{"id":"F2006B04322","name":"AD/BELL 204/15 - Fire Detection System - Audible Warning","slug":"ad-bell-204-15-fire-detection-system-audible-warning","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44137,"registerId":"commonwealth-F2006B04322-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 204/15 - Fire Detection System - Audible Warning","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Bell Helicopter Textron 204 Series Helicopters\n\n \n\nAD/BELL 204/15 Fire Detection System - Audible Warning NK\n\nApplicability: All models.\n\n \n\nRequirement:  Modify the engine fire detection system to include an audible warning. The warning shall be unmistakeable from any other audible warning and shall be capable of being manually silenced.\n\n \n\nCompliance: Before 1 January 1975.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The instrument itself sets a narrow, specific retrofit requirement for Bell 204 series helicopters: fit an unmistakeable, manually silencable audible engine‑fire warning and comply by a stated date. The text does not indicate any expansion or narrowing of that technical scope relative to what is stated, so no change in scope is identified from the instrument's own terms. (Applicability; Requirement; Compliance)"},"complexity_factors":["Single, narrowly framed mandatory action (modify fire detection system to add an audible warning). (Requirement)","Applies to a clearly defined population: all Bell 204 series helicopters. (Applicability)","Functional (not prescriptive) technical specification: sets characteristics (unmistakeable, manually silencable) but not a single design or supplier. (Requirement)","Fixed compliance deadline (historical date) creates a binary compliance state rather than phased implementation. (Compliance)","Implementation complexity depends on technical compatibility and parts/labour availability rather than statutory ambiguity. (Requirement)"],"plain_english_summary":"What this instrument changes, mechanically\n\n- It requires a modification to the engine fire detection system on Bell 204 series helicopters so the system provides an audible warning. The audible warning must be unmistakeable from any other audible warning and must be capable of being manually silenced. (Requirement)\n\nWho the rule applies to and who enforces it\n\n- The directive applies to all Bell 204 series helicopters. (Applicability)\n- The directive is issued under the Commonwealth civil aviation framework and is enforced through the Civil Aviation Safety Authority's airworthiness directive regime. (header)\n\nDeadline and legal effect\n\n- Owners/operators were required to complete the modification before 1 January 1975. (Compliance)\n\nStated purpose and how it operates in practice\n\n- The stated purpose (implicit in the text) is to add an unmistakable audible alert for engine fire conditions so flight crew can detect and respond to engine fires. The text describes the mechanical change required (an audible warning that is unmistakeable and manually silenced) rather than prescribing a single technical design. (Requirement)\n\nWho pays, who decides, and what behaviour changes\n\n- Who pays: aircraft owners/operators bear the cost of the retrofit (parts, labour, any testing or approval steps). (Applicability; Requirement; Compliance)\n- Who decides: the civil aviation authority issued the mandatory requirement; owners/operators (or their contracted maintenance organisations) choose the technical solution that meets the stated characteristics. (header; Requirement)\n- Behaviour changes: operators must schedule and fund a retrofit for each affected helicopter and may use third‑party maintenance organisations to perform the work. After installation, crews will receive a new audible alert for engine fire conditions and will have the ability to silence it manually. (Requirement)\n\nCompliance burden, discretion and implementation risk\n\n- Compliance burden: the action is a retrofit across the fleet (all models). That generates direct costs (components and labour) and indirect costs (downtime while the modification is fitted). (Applicability; Compliance)\n- Technical discretion: the directive sets functional requirements (audible, unmistakeable, manually silencable) but does not prescribe a single hardware design or supplier. That leaves implementers discretion to select or design a solution that meets the functional criteria. This creates variation in costs and timing depending on chosen solutions and availability of compatible equipment. (Requirement)\n- Implementation risks and trade‑offs: risks include parts availability, compatibility with existing electrical/avionics systems, and the need for any testing or approval of the modification. The manual‑silence feature reduces nuisance alert persistence but also means crews can silence the warning; operators and maintainers must manage procedures and training accordingly. (Requirement)\n\nMarket effects and allocation of benefits and costs\n\n- Costs are concentrated on owners/operators who must retrofit their helicopters. Maintenance and avionics suppliers may receive demand for parts and labour. The directive imposes a uniform technical standard on all affected aircraft, which limits variation in safety performance among operators but does not prescribe a single supplier or design. (Applicability; Requirement)\n\nOpportunity costs and enforcement\n\n- Opportunity costs include time and resources spent on the retrofit instead of other maintenance or upgrades. Enforcement is by the aviation regulator via the airworthiness directive mechanism and the specified compliance date. (Compliance; header)\n\nSource citations\n\n- Applicability: \"All models.\" (Applicability)\n- Requirement: \"Modify the engine fire detection system to include an audible warning. The warning shall be unmistakeable from any other audible warning and shall be capable of being manually silenced.\" (Requirement)\n- Compliance date: \"Before 1 January 1975.\" (Compliance)\n\nNotes on interpretation\n\n- The text prescribes functional performance characteristics rather than a single technical fix. That assigns choice of technical implementation to owners/operators and their maintenance providers, within the bounds of regulatory approval and the directive's stated characteristics. (Requirement)"},"kimi_summary":{"content_quality":"ok","complexity_score":1,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive from 1975 (based on the compliance date) addressing a specific safety concern. There is no evidence of scope creep; it does exactly what it says on the tin — mandates an audible fire warning for one helicopter type."},"complexity_factors":["Single, unambiguous requirement with no conditional logic","No defined terms requiring interpretation","No cross-references to other legislation or regulations","Straightforward applicability (all models)","Fixed compliance date with no exceptions or extensions mentioned","Total length is approximately 100 words"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\nIt requires owners and operators of **Bell 204 series helicopters** to modify their engine fire detection systems. Specifically, they must add an **audible warning** (a sound alarm) that:\n- Is clearly different from any other warning sounds in the cockpit\n- Can be manually turned off by the pilot\n\n**Who it affects:**\nAnyone who owns or operates any model of Bell 204 helicopter in Australia.\n\n**Why it matters:**\nEngine fires in helicopters are extremely dangerous. This rule ensures pilots get immediate, unambiguous audio alerts about fire detection, giving them critical seconds to respond. The requirement for a distinct sound prevents confusion with other warnings (like low fuel or altitude alerts), and the manual silencing feature stops the alarm from becoming a distraction once the pilot is aware of the problem."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-204-15-fire-detection-system-audible-warning","history":"/api/acts/ad-bell-204-15-fire-detection-system-audible-warning/history","analysis":"/api/acts/ad-bell-204-15-fire-detection-system-audible-warning/analysis","conflicts":"/api/acts/ad-bell-204-15-fire-detection-system-audible-warning/conflicts","importantCases":"/api/acts/ad-bell-204-15-fire-detection-system-audible-warning/important-cases","documents":"/api/acts/ad-bell-204-15-fire-detection-system-audible-warning/documents"}}