{"id":"F2006B06394","name":"AD/PW4000/2 - 2nd Stage HPT Rotating Airseal","slug":"ad-pw4000-2-2nd-stage-hpt-rotating-airseal","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":47703,"registerId":"commonwealth-F2006B06394-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PW4000/2 - 2nd Stage HPT Rotating 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)  \nPratt and Whitney Turbine Engines \\- PW4000 Series\n\nAD/PW4000/2 2nd Stage HPT Rotating Airseal 1/99\n\nApplicability: PW4000 series engines.\n\nRequirement: 1. Inspect 2nd stage high pressure turbine rotating airseals in accordance with Pratt and Whitney Alert Service Bulletins, PW4ENG A72-628, Rev. 1, and PW4G-100- A72-80, Rev. 1, as applicable.\n\n2. Modify 2nd stage ring segments and vane clusters, and install improved 2nd stage high pressure turbine rotating seals in accordance with Pratt and Whitney Service Bulletins PW4ENG 72-636, PW4ENG 72-637, PW4G-10- 72-93, and PW4G-100- 72-94, as applicable.\n\nIncorporation of these modifications and installation of an improved 2nd stage HPT rotating airseal constitutes terminating action for Requirement 1 of this Directive.\n\nNote: FAA AD 98-19-03 also refers.\n\nCompliance: 1. At each occasion the HPT is disassembled after the effective date of this Directive.\n\n2. Within 6 years after the effective date of this Directive.\n\nThis Airworthiness Directive becomes effective on 28 January 1999.\n\nBackground: This Directive is prompted by reports of 2nd stage HPT rotating airseal cracking which could result in an uncontained engine failure and damage to an aircraft.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, original safety directive addressing a specific mechanical defect in a specific engine series. It has not expanded beyond its original purpose of addressing 2nd stage HPT rotating airseal cracking."},"complexity_factors":["Short, single-purpose directive (approximately 200 words)","Only 4 defined technical references (the Pratt & Whitney Service Bulletins)","Simple two-part structure: inspection requirement + modification requirement with terminating action","Clear applicability statement (PW4000 series engines only)","Two straightforward compliance deadlines (recurring inspection + 6-year hard deadline)","No nested exceptions or conditional logic — requirements apply to all affected engines","Single cross-reference to related FAA directive for context","Technical terminology is aircraft-specific but clearly defined (HPT = High Pressure Turbine, airseal function explained in background)"],"plain_english_summary":"CASA requires inspections and a mandated upgrade for Pratt & Whitney PW4000 engines after cracks were found in the 2nd‑stage high‑pressure turbine rotating airseal. The aim is to prevent uncontained engine failure that could damage aircraft and endanger occupants.\n\nOperators and maintenance organisations must inspect the seal at HPT teardown and complete seal and related‑part modifications within six years; once modified, recurring inspections are no longer required. This aligns with the FAA’s earlier action."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive keeps a narrow scope: it targets PW4000 series engines and the 2nd‑stage HPT rotating airseal, mandating inspections and a specific hardware modification within set timeframes. It does not broaden to other engine types or unrelated components."},"complexity_factors":["Technical specificity: requires part‑level inspection and hardware modification of the 2nd‑stage HPT rotating airseal (source: Requirement 1–2).","Multiple referenced documents: several Pratt & Whitney Alert and Service Bulletins are mandatory, increasing coordination (Requirement; Applicability).","Conditional compliance triggers: inspection is required at each HPT disassembly, and modification must occur within six years — two different compliance paths (Compliance 1–2).","Terminating action: completing the modification ends the ongoing inspection obligation, creating a one‑time upgrade choice vs recurring inspections (Requirement 2).","Operational impact: maintenance planning and parts/repair availability affect operators’ costs and aircraft downtime (Compliance; Background).","Regulatory cross‑reference: FAA AD referenced, implying harmonisation with overseas regulator (Note)."],"plain_english_summary":"Requires operators of Pratt & Whitney PW4000 engines to inspect the 2nd‑stage high‑pressure turbine (HPT) rotating airseal using specified Pratt & Whitney service bulletins, and to modify ring segments/vane clusters and fit improved rotating seals. Inspections must occur whenever the HPT is disassembled and the mod must be completed within six years; the mod ends the inspection requirement. The directive is prompted by reported airseal cracking that could cause uncontained engine failure. Costs and scheduling fall to engine operators, who must follow the referenced service bulletins."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pw4000-2-2nd-stage-hpt-rotating-airseal","history":"/api/acts/ad-pw4000-2-2nd-stage-hpt-rotating-airseal/history","analysis":"/api/acts/ad-pw4000-2-2nd-stage-hpt-rotating-airseal/analysis","conflicts":"/api/acts/ad-pw4000-2-2nd-stage-hpt-rotating-airseal/conflicts","importantCases":"/api/acts/ad-pw4000-2-2nd-stage-hpt-rotating-airseal/important-cases","documents":"/api/acts/ad-pw4000-2-2nd-stage-hpt-rotating-airseal/documents"}}