{"id":"F2006B03470","name":"AD/BAe 146/18 - Pylon to Engine Front Mount Yoke Bush","slug":"ad-bae-146-18-pylon-to-engine-front-mount-yoke-bush","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":43024,"registerId":"commonwealth-F2006B03470-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BAe 146/18 - Pylon to Engine Front Mount Yoke Bush","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)  British Aerospace BAe 146 Series Aeroplanes\n\n \n\nAD/BAe 146/18 Pylon to Engine Front Mount Yoke Bush 2/90\n\nApplicability: Series 200 S/No. E2106, E2111, E2115, E2121 and E2127. Series 300 S/No. E3128, E3131 and E3134.\n\n \n\nRequirement: Action in accordance with BAe SB 54-4. Compliance:  In accordance with the Requirement Document.\n\nBackground: There has been a report of the subject bush being found incorrectly installed.\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, targeted safety directive addressing a specific mechanical defect on specific aircraft. It has not expanded beyond its original purpose of mandating inspection/repair of the yoke bush installation."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 2 substantive operative provisions: applicability and requirement","No defined terms section — relies entirely on external reference to BAe SB 54-4","Simple conditional logic: if aircraft serial number matches list, then compliance required","No nested exceptions or cross-references to other legislation","Single background fact pattern with straightforward safety rationale"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to specific British Aerospace BAe 146 aircraft (a regional jet airliner).\n\n**What it does:**\n- Requires owners/operators of certain BAe 146 aircraft to inspect and fix a specific mechanical part: the \"bush\" (a cylindrical lining) in the engine front mount yoke on the pylon (the structure that attaches the engine to the wing).\n- The directive references a British Aerospace Service Bulletin (SB 54-4) which contains the detailed instructions for what needs to be done.\n\n**Who it affects:**\n- Operators of specific BAe 146 aircraft with serial numbers: E2106, E2111, E2115, E2121, E2127 (Series 200), and E3128, E3131, E3134 (Series 300).\n\n**Why it matters:**\n- An incorrectly installed bush was discovered on one aircraft. If left uncorrected, this could potentially lead to engine mount failure — a serious safety risk. The directive ensures all affected aircraft get checked and fixed before the problem causes an accident.\n\n**Key point:** This is a **compliance document** — aircraft cannot legally fly unless this inspection/repair is completed as specified."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive's scope is confined to addressing the reported incorrect installation of the pylon-to-engine front mount yoke bush and applies only to the specific serial numbers listed. The stated background (a report of incorrect installation) aligns with the AD's requirement to follow BAe SB 54-4; there is no indication in the provided text that the directive's scope departs from that stated purpose (Background; Applicability; Requirement)."},"complexity_factors":["Narrow applicability limited to eight specific airframe serial numbers (low population of affected units) (Applicability).","Directive refers to an external technical document (BAe SB 54-4) for the required work rather than containing procedural detail itself (Requirement; Compliance).","AD text does not state timing, inspection intervals, or detailed acceptance criteria within the directive (Requirement; Compliance).","Operational impacts depend on the content, clarity and availability of the referenced Service Bulletin (implementation risk) (Requirement).","Compliance and enforcement are straightforward legally but practically require coordination between operators and maintenance organisations (Compliance)."],"plain_english_summary":"This AD requires operators of eight specific BAe 146 airframes to carry out the inspection/rectification in BAe Service Bulletin 54-4 to detect and correct an incorrectly installed pylon-to-engine front mount yoke bush.  \n\nIt makes compliance with that SB mandatory, placing inspection, repair, downtime and parts costs on the affected operators/maintenance providers and relying on the SB for all technical and timing details."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bae-146-18-pylon-to-engine-front-mount-yoke-bush","history":"/api/acts/ad-bae-146-18-pylon-to-engine-front-mount-yoke-bush/history","analysis":"/api/acts/ad-bae-146-18-pylon-to-engine-front-mount-yoke-bush/analysis","conflicts":"/api/acts/ad-bae-146-18-pylon-to-engine-front-mount-yoke-bush/conflicts","importantCases":"/api/acts/ad-bae-146-18-pylon-to-engine-front-mount-yoke-bush/important-cases","documents":"/api/acts/ad-bae-146-18-pylon-to-engine-front-mount-yoke-bush/documents"}}