{"id":"F2006B11091","name":"AD/LEARJET 35/13 - Upper Cabin Door Lock Mechanism Bolts - Modification","slug":"ad-learjet-35-13-upper-cabin-door-lock-mechanism-bolts-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56751,"registerId":"commonwealth-F2006B11091-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LEARJET 35/13 - Upper Cabin Door Lock Mechanism Bolts - 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)  Gates Learjet 35 and 36 Series Aeroplanes\n\n \n\n# AD/LEARJET 35/13  Upper Cabin Door Lock Mechanism Bolts - Modification\n\nApplicability: All model 35 with S/Nos. 35-001 to 35-274 and 278;\n\n \n\nAll model 36 with S/Nos. 36-001 to 36-044.\n\n# 4/80\n\n \n\nRequirement: Modify the upper cabin door lock mechanism bolts by installing Gates Learjet Kit No. AMK 79-9.\n\n \n\nCompliance: Within 150 hours time in service after 30 April 1980.\n\n \n\nBackground: Modification kit AMK 79-9 provides an additional safety feature to the upper cabin door lock mechanism by installing drilled bolts and lockwiring these bolts in-situ.\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 imposes a single, specified modification on a defined set of aircraft serial numbers. It does not expand or narrow applicability beyond the listed models and serial numbers, nor does it introduce additional obligations or alternative measures. The scope remains to mandate the installation of Kit No. AMK 79-9 on the named aircraft within the stated compliance window. (Applicability; Requirement; Compliance)"},"complexity_factors":["Narrow applicability limited to specific serial-number ranges for Learjet 35 and 36 (clear target population). (Applicability)","Single specified corrective action (install Gates Learjet Kit No. AMK 79-9) rather than multiple options. (Requirement)","Clear compliance timeframe (150 hours time in service after 30 April 1980) reducing scheduling ambiguity. (Compliance)","No stated exemptions, alternatives, or phased implementation details that would add regulatory complexity. (Requirement)","Implementation requires hands-on maintenance skill (drilled bolts and lockwiring), introducing a practical execution requirement rather than regulatory interpretation. (Background)","Dependence on a specific manufacturer kit creates potential supply/availability complexity for operators. (Requirement)"],"plain_english_summary":"### What this directive does (mechanical change)\n\nThis airworthiness directive requires that operators install Gates Learjet Kit No. AMK 79-9 on specified Learjet 35 and 36 aircraft. The installation modifies the upper cabin door lock mechanism bolts by replacing/altering them so they are drilled and then lockwired in place (the bolts are made capable of being safety-wired in-situ). (Requirement; Background)\n\n### Who it affects\n\n- Aircraft operators, owners and maintenance providers for the following aeroplanes: all Learjet 35 with serial numbers 35-001 to 35-274 and 35-278, and all Learjet 36 with serial numbers 36-001 to 36-044. (Applicability)\n- The Civil Aviation Safety Authority (CASA) is the issuing authority of the directive (header: Civil Aviation Safety Authority / Schedule of Airworthiness Directives).\n\n### When it must be done\n\nThe modification must be completed within 150 hours time in service after 30 April 1980. That is the compliance window set by the directive. (Compliance)\n\n### Why the directive says it is needed\n\nThe directive states the modification \"provides an additional safety feature to the upper cabin door lock mechanism\" because the bolts are drilled and lockwired, which prevents loosening or loss of the bolts in service. This is presented as the official purpose of the kit. (Background)\n\n### Who pays and who decides\n\n- Operators/owners pay for the kit (Gates Learjet Kit No. AMK 79-9), the labour to install it, and any associated downtime or maintenance scheduling costs. (Requirement; Compliance)\n- CASA decides the mandatory action by issuing the airworthiness directive. Compliance is not optional for the affected serial-numbered aircraft. (header; Applicability)\n\n### Incentives, trade-offs and compliance burden\n\n- Incentives: Completing the modification reduces the risk that the upper cabin door lock bolts will work loose in service (the stated safety benefit). (Background)\n- Trade-offs and opportunity costs: Operators must allocate maintenance time and budget to procure the specified kit and install it, which may require aircraft downtime that could otherwise be used for revenue flights or other maintenance tasks. (Requirement; Compliance)\n- Compliance burden: The directive specifies a single prescribed kit (AMK 79-9) and a firm time-in-service compliance window (150 hours after 30 April 1980). Operators must source that kit and schedule an appropriately certified maintenance action within the timeframe and retain records showing compliance. (Requirement; Compliance)\n\n### Implementation risks and verification\n\n- Installation quality: The safety outcome depends on correct installation and proper lockwiring technique; improper installation could reduce the intended safety benefit. This places responsibility on qualified maintenance personnel and the operator’s maintenance procedures. (Requirement; Background)\n- Supply risk: The directive names a specific manufacturer kit, so availability of that kit affects the operator’s ability to comply on time. (Requirement)\n- Verification: Compliance is verifiable by maintenance records and physical inspection of the drilled and lockwired bolts. (Requirement; Compliance)\n\n### Effects on private choice and market aspects\n\n- Operators must choose to buy the specified kit and schedule a maintenance action to comply; this constrains operator choice to the specified modification method in the directive. (Requirement)\n- The directive does not address alternatives, exemptions or cost-sharing mechanisms; it mandates a particular hardware solution for the listed serial-numbered aircraft. (Requirement)\n\nSections cited: (Applicability), (Requirement), (Compliance), (Background)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope: a specific safety modification for specific aircraft models. There is no evidence of scope creep — it addresses exactly one mechanical issue on exactly two aircraft models with defined serial numbers."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 2 defined applicability criteria (specific serial number ranges)","Single, unambiguous requirement with no conditional logic or exceptions","No cross-references to other legislation or regulations","Simple compliance deadline (fixed hours-in-service after a specific date)","No nested definitions or interpretive provisions"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires owners and operators of specific Gates Learjet 35 and 36 aircraft to modify the bolts on the upper cabin door lock mechanism.\n\n**Who it affects:**\n- Owners and operators of Learjet model 35 aircraft with serial numbers 35-001 through 35-274 and 278\n- Owners and operators of Learjet model 36 aircraft with serial numbers 36-001 through 36-044\n\n**What must be done:**\nInstall a specific modification kit (Gates Learjet Kit No. AMK 79-9) that replaces the existing upper cabin door lock mechanism bolts with **drilled bolts** (bolts with holes drilled through them) and **lockwires** them in place. Lockwiring is a safety technique where wire is threaded through holes in bolts and twisted to prevent them from loosening during flight.\n\n**Why it matters:**\nThe modification adds a critical safety feature to prevent the upper cabin door lock bolts from coming loose. If these bolts failed in flight, the cabin could depressurize or the door could separate from the aircraft — a potentially catastrophic event.\n\n**Deadline:**\nThe modification must be completed within 150 hours of flight time after 30 April 1980."}},"importantCases":[],"_links":{"self":"/api/acts/ad-learjet-35-13-upper-cabin-door-lock-mechanism-bolts-modification","history":"/api/acts/ad-learjet-35-13-upper-cabin-door-lock-mechanism-bolts-modification/history","analysis":"/api/acts/ad-learjet-35-13-upper-cabin-door-lock-mechanism-bolts-modification/analysis","conflicts":"/api/acts/ad-learjet-35-13-upper-cabin-door-lock-mechanism-bolts-modification/conflicts","importantCases":"/api/acts/ad-learjet-35-13-upper-cabin-door-lock-mechanism-bolts-modification/important-cases","documents":"/api/acts/ad-learjet-35-13-upper-cabin-door-lock-mechanism-bolts-modification/documents"}}