{"id":"F2006B11096","name":"AD/LEARJET 35/18 - Horizontal Stabiliser Hinge Pin Bushing Installation - Inspection","slug":"ad-learjet-35-18-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":56756,"registerId":"commonwealth-F2006B11096-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LEARJET 35/18 - 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 35 and 36 Series Aeroplanes\n\n \n\nAD/LEARJET 35/18 Horizontal Stabiliser Hinge Pin Bushing\n\nInstallation - Inspection\n\n\n12/81\n\n \n\nApplicability: All models 35 & 36 with S/Nos. referenced in Gates Learjet Service Bulletin No.\n\n35/36-27-13 or with S/Nos. referenced in subsequent issues of that Service Bulletin.\n\n \n\nDocument: Gates Learjet SB 35/36-27-13.\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\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD's scope is presented in the instrument itself: it applies to Learjet 35 and 36 aeroplanes with serial numbers listed in Gates Learjet SB 35/36-27-13 (or later issues of that Bulletin) and requires inspection within the specified 100-hour window. There is no indication in the text provided that the scope, as set out in the Instrument (Applicability; Document; Compliance), has been changed from the original intent described in the document."},"complexity_factors":["Narrow applicability limited to serial numbers listed in a specific Service Bulletin (Applicability; Document)","Dependency on an external technical document (Gates Learjet SB 35/36-27-13) for procedures and corrective actions (Document)","A single, short compliance window (100 hours after 31 December 1981) reduces scheduling flexibility but simplifies timing (Compliance)","Technical nature of the inspection requires certificated maintenance personnel and possible parts replacement, introducing operational variability (Document)","No layered regulatory steps or ongoing monitoring duties specified in the AD itself (Compliance)"],"plain_english_summary":"What this instrument does, mechanically\n\n- This Airworthiness Directive (AD) requires operators of certain Gates Learjet 35 and 36 aeroplanes to carry out an inspection of the horizontal stabiliser hinge pin bushing installation. (Document: Gates Learjet SB 35/36-27-13; Compliance)\n\nWho it applies to\n\n- It applies to all Learjet 35 and 36 aeroplanes whose serial numbers are listed in Gates Learjet Service Bulletin No. 35/36-27-13, or in later issues of that Service Bulletin. (Applicability; Document)\n\nWhen the work must be done\n\n- The inspection must be completed within 100 hours time in service after 31 December 1981. (Compliance)\n\nWhy the directive was issued (statement from the source)\n\n- The Background states that the horizontal stabiliser hinge pin bushings may move out of their mating fittings during normal service. That is the operational condition the AD is intended to address. (Background)\n\nWhat operators must do, in practice\n\n- Locate affected aircraft by serial number using the referenced Service Bulletin. (Applicability; Document)\n- Follow the inspection procedure and any corrective actions described in Gates Learjet SB 35/36-27-13. (Document)\n- Complete the inspection within the 100-hour window specified. (Compliance)\n\nWho pays and who decides\n\n- Aircraft operators (owners or their maintenance organisations) bear the direct costs of the inspection and any repairs or parts required by the Service Bulletin. (Document; Compliance)\n- The Civil Aviation Safety Authority issues the AD and sets the compliance requirement; the Service Bulletin provides the technical steps to be followed. Operational decisions about when and how the inspection is performed (within the AD's time window) are made by the operator and their certificated maintenance personnel. (Document; Compliance)\n\nCompliance burden, incentives and trade-offs\n\n- Cost and downtime: The inspection consumes maintenance labour hours and may require grounding the aeroplane while work is done. Any corrective work or replacement bushings add parts and labour cost. (Document; Compliance)\n- Incentives: The AD creates a direct regulatory incentive for affected operators to prioritise the inspection within the 100-hour window to return the aircraft to permitted service. (Compliance)\n- Opportunity cost: Aircraft scheduled for this inspection may be unavailable for revenue flying during the maintenance slot. Operators may shift maintenance sequencing to minimise disruption. (Compliance)\n- Concentration of costs/benefits: The costs fall on the relatively small set of operators who own the listed serial-number aircraft; the expected safety benefit is diffuse (general reduction in risk). (Applicability; Background)\n\nImplementation risk and discretion\n\n- Technical discretion rests with certificated maintenance personnel following the Service Bulletin; outcomes depend on correct diagnosis and repair where required. (Document)\n- The AD relies on the Service Bulletin for detailed procedures. If the Bulletin is ambiguous or incomplete for a specific condition, maintenance personnel must exercise judgement; that creates an implementation risk if corrective steps are not fully specified. (Document)\n\nEffects on private enterprise and markets\n\n- Short-term: increases demand for maintenance services and possibly parts for the specific hinge pin bushings on affected aircraft. (Document; Compliance)\n- Long-term: no change to ownership or operating rules is made by the AD; it imposes a one-off (or periodic if the Service Bulletin requires follow-up) maintenance obligation tied to identified serial numbers. (Applicability; Document)\n\nSummary statement\n\n- Mechanically, this AD orders a timed inspection of the horizontal stabiliser hinge pin bushings on specific Learjet 35/36 aircraft identified by serial number in Gates Learjet SB 35/36-27-13, to be completed within 100 hours time in service after 31 December 1981, because the bushings may move out of their mating fittings in service. (Applicability; Document; Compliance; Background)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive issued in 1981. It has not expanded beyond its original purpose of addressing a specific mechanical defect in specific aircraft models."},"complexity_factors":["Very short document (approximately 150 words)","Only 4 operative provisions: applicability, document reference, compliance deadline, and background","No defined terms section","No cross-references to other legislation beyond a single service bulletin","Single, unambiguous compliance condition (time-based deadline)","No exceptions, exemptions, or conditional logic"],"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 and operators of certain Gates Learjet 35 and 36 series aircraft to inspect the horizontal stabiliser hinge pin bushings. These are small but critical components that help control the aircraft's pitch (nose up/down movement). The concern is that these bushings can slip out of position during normal flight operations, potentially affecting flight control.\n\n**Who must comply:** All Learjet 35 and 36 models with serial numbers listed in Gates Learjet Service Bulletin 35/36-27-13 (or later versions of that bulletin).\n\n**What must be done:** Operators must complete the inspection within 100 hours of flight time after 31 December 1981, following the procedures in the referenced service bulletin.\n\n**Why it matters:** Loose or displaced hinge pin bushings could compromise the horizontal stabiliser's function — a serious flight safety risk. This AD ensures potential defects are caught before they cause accidents."}},"importantCases":[],"_links":{"self":"/api/acts/ad-learjet-35-18-horizontal-stabiliser-hinge-pin-bushing-installation-inspection","history":"/api/acts/ad-learjet-35-18-horizontal-stabiliser-hinge-pin-bushing-installation-inspection/history","analysis":"/api/acts/ad-learjet-35-18-horizontal-stabiliser-hinge-pin-bushing-installation-inspection/analysis","conflicts":"/api/acts/ad-learjet-35-18-horizontal-stabiliser-hinge-pin-bushing-installation-inspection/conflicts","importantCases":"/api/acts/ad-learjet-35-18-horizontal-stabiliser-hinge-pin-bushing-installation-inspection/important-cases","documents":"/api/acts/ad-learjet-35-18-horizontal-stabiliser-hinge-pin-bushing-installation-inspection/documents"}}