{"id":"F2006B09875","name":"AD/F50/48 - RH Nacelle Aft Cone Fairing Fork-End Assemblies","slug":"ad-f50-48-rh-nacelle-aft-cone-fairing-fork-end-assemblies","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54991,"registerId":"commonwealth-F2006B09875-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/48 - RH Nacelle Aft Cone Fairing Fork-End Assemblies","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/F50/48 RH Nacelle Aft Cone Fairing Fork-End Assemblies 10/91\n\nApplicability: Serial numbers 20150, 20156, 20161, 20164, 20166, 20167, 20170, 20174 and 20175. Requirement:               Action in accordance with the Technical Requirements of RLD AD 90-037, dated\n\n12 April 1990.\n\n \n\nNote: Fokker Service Bulletin F50-54-007, dated 28 March 1990 refers.\n\n \n\nCompliance: Prior to exceeding 6000 flight cycles.\n\n \n\nBackground: The fork-end fittings that attach the RH nacelle aft cone fairing to the nacelle on aircraft equipped with an APU, have been found to have insufficient fatigue lives. This AD requires replacement of the fork-end fittings, with improved units.\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\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 mechanical defect in specific aircraft. It has not expanded beyond its original purpose of mandating replacement of fatigue-prone fork-end fittings."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 1 defined term implicitly referenced (flight cycles)","No cross-references to other legislation beyond a single external technical document (RLD AD 90-037)","Simple conditional logic: applies only to 9 specific serial numbers AND only to aircraft with APUs","Single compliance deadline (prior to 6,000 flight cycles)","No nested exceptions or complex procedural requirements"],"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). Think of it like a recall notice for aircraft, but legally binding.\n\n**What it does:** It requires owners or operators of specific Fokker F50 aeroplanes to replace certain metal fittings (called \"fork-end assemblies\") on the right-hand engine nacelle (the housing around the engine). These fittings attach the rear cone fairing (a protective cover) to the engine housing.\n\n**Why it matters:** The original fittings were found to wear out too quickly from repeated stress (fatigue) — specifically after around 6,000 flight cycles (one take-off and landing). If they fail, parts of the engine cover could detach during flight, creating a serious safety hazard.\n\n**Who must act:** Only applies to 9 specific aircraft (serial numbers listed: 20150, 20156, 20161, 20164, 20166, 20167, 20170, 20174 and 20175) that have an Auxiliary Power Unit (APU) — a small engine used for power when the main engines are off.\n\n**What must be done:** Replace the faulty fittings with improved, stronger versions before the aircraft completes 6,000 flight cycles. The work must follow the technical instructions in a Dutch aviation safety document (RLD AD 90-037) from April 1990."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"Based on the text of this AD, the instrument's scope is consistent with its stated purpose: it targets a defined set of serial-numbered aircraft and requires replacement of the identified fittings before 6,000 flight cycles due to insufficient fatigue lives. The AD does not expand or narrow the set of obligations beyond that stated corrective action and the referenced technical documents. (Applicability, Requirement, Compliance, Background)"},"complexity_factors":["Limited and specific applicability to nine aircraft by serial number (Applicability)","Single mandatory corrective action (replacement of fork-end fittings) rather than a program of inspections or variable treatments (Requirement)","Compliance set by a clear numeric usage threshold (6,000 flight cycles), which simplifies timing but requires accurate cycle records (Compliance)","Technical execution and detailed procedures are delegated to an external document (RLD AD 90-037) and a service bulletin, so the AD itself is concise but cross-references more detailed sources (Requirement, Note)","No phased implementation, conditional forums, or complex reporting obligations are included in the AD text (Requirement, Compliance)"],"plain_english_summary":"This AD applies to nine specified Fokker F50 (F27 Mk 50) aeroplanes and requires operators to replace the right‑hand nacelle aft‑cone fairing fork‑end fittings with improved units, following the technical requirements of RLD AD 90‑037. \n\nCompliance is mandatory before each affected aeroplane exceeds 6,000 flight cycles; owners/operators bear the cost, scheduling, and downtime, with implementation details referenced to the service bulletin."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-48-rh-nacelle-aft-cone-fairing-fork-end-assemblies","history":"/api/acts/ad-f50-48-rh-nacelle-aft-cone-fairing-fork-end-assemblies/history","analysis":"/api/acts/ad-f50-48-rh-nacelle-aft-cone-fairing-fork-end-assemblies/analysis","conflicts":"/api/acts/ad-f50-48-rh-nacelle-aft-cone-fairing-fork-end-assemblies/conflicts","importantCases":"/api/acts/ad-f50-48-rh-nacelle-aft-cone-fairing-fork-end-assemblies/important-cases","documents":"/api/acts/ad-f50-48-rh-nacelle-aft-cone-fairing-fork-end-assemblies/documents"}}