{"id":"F2006B10486","name":"AD/HS 125/47 - Fin Rear Spar - Elevator Control Pulley Bracket Modification","slug":"ad-hs-125-47-fin-rear-spar-elevator-control-pulley-bracket-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116235,"registerId":"commonwealth-F2006B10486-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 125/47 - Fin Rear Spar - Elevator Control Pulley Bracket Modification","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)  British Aerospace BAe 125 Series Aeroplanes\n\n \n\nAD/HS 125/47 Fin Rear Spar - Elevator Control Pulley Bracket Modification\n\n\n6/77\n\n \n\nApplicability: As detailed in the Requirement Document: Hawker Siddeley SB No. 27-122-(2578). Compliance:               Before 31 March 1978.\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\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, time-bound safety directive from 1977 with a narrow, specific scope (modification of a particular aircraft component). It has not expanded beyond its original purpose."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 defined elements: applicability and compliance deadline","Single cross-reference to external technical document (Hawker Siddeley SB)","No conditional logic or exceptions","Straightforward command structure: 'applies to X, do Y by Z date'","No internal definitions section","No nested provisions or subsections"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA) under the Civil Aviation Regulations 1998. It applies to **British Aerospace BAe 125 series aircraft** (business jets).\n\n**What it does:**\nThe directive requires owners/operators to modify the **fin rear spar** (a structural component at the back of the aircraft's tail) and the **elevator control pulley bracket** (part of the system that controls the aircraft's pitch/up-down movement). The specific modification details are found in a technical document called **Hawker Siddeley Service Bulletin No. 27-122-(2578)**.\n\n**Who it affects:**\n- Owners and operators of British Aerospace BAe 125 series aeroplanes\n- Maintenance organisations servicing these aircraft\n\n**Why it matters:**\nAirworthiness Directives are legally binding safety orders. This one addresses a potential structural or control system defect that could affect flight safety. The modification must be completed **before 31 March 1978** to keep the aircraft legally airworthy.\n\n**Key point:** The directive itself doesn't describe the technical fix—it simply mandates compliance with the referenced service bulletin, which contains the actual engineering instructions."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD as supplied sets a straightforward regulatory requirement to perform a specific modification per the referenced Hawker Siddeley service bulletin and a fixed compliance date. There is no indication in the supplied text that the directive’s scope departs from that original, intended action: it mandates the modification for the aircraft identified in the requirement document and fixes a compliance deadline (see \"Applicability\" and \"Compliance\")."},"complexity_factors":["Short, narrowly targeted directive focused on one component (fin rear spar elevator control pulley bracket).","Relies on an external technical document (Hawker Siddeley SB No. 27-122-(2578)) for the actual work specification.","Contains a single clear compliance deadline (before 31 March 1978) rather than staged or conditional requirements.","Limited legal text in the supplied extract—no multiple compliance options, exemptions, or ancillary procedures set out in this excerpt.","Technical implementation complexity (aircraft maintenance) sits in the service bulletin rather than in the AD text, concentrating regulatory legal simplicity but technical execution complexity outside the instrument."],"plain_english_summary":"What this instrument does\n\n- This is an airworthiness directive titled \"AD/HS 125/47 — Fin Rear Spar - Elevator Control Pulley Bracket Modification\" issued under the Commonwealth Civil Aviation Regulations (Schedule of Airworthiness Directives). It requires a specific modification to the fin rear spar elevator control pulley bracket on certain British Aerospace BAe 125 series aeroplanes. (See: Applicability line and the AD title.)\n\nWho it affects\n\n- Aircraft owners/operators and maintenance organisations responsible for the BAe 125 series aeroplanes listed in the referenced requirement document. The AD points to Hawker Siddeley Service Bulletin No. 27-122-(2578) for details of which aeroplanes and exactly what work must be done. (See: \"Applicability: As detailed in the Requirement Document: Hawker Siddeley SB No. 27-122-(2578)\")\n\nHow it works, mechanically\n\n- The AD requires that the modification described in the referenced Hawker Siddeley service bulletin be performed. The AD sets a firm compliance deadline: the work must be completed before 31 March 1978. (See: \"Compliance: Before 31 March 1978.\")\n\nOfficial rationale (as presented by the form of the document)\n\n- The document is an airworthiness directive. By form and placement in the Schedule of Airworthiness Directives, it is presented as a mandatory measure addressing an identified technical/airworthiness issue for the affected aeroplanes. The text supplied does not include a detailed explanation of the technical failure mode or incident history that prompted the directive.\n\nWho pays, who decides, and what behaviour changes\n\n- Who pays: The owners/operators of the affected BAe 125 aircraft would be responsible for procuring parts and paying for labour to perform the modification required by the service bulletin (the AD itself does not allocate funding). (Source: Applicability and Compliance lines.)\n- Who decides: The Civil Aviation Safety Authority issued the directive via the Schedule of Airworthiness Directives; the AD itself delegates the technical specification of the work to the Hawker Siddeley service bulletin it references. (Source: AD heading and \"Requirement Document\" reference.)\n- Behaviour changes required: Affected operators must schedule and complete the specified modification by the deadline. That may require taking aircraft out of service until the work is done and engaging appropriately rated maintenance providers.\n\nCosts, incentives and trade-offs to note (grounded in what the instrument requires)\n\n- Cost bearer and concentration: Costs are concentrated on the operators of the affected BAe 125 aircraft (who must pay for the modification). The directive does not provide financial support or exemptions. (Source: Applicability and Compliance.)\n- Compliance burden and timing risk: The AD imposes a hard deadline for compliance. Operators must arrange parts, technical labour, and aircraft availability; if parts or qualified maintenance capacity are limited, operators may face scheduling delays or operational disruption.\n- Effects on maintenance market and contract freedom: The AD requires work to the specification in the referenced service bulletin. Maintenance work can be performed by any organisation capable of meeting that specification, subject to regulatory approvals; the bulletin may specify parts or procedures that affect whether independent providers or OEM-affiliated shops are better placed to perform the work (the AD text provided does not list those technical details). (Source: reference to Hawker Siddeley SB No. 27-122-(2578).)\n- Implementation risk and opportunity cost: Time spent and money spent complying with the AD cannot be used for other maintenance or investments; the AD’s deadline creates a scheduling priority relative to other tasks.\n\nNet effect summary\n\n- Mechanically, the directive converts the Hawker Siddeley service bulletin requirement into a mandatory regulatory obligation with a fixed compliance date for the covered BAe 125 aeroplanes. The regulatory obligation assigns costs and operational disruption risk to aircraft owners/operators and delegates the technical specification of the work to the referenced service bulletin. (See: AD title; Applicability; Compliance.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-125-47-fin-rear-spar-elevator-control-pulley-bracket-modification","history":"/api/acts/ad-hs-125-47-fin-rear-spar-elevator-control-pulley-bracket-modification/history","analysis":"/api/acts/ad-hs-125-47-fin-rear-spar-elevator-control-pulley-bracket-modification/analysis","conflicts":"/api/acts/ad-hs-125-47-fin-rear-spar-elevator-control-pulley-bracket-modification/conflicts","importantCases":"/api/acts/ad-hs-125-47-fin-rear-spar-elevator-control-pulley-bracket-modification/important-cases","documents":"/api/acts/ad-hs-125-47-fin-rear-spar-elevator-control-pulley-bracket-modification/documents"}}