{"id":"F2006B03264","name":"AD/B747/87 - Aural and Master Fire Warning Systems","slug":"ad-b747-87-aural-and-master-fire-warning-systems","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42688,"registerId":"commonwealth-F2006B03264-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/87 - Aural and Master Fire Warning Systems","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)  \nBoeing 747 Series Aeroplanes\n\nAD/B747/87 Aural and Master Fire Warning Systems 3/91\n\nApplicability: All model 747-400 series aeroplanes listed in the Requirement Document. Requirement: Action in accordance with the technical requirements of FAA AD 90-26-08.\n\nNote: Boeing Alert SB 747-26A2171 also refers.\n\nCompliance: As specified in the Requirement Document with an effective date of 21 March 1991. Background: Reports indicate that with certain Integrated Display System (IDS) software installed,\n\nthe aural and master caution systems of the fire detection system are inoperative.\n\nThis failure cannot be identified during normal system checks, and if not corrected, could result in the failure of the system to annunciate a fire in the APU, engines, wheel wells or cargo compartments.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific technical fault in a specific aircraft model. It has not expanded beyond its original purpose of mandating fire warning system repairs."},"complexity_factors":["Very short document (under 200 words)","Only 1 defined term (Requirement Document, implicitly referencing external FAA AD)","No nested conditional logic or exceptions","Single straightforward requirement: comply with external FAA directive","No cross-references to other Australian legislation beyond Civil Aviation Regulations 1998 Part 39","Clear, unambiguous applicability (all 747-400 series)"],"plain_english_summary":"This is an **Airworthiness Directive** (a mandatory safety order) issued by Australia's Civil Aviation Safety Authority for **Boeing 747-400 aircraft**.\n\n**What it does:**\nIt requires airlines and aircraft operators to fix a dangerous software bug in the fire warning system. Specifically, certain software versions in the Integrated Display System (IDS) can cause the **aural alarms and master warning lights for fires to stop working** — meaning pilots might not hear or see warnings about fires in the engines, auxiliary power unit (APU), wheel wells, or cargo holds.\n\n**Why it matters:**\nThis is a **silent failure** — the broken warning system won't show up during routine checks, so operators won't know it's broken until it's too late. If a fire breaks out and the warnings don't work, the crew might not detect the fire in time to save the aircraft and passengers.\n\n**Who must act:**\nAnyone operating Boeing 747-400 series aircraft must follow the technical instructions in the referenced **FAA Airworthiness Directive 90-26-08** (the US aviation safety authority's equivalent order) and Boeing's Alert Service Bulletin 747-26A2171.\n\n**When:**\nCompliance was required from **21 March 1991**."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The text presents a directive applying to all model 747-400 series aeroplanes listed in the Requirement Document and mandates action in accordance with FAA AD 90-26-08 (Applicability; Requirement). There is no information in the instrument indicating a change in scope from an earlier or original intent; the directive simply adopts external technical requirements and sets an effective compliance date (Requirement; Compliance)."},"complexity_factors":["Cross-reference to an external FAA Airworthiness Directive (FAA AD 90-26-08) rather than containing full technical instructions in the text (Requirement).","Applicability and compliance instructions are specified in a separate Requirement Document, requiring consultation of multiple documents (Applicability; Compliance).","Technical root cause involves software interactions in the Integrated Display System that are not revealed by normal system checks, which complicates diagnosis and verification (Background).","Mention of an additional Boeing Alert Service Bulletin as relevant information increases the number of documents to reconcile (Note)."],"plain_english_summary":"What this instrument does (mechanics)\n\n- Requires that operators of certain Boeing 747-400 series aeroplanes perform the maintenance/technical actions set out in FAA Airworthiness Directive 90-26-08 (the AD) (Requirement).  The specific aeroplane list and the precise compliance instructions are set out in the local Requirement Document (Applicability; Compliance).\n\nWho it affects\n\n- Applies to all model 747-400 series aeroplanes listed in the Requirement Document (Applicability).\n- Practically, this means aircraft owners, operators and their maintenance organisations must carry out the technical work specified by the FAA AD and any referenced Boeing service bulletin (Note).\n\nWhy it matters (official purpose and practical implications)\n\n- The background provided states that, with certain Integrated Display System (IDS) software installed, the aural and master caution portions of the fire detection system can be inoperative and that this failure cannot be detected by normal system checks. If uncorrected, the failure could prevent annunciation of a fire in the APU, engines, wheel wells or cargo compartments (Background).\n- To address that risk, the instrument mandates following the technical requirements of FAA AD 90-26-08 (Requirement). The instrument makes compliance compulsory as specified in the Requirement Document with an effective date (Compliance).\n\nWho pays, who decides, and what behaviour changes\n\n- Who decides: the Civil Aviation Safety Authority (CASA) has issued the directive; the instrument implements or adopts the FAA AD for the listed aircraft (Requirement; Compliance).\n- Who pays: operators/owners and their maintenance providers will incur the costs of performing the mandated technical actions and any associated aircraft downtime, because the instrument requires those actions to be performed on the affected aeroplanes (Applicability; Requirement; Compliance).\n- Behaviour change required: operators must schedule and carry out the specified inspections/repairs/modifications in accordance with FAA AD 90-26-08 (Requirement). They may need to follow the Boeing Alert Service Bulletin cited in the Note where relevant.\n\nCosts, incentives and trade-offs (concrete mechanisms)\n\n- Direct compliance cost: technical work, parts, labour and aircraft out-of-service time required by the FAA AD and the Requirement Document (Requirement; Compliance).\n- Incentives: operators gain the safety benefit of corrected annunciation but incur maintenance costs and downtime. The directive creates a compliance incentive because it is mandatory for the listed aeroplanes (Applicability; Requirement).\n- Opportunity cost: time and resources devoted to complying cannot be used elsewhere (Compliance).\n\nImplementation risk, compliance burden and discretion\n\n- Implementation risk: the underlying failure mode is a software-related IDS fault that may not be revealed by normal checks, increasing the risk that the problem remains latent until a fire event (Background).\n- Compliance burden: the AD cross-references external technical documents (FAA AD 90-26-08 and a Boeing Alert SB). That requires operators and maintainers to obtain and follow those external documents, which creates administrative and technical work beyond a self-contained requirement (Requirement; Note).\n- Bureaucratic discretion: the instrument delegates the specific technical steps and the exact list of affected aeroplanes to the Requirement Document and to the FAA AD it cites, rather than embedding all details in the text. That concentrates technical specification into the referenced documents (Applicability; Requirement; Compliance).\n\nNet operational effect (concise)\n\n- The instrument imposes a mandatory corrective action for listed 747-400s to address an IDS-related failure of aural and master fire warnings. It shifts the immediate financial and operational burden of fixing and verifying the issue onto operators and maintenance organisations, and relies on external technical documents (FAA AD and Boeing service information) to define the exact work to be done (Requirement; Note; Compliance)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-87-aural-and-master-fire-warning-systems","history":"/api/acts/ad-b747-87-aural-and-master-fire-warning-systems/history","analysis":"/api/acts/ad-b747-87-aural-and-master-fire-warning-systems/analysis","conflicts":"/api/acts/ad-b747-87-aural-and-master-fire-warning-systems/conflicts","importantCases":"/api/acts/ad-b747-87-aural-and-master-fire-warning-systems/important-cases","documents":"/api/acts/ad-b747-87-aural-and-master-fire-warning-systems/documents"}}