{"id":"F2006B10557","name":"AD/HS 748/22 - Main Hydraulic Accumulators - Corrosion Inspection","slug":"ad-hs-748-22-main-hydraulic-accumulators-corrosion-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116377,"registerId":"commonwealth-F2006B10557-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 748/22 - Main Hydraulic Accumulators - Corrosion 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)  British Aerospace (Hawker Siddeley) HS 748 Series Aeroplanes\n\n \n\n# AD/HS 748/22 Main Hydraulic Accumulators - Corrosion\n\nInspection\n\nApplicability: British Aerospace HS748 aircraft.\n\n# 7/97\n\n \n\nRequirement: Inspect the main hydraulic accumulators for corrosion and repair as required, in accordance with British Aerospace Service Bulletin HS748-29-49 issued Feb 25/97.\n\n \n\nCompliance: Within 30 days from effective date of this Directive and thereafter every two years.\n\n \n\nThis Airworthiness Directive becomes effective on 19 June 1997.\n\n \n\nBackground: Extensive corrosion has been found under the mounting brackets of the main hydraulic accumulators of an operator's aircraft during unscheduled maintenance which required removal of the accumulators.\n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive implements the stated original aim in the background — to detect and address corrosion found under accumulator mounting brackets — by requiring inspections and repairs for HS 748 main hydraulic accumulators in accordance with the manufacturer’s service bulletin and on a fixed timetable (initial inspection within 30 days, then every two years). The scope is limited to that aircraft type and that component and does not expand beyond the stated inspection-and-repair requirement."},"complexity_factors":["Narrow applicability: only British Aerospace HS 748 series aeroplanes (Applicability).","Single-component focus: main hydraulic accumulators only (Requirement; Background).","Reference to external technical document: compliance requires following British Aerospace Service Bulletin HS748-29-49 for inspection and repair procedures (Requirement).","Simple compliance timeline: initial inspection within 30 days, then every two years (Compliance).","Repair discretion: repairs are required \"as required\" by inspection results, with technical scope determined by the service bulletin and maintenance judgement (Requirement)."],"plain_english_summary":"- What this directive does, mechanically:\n  - Applies to: British Aerospace HS 748 series aeroplanes. (Applicability)\n  - Requires operators to inspect the main hydraulic accumulators for corrosion and to carry out any repairs indicated by that inspection. The inspections and repairs must follow British Aerospace Service Bulletin HS748-29-49 (issued 25 Feb 1997). (Requirement)\n  - Sets timing: the first inspection must be done within 30 days of the directive becoming effective and then repeated every two years. (Compliance)\n  - Effective date: 19 June 1997. (This Airworthiness Directive becomes effective on 19 June 1997.)\n\n- Why it was issued (as stated in the directive):\n  - The background note records that extensive corrosion was found under the mounting brackets of the main hydraulic accumulators on an operator's aircraft during unscheduled maintenance, and removal of the accumulators was required. That observation is the stated basis for requiring inspections. (Background)\n\n- Who pays and who decides:\n  - Aircraft operators (the owners or operators of HS 748 aeroplanes) are required to arrange and pay for the inspections and any repairs. The directive sets the mandatory action and timing; the detailed inspection and repair procedures are specified by the manufacturer’s service bulletin and must be followed. (Applicability; Requirement)\n\n- Behaviour changes required:\n  - Operators must schedule and carry out an initial inspection within 30 days and then schedule recurring inspections every two years. Operators must also carry out repairs if corrosion is found, using the procedures in the referenced service bulletin. (Compliance; Requirement)\n\n- Costs, incentives and trade-offs (source-grounded):\n  - Direct costs to operators: time and money to perform the inspections and to procure and perform repairs where corrosion is found. The directive does not state how large those costs will be; it only prescribes obligation and timing. (Requirement; Compliance)\n  - Incentives: operators have a regulatory incentive to inspect and repair on schedule to meet the directive’s mandatory timetable. (Compliance)\n  - Opportunity costs and scheduling impacts: the need for inspections within 30 days and then biennially may require operators to prioritise maintenance slots, potentially affecting aircraft availability. The directive itself sets the timing but does not allocate resources or compensation. (Compliance)\n\n- Implementation, compliance burden and discretion:\n  - The directive delegates technical detail to the manufacturer’s service bulletin (HS748-29-49). That bulletin determines inspection and repair methods; the AD requires adherence to it. This means compliance depends on access to and use of those manufacturer procedures. (Requirement)\n  - The AD requires repairs “as required” by inspection results; the scope of repairs follows the service bulletin and the judgement of the maintenance provider following those procedures. The AD does not itself specify repair thresholds. (Requirement)\n\n- Effects on private enterprise and independent maintenance providers (source-grounded):\n  - The directive imposes a compliance obligation on operators, which may be discharged by the operator’s maintenance organisation, whether in-house or independent. The AD’s technical direction refers operators to a specific manufacturer service bulletin for the required procedures; that reference shapes which inspection and repair methods are acceptable for compliance. (Requirement)\n\n- Net description of scope and risk from the source text:\n  - The AD is narrowly targeted at a specific component (main hydraulic accumulators) on a specific aircraft type (HS 748), requires periodic inspection and repair per a cited service bulletin, and was issued after corrosion was found during maintenance on an operator’s aircraft. It prescribes timing (initial 30 days, then every two years) but leaves technical detail and repair decisions to the service bulletin and qualified maintenance personnel. (Applicability; Requirement; Compliance; Background)\n"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific corrosion issue identified in service. It has not expanded beyond its original purpose of ensuring hydraulic accumulator integrity on HS748 aircraft."},"complexity_factors":["Single, specific mechanical component targeted (main hydraulic accumulators)","Only one technical reference document to follow (British Aerospace Service Bulletin HS748-29-49)","Simple compliance timeline: initial 30-day window, then biennial recurrence","No defined terms section or interpretation provisions","No conditional exceptions or nested logic — applies to all HS748 aircraft uniformly","Extremely short document (approximately 150 words of substantive content)","Single applicability criterion (aircraft model type)"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). Think of it like a compulsory recall notice, but for aircraft parts rather than consumer goods.\n\n**What it does:** It requires owners and operators of British Aerospace HS748 aircraft to inspect the main hydraulic accumulators (pressure storage tanks in the plane's hydraulic system) for corrosion damage. If corrosion is found, it must be repaired.\n\n**Who must follow it:** Anyone operating British Aerospace HS748 aircraft in Australia. This includes airlines, charter companies, and private owners.\n\n**How to comply:**\n- **First inspection:** Within 30 days of 19 June 1997\n- **Repeat inspections:** Every two years after that\n- **Method:** Follow the specific instructions in British Aerospace Service Bulletin HS748-29-49 (dated 25 February 1997)\n\n**Why it matters:** Corrosion was discovered under the mounting brackets during unscheduled maintenance on one operator's aircraft. This hidden damage could potentially cause hydraulic system failure — a serious safety risk. The directive ensures all similar aircraft are checked before corrosion becomes dangerous.\n\n**Key point:** This is **retrospective** — it applies to existing aircraft, not just new ones. Non-compliance means the aircraft cannot legally fly."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-748-22-main-hydraulic-accumulators-corrosion-inspection","history":"/api/acts/ad-hs-748-22-main-hydraulic-accumulators-corrosion-inspection/history","analysis":"/api/acts/ad-hs-748-22-main-hydraulic-accumulators-corrosion-inspection/analysis","conflicts":"/api/acts/ad-hs-748-22-main-hydraulic-accumulators-corrosion-inspection/conflicts","importantCases":"/api/acts/ad-hs-748-22-main-hydraulic-accumulators-corrosion-inspection/important-cases","documents":"/api/acts/ad-hs-748-22-main-hydraulic-accumulators-corrosion-inspection/documents"}}