{"id":"F2006B08518","name":"AD/CFM56/13 - Accessory Gear Box - Starter Gear Replacement","slug":"ad-cfm56-13-accessory-gear-box-starter-gear-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":51257,"registerId":"commonwealth-F2006B08518-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CFM56/13 - Accessory Gear Box - Starter Gear 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/CFM56/13 Accessory Gear Box \\- Starter Gear Replacement\n\n  \n10/98\n\nDM\n\nApplicability: CFM International (CFMI) CFM56-3, \\-3B and \\-3C model turbofan engines identified and listed in Table 1 of CFMI Service Bulletin 72-877 Revision 1 and installed on Boeing 737 and other aeroplanes.\n\nRequirement: Replace the starter gear (line 5) in the accessory gearbox (AGB) of applicable engines in accordance with CFMI Service Bulletin 72-877 Rev 1.\n\nNote: DGAC 98-198(B)R1 dated 01 July 1998 refer.\n\nCompliance: 1. For aircraft with two applicable engines fitted, perform above requirement on one engine before 1 October 1998.\n\n2. For aircraft which have only one applicable engine, perform above action before 1 February 1999.\n\nThis airworthiness directive becomes effective on 29 July 1998.\n\nBackground: Two in flight shut downs were experienced due to a failure of the starter gear (line5) in the AGB.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"Scope aligns with the directive's stated purpose: it only requires replacement of the starter gear in the accessory gearbox for the specified CFM56-3 family engines identified by the service bulletin and sets deadlines by engine configuration (Applicability; Requirement; Compliance). There is no expansion beyond that replacement task or addition of unrelated obligations."},"complexity_factors":["Safety-critical mechanical action required due to prior in-flight shutdowns (Background).","Limited applicability to specific engine models and engines listed in CFMI Service Bulletin 72-877 Rev 1 (Applicability; Requirement).","Mandate depends on an external manufacturer service bulletin for the technical procedure (Requirement).","Staged compliance deadlines differ for aircraft with one versus two affected engines, creating scheduling complexity (Compliance 1–2).","Operational and logistical burden on operators/maintenance organisations to obtain parts and perform the replacement before deadlines (Compliance; Effective date).","Regulatory force: AD is mandatory from an effective date, so non-compliance carries safety and certification risks (Effective date; Compliance)."],"plain_english_summary":"This airworthiness directive requires replacement of the starter gear (line 5) in the accessory gearbox of specified CFMI CFM56-3, -3B and -3C engines, following CFMI Service Bulletin 72-877 Revision 1. It affects operators of Boeing 737 and other aeroplanes fitted with those engines, who must schedule the work by the directive's staged compliance dates to reduce the risk of in‑flight engine shutdowns."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive addressing a specific mechanical defect. It has not expanded beyond its original purpose of mandating replacement of a known faulty component."},"complexity_factors":["Very short document (approximately 200 words)","Only 2 defined terms (AGB/accessory gearbox, line 5 starter gear)","No cross-references to other legislation beyond a single note referencing a French aviation authority document (DGAC 98-198(B)R1)","Simple conditional structure: two compliance scenarios based on engine count","Single technical requirement with clear reference to manufacturer service bulletin","No nested exceptions or complex definitional sections"],"plain_english_summary":"This is a **safety order** (called an \"Airworthiness Directive\") issued by Australia's aviation safety regulator. It requires airlines and aircraft operators to replace a specific faulty part in certain jet engines.\n\n**What it does:**\n- **Targets:** CFM56-3 series jet engines (commonly used on Boeing 737 aircraft)\n- **The problem:** The starter gear in the engine's accessory gearbox has been failing in flight, causing two engines to shut down mid-flight\n- **The fix:** Replace the faulty starter gear following the manufacturer's instructions (Service Bulletin 72-877)\n\n**Who must comply:**\n- Airlines or operators with Boeing 737s or other aircraft using these specific engines\n- Different deadlines apply depending on how many affected engines are on the aircraft:\n  - **Two affected engines:** Fix one engine by 1 October 1998\n  - **One affected engine:** Fix it by 1 February 1999\n\n**Why it matters:**\nIn-flight engine shutdowns are serious safety risks. This directive forces operators to fix a known defect before it causes more incidents."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cfm56-13-accessory-gear-box-starter-gear-replacement","history":"/api/acts/ad-cfm56-13-accessory-gear-box-starter-gear-replacement/history","analysis":"/api/acts/ad-cfm56-13-accessory-gear-box-starter-gear-replacement/analysis","conflicts":"/api/acts/ad-cfm56-13-accessory-gear-box-starter-gear-replacement/conflicts","importantCases":"/api/acts/ad-cfm56-13-accessory-gear-box-starter-gear-replacement/important-cases","documents":"/api/acts/ad-cfm56-13-accessory-gear-box-starter-gear-replacement/documents"}}