{"id":"F2006B08516","name":"AD/CFM56/11 - Accessory and Transfer Gearbox Replacement","slug":"ad-cfm56-11-accessory-and-transfer-gearbox-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":51251,"registerId":"commonwealth-F2006B08516-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CFM56/11 - Accessory and Transfer Gearbox 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)  \nCFM International Turbine Engines \\- CFM56 Series\n\nAD/CFM56/11 Accessory and Transfer Gearbox Replacement\n\n  \n6/98 TX\n\nApplicability: CFM International (CFMI) CFM 56-5, 56-5B and 56-5C, all models, turbofan engines with serial numbers as listed below (Warning: some engines may appear in more than one list):\n\nList 1A: (First batch of CFM56-5 Engines with suspect gearshaft cluster spur assembly 31x71 teeth (line 2) in the accessory gearbox (AGB). Engines Serial Number (ESN): 731951, 731954, 731955, 731959, 731960, 731962, 731963,\n\n731966, 731969 (See Service Bulletin CFM56-5 S/B 72-523 Revision 1).\n\nList 1B: (Second batch of CFM56-5 engines with suspect gearshaft cluster spur assembly 31x71 teeth (line 2) in the accessory gearbox (AGB). ESN 731943 to 731948, 731952, 731953, 731956 to 731958, 731973. (See Service Bulletin CFM56-5\n\nS/B 72-523 Revision 1).\n\nList 2A: (First batch of CFM56-5B Engines with suspect gearshaft cluster spur assembly 31x71 teeth (line 2) in the accessory gearbox (AGB). ESN: 779316, 779318, 779322, 779323, 779330, 779332, 779339 (See Service Bulletin CFM56-5B\n\nS/B 72-211 Revision 1).\n\nList 2B: (Second batch of CFM56-5B Engines with suspect gearshaft cluster spur assembly 31x71 teeth (line 2) in the accessory gearbox(AGB). ESN 779307 to 779315, 779317, 779327 (See Service Bulletin CFM56-5B S/B 72-211 Revision 1).\n\nList 3A: (First batch of CFM56-5C engines with suspect gearshaft cluster spur assembly 31x71 teeth (line 2) in the accessory gearbox (AGB) ESN: 741666, 741668, 741670 to 741674, 741676, 741677, 741680, 741682, 741684 (see Service\n\nBulletin CFM56-5C S/B 72-350 Revision 1).\n\nList 3B: (Second batch of CFM56-5C engines with suspect gearshaft cluster spur assembly 31x71 teeth (line 2) in the accessory gearbox (AGB). ESN: 741653, 741655, 741665, 741667, 741669, 741675, 741678, 741679, 741681 (see Service\n\nBulletin CFM56-5C S/B 72-350 Revision 1).\n\nRequirement: 1. For all engines in Lists 1A and 1B above, remove from service the gearshaft cluster spur assembly (31x71 teeth) in the AGB in accordance with the instructions of Service Bulletin CFM56-5 S/B 72-523 Revision 1.\n\n    2. For all engines in Lists 2A and 2B above, remove from service the gearshaft cluster spur assembly (31x 71 teeth) in the AGB in accordance with the instructions of Service Bulletin CFM56-5B S/B 72-211 Revision 1.\n\n    3. For all engines in Lists 3A and 3B above, remove from service the gearshaft cluster spur assembly (31x 71 teeth) in the AGB in accordance with the instructions of Service Bulletin CFM56-5C S/B 72-350 Revision 1.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n    4. For twin engined aircraft, with both engines applicable, all suspect gearshafts on one of the engines must be replaced in accordance with actions 1-2 above.\n\n    5. For four engined aircraft which have more than one engine applicable to the provisions of this directive, replace all suspect gearshafts, on all applicable engines (in accordance with actions 2-7 above), such that no more than one applicable engine with suspect gearshafts remains in service on any four engined aircraft.\n\nNote 1: Actions listed above which have already been completed under AD/CFM- 56/8 need not be repeated under this directive.\n\nNote 2: DGAC T98-097 (B) dated 25 February 1998 refers.\n\nCompliance: 1. Before 01 February 1998.\n\n    2. Engines on List 2A before 01 February 1998; engines on List 2B before 15 April 1998.\n\n    3. Engines on List 3A before 01 February 1998; engines on List 3B before 15 April 1998.\n\n    4. Before next flight.\n\n    5. Before next flight.\n\nThis airworthiness directive becomes effective on 26 March 1998.\n\nBackground: Three in flight shut downs were experienced due to failure of starter gearshafts in the accessory gearbox (AGB). The first analysis results shows also a risk of failure of the conical gearshafts of the transfer gearbox (TGB) which could lead to an in flight shut down. This directive supersedes the CFM56-5 requirements of AD/CFM-56/8 which has been cancelled.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"This directive expands and refines the earlier AD’s scope. The Background notes that it supersedes AD/CFM‑56/8; it continues and broadens corrective action by explicitly addressing not only starter gearshaft failures in the accessory gearbox (AGB) but also a reported risk to conical gearshafts in the transfer gearbox (TGB). The current text specifies multiple engine‑serial number lists across three engine sub‑types, ties each sub‑type to a distinct Service Bulletin, and adds specific operational constraints for twin‑ and four‑engined aircraft (Requirements 4–5). Those additions extend the original corrective focus into a wider set of engines, more prescriptive repair procedures, and stricter interim operational limits compared with a narrower original intent."},"complexity_factors":["Six separate engine lists (Lists 1A, 1B, 2A, 2B, 3A, 3B) specifying serial numbers","Different service bulletins tied to each engine sub‑type (CFM56‑5 S/B 72‑523 Rev 1; CFM56‑5B S/B 72‑211 Rev 1; CFM56‑5C S/B 72‑350 Rev 1)","Multiple staggered compliance deadlines (before 01 Feb 1998, before 15 Apr 1998, and 'before next flight')","Conditional rules for twin‑engined and four‑engined aircraft (Requirement 4–5) producing operational constraints","Cross‑reference to and supersession of a prior AD (AD/CFM‑56/8) and to foreign authority communication (DGAC T98‑097(B))","Warning that engines may appear in more than one list (adds reconciliation work for operators)"],"plain_english_summary":"**What this directive does (mechanical change)\n\n- Requires removal and replacement of a specific gearshaft cluster spur assembly (31x71 teeth) in the accessory gearbox (AGB) for certain CFM56-5, -5B and -5C turbofan engines. (See Requirement paragraphs 1–3.)\n- Requires additional limits for multi‑engine aircraft: on twin‑engine aircraft with both engines affected, all suspect gearshafts on one engine must be replaced before further flight; on four‑engine aircraft, replacements must be done so that at most one affected engine remains in service. (See Requirement paragraphs 4–5.)\n- Directs operators to follow the detailed repair/replacement procedures in the manufacturer’s Service Bulletins specified for each engine sub‑type. (See Requirement paragraphs 1–3 and the Service Bulletin references.)\n\nWho is affected\n\n- Aircraft operators and maintenance organisations that operate or service CFMI CFM56-5, CFM56-5B and CFM56-5C engines whose serial numbers appear in the six engine lists published in the directive (Lists 1A, 1B, 2A, 2B, 3A, 3B). The directive warns that some engines may be listed more than once.\n- Twin‑engined and four‑engined aircraft operators who have one or more affected engines installed, because of the specific “one‑engine” rules for continuing operations. (Requirement 4–5.)\n\nWhy it matters (stated purpose and operational effect)\n\n- Stated purpose: the directive responds to in‑flight shutdowns caused by starter gearshaft failures in the AGB and a risk of failure of conical gearshafts in the transfer gearbox (TGB). It supersedes and replaces earlier, related AD material. (Background.)\n- Operational effect: affected gearshafts must be removed from service and replaced according to the manufacturer’s instructions by the stated compliance dates (see Compliance). Until replacement is done, affected engines may be limited in use by the twin‑/four‑engine rules.\n\nKey deadlines and compliance mechanics\n\n- Engines on Lists 1A/1B: remove the suspect gearshaft before 01 February 1998. (Compliance 1.)\n- Engines on Lists 2A: before 01 February 1998; 2B: before 15 April 1998. (Compliance 2.)\n- Engines on Lists 3A: before 01 February 1998; 3B: before 15 April 1998. (Compliance 3.)\n- For twin‑engine aircraft with both engines applicable: replacement required before next flight. (Requirement 4 + Compliance 4.)\n- For four‑engine aircraft with more than one applicable engine: replace so that no more than one applicable engine with suspect gearshafts remains in service; action required before next flight. (Requirement 5 + Compliance 5.)\n\nOperational and economic consequences (mechanisms, incentives, trade‑offs)\n\n- Who pays: aircraft operators (or their insurers) pay for the replacement parts, maintenance labour and any aircraft downtime or schedule disruption caused by the work. The AD mandates use of manufacturer service bulletins, which fixes the technical standard for the work (Requirement 1–3).\n- Who decides: the Civil Aviation Safety Authority (CASA) issued the AD; operators decide scheduling and which maintenance provider performs the work, subject to following the referenced Service Bulletins. Maintenance organisations must certify the work per normal regulatory practice.\n- Direct costs and opportunity costs: parts availability and shop capacity determine how quickly work can be done. Operators face direct expenditure on parts and labour and indirect costs from aircraft ground time and potential schedule impacts.\n- Effects on competition and independent MROs: because the AD requires compliance with particular manufacturer service bulletins (Requirement 1–3), independent maintenance providers can perform the work only if they have the capability and documentation to apply the specified procedures. If replacement parts are limited or routed preferentially to OEM‑linked shops, that can constrain independent MROs and create concentrated demand for certain suppliers.\n- Behavioural change: operators must inspect fleet serial numbers against the six lists, ground or limit operation of affected engines per the twin/four‑engine rules until replacement is done, and schedule replacements to meet staggered deadlines (Compliance section). Some operators may prioritize replacements to keep aircraft in service.\n- Compliance risk and implementation trade‑offs: tight deadlines (some \"before next flight\" requirements for multi‑engine cases) can force short‑notice removals and create schedule disruption. Availability of replacement gearshafts and qualified labour is a practical risk to meeting the AD on time.\n\nOther technical/legal notes\n\n- The directive explicitly states that actions already completed under the earlier AD/CFM‑56/8 need not be repeated. (Note 1.)\n- The AD references French DGAC communication T98‑097(B) as related material. (Note 2.)\n\nPlain‑language takeaways\n\n- If you operate aircraft with the specified CFM56‑5 family engines, check the engine serial numbers in this AD against your records immediately.\n- If your engine is listed, you must remove and replace the specified gearshaft assembly according to the manufacturer’s service bulletin by the deadline stated for that list, and you may be limited from flying until the work is done in some multi‑engine configurations.\n- Expect direct repair costs, scheduling and parts availability to be the main operational burdens; the regulator sets the technical standard and deadlines, and operators and maintenance organisations must execute the work (Requirement 1–5; Compliance; Service Bulletin references)."},"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":3,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific mechanical defect in specific engine serial numbers. It supersedes a prior directive (AD/CFM-56/8) but only for the CFM56-5 series, suggesting refinement rather than expansion. The multi-engine aircraft provisions (actions 4-5) are standard risk-mitigation measures for this type of safety issue, not scope creep."},"complexity_factors":["Multiple enumerated lists (6 separate lists) with specific serial numbers requiring cross-referencing against engine logs","Different compliance deadlines for different engine batches (1 Feb 1998 vs 15 April 1998)","Conditional logic based on aircraft configuration (twin-engine vs four-engine requirements differ significantly)","Reference to external technical documents (Service Bulletins) for actual replacement procedures — the AD mandates action but doesn't contain the instructions","Nested applicability: must check engine model, then serial number, then aircraft type to determine exact compliance action","Supersedes previous directive (AD/CFM-56/8) with partial overlap (Note 1 allows credit for prior work)"],"plain_english_summary":"This CASA Airworthiness Directive orders immediate replacement of a faulty 31x71-teeth gearshaft in the accessory gearbox of specified CFM56-5/5B/5C engines (engines listed in six serial-number batches). It affects operators of A320-family aircraft fitted with those engines and required near‑term, often “before next flight,” replacements to prevent in‑flight shutdowns. The AD is an urgent safety action after multiple engines shut down in flight."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cfm56-11-accessory-and-transfer-gearbox-replacement","history":"/api/acts/ad-cfm56-11-accessory-and-transfer-gearbox-replacement/history","analysis":"/api/acts/ad-cfm56-11-accessory-and-transfer-gearbox-replacement/analysis","conflicts":"/api/acts/ad-cfm56-11-accessory-and-transfer-gearbox-replacement/conflicts","importantCases":"/api/acts/ad-cfm56-11-accessory-and-transfer-gearbox-replacement/important-cases","documents":"/api/acts/ad-cfm56-11-accessory-and-transfer-gearbox-replacement/documents"}}