{"id":"F2009L01569","name":"AD/B747/391 - Refuel Valve Control Unit","slug":"ad-b747-391-refuel-valve-control-unit","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":78301,"registerId":"commonwealth-F2009L01569-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Boeing 747 Series Aeroplanes","sectionType":"division","heading":"Boeing 747 Series Aeroplanes","content":"### Boeing 747 Series Aeroplanes\n\n| AD/B747/391 | Refuel Valve Control Unit | 5/2009 |\n| ----------- | ------------------------- | ------ |\n\n| Applicability: | Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SR, and 747SP series aeroplanes, as identified in Boeing Alert Service Bulletin 747-28A2291 Revision 1, dated12 March 2009. |\n| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement: | 1. Modify the refuel valve control unit for the reserve fuel tanks, by accomplishing all of the applicable actions specified in the Accomplishment Instructions of Boeing Alert Service Bulletin 747-28A2291 Revision 1.2. Revise the approved maintenance program by incorporating the information specified in Requirement 2(a) or 2(b) of this AD, as applicable.(a) For Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C,747-200F, 747-300, 747SR, and 747SP series aeroplanes: Incorporate AWL No. 28-AWL-20 of Section D of the Boeing 747-100/200/300/SP Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), D6-13747-CMR, Revision January 2007, into the approved maintenance program.(b) For Model 747-400, 747-400D, and 747-400F series aeroplanes: Incorporate AWL No. 28-AWL-25 of Subsection D of the Boeing 747-400 Maintenance Planning Data (MPD) Document, D621U400-9, Section 9, Revision 24, dated June 2006, into the approved maintenance program.Accomplishing the revision in accordance with a later revision of the MPD is an acceptable method of compliance if the revision is approved by the Manager, Seattle Aircraft Certification Office (ACO) of the United States Federal Aviation Administration (FAA).3. No alternative CDCCLs may be used unless the CDCCLs are approved as an AMOC.Terminating Action for Maintenance Program Revision(a) For Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C,747-200F, 747-300, 747SR, and 747SP series aeroplanes: Incorporating AWL No. 28-AWL-20 into the FAA-approved maintenance program in accordance with Requirement 1(a) of AD/B747/379, terminates the action required by Requirement 2(a) of this AD. |\n| | (b) For Model 747-400, 747-400D, and 747-400F series aeroplanes: Incorporating AWL No. 28-AWL-25 into the approved maintenance program in accordance with Requirement 1(c) of AD/B747/378 terminates the action required by Requirement 2(b) of this AD.Note: FAA AD 2008-18-09 Amdt 39-15666 dated 25 August 2008 refers. |\n| Compliance: | For Requirement 1 - Before 17 October 2013, unless previously accomplished.For Requirement 2 - Concurrently with accomplishing the modification required by Requirement 1 of this AD.For Requirement 3 - After accomplishing the applicable action specified in Requirement 2 of this AD. |\n| | This Airworthiness Directive becomes effective on 7 May 2009. |\n| Background: | This AD results from fuel system reviews conducted by the manufacturer. The issuing of this AD is to prevent lightning-induced electrical energy from entering a reserve fuel tank through the refuel valve, which could result in a fuel tank explosion and consequent loss of the aeroplane. |\n\n![](image.001.png) \nJames Coyne \nDelegate of the Civil Aviation Safety Authority\n\n26 March 2009","sortOrder":0},{"sectionNumber":"AD/B747/391","sectionType":"part","heading":"AD/B747/391","content":"## AD/B747/391","sortOrder":1},{"sectionNumber":"Refuel Valve Control Unit","sectionType":"part","heading":"Refuel Valve Control Unit","content":"## Refuel Valve Control Unit","sortOrder":2},{"sectionNumber":"5/2009","sectionType":"part","heading":"5/2009","content":"## 5/2009","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":false,"description":"The AD keeps its original safety-focused scope: requiring modification of the refuel-valve control unit and insertion of specific AWL/MPD maintenance tasks for the listed 747 models to prevent lightning-induced energy entering reserve fuel tanks. There is no expansion beyond those aircraft, components, or the stated lightning-fuel-safety objective; terminating-action cross-references to other ADs only clarify compliance paths."},"complexity_factors":["Multiple affected airframe variants across 747-100/200/300/400/SR/SP families, requiring model-specific instructions.","Mandated hardware modification per Boeing Alert Service Bulletin 747-28A2291 Revision 1 — follows manufacturer procedures and parts/installation steps.","Mandatory incorporation of specific AWLs/MPD items into the operator's approved maintenance program (different AWL/MPD items for 100/200/300/SP vs 400 series).","Interplay with other ADs (AD/B747/379 and AD/B747/378) as terminating actions — operators must track cross-references to determine compliance relief.","Restrictions on using alternative Critical Design Configuration Control Limitations (CDCCLs) unless approved as an AMOC; AMOC/approval routing adds administrative burden and FAA/ACO discretion.","Approval pathway for later MPD revisions requires approval by the FAA Seattle ACO — creates dependency on an external certification office.","Specified compliance deadlines (different actions tied to modification, concurrent maintenance revision, and post-modification compliance) impose scheduling and operational planning constraints."],"plain_english_summary":"Requires operators of specified Boeing 747 models to modify the refuel valve control unit for the reserve fuel tanks and to update the approved maintenance program to include specified AWL/MPD tasks. The mechanical change and the maintenance-task insert aim to stop lightning-induced electrical energy entering a reserve tank. This affects aircraft owners/operators (who pay for work and program changes) and requires compliance with referenced Boeing and FAA documents within stated timeframes."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This AD maintains focused scope on its original safety purpose — preventing fuel tank explosions due to lightning strikes on Boeing 747 aircraft. The document does not exhibit scope creep; it addresses a specific technical vulnerability identified through manufacturer fuel system reviews and mandates targeted hardware modifications and maintenance program updates. The reference to prior ADs for terminating actions represents normal regulatory continuity rather than scope expansion."},"complexity_factors":["Multiple aircraft model variants with different compliance paths (split between older 747-100/200/300/SP/SR series and newer 747-400 series)","Cross-references to external Boeing technical documents (Service Bulletin 747-28A2291 Revision 1, Airworthiness Limitations documents D6-13747-CMR and D621U400-9)","Nested conditional logic: Requirement 2 has sub-requirements (a) and (b) depending on aircraft model, with Requirement 3 applying after Requirement 2","Terminating action provisions that reference other ADs (AD/B747/379 and AD/B747/378) creating interdependence with prior regulatory instruments","Technical aviation acronyms requiring domain knowledge (AD, AWL, CMR, CDCCL, AMOC, ACO, FAA, MPD)","Delegated compliance authority to FAA (US Federal Aviation Administration) for approving later revisions of maintenance planning documents"],"plain_english_summary":"This CASA Airworthiness Directive mandates operators of affected Boeing 747 models to modify the reserve fuel tank refuel valve control unit and revise maintenance programs to add new Airworthiness Limitations, fixing a lightning-induced ignition risk that could cause a fuel-tank explosion. It applies to most 747 passenger and freighter variants and aimed to prevent a recurrence of catastrophic fuel-tank failures; the modification and program updates were required by 17 October 2013."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-391-refuel-valve-control-unit","history":"/api/acts/ad-b747-391-refuel-valve-control-unit/history","analysis":"/api/acts/ad-b747-391-refuel-valve-control-unit/analysis","conflicts":"/api/acts/ad-b747-391-refuel-valve-control-unit/conflicts","importantCases":"/api/acts/ad-b747-391-refuel-valve-control-unit/important-cases","documents":"/api/acts/ad-b747-391-refuel-valve-control-unit/documents"}}