{"id":"F2006B11007","name":"AD/JT9D/14 Amdt 1 - Diffuser Case Rear Rail Cracking","slug":"ad-jt9d-14-amdt-1-diffuser-case-rear-rail-cracking","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56605,"registerId":"commonwealth-F2006B11007-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/JT9D/14 Amdt 1 - Diffuser Case Rear Rail Cracking","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)  Pratt and Whitney Turbine Engines - JT9D Series\n\n \n\nAD/JT9D/14\n\nAmdt 1\n\n\nDiffuser Case Rear Rail Cracking 6/93\n\n \n\nApplicability: JT9D-7, 7A, -7H, -7AH, -7F, -7J.\n\n \n\nRequirement: Inspect the diffuser case rear rail for cracking in accordance with Pratt and Whitney Service Bulletin 5591 Revision 7.\n\n \n\nNote: FAA AD 86-11-04 refers.\n\n \n\nCompliance: Effective 27 May 1993: As detailed in the requirement document.\n\n \n\nBackground:  This Directive has been amended to reflect the manufacturer's latest revision to the requirement document. The revision, in part, introduces a new Eddy Current Inspection (ECI) probe and reduced inspection intervals for diffuser cases with weld repairs in certain locations and various crack lengths.\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":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"The directive was amended to reflect the manufacturer's latest revision to Service Bulletin 5591 (Requirement/Background). The amendment introduces a new eddy‑current inspection probe and reduces inspection intervals for diffuser cases with certain weld repairs and crack lengths, tightening inspection technique and frequency compared with the prior directive."},"complexity_factors":["Cross-reference to an external manufacturer document (Pratt & Whitney Service Bulletin 5591 Revision 7) — the AD defers procedural detail to that SB (Requirement).","Technical inspection method change: introduction of a new eddy‑current inspection (ECI) probe requires specific equipment and technique (Background).","Variable inspection frequency tied to repair status and crack lengths: reduced intervals for diffuser cases with weld repairs in certain locations and for various crack lengths increase scheduling complexity (Background).","Applicability limited to multiple specific JT9D engine variants, requiring operators to determine applicability precisely (Applicability).","Limited procedural detail in the AD itself — compliance requires consulting the service bulletin for step‑by‑step actions and thresholds (Requirement).","Regulatory cross‑reference to an FAA AD may require coordination or comparison with overseas directives (Note).","Operational costs and training burden fall on engine operators and maintenance organisations because they must acquire/qualify new ECI probes and adjust inspection programs (Requirement/Background)."],"plain_english_summary":"This directive requires operators of JT9D-7, -7A, -7H, -7AH, -7F and -7J engines to inspect the diffuser-case rear rail for cracking per Pratt & Whitney Service Bulletin 5591 Revision 7, effective 27 May 1993. It amends the earlier directive to adopt a new eddy‑current inspection probe and to reduce inspection intervals for diffuser cases with weld repairs in certain locations and for various crack lengths. Operators and maintenance organisations must follow the manufacturer's service bulletin to comply."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a routine amendment to an existing Airworthiness Directive. The scope remains tightly focused on the original safety issue (diffuser case rear rail cracking in JT9D engines). The amendment simply updates the technical requirements to reflect the manufacturer's latest service bulletin revision — it does not expand the applicability to new engine models or introduce new categories of requirements."},"complexity_factors":["Very short document (under 200 words)","Only 6 engine models specified in applicability","Single primary requirement referencing an external technical document (Service Bulletin 5591 Rev 7)","No defined terms section","No nested conditional logic or exceptions within the legislative text itself (technical complexity resides in the referenced service bulletin, not this instrument)","Simple compliance structure: effective date plus reference to external document"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). Think of it as a \"recall notice\" for aircraft parts, but legally binding.\n\n**What it does:** It requires owners and operators of specific Pratt & Whitney jet engines (the JT9D series, commonly used on older Boeing 747s and similar large aircraft) to inspect a particular engine component — the \"diffuser case rear rail\" — for cracks.\n\n**Who it affects:** Anyone operating aircraft with these specific engine models: JT9D-7, 7A, -7H, -7AH, -7F, and -7J.\n\n**What must be done:** Operators must follow Pratt & Whitney's Service Bulletin 5591 (Revision 7) to conduct the inspection. This updated version (Amendment 1) introduces:\n- A new type of crack-detection tool (an \"Eddy Current Inspection probe\" — a device that uses electromagnetic fields to find surface cracks without taking the engine apart)\n- More frequent inspections for engines that have had certain weld repairs\n- Different inspection schedules depending on how long any cracks are\n\n**Why it matters:** Cracks in engine components can lead to catastrophic engine failure. This directive prevents accidents by ensuring potential cracks are found before they become dangerous. The amendment reflects new technical knowledge from the manufacturer about where and how cracks develop."}},"importantCases":[],"_links":{"self":"/api/acts/ad-jt9d-14-amdt-1-diffuser-case-rear-rail-cracking","history":"/api/acts/ad-jt9d-14-amdt-1-diffuser-case-rear-rail-cracking/history","analysis":"/api/acts/ad-jt9d-14-amdt-1-diffuser-case-rear-rail-cracking/analysis","conflicts":"/api/acts/ad-jt9d-14-amdt-1-diffuser-case-rear-rail-cracking/conflicts","importantCases":"/api/acts/ad-jt9d-14-amdt-1-diffuser-case-rear-rail-cracking/important-cases","documents":"/api/acts/ad-jt9d-14-amdt-1-diffuser-case-rear-rail-cracking/documents"}}