{"id":"F2006B11025","name":"AD/JT9D/31 Amdt 1 - 14th and 15th Stage HPC Disks","slug":"ad-jt9d-31-amdt-1-14th-and-15th-stage-hpc-disks","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56633,"registerId":"commonwealth-F2006B11025-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/JT9D/31 Amdt 1 - 14th and 15th Stage HPC Disks","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \n![](image.002.png)  \nPratt and Whitney Turbine Engines \\- JT9D Series\n\nAIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\n![](image.002.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/JT9D/31 and issues the following AD under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\nAD/JT9D/31\n\nAmdt 1\n\n  \n14th and 15th Stage HPC Disks 8/2000\n\nApplicability: Pratt and Whitney JT9D-59A, -70A, 7Q, -7Q3, and JT9D-7R4 series engines incorporating 14th and 15th stage high pressure compressor disks as detailed in FAA AD 98-21-22R1.\n\nRequirement: Inspect and replace as necessary 14th and 15th stage high compressor disks in accordance with the technical requirements of FAA AD 98-21-22R1.\n\nNote: P&W Alert SBs JT9D-7R4-72-524, Rev1 and A6232, Rev 2, also refer.\n\nCompliance: Initial and repeat instructions, as detailed in the Requirement document, with the effective date amended to 10 August 2000.\n\nThis Airworthiness Directive becomes effective on 10 August 2000.\n\nBackground: This Directive is prompted by reports of disk bore cracks detected in certain 14th and 15th stage HPC disks during engine shop visits. Such cracks could result in an uncontained engine failure and damage to the aircraft.\n\nThis amendment updates the Requirement document to reference the latest revision of FAA AD 98-21-22. AD 98-21-22R1 makes reference to specific P&W NDI procedures and provides a revised definition of an engine shop visit that is less onerous than originally specified.\n\nThe original issue of this AD became effective on 28 January 1999.\n\n![Signature of Eugene Paul Holzapfel Delegate of the Civil Aviation Safety Authority](image.003.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 23 June 2000\n\n![](image.002.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 12 July 2000.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment maintains the original scope — safety inspections of specific engine components. The amendment is purely technical: it updates the referenced FAA document to its latest revision and adjusts the definition of 'engine shop visit' to be less onerous. No expansion of affected engine types, no new categories of compliance, no policy drift from the original safety purpose."},"complexity_factors":["Short, single-purpose instrument (approximately 400 words)","Only 5 defined engine model variants in applicability section","Single cross-reference to external technical document (FAA AD 98-21-22R1) — actual technical requirements are 'incorporated by reference' rather than reproduced","Simple conditional structure: if engine type X, then do action Y","No nested exceptions or complex definitional provisions","Clear, linear compliance timeline (effective date plus referenced schedule)"],"plain_english_summary":"This AD revokes and replaces a previous directive, mandating inspection and replacement of certain 14th/15th stage high‑pressure compressor disks in Pratt & Whitney JT9D engines by requiring compliance with FAA AD 98‑21‑22R1. It affects owners/operators of JT9D‑series engines with those disks. Cracks found in these disks risk uncontained engine failure; the amendment also eases the compliance burden by adopting a revised definition of an “engine shop visit.” Non‑compliance is legally binding."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"Yes. The amendment updates the Requirement to reference FAA AD 98‑21‑22R1 (rather than the earlier FAA AD) and amends the effective date to 10 August 2000 (Requirement; Compliance). FAA AD 98‑21‑22R1 adds explicit P&W NDI procedures and revises the definition of an 'engine shop visit' to be less onerous; the core duty to inspect and replace affected 14th/15th stage HPC disks remains, but the triggers and approved inspection methods have been narrowed/clarified (Background)."},"complexity_factors":["Cross-reference to an external FAA AD (98‑21‑22R1) rather than containing full inspection procedures in the instrument (Requirement).","Reliance on specific P&W non‑destructive inspection (NDI) procedures and service bulletins, requiring specialist technical skills and judgment (Background; Note).","Multiple engine variants and narrowly defined parts (14th and 15th stage HPC disks) increase applicability-checking complexity (Applicability).","Amendment changes effective date and updates the definition of an 'engine shop visit', altering timing and trigger events for compliance (Compliance; Background).","Obligation for initial and repeat inspections imposes ongoing operational and record‑keeping burdens on operators (Compliance; Requirement)."],"plain_english_summary":"This Airworthiness Directive requires operators of Pratt & Whitney JT9D-59A, -70A, -7Q, -7Q3 and -7R4 engines that incorporate 14th and 15th stage high‑pressure compressor (HPC) disks to inspect and, if necessary, replace those disks following the technical procedures of FAA AD 98‑21‑22R1 and related P&W service bulletins. It is effective 10 August 2000. Operators pay for inspections and replacements; the CASA delegate enforces compliance by mandating the FAA‑referenced procedures (Applicability; Requirement; Compliance; Background)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-jt9d-31-amdt-1-14th-and-15th-stage-hpc-disks","history":"/api/acts/ad-jt9d-31-amdt-1-14th-and-15th-stage-hpc-disks/history","analysis":"/api/acts/ad-jt9d-31-amdt-1-14th-and-15th-stage-hpc-disks/analysis","conflicts":"/api/acts/ad-jt9d-31-amdt-1-14th-and-15th-stage-hpc-disks/conflicts","importantCases":"/api/acts/ad-jt9d-31-amdt-1-14th-and-15th-stage-hpc-disks/important-cases","documents":"/api/acts/ad-jt9d-31-amdt-1-14th-and-15th-stage-hpc-disks/documents"}}