{"id":"F2006B03150","name":"AD/B747/251 Amdt 1 - Fuel Quantity Indicating System Wiring","slug":"ad-b747-251-amdt-1-fuel-quantity-indicating-system-wiring","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42522,"registerId":"commonwealth-F2006B03150-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/251 Amdt 1 - Fuel Quantity Indicating System Wiring","content":"![](image.001.png)\n\nAIRWORTHINESS DIRECTIVE\n\n![](image.001.png)  \n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/B747/251 and issues the following 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\n\nAD/B747/251\n\nAmdt 1\n\n  \nFuel Quantity Indicating System Wiring 4/2004\n\nApplicability: All Model 747-100, \\-200, \\-300, \\-SP and \\-SR series aeroplanes.\n\nRequirement: Replace all the fuel quantity indication system (FQIS) wiring outside of the fuel tanks and surge tank with shielded wiring and install the new wiring so as to provide separation of that wiring from other aeroplane systems wiring in accordance with a method approved by Manager, Seattle Aircraft Certification Office, Federal Aviation Administration (FAA), Transport Airplane Directorate.\n\nInstallations of Smiths Industries Transient Suppression Units in accordance with Boeing SB 747-28-2233 dated 22 February 2001 (FAA STC ST00181SE refers), or in accordance with methods approved in FAA Letters 130S-00-0391 or 130S-03-375 are considered acceptable means of compliance with this Directive.\n\nNote: FAA AD 98-20-40 Amdt 39-10808 refers.\n\nCompliance: Remains unchanged as ‘Before 31 December 2001’.\n\nThis Amendment becomes effective on 15 April 2004.\n\nBackground: The FAA issued AD 98-20-40 following a failure analysis of the FQIS system and testing, which revealed that excessive energy levels in the electrical wiring and probes of the fuel system could be induced by electrical transients. The original Directive required actions intended to prevent electrical transients, introduced by electromagnetic interference or electrical short circuits from causing arcing of the FQIS electrical wiring or probes in the fuel tank(s). Such arcing could result in ignition of the fuel tank(s). The Directive also included FAA STC ST00181SE as an alternate method of compliance.\n\nThis amendment introduces an additional alternate method of compliance to allow the use of alternate indicators in previously modified aeroplanes.\n\nBoeing 747 Series Aeroplanes\n\nAD/B747/251 Amdt 1 (continued)\n\nThe original issue of this Directive became effective on 9 August 2001.\n\n![Signature of James Coyne, Delegate of the Civil Aviation Safety Authority.](image.002.png)  \n\nJames Coyne\n\nDelegate of the Civil Aviation Safety Authority 4 March 2004\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 24 March 2004.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The amendment did not expand the set of aircraft subject to the directive or change the original compliance deadline. It only added an additional acceptable alternative means of compliance (allowing certain alternate indicators/transient suppression installations for previously modified aeroplanes). That is an adjustment to compliance options rather than a substantive widening of scope or purpose."},"complexity_factors":["Short document (single-aircraft-type AD, limited number of operative paragraphs)","One primary technical requirement (replace FQIS external wiring with shielded wiring and separate from other wiring)","Several cross-references to external documents (FAA AD 98-20-40, Boeing SB 747-28-2233 / FAA STC ST00181SE, FAA Letters 130S-00-0391 and 130S-03-375)","Conditional acceptance of alternative methods of compliance (requires FAA Manager approval or specified SB/STC/letters)","Potentially confusing compliance timing (compliance stated as 'Before 31 December 2001' while amendment effective in 2004)","Relies on another authority's approvals (Manager, Seattle ACO), introducing extra administrative dependency"],"plain_english_summary":"**What this Airworthiness Directive (AD) does**\n\n- Requires operators of the affected Boeing 747 models to fix a potential fire/ignition risk in the fuel quantity indicating system (FQIS) wiring. Specifically, it mandates replacing all FQIS wiring that runs outside the fuel tanks and surge tank with shielded wiring and routing that wiring so it is separated from other aeroplane wiring. (Requirement)\n\n- Allows certain alternative fixes instead of full rewiring if those alternatives are installed in accordance with specified FAA-approved methods or the Boeing service bulletin listed. In particular, installations of Smiths Industries Transient Suppression Units per Boeing SB 747-28-2233 (FAA STC ST00181SE) or methods approved in two named FAA letters are treated as acceptable compliance. (Requirement; Note)\n\n**Which aircraft are affected**\n\n- All Boeing 747-100, -200, -300, -SP and -SR series aeroplanes. (Applicability)\n\n**Why the rule exists (background)**\n\n- Testing and failure analysis showed the FQIS electrical wiring and probes could pick up excessive energy from electrical transients. Those transients can cause arcing in wiring or probes located in fuel tanks, which in turn could ignite fuel. The AD implements corrective work intended to prevent those transients from causing arcing and ignition. (Background)\n\n**How it must be done and who approves alternatives**\n\n- The new shielded wiring and any changes must be installed using a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Transport Airplane Directorate. The AD explicitly accepts the Boeing service bulletin/FAA STC route or the two FAA letters as alternative means of compliance. (Requirement)\n\n**Timing and effect of this amendment**\n\n- The AD repeats the original compliance deadline as written: \"Before 31 December 2001\". The amendment itself became effective on 15 April 2004 and its primary change was to add an extra acceptable alternative compliance method. (Compliance; This Amendment)\n\n**Who pays and who decides**\n\n- Aircraft operators (owners/airlines) bear the cost: either rewiring the FQIS wiring with shielded cable and rerouting it, or installing an approved transient suppression unit or other FAA-approved alternative. The CASA delegate issues and enforces the AD, but compliance options rely on FAA approvals (Manager, Seattle ACO) or the specific Boeing service bulletin / FAA letters listed. (Requirement; Note)\n\n**Practical implications, incentives and trade-offs**\n\n- Direct costs and downtime: Full rewiring is labour- and parts-intensive and will impose aircraft downtime and repair costs on operators.\n- Substitution effect: Operators may choose an approved suppression-unit installation (if available and appropriate) instead of full rewiring; that can lower cost and downtime if it meets the FAA/CASA acceptance criteria. (Requirement; Note)\n- Administrative burden: Using any alternative method requires either following the specified Boeing service bulletin/STC or obtaining FAA-approval under the Seattle ACO manager’s authority; that adds paperwork and possibly technical evaluation time. (Requirement)\n- Implementation risk and jurisdictional dependence: The AD depends on FAA approvals and specified FAA documents for acceptable alternatives, which means CASA enforcement is tied to FAA certification decisions for those alternatives. (Requirement; Note)\n\n**What changed in this amendment compared to the original AD**\n\n- This amendment does not broaden the set of affected aeroplanes or change the original compliance deadline. It adds one more acceptable alternative means of compliance (allowing certain alternate indicators or suppression installations on aeroplanes that were already modified), thereby providing operators an additional route to compliance without requiring full rewiring. (Background; This Amendment)\n\n(References in parentheses indicate the AD section where each point is set out: Applicability, Requirement, Note, Compliance, Background, This Amendment.)"},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment maintains the original scope of the directive. It does not expand applicability to new aircraft models or introduce new safety concerns. The amendment solely adds an additional alternative method of compliance (Smiths Industries Transient Suppression Units) to the existing requirement, which is a standard administrative update within the original safety intent."},"complexity_factors":["Short, single-purpose document (approximately 400 words)","Only 2 defined technical terms (FQIS, STC — Special Type Certificate)","Minimal cross-referencing (only references to FAA AD 98-20-40 and Boeing service bulletin)","Clear, linear structure with standard AD format (Applicability, Requirement, Compliance, Background)","Single conditional element (alternative compliance method introduced in amendment)","No nested exceptions or complex logical structures"],"plain_english_summary":"This AD orders owners/operators of Boeing 747-100/200/300/-SP/-SR aircraft to eliminate a fuel-tank ignition risk by replacing FQIS wiring outside the tanks with shielded, separated wiring (or, per the amendment, installing FAA‑approved Smiths transient suppression units as an alternative). It targets airlines and operators because unshielded wiring can arc and ignite fuel — the hazard linked to the TWA Flight 800 tragedy."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-251-amdt-1-fuel-quantity-indicating-system-wiring","history":"/api/acts/ad-b747-251-amdt-1-fuel-quantity-indicating-system-wiring/history","analysis":"/api/acts/ad-b747-251-amdt-1-fuel-quantity-indicating-system-wiring/analysis","conflicts":"/api/acts/ad-b747-251-amdt-1-fuel-quantity-indicating-system-wiring/conflicts","importantCases":"/api/acts/ad-b747-251-amdt-1-fuel-quantity-indicating-system-wiring/important-cases","documents":"/api/acts/ad-b747-251-amdt-1-fuel-quantity-indicating-system-wiring/documents"}}