{"id":"F2006B10411","name":"AD/HS 125/131 - Hydraulic System Accumulator","slug":"ad-hs-125-131-hydraulic-system-accumulator","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116085,"registerId":"commonwealth-F2006B10411-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 125/131 - Hydraulic System Accumulator","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\nAD/HS 125/131 Hydraulic System Accumulator 12/92\n\nApplicability: All model 125 up to and including the 800 series aircraft.\n\n \n\nRequirement: Unless previously carried out, action in accordance with “2. Accomplishment Instructions” contained in Mandatory Service Bulletin No 29-89-3269A.\n\n \n\nNote: Compliance with this SB has been classified as Mandatory by the UK CAA.\n\n \n\nCompliance: Prior to 31 August 1993.\n\n \n\nBackground:  Due to possible hydraulic fluid contamination of the accumulator air charge, resulting in possible compression ignition, the accumulators are to be charged with nitrogen.\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 directive implements the stated purpose in the Background by mandating the Service Bulletin instructions for the identified fleet and setting a compliance deadline. The scope described in the instrument (applicability to all BAe 125 up to and including the 800 series; mandatory compliance with the Service Bulletin; deadline) matches the operational objective stated in the Background and in the Note; the instrument does not expand or narrow that scope beyond what is stated."},"complexity_factors":["Narrow applicability limited to BAe 125 models up to and including the 800 series (Applicability).","Clear single technical requirement referenced to a specific part of a named Service Bulletin: \"2. Accomplishment Instructions\" in Mandatory Service Bulletin No 29-89-3269A (Requirement).","Fixed compliance deadline (prior to 31 August 1993) creates a simple temporal constraint (Compliance).","Safety rationale is specific and narrowly framed (hydraulic fluid contamination causing possible compression ignition) rather than broad policy changes (Background).","Directive enforces an external technical document by reference, so practical complexity depends on the technical content of that Service Bulletin rather than on the AD text itself (Requirement)."],"plain_english_summary":"### What this instrument does, in plain English\n\n- This airworthiness directive requires that all British Aerospace BAe 125 aeroplanes (models up to and including the 800 series) have their hydraulic system accumulators serviced in a specific way. (Applicability; Requirement)\n\n- The specific action to be taken is wherever \"2. Accomplishment Instructions\" in Mandatory Service Bulletin No 29-89-3269A directs. The directive makes following that part of the Service Bulletin compulsory for the affected aeroplanes. (Requirement)\n\n- The directive sets a compliance deadline: the required action must be completed prior to 31 August 1993. (Compliance)\n\n- The stated safety reason is that hydraulic fluid could contaminate the accumulator air charge and possibly cause compression ignition; to address that risk the accumulators are to be charged with nitrogen. That purpose is described in the Background. (Background)\n\n- The directive notes that the United Kingdom Civil Aviation Authority has classified compliance with the same Service Bulletin as mandatory. (Note)\n\nWho this affects and who decides\n\n- Affected parties: owners and operators of BAe 125 aeroplanes up to and including the 800 series. (Applicability)\n\n- The directive requires those owners/operators to implement the actions set out in the named Service Bulletin. The issuing authority enforces that obligation by publishing this airworthiness directive. (Requirement)\n\nHow it works mechanically\n\n- The directive does not itself describe the step-by-step maintenance tasks; it points to \"2. Accomplishment Instructions\" in Mandatory Service Bulletin No 29-89-3269A, and makes compliance with those instructions mandatory. (Requirement)\n\n- The practical change specified in the Background is that accumulators are to be charged with nitrogen to avoid possible ignition caused by hydraulic fluid contamination. (Background)\n\nCosts, incentives and trade-offs (mechanical, not normative)\n\n- Who pays: owners/operators bear the direct costs of performing the required service work (labour, materials, aircraft downtime) because the directive imposes the action on the aircraft operator through the Service Bulletin reference. (Requirement; Compliance)\n\n- Incentives: operators are required to comply by the directive; non-compliance would leave the aircraft non-compliant with the airworthiness directive. The Background provides the safety rationale (contamination risk and possible compression ignition) that creates the operational incentive to carry out the work. (Background)\n\n- Compliance burden and timing: the directive sets a fixed cutoff date (prior to 31 August 1993), concentrating the required work into the period before that date. That creates scheduling and resource effects for affected operators. (Compliance)\n\n- Effects on third parties and markets: because the directive points to a specific Mandatory Service Bulletin, maintenance providers and suppliers of whatever materials or gases are required (for example, nitrogen as stated in the Background) will be the recipients of the work and supply purchases. The directive therefore shifts maintenance demand to those performing the required instructions. (Requirement; Background)\n\nImplementation risk and discretion\n\n- The directive delegates the technical method to the Service Bulletin (\"2. Accomplishment Instructions\"). The issuing authority enforces compliance with the Service Bulletin requirement via this directive, but the AD itself does not set the step-by-step technical content — it makes those steps mandatory by reference. (Requirement)\n\n- The document does not specify any alternative compliance methods or exemptions; it mandates the Service Bulletin instructions for the affected fleet. (Requirement)\n\nSummary sentence\n\n- In short: owners/operators of BAe 125 models through the 800 series must, by 31 August 1993, carry out the instructions in Mandatory Service Bulletin No 29-89-3269A (section 2) so that hydraulic accumulators are charged with nitrogen to address a stated risk of hydraulic fluid contamination and possible compression ignition. (Applicability; Requirement; Compliance; Background; Note)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive with a single specific purpose. It has not expanded beyond its original intent of addressing the hydraulic accumulator ignition risk in the specified aircraft series."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 1 defined applicability criterion (aircraft model range)","Single requirement referencing an external document (the Service Bulletin)","No nested conditions, exceptions, or cross-references to other legislation","Simple compliance deadline with no alternative methods or escalations","Background explanation is straightforward technical safety rationale"],"plain_english_summary":"This is an **Airworthiness Directive** (AD) — essentially a mandatory safety order for aircraft. It applies to **British Aerospace BAe 125 series aeroplanes** (models up to and including the 800 series).\n\n**What it does:**\n- Requires aircraft owners/operators to follow specific instructions in **Mandatory Service Bulletin No. 29-89-3269A** (a technical notice from the manufacturer)\n- Specifically, it mandates that **hydraulic system accumulators** (pressure storage devices in the aircraft's hydraulic system) must be **charged with nitrogen** rather than whatever gas they might currently use\n\n**Why it matters:**\n- **Safety risk:** Hydraulic fluid could contaminate the air charge inside the accumulator, potentially causing **compression ignition** (essentially an explosion risk from heat generated by compressing contaminated gas)\n- **Deadline:** Had to be done before **31 August 1993**\n- **Authority:** The UK Civil Aviation Authority (CAA) classified this as mandatory, and Australia's CASA adopted it\n\n**Who it affects:**\n- Owners and operators of older BAe 125 business jets in Australia\n- Maintenance organisations servicing these aircraft"}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-125-131-hydraulic-system-accumulator","history":"/api/acts/ad-hs-125-131-hydraulic-system-accumulator/history","analysis":"/api/acts/ad-hs-125-131-hydraulic-system-accumulator/analysis","conflicts":"/api/acts/ad-hs-125-131-hydraulic-system-accumulator/conflicts","importantCases":"/api/acts/ad-hs-125-131-hydraulic-system-accumulator/important-cases","documents":"/api/acts/ad-hs-125-131-hydraulic-system-accumulator/documents"}}