{"id":"F2006B11138","name":"AD/LEARJET/21 - Aft Engine Beam - Inspection","slug":"ad-learjet-21-aft-engine-beam-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56822,"registerId":"commonwealth-F2006B11138-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LEARJET/21 - Aft Engine Beam - 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/21 Aft Engine Beam - Inspection 5/80\n\nApplicability: All models 25 with S/Nos. 25-266 to 25-300. Document:  Gates Learjet SB 25-298.\n\nCompliance: As per requirement document.\n\n \n\nBackground: To inspect the aft engine beam forward web lightening hole flanges for cracks.\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":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD’s scope is confined to inspecting aft engine beam forward web lightening hole flanges for cracks on Gates Learjet model 25 aircraft with serial numbers 25-266 to 25-300. The text does not indicate any expansion, amendment, or narrowing from an earlier scope; it sets this specific applicability and directs compliance to Gates Learjet SB 25-298 (Applicability; Document; Background)."},"complexity_factors":["Narrow applicability limited to a small serial‑number range (25-266 to 25-300) reduces operational complexity (Applicability).","The AD is short and delegates procedural detail to a single manufacturer service bulletin (Gates Learjet SB 25-298), which centralises technical complexity but keeps the AD itself simple (Document).","The AD states compliance only as “per requirement document,” creating a dependency on the service bulletin for timing, methods and thresholds; complexity shifts to that external document (Compliance).","No multiple compliance options, alternatives, or phased implementation details are specified in the AD text, lowering internal regulatory complexity but increasing reliance on the SB for operational guidance (Compliance).","Potential implementation variability depending on what the service bulletin requires (e.g., inspection technique, tooling, repair actions) introduces conditional complexity outside the AD text (Document)."],"plain_english_summary":"This Airworthiness Directive requires operators of Gates Learjet Model 25 serial numbers 25‑266 through 25‑300 to inspect the aft engine beam forward web lightening hole flanges for cracks, following Gates Learjet Service Bulletin SB 25‑298. \n\nThe Civil Aviation Safety Authority enforces compliance; affected owners/operators bear inspection, repair and downtime costs to mitigate structural risk."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused on a specific safety inspection. It has not expanded beyond its original purpose of mandating crack inspection on a defined aircraft component."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 1 defined applicability criterion (serial number range)","Single compliance requirement referencing external document","No conditional logic or nested exceptions","No cross-references to other legislation beyond the enabling regulations (CAR 1998 Part 39)","Straightforward technical scope — one inspection task on one aircraft component"],"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 does:** It requires owners and operators of specific Gates Learjet aircraft (Models 25 with serial numbers 25-266 through 25-300) to inspect a particular part of the plane — the **aft engine beam forward web lightening hole flanges** — for cracks.\n\n**Why it matters:** Cracks in this structural component could compromise the aircraft's safety. The directive references a **Service Bulletin (SB 25-298)** from the manufacturer (Gates Learjet) that contains the detailed inspection instructions. Compliance is mandatory \"as per requirement document\" — meaning operators must follow the manufacturer's bulletin exactly.\n\n**Who it affects:** Anyone operating or maintaining the specified Learjet 25 aircraft in Australia. This includes airlines, charter operators, private owners, and maintenance organisations."}},"importantCases":[],"_links":{"self":"/api/acts/ad-learjet-21-aft-engine-beam-inspection","history":"/api/acts/ad-learjet-21-aft-engine-beam-inspection/history","analysis":"/api/acts/ad-learjet-21-aft-engine-beam-inspection/analysis","conflicts":"/api/acts/ad-learjet-21-aft-engine-beam-inspection/conflicts","importantCases":"/api/acts/ad-learjet-21-aft-engine-beam-inspection/important-cases","documents":"/api/acts/ad-learjet-21-aft-engine-beam-inspection/documents"}}