{"id":"F2006B09848","name":"AD/F50/22 - Elevator Trim Cable Pulley Bracket and Mounting","slug":"ad-f50-22-elevator-trim-cable-pulley-bracket-and-mounting","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54909,"registerId":"commonwealth-F2006B09848-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/22 - Elevator Trim Cable Pulley Bracket and Mounting","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/F50/22 Elevator Trim Cable Pulley Bracket and Mounting 8/89\n\nApplicability: Serial numbers 20103 through 20108 and 20110 through 20123.\n\n \n\nRequirement: Reinforce elevator trim cable pulley brackets and mountings in accordance with Fokker Service Bulletin F50-27-008 dated 3 February 1989.\n\n \n\nNote: Netherlands AD 89-24 refers.\n\n \n\nCompliance: Prior to the accumulation of 8000 flight cycles.\n\n \n\nBackground:  Stress analysis has shown that the increased tension in the elevator trim cables will decrease the fatigue life of the pulley brackets and mountings.\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\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive's scope is limited to the specified Fokker F50 serial numbers (20103–20108 and 20110–20123) and requires reinforcement per the named Fokker Service Bulletin to be completed before 8,000 flight cycles. The instrument, as presented, implements that targeted corrective action; there is no indication in the text that the scope has been broadened or otherwise altered from that stated purpose (Applicability; Requirement; Compliance; Background)."},"complexity_factors":["Very narrow applicability: limited to specific aircraft serial numbers (Applicability).","Single technical action required: reinforcement of pulley brackets and mountings as specified (Requirement).","Compliance metric is simple and specific: completion before accumulation of 8,000 flight cycles (Compliance).","Method prescribed by manufacturer service bulletin, reducing procedural variability (Requirement).","No alternative compliance procedures or exemptions are stated in the text, which simplifies compliance interpretation.","Cross-reference to another authority (Netherlands AD) adds an external regulatory linkage (Note)."],"plain_english_summary":"What this instrument does (mechanically)\n\n- This Airworthiness Directive (AD) requires a physical modification to certain Fokker F50 (F27 Mk 50) aeroplanes. Specifically, it mandates reinforcement of the elevator trim cable pulley brackets and their mountings in accordance with Fokker Service Bulletin F50-27-008 dated 3 February 1989. (Requirement)\n- The AD applies only to aeroplanes with serial numbers 20103–20108 and 20110–20123. (Applicability)\n- The reinforcement must be completed before the affected aeroplane accumulates 8,000 flight cycles. (Compliance)\n\nWhy the change is required (official rationale)\n\n- The directive states that stress analysis has shown increased tension in the elevator trim cables will reduce the fatigue life of the pulley brackets and mountings. That engineering finding is given as the reason for requiring reinforcement. (Background)\n- The AD cross-references a related Netherlands AD (Note). (Note)\n\nWho is affected and who decides how the work is done\n\n- The owners/operators of the listed serial-number aeroplanes are the parties required to have the work done, because the AD is limited to those serial numbers. (Applicability; Requirement)\n- The AD prescribes the method for the modification by referring to a specific Fokker Service Bulletin. That means the manufacturer’s service instructions determine the technical steps to be taken. (Requirement)\n\nPractical effects, costs and compliance mechanics\n\n- The directive turns a design/engineering concern (reduced fatigue life) into a mandatory maintenance action for a defined set of aircraft. (Background; Requirement)\n- Compliance requires scheduling and performing the reinforcement work before the 8,000 flight–cycle threshold, which creates a clear monitoring requirement (tracking flight cycles) and a deadline for maintenance planning. (Compliance)\n- The mandatory work will require parts, labour and aircraft downtime; those are the direct operational inputs necessary to satisfy the AD (implied by the Requirement). The AD itself does not state who pays, but it places the obligation to carry out the work on the operators of the affected aircraft. (Applicability; Requirement)\n\nTrade-offs, incentives and implementation risks (mechanical and administrative)\n\n- The AD reduces the risk associated with pulley-bracket fatigue by making reinforcement compulsory for the targeted fleet segment. (Background)\n- The requirement concentrates costs and downtime on a narrowly defined group of aircraft (the listed serial numbers). Operators must balance the timing of the reinforcement against operational schedules because the compliance metric is flight cycles rather than calendar time. (Applicability; Compliance)\n- The AD fixes the technical remedy by reference to the manufacturer’s Service Bulletin, so there is limited discretion in how the modification is accomplished unless an alternative is later approved by the regulator. (Requirement)\n- Implementation relies on accurate tracking of flight cycles and execution of the specified service instructions. Failure to monitor cycles or to follow the prescribed procedures would be the primary compliance risks. (Compliance; Requirement)\n\nConcise statement of the mechanical change and the stated purpose\n\n- Mechanical change required: reinforce elevator trim cable pulley brackets and mountings per Fokker Service Bulletin F50-27-008 (Requirement).\n- Stated purpose: to address reduced fatigue life caused by increased tension in the elevator trim cables (Background)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific engineering defect in a limited aircraft population. It has not expanded beyond its original purpose of mandating a structural reinforcement."},"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 or complex conditional logic","Single, straightforward compliance requirement with clear deadline","No exceptions, exemptions, or nested conditions","Technical content refers to external engineering document (Service Bulletin) rather than legislative complexity"],"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:**\nIt requires owners or operators of certain Fokker F50 aeroplanes to strengthen (reinforce) the brackets and mountings that hold the elevator trim cable pulleys. The elevator trim system helps pilots control the aircraft's pitch (nose up or down), and the pulleys guide the cables that move this system.\n\n**Who it affects:**\nOnly Fokker F50 aircraft with serial numbers 20103 through 20108 and 20110 through 20123 — a specific batch of 20 planes.\n\n**Why it matters:**\nEngineering analysis found that higher tension in the elevator trim cables was causing faster wear and tear (fatigue) on the pulley brackets than originally expected. If these brackets fail, the pilot could lose control of the elevator trim, potentially making the aircraft difficult or dangerous to fly. The directive mandates a fix before the aircraft reaches 8,000 flight cycles (roughly, one takeoff and landing equals one cycle).\n\n**What must be done:**\nOperators must follow the exact repair instructions in **Fokker Service Bulletin F50-27-008** (dated 3 February 1989) to reinforce the affected parts."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-22-elevator-trim-cable-pulley-bracket-and-mounting","history":"/api/acts/ad-f50-22-elevator-trim-cable-pulley-bracket-and-mounting/history","analysis":"/api/acts/ad-f50-22-elevator-trim-cable-pulley-bracket-and-mounting/analysis","conflicts":"/api/acts/ad-f50-22-elevator-trim-cable-pulley-bracket-and-mounting/conflicts","importantCases":"/api/acts/ad-f50-22-elevator-trim-cable-pulley-bracket-and-mounting/important-cases","documents":"/api/acts/ad-f50-22-elevator-trim-cable-pulley-bracket-and-mounting/documents"}}