{"id":"F2006B02307","name":"AD/ALF/11 Amdt 1 - Third Stage Compressor Disc","slug":"ad-alf-11-amdt-1-third-stage-compressor-disc","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41537,"registerId":"commonwealth-F2006B02307-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ALF/11 Amdt 1 - Third Stage Compressor Disc","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)  \nAlliedSignal (Lycoming) Turbine Engines \\- ALF502 and LF507 Series\n\nAD/ALF/11\n\nAmdt 1\n\n  \nThird Stage Compressor Disc 8/91\n\nApplicability: All ALF502 engines fitted with third stage compressor disc part number 2-101-630- 04/-05.\n\nRequirement: Inspect third stage compressor discs part number 2-101-630-04/-05 for evidence of cracking and apply Sermetel W or ALSEAL 518 protective coating in accordance with;\n\n    (a) Model ALF502R series engines: Lycoming SB ALF502R 72-203 R2, or\n\n    (b) Model ALF502L series engines: Lycoming SB ALF502L 72-203 R2.\n\nNote: For ALF 502R series engines, FAA AD 90-24-01 refers. FAA AD 90-24-01 supersedes FAA AD T89-13-52.\n\nCompliance: As detailed in requirement documents.\n\nBackground: This Directive has been amended to include ALF502L series engines and to reflect a reduction in the inspection threshold. This amendment follows advice of cracking found in two discs at engine cycles below the 8,500 cycles since new inspection threshold detailed in FAA AD T89-13-52.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"The original directive (implied by the amendment note) only covered ALF502R series engines with an inspection threshold of 8,500 cycles. Amendment 1 expanded scope to include ALF502L series engines and lowered the inspection threshold based on new safety data showing cracks occurring below 8,500 cycles."},"complexity_factors":["Very short document (under 300 words)","Only 2 defined applicability criteria (engine model and part number)","Simple binary conditional structure (R-series vs L-series engines)","No nested exceptions or complex cross-referencing beyond pointing to external service bulletins","Single compliance requirement with clear alternative coating options","Background section provides clear rationale for amendment"],"plain_english_summary":"This AD requires operators of aircraft powered by AlliedSignal/Lycoming ALF502 engines with third-stage compressor discs P/N 2-101-630-04 or 2-101-630-05 to inspect those discs for cracks and apply a protective coating (Sermetel W or ALSEAL 518) per the referenced service bulletins. It was tightened after in-service cracks appeared earlier than expected, now covering additional L‑series engines and lowering the inspection threshold to reduce in‑flight failure risk."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Scope was expanded by the amendment to include ALF502L series engines and by reducing the inspection threshold after detection of cracking below the prior 8,500 cycle threshold (Background; Applicability; Requirement)."},"complexity_factors":["Narrow technical applicability: applies only to third stage compressor discs part number 2-101-630-04/-05 on ALF502 engines (Applicability).","Dependency on external documents: compliance requires following Lycoming Service Bulletins ALF502R 72-203 R2 or ALF502L 72-203 R2 (Requirement).","Cross-reference to foreign regulator actions: note refers to FAA ADs, creating reliance on non‑domestic regulatory history (Requirement/Note).","Changed inspection threshold: amendment lowers the cycles‑since‑new threshold because cracks were found below the prior 8,500-cycle benchmark (Background).","Operational/compliance burden: operators must perform inspections and apply protective coating per the service bulletins; costs and aircraft downtime borne by operators (Requirement/Compliance)."],"plain_english_summary":"Requires inspection and application of a protective coating to third-stage compressor discs (`2-101-630-04`/`-05`) on ALF502 engines, to be done in accordance with Lycoming service bulletins. The Civil Aviation Safety Authority’s directive affects operators of aircraft with these engine parts, who must carry out inspections and coatings and bear the associated costs. The amendment adds ALF502L engines and lowers the inspection threshold after cracking was found below the previous 8,500-cycle threshold."}},"importantCases":[],"_links":{"self":"/api/acts/ad-alf-11-amdt-1-third-stage-compressor-disc","history":"/api/acts/ad-alf-11-amdt-1-third-stage-compressor-disc/history","analysis":"/api/acts/ad-alf-11-amdt-1-third-stage-compressor-disc/analysis","conflicts":"/api/acts/ad-alf-11-amdt-1-third-stage-compressor-disc/conflicts","importantCases":"/api/acts/ad-alf-11-amdt-1-third-stage-compressor-disc/important-cases","documents":"/api/acts/ad-alf-11-amdt-1-third-stage-compressor-disc/documents"}}