{"id":"F2006B11128","name":"AD/LEARJET/12 - Control System Stop Bolts - Replacement","slug":"ad-learjet-12-control-system-stop-bolts-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56806,"registerId":"commonwealth-F2006B11128-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LEARJET/12 - Control System Stop Bolts - Replacement","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/12 Control System Stop Bolts - Replacement 9/75\n\nApplicability: All model 24 with S/Nos. 24-100 to 24-304 and 24-309 to 24-322, and all model 25\n\nwith S/Nos. 25-003 to 25-197. Document: Gates Learjet SB 23/24/25-266.\n\nCompliance: Within 300 hours time in service after 31 October 1975.\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 issued in 1975 (as indicated by the '9/75' designation and October 1975 compliance baseline). It addresses a specific technical defect in specific aircraft and has not expanded beyond its original narrow scope. Airworthiness Directives are inherently limited-purpose instruments by design."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 4 defined elements: applicability (specific serial numbers), document reference, compliance deadline, and subject matter","No cross-references to other legislation or regulations beyond the enabling authority (Civil Aviation Regulations 1998, Part 39)","Single, unambiguous compliance action (replacement of stop bolts)","Clear, fixed deadline with simple calculation method (300 hours time in service after a specific date)","No conditional logic, exceptions, or alternative compliance methods","Straightforward applicability criteria based on aircraft model and serial number ranges"],"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) under the Civil Aviation Regulations 1998.\n\n**What it requires:** Owners and operators of specific Gates Learjet 24 and 25 series aircraft must **replace certain \"stop bolts\" in the control system**. These bolts are mechanical components that limit how far control surfaces (like flaps or flight controls) can move.\n\n**Who it affects:**\n- **Learjet Model 24** aircraft with serial numbers 24-100 through 24-304, and 24-309 through 24-322\n- **Learjet Model 25** aircraft with serial numbers 25-003 through 25-197\n\n**The deadline:** The replacement must be completed **within 300 hours of flight time** after 31 October 1975.\n\n**Why it matters:** Stop bolts are critical safety components. If they fail or are improperly installed, pilots could lose proper control of the aircraft. This AD mandates a fix based on a manufacturer service bulletin (Gates Learjet SB 23/24/25-266), ensuring these specific aircraft remain safe to fly.\n\n**Key point:** This is not optional — compliance is legally required for these aircraft to maintain their airworthiness certificate (official permission to fly)."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive sets out a specific, unchanged scope: identified Learjet model 24 and 25 aircraft within the listed serial-number ranges must have control-system stop bolts replaced per Gates Learjet SB 23/24/25-266 within 300 hours after 31 October 1975. The source text contains no amendment or broadened scope language."},"complexity_factors":["Narrow and explicit applicability by model and serial number (straightforward to identify affected fleet). (Applicability)","Single clear compliance deadline measured in flight hours from a fixed calendar date (300 hours after 31 October 1975). (Compliance)","Technical execution delegated to an external service bulletin rather than set out in the directive (requires consulting a separate document). (Document)","Limited textual detail in the directive itself — the technical and procedural specifics are contained in the referenced Service Bulletin, increasing dependence on that external document for implementation. (Document)","Vintage date and model identifiers may create practical issues (e.g. locating SB, parts or maintenance capability) even though not specified in the directive text. (Applicability; Document)"],"plain_english_summary":"This directive requires replacement of control‑system stop bolts on specified Gates Learjet 24 and 25 aeroplanes, to be carried out per Gates Learjet Service Bulletin 23/24/25‑266 within 300 hours time‑in‑service after 31 October 1975. It affects owners/operators and maintenance organisations for the listed serial numbers, who bear parts, labour and downtime costs; the Civil Aviation Safety Authority enforces compliance to address the identified airworthiness concern."}},"importantCases":[],"_links":{"self":"/api/acts/ad-learjet-12-control-system-stop-bolts-replacement","history":"/api/acts/ad-learjet-12-control-system-stop-bolts-replacement/history","analysis":"/api/acts/ad-learjet-12-control-system-stop-bolts-replacement/analysis","conflicts":"/api/acts/ad-learjet-12-control-system-stop-bolts-replacement/conflicts","importantCases":"/api/acts/ad-learjet-12-control-system-stop-bolts-replacement/important-cases","documents":"/api/acts/ad-learjet-12-control-system-stop-bolts-replacement/documents"}}