{"id":"F2006B11144","name":"AD/LEARJET/27 - Horizontal Stabiliser Hinge Pin Bushing Installation - Inspection","slug":"ad-learjet-27-horizontal-stabiliser-hinge-pin-bushing-installation-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56830,"registerId":"commonwealth-F2006B11144-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LEARJET/27 - Horizontal Stabiliser Hinge Pin Bushing Installation - Inspection","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)  Gates Learjet 24 & 25 Series Aeroplanes\n\n \n\nAD/LEARJET/27 Horizontal Stabiliser Hinge Pin Bushing\n\nInstallation - Inspection\n\n\n12/81\n\n \n\nApplicability: All Gates Learjet models 24 and 25 with S/Nos. referenced in Gates Learjet Service Bulletin No. 23/24/ 25-311 or with S/Nos. referenced in subsequent issues of that Service Bulletin.\n\n \n\nDocument: Gates Learjet SB 23/24/25-311.\n\n \n\nCompliance: Within 100 hours time in service after 31 December 1981.\n\n \n\nBackground:  The horizontal stabiliser hinge pin bushings may move out of their mating fittings during normal service.\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, single-issue airworthiness directive focused specifically on a known mechanical defect in particular aircraft models. It has not expanded beyond its original purpose of mandating inspection of horizontal stabiliser hinge pin bushings."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 4 defined elements: applicability, document reference, compliance deadline, and background","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1988","Single, unambiguous compliance action (inspect per service bulletin)","No conditional logic, exceptions, or alternative compliance methods","Clear, fixed deadline (100 hours after 31 December 1981)"],"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 and operators of certain **Gates Learjet 24 and 25 series aircraft** to inspect the **horizontal stabiliser hinge pin bushings** — small but critical components that help control the aircraft's pitch (up and down movement).\n\n**The safety problem:**\nThese bushings can work loose from their fittings during normal flight operations. If they move out of position, it could affect the aircraft's ability to stay level or control its altitude — a serious flight safety risk.\n\n**Who must comply:**\nAnyone operating a Learjet 24 or 25 with specific serial numbers listed in Gates Learjet Service Bulletin No. 23/24/25-311 (or later versions of that bulletin).\n\n**What they must do:**\nFollow the inspection procedures in the referenced service bulletin within **100 hours of flight time** after 31 December 1981.\n\n**Why it matters:**\nAirworthiness Directives are legally binding. Ignoring this order means the aircraft cannot legally fly in Australian airspace. This particular directive addresses a mechanical defect that could lead to loss of aircraft control if left unchecked."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive applies only to Gates Learjet models 24 and 25 with serial numbers listed in the cited service bulletin or subsequent issues, and requires inspection within a specified 100-hour window for the stated reason that bushings may move out of their fittings. Nothing in the text indicates an expansion or narrowing of that scope beyond the serial-number limitation and the reliance on subsequent issues of the service bulletin (Applicability; Document; Compliance; Background)."},"complexity_factors":["Narrow, aircraft-model-and-serial-number-specific applicability reduces breadth but requires serial-number verification (Applicability).","Compliance relies on an external technical document (Gates Learjet SB 23/24/25-311), which requires consulting and following manufacturer procedures (Document).","A fixed, short compliance window referenced to a calendar date (100 hours after 31 December 1981) creates scheduling constraints (Compliance).","Technical nature of the inspection means qualified maintenance personnel and possible parts supply considerations are necessary, adding operational complexity.","Allowance for later issues of the service bulletin introduces potential variability in precise procedures and scope (Document)."],"plain_english_summary":"This directive requires operators of specific Gates Learjet 24 and 25 airframes identified in Service Bulletin 23/24/25‑311 to inspect the horizontal stabiliser hinge‑pin bushings per that SB, to be completed within 100 flight hours after 31 December 1981.  \n\nIt affects only those listed serial numbers, places inspection and any corrective costs on operators, and aims to detect bushings that may have moved out of their fittings during service."}},"importantCases":[],"_links":{"self":"/api/acts/ad-learjet-27-horizontal-stabiliser-hinge-pin-bushing-installation-inspection","history":"/api/acts/ad-learjet-27-horizontal-stabiliser-hinge-pin-bushing-installation-inspection/history","analysis":"/api/acts/ad-learjet-27-horizontal-stabiliser-hinge-pin-bushing-installation-inspection/analysis","conflicts":"/api/acts/ad-learjet-27-horizontal-stabiliser-hinge-pin-bushing-installation-inspection/conflicts","importantCases":"/api/acts/ad-learjet-27-horizontal-stabiliser-hinge-pin-bushing-installation-inspection/important-cases","documents":"/api/acts/ad-learjet-27-horizontal-stabiliser-hinge-pin-bushing-installation-inspection/documents"}}