{"id":"F2006B11024","name":"AD/JT9D/30 - First Stage High Pressure Turbine Disk","slug":"ad-jt9d-30-first-stage-high-pressure-turbine-disk","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56632,"registerId":"commonwealth-F2006B11024-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/JT9D/30 - First Stage High Pressure Turbine Disk","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/30 First Stage High Pressure Turbine Disk 6/98\n\nApplicability: Pratt and Whitney JT9D series engines incorporating high pressure turbine disks specified in FAA AD 97-25-10.\n\n \n\nRequirement: Inspect affected high pressure turbine disks in accordance with the technical requirements of FAA AD 97-25-10.\n\n \n\nNote: FAA AD 97-25-10 supersedes FAA AD 91-04-10.\n\n \n\nCompliance: Unless previously accomplished, as detailed in the Requirement document.\n\n \n\nThis airworthiness directive becomes effective on 21 May 1998.\n\n \n\nBackground: This Directive is prompted by reports of cracks in certain high pressure turbine disks at cooling hole and tie bolt hole locations.\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 safety issue with a specific engine component. It has not expanded beyond its original purpose of mandating inspections for cracked turbine disks."},"complexity_factors":["Very short document (approximately 200 words)","Only 1 defined term implicitly referenced (FAA AD 97-25-10)","No nested conditional logic or exceptions","Single straightforward requirement: comply with external US directive","No cross-references to other Australian legislation beyond Civil Aviation Regulations 1998 Part 39","Simple structure: Applicability → Requirement → 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).\n\n**What it does:**\nIt requires airlines and aircraft operators to inspect specific Pratt & Whitney JT9D jet engines for dangerous cracks in a critical component called the \"first stage high pressure turbine disk.\" This disk is a spinning part inside the engine that operates under extreme heat and stress.\n\n**Who it affects:**\n- Airlines and operators using Pratt & Whitney JT9D series engines (commonly found on older Boeing 747s and similar large aircraft)\n- Maintenance crews responsible for engine inspections\n\n**Why it matters:**\nCracks in turbine disks can lead to catastrophic engine failure — potentially causing an uncontained engine failure where metal parts burst through the engine casing. This directive was triggered by actual reports of cracks forming at cooling holes and bolt holes in these disks. The directive makes compliance with an American safety order (FAA AD 97-25-10) mandatory in Australia.\n\n**Key points:**\n- **Effective date:** 21 May 1998\n- **Action required:** Inspect specific turbine disks following US technical standards\n- **Urgency:** Unless already done, operators must comply with the inspection requirements"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This AD adopts the technical requirements of FAA AD 97-25-10 and notes that FAA AD 97-25-10 supersedes FAA AD 91-04-10, so the directive updates and replaces the earlier FAA-specified inspection requirements (Note). The change aligns Australian mandatory inspections with the later FAA directive and its specified affected disks and inspection procedures (Applicability; Requirement; Note)."},"complexity_factors":["Cross-reference to an external technical document (FAA AD 97-25-10) — requires obtaining and following another regulator's detailed procedures (Note).","Technical inspection work on safety‑critical rotating parts — needs specialised maintenance facilities, tooling and trained personnel (Background: cracks at cooling and tie‑bolt holes).","Applicability limited to specific JT9D engines/disks — requires operators to determine if their engines match the listed parts (Applicability).","Compliance timing and documentation enforcement by CASA — operators must schedule compliance and retain evidence (Compliance; Effective date 21 May 1998).","Potential for consequential actions (repair/part replacement) following inspection — creates variable cost and operational disruption depending on findings (Requirement and Background)."],"plain_english_summary":"This airworthiness directive requires operators of Pratt & Whitney JT9D engines that use the specified high‑pressure turbine disks to perform inspections described in FAA Airworthiness Directive 97-25-10. It matters because reports of cracks at cooling‑hole and tie‑bolt locations raise a risk to engine integrity; operators must schedule and pay for the inspections and any follow-up maintenance. The directive took effect 21 May 1998 and enforces the FAA‑specified inspection procedure in Australian regulation."}},"importantCases":[],"_links":{"self":"/api/acts/ad-jt9d-30-first-stage-high-pressure-turbine-disk","history":"/api/acts/ad-jt9d-30-first-stage-high-pressure-turbine-disk/history","analysis":"/api/acts/ad-jt9d-30-first-stage-high-pressure-turbine-disk/analysis","conflicts":"/api/acts/ad-jt9d-30-first-stage-high-pressure-turbine-disk/conflicts","importantCases":"/api/acts/ad-jt9d-30-first-stage-high-pressure-turbine-disk/important-cases","documents":"/api/acts/ad-jt9d-30-first-stage-high-pressure-turbine-disk/documents"}}