{"id":"F2006B06684","name":"AD/RRT-S/3 - Stage 2 and 3 H.P. Compressor Discs - Increased Thickness Neck and Diaphragm","slug":"ad-rrt-s-3-stage-2-and-3-h-p-compressor-discs-increased-thickness-neck-and-diaphragm","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":48707,"registerId":"commonwealth-F2006B06684-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/RRT-S/3 - Stage 2 and 3 H.P. Compressor Discs - Increased Thickness Neck and Diaphragm","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 - Spey Series\n\n \n\nAD/RRT-S/3 Stage 2 and 3 H.P. Compressor Discs - Increased\n\nThickness Neck and Diaphragm\n\n\n9/74\n\n \n\nApplicability: Spey 505-5F, 506-14, 506-14A, 506-14AW, 506-14D, 511-5W, 511-8, 511-14, 511-\n\n14W, 555-15.\n\n \n\nRequirement: Rolls Royce Spey SB No. Sp 72-715 Part 1 and Part 2.\n\n \n\nCompliance: As per the requirement document or at 4000 disc cycles, whichever occurs first.\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\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 known defect in specific engine models. It has not expanded beyond its original purpose of mandating a particular hardware modification to prevent compressor disc failures."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 3 operative provisions: applicability, requirement, and compliance","No defined terms section - relies entirely on external technical reference (Rolls-Royce Service Bulletin Sp 72-715)","Single cross-reference to external technical document rather than internal legislative structure","Simple conditional compliance trigger: 'whichever occurs first' is the only logical operator","No exceptions, exemptions, or nested conditions within the directive itself"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA) that mandates safety modifications to specific Rolls-Royce Spey jet engines used in aircraft.\n\n**What it does:**\n- Requires owners and operators of certain Spey engine models to inspect and modify the **Stage 2 and 3 High Pressure (H.P.) Compressor Discs** by installing versions with **increased thickness at the neck and diaphragm** areas.\n- The modification addresses a structural weakness in the original compressor discs that could lead to cracking or failure under stress.\n\n**Who it affects:**\n- Aircraft operators using Rolls-Royce Spey engines with these specific model numbers: 505-5F, 506-14, 506-14A, 506-14AW, 506-14D, 511-5W, 511-8, 511-14, 511-14W, and 555-15.\n- This typically includes operators of aircraft like the BAC One-Eleven, Fokker F28, and certain military aircraft that use these engines.\n\n**Why it matters:**\n- **Safety critical:** Compressor disc failures can cause catastrophic engine damage and potentially lead to loss of aircraft control.\n- **Mandatory compliance:** Operators must follow the technical instructions in Rolls-Royce Service Bulletin Sp 72-715 (Parts 1 and 2) and complete the work either according to that document's timeline **or** by the time the disc reaches 4,000 flight cycles—whichever comes first.\n- **Legal obligation:** Non-compliance means the aircraft cannot legally operate in Australian airspace."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD, as presented, sets a mandatory requirement for the listed Spey engine models to comply with Rolls Royce Service Bulletin Sp 72-715 Part 1 and Part 2 or act at 4,000 disc cycles. The text does not indicate any expansion or narrowing of the affected models or the compliance trigger beyond what is explicitly stated in Applicability and Compliance; therefore the scope, as set out, has not changed from the directive's stated requirements."},"complexity_factors":["Concise directive but technically dependent on an external manufacturer Service Bulletin (Sp 72-715 Part 1 and Part 2) for procedural detail","Compliance timing contains a monitoring requirement ('or at 4000 disc cycles, whichever occurs first') requiring life‑tracking of components","Multiple specific engine variants listed in applicability increases the population of affected operators","AD text does not include the technical remedy or inspection steps, so implementers must obtain and interpret the Service Bulletin","Legal force is clear (Part 39 AD) but operational details rest with manufacturer document rather than the AD itself"],"plain_english_summary":"This Airworthiness Directive makes compliance with Rolls‑Royce Service Bulletin Sp 72‑715 Parts 1 and 2 mandatory for operators of the specified Rolls‑Royce Spey engines.  \n\nOperators must perform the Bulletin’s modifications/inspections either on the Bulletin’s schedule or by 4,000 compressor‑disc cycles, whichever comes first; operators bear the costs and must track disc cycles to ensure compulsory compliance under Part 39."}},"importantCases":[],"_links":{"self":"/api/acts/ad-rrt-s-3-stage-2-and-3-h-p-compressor-discs-increased-thickness-neck-and-diaphragm","history":"/api/acts/ad-rrt-s-3-stage-2-and-3-h-p-compressor-discs-increased-thickness-neck-and-diaphragm/history","analysis":"/api/acts/ad-rrt-s-3-stage-2-and-3-h-p-compressor-discs-increased-thickness-neck-and-diaphragm/analysis","conflicts":"/api/acts/ad-rrt-s-3-stage-2-and-3-h-p-compressor-discs-increased-thickness-neck-and-diaphragm/conflicts","importantCases":"/api/acts/ad-rrt-s-3-stage-2-and-3-h-p-compressor-discs-increased-thickness-neck-and-diaphragm/important-cases","documents":"/api/acts/ad-rrt-s-3-stage-2-and-3-h-p-compressor-discs-increased-thickness-neck-and-diaphragm/documents"}}