{"id":"F2006B09880","name":"AD/F50/52 - Cockpit Window Post Attach Angles","slug":"ad-f50-52-cockpit-window-post-attach-angles","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55006,"registerId":"commonwealth-F2006B09880-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/52 - Cockpit Window Post Attach Angles","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/F50/52 Cockpit Window Post Attach Angles 4/92\n\nApplicability: F27 Mk 50 series serial numbers:\n\n \n\n20103 to 20108 inclusive;\n\n \n\n20110 to 20149 inclusive; and\n\n \n\n20151 and 20152.\n\n \n\nRequirement: Modify in accordance with Fokker Service Bulletin F50-53-029 dated 1 August 1990.\n\n \n\nNote: RLD AD (BLA) 90-084 refers.\n\n \n\nCompliance: Required before accumulating 30 000 flight cycles.\n\n \n\nBackground: During a full scale fatigue test of the forward fuselage, five of the attachment angles at the upper and lower ends of the window posts showed fatigue cracks at 45 000 simulated flight cycles. To extend the fatigue life of the window posts the 16 existing aluminium alloy angles are replaced by corrosion resistant steel 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","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 a particular modification to prevent window post failures."},"complexity_factors":["Single, specific technical requirement (replace specific parts per manufacturer bulletin)","Clear applicability criteria (specific serial number ranges)","Simple compliance deadline (before 30,000 flight cycles)","No defined terms section or complex cross-referencing","Straightforward background explanation without nested conditions"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:** It requires owners or operators of certain Fokker F50 aeroplanes to replace 16 aluminium alloy window post attachment angles with stronger, corrosion-resistant steel ones. This modification must be done before the aircraft reaches 30,000 flight cycles (roughly, one take-off and landing equals one cycle).\n\n**Who it affects:** Anyone who owns or operates Fokker F50 aircraft with serial numbers 20103–20108, 20110–20149, and 20151–20152.\n\n**Why it matters:** During fatigue testing, engineers found cracks developing in these attachment angles after 45,000 simulated flight cycles. Since these angles hold the cockpit windows in place, fatigue cracks could compromise structural integrity and flight safety. The directive prevents potential failures by mandating stronger replacement parts before the aircraft accumulates too much wear and tear."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"Scope remains focused: the directive mandates a specific structural modification for the listed serial-number aircraft to mitigate fatigue risk. It does not broaden applicability beyond those serial numbers or add recurring inspection regimes; it replaces specified parts per the service bulletin and sets a flight-cycle compliance deadline (Applicability; Requirement; Compliance; Background)."},"complexity_factors":["Narrow, serial-number-based applicability requires fleet-level record checks to identify affected aircraft (Applicability).","Single, well-defined technical action: replace 16 aluminium angles with corrosion-resistant steel per a named service bulletin (Requirement).","Compliance measured by flight cycles (operational tracking) rather than calendar time, so operators must monitor usage to schedule work (Compliance).","Technical dependence on manufacturer service bulletin details for correct modification; implementer must follow engineering instructions (Requirement).","Procurement and installation burden on operators: sourcing steel angles and arranging maintenance slots and certification.","Cross-reference to another authority’s AD (RLD AD (BLA) 90-084) introduces potential coordination or interpretation needs (Note).","Background evidence (full-scale fatigue test showing cracks at 45,000 cycles) constrains options to a structural modification rather than monitoring alone (Background)."],"plain_english_summary":"This airworthiness directive orders owners/operators of specified Fokker F50 (F27 Mk 50) aeroplanes (listed serial numbers) to replace the 16 aluminium cockpit window post attach angles with corrosion‑resistant steel in accordance with Fokker Service Bulletin F50‑53‑029. The Civil Aviation Safety Authority requires the modification before the aircraft reach 30,000 flight cycles to address fatigue cracks found in test cycles. Operators arrange and pay for the work; the directive changes maintenance obligations and parts procurement timing."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-52-cockpit-window-post-attach-angles","history":"/api/acts/ad-f50-52-cockpit-window-post-attach-angles/history","analysis":"/api/acts/ad-f50-52-cockpit-window-post-attach-angles/analysis","conflicts":"/api/acts/ad-f50-52-cockpit-window-post-attach-angles/conflicts","importantCases":"/api/acts/ad-f50-52-cockpit-window-post-attach-angles/important-cases","documents":"/api/acts/ad-f50-52-cockpit-window-post-attach-angles/documents"}}