{"id":"F2006B03206","name":"AD/B747/312 - Fire Extinguisher System Tube","slug":"ad-b747-312-fire-extinguisher-system-tube","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42578,"registerId":"commonwealth-F2006B03206-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# ![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\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\nBoeing 747 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/B747/312 Fire Extinguisher System Tub","sectionType":"part","heading":"AD/B747/312 Fire Extinguisher System Tube 10/2004","content":"# AD/B747/312 Fire Extinguisher System Tube 10/2004\n\nApplicability: Model 747-400 and 747-400D series aeroplanes, as listed in Boeing Service Bulletin (SB) 747-26A2270, Revision 2 dated 26 June 2003.\n\nRequirement: Either inspect or pressure test the fire extinguishing system tube as detailed in Requirement 1 or 3 of this Directive.\n\n    Perform a detailed inspection of the fire extinguishing system tube and clamps for correct installation, either using an inspection hole and boroscope or with the floor panel removed, per Boeing SB 747-26A2270 Revision 2. If the fire extinguishing system tube is installed correctly no further action is required by this Directive.\n\n    2. If the fire extinguishing system tube is installed incorrectly, remove the fire extinguishing system tube and perform a detailed inspection of the fire extinguishing system tube for chafing/damage per Boeing SB 747-26A2270 Revision 2.\n\n    If no chafing/damage is found, install the existing fire extinguishing system tube per Figure 3 of Boeing SB 747-26A2270 Revision 2.\n\n    b. If any chafing/damage is found, replace the fire extinguishing system tube with a new tube or repair the fire extinguishing system tube, per Boeing SB 747-26A2270 Revision 2, and install the new or repaired tube per Figure 3 of Boeing SB 747-26A2270 Revision 2.\n\n    3. Perform a pressure test of the fire extinguishing system tube to check for leakage of the fire-extinguishing agent per Boeing SB 747-26A2270 Revision 2.\n\n    4. If any leakage is found during the pressure test as detailed in Requirement 3 of this Directive, replace the fire extinguishing system tube with a new tube or repair the fire extinguishing system tube, per Boeing SB 747-26A2270 Revision 2, and install the new or repaired tube per Figure 3 of Boeing SB 747-26A2270 Revision 2.\n\nNote: FAA AD 2004-09-33 Amdt 39-13624 refers.","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD is narrowly targeted to correct an identified unsafe condition on specific Boeing 747 models and requires inspection/pressure testing and repair/replacement per the Boeing service bulletin. The directive does not broaden the regulated activities beyond that safety correction (it does not add unrelated obligations or additional aircraft types). The scope therefore remains aligned with the AD’s stated corrective purpose (see Applicability and Requirements 1–4)."},"complexity_factors":["Limited applicability: only Model 747-400 and 747-400D aircraft listed in a single Boeing SB (keeps scope narrow)","Two alternative compliance methods (inspection with boroscope or floor-panel removal; or pressure test) create conditional choice","Three main conditional outcomes: correctly installed (no further action); incorrectly installed but undamaged (reinstall per figure); damaged/leaking (repair or replace) (nested but shallow)","Cross-reference to Boeing Service Bulletin 747-26A2270 Revision 2 for procedural detail (external dependency)","Reference to related FAA AD (informational cross-jurisdictional link)","Numbered requirements are few and procedural rather than heavily qualified (low internal branching)"],"plain_english_summary":"**What this directive does (mechanically)**\n\n- This Airworthiness Directive (AD) applies to Boeing 747-400 and 747-400D aeroplanes listed in Boeing Service Bulletin (SB) 747-26A2270, Revision 2 (Applicability).  \n- It requires operators to either:  \n  - perform a detailed visual inspection of a specified fire-extinguishing system tube and its clamps (Requirement 1), or  \n  - perform a pressure test of that tube to check for leakage (Requirement 3).  \n- If the tube is installed correctly on inspection, no further action is required (Requirement 1).  \n- If the tube is installed incorrectly, the tube must be removed and inspected for chafing or damage; if none is found it is reinstalled per the Boeing SB; if damage is found it must be repaired or replaced and reinstalled per the Boeing SB (Requirement 2).  \n- If a pressure test reveals leakage, the tube must be repaired or replaced and reinstalled per the Boeing SB (Requirement 4).  \n- The directive points the mechanic/operator to Boeing SB 747-26A2270 Rev 2 for the detailed steps, mounting configuration (Figure 3) and repair/replacement procedures. The AD also notes a related FAA AD for reference.\n\n**Who this affects**\n\n- Aircraft operators that own or operate Boeing 747-400/400D aeroplanes listed in the cited Boeing service bulletin.  \n- Maintenance organisations and licensed aircraft engineers who carry out inspections, pressure tests, repairs and replacements in accordance with the Boeing SB.  \n- Potentially suppliers of replacement tubes and associated clamps, if replacements are required.\n\n**Why it matters (stated safety rationale and mechanical effect)**\n\n- The AD addresses a potential unsafe condition in the fire-extinguishing system tube (risk of incorrect installation, chafing leading to damage, or leakage). The mechanical effect required is inspection or pressure testing and, if necessary, repair or replacement to ensure the integrity and correct routing/clamping of the tube so the extinguishing system can operate as intended (Requirements 1–4).\n\n**Costs, incentives and trade-offs**\n\n- Who pays: the aircraft operator pays for inspections, pressure tests, labour, any removal of floor panels, parts and repairs or replacements (Requirements 1–4).  \n- Direct costs/time: inspections may require opening access (inspection hole or floor panel removal), boroscope use, or pressure test equipment and time in the hangar; if replacement or repair is required, there is additional parts cost and aircraft downtime (Requirement 1–4).  \n- Behavioural choices: operators can choose the inspection route (visual/boroscope) or the pressure-test route depending on access, cost and time considerations (Requirements 1 and 3).  \n- Implementation risk/constraints: availability of authorised parts or qualified repair capability could affect how quickly an operator can rectify a defect discovered under the AD (Requirement 2 and 4).  \n- Administrative/bureaucratic discretion: the AD delegates the precise corrective steps to the Boeing SB (cited throughout), so compliance requires following those manufacturer instructions as accepted by the regulator; the CASA delegate issued the AD under CASR subregulation 39.1(1) (front matter).\n\n**Effects on private enterprise and market factors**\n\n- Maintenance work is concentrated on operators and maintenance organisations — operators bear the cost; maintenance providers receive business from inspections/repairs.  \n- The requirement to follow Boeing's SB centralises the technical compliance path around the manufacturer’s procedures (Requirement references), which focuses repair/replacement specifications on Boeing-approved parts and methods.  \n- There is limited direct effect on competition beyond the fact that licensed maintenance organisations with access to the SB and authorised parts will perform the work; small operators without in-house capability may face higher relative costs due to outsourcing and aircraft downtime.\n\n**Scope and substitution effects**\n\n- The AD is tightly scoped to a specific part on specified 747 models (Applicability). Operators can substitute between inspection methods (visual/boroscope) and pressure-test methods where allowed, but if defects are found repair or replacement is mandatory (Requirements 1–4).  \n\n**Summary of practical implications**\n\n- Operators must inspect or pressure-test the identified fire-extinguishing tube and, if required, repair or replace it per the Boeing service bulletin. Noncompliance would leave the aircraft with a recognised unsafe condition and contrary to the AD’s requirements. The principal trade-offs are operator expense and aircraft downtime versus restoring or assuring the fire-extinguishing system’s integrity."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope. It addresses a specific unsafe condition (potential fire extinguisher tube damage/incorrect installation) on a specific aircraft type (Boeing 747-400 series). There is no evidence of scope creep; it does not expand to cover other aircraft systems, other Boeing models, or unrelated maintenance issues."},"complexity_factors":["Short, single-purpose directive with clear applicability (one aircraft model series)","Straightforward binary compliance path: inspect OR pressure test","Only 4 numbered requirements with simple conditional logic (if X then Y)","Single external reference to a Boeing Service Bulletin (SB 747-26A2270 Revision 2) — the actual technical instructions are incorporated by reference rather than reproduced","No defined terms section, no cross-references to other legislation beyond the enabling regulation (CASR 1998 subregulation 39.1(1))","Minimal exceptions or nested conditions — essentially: check it, and if broken, fix it"],"plain_english_summary":"This AD requires operators of certain Boeing 747-400/-400D aircraft to inspect and, if needed, repair or replace engine fire-extinguisher system tubes per Boeing Service Bulletin 747-26A2270 Rev.2. Compliance may be by borescope/floor-panel visual inspection (with removal/repair if incorrectly installed or damaged) or by pressure/leak testing. It targets maintenance teams and operators to prevent extinguisher failure during an engine fire, preserving aircraft and passenger safety."},"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-b747-312-fire-extinguisher-system-tube","history":"/api/acts/ad-b747-312-fire-extinguisher-system-tube/history","analysis":"/api/acts/ad-b747-312-fire-extinguisher-system-tube/analysis","conflicts":"/api/acts/ad-b747-312-fire-extinguisher-system-tube/conflicts","importantCases":"/api/acts/ad-b747-312-fire-extinguisher-system-tube/important-cases","documents":"/api/acts/ad-b747-312-fire-extinguisher-system-tube/documents"}}