{"id":"F2006B11028","name":"AD/JT9D/35 - HPT Disc Inspection","slug":"ad-jt9d-35-hpt-disc-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56636,"registerId":"commonwealth-F2006B11028-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\n\n![](image.001.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (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\nPratt and Whitney Turbine Engines \\- JT9D Series","sortOrder":0},{"sectionNumber":"AD/JT9D/35 HPT Disc Inspection 4/2002","sectionType":"part","heading":"AD/JT9D/35 HPT Disc Inspection 4/2002","content":"# AD/JT9D/35 HPT Disc Inspection 4/2002\n\nApplicability: Pratt and Whitney JT9D-7R4 series engines.\n\nRequirement: Initial action and repeat inspection in accordance with the requirements of FAA AD 2001-17-30.\n\nCompliance: As detailed in the requirement document with a revised effective date of 18 April 2002.\n\nThis Airworthiness Directive becomes effective on 18 April 2002.\n\nBackground: HPT stage 1 disc firtrees are found to fail due to interaction with the adjoining air seal. This Directive requires replacement of some seals, and introduces an initial and repetitive inspection along with a terminating action to address a potential uncontained engine failure mode.\n\n![Signature of Eugene Paul Holzapfel Delegate of the Civil Aviation Safety Authority](image.002.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 10 March 2002\n\n![](image.001.png)","sortOrder":1}],"analysis":{"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"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific mechanical failure mode in a specific engine series. It does not expand beyond the original safety issue identified."},"complexity_factors":["Very short document (under 300 words)","Only 4 structural sections (Applicability, Requirement, Compliance, Background)","Single cross-reference to external FAA directive (AD 2001-17-30) — actual technical instructions are contained there, not here","No defined terms section — assumes technical aviation knowledge","No nested exceptions or conditional logic — straightforward mandatory action","Simple temporal trigger (effective date) with compliance delegated to external document"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspections, recurring checks, and replacement of certain air seals on Pratt & Whitney JT9D-7R4 series engines to address cracking of HPT stage‑1 disc firtrees caused by seal contact. The action prevents possible uncontained engine failures that could damage aircraft or injure people. It affects operators of aircraft fitted with these engines (commonly older Boeing 747 and Airbus A300/A310) and took effect 18 April 2002, with a specified terminating action."},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":false,"description":"No material change in scope. The AD adopts and enforces the requirements of FAA AD 2001-17-30 for Pratt & Whitney JT9D‑7R4 engines, specifies replacement of certain seals, initial and repetitive inspections, and a terminating action, and sets the effective date as 18 April 2002 (Applicability; Requirement; Compliance; Background)."},"complexity_factors":["External-reference dependency: the AD requires compliance “in accordance with the requirements of FAA AD 2001-17-30”, so full compliance depends on an external, technical document (Requirement).","Technical engineering content: the unsafe condition concerns HPT stage‑1 disc firtree interaction with an adjoining air seal — a specialist metallurgical/engineering issue (Background).","Multiple required actions: the instrument mandates seal replacement, initial and repetitive inspections, and a terminating action — multiple operational steps increase implementation complexity (Requirement; Background).","Operational burden on operators: inspections, part replacement and any terminating action create direct maintenance costs, aircraft downtime and scheduling impacts for engine owners/operators (Requirement).","Narrow but concentrated applicability: applies only to Pratt & Whitney JT9D‑7R4 engines, so a small set of operators face concentrated compliance obligations (Applicability).","Timing and legal effect: a revised effective date (18 April 2002) and formal issuance under subregulation 39.1(1) CAR 1998 impose a legal compliance deadline and delegated authority considerations (Compliance; opening paragraph).","Safety consequence linkage: the AD addresses potential uncontained engine failure, which affects operational risk assessments and may trigger broader fleet-level inspections or grounding decisions (Background).","Traceability and audit: relying on an FAA AD for procedures requires operators and regulators to track versions and amendments of the external document to remain compliant (Requirement)."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of Pratt & Whitney JT9D‑7R4 engines to perform initial and recurring inspections of the high‑pressure turbine (HPT) stage‑1 disc firtrees, replace certain air seals, and complete a terminating action as specified in FAA AD 2001‑17‑30. It takes effect 18 April 2002.\n\nThe measure responds to reported contact between the HPT disc firtrees and an adjoining air seal that can cause disc failure and risk an uncontained engine failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-jt9d-35-hpt-disc-inspection","history":"/api/acts/ad-jt9d-35-hpt-disc-inspection/history","analysis":"/api/acts/ad-jt9d-35-hpt-disc-inspection/analysis","conflicts":"/api/acts/ad-jt9d-35-hpt-disc-inspection/conflicts","importantCases":"/api/acts/ad-jt9d-35-hpt-disc-inspection/important-cases","documents":"/api/acts/ad-jt9d-35-hpt-disc-inspection/documents"}}