{"id":"F2006B10991","name":"AD/JT8D/37 - HP Compressor Disc Replacement","slug":"ad-jt8d-37-hp-compressor-disc-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56580,"registerId":"commonwealth-F2006B10991-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/JT8D/37 - HP Compressor Disc Replacement","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 \\- JT8D Series\n\nAD/JT8D/37 HP Compressor Disc Replacement 8/99\n\nApplicability: All JT8D-1 through \\-17R series engines incorporating a high pressure compressor disc listed by serial number in Appendix 1 of FAA AD 99-01-08.\n\nRequirement: Remove from service stage 7 through stage 14 high pressure compressor discs as specified by serial number in Appendix 1 of FAA AD 99-01-08.\n\nNote: A review carried out when this problem first became known showed that none of the affected discs were installed in engines fitted to Australian aircraft.\n\nCompliance: Unless previously accomplished, as detailed in FAA AD 99-01-08, Compliance (a).\n\nThis Airworthiness Directive becomes effective on 12 August 1999.\n\nBackground: This directive is prompted by advice of an uncontained HPC disc failure on a JT8D-9 engine. The investigation into this incident identified the disc failure was caused by cadmium embrittlement due to a process anomaly during nickel cadmium plating.\n\nNickel cadmium plating is used to provide corrosion protection for the disc.\n\nThe FAA has advised that several hundred high pressure compressor discs fitted to P&W JT3D and JT8D engines may have been incorrectly processed during nickel cadmium plating at a particular repair facility. Given the potential for further uncontained failures, replacement of the suspect discs has been made mandatory unless they have operated beyond an established safe threshold.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue safety directive addressing a specific manufacturing defect in specific engine components. It has not expanded beyond its original purpose of mandating replacement of suspect compressor discs."},"complexity_factors":["Very short document (under 300 words)","Only 1 substantive requirement (remove specific discs)","No defined terms section — relies entirely on external reference to FAA AD 99-01-08","Single condition: 'unless previously accomplished'","No nested exceptions or conditional logic","Straightforward applicability test (engine model + serial number list)"],"plain_english_summary":"This Airworthiness Directive orders removal of specific high‑pressure compressor discs from Pratt & Whitney JT8D‑series engines (discs listed by serial number in FAA AD 99‑01‑08) after an in‑service disc exploded from cadmium embrittlement caused by faulty plating at a repair facility, creating an uncontained‑failure hazard. It affects operators of JT8D‑1 through JT8D‑17R engines; Australian checks found none installed, but compliance was mandatory from 12 August 1999."},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":false,"description":"Scope remains a targeted safety recall: removal of specific HPC discs identified by serial number (see 'Applicability' and 'Requirement') per FAA AD. The directive does not broaden coverage beyond those listed discs, but preserves an exception for discs that have operated beyond an established safe threshold."},"complexity_factors":["Cross-reference to FAA AD 99‑01‑08 for the definitive serial‑number list and compliance steps (requires reliance on external instrument).","Serial‑number‑specific applicability requires parts traceability and record checks for each affected disc.","Technical safety determination (cadmium embrittlement) and the exception for discs that have operated beyond a specified safe threshold introduce engineering judgment and threshold calculation.","Multiple engine models covered (JT8D‑1 through ‑17R) increasing operator footprint.","Operational disruption and logistics of removing and replacing hundreds of discs (parts availability, downtime).","Effective date and mandatory compliance language create time‑bound enforcement pressure.","Investigation dependence on repair‑facility process failure (ni‑Cd plating anomaly) implicates supply‑chain scrutiny and potential follow‑up actions."],"plain_english_summary":"This directive requires operators to remove from service certain stage 7–14 high‑pressure compressor discs on Pratt & Whitney JT8D‑1 through ‑17R engines when the disc serial number appears in Appendix 1 of FAA AD 99‑01‑08. It took effect 12 August 1999. The action responds to an uncontained disc failure traced to cadmium embrittlement from a nickel‑cadmium plating process anomaly; operators must follow the FAA AD compliance schedule. Owners pay replacement and traceability costs; the regulator enforces removal unless a disc has already exceeded an established safe threshold."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-jt8d-37-hp-compressor-disc-replacement","history":"/api/acts/ad-jt8d-37-hp-compressor-disc-replacement/history","analysis":"/api/acts/ad-jt8d-37-hp-compressor-disc-replacement/analysis","conflicts":"/api/acts/ad-jt8d-37-hp-compressor-disc-replacement/conflicts","importantCases":"/api/acts/ad-jt8d-37-hp-compressor-disc-replacement/important-cases","documents":"/api/acts/ad-jt8d-37-hp-compressor-disc-replacement/documents"}}