{"id":"F2006B08700","name":"AD/DART/13 - Low Pressure Impeller Hub Shim","slug":"ad-dart-13-low-pressure-impeller-hub-shim","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":51878,"registerId":"commonwealth-F2006B08700-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DART/13 - Low Pressure Impeller Hub Shim","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 - 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Rolls Royce Turbine Engines - Dart Series\n\n \n\nAD/DART/13 Low Pressure Impeller Hub Shim 11/87\n\nApplicability: All Dart RDa-6, RDa-7 series engines.\n\n \n\nRequirement: 1. Action in accordance with Rolls Royce SB Da 72-430 Rev 2; or\n\n \n\n2. AD/RRT/23.\n\n \n\nCompliance:  As detailed in Requirement Document. Background: Reissue of AD/RRT/23.\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 standard, narrow airworthiness directive focused on a specific mechanical component in specific engine models. It has not expanded beyond its original safety purpose. The reissue nature (Background: 'Reissue of AD/RRT/23') suggests consolidation or administrative updating rather than scope expansion."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 2 defined applicability criteria (engine model series)","Simple binary compliance pathway (Option 1 OR Option 2)","No nested exceptions or conditional logic","No cross-references to other legislation beyond a single service bulletin and one superseded directive","Single technical requirement with straightforward alternative compliance method"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety notice issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft engines.\n\n**What it does:**\nThis directive requires owners and operators of specific Rolls Royce Dart engines (the RDa-6 and RDa-7 series) to take action regarding a **low pressure impeller hub shim** — a small mechanical spacer component inside the engine's compressor section.\n\n**Who must comply:**\nAnyone operating aircraft with these specific Dart engine models.\n\n**What action is required:**\nOperators must follow one of two paths:\n- **Option 1:** Carry out the maintenance actions specified in Rolls Royce Service Bulletin Da 72-430 (Revision 2); OR\n- **Option 2:** Comply with a different directive called AD/RRT/23.\n\n**Why it matters:**\nThis directive was reissued to ensure engine safety. The \"hub shim\" is a critical component that helps maintain proper alignment and spacing in the engine's low-pressure compressor. If this part fails or is improperly maintained, it could lead to engine damage or failure — a serious safety risk in aviation. The directive gives operators flexibility in how they achieve compliance while ensuring the safety standard is met.\n\n**Key point:** This is a **reissue** of an earlier directive (AD/RRT/23), meaning the safety requirement itself isn't new, but the way it's presented or referenced has been updated."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The instrument is described as a reissue of AD/RRT/23 (Background) and retains the same stated applicability (all Dart RDa-6, RDa-7 series engines) and the same compliance route (action in accordance with Rolls Royce SB Da 72-430 Rev 2 or AD/RRT/23). The text gives no indication of a change in scope from the prior AD; confirming any substantive change would require comparing the referenced AD/RRT/23 and the service bulletin themselves. (Applicability; Requirement; Background)"},"complexity_factors":["Short, single-issue directive focused on a specific engine component (low pressure impeller hub shim). (Applicability)","Delegation to external technical documents (Rolls Royce SB Da 72-430 Rev 2) or another AD (AD/RRT/23) for the substantive steps and timing. (Requirement; Compliance)","Lack of technical detail or timelines within the AD text itself increases reliance on referenced documents. (Requirement; Compliance)","Reissue status references prior AD (AD/RRT/23), which requires cross-checking previous instruments to confirm continuity or changes. (Background)"],"plain_english_summary":"What this instrument changes mechanically\n\n- This airworthiness directive applies to all Rolls Royce Dart RDa-6 and RDa-7 series turbine engines. (Applicability)\n- It requires that the corrective action for the low pressure impeller hub shim be carried out either by following Rolls Royce Service Bulletin Da 72-430 Rev 2 or by complying with AD/RRT/23. (Requirement)\n- The timing and specific steps for compliance are those set out in the referenced requirement document(s). (Compliance)\n\nOfficial rationale and immediate provenance\n\n- The text states that this instrument is a reissue of AD/RRT/23. (Background)\n\nWho decides, who pays, and what behaviour changes\n\n- The regulator (the Civil Aviation Safety Authority, via this AD) decides that operators of the listed engines must follow the corrective action described in the referenced documents. (Applicability; Requirement)\n- The owners/operators of affected engines are the parties required to take the action; any costs or downtime associated with the action will therefore fall on them, subject to specifics in the referenced requirement document. (Requirement; Compliance)\n- The concrete behavioural change is: operators must carry out the work set out in Rolls Royce SB Da 72-430 Rev 2 or AD/RRT/23 in order to meet the AD’s compliance requirement. (Requirement; Compliance)\n\nMechanics of delegation, incentives and practical trade-offs\n\n- The AD does not itself set out technical steps; it delegates the technical specification and timing to an external manufacturer service bulletin and/or another AD. This makes compliance contingent on documents outside the AD’s text. (Requirement; Compliance)\n- Because the AD directs operators to follow the manufacturer’s service bulletin or another AD, the manufacturer and the referenced AD-holder effectively supply the procedural detail that determines labour, parts, and downtime. Those details will determine the actual cost and operational impact on operators. (Requirement; Compliance)\n\nImplementation risk, compliance burden and discretion\n\n- Implementation depends on access to and interpretation of the referenced documents (Rolls Royce SB Da 72-430 Rev 2 or AD/RRT/23). The AD itself provides no technical guidance or timelines in its text, so risk arises from any ambiguity or variation in those external documents. (Requirement; Compliance)\n- The compliance burden is concentrated on the operators of the specified engine series because they must perform the actions mandated by the referenced documents. The AD does not specify exemptions or cost relief. (Applicability; Requirement)\n\nMarket and business effects (limited to what the text supports)\n\n- The AD sets a mandatory maintenance requirement for a defined set of engines. That obligation can affect operators’ maintenance scheduling, parts procurement, and aircraft availability, but the AD does not quantify those effects; the scale depends on the actions specified in the referenced requirement document. (Applicability; Requirement; Compliance)\n\nNotes on scope and provenance\n\n- This AD is explicitly described as a reissue of AD/RRT/23; it therefore continues an existing regulatory requirement under a new instrument. (Background)\n\nCited provisions: Applicability; Requirement; Compliance; Background."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dart-13-low-pressure-impeller-hub-shim","history":"/api/acts/ad-dart-13-low-pressure-impeller-hub-shim/history","analysis":"/api/acts/ad-dart-13-low-pressure-impeller-hub-shim/analysis","conflicts":"/api/acts/ad-dart-13-low-pressure-impeller-hub-shim/conflicts","importantCases":"/api/acts/ad-dart-13-low-pressure-impeller-hub-shim/important-cases","documents":"/api/acts/ad-dart-13-low-pressure-impeller-hub-shim/documents"}}