{"id":"F2006B10497","name":"AD/HS 125/58 - Landing Gear Hydraulic System - Inspection and Modification","slug":"ad-hs-125-58-landing-gear-hydraulic-system-inspection-and-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116257,"registerId":"commonwealth-F2006B10497-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 125/58 - Landing Gear Hydraulic System - Inspection and 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)  British Aerospace BAe 125 Series Aeroplanes\n\n \n\n# AD/HS 125/58 Landing Gear Hydraulic System - Inspection\n\nand Modification\n\nApplicability: All models without Modification No. 252837. Document:  British Aerospace 125 SB No. 32-190.\n\nCompliance: Before 1 April 1982.\n\n# 11/81\n\n \n\nBackground:  Blockage of a landing gear restrictor valve may prevent lowering of the gear by either the normal or the auxiliary hydraulic system. Filters are introduced at each side of the restrictor valves.\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 from 1981 with a narrow, specific purpose. It has not expanded beyond its original scope of addressing a specific hydraulic system defect in a specific aircraft series."},"complexity_factors":["Very short document (approximately 150 words)","Only 4 operative provisions: applicability, document reference, compliance deadline, and background","No defined terms section","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","Single condition (applicability based on absence of one specific modification number)","Straightforward mandatory action with clear technical reference"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\n- Requires owners and operators of **British Aerospace BAe 125 series aircraft** to inspect and modify the landing gear hydraulic system.\n- Specifically, it mandates installing **filters on both sides of restrictor valves** in the landing gear hydraulic system.\n\n**Why it matters:**\n- A blocked restrictor valve could prevent the landing gear from lowering using either the normal or backup (auxiliary) hydraulic system — a serious safety risk during landing.\n- The filters prevent debris from blocking these valves.\n\n**Who must comply:**\n- Anyone operating a BAe 125 aircraft that does **not** already have **Modification No. 252837** installed.\n\n**Deadline:**\n- The work had to be completed **before 1 April 1982**.\n\n**How to comply:**\n- Follow the instructions in **British Aerospace Service Bulletin No. 32-190** (the technical manual for this fix)."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive, as written, sets an obligation for all BAe 125 models that do not already have Modification No. 252837 to be inspected and modified by the stated date. The text does not indicate any change from an earlier or different scope; it simply defines the current scope as those aircraft without the stated modification and prescribes the remedial action and deadline. (Applicability; Compliance; Background)"},"complexity_factors":["Narrow and explicit applicability: applies to \"All models without Modification No. 252837.\" (Applicability)","Single, fixed compliance deadline: \"Before 1 April 1982.\" (Compliance)","Technical action referenced to a single manufacturer service bulletin: \"British Aerospace 125 SB No. 32‑190.\" (Document)","Clear stated hazard and straightforward mitigation: restrictor valve blockage; install filters on each side of the restrictor valves. (Background)","No discretionary provisions, alternative compliance routes, or exemptions set out in the text (Compliance; Applicability)"],"plain_english_summary":"This directive requires owners/operators of British Aerospace BAe 125 series aeroplanes without Modification No. 252837 to inspect and fit filters to each side of the landing‑gear restrictor valves per British Aerospace SB No. 32‑190, to mitigate the risk that valve blockage could prevent gear lowering.\n\nIssued by the Civil Aviation Safety Authority, compliance is mandatory by 1 April 1982 and the cost and arrangement of the work fall to the aircraft owners/operators."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-125-58-landing-gear-hydraulic-system-inspection-and-modification","history":"/api/acts/ad-hs-125-58-landing-gear-hydraulic-system-inspection-and-modification/history","analysis":"/api/acts/ad-hs-125-58-landing-gear-hydraulic-system-inspection-and-modification/analysis","conflicts":"/api/acts/ad-hs-125-58-landing-gear-hydraulic-system-inspection-and-modification/conflicts","importantCases":"/api/acts/ad-hs-125-58-landing-gear-hydraulic-system-inspection-and-modification/important-cases","documents":"/api/acts/ad-hs-125-58-landing-gear-hydraulic-system-inspection-and-modification/documents"}}