{"id":"F2008L01403","name":"AD/B737/321 - Fuel Systems Airworthiness Limitations & Motor Operated valves","slug":"ad-b737-321-fuel-systems-airworthiness-limitations-motor-operated-valves","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":73661,"registerId":"commonwealth-F2008L01403-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Boeing 737 Series Aeroplanes","sectionType":"division","heading":"Boeing 737 Series Aeroplanes","content":"### Boeing 737 Series Aeroplanes\n\n| AD/B737/321 | Fuel Systems Airworthiness Limitations & Motor Operated valves | 6/2008 |\n| ----------- | -------------------------------------------------------------- | ------ |\n\n| Applicability: | Model 737-600, -700, -700C, -800 and -900 series aeroplanes, as identified in Boeing Alert Service Bulletin (ASB) 737-28A1207, dated 15 February 2007.                                                                                                                                                                                                                                                                                                |\n| -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Inspect the following three motor-operated valves (MOVs) to determine whether an MOV with the affected part number, identified in the Accomplishment Instructions of ASB 737-28A1207, is installed:                                                                                                                                                                                                                                                |\n|                | a. Left engine fuel shutoff (spar) valve,b. Right engine fuel shutoff (spar) valve, andc. Fuel crossfeed valve.                                                                                                                                                                                                                                                                                                                                       |\n|                | A review of aeroplane’s maintenance records is acceptable in lieu of this inspection if the part number of the part can be conclusively determined from that review.                                                                                                                                                                                                                                                                                  |\n|                | 2. Accomplish all applicable related investigative and corrective actions in accordance with the Accomplishment Instructions of ASB 737-28A1207.                                                                                                                                                                                                                                                                                                      |\n|                | 3. Revise the airworthiness limitations (AWL) section of the Instructions for Continued Airworthiness for the aeroplane by incorporating the information specified in Section F, ''AIRWORTHINESS LIMITATIONS–FUEL SYSTEM AWLs,'' of Boeing 737-600/700/700C/700IGW/800/900 MPD Document D626A001-CMR, Section 9, Revision November 2006 R1, into the Maintenance Planning Data (MPD) to incorporate AWL No 28-AWL-21 No. 28-AWL-22 and No. 28-AWL-24. |\n|                | Accomplishing the revision in accordance with a later revision of the MPD document is an acceptable method of compliance if the revision is approved by the Manager, Seattle Aircraft Certification Office (ACO), United States Federal Aviation Administration (FAA).                                                                                                                                                                                |\n|                | Later revisions of the ASB 737-28A1207, approved by the FAA as an Alternate Method of Compliance (AMOC) to FAA AD 2008-06-03, are considered acceptable for compliance with the equivalent Requirements of this Directive.                                                                                                                                                                                                                            |\n\n|             | Note: FAA AD 2008-06-03 Amdt 39-15415 refers.                                                                                                                                                                                                                                                                     |\n| ----------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Compliance: | For Requirement 1 - Within 60 months after the effective date of this Directive.                                                                                                                                                                                                                                  |\n|             | For Requirement 2 - Before further flight after the Requirement 1 inspection/determination.                                                                                                                                                                                                                       |\n|             | For Requirement 3 - Concurrent with Requirement 1.                                                                                                                                                                                                                                                                |\n|             | This Airworthiness Directive becomes effective on 5 June 2008.                                                                                                                                                                                                                                                    |\n| Background: | This Directive requires inspecting to determine if certain motor-operated shutoff valve actuators for the fuel tanks are installed together with related investigative and corrective actions as necessary. The Directive also requires revising the AWL section of the Instructions for Continued Airworthiness. |\n|             | The Directive results from a design review of the fuel tank systems and is issued to prevent electrical energy from lightning, hot shorts or fault current from entering the fuel tank through the MOV actuator shaft, which could result in fuel tank explosions and consequent loss of the aeroplane.           |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n21 April 2008","sortOrder":0},{"sectionNumber":"AD/B737/321","sectionType":"part","heading":"AD/B737/321","content":"## AD/B737/321","sortOrder":1},{"sectionNumber":"Fuel Systems Airworthiness Limitations &","sectionType":"part","heading":"Fuel Systems Airworthiness Limitations & Motor Operated valves","content":"## Fuel Systems Airworthiness Limitations & Motor Operated valves","sortOrder":2},{"sectionNumber":"6/2008","sectionType":"part","heading":"6/2008","content":"## 6/2008","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This is a standard airworthiness directive with a focused, single-purpose scope: addressing a specific fuel system safety defect on specific aircraft models. The scope has not expanded beyond its original safety intent."},"complexity_factors":["Multiple cross-references to external Boeing documents (ASB 737-28A1207, MPD Document D626A001-CMR) that are not reproduced in the directive itself","Conditional compliance pathways: maintenance records review acceptable 'in lieu of' physical inspection; later MPD revisions acceptable if FAA-approved; later ASB revisions acceptable if approved as FAA AMOC","Technical aviation terminology requiring domain knowledge (spar valves, crossfeed valves, airworthiness limitations, AMOC)","Three distinct requirements with different compliance timing (concurrent vs. before further flight vs. 60-month window)","Dual regulatory framework: Australian directive incorporates by reference US FAA AD 2008-06-03 and requires FAA approvals for alternative compliance methods"],"plain_english_summary":"This AD orders operators of specified Boeing 737-600/700/700C/800/900 series aircraft to inspect three motor-operated fuel valves for a known faulty part and, if found, repair or replace them per Boeing instructions, plus update maintenance manuals to add new mandatory fuel-system inspection limits. \n\nIt affects airlines, maintenance engineers and safety managers; the work must be done within 60 months and repairs completed before the aircraft next flies to prevent lightning- or electrical-fault-induced fuel-tank ignition."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"This Directive remains within the original safety-focused purpose set out in the background: to prevent electrical energy from entering fuel tanks via MOV actuator shafts and thereby reduce the risk of fuel tank ignition. It does not broaden the subject matter beyond fuel-system MOVs and airworthiness limitations; it prescribes inspection/correction and a continuing maintenance requirement, consistent with that original intent."},"complexity_factors":["Three distinct mandatory actions (inspection/records review; investigative/corrective work; AWL revision) with differing timing requirements","Cross-reference to Boeing Alert Service Bulletin (ASB 737-28A1207) for detailed inspection and corrective procedures","Cross-reference to Boeing MPD Document D626A001-CMR Section 9 (specific AWL items 28-AWL-21, 28-AWL-22, 28-AWL-24) requiring incorporation into operator documentation","Acceptance of later revisions of the ASB and MPD only if approved as Alternate Method of Compliance (AMOC) or approved by FAA Seattle ACO manager (adds administrative approval path)","Option to use maintenance records in lieu of physical inspection if part number can be conclusively determined (creates a conditional compliance path)","Timing rules: 60 months for inspection, corrective actions before next flight, AWL revision concurrent with inspection (multiple, non-uniform deadlines)","Reference to a parallel FAA AD (FAA AD 2008-06-03) — inter-jurisdictional dependence on foreign regulator documentation"],"plain_english_summary":"**What this instrument does (mechanically)\n\n- Requires operators of certain Boeing 737 series aeroplanes to check three specific motor-operated fuel valves (MOVs) to see if an affected part number is fitted (Requirement 1). A review of the aircraft's maintenance records can be used instead of a physical inspection if the part number is clearly shown in the records.  \n- Requires operators to carry out any investigative and corrective work that the Boeing Alert Service Bulletin (ASB 737-28A1207) specifies if an affected valve is found (Requirement 2). These corrective actions must be done before the aircraft flies again.  \n- Requires the operator to update the aeroplane's Airworthiness Limitations (AWL) in the Instructions for Continued Airworthiness by adding specified fuel-system AWLs from Boeing Maintenance Planning Data (MPD) Document D626A001-CMR Section 9 (Requirement 3). The AWL revision must be done at the same time as the inspection requirement.  \n\nKey compliance timings\n\n- The inspection (Requirement 1) must be completed within 60 months of the Directive's effective date.  \n- Any investigative/corrective actions found during that inspection must be done before the aircraft is next flown (Requirement 2).  \n- The AWL revision must be done at the time the inspection is done (Requirement 3).  \n- Later revisions of the Boeing ASB that have FAA approval as an Alternate Method of Compliance (AMOC) are acceptable for compliance with this Directive.\n\nWhich aeroplanes and parts are affected\n\n- Affects Boeing 737-600, -700, -700C, -800 and -900 series aeroplanes, as identified in Boeing ASB 737-28A1207 (dated 15 February 2007).  \n- The three MOVs named are: left engine fuel shutoff (spar) valve, right engine fuel shutoff (spar) valve, and the fuel crossfeed valve. The Directive applies only if the part numbers match the ‘‘affected’’ part numbers listed in the ASB.\n\nWhy the Directive exists (official rationale and mechanical risk)\n\n- The stated safety concern is that electrical energy (for example from lightning, hot shorts or fault currents) could enter the fuel tank through the MOV actuator shaft. If that occurred, it could ignite fuel vapour in the tank and cause an explosion with loss of the aeroplane. The Directive therefore seeks to remove or modify affected valve actuators and to create continuing airworthiness tasks (AWLs) to prevent recurrence.\n\nPractical effects on operators and maintenance organisations (incentives, costs, and decision points)\n\n- Who pays: aircraft operators (or their maintenance contractors) will bear the cost and downtime of inspections, any required corrective work, and the administrative task of updating maintenance planning documents.  \n- What decisions operators make: whether to perform a physical inspection or rely on maintenance records (records review is allowed if conclusive); how to schedule corrective actions; whether to adopt later ASB revisions approved as AMOCs.  \n- Costs and operational trade-offs: physical inspections and any part replacements/repairs produce direct maintenance costs and possible out-of-service time. Incorporation of AWLs into the MPD establishes ongoing scheduled tasks that increase future maintenance workload and cost.  \n- Implementation dependencies and discretion: the Directive relies on Boeing ASB instructions for the particulars of inspection, investigation and correction, and it permits compliance using later-approved ASB revisions or MPD revisions if approved by the FAA Seattle ACO manager. That creates a dependency on Boeing/FAA documentation and approvals for exact methods of compliance.  \n- Compliance risk and substitution: using maintenance records in place of a physical inspection can reduce aircraft downtime but depends on record completeness. If records are unclear, the operator must inspect. Using AMOCs or later MPD revisions can change the exact procedures but only with FAA-approved documentation.\n\nSummary of mechanics by Directive section\n\n- Requirement 1: Inspect (or review records) for affected MOV part numbers for left/right engine spar shutoff valves and fuel crossfeed valve; compliance within 60 months.  \n- Requirement 2: Perform all related investigative and corrective actions specified in the Boeing ASB before next flight if an affected part is found.  \n- Requirement 3: Revise the AWL section of the Instructions for Continued Airworthiness by incorporating specified fuel-system AWLs from Boeing MPD Document D626A001-CMR Section 9; do this when you do Requirement 1.  \n\nNet effect\n\n- The Directive identifies a specific electrical-fuel-tank ignition pathway, requires confirmation that potentially vulnerable valve actuators are not installed (or are corrected), and imposes permanent AWL entries so the fuel-system configuration and protective measures are maintained as part of ongoing maintenance planning."},"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-b737-321-fuel-systems-airworthiness-limitations-motor-operated-valves","history":"/api/acts/ad-b737-321-fuel-systems-airworthiness-limitations-motor-operated-valves/history","analysis":"/api/acts/ad-b737-321-fuel-systems-airworthiness-limitations-motor-operated-valves/analysis","conflicts":"/api/acts/ad-b737-321-fuel-systems-airworthiness-limitations-motor-operated-valves/conflicts","importantCases":"/api/acts/ad-b737-321-fuel-systems-airworthiness-limitations-motor-operated-valves/important-cases","documents":"/api/acts/ad-b737-321-fuel-systems-airworthiness-limitations-motor-operated-valves/documents"}}