{"id":"F2006B06397","name":"AD/PW4000/7 Amdt 1 - Low Pressure Turbine Fourth Stage Airseal","slug":"ad-pw4000-7-amdt-1-low-pressure-turbine-fourth-stage-airseal","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":47713,"registerId":"commonwealth-F2006B06397-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PW4000/7 Amdt 1 - Low Pressure Turbine Fourth Stage Airseal","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\nAIRWORTHINESS 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 revokes Airworthiness Directive (AD) AD/PW4000/7 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\nPratt & Whitney Turbine Engines \\- PW4000 Series\n\nAD/PW4000/7\n\nAmdt 1\n\n  \nLow Pressure Turbine Fourth Stage Airseal 11/2001\n\nDM\n\nApplicability: PW4000 series engines incorporating low pressure turbine 4th stage airseal, P/No 50N478 or 50N478-001.\n\nRequirement: Replace low pressure turbine 4th stage airseals, P/No 50N478 or 50N478-001 in accordance with the technical requirements of FAA AD 2001-05-07.\n\nCompliance: Comply with the requirements of this airworthiness directive at the periods specified in FAA AD 2001-05-07.\n\nNote: FAA AD 2001-05-07 supersedes FAA AD 2000-25-06.\n\nThis Amendment becomes effective on 3 October 2001.\n\nBackground: This Airworthiness Directive is prompted by reports of cracked low pressure turbine 4th stage airseals. Seal fracture could result in an uncontained engine failure leading to damage to the aircraft.\n\nThis amendment references new FAA AD 2001-05-07 which supersedes FAA AD 2000-25-06 to correct an error relating to engines affected by P7W SB PW4 ENG 72- 657, Revision 1.\n\nThe original issue of this Airworthiness Directive became effective 31 January 2001.\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 24 September 2001\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 3 October 2001.\n\n  \nPage 1 of 1","sortOrder":0}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"This amendment does not broaden the subject matter or add new categories of affected engines. It updates the Australian directive to adopt FAA AD 2001-05-07 (which supersedes the earlier FAA AD) to correct an error about which engines were affected by a service bulletin. Mechanically the change is an administrative update and clarification rather than an expansion of scope or new regulatory reach."},"complexity_factors":["Very short single-page directive","Single, specific applicability (two part numbers: 50N478 and 50N478-001)","One core requirement (replace airseals)","Direct cross-reference to an external FAA AD for technical steps and compliance timing (FAA AD 2001-05-07)","No nested exceptions or multiple conditional branches","Revokes prior Australian AD and adopts updated FAA AD (administrative cross-reference)"],"plain_english_summary":"**What this instrument does (mechanics)**\n\n- Revokes the earlier Australian Airworthiness Directive AD/PW4000/7 and replaces it with this amended directive (Amdt 1).\n- Applies to Pratt & Whitney PW4000 series engines that have a fourth-stage low-pressure turbine airseal with part number 50N478 or 50N478-001 (Applicability).\n- Requires replacement of those specific 4th-stage low-pressure turbine airseals in accordance with the technical steps and timing set out in FAA Airworthiness Directive 2001-05-07 (Requirement; Compliance).\n- The compliance times are the same as those specified in FAA AD 2001-05-07; FAA AD 2001-05-07 supersedes FAA AD 2000-25-06 (Note; Compliance).\n- The amendment took effect 3 October 2001 (Effective date).\n\n**Why it matters (safety rationale)**\n\n- The directive was issued because there were reports of cracked low-pressure turbine 4th-stage airseals (Background).\n- A fractured airseal can be thrown from the engine and could cause an uncontained engine failure, which risks damage to the aircraft (Background).\n\n**Who it affects**\n\n- Aircraft operators and maintenance organisations that operate aircraft fitted with PW4000 engines containing the specific airseal part numbers 50N478 or 50N478-001 (Applicability).\n- Maintenance suppliers and parts vendors who provide the specified airseals or replacement services.\n\n**Who pays, who decides, and what behaviour changes**\n\n- Who pays: the aircraft operators (or their maintenance contractors) bear the direct costs — purchasing replacement airseals, labour to remove/install parts, and any aircraft downtime.\n- Who decides: the Civil Aviation Safety Authority (CASA) delegate enforces the directive in Australia by mandating compliance with the FAA AD; technical method and timing are taken from FAA AD 2001-05-07 (Requirement; Compliance). Maintenance providers implement the work according to those instructions.\n- Behavioural change required: affected operators must inspect/replace the identified airseals following the FAA AD’s procedures and at the FAA AD’s specified intervals. That may require scheduling maintenance checks, ordering parts, and grounding aircraft until the work is done.\n\n**Costs, incentives and trade-offs**\n\n- Direct costs: parts, labour and aircraft downtime. These are concentrated on operators of the affected engines.\n- Safety benefits: reduce the risk of airseal fracture and uncontained engine failures for those engines.\n- Incentives: operators trade immediate maintenance expense and downtime against avoiding more severe damage, liability and operational disruption from an in-service failure.\n- Opportunity cost: maintenance resources (hangar time, skilled technicians, replacement parts) allocated to this work cannot be used for other fleet maintenance during the same windows.\n\n**Implementation risks and compliance burden**\n\n- Compliance burden is procedural: follow the FAA AD instructions. CASA exercises little technical discretion here because the AD adopts the FAA requirements.\n- Implementation risks include parts availability (supply constraints for the specified airseals), scheduling capacity at maintenance facilities, and ensuring record-keeping and traceability that the mandated replacements have been completed.\n\n**Market effects and competitive issues**\n\n- The directive channels demand for the specific replacement parts and maintenance services to whichever suppliers (including the OEM) can supply approved parts and work packages.\n- If replacement parts are only available from the original manufacturer or authorised suppliers, that concentrates demand and can temporarily raise prices or create lead-time bottlenecks.\n\n**Concentrated benefits and diffuse costs**\n\n- Benefits (reduced risk of engine failure) are concentrated on operators, passengers and airworthiness regulators; costs (replacement, downtime) fall directly on operators and indirectly on their customers.\n\n**Document provenance and relation to earlier instruments**\n\n- This amendment references and requires compliance with FAA AD 2001-05-07, which superseded FAA AD 2000-25-06. The stated purpose of referencing the newer FAA AD was to correct an error relating to a service bulletin (P7W SB PW4 ENG 72-657, Revision 1) and thereby clarify which engines/parts were affected (Background).\n\n(Referenced sections: Applicability; Requirement; Compliance; Note; Background.)"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment maintains the original scope of addressing unsafe airseals in PW4000 engines. The change is purely corrective — fixing an error that excluded certain engines from the original directive. The fundamental purpose (mandating replacement of cracked airseals to prevent engine failure) remains unchanged."},"complexity_factors":["Short, single-page document with clear structure (Applicability, Requirement, Compliance, Background)","Only 2 specific part numbers identified as affected","Single mandatory action (replacement of component)","Cross-reference to external technical document (FAA AD 2001-05-07) for detailed compliance timing and procedures — operators must obtain and follow this separate document","No nested exceptions or conditional logic within the directive itself","Minimal defined terms (relies on standard aviation terminology)"],"plain_english_summary":"This CASA Airworthiness Directive mandates replacement of a cracked low‑pressure turbine 4th‑stage airseal (PN 50N478/50N478‑001) on Pratt & Whitney PW4000 engines because cracking can cause uncontained engine failure. It applies to operators of affected aircraft and requires compliance with the FAA’s technical and compliance timelines (FAA AD 2001‑05‑07). This Amendment 1 corrects an earlier omission and took effect 3 October 2001."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pw4000-7-amdt-1-low-pressure-turbine-fourth-stage-airseal","history":"/api/acts/ad-pw4000-7-amdt-1-low-pressure-turbine-fourth-stage-airseal/history","analysis":"/api/acts/ad-pw4000-7-amdt-1-low-pressure-turbine-fourth-stage-airseal/analysis","conflicts":"/api/acts/ad-pw4000-7-amdt-1-low-pressure-turbine-fourth-stage-airseal/conflicts","importantCases":"/api/acts/ad-pw4000-7-amdt-1-low-pressure-turbine-fourth-stage-airseal/important-cases","documents":"/api/acts/ad-pw4000-7-amdt-1-low-pressure-turbine-fourth-stage-airseal/documents"}}