# D

S.B. A84-57-25 Page 1 of 18 20 Jul 2011 PM 

# ALERT SERVICE BULLETIN
Customer Support
ATA SYSTEM: 5713 NUMBER: A84-57-25 THIS SERVICE BULLETIN IS BEING SENT TO EACH AFFECTED OPERATOR. IF THE OPERATOR IF THE OPERATOR HAS SOLD AIRCRAFT OR TRANSFERRED AFFECTED SPARES WITHIN THE LAST SIX MONTHS, THIS SERVICE BULLETIN SHOULD BE FORWARDED TO THE NEW OWNER UNLESS CONFIRMATION HAS BEEN RECEIVED THAT BOMBARDIER AEROSPACE REGIONAL HAS LEASED AIRCRAFT, THIS SERVICE BULLETIN SHOULD BE FORWARDED TO THE LESSEE.

AIRCRAFT HAS INCLUDED THE NEW OPERATOR ON THE DISTRIBUTION LIST.

SUBJECT: Wings - Front Spar to Fuselage Attachment - Special Inspection of Barrel Nuts Used on Primary Attachment Joints

1. PLANNING INFORMATION
A. Effectivity Aircraft Affected: In-Service: DHC-8 Aircraft Models 401 and 402 Serial Numbers 4001 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: The following is a list of spares affected by this change. Review spares and procurement systems to determine the existence of any listed parts.

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 2 of 18 20 Jul 2011 PM Part Number Description

DSC228-16 Barrel Nut B. Reason Problem: Service Bulletin A84-57-18 and A84-57-19 were previously issued to advise Operators of a potential quality concern with the barrel nuts securing the wing front spar to the fuselage. During scheduled maintenance, an Operator found cracks in the barrel nut and cradle at one of the four front spar locations. Investigation determined that the cracks were due to hydrogen embrittlement, however the root cause could not be determined. It was believed that the problem was restricted to a batch of 166 barrel nuts from one supplier. This batch is identified with the marking LH7940T SPS 01, where 01 identifies the batch (All barrel nuts from this batch will also show a yellow dot identifier). As a precautionary measure, Alert Service Bulletin A84-57-18 was issued for Operators to perform a one time special inspection of the fittings at the forward wing to fuselage attachment points, to ensure the bolts are properly torqued and the barrel nuts have no signs of cracking. Barrel nuts from the suspect batch, were permitted to remain in-service, provided that the bolt preload was correct and the barrel nuts had no cracks. Replacement of suspect barrel nuts was required within 6,000 flight hours. After conducting an inspection per A84-57-18, one Operator has reported finding cracked barrel nuts at three of the four wing front spar attachment locations on one aircraft. All three barrel nuts were from the suspect batch. In one case, the attachment bolt was found to have a loss of preload, however in the remaining two cases the bolt preload was correct but the cradles were cracked. As a precautionary measure the Operator ran a piece of lockwire around the barrel nut and discovered it was snagging. Cracks were then confirmed using a borescope. As a result of those findings, Alert Service Bulletin A84-57-19 was issued, requiring Operators to check that all front spar attachment bolts are properly preloaded and to perform a borescope inspection of barrel nuts from the suspect batch of yellow dot barrel nuts. All yellow dot barrel nuts were removed from service as mandated by AD CF-2008-11R. During scheduled maintenance, an Operator found cracks in a blue dot barrel nut and cradle at one of the four spar locations. The three remaining locations were checked and in each case the cradles and the barrel nuts were not cracked. Preliminary investigation has determined that the cracks were most likely due to hydrogen embrittlement. The finding was identified in an aircraft outside the applicability of Alert Service Bulletin A84-57-19 and respective TC and FAA Airworthiness Directives.

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 3 of 18 20 Jul 2011 PM Operator’s doing the inspection according to AOM 466 have found two other barrel nut failures, and two instances of loose PLI washers. Due to the importance of these barrel nuts, aircraft need to be inspected in order to determine whether the issue is batch related to ensure structural integrity. Solution: As a result, Alert Service Bulletin A84-57-25 has been issued requiring Operators to check that all front spar attachment bolts are properly preloaded and to do a borescope inspection of barrel nuts. C. Description The procedures in this service bulletin give the instructions to do the tasks that follow: - wing root access panels are opened - four barrel nuts are inspected visually and with a borescope at the wing to fuselage front spar joint - the PLI washers are checked to make sure they are pre-loaded - if cracked or damaged barrel nuts are found, the barrel nut, bolt and PLI washer at that location are replaced - the inspecton is repeated at specific intervals. - Log entries are made and findings are reported to Bombardier D. Compliance Alert Service Bulletin A84-57-25 is applicable. Alert Service Bulletin A84-57-18 is superceded by Alert Service Bulletin A84-57-19. Alert Service Bulletin A84-57-19 is still effective. If the bolt preload is maintained and barrel nuts have no cracks or damage, they may remain in service.

NOTE: Operators that have previously conducted inspections according to instructions in SB A84-57-19 since June 01, 2011 as referenced by AOM 466 and have either confirmed the barrel nut is serviceable or replaced the hardware, need not do the initial inspection specified in this Alert Service Bulletin. Aircraft greater than 1900 total flight hours or more than 1 year old, whichever is less: Initial inspection within 100 flight hours or 10 days whichever comes first, is required. Repeat inspection within 2000 flight hours or 1 year, whichever comes first, after the initial inspection, is required.

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 4 of 18 20 Jul 2011 PM Aircraft with less than 1900 total flight hours or less than 1 year old, whichever is less: Initial inspection within 2000 total flight hours or 1 year old, whichever comes first, is required. Repeat inspection within 2000 flight hours or 1 year, whichever comes first, after the initial inspection, is required. 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). F. Manpower It will take an estimated 7 man-hours to complete PART A of the ACCOMPLISHMENT INSTRUCTIONS in this service bulletin. The breakdown of the man-hours is shown in the table that follows: TASK MAN-HOURS Job Set-Up 2.00 Procedure 3.00 Test / RTS 0.00 Close-Out 2.00 It will take an estimated 8 man-hours to complete PART B of the ACCOMPLISHMENT INSTRUCTIONS in this service bulletin if required. The breakdown of the man-hours is shown in the table that follows: TASK MAN-HOURS Job Set-Up 2.00 Procedure 4.00 Test / RTS 0.00 Close-Out 2.00

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 5 of 18 20 Jul 2011 PM G. Material - Price and Availability The parts detailed in Paragraph 2.A. may be obtained from the Spares AOG Desk. 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 H. Tooling - Price and Availability None I. Weight and Balance None J. Electrical Load Data Not affected K. Publications Affected None L. References The initial issue of this service bulletin was prepared to the engineering drawings and related data that follows: AOM # 466 PCA 43791 Revision 0 (for internal reference only) Transport Canada Airworthiness Directive Pending

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 6 of 18 20 Jul 2011 PM 2. MATERIALINFORMATION A. Parts Required per Aircraft (1) Detailed Parts List:
Quantity per Location Part Number Description Remarks
1 DSC228-16 Barrel Nut 1 MS21250-16038 Bolt 1 62524-16-85.5 PLI Washer
NOTE: This service bulletin is self-contained (illustrated). No drawings will be supplied. (2) 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 Bombardier Aerospace Regional Aircraft or purchased directly from industry sources. Addresses of manufacturers and suppliers not shown below are listed in either Maintenance Manual Chapter 20 or in Structural Repair Manual Chapter 51 or, for 400 Series Aircraft, in Consumable Products Manual PSM 1-84-18.

Part Number Qty. Per Aircraft Description Remarks DHMS S3.06 1/2 Quart Type I Class C Sealant MIL-C-16173 1/2 Quart Corrosion Preventive Compound F13, Type 2

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 7 of 18 20 Jul 2011 PM B. Parts Required to Modify Spares None C. Special Tools and Equipment Required Borescope equivalent to: ITI (Instrument Technology Inc.) Model 123010-40, (40 degrees with right angle adapter, 10mm diameter 60 cm long) OR Fiberscope equivalent to: ITI (Instrument Technology Inc.) Model 127006, (6mm diameter, 1.5 cm long) OR Borescopes or Fiberscopes equivalent to those in kit PWC 37711 (for engine inspections) Equipment for Eddy Current Inspection: Refer to Nondestructive Testing Manual PSM 1-84-7A Part 6 TASK 51-00-01-250-801 Paragraph 8 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 TASK’S 24-00-00-861-802 and 24-00-00-910-801). (2) Make sure that lock pins are installed thru each main gear and main gear door mechanism. (3) Make sure the nose gear ground lock is engaged. (4) Set up the work platforms or ladders as required next to the fuselage under the wing area to gain access to the access panels and inspection area. Make sure the work platforms or ladders are electrically grounded (refer to Figure 1). (5) Refer to AMM TASK 06-41-00-992-803 and open the following access panels:

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 8 of 18 20 Jul 2011 PM LOCATION ACCESS PANELS

Left Wing 261CT, 261FT and 263AL Right Wing 261LT, 261HT and 264AR B. Procedure

Part A - Inspection of Barrel Nut Assemblies (1) Refer to Figure 1 and Figure 2 at Yw42 port and starboard, check that the inboard and outboard bolts are still pre-loaded using the method in step (4) of AMM TASK 20-10-11-400-801. Attempt to turn ring (reference Figure 2-Item 14) in each PLI washer under head of bolt. (2) If ring can be rotated, remove and replace all hardware (except saddle washer and retainer) at that location only, using replacement instructions in Part B before next flight. (3) If preload is maintained, visually inspect the barrel nut / cradle at each of the four locations shown in Figure 1. See barrel nut / cradle assembly in Picture1 and Picture 2. Use a strong light and borescope. If barrel nut is cracked, as shown in Picture 1, or has evidence of pitting and / or corrosion, replace all hardware except saddle washer and retainer before next flight. If the cradle is cracked, replace all hardware except saddle washer and retainer before next flight. Report details to Bombardier Technical Help Desk and order required parts from the Spares AOG Desk. Any new hardware is to be inspected commencing one year after entry into service or 2000 flight hours whichever is less. After initial inspection hardware is to be inspected repeatedly every year or every 2000 flight hours whichever comes first. (4) Complete the enclosed inspection form with inspection results and submit to the Technical Help Desk Part B - Replacement Procedure for Barrel Nut Assemblies (5) Make sure the aircraft is in a stable symmetric condition either on jacks or gear but not a combination of the two prior to proceeding with the removal of any bolts. (6) Refer to AMM TASK 57-11-01-000-801 and lift the weight of LHS #1 engine to relieve wing twist when replacing the bolts/barrel nuts at the LHS attachment points. Lift the weight of RHS #2 engine to relieve wing twist when replacing the bolts/barrel nuts at the RHS attachment points. CAUTION: ONLY ONE TENSION BOLT/BARREL NUT IS TO BE REPLACED AT A TIME. DO NOT LOOSEN OR REPLACE MORE THAN ONE BOLT/BARREL NUT AT A TIME.

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 9 of 18 20 Jul 2011 PM (7) At each of the affected barrel nut locations, remove bolts and all associated hardware and retain for submission to Bombardier for analysis. (8) Do an eddy current check on the bore pad and radius of the fittings per Figure 4 to ensure no cracks prior to installing new hardware. Refer to Non Destructive Testing Manual PSM 1-84-7A Part 6 TASK 51-00-01-250-801 and calibrate machine with ferrous coupon detailed in paragraph 8.A.(8). (9) Visually inspect the saddle washer and retainer for wear and replace if required. NOTE: No damage or wear is acceptable on the hardware. If any signs of damage/wear is found the hardware must be replaced. (10) Replace hardware at the forward tension fitting (bolt/barrel nut, PLI washer) at Yw42 immediately after removing damaged hardware. Change saddle washer and retainer only if required. Do not leave any bolts or nuts out and continue with any other type of work to the aircraft. (11) Refer to Figure 3 and apply F13, Type 2 corrosion peventive compound to the shank of the affected bolts. Do not apply compound to threads of the bolts. (12) Refer to Figure 3 and apply F13, Type 2 corrosion peventive compound to the seating surface of the barrel nut. Do not apply compound to areas of the barrel nut other than the seating surface. (13) Refer to Figure 3 and apply Fayseal as shown. (14) Determine required preload from AMM Chapter 20-10-11 and install new hardware. C. Close Out (1) Refer to applicable steps in AMM TASK 57-11-01-400-801 and lower the engine(s) to the nacelle(s). (2) Replace removed access panels. (3) Remove all tools and equipment from the work area. (4) On completion of this service bulletin, make the following entry in the appropriate logbooks: “Service Bulletin A84-57-25 accomplished.”. If the inspection procedure from Alert Service Bulletin 84-57-19 (as referenced in AOM 466) was used for the initial inspection (conducted since June 2011), it is acceptable to reference the airline work order in the logbook.

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 10 of 18 20 Jul 2011 PM Please send results to the Technical Help Desk in Toronto at telephone (416) 375--4000 or facsimile (416) 375--4539 or e--mail: thd.qseries@aero.bombardier.com HOURS / CYCLES NO FINDINGS

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 11 of 18 20 Jul 2011 PM NUT

CRACK I.D. DOT (if present)

Picture 1

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 12 of 18 20 Jul 2011 PM Picture 2

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 13 of 18 20 Jul 2011 PM Picture 3PART MARKING MAY BEVISIBLE ON THE FACE OFTHE CRADLE

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 14 of 18 20 Jul 2011 PM Figure 1

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 15 of 18 20 Jul 2011 PM View Looking Aft on Front Spar (LHS shown, RHS opposite) Figure 2 Barrel Nuts Tension Bolt Attachment Yw24
Tension Bolt Attachment Inboard Yw42
Tension Bolt Attachment Outboard Yw42
FAYING SURFACE SEAL WITH DHMS S3.06 TYPE I CLASS C SEALANT PER STRUCTURAL REPAIR MANUAL CHAPTER 51-23-00 BETWEEN SADDLE WASHER AND CHANNEL FITTING.

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 16 of 18 20 Jul 2011 PM

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 17 of 18 20 Jul 2011 PM F13 and Sealant Application Figure 3 F13 ON BOLT SHANK

F13 ON SEATING SURFACE FAY SEAL UNDER SADDLE WASHER PLI WASHER OMITTED FOR CLARITY

### ALERT SERVICE BULLETIN A84-57-25

S.B. A84-57-25 Page 18 of 18 20 Jul 2011 PM Figure 4 2Jan 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.comFeb 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 VApproval V Manpower V Material VWeight and Balance V Electrical Load VTooling 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 VTest 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