{"id":"F2006B09417","name":"AD/ELECT/4 - Magnetos BTH - Earthing Modification","slug":"ad-elect-4-magnetos-bth-earthing-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":53795,"registerId":"commonwealth-F2006B09417-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ELECT/4 - Magnetos BTH - Earthing Modification","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 107 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nElectrical Equipment\n\nAD/ELECT/4 Magnetos BTH \\- Earthing Modification NK\n\nApplicability: BTH AG4, SG4 and MC1 types with screened contact breaker covers.\n\nRequirement: Modify the contact breaker cover as follows to ensure positive connection of the magneto switch lead to the magneto earthing spring and brush assembly.\n\n    Remove the earthing spring and brush assembly from the contact breaker cover.\n\n    2. Remove switch lead set screw and tab washer. Drill out thread for this screw in insert.\n\n    3. Cut channel of approximately 1/8\" width in brass insert, sloping from bottom of drilled hole to top of insert for earthing spring as shown in Fig. 1 of this Section. Radius all corners to remove sharp edges.\n\nNote: This channel may be conveniently cut by using a small grinding wheel (3/32 in. or 1/8 in. diameter) in an air or electric drill.\n\n    4. Replace contact breaker cover spring and brush assembly.\n\n![Magnetos BTH - Earthing Modification](image.002.png)  \n\nor ANO 107.2.16.2.3.\n\nCompliance: Before installation in an aircraft.","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1104},"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This directive remains tightly focused on its original purpose: rectifying a specific earthing defect in three specific models of BTH magnetos. There is no evidence of scope creep or expansion beyond this targeted safety repair."},"complexity_factors":["Technical aviation engineering terminology (magnetos, contact breaker covers, earthing springs)","Precise mechanical specifications requiring specialist tools (1/8 inch channel, 3/32 inch grinding wheel)","Reference to external technical standard (ANO 107.2.16.2.3) without full context","Reliance on accompanying diagram (Fig. 1) not fully reproduced in text"],"plain_english_summary":"This Airworthiness Directive requires a mandatory modification to BTH magnetos (models AG4, SG4, MC1 with screened contact breaker covers) before installation. Maintenance engineers and owners must ensure the contact-breaker cover’s earthing connection is corrected — removing and refitting the earthing spring/brush and making small drill/cut alterations to a brass insert — to secure proper grounding. \n\nIt prevents magneto switch failure that could stop the engine from shutting down when ignition is turned off."}},"importantCases":[],"_links":{"self":"/api/acts/ad-elect-4-magnetos-bth-earthing-modification","history":"/api/acts/ad-elect-4-magnetos-bth-earthing-modification/history","analysis":"/api/acts/ad-elect-4-magnetos-bth-earthing-modification/analysis","conflicts":"/api/acts/ad-elect-4-magnetos-bth-earthing-modification/conflicts","importantCases":"/api/acts/ad-elect-4-magnetos-bth-earthing-modification/important-cases","documents":"/api/acts/ad-elect-4-magnetos-bth-earthing-modification/documents"}}