{"id":"F2006B11099","name":"AD/LEARJET 35/20 - Engine Firewall Sealing","slug":"ad-learjet-35-20-engine-firewall-sealing","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56759,"registerId":"commonwealth-F2006B11099-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/LEARJET 35/20 - Engine Firewall Sealing","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 35/20 Engine Firewall Sealing 8/82\n\nApplicability: Learjet 35-001 to 35-482; Learjet 36-001 to 36-050. Document: Gates Learjet Service Bulletin SB35/36-71-2 refers. Compliance:   Within 150 hours after 31 August 1982.\n\nBackground:   Manufacturers requirement to improve fireproofing at the engine pylon firewall.\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 1982. It has not expanded beyond its original narrow purpose of addressing a specific fireproofing defect in specific aircraft serial numbers. The scope remains precisely limited to the original technical issue identified by the manufacturer."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 4 defined elements: applicability range, reference document, compliance deadline, and background","No cross-references to other legislation beyond the enabling Civil Aviation Regulations 1998","Single, unambiguous compliance action with clear deadline","No conditional logic, exceptions, or alternative compliance methods","Technical content refers to external service bulletin rather than reproducing complex specifications"],"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 35 and 36 series aircraft to improve the fireproof sealing at the engine pylon firewall (the protective barrier between the engine and the rest of the aircraft).\n\n**Who it affects:** \n- **Aircraft covered:** Learjet 35 serial numbers 001 through 482, and Learjet 36 serial numbers 001 through 050\n- **People affected:** Aircraft owners, operators, and maintenance organisations responsible for these specific Learjet models\n\n**What must be done:** The work must follow the technical instructions in **Gates Learjet Service Bulletin SB35/36-71-2** and must be completed **within 150 flight hours after 31 August 1982**.\n\n**Why it matters:** Fire in an engine nacelle can spread to the wing or fuselage if the firewall isn't properly sealed. This directive addresses a manufacturer's-identified weakness in the original fireproofing design, reducing the risk of catastrophic in-flight fire."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD’s scope, as stated in the supplied text, aligns with its declared purpose: to require improved fireproofing at the engine pylon firewall for a defined set of Learjet 35 and 36 serial numbers by mandating compliance with Gates Learjet Service Bulletin SB35/36-71-2 within a defined 150-flight-hour window after 31 August 1982 (Applicability; Document; Compliance; Background). The directive does not expand or narrow that applicability in the supplied text."},"complexity_factors":["Narrow applicability: applies to a specific, finite set of serial-numbered aircraft (Applicability).","Single, well-defined technical action: compliance requires work in accordance with a single manufacturer service bulletin (Document).","Fixed, short compliance window: compliance must occur within 150 flight hours after a specified date, creating scheduling pressure but little procedural ambiguity (Compliance).","No alternative methods or exemption procedure stated in the supplied text: leaves limited explicit administrative discretion (Document).","Dependence on external technical inputs: actual execution depends on availability of parts, trained maintenance personnel and the service bulletin details, which are external to the AD (Document)."],"plain_english_summary":"This airworthiness directive requires owners/operators of specified Learjet 35 (s/n 35‑001–35‑482) and 36 (s/n 36‑001–36‑050) aeroplanes to carry out Gates Learjet Service Bulletin SB35/36‑71‑2 to improve engine‑pylon firewall sealing. \n\nWork must be completed within 150 flight hours of 31 August 1982, creating a binding maintenance obligation and scheduling/cost burden on operators with no alternative methods or exemptions specified in the text."}},"importantCases":[],"_links":{"self":"/api/acts/ad-learjet-35-20-engine-firewall-sealing","history":"/api/acts/ad-learjet-35-20-engine-firewall-sealing/history","analysis":"/api/acts/ad-learjet-35-20-engine-firewall-sealing/analysis","conflicts":"/api/acts/ad-learjet-35-20-engine-firewall-sealing/conflicts","importantCases":"/api/acts/ad-learjet-35-20-engine-firewall-sealing/important-cases","documents":"/api/acts/ad-learjet-35-20-engine-firewall-sealing/documents"}}