{"id":"F2010L02549","name":"AD/PW4000/21 - 2nd Stage High Pressure Turbine Air Seal Assembly","slug":"ad-pw4000-21-2nd-stage-high-pressure-turbine-air-seal-assembly","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":84484,"registerId":"commonwealth-F2010L02549-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Pratt and Whitney Turbine Engines - PW40","sectionType":"division","heading":"Pratt and Whitney Turbine Engines - PW4000 Series","content":"### Pratt and Whitney Turbine Engines - PW4000 Series\n\n| AD/PW4000/21 | 2nd Stage High Pressure TurbineAir Seal Assembly | 20/2010 |\n| ------------ | ------------------------------------------------ | ------- |\n\n| Applicability: | Pratt and Whitney PW4000 engines as specified by models in FAA AD 2001-20-02.                                                                                                                                                                                                                                                                                                                                                                                                                                        |\n| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Unless previously accomplished, perform the actions in accordance with the technical requirements of FAA AD 2001-20-02.Repeat the actions in accordance with the technical requirements of FAA AD2001-20-02.Later revisions to PW ASB PW4G-112-A72-233, Revision 3, dated 3 August 2001, approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2001-20-02, are considered acceptable for compliance with the equivalent Requirements of this AD. |\n| Compliance:    | As specified in the Requirement Document with a revised effective date of21 October 2010.                                                                                                                                                                                                                                                                                                                                                                                                                            |\n|                | This Airworthiness Directive becomes effective on 21 October 2010.                                                                                                                                                                                                                                                                                                                                                                                                                                                   |\n| Background:    | Reports have been received that thirteen 2nd stage High Pressure Turbine (HPT) air seal assemblies have been found cracked in the rim area. The actions specified in this AD are intended to prevent fracture of the 2nd stage HPT air seal assembly that could result in an uncontained engine failure.                                                                                                                                                                                                             |\n\n![](image.001.png)\n\nCharles Lenarcic  \nDelegate of the Civil Aviation Safety Authority\n\n22 September 2010","sortOrder":0},{"sectionNumber":"AD/PW4000/21","sectionType":"part","heading":"AD/PW4000/21","content":"## AD/PW4000/21","sortOrder":1},{"sectionNumber":"2nd","sectionType":"part","heading":"Stage High Pressure TurbineAir Seal Assembly","content":"## 2nd Stage High Pressure Turbine  \nAir Seal Assembly","sortOrder":2},{"sectionNumber":"20/2010","sectionType":"part","heading":"20/2010","content":"## 20/2010","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific mechanical defect in a specific engine component. It does not expand beyond the original safety purpose of preventing HPT air seal assembly fractures."},"complexity_factors":["Short, single-purpose directive (approximately 200 words of substantive content)","Only 1 defined term implicitly referenced (FAA AD 2001-20-02)","Simple conditional structure: 'Unless previously accomplished' is the only exception","Heavy reliance on external documents — the actual technical requirements are contained in FAA AD 2001-20-02 and Pratt & Whitney service bulletin, not reproduced here","No nested exceptions or complex cross-referencing within the document itself","Clear, linear compliance structure with single effective date"],"plain_english_summary":"This AD requires operators of Pratt & Whitney PW4000 engines to inspect and, if necessary, repair or replace the 2nd‑stage high‑pressure turbine air seal assembly after cracked rims were found. It mandates compliance with FAA AD 2001‑20‑02 (and later approved Pratt & Whitney service bulletins) to prevent uncontained engine failure. The directive has applied since 21 October 2010."},"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":3,"scope_assessment":{"changed":false,"description":"This AD adopts the FAA AD's technical requirements for the same PW4000 models and accepts a specified PW service bulletin revision as an AMOC. The instrument does not broaden or narrow the FAA AD's technical scope; the main regulatory change is specifying the Australian effective date (21 October 2010) and making the FAA-prescribed measures mandatory for Australian operators."},"complexity_factors":["Cross-reference to an external FAA AD (FAA AD 2001-20-02): compliance depends on following another jurisdiction's instrument (Requirement / Applicability).","Recurring inspection and corrective-action schedule: ongoing operational burden for engine operators (Requirement).","Acceptance of an alternate method of compliance (AMOC) via PW ASB PW4G-112-A72-233 Rev 3 — requires monitoring and approval of service-bulletin revisions (Requirement).","Applicability limited to PW4000 models identified in the FAA AD — requires operators to verify model coverage against FAA text (Applicability).","Specified Australian effective date (21 October 2010) ties compliance timing to a discrete regulatory milestone (Compliance).","Safety risk context: reports of thirteen cracked assemblies motivate mandatory action and create urgency (Background)."],"plain_english_summary":"This Airworthiness Directive requires operators of specified Pratt & Whitney PW4000 engines to perform the inspections and repeat actions set out in FAA AD 2001-20-02 to detect and repair cracked 2nd‑stage high‑pressure turbine air seal assemblies. CASA accepts a later Pratt & Whitney service bulletin revision as an alternate method of compliance and set the directive effective 21 October 2010. Engine operators bear compliance costs and must follow the FAA-prescribed inspection schedule to reduce the risk of uncontained engine failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pw4000-21-2nd-stage-high-pressure-turbine-air-seal-assembly","history":"/api/acts/ad-pw4000-21-2nd-stage-high-pressure-turbine-air-seal-assembly/history","analysis":"/api/acts/ad-pw4000-21-2nd-stage-high-pressure-turbine-air-seal-assembly/analysis","conflicts":"/api/acts/ad-pw4000-21-2nd-stage-high-pressure-turbine-air-seal-assembly/conflicts","importantCases":"/api/acts/ad-pw4000-21-2nd-stage-high-pressure-turbine-air-seal-assembly/important-cases","documents":"/api/acts/ad-pw4000-21-2nd-stage-high-pressure-turbine-air-seal-assembly/documents"}}