{"id":"F2006B09809","name":"AD/F28/75 - Fuselage Skin Lap Joint at Stringer 17/58","slug":"ad-f28-75-fuselage-skin-lap-joint-at-stringer-17-58","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54731,"registerId":"commonwealth-F2006B09809-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F28/75 - Fuselage Skin Lap Joint at Stringer 17/58","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nFokker F28 Series Aeroplanes\n\nAD/F28/75 Fuselage Skin Lap Joint at Stringer 17/58 9/94\n\nApplicability: F28 aircraft (except Mark 0100), all serial numbers.\n\nRequirement: Repair the fuselage skin lap joint between stringers 16 and 17 (58 and 59) in accordance with Fokker Service Bulletin (SB) F28/53-121 Revision 1.\n\nNote: RLD AD 91-022 refers.\n\nCompliance: 1. For aircraft modified in accordance with Fokker SB F28/21-16, repair before 32000 flights or before 15 February 1995, whichever occurs last.\n\n2. For aircraft not modified in accordance with Fokker SB F28/21-16, repair before 48000 flights or before 15 February 1995, whichever occurs last.\n\nNote: This repair eliminates the need for further inspections in accordance with the F28 Structural Integrity Program, Part 1, item 53-30-08 (AD/F28/45 refers).\n\nBackground: A Fokker evaluation has shown that current NDT methods are not effective at detecting small cracks in non-bonded dimpled riveted skin lap joints, such as the joint at Stringer 17/58. Therefore, as the cracks cannot reliably be detected, the RLD has determined that the Stringer 17/58 lap joint should be permanently repaired to avoid the possibility of joint failure and subsequent aircraft depressurisation.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific structural defect in a particular aircraft type. It has not expanded beyond its original purpose of mandating repair of the Stringer 17/58 lap joint."},"complexity_factors":["Single, specific technical requirement (one repair procedure)","Only two compliance pathways based on prior modification status","Minimal cross-referencing (only references one Service Bulletin and one related AD)","No nested definitions or interpretation sections","Short document (approximately 200 words)","Clear applicability statement (specific aircraft model, all serial numbers except one variant)"],"plain_english_summary":"This AD requires owners/operators of Fokker F28 aircraft (except Mark 0100) to permanently repair a lap joint near Stringer 17/58 per Fokker Service Bulletin F28/53-121 Rev 1 because small cracks in the riveted joint aren’t reliably found by non‑destructive testing and could cause in‑flight depressurisation.\n\nCompliance deadlines vary by modification history (earlier deadline if modified per SB F28/21‑16); once repaired, ongoing inspections of this joint are no longer required."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The AD's scope aligns with the stated objective in the Background: to permanently repair the Stringer 17/58 lap joint because small cracks cannot be reliably detected by NDT. It applies to the entire applicable F28 fleet (except Mark 0100) with compliance times tied to prior modification status, and does not extend relief or requirements to other joints or aircraft types beyond those specified."},"complexity_factors":["Technical detection limit: the AD is motivated by a finding that current NDT methods cannot reliably detect small cracks in non-bonded dimpled riveted lap joints (Background).","Single prescriptive remedy: requires repair per a specific Fokker Service Bulletin (Requirement: SB F28/53-121 Revision 1), which raises technical compliance and implementation specificity.","Differentiated compliance timing: two distinct deadlines depending on whether the aircraft was modified under SB F28/21-16 (Compliance paragraphs 1–2).","Fleet applicability: applies to all F28 aircraft except Mark 0100, across all serial numbers (Applicability), concentrating administrative impact on the whole applicable fleet.","Cross-references to other regulatory material: notes and effects on the F28 Structural Integrity Program (Part 1, item 53-30-08) and references to other ADs (RLD AD 91-022; AD/F28/45), which require readers to follow linked documents for full compliance context.","Operational impact on operators: the directive imposes repair and scheduling obligations and therefore affects maintenance planning, downtime and direct repair costs (Requirement and Compliance)."],"plain_english_summary":"This AD mandates a permanent repair of the fuselage skin lap joint between stringers 16 and 17 (58/59) on Fokker F28 aircraft (except Mark 0100), to be carried out in accordance with Fokker Service Bulletin F28/53-121 Revision 1. Compliance deadlines depend on whether the aeroplane was modified under SB F28/21-16; completing the repair removes the need for further inspections under the F28 Structural Integrity Program. It affects operators and maintenance organisations and imposes repair and scheduling obligations on operators because NDT cannot reliably detect small cracks at this joint."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f28-75-fuselage-skin-lap-joint-at-stringer-17-58","history":"/api/acts/ad-f28-75-fuselage-skin-lap-joint-at-stringer-17-58/history","analysis":"/api/acts/ad-f28-75-fuselage-skin-lap-joint-at-stringer-17-58/analysis","conflicts":"/api/acts/ad-f28-75-fuselage-skin-lap-joint-at-stringer-17-58/conflicts","importantCases":"/api/acts/ad-f28-75-fuselage-skin-lap-joint-at-stringer-17-58/important-cases","documents":"/api/acts/ad-f28-75-fuselage-skin-lap-joint-at-stringer-17-58/documents"}}