{"id":"F2006B08711","name":"AD/DART/25 - High Pressure Impeller Replacement","slug":"ad-dart-25-high-pressure-impeller-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":51904,"registerId":"commonwealth-F2006B08711-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DART/25 - High Pressure Impeller Replacement","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/25 High Pressure Impeller Replacement 13/94\n\nApplicability: All Rolls Royce Dart Series engines that incorporate a pre-Mod.1475 standard High Pressure Impeller.\n\n \n\nRequirement: Replace the high pressure impeller in accordance with Rolls Royce Service Bulletin Da 72-307, Revision 5 dated Sept.94 (RR Mod.1475).\n\n \n\nNote: CAA (UK) AD 004-09-94 also refers.\n\n \n\nCompliance: Effective 8 December 1994, at the first engine shop visit at which the HP compressor area is exposed but no later than 30 June 1995.\n\n \n\nBackground: Pre-Mod 1475 H.P. Impellers have experienced vane tip failures caused by a particular mode of vibration being excited within the engine operating R.P.M. range.\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 addressing a specific mechanical defect. It has not expanded beyond its original purpose of mandating replacement of a faulty engine component."},"complexity_factors":["Single, specific mechanical component targeted (high pressure impeller)","Clear applicability test: pre-Mod.1475 standard impellers only","Single compliance pathway with two alternative deadlines (first shop visit OR fixed date)","No defined terms section — uses standard aviation terminology","No cross-references to other legislation beyond a single related UK directive","Straightforward requirement: replace part per manufacturer's bulletin"],"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) for aircraft engines.\n\n**What it does:** It requires owners and operators of certain Rolls Royce Dart engines to replace a specific part — the \"high pressure impeller\" — with an improved version. The old part (made before \"Modification 1475\") was experiencing dangerous failures where the tips of its vanes were breaking off due to vibration problems at certain engine speeds.\n\n**Who it affects:** Anyone operating aircraft with Rolls Royce Dart series engines that still have the older-style high pressure impeller installed.\n\n**What must be done:** The impeller must be replaced following Rolls Royce's official service instructions (Service Bulletin Da 72-307, Revision 5). This had to happen by the earlier of: (a) the first time the engine was opened up for maintenance after 8 December 1994, or (b) 30 June 1995.\n\n**Why it matters:** Vane tip failures in jet engines can cause catastrophic engine damage, potentially leading to engine failure in flight. This directive prevents that risk by mandating replacement of the faulty component before it can fail."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive's scope is limited to engines that incorporate a pre-Mod.1475 high-pressure impeller, as stated in the Applicability. The instrument does not expand or narrow that stated applicability elsewhere in the text; it mandates replacement for those engines only."},"complexity_factors":["Narrow technical scope: applies only to Rolls Royce Dart Series engines with pre-Mod.1475 high-pressure impellers (Applicability).","Single mandatory action: full impeller replacement, not inspection or monitoring (Requirement).","Prescribed method: replacement must follow Rolls Royce Service Bulletin Da 72-307 Rev.5, concentrating technical discretion with manufacturer documentation (Requirement).","Time-limited compliance window tied to operational events: at next shop visit exposing HP compressor or by a fixed date (Compliance).","Operational burden: requires engine shop access, parts and labour — cost and scheduling fall on operators (Compliance/Requirement).","Regulatory linkage: cross-reference to CAA (UK) AD 004-09-94 creates international compliance considerations (Note).","Technical cause identified: addresses vane-tip failures from a vibration mode in operating RPM range, implying a single remedial measure (Background)."],"plain_english_summary":"Requires replacement of the high‑pressure impeller on all Rolls‑Royce Dart engines fitted with pre‑Mod.1475 impellers, using Rolls Royce Service Bulletin Da 72-307 Rev 5 (RR Mod.1475). Operators must complete the replacement at the next engine shop visit that exposes the HP compressor or by 30 June 1995.\n\nThe AD responds to vane‑tip failures caused by a vibration mode within the operating RPM range. It assigns the technical method to the manufacturer's service bulletin and creates direct maintenance cost, scheduling and parts burdens for operators."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dart-25-high-pressure-impeller-replacement","history":"/api/acts/ad-dart-25-high-pressure-impeller-replacement/history","analysis":"/api/acts/ad-dart-25-high-pressure-impeller-replacement/analysis","conflicts":"/api/acts/ad-dart-25-high-pressure-impeller-replacement/conflicts","importantCases":"/api/acts/ad-dart-25-high-pressure-impeller-replacement/important-cases","documents":"/api/acts/ad-dart-25-high-pressure-impeller-replacement/documents"}}