{"id":"F2006B02274","name":"AD/AL 250/63 Amdt 7 - Turbine to Compressor Coupling Shaft Inspection and Modifications to Prevent Failure","slug":"ad-al-250-63-amdt-7-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":41504,"registerId":"commonwealth-F2006B02274-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AL 250/63 Amdt 7 - 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 250/63\n\nAmdt 7\n\n  \n\nTurbine to Compressor Coupling Shaft Inspection and Modifications to Prevent Failure\n\n  \n3/86\n\nApplicability: Model 250-C30 and -C30S engines installed in Sikorsky S-76 helicopters and Model 250-C30, -C30P, -C30R and - C30S engines installed in helicopters other than Sikorsky S-76, whose engine and turbine S/N are listed in the Requirement Document excepting those engines which incorporate all of the following CEBs:- CEB-A-72- 3134 Rev. 2 or CEB-A-72-3135 Rev.1: CEB-72-3100 Rev.1: CEB-72-3059 Rev. 4 and CEB-72-3096 Rev. 1.\n\nRequirement: F.A.A. A.D. 84-24-54 R.2 Amendment 39-5163 as amended by 39-5192.\n\nNote: Allison CEB-A-72-3134 Rev. 2\\. CEB-A-72-3135 Rev. 1.\n\nCEB-72-3100 Rev. 1.\n\nCEB-72-3059 Rev. 4.\n\nCEB-A-72-3108 Rev. 3\\. CEB-72-3096 Rev.1.\n\nand CEB-A-72-3143 refer.\n\nCompliance: 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 84-24-54 R.2 Amdt 39-5163 as amended by 39-5192 as the Requirement Document. The FAA AD includes additional C-30 model engines in the applicability for installations other than S-76 and, requires the mandatory introduction of turbine to compressor coupling shaft associated CEBs to prevent coupling shaft distress and the possibility of shaft disconnect which could result in an uncontained turbine failure.\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) until 30 Nov 1986 for S- 76 installations and 30 Nov 1987 for other helicopter installations.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":6,"scope_assessment":{"changed":true,"description":"The original directive (dating to 3/86) has expanded significantly through seven amendments. This version broadens applicability to include additional C-30 model engines in non-S-76 installations, converts previously optional CEBs into mandatory requirements, and imposes specific deadlines for replacing temporary shaft part numbers. The scope has shifted from a basic inspection requirement to a comprehensive retrofit program with phased compliance dates."},"complexity_factors":["Heavy cross-referencing to external FAA documents (AD 84-24-54 R.2, Amendment 39-5163, and Amendment 39-5192) without reproducing their content","Complex applicability clause with multiple nested conditions: specific engine models, specific aircraft types, specific serial numbers, AND a five-part exemption test requiring all CEBs to be present","Seven different CEB references with specific revision numbers (e.g., 'CEB-A-72-3134 Rev. 2 or CEB-A-72-3135 Rev.1') that must be cross-checked against engine records","Dual compliance deadlines (1986 for S-76, 1987 for other helicopters) with temporary part number restrictions","Technical aviation terminology requiring specialized knowledge (CEBs, part numbers, turbine/compressor coupling, uncontained failure)","Amendment structure — this is Amendment 7, indicating iterative changes that operators must track against previous versions"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of certain Allison 250‑C30 series turbine engines (notably on Sikorsky S‑76 and similar helicopters) to inspect and install mandatory coupling‑shaft modifications per the FAA AD. It makes previously optional manufacturer CEB upgrades compulsory (engines with all five CEBs are exempt) to prevent coupling‑shaft failure and uncontained turbine events."},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"This amendment broadened and tightened the original scope. Compared with the earlier Directive it: (1) explicitly adds additional C‑30 model engines for installations other than the Sikorsky S‑76 into the applicability (see \"Background\"), and (2) converts several turbine-to-compressor coupling shaft CEBs that were previously non‑mandatory into mandatory requirements (see \"Background\" and the Note on compliance). Both changes increase the number of engines/operators captured by the Directive and increase required corrective work beyond what earlier compliance may have covered."},"complexity_factors":["Cross-reference to an external document: FAA AD 84-24-54 R.2 (and amendments) is adopted as the Requirement Document","Multiple referenced Component Engineering Bulletins (CEBs) with specific revision numbers (at least 6 CEBs listed)","Conditional applicability by engine model and helicopter installation type (S‑76 versus other helicopters)","Serial-number-limited applicability (Requirement Document lists affected engine/turbine S/Ns)","Exception clause for engines that already incorporate all listed CEB revisions","Temporary allowance of alternative part numbers with different cutoff dates (two distinct deadlines)","Note that prior compliance may be insufficient if CEBs previously non-mandatory are now mandatory (requires rework)"],"plain_english_summary":"**What this directive does (mechanically)**\n\n- Requires inspection and, where needed, modification or replacement of the turbine-to-compressor coupling shaft on certain Allison Model 250-C30 series turbine engines installed in helicopters. (See \"Applicability\".)\n- Adopts and requires compliance with the FAA Airworthiness Directive 84-24-54 R.2 (and its amendments) as the technical Requirement Document for what inspections and modifications must be done. (See \"Requirement\".)\n- Makes several Allison Component Engineering Bulletins (CEBs) mandatory for the turbine‑to‑compressor coupling shaft work; these CEBs give the specific engineering changes and rework actions to prevent shaft distress and the possibility of shaft disconnect. (See the list of CEBs in the Directive.)\n- Temporarily permits the use of two older shaft part numbers (P/N 6896895 and 6889071) as interim alternatives until set cutoff dates (30 Nov 1986 for Sikorsky S‑76 installations; 30 Nov 1987 for other helicopter installations), after which the new shaft (P/N 23032345) or required modifications must be in place. (See final Note.)\n\n**Who is affected**\n\n- Owners and operators of helicopters with Allison Model 250-C30 and 250-C30S engines installed in Sikorsky S‑76 helicopters, and Model 250-C30, -C30P, -C30R and -C30S engines installed in other helicopters — but only the specific engine and turbine serial numbers listed in the Requirement Document, and excepting engines that already incorporate all the listed CEB revisions. (See \"Applicability\" and the CEB exception list.)\n\n**Why it matters (stated purpose and mechanical effect)**\n\n- The stated purpose (from the Directive and FAA AD it adopts) is to prevent coupling shaft distress and the risk of shaft disconnect. A shaft disconnect could result in an uncontained turbine failure. The mandated inspections and CEB change instructions are the mechanical measures intended to detect and fix or replace shafts that could fail. (See \"Background\" and the Requirement Document.)\n\n**Operational effects and immediate obligations**\n\n- Operators must follow the FAA AD and the referenced CEBs exactly as set out in the Requirement Document. \"Compliance\" is governed by that document; simply having complied with an earlier version of this Directive may not be enough if previously non‑mandatory CEBs are now mandatory — rework may be required. (See \"Compliance\" and the Note.)\n- Maintenance organisations will have to locate affected serial-numbered engines, schedule inspections, perform any mandated rework or part replacement, and manage aircraft downtime while compliance occurs.\n\n**Who pays and who decides**\n\n- The cost and operational impact fall on aircraft owners/operators and their maintenance providers: parts, labour, and helicopter downtime are borne by them. The Civil Aviation Safety Authority enforces the Directive; the FAA AD and the listed CEBs determine the technical details to be followed. (See \"Requirement\", \"CEBs\" and \"Compliance\".)\n\n**Costs, incentives and trade-offs**\n\n- Direct costs: inspections, parts (the new shaft P/N 23032345 or other parts required by the CEBs), downtime and maintenance labour. Those are concentrated on the affected operators.\n- Supply and scheduling risk: if many operators need the same replacement shaft or specialist rework, parts and maintenance capacity could be constrained, extending downtime.\n- Behavioural change: operators must prioritise compliance over other maintenance tasks; some may ground aircraft until work is done or use the permitted temporary shafts until the cutoff dates.\n- Benefit concentration: the principal immediate beneficiaries are users of the safety improvement (passengers, crew) and firms that supply the specified shafts or carry out the rework. The Directive creates a clear market for the specified parts and approved rework services.\n- Administrative and compliance burden: the Directive cross‑references an FAA AD and multiple CEBs; operators must ensure they have the correct CEB revisions and that earlier compliance does not leave outstanding mandatory changes.\n\n**Implementation risks and practical notes**\n\n- The effectiveness depends on correct identification of affected serial numbers in the Requirement Document and on operators following the specific CEB revisions now made mandatory. If records are incomplete or spare parts are scarce, risks to timely compliance increase.\n- The temporary allowance of two older shafts reduces immediate grounding pressure but imposes deadlines; failing to meet those deadlines requires replacement with the new P/N or completed modification.\n\n**Source claims vs. concrete trade‑offs**\n\n- The Directive claims the mandated inspections and CEB rework prevent shaft distress and possible uncontained turbine failure (see \"Background\"). Mechanically, this is achieved by making specific engineering changes mandatory and by prescribing inspections to detect distress. The trade‑offs are cost, downtime and reliance on parts/maintenance capacity; these are concrete and borne by operators (refer \"Compliance\", \"Note\").\n\n(References: Applicability; Requirement; Notes on CEBs and compliance; Background; final Note on temporary shaft P/Ns.)"},"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-al-250-63-amdt-7-turbine-to-compressor-coupling-shaft-inspection-and-modifications-to-prevent-fai","history":"/api/acts/ad-al-250-63-amdt-7-turbine-to-compressor-coupling-shaft-inspection-and-modifications-to-prevent-fai/history","analysis":"/api/acts/ad-al-250-63-amdt-7-turbine-to-compressor-coupling-shaft-inspection-and-modifications-to-prevent-fai/analysis","conflicts":"/api/acts/ad-al-250-63-amdt-7-turbine-to-compressor-coupling-shaft-inspection-and-modifications-to-prevent-fai/conflicts","importantCases":"/api/acts/ad-al-250-63-amdt-7-turbine-to-compressor-coupling-shaft-inspection-and-modifications-to-prevent-fai/important-cases","documents":"/api/acts/ad-al-250-63-amdt-7-turbine-to-compressor-coupling-shaft-inspection-and-modifications-to-prevent-fai/documents"}}