{"id":"F2006B01833","name":"AD/A109/49 - Battery Bus Circuit Breaker","slug":"ad-a109-49-battery-bus-circuit-breaker","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41031,"registerId":"commonwealth-F2006B01833-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)  \n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n![](image.001.png)  \n\nAgusta A109 Series Helicopters","sortOrder":0},{"sectionNumber":"AD/A109/49 Battery Bus Circuit Breaker 3","sectionType":"part","heading":"AD/A109/49 Battery Bus Circuit Breaker 3/2004","content":"# AD/A109/49 Battery Bus Circuit Breaker 3/2004\n\nApplicability: A109E series helicopters as follows:\n\n    All serial numbers (S/N) up to and including 11077 that have kits part number 109-0812-04-101, or -103, or -107, or -109 installed, and\n\n    b. S/N 11078 up to and including 11122.\n\nRequirement: Modify the emergency electrical bus in accordance with Agusta Mandatory Bollettino Tecnico 109EP-39 dated 25 November 2003.\n\nNote: ENAC AD 2003-384 refers.\n\nCompliance: No later than 31 March 2004.\n\nThis Airworthiness Directive becomes effective on 18 March 2004.\n\nBackground: The Italian Ente Nazionale per l’Aviazone Civile has advised that Agusta, whilst carrying out an investigation into the emergency busses of the A109E helicopter, discovered that in the event of a double generator failure the 25 Amp “BATT BUS” circuit breaker could trip. This Directive requires the modification of the emergency electrical bus installation by the replacement of the “BATT BUS” circuit breaker with a 35 Amp rated circuit breaker.\n\n![](image.002.png)  \n\nJames Coyne\n\nDelegate of the Civil Aviation Safety Authority 4 February 2004\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 25 February 2004.","sortOrder":1}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific unsafe condition in a particular helicopter model's electrical system. No scope creep is evident; it targets exactly the safety issue identified (circuit breaker tripping during dual generator failure) without expanding into unrelated systems or operational requirements."},"complexity_factors":["Single, specific technical requirement (replace one circuit breaker)","Limited applicability — only two defined serial number ranges with specific equipment kits","No nested exceptions or conditional logic beyond the applicability criteria","Clear compliance deadline with no alternative methods or phased implementation","Short document (under 300 words) with minimal cross-referencing (one reference to Italian aviation authority directive and Agusta technical bulletin)","Only one defined term implicitly used (Bollettino Tecnico — Italian for technical bulletin)"],"plain_english_summary":"This Airworthiness Directive requires owners/operators and maintenance organisations of certain Agusta A109E helicopters to replace the 25 A \"BATT BUS\" circuit breaker with a 35 A unit, per Agusta technical instructions (Bollettino Tecnico 109EP-39). \n\nThe change prevents the breaker tripping during a double generator failure — preserving emergency electrical power and reducing the risk of loss of critical systems. Compliance is required by 31 March 2004."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This AD converts a previously optional or as‑fitted component configuration into a mandatory configuration for listed A109E helicopters: it requires replacing the existing 25A BATT BUS circuit breaker with a 35A unit and modifying the emergency electrical bus per Agusta Bollettino 109EP-39 (Requirement; Background; Applicability). The AD thus changes the installed electrical protection specification for affected serial numbers and imposes a compliance obligation on operators by 31 March 2004 (Compliance)."},"complexity_factors":["Narrow, serial-numbered applicability combining helicopter S/N ranges and specific kit part numbers (Applicability).","Mandatory technical action requires compliance with an external manufacturer document: Agusta Mandatory Bollettino Tecnico 109EP-39 dated 25 Nov 2003 (Requirement).","Fixed, short compliance deadline (No later than 31 March 2004) creating scheduling pressure for operators (Compliance).","Change to a specific electrical component rating (replace 25 Amp breaker with 35 Amp) — simple hardware swap but requires correct part procurement and installation (Background).","Cross-reference to foreign authority AD (ENAC AD 2003-384), implying reliance on another regulator's findings (Note).","Regulatory authority and enforcement set by CASA delegate; directive effective date and delegate signature establish mandatory legal force (Effective date; Delegate signature).","Practical implementation factors: availability of specified parts, maintenance manpower/time, and inspection to verify correct installation (inferred from Requirement and Background)."],"plain_english_summary":"This AD requires certain Agusta A109E helicopters (specified serial numbers and kit part numbers) to modify the emergency electrical bus by replacing the 25 Amp “BATT BUS” circuit breaker with a 35 Amp unit, following Agusta Mandatory Bollettino Tecnico 109EP-39. It affects operators who must obtain parts and complete the modification by 31 March 2004 to address a risk that the 25A breaker could trip if both generators fail."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-a109-49-battery-bus-circuit-breaker","history":"/api/acts/ad-a109-49-battery-bus-circuit-breaker/history","analysis":"/api/acts/ad-a109-49-battery-bus-circuit-breaker/analysis","conflicts":"/api/acts/ad-a109-49-battery-bus-circuit-breaker/conflicts","importantCases":"/api/acts/ad-a109-49-battery-bus-circuit-breaker/important-cases","documents":"/api/acts/ad-a109-49-battery-bus-circuit-breaker/documents"}}