{"id":"F2006B10573","name":"AD/HS 748/8 - Engine Subframe/Wing Attachment Assembly","slug":"ad-hs-748-8-engine-subframe-wing-attachment-assembly","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116409,"registerId":"commonwealth-F2006B10573-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HS 748/8 - Engine Subframe/Wing Attachment Assembly","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\nAD/HS 748/8 Engine Subframe/Wing Attachment Assembly 13/94\n\nApplicability: All HS748 aircraft.\n\n \n\nRequirement: Action in accordance with British Aerospace Mandatory Service Bulletin 54/29.\n\n \n\nNote: UK CAA AD 026-11-86 refers.\n\n \n\nCompliance: As specified in the Requirement Document.\n\n \n\nBackground:  Undetected abnormal movement and wear of the engine subframe/wing attachment assembly can lead to the failure of the split bush and/or taper bolt, which can cause severe stress and damage to the engine support structure.\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 in a specific aircraft type. It has not expanded beyond its original purpose of mandating inspection/repair of the engine subframe/wing attachment assembly."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 1 defined applicability (all HS748 aircraft)","Single requirement referencing an external technical document (British Aerospace Mandatory Service Bulletin 54/29)","No nested conditional logic or exceptions","No cross-references to other legislation beyond a single note referencing UK CAA AD","Straightforward compliance structure ('as specified in the Requirement Document')","Standardised AD format with predictable sections (Applicability, Requirement, Note, Compliance, Background)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order — issued by Australia's Civil Aviation Safety Authority (CASA) for a specific type of aircraft: the **British Aerospace (Hawker Siddeley) HS 748** series.\n\n**What it does:**\n- Requires owners and operators of all HS 748 aircraft to inspect and potentially repair the **engine subframe/wing attachment assembly** — the structural connection between the engine mounting frame and the aircraft wing.\n- The work must follow **British Aerospace Mandatory Service Bulletin 54/29**, which contains the detailed technical instructions.\n\n**Why it matters:**\n- **Safety risk:** Undetected wear or abnormal movement in this assembly can cause the **split bush** (a type of bearing sleeve) or **taper bolt** to fail. If that happens, the engine support structure can suffer severe stress and damage — potentially leading to engine separation or structural failure in flight.\n- **Mandatory compliance:** This isn't optional. Aircraft cannot legally fly unless this directive is followed within the timeframe specified in the service bulletin.\n\n**Who it affects:**\n- Operators of HS 748 aircraft in Australia (these are typically regional turboprop aircraft, though many are now retired or in limited service).\n- Maintenance organisations responsible for keeping these aircraft airworthy.\n\n**Key point:** This directive references a UK Civil Aviation Authority AD (026-11-86), showing how Australian aviation safety rules often align with or adopt international standards, particularly from the UK where these aircraft were originally designed and manufactured."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD applies to all HS 748 aircraft and mandates compliance with British Aerospace Mandatory Service Bulletin 54/29 as specified in the Requirement Document. The text provided does not indicate any amendment or narrowing/widening of scope from an earlier or original intent; it presents a single, fleet-wide maintenance obligation tied to the Service Bulletin and cites a related UK CAA AD. (Applicability; Requirement; Note)"},"complexity_factors":["The AD itself is short and refers to an external Mandatory Service Bulletin (54/29) for technical detail rather than setting procedures in the AD text (Requirement).","Technical work involves structural components (engine subframe/wing attachment, split bush, taper bolt) that typically require specialised maintenance skills and parts (Background; Requirement).","The compliance timing and detailed steps are contained in the Requirement Document, which is not reproduced here, leaving implementation specifics to that external document (Compliance).","Applicability is broad (all HS 748 aircraft), creating a uniform obligation across the fleet but varying operational impact depending on each operator’s maintenance status and spare-part availability (Applicability).","Cross-reference to UK CAA AD indicates alignment with foreign regulator action, which may require operators to consult multiple documents to understand full regulatory context (Note)."],"plain_english_summary":"What this instrument does, in plain terms:\n\n- It requires every operator of a British Aerospace (Hawker Siddeley) HS 748 aeroplane to carry out the maintenance actions set out in British Aerospace Mandatory Service Bulletin 54/29. (Requirement; Applicability)\n- The legal obligation is to follow the Service Bulletin; the AD says compliance must be \"as specified in the Requirement Document.\" (Requirement; Compliance)\n\nWhy the regulator issued this requirement:\n\n- The AD states that abnormal movement and wear in the engine subframe/wing attachment assembly can go undetected and may cause the split bush and/or taper bolt to fail. Such a failure can place severe stress on, and damage, the engine support structure. That is the safety risk the measures are intended to address. (Background)\n\nWho is affected and who pays:\n\n- All HS 748 aircraft operators are directly affected because the AD applies to the entire fleet of that type. (Applicability)\n- Operators will bear the direct costs of implementing the Service Bulletin: inspections, parts, labour, and any aircraft downtime required by the work. (Requirement; Compliance)\n\nWho decides and who performs the work:\n\n- The Civil Aviation Safety Authority issued the AD as part of the Schedule of Airworthiness Directives; the AD mandates that operators act in accordance with the manufacturer’s Mandatory Service Bulletin. (Schedule of Airworthiness Directives; Requirement)\n- The detailed technical steps, timeframes and specified parts are set out in the referenced Service Bulletin and the Requirement Document; maintenance providers who carry out the work must follow those instructions. (Requirement; Compliance)\n\nHow it changes behaviour and the practical effects:\n\n- Operators must schedule and carry out the specified inspections/repairs/modifications for their HS 748 aircraft according to the Service Bulletin and the Requirement Document. (Requirement; Compliance)\n- This typically increases maintenance activity for affected aircraft: it may raise short-term maintenance costs, create demand for specified parts and specialised labour, and cause aircraft to be out of service for the duration of the work. (Requirement; Compliance)\n\nTrade-offs, implementation risks, and compliance burdens (mechanical, not political):\n\n- The directive shifts the cost of addressing the identified mechanical risk onto operators (labour, parts, and downtime). (Applicability; Requirement)\n- The AD delegates the exact inspection intervals, thresholds and procedures to the Mandatory Service Bulletin and Requirement Document; without those texts included here, the technical difficulty, required tooling, or parts lead times are not stated in the AD itself. That creates dependency on the manufacturer document for implementation detail. (Requirement; Compliance)\n- If parts are scarce or the work is technically specialised, operators could face extended grounding or higher repair costs. The AD does not specify mitigation for those supply or scheduling constraints. (Requirement; Compliance)\n\nEffects on independent businesses and markets:\n\n- Independent maintenance organisations can perform the work if they can comply with the Service Bulletin’s technical requirements; demand for maintenance and parts for HS 748 aircraft will increase while the AD remains in force. (Requirement; Compliance)\n- The AD does not change ownership rights or contracting freedom directly; it creates a regulatory obligation that affects commercial choices about scheduling, outsourcing maintenance, or retiring aircraft. (Applicability; Requirement)\n\nOther references:\n\n- The AD notes that a UK CAA airworthiness directive (AD 026-11-86) is related. That cross-reference signals the issue was recognised by the UK regulator and the Australian AD adopts the manufacturer’s Service Bulletin as the means of compliance. (Note)\n\nIn short: the AD requires all HS 748 operators to carry out the specific manufacturer-prescribed maintenance actions to address wear and movement at the engine subframe/wing attachment. Operators must follow the Mandatory Service Bulletin and the Requirement Document, and they will incur the associated maintenance costs, scheduling and logistical consequences. (Applicability; Requirement; Compliance; Background)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-748-8-engine-subframe-wing-attachment-assembly","history":"/api/acts/ad-hs-748-8-engine-subframe-wing-attachment-assembly/history","analysis":"/api/acts/ad-hs-748-8-engine-subframe-wing-attachment-assembly/analysis","conflicts":"/api/acts/ad-hs-748-8-engine-subframe-wing-attachment-assembly/conflicts","importantCases":"/api/acts/ad-hs-748-8-engine-subframe-wing-attachment-assembly/important-cases","documents":"/api/acts/ad-hs-748-8-engine-subframe-wing-attachment-assembly/documents"}}