{"id":"F2006B02279","name":"AD/AL 250/68 Amdt 2 - Turbine to Compressor Coupling Shaft Inspection and Modifications to Prevent Failure","slug":"ad-al-250-68-amdt-2-turbine-to-compressor-coupling-shaft-inspection-and-modifications-to-prevent-fai","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41509,"registerId":"commonwealth-F2006B02279-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AL 250/68 Amdt 2 - Turbine to Compressor Coupling Shaft Inspection and Modifications to Prevent Failure","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)  \nAllison Turbine Engines \\- 250 Series\n\nAD/AL 250/68\n\nAmdt 2\n\n  \n\nTurbine to Compressor Coupling Shaft Inspection and Modifications to Prevent Failure\n\n  \n3/86\n\nApplicability: For Part A:-All model 250-C28B, \\-C28C engines which incorporate turbine to compressor coupling shaft P/N 23008080 and;\n\nFor Part B:- All model 250-C28B, \\-C28C engines with engine and turbine serial numbers listed in the Requirement Document excepting those engine which incorporate ALL of the following CEBs:-\n\nCEB-A-72-2127 Rev 1, CEB-72-2101 Rev 1, CEB-72-2063 Rev 4, and CEB-72- 2099 Rev 1.\n\nRequirement: Part A:- FAA AD 85-25-12 Amdt 39-5191.\n\nNote: Turbine to compressor coupling shafts P/N 6896895 or 6889071 may be fitted temporarily as an alternative to new shaft P/N 23032345, in which case further rework in accordance with Part B of this Directive will be required.\n\nPart B:- FAA AD 85-25-09 Amdt 39-5190.\n\nNote: Allison CEB-A-72-2127 Rev 1\\. CEB-72-2101 Rev 1.\n\nCEB-72-2063 Rev 4.\n\nCEB-72-2099 Rev 1.\n\nand CEB-A-72-2122 refer.\n\nCompliance: Part A:- Within 100 hours’ time in service, or at the next turbine repair or inspection, whichever occurs first after 20 December 1985, but in any case no later than 6 March 1986.\n\nPart B:- As detailed in the Requirement Document.\n\nNote: Compliance with the previous issue of this Directive may not satisfy the mandatory introduction of some CEBs which were previously assessed as non- mandatory, hence, further rework may be necessary.\n\nBackground: This Directive is amended to reflect FAA AD 85-25-12 AMDT 39-5191 and AD 85- 25-09 AMDT 39-5190 as the Requirement Documents. These Directives require modifications to -C28B and -C28C series engines to prevent distress and the possibility of shaft disconnects which could result in an uncontained failure. C30 series engines which were previously nominated as “applicable” in this Directive are now reflected in AD/AL-250/63 Amdt 7 issued concurrent with this Directive.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nNote: This Directive limits the use of shafts P/N 6896895 and 6889071 as temporary alternatives (pending the change to new shaft P/N 23032345) for C28 series engines until 30 November 1987.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":true,"description":"This is Amendment 2 to an existing directive. The scope has been narrowed from the original version — the C30 series engines were removed from this directive and moved to a separate Airworthiness Directive (AD/AL-250/63 Amdt 7). Additionally, the amendment introduces stricter limitations on temporary alternative parts (shafts P/N 6896895 and 6889071) with a hard deadline of 30 November 1987, and clarifies that previous compliance may not be sufficient due to reclassification of certain CEBs from non-mandatory to mandatory."},"complexity_factors":["Multiple part numbers referenced (P/N 23008080, 23032345, 6896895, 6889071) requiring cross-checking against engine records","Dual-part structure (Part A and Part B) with different applicability criteria and compliance timelines","Five specific Customer Engineering Bulletin (CEB) references that must be verified to determine if Part B applies","Nested conditional logic: Part B applicability depends on engine serial numbers AND exclusion criteria based on which CEBs are already installed","External document incorporation by reference (FAA AD 85-25-12 and 85-25-09) — the full requirements aren't contained in this text","Temporal compliance calculations involving 'whichever occurs first' triggers (flight hours vs. calendar dates)","Amendment history context (previous issues, concurrent directives affecting C30 series engines now moved to separate AD)"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspection, replacement and modification of the turbine-to-compressor coupling shaft on Allison 250‑C28B and 250‑C28C engines to prevent shaft breakage and potential uncontained engine failure. It affects operators and maintenance organisations for aircraft using these engines, imposes strict deadlines (no extensions) for inspections and permanent upgrades, and is legally mandatory under the Civil Aviation Regulations."},"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":5,"scope_assessment":{"changed":true,"description":"The amendment aligns the Directive with the cited FAA ADs, clarifies and tightens requirements for C28B/C28C engines, removes C30 series from this Directive (moved to AD/AL-250/63 Amdt 7), and imposes limits on temporary shaft use (expiry 30 Nov 1987). It also introduces exceptions for engines incorporating specific CEB revisions and warns that earlier compliance may not meet the newly mandatory CEB rework, potentially expanding required work."},"complexity_factors":["Cross-references to multiple FAA Airworthiness Directives (AD 85-25-12 and AD 85-25-09) and several Allison CEBs, requiring readers to consult external documents for full technical detail","Split structure (Part A and Part B) with different applicability and compliance triggers","Conditional applicability and exclusions — engines listed in Requirement Document are treated differently and some engines are excepted if they incorporate specified CEBs","Temporary allowance of alternate shaft part numbers (P/N 6896895 or 6889071) contingent on later rework and a fixed expiry date (30 Nov 1987)","Mixed timing rules (within 100 hours’ time in service or at next repair, versus 'as detailed in Requirement Document'), increasing compliance planning complexity","Note that prior compliance may not satisfy newly mandatory CEBs, creating potential rework and record-review burdens"],"plain_english_summary":"This Directive requires inspections and modifications to the turbine-to-compressor coupling shaft on Allison 250‑C28B and 250‑C28C engines to prevent shaft distress or disconnects. It mandates operators and maintenance organisations to carry out the specified work within set service‑time limits or at the next turbine repair, allows two alternative temporary shaft part numbers pending replacement (with further rework required) and fixes a 30 November 1987 limit on those temporary parts. CASA enacts the work by adopting specified FAA ADs and Allison CEBs; operators pay for compliance and schedule the work."}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-68-amdt-2-turbine-to-compressor-coupling-shaft-inspection-and-modifications-to-prevent-fai","history":"/api/acts/ad-al-250-68-amdt-2-turbine-to-compressor-coupling-shaft-inspection-and-modifications-to-prevent-fai/history","analysis":"/api/acts/ad-al-250-68-amdt-2-turbine-to-compressor-coupling-shaft-inspection-and-modifications-to-prevent-fai/analysis","conflicts":"/api/acts/ad-al-250-68-amdt-2-turbine-to-compressor-coupling-shaft-inspection-and-modifications-to-prevent-fai/conflicts","importantCases":"/api/acts/ad-al-250-68-amdt-2-turbine-to-compressor-coupling-shaft-inspection-and-modifications-to-prevent-fai/important-cases","documents":"/api/acts/ad-al-250-68-amdt-2-turbine-to-compressor-coupling-shaft-inspection-and-modifications-to-prevent-fai/documents"}}