{"id":"F2006B02282","name":"AD/AL 250/71 - Turbine Splined Adapter Locknut Torque","slug":"ad-al-250-71-turbine-splined-adapter-locknut-torque","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41512,"registerId":"commonwealth-F2006B02282-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AL 250/71 - Turbine Splined Adapter Locknut Torque","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 250/71 Turbine Splined Adapter Locknut Torque 12/86 TX\n\nApplicability: Model 250-C28 and \\-C30 series and turbines with serial numbers CAT 70001 through 70802 and 70804: CAT 28001 through 28046: and CAT 90001 through 95436 and 95438, and those turbines which have not been assembled or had turbine splined adapter locknut torque checked in accordance with: CEB-A-72-2132/3146; THO- 2639W-RFR-85 dated 7 February 1985; C28 Overhaul Manual Temporary Revision 72-7 dated 22 January 1986; C30 Overhaul Manual Revision 1 dated 1 July 1985, or\n\nCSL-2071/3073 dated 1 June 1985.\n\nRequirement: Inspect the gas generator turbine splined adapter locknut torque in accordance with Allison CEB-A-72-2132/3146 dated 1 October 1985 or approved equivalent.\n\nFAA Emergency Priority Letter AD 86-20-13 refers.\n\nCompliance: Unless already accomplished, within 5 hours’ time in service after 27 October 1986 but not later than 31 October 1986.\n\nBackground: Allison CSL-A-2084/3087 dated 10 September 1986 advises a recent contained C30 turbine wheel failure. Excessive wear and/or fretting of the splined connection between turbine splined adapter and turbine to compressor shaft can result from insufficient torque on the splined adapter locknut. This can lead to disconnect, overspeed and failure of the gas generator turbine. This Directive is issued to prevent excessive wear and/or fretting occurring due to improper torque of the splined adapter locknut.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in specific engine models. It has not expanded beyond its original purpose of preventing turbine adapter locknut failures."},"complexity_factors":["Single, specific technical requirement with clear compliance deadline","Limited applicability criteria using serial number ranges (6 distinct ranges plus exclusions)","References to 5 external technical documents (service bulletins, overhaul manual revisions)","Cross-reference to US FAA Emergency AD 86-20-13","No defined terms section or interpretation clauses","Straightforward conditional logic: 'Unless already accomplished' exemption"],"plain_english_summary":"This CASA Airworthiness Directive mandatorily requires inspection and correct torquing of the turbine splined-adapter locknut on specified Allison 250‑C28/C30 engines to prevent fretting, turbine separation, overspeed and catastrophic engine failure. It affects owners/operators of engines in the listed serial ranges and excludes engines already inspected or assembled per the approved procedures.\n\nCompliance is urgent and legally required within the short time limits specified."},"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":3,"scope_assessment":{"changed":false,"description":"The directive enforces a one‑off inspection/verification on the specified engines and serial numbers as described in the source (Applicability/Requirement/Compliance). It does not expand to other models or create ongoing certification changes beyond requiring the torque check per the referenced manufacturer documents, so scope remains aligned with the stated safety intent."},"complexity_factors":["Narrow technical applicability: specific models and long lists of serial numbers increases administrative checking burden for operators.","Reliance on external technical documents (Allison CEB-A-72-2132/3146 and overhaul manual revisions) requires access to and compliance with manufacturer procedures.","Very short compliance window (within 5 hours' time in service after 27 Oct 1986, not later than 31 Oct 1986) creates operational disruption and logistical pressure.","Requirement allows 'approved equivalent' procedure, introducing regulatory discretion and potential approval delay.","Technical nature of the task (torque inspection/adjustment of splined adapter locknut) requires qualified maintenance personnel and workshop resources.","Cross-reference to FAA Emergency Priority Letter AD increases coordination and duplicate compliance checks for international operators."],"plain_english_summary":"This airworthiness directive requires operators of specified Allison 250-C28 and 250-C30 series turbines (listed by serial number) to inspect the gas‑generator turbine splined‑adapter locknut torque using Allison CEB‑A‑72‑2132/3146 or an approved equivalent (Requirement/Compliance). CASA issued the directive; affected operators and maintenance providers must do the check within the short, specified window. The stated reason is to prevent fretting/wear from insufficient torque that can cause disconnect, overspeed and turbine failure. Costs (inspection, re‑torque, downtime) fall to operators; approval discretion exists for equivalent procedures."}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-71-turbine-splined-adapter-locknut-torque","history":"/api/acts/ad-al-250-71-turbine-splined-adapter-locknut-torque/history","analysis":"/api/acts/ad-al-250-71-turbine-splined-adapter-locknut-torque/analysis","conflicts":"/api/acts/ad-al-250-71-turbine-splined-adapter-locknut-torque/conflicts","importantCases":"/api/acts/ad-al-250-71-turbine-splined-adapter-locknut-torque/important-cases","documents":"/api/acts/ad-al-250-71-turbine-splined-adapter-locknut-torque/documents"}}