{"id":"F2006B02252","name":"AD/AL 250/38 - Idler Gearshafts - Replacement","slug":"ad-al-250-38-idler-gearshafts-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41482,"registerId":"commonwealth-F2006B02252-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AL 250/38 - Idler Gearshafts - 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)  \nAllison Turbine Engines \\- 250 Series\n\nAD/AL 250/38 Idler Gearshafts \\- Replacement 10/79\n\nApplicability: All 250-C28 and \\-C30 series models fitted with generator idler gearshaft P/N 6898980 or 6898591 and 77 tooth idler gearshaft P/N 6898652.\n\n| Document:   | 1.  | Allison 250-C28 CEB No. 72-2003; or Allison 250-C30 CEB No. 72-3003; or                                                                                       |\n| ----------- | --- | ------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n|             | 2.  | FAA AD 79-16-06 Amendment 39-3527 also refers.                                                                                                                |\n| Compliance: | 1.  | For 250-C28 engines: Prior to reaching 9000 cycles.                                                                                                           |\n|             | 2.  | For 250-C30 engines: Prior to reaching 2000 cycles.                                                                                                           |\n|             | 3.  | For engines which may have exceeded the maximum permissible number of cycle at the time of promulgation of this Directive 3 September 1979, within 50 cycles. |\n\nBackground: This Directive is issued to prevent sudden power loss due to accessory drive gearbox gearshaft failure.","sortOrder":0}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused on a specific mechanical failure mode in specific engine models. It has not expanded beyond its original purpose of preventing gearshaft failure through mandatory replacement."},"complexity_factors":["Very short document (under 300 words)","Only 3 defined part numbers in applicability section","Simple conditional structure: 3 compliance deadlines based on engine model and current cycle count","No cross-references to other legislation beyond citing source documents (FAA AD and manufacturer bulletins)","Single purpose: replacement of specific parts by specific deadlines","No nested exceptions or complex definitional sections"],"plain_english_summary":"This Airworthiness Directive requires owners/operators of aircraft with Allison 250-C28 or 250-C30 engines fitted with specific generator/77‑tooth idler gearshafts (P/N 6898980, 6898591, 6898652) to replace those parts before reaching cycle limits (C28: 9,000 cycles; C30: 2,000; engines already over the limits as of Sept 1979: within 50 cycles). It’s mandatory because these shafts can fail suddenly, causing complete power loss and grounding non‑compliant aircraft."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive targets replacement of specified idler gearshafts on specified engine models to prevent gearbox gearshaft failure and sets mandatory replacement deadlines. It does not broaden applicability beyond the listed models/part numbers but imposes time-bound replacement requirements (Applicability; Compliance; Background)."},"complexity_factors":["Narrow applicability to two engine models and three part numbers reduces breadth but requires part-level checks (Applicability).","Multiple and asymmetric compliance deadlines create scheduling complexity: 9,000 cycles (250-C28); 2,000 cycles (250-C30); within 50 cycles if already exceeded (Compliance: 1–3).","References to external technical/regulatory documents (Allison CEB Nos.; FAA AD 79-16-06) require operators to consult additional material for implementation details (Document).","Safety-critical nature (prevent sudden power loss from gearshaft failure) elevates enforcement and inspection priority, increasing operational impact and potential downtime (Background).","Immediate obligation for engines already beyond permitted cycles concentrates short-term cost and logistical burden on affected operators (Compliance: 3)."],"plain_english_summary":"This airworthiness directive requires operators of Allison 250-C28 and 250-C30 engines fitted with specific idler gearshafts (P/Ns 6898980, 6898591, 6898652) to replace those parts by set cycle limits to prevent accessory-drive gearbox gearshaft failure. Operators must schedule replacements by 9,000 cycles for 250-C28, 2,000 cycles for 250-C30, or within 50 cycles if already over the limit, imposing defined maintenance, cost and scheduling obligations."}},"importantCases":[],"_links":{"self":"/api/acts/ad-al-250-38-idler-gearshafts-replacement","history":"/api/acts/ad-al-250-38-idler-gearshafts-replacement/history","analysis":"/api/acts/ad-al-250-38-idler-gearshafts-replacement/analysis","conflicts":"/api/acts/ad-al-250-38-idler-gearshafts-replacement/conflicts","importantCases":"/api/acts/ad-al-250-38-idler-gearshafts-replacement/important-cases","documents":"/api/acts/ad-al-250-38-idler-gearshafts-replacement/documents"}}