{"id":"F2006B04633","name":"AD/BELL 407/2 - Warning Horns","slug":"ad-bell-407-2-warning-horns","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44385,"registerId":"commonwealth-F2006B04633-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 407/2 - Warning Horns","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)  \nBell Helicopter Textron Canada (BHTC) 407 Series Helicopters\n\nAD/BELL 407/2 Warning Horns 5/99\n\nApplicability: Model 407 helicopters with Serial Numbers 53000 through 53194 inclusive. Requirement: If not previously accomplished, replace the existing ‘FADEC FAIL’, ‘ENGINE OUT’\n\nand ‘LOW ROTOR RPM’ warning horns with new horns having Part Numbers\n\nVSB628CP, SC628NP and SC628N respectively. Replacement of the horns is to be accomplished in accordance with Bell Helicopter Textron Canada Alert Service Bulletin No 407-97-12 dated 7 October 1997.\n\nNote: Transport Canada AD CF-98-13 refers.\n\nCompliance: Prior to 20 July 1999.\n\nThis Airworthiness Directive becomes effective on 20 May 1999.\n\nBackground: Transport Canada Aviation has advised that analysis of engine failures with this helicopter have shown a need for the sound of the ‘FADEC FAIL’ horn to be distinct and for the ‘ENGINE OUT’ and ‘LOW ROTOR RPM’ warning horns to be louder.\n\nThis Directive facilitates appropriate flight crew reactions to in-flight emergencies by providing more distinct and conspicuous warnings.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope: a specific safety modification for a defined fleet of helicopters. It has not expanded beyond the original intent of replacing defective warning horns."},"complexity_factors":["Single, unambiguous requirement with no conditional logic or exceptions","Only 3 defined part numbers referenced","Clear applicability criteria (specific serial number range)","Single compliance deadline with no phased or alternative compliance options","No cross-references to other legislation sections beyond a single related Canadian directive","Background explanation provided in plain language"],"plain_english_summary":"This safety order requires owners/operators of Bell 407 helicopters (SN 53000–53194) to replace three cockpit audio warning horns — FADEC FAIL, ENGINE OUT, and LOW ROTOR RPM — with specified louder, more distinct part numbers. Prompted by incidents where pilots couldn’t distinguish or hear warnings, the upgrade improves emergency recognition and response; aircraft are grounded if not compliant by 20 July 1999 (effective 20 May 1999)."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive enforces replacement of specified warning horns on a defined subset of Bell 407 helicopters to achieve clearer and louder warnings, consistent with the stated safety purpose. It does not expand applicability beyond the listed serial numbers or broaden requirements to other systems (Applicability; Requirement; Background)."},"complexity_factors":["Narrow applicability limited to Bell 407 serial numbers 53000–53194 (Applicability)","Prescriptive replacement of specific parts by part number (Requirement)","Mandatory compliance deadline (Compliance: prior to 20 July 1999)","Technical work delegated to an external service bulletin for procedures (Bell Alert Service Bulletin No 407-97-12)","Safety-critical but mechanically straightforward action (Background)","Compliance cost and scheduling borne by operators (implicit in Requirement/Compliance)"],"plain_english_summary":"Requires operators of Bell 407 helicopters (serial numbers 53000–53194) to replace the FADEC FAIL, ENGINE OUT and LOW ROTOR RPM warning horns with specified part numbers, following Bell Alert Service Bulletin 407‑97‑12, to be completed before 20 July 1999. (Requirement; Compliance.)\n\nThe measure places installation cost and compliance responsibility on aircraft operators and is intended to make warning sounds more distinct and louder so flight crews can respond to engine-failure events. (Background.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-407-2-warning-horns","history":"/api/acts/ad-bell-407-2-warning-horns/history","analysis":"/api/acts/ad-bell-407-2-warning-horns/analysis","conflicts":"/api/acts/ad-bell-407-2-warning-horns/conflicts","importantCases":"/api/acts/ad-bell-407-2-warning-horns/important-cases","documents":"/api/acts/ad-bell-407-2-warning-horns/documents"}}