{"id":"F2006B09873","name":"AD/F50/46 - Forward Fuselage Skin Dimples","slug":"ad-f50-46-forward-fuselage-skin-dimples","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54987,"registerId":"commonwealth-F2006B09873-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/46 - Forward Fuselage Skin Dimples","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Fokker F50 (F27 Mk 50) Series Aeroplanes\n\n \n\nAD/F50/46 Forward Fuselage Skin Dimples 10/91\n\nApplicability: Serial numbers 20103 to 20108 inclusive, 20110 to 20149 inclusive, and 20151 and\n\n20152.\n\n \n\nRequirement: Action in accordance with the Technical Requirements of RLD AD 89-152, dated 15 December 1989.\n\n \n\nNote: Fokker Service Bulletin F50-53-018, dated 8 December 1989 refers.\n\n \n\nCompliance: Prior to exceeding 10 000 pressurisation cycles.\n\n \n\nBackground: During full-scale fatigue testing, cracks were found in the forward fuselage skin, which originated at the rivet hole dimples. To improve the fatigue life of the skin-to- stringer and skin-to-frame connectors, this AD calls for the installation of reinforcement angles.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","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 fatigue issue identified during testing. It has not expanded beyond its original purpose of mandating reinforcement for identified aircraft serial numbers."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 3 defined elements: applicability by serial number, single technical requirement reference, and one compliance threshold","No nested conditional logic or exceptions","Single cross-reference to external technical document (RLD AD 89-152)","Straightforward mandatory action with clear deadline"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\nOrders owners/operators of certain Fokker F50 aeroplanes to install reinforcement angles on the forward fuselage skin. This fixes a fatigue cracking problem discovered during testing.\n\n**Who it affects:**\nOwners and operators of Fokker F50 aircraft with specific serial numbers: 20103–20108, 20110–20149, and 20151–20152.\n\n**Why it matters:**\nDuring fatigue testing, engineers found cracks starting at rivet hole dimples in the forward fuselage skin. These cracks could compromise the aircraft's structural integrity over time. The directive prevents potential structural failure by requiring reinforcement before the aircraft completes 10,000 pressurisation cycles (the repeated pressurising and depressurising that happens with every flight).\n\n**Key deadline:**\nThe fix must be done before the aircraft reaches 10,000 pressurisation cycles.\n\n**Technical reference:**\nThe work must follow the technical requirements of a Dutch aviation authority directive (RLD AD 89-152) and Fokker Service Bulletin F50-53-018."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"The directive converts a design/fatigue finding into a mandatory corrective modification for the listed serial numbers by requiring installation of reinforcement angles before 10,000 pressurisation cycles (Requirement; Compliance). This alters operator obligations from ordinary inspection/monitoring to a compulsory structural modification and associated costs and scheduling responsibilities."},"complexity_factors":["Narrow, serial‑numbered applicability limits affected fleet but requires individual aircraft checks (Applicability).","Mandates a specific structural modification rather than routine inspection—installation of reinforcement angles (Requirement; Background).","Relies on external technical documents (RLD AD 89‑152) and a manufacturer service bulletin for implementation details (Requirement; Note).","A firm compliance metric tied to airframe life: before exceeding 10,000 pressurisation cycles (Compliance).","Operational impacts include downtime, parts and labour costs, and scheduling across operators; these follow directly from the mandated modification (implicit from Requirement and Compliance)."],"plain_english_summary":"This airworthiness directive requires operators of certain Fokker F50 aeroplanes (serials 20103–20108, 20110–20149, 20151–20152) to install reinforcement angles on the forward fuselage skin in accordance with RLD AD 89‑152 and Fokker Service Bulletin F50‑53‑018. The Civil Aviation Safety Authority requires completion before any affected aeroplane exceeds 10,000 pressurisation cycles. Operators/owners must schedule and pay for the structural modification to address cracks that began at rivet‑hole dimples during fatigue testing."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-46-forward-fuselage-skin-dimples","history":"/api/acts/ad-f50-46-forward-fuselage-skin-dimples/history","analysis":"/api/acts/ad-f50-46-forward-fuselage-skin-dimples/analysis","conflicts":"/api/acts/ad-f50-46-forward-fuselage-skin-dimples/conflicts","importantCases":"/api/acts/ad-f50-46-forward-fuselage-skin-dimples/important-cases","documents":"/api/acts/ad-f50-46-forward-fuselage-skin-dimples/documents"}}