{"id":"F2006B11228","name":"AD/M20/21 - Engine Mount - Inspection and Repair","slug":"ad-m20-21-engine-mount-inspection-and-repair","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56946,"registerId":"commonwealth-F2006B11228-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/M20/21 - Engine Mount - Inspection and Repair","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nMooney M20 Series Aeroplanes\n\nAD/M20/21 Engine Mount \\- Inspection and Repair 5/75\n\nApplicability: Model M20C with S/Nos. 1852, 1940 to 3466, 670001 to 700061, and 20-0001 to 20-\n\n1156; Model M20D S/Nos. 101 to 260; Model M20E S/Nos. 101 to 1308, 670001 to\n\n700061, 20-0001 to 21-1165; Model M20F S/Nos. 660003 to 700072, 22-0001 to 22-\n\n1207; Model M20G S/Nos. 680001 to 700006.\n\nDocument: Mooney SB No. M20-192.\n\nCompliance: 1. For engine mounts which have achieved 450 hours time in service - within 50 hours time in service after 19 May 1975 and there- after at intervals not exceeding 100 hours time in service until repaired or replaced as detailed in SB M20-192.\n\n2. For all other mounts \\- before achieving 450 hours time in service and thereafter at intervals not exceeding 100 hours time in service until repaired or replaced as detailed in the Service Bulletin.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD applies to the specified Mooney M20 models and serial-number ranges and prescribes inspection intervals and remedial action by reference to Service Bulletin M20-192. There is no indication in the text that the scope of affected aircraft or the nature of required inspections and repairs has been broadened beyond that original prescription."},"complexity_factors":["Multiple model and serial-number ranges listed in Applicability, requiring cross-check of airframe identity.","Two different inspection-start rules depending on whether a mount has reached 450 hours time in service (Compliance 1–2).","Recurring inspection interval specified (every 100 hours) creating an ongoing obligation (Compliance 1–2).","Required remedial actions are defined by an external document (Mooney SB No. M20-192) rather than fully in the AD (Document).","Historic date reference (within 50 hours after 19 May 1975) creates an archival/timing detail that may complicate interpretation for records."],"plain_english_summary":"What this instrument does, mechanically\n\n- It requires regular inspections and any necessary repairs or replacement of engine mounts on specified Mooney M20 aeroplane models and serial-number ranges. (Applicability; Compliance; Document: Mooney SB No. M20-192.)\n\nWho is affected\n\n- Owners and operators of the listed Mooney M20 models and serial-number ranges must carry out the inspections and do the repairs or replacements described in Service Bulletin M20-192. (Applicability; Document.)\n\nHow compliance works (the rules you must follow)\n\n- For engine mounts that already have 450 hours time in service: inspect within 50 hours after 19 May 1975 and then at intervals not exceeding 100 hours time in service until the mount is repaired or replaced as detailed in SB M20-192. (Compliance 1.)\n- For mounts with less than 450 hours time in service: inspect before they reach 450 hours and thereafter at intervals not exceeding 100 hours time in service until repaired or replaced as detailed in SB M20-192. (Compliance 2.)\n- The Service Bulletin M20-192 contains the repair/replacement procedures the AD requires you to follow. (Document.)\n\nWho decides and who pays\n\n- The Civil Aviation Safety Authority issued the directive under the Civil Aviation Regulations schedule of Airworthiness Directives; it prescribes mandatory inspection and repair timing. (Header: Civil Aviation Regulations 1998, PART 39 - Schedule of Airworthiness Directives.)\n- Aircraft owners/operators pay for the inspections, repairs and any replacement parts and labour required to meet the Service Bulletin instructions. (Applicability; Compliance; Document.)\n\nIncentives, trade-offs and operational effects\n\n- The time-based inspection schedule creates a recurring maintenance obligation tied to aircraft utilisation (hours in service). Operators face an ongoing cost of inspections every 100 hours once the initial threshold is reached. (Compliance 1–2.)\n- Because the AD requires repair or replacement “as detailed” in the Service Bulletin, operators must obtain and follow that external document to return an engine mount to service; this concentrates practical decision-making and technical responsibility in the content of SB M20-192 rather than in the AD text itself. (Document; Compliance 1–2.)\n- The AD makes continued operation conditional on completing inspections and any required remedial work; therefore operators may choose between increased maintenance expenditure, replacing mounts sooner, or withdrawing aircraft from service until compliance is achieved. (Compliance 1–2.)\n\nCompliance burden and implementation risks\n\n- Administrative and operational burden arises from recurring inspections at 100‑hour intervals and from carrying out repairs or replacements specified in the external Service Bulletin. (Compliance 1–2; Document.)\n- The AD’s prescriptive timing (including a historic reference date) and the reliance on an external Service Bulletin mean implementing parties must access the SB and interpret its technical instructions correctly to be compliant. Errors in following the SB or delays obtaining parts could extend out-of-service time. (Compliance 1–2; Document.)\n\nNet practical effect\n\n- The instrument creates a continuing maintenance requirement for the listed Mooney M20 serials: perform inspections at the specified hour thresholds and follow SB M20-192 to repair or replace mounts as required. (Applicability; Compliance; Document.)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused specifically on engine mount inspection for a narrow class of aircraft. It has not expanded beyond its original purpose."},"complexity_factors":["Very short document (under 200 words)","Only 2 compliance conditions with clear thresholds (450 hours vs under 450 hours)","Single cross-reference to manufacturer Service Bulletin M20-192","Limited applicability: 5 specific aircraft models with enumerated serial number ranges","No defined terms section, no nested exceptions, no conditional logic beyond the hour-based bifurcation"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires owners and operators of specific **Mooney M20 series aircraft** to inspect and potentially repair or replace the **engine mount** (the metal framework that attaches the engine to the aircraft body).\n\n**Who it affects:**\n- Owners and operators of specific Mooney M20 models (M20C, M20D, M20E, M20F, M20G) with specific serial numbers listed in the document.\n\n**What it requires:**\n- **High-time engine mounts** (450+ hours of flight time): Inspect within 50 hours after 19 May 1975, then every 100 hours until fixed or replaced.\n- **All other mounts**: Inspect before reaching 450 hours, then every 100 hours until fixed or replaced.\n- Repairs must follow the manufacturer's Service Bulletin M20-192.\n\n**Why it matters:**\nEngine mounts carry heavy loads and vibration. Fatigue or failure could cause the engine to detach in flight — catastrophic. This AD mandates proactive inspection to catch problems before they become dangerous."}},"importantCases":[],"_links":{"self":"/api/acts/ad-m20-21-engine-mount-inspection-and-repair","history":"/api/acts/ad-m20-21-engine-mount-inspection-and-repair/history","analysis":"/api/acts/ad-m20-21-engine-mount-inspection-and-repair/analysis","conflicts":"/api/acts/ad-m20-21-engine-mount-inspection-and-repair/conflicts","importantCases":"/api/acts/ad-m20-21-engine-mount-inspection-and-repair/important-cases","documents":"/api/acts/ad-m20-21-engine-mount-inspection-and-repair/documents"}}