5 of34 07 Jun 2018 AS Revision ‘B’17 Feb 2023 F. Manpower PartA– Inspection It will take an estimated 13.00 man-hours to complete Part A – Inspection given in the ACCOMPLISHMENT instructions in this service bulletin. The breakdown of manhours is shown in the table that follows:

TASK MAN-HOURS Job Set-Up 2.00 Procedure in PartA 4.00 Test / RTS 5.00 Close-Out 2.00 NOTE: Man hours in Procedure – Part B are inclusive to PCU bracket replacements and additional man-hours for repair/replace ment of elevator/H-stab due to structural cracks are not included.

PartB– Rectification It will take an estimated 18.00 man-hours to complete PART B – Rectification given in the ACCOMPLISHMENT instructions in this service bulletin. The breakdown of man -hours is shown in the table that follows:

TASK MAN-HOURS Job Set-Up 1.00 Procedure in PartB 10.00 Test / RTS 5.00 Close-Out 2.00 G. Material–PriceandAvailability The full Modification Kit required to do this service bulletin is listed in the table below for reference only:

SERVICEBULLETIN 84-55-09 S.B. 84-55-09 Page 6 of34 07 Jun 2018 AS Revision ‘B’17 Feb 2023 KitNumber Description 8MK4837-001 Kit – PCU Fitting Replacement, HSTAB NOTE: Whole 8MK4837-001 kit is not procurable. It is intended thatoperators order fittings and shims as required after they find crackedfittings.

NOTE: Please note that the full Modification kit required to do this service bulletin is listed in the above table for reference only. Refer to section

2.A. and order part quantities sufficient to replace fittings which have cracked.

Operators should submit a purchase order through the Customer Response Center (CRC) to the Customer Accounts Service Team (CAST) at DHC specifying aircraft serial number(s). Submit the purchase orderto:

De Havilland Aircraftof Canada Limited Material Services 5800 Explorer Drive Mississauga Ontario Canada L4W-5K9 DHCPhone Numbers :

North America:Toll Free: 1-855-310-1013 or Direct: 1-647-277-5820 DHC Emails:

Parts: Europe, Middle East, Africa, and Russia: emear.parts@dehavilland.com Americas and Rest of World: parts@dehavilland.com

SERVICEBULLETIN 84-55-09 S.B. 84-55-09 Page 7 of34 07 Jun 2018 AS Revision ‘B’17 Feb 2023 H. Tooling–Price andAvailability For tool rentals, contact the Customer Response Center (CRC ) Kits Team at 1-855-310-1013 or1-647-277-5820 or email: kits@dehavilland.com.

I. WeightandBalance NOTE: Weight and Balance changes are only required if replacing any fitting.

A/CType and Model Weight(Lb) Arm(Inches) Moment (InchesxLb) x0.001 DHC-8 Model401,402 Kit -8MK4837-001 8Z10178-001 PCU #1(Y- 90.50) +0.13 1049.72 0.14 DHC-8 Model401,402 Kit -8MK4837-001 8Z10178-001 PCU #2(Y- 82.50) +0.13 1049.72 0.14 DHC-8 Model401,402 Kit -8MK4837-001 8Z10178-001 PCU #3(Y- 70.50) +0.13 1049.72 0.14 DHC-8 Model401,402 Kit -8MK4837-001 8Z10178-002 PCU #1(Y+90.50) +0.13 1049.72 0.14 DHC-8 Model401,402 Kit -8MK4837-001 8Z10178-002 PCU #2(Y+82.50) +0.13 1049.72 0.14 DHC-8 Model401,402 Kit -8MK4837-001 8Z10178-002 PCU #3(Y+70.50) +0.13 1049.72 0.14 J. ElectricalLoadData Not affected

SERVICEBULLETIN 84-55-09 S.B. 84-55-09 Page 8 of34 07 Jun 2018 AS Revision ‘B’17 Feb 2023 K. PublicationsAffected AircraftMaintenance Manual PSM 1-84-2........................

AircraftIllustrated Parts Catalog PSM 1-84-4.....................

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

L. References Revision ‘B’ of this service bulletin was prepared to the engineering drawings and relateddatathat follows:

DRAWING SHEET REV 8MK4837 1 -- 8Z10178 1 -H 8Z10178 2 -C Tool Drawing8Z10178-001-58 ModSum 4Q113983 Rev.‘M’ ModSum 4-113983 Rev. ‘N’ Related ModSum 4-180055 Rev. ‘D’ PCA 46717 Revision 04 (for internal reference only) Transport Canada Airworthiness Directive CF-2018-34 effective 2018-12-31.

2. MATERIAL INFORMA TION A. PartsRequiredPerAircraft

(1) Modification Kit 8MK4837-001 for reference only (See Note below).

SERVICEBULLETIN 84-55-09 S.B. 84-55-09 Page 9 of34 07 Jun 2018 AS Revision ‘B’17 Feb 2023

(2) Detailed Kit Content:

Quantity PerKit -001 PartNumber Description Remarks Ref 8Z10178 Retrofit Drawing only 6 CSP469A-115-340 Shim 6 85517244-101 Shim 3 85517347-004 PCU FTG Assy, RH 3 85517347-003 PCU FTG Assy, LH NOTE: Kit 8MK4837-001 is not procurable. Quantity is shown for replacement of all PCU fittings.Replace only fittings which have cracked.

Listed drawings that are required to complete the kits abovecan be requested by writing tothe following email address:

dwg.request@dehavilland.com

(3) In addition to the above part(s), the following material(s) are required for the completion of this service bulletin and may be procured as single items from DeHavilland orpurchaseddirectlyfrom industry sources.

Each consumable product listed in the table below is given its own unique Product ID Number. The number is used to identify a particular recommended product, the specifications and the trade names any of whichcan be used unless specified otherwise (refer to PSM 1-84-18, Consumab le Products Manual).

SERVICEBULLETIN 84-55-09 S.B. 84-55-09 Page 10 of 34 07 Jun 2018 AS Revision ‘B’17 Feb 2023 Consumable ProductID Number Qty.PerAircraft Description Remarks 06-02 A/R Sealant, Corrosion Inhibiting DHMS S3.06 C-80 Alternative Proseal P/S 870 C-12 Sealant to MIL-PRF-81733 05-01 A/R Adhesive,Room Temperature Curing, Polychloroprene Rubber-Based DHMS A6.11Type 1 Class 1 07-02 A/R Primer, Fluid-Resistant,Chromate Epoxy(F19) DHMS C4.01 Type 2

(4) The following parts are required for the completion of this service bulletin and may be procured as single items from DeHavilland or purchased directly from industry sources.

Qty.

PerAircraft PartNumber Description Remarks (AlternateParts) 24 B0206017TP8 Collar HST1488TP-8 12 B0206016CY8 Collar HST1479CY-8 72 B0206016CY5 Collar HST1479CY-5 12 B0206003AG8-9 Pin HST12AG8-9 12 B0206003AG8-6 Pin HST12AG8-6 12 B0206002AG8-4 Pin HST11AG8-4 72 B0206001AG5-6 Pin HST10AG5-6 NOTE: Alternate part numbers are provided per EO 7336 in the Table and not shown in the kitdrawing.