# BAE Systems Inspection Service Bulletin ISB.53-249: No revision named - Rights: © BAE Systems. Filed by the FAA in regulations.gov docket FAA-2024-1478; AD 2024-17-06 incorporates this document by reference. Not covered by OpenAirDocs’ CC0 dedication. - Document: [BAE Systems Inspection Service Bulletin ISB.53-249](https://openairdocs.org/service-documents/bae-systems/isb53-249.md) - Title as filed: ISB 53-249 R0 - Pages: 20 - PDF: https://openairdocs.org/files/sha256/d1/c7/d1c7841abe904d5baae3186c608dfe3a797a1cd4ba3191535297c62b6ebbca0e - Page: https://openairdocs.org/service-documents/bae-systems/isb53-249/file/d1c7841abe90 ## Text This text is OCR from a scan. OCR can misread letters and numbers. Each page's text from the PDF; open the PDF at a page with #page=N. ### Page 1 (OCR) BAE SYSTEMS (Operations) Limited, Prestwick International Airport, Ayrshire, KA9 2RW, Scotland. INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT TITLE: FUSELAGE - CENTRE FUSELAGE - TO INSPECT FORWARD RIB O LONGERON 1.Planning information A.Effectivity (1) Aircraft Aircraft affected by this inspection are defined below:- BAe 146 Series 301. AlL BAe 146 100, 200, 300 Series. ALL AVRO 146-RJ70, RJ85, RJ100 Series. B. Reason An operator recently reported, during routine maintenance, cracking on the radius of the Rib 0 Forward Longeron at Frame 26. The cracking initiated close to a local blend in the radius. Failure of a Rib O Forward Longeron could result in loss of continuity across the wing box, causing re-distribution of loading into the fuselage skin or the adjacent Rib 1 longerons. Such re-distribution if not detected and corrected, could result in failure of the fuselage skin, leading to rapid decompression and potential loss of the aircraft. C.Description This Inspection Service Bulletin (ISB) requires a one-off visual and high frequency eddy current inspection of the radius of the Rib O Forward Longeron at Frame 26. D. Compliance The technical content of this ISB is the subject of UK CAA Airworthiness Directive consultation. Accomplish the instructions in para.2.C within 6 months of publication of this ISB. Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 1 of 20 Printed in England ### Page 2 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT E. ApprovaL The technical content of this document is approved under the authority of the DOA Ref.UK.21J.0047. The technical content of this document is approved under the authority of the UK CAA design organisation approval reference: AD/1852/05. F. Manpower To inspect as defined in para.2.C - 2.0 man-hours. This man-hour estimate does not include time for gaining access to, or cleaning, the inspection area, paint removal and paint re-instatement. G.Materials - cost and availability None. H.Tooling 10x Magnifier High Frequency Eddy Current inspection equipment. Inspection light Metallic straight edge (minimum 6 in. (152.4mm.)) Mirror Non-metallic scraper. I.Weight and balance Not applicable. J.References Aircraft Maintenance Manual, Chapters 06-40-00, 20-10-10, 20-10-11, 20-10-12, 20-20-00. Test Instrument manufacturer's handbook. Structural Repair Manual, Chapter 51-23-00. Non-Destructive Testing Manual, Part 1, 20-00-00, Part 6, 20-00-00, 20-06-00. K.Publications affected Not applicable. Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 2 of 20 Printed in England ### Page 3 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT L.Electrical load data Not applicable. M.Software Accomplishment Summary Not applicable. N.Aircraft Noise Levels Not applicable. Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 3 of 20 Printed in England ### Page 4 (OCR) BAE SYSTEMS BAe 146 SERIES/AUR SERVE SERES AIRCRAFT This Page Is Intentionally Left Blank. Date: 25-AUG-2023 Revision: Initial issue page 4 of 2l Printed in England ### Page 5 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT 2.Accomplishment instructions A. General WARNING: WHENEVER ANY PART OF THE MAIN OR ASSOCIATED CONTROL SYSTEM IS DISMANTLED, ADJUSTED, REPAIRED OR RENEWED, THAT PART OF THE SYSTEM WHICH HAS BEEN DISTURBED SHALL BE A SECOND INDEPENDENT INSPECTION FOR SECURITY OF LOCKING DEVICES, FULL AND FREE MOVEMENT, DIRECTION AND TENSION CHECKS. ACCEPTABLE MEANS OF COMPLIANCE M.A. 402 (a) TO EASA PART M, OR TO AN EQUIVALENT NATIONAL STANDARD. (1) The following abbreviations are used within this document:- AMM - Aircraft Maintenance Manual jaw - in accordance with ISB - Inspection Service Bulletin LH - Left Hand RH - Right Hand SRM - Structural Repair Manual. NTM - Non-Destructive Testing Manual. (2) Observe all WARNINGS and CAUTIONS appearing in the AMM referred to in this ISB. (3) Restore protective treatment as required, using epoxy primer (Material No.16-580) and polyurethane top coat grey (Material No. 16-584). B.Preparation (1) Refer to AMM 06-40-00. Remove access panels 281AT, 281AZ, 281BT, 281CT, 282AZ, 282BT, 282CT. (2) Gain access to the Rib O Forward Longeron. (3) Remove sealant and clean the LH and RH edge of the Longeron, to allow the straight edge to be located (Ref. Drawing 1). - Refer to AMM 20-20-00. Use an approved cleaner and a non-metallic scraper. (4) Remove primer and paint from the radius edge and flanges of the LH and RH sides of Rib O Forward Longeron iaw AMM 20-10-10 (Ref. Drawing 1). Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 5 of 20 Printed in England ### Page 6 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT C. Inspection (1) Refer to Drawing 1. Perform a detailed inspection of the radius edge and flanges of the LH and RH sides of Rib O Forward Longeron for evidence of rough edges, nicks, or visible cracking. - Use 10x magnification and a strong light and mirror as required. (2) Refer to Drawing 1. Inspect for evidence of blending or undercutting in the radius and flanges of the LH and RH sides of Rib O Forward Longeron. - Use a metallic straight edge (minimum 6 inches (152.4 mm)) NOTE: Blending or undercutting is present if a gap is visible between the straight edge and the edge of the longeron. (3) Refer to Appendix 2 inspection of the radius edge. Perform a high frequency eddy current (4) Before further flight, report any cracking, surface defects, blending or undercutting found to BAE Systems Repair Design Office (raengliaisonabaesystems.com) and await further instruction. Use a copy of the Inspection Report form in Appendix 1. Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 6 of 20 Printed in England ### Page 7 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT FRAME 29 REAR SPAR (REF) FRAME 26 FRONT SPAR (REF) RIB 0 FORWARD LONGERON FWD FRAME 24 FRAME 25 FRAME TYPICAL 26 FWD CAREFULLY PLACE THE STRAIGHT EDGE ALONG THE EDGE STRAIGHT EDGE RADIUS OF THE LONGERON TOWARDS THE RADIUS. MINIMUM LENGTH 6.0 in. (152.4 mm) DO NOT PUSH THE END OF THE STRAIGHT EDGE INTO THE RADIUS. FLANGE IF THERE IS EVIDENCE OF BLENDING OR UNDERCUTTING ALONG THE EDGE THEN REPAIR ACTION MAY BE REQUIRED. INSPECT THE RADIUS ON BOTH SIDES OF THE LONGERON. VIEW ON ARROW 'C' POSSIBLE BLEND OR UNDERCUT STRIP PAINT AND PRIMER IN THIS AREA ON THE FLANGE AND RADIUS EDGE ON BOTH SIDES OF THE LONGERON N5324901 INSPECTION OF LH AND RH RIB O FORWARD LONGERON DRAWING 1. Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 7 of 20 Printed in England ### Page 8 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT D.Test Not applicable. E.Close up (1) Make sure work area is clean, and clear of tools and miscellaneous equipment. (2) Refer to AMM 20-10-11. Restore protective treatment as required, using coloured chemical conversion coating, Material No.13-002 or Material No.13-002A and epoxy primer (Material No.16-580). (3) Refer to AMM 20-10-12. Restore paint finish as required, using polyurethane top coat grey (Material No.16-584). (4) Refer to SRM 51-23-00. Reinstate sealant (Material No.09-002A) in area of inspection as required. (5) Refer to AMM 06-40-00. Install access panels 281AT, 281AZ, 281BT, 281CT, 282AZ, 282BT, 282CT. F.Documentation (1) Record, in aircraft technical records, embodiment of this SB. G.Terminating action (1) None. Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 8 of 20 Printed in England ### Page 9 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT 3. Material information A. Materials (1) Materials required (Operator supplied). Table 1. DESCRIPTION MATERIAL NUMBER QTY. (REF.AMM 20-20-00 ) Coloured chemical conversion coating 13-002 or 13-002A A/R epoxy primer 16-580 A/R polyurethane top coat grey 16-584 A/R PR1422B-2 Sealant 09-002 AYR NOTE: A/R denotes as required. Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 9 of 20 Printed in England ### Page 10 (OCR) BAE SYSTEMS BAe 146 SERIES/AUR SERVE SERES AIRCRAFT This Page Is Intentionally Left Blank. Date: 25-AUG-2023 Revision: Initial issue Printed in England ### Page 11 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT APPENDIX 1 1.INSPECTION REPORT A. Complete and return this form as detailed OPERATOR: AIRCRAFT REGISTRATION: CONSTRUCTOR'S NUMBER: FLIGHT HOURS: LANDINGS: DATE INSPECTION PERFORMED: FINDINGS: To: Customer Technical Support (Building 37), BAE SYSTEMS (Operations) Limited, Prestwick International Airport, Ayrshire, KA9 2RW, SCOTLAND. e-mail raengliaison@baesystems.com Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 11 of 20 Printed in England ### Page 12 (OCR) BAE SYSTEMS BAe 146 SERIES/AUR SERVE SERES AIRCRAFT This Page Is Intentionally Left Blank. Date: 25-AUG-2023 page 1zo20 Revision: Initial issue Printed in England ### Page 13 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT APPENDIX 2 HIGH FREQUENCY EDDY CURRENT INSPECTION OF RIB O FORWARD LONGERON RADIUS 1.COMPONENT OR AREA TO BE INSPECTED A.Wing to Fuselage Attachment Longeron (1) The forward longeron at Rib 0 (Ref. Drawing 2). (a) Wing to fuselage attachment longeron. B.Description Of Possible Damage (1) Inspection (a) Cracks initiating at the free edge of the horizontal flanges of the forward longeron at Rib O in the upper or inboard/outboard surfaces, 0.1 in. (2.54 mm) or greater in Length. C.Related Documents (1) NTM Part 1, Chapter 20-00-00, Section 3, Safety Precautions. (2) NTM Part 6, Chapter 20-00-00, Eddy Current Testing - General. (3) NTM Part 6, Chapter 20-06-00, Instrument calibration. (4) Aircraft Maintenance Manual (AMM). (5) Test Instrument Manufacturer's Handbook. D.Equipment and Materials (1) The following equipment was used during the development of this instruction and was found to be acceptable. (a) Instrument: Elotest B1 v4 phase analysis eddy current instrument, with B1-2BN-1 adapter, from Rohmann (UK) Ltd. (b) Balance load: Inductance - 47 uH. Part number 5A058, from Hocking NDT Ltd. (c) Probe 1: Absolute, shielded, 500 kHz straight probe with a 90-degree tip. Part number LS-171-1E, from Rohmann (UK) Ltd. (d) Probe 2: Absolute, shielded, 500 kHz pencil probe. Part Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 13 of 20 Printed in England ### Page 14 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT number LS-185-1E, from Rohmann (UK) Ltd. (e) Calibration standard: Aluminium block with 0.020 in. (0.5 mm) deep slot. Part number 29A029, from Hocking NDT Ltd (Refer to NTM, PART 6, 20-06-00). NOTE: Probe 1 or Probe 2 to be used as required at Operators discretion. NOTE: Any comparable eddy current equipment may be used provided it satisfies the requirements of this instruction and is capable of resolving the slot in the calibration standard at the required level of sensitivity. E.Preparation (1) Make sure adequate staging is in place to provide safe access to the inspection area. (2) Make sure inspection area is clean and free from sealant. (3) Check the inspection area for any visible damage prior to inspection. Table 2. Calibration Settings Initial settings: Set to manufacturers instructions Alarm: Optional - Refer to manufacturers instructions Frequency: Set to 500 kHz Gain: Set to produce the required sensitivity Pre amp: -10 dB Y spread: 20 dB X spread: 0 dB Filter: Band: Set to Static High pass: Set to Off Low pass: Set to 40 Hz Bandwidth limiter: Set to Off Timebase/Display: Y/X Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 14 of 20 Printed in England ### Page 15 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT Dot position: Refer to Figure 2 F.Sensitivity Settings (1) Place the probe on the surface of the calibration standard away from the slots and balance the instrument. (2) Set lift-off effect to horizontal and to the left. (3) Slide the probe over the 0.020 in. (0.5 mm) slot in the calibration standard and adjust the settings to obtain a display similar to Drawing 3. (a) Ensure that the 0.020 in. (0.5 mm) slot produces a vertical displacement of 60 percent Full Screen Height (FSH). NOTE: Where the surface to be inspected is painted the Lift-off, zero and sensitivity adjustments should be carried out with a non-conducting shim of similar thickness to the paint between the probe and calibration standard. G.Inspection Procedure (1) Select the area for inspection, (Ref. Drawing 4) - Fastener positions 39A & 39B, 38A & 38B. (2) Place the probe on the surface to be inspected and balance the instrument. (3) Reset lift-off as required (Ref. Drawing 3). (4) Scan along the free edge between Frame 26 and the centreline of second fastener forward of Frame 26 (Ref. Drawing 4). (5) Repeat G. (1) to G. (4) for the remaining two scans for that flange. (6) Repeat G.(1) to G.(4) for the opposite flange. H.Acceptance Criteria (1) Interpret signals by reference to Drawing 3. (2) Any indication with a rapid vertical spot displacement having an amplitude of 20 percent FSH or greater that cannot be attributed to ferrous effect, probe handling or component geometry shall be considered to be a crack. Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 15 of 20 Printed in England ### Page 16 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT NOTE: Cracks and other discrete surface damage can usually be identified by a rapid vertical spot displacement, which once the crack or damage has been crossed returns to the balanced position. NOTE: Smooth, gradual spot movement is a common occurrence and can happen for a variety of reasons, such as paint thickness variation lift-off), edge effect and conductivity changes. Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 16 of 20 Printed in England ### Page 17 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT S D000000 FRAME 29 REAR SPAR (REF) FRAME 26 FRONT SPAR (REF) RIB O FORWARD LONGERON N5324902 FORWARD LONGERON, RIB O, AT FRAME 26 DRAWING 2. Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 17 of 20 Printed in England ### Page 18 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT SIGNAL FROM SIGNAL 0.020in (0.5mm) SLOT 60% FSH FROM EDGE 75% FSH 50% FSH 25% FSH 'X' INDICATES BALANCE POSITION LIFT OFF TYPICAL ELOTEST B1 V4 SCREEN DISPLAY FOR 0.020in (0.5mm) SLOT IN CALIBRATION STANDARD N5324903 TYPICAL SCREEN DISPLAY - HIGH FREQUENCY (PHASE ANALYSIS) EDDY CURRENTS Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 18 of 20 Printed in England ### Page 19 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT - FRAME 26 INSPECT THE FREE EDGES OF THE LONGERON FASTENER LEFT AND RIGHT HORIZONTAL FLANGES POSTIONS FROM FRAME 26 TO CENTRELINE OF THE SECOND FASTENER ATTACHING THE LONGERON (38A AND 38B) AT THREE POSITIONS FOR EACH SIDE C PROBE SCAN VIEW ON ARROW 'D* POSITIONS SECTION 'C-C' (NOT TO SCALE) CROSS SECTION SHOWING PROBE POSITIONS FOR EACH SCAN (3 SCANS PER FLANGE) FWD FRAME 26 FASTENERS SCAN UP TO FRAME 26 PROBE VIEW ON ARROW 'B' 0.079 in. (2.0 mm) MAXIMUM FROM EDGE SCAN PATHS OF FLANGE N5324904 FORWARD LONGERON, RIB O, AT FRAME 26 SCAN PATHS DRAWING 4. Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 19 of 20 Printed in England ### Page 20 (OCR) BAE SYSTEMS INSPECTION SERVICE BULLETIN BAe 146 SERIES/AVRO 146-RJ SERIES AIRCRAFT I.Reporting/Repair/Rectification (1) All crack and discontinuity indications are to be recorded in the relevant aircraft documentation and the appropriate BAE Systems approved repair rectification taken. Reporting Procedure (2) Report all cracks/discontinuities to: BAE Systems Repair Design Office (raengliaisonabaesystems.com) using Appendix 1. (3) Also send the information that follows: - Aircraft constructors number. - Aircraft registration. - Flying hours and number of landings. - ISB number. - Fastener location. - Direction and length of the crack or discontinuity/percent FSH. Date: 25-AUG-2023 ISB.53-249 Revision: Initial issue Page 20 of 20 Printed in England --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain, except the copies of manufacturers’ service documents, which belong to their rights holders.