{"id":"F2008L04604","name":"AD/B737/350 - Auxiliary Fuel Tanks","slug":"ad-b737-350-auxiliary-fuel-tanks","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":120945,"registerId":"commonwealth-F2008L04604-current","compilationNumber":null,"startDate":"2026-04-03","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/B737/350 | Auxiliary Fuel Tanks | 1/2009 |\n| ----------- | -------------------- | ------ |\n\n```html\n

Applicability:

This AD applies to the following aeroplanes fitted with the Auxiliary tank STC(s) listed in Table 1 of this AD.

Table 1

Aeroplanes

Auxiliary tank STC(s)

Boeing Model 737-200 series aeroplanes

SA83NE, SA725NE (unless installed with SA725NE-D, Configuration 7), SA1078NE, SA1265EA

Boeing Model 737-200C series aeroplanes

SA725NE (unless installed with
SA725NE-D, Configuration 7)

Boeing Model 737-300 series aeroplanes

SA500NE, SA542NE, SA553NE, SA714NE, SA725NE (unless installed with
SA725NE-D, Configuration 7)

Boeing Model 737-400 series aeroplanes

SA553NE, SA725NE (unless installed with SA725NE-D, Configuration 7)

Boeing Model 737-500 series aeroplanes

SA725NE (unless installed with
SA725NE-D, Configuration 7), ST00040NY, ST01337NY

Boeing Model 737-700 series aeroplanes (increased gross weight)

ST00936NY-D (unless installed with Configuration 3), ST01650NY-D

Boeing Model 737-800 series aeroplanes

ST01384NY, ST01384NY-D

Requirement:

1. Submit a report to the Manager, Systems and New Technologies, Airworthiness Engineering Group CASA, Fax (02) 6217 1914.

The report must include the following information:

(a) The aeroplane registration and auxiliary tank STC number installed.

\n```\n\n| | (b) The usage frequency in terms of total number of flights per year and total number of flights per year for which the auxiliary tank is used.2. Deactivate the auxiliary fuel tanks, in accordance with a deactivation procedure approved by CASA. Any auxiliary tank component that remains on the aeroplane must be secured and must have no effect on the continued operational safety and airworthiness of the aeroplane. Deactivation must not result in the need for additional instructions for continued airworthiness.Note 1: Appendix A of this AD provides criteria that should be included in the deactivation procedure. The proposed deactivation procedures should be submitted to the Manager, Systems and New Technologies, as soon as possible to ensure timely review and approval.Note 2: FAA AD 2008-22-01 Amdt 39-15696 dated 9 October 2008 refers. |\n| ----------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Compliance: | For Requirement 1 - Within 45 days after the effective date of this AD.For Requirement 2 - Before 16 December 2009. |\n| | This Airworthiness Directive becomes effective on 15 January 2009. |\n| Background: | This AD requires deactivation of PATS Aircraft, LLC, auxiliary fuel tanks. This AD results from fuel system reviews conducted by the manufacturer, which identified unsafe conditions for which the manufacturer has not provided corrective actions. The issuing of this AD is intended to prevent the potential of ignition sources inside fuel tanks, which, in combination with flammable fuel vapours, 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\n27 November 2008\n\n| AD/B737/350Appendix A | Auxiliary Fuel Tanks | 1/2009 |\n| --------------------- | -------------------- | ------ |\n\nDeactivation Criteria\n\nThe auxiliary fuel tank deactivation procedure as detailed in Requirement 2 of this AD should address the following actions.\n\n1. Permanently drain auxiliary fuel tanks, and clear them of fuel vapours to eliminate the possibility of out-gassing of fuel vapours from the emptied auxiliary tank.\n\n2. Disconnect all electrical connections from the fuel quantity indication system (FQIS), fuel pumps if applicable, float switches, and all other electrical connections required for auxiliary tank operation, and stow them at the auxiliary tank interface.\n\n3. Disconnect all pneumatic connections if applicable, cap them at the pneumatic source, and secure them.\n\n4. Disconnect all fuel feed and fuel vent plumbing interfaces with aeroplane original equipment manufacturer (OEM) tanks, cap them at the aeroplane tank side, and secure them in accordance with a method approved by CASA; one approved method is specified in AC 25-8 Auxiliary Fuel System Installations. In order to eliminate the possibility of structural deformation during cabin decompression, leave open and secure the disconnected auxiliary fuel tank vent lines.\n\n5. Pull and collar all circuit breakers used to operate the auxiliary tank.\n\n6. Revise the weight and balance document, if required, and obtain CASA approval.\n\n7. Amend the applicable sections of the applicable aeroplane flight manual (AFM) to indicate that the auxiliary fuel tank is deactivated. Remove auxiliary fuel tank operating procedures to ensure that only the OEM fuel system operational procedures are contained in the AFM. Amend the Limitations Section of the AFM to indicate that the AFM Supplement for the STC is not in effect. Place a placard in the flight deck indicating that the auxiliary tank is deactivated. The AFM revisions specified in this paragraph may be accomplished by inserting a copy of this AD into the AFM.\n\n8. Amend the applicable sections of the applicable aeroplane maintenance manual to remove auxiliary tank maintenance procedures.\n\n9. After the auxiliary fuel tank is deactivated, accomplish procedures such as leak checks and pressure checks deemed necessary before returning the aeroplane to service. These procedures must include verification that the aeroplane FQIS and fuel distribution systems have not been adversely affected.\n\n10. Revise the instructions for continued airworthiness, as required, after deactivation.\n\n11. Include with the operator's proposed procedures any relevant information or additional steps that are deemed necessary by the operator to comply with the deactivation and return the aeroplane to service.","sortOrder":0},{"sectionNumber":"AD/B737/350","sectionType":"part","heading":"AD/B737/350","content":"## AD/B737/350","sortOrder":1},{"sectionNumber":"Auxiliary Fuel Tanks","sectionType":"part","heading":"Auxiliary Fuel Tanks","content":"## Auxiliary Fuel Tanks","sortOrder":2},{"sectionNumber":"1/2009","sectionType":"part","heading":"1/2009","content":"## 1/2009","sortOrder":3},{"sectionNumber":"AD/B737/350Appendix A","sectionType":"part","heading":"AD/B737/350Appendix A","content":"## AD/B737/350 \nAppendix A","sortOrder":4}],"analysis":{"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":4,"scope_assessment":{"changed":false,"description":"This is a discrete safety directive addressing a specific identified hazard. The scope remains tightly focused on deactivation of PATS auxiliary fuel tanks in Boeing 737 series aircraft. The detailed deactivation criteria in Appendix A are integral to the core safety purpose rather than scope creep."},"complexity_factors":["Multiple nested exceptions in applicability (e.g., 'unless installed with SA725NE-D, Configuration 7')","Cross-reference to FAA AD 2008-22-01 for additional context","Detailed technical deactivation procedure with 11 specific criteria in Appendix A","Requirement for CASA approval of deactivation procedures and weight/balance revisions","Reference to external document AC 25-8 for approved methods","Dual compliance deadlines (45 days for reporting, fixed date for deactivation)","Multiple document amendments required (AFM, maintenance manual, instructions for continued airworthiness)"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of certain Boeing 737 models with PATS Aircraft auxiliary fuel tanks (installed via specific STCs) to report affected aircraft within 45 days and permanently deactivate the tanks by 16 December 2009 using a CASA-approved procedure. The action—draining, disconnecting, securing/removing components, updating manuals/records, and placarding—responds to identified ignition risks in the tanks that could allow fuel-vapour explosions and endanger flight safety."},"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":false,"description":"The AD focuses on PATS auxiliary fuel tanks identified by specific STCs and requires reporting plus deactivation to address fuel‑system safety issues identified by the manufacturer. That targeted approach aligns with the stated background (manufacturer fuel system reviews) and the Applicability/Requirement provisions; it does not expand obligations beyond the listed STCs and the technical deactivation and paperwork changes set out in Appendix A (Background; Applicability; Requirement 2; Appendix A)."},"complexity_factors":["Applicability spans many 737 variants and multiple STCs, so identifying affected aeroplanes requires cross‑checking Table 1 (Applicability / Table 1).","Two distinct mandatory actions with different deadlines: reporting within 45 days and deactivation by 16 December 2009 (Requirement 1; Requirement 2; Compliance).","Deactivation requires CASA approval of the operator's procedure and submission to the Manager, Systems and New Technologies, creating administrative interaction and discretionary review (Requirement 2; Applicability).","Appendix A prescribes detailed technical steps (draining vapours, disconnecting electrics/pneumatics/fuel plumbing, sealing vents) that impose engineering and maintenance work (Appendix A, items 1–5).","Operational and airworthiness paperwork changes are required: AFM, AFM Supplement removal/placarding, maintenance manual and instructions for continued airworthiness, and possible weight & balance revisions (Appendix A, items 6–10).","Return‑to‑service checks (leak/pressure checks, verification of FQIS and fuel distribution) create testing and inspection obligations (Appendix A, item 9).","Cross‑jurisdictional reference to FAA AD 2008‑22‑01 implies coordination with existing foreign directives (Background, Note 2)."],"plain_english_summary":"This Airworthiness Directive covers Boeing 737 aeroplanes fitted with the PATS auxiliary fuel‑tank STCs listed in Table 1. It requires operators to (a) report aeroplane registration and tank usage to the Manager, Systems and New Technologies, CASA within 45 days, and (b) deactivate the auxiliary tanks under a CASA‑approved procedure before 16 December 2009 (Requirements 1–2; Applicability; Compliance). Operators pay compliance costs and must amend manuals and weight/balance records as set out in Appendix A."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-350-auxiliary-fuel-tanks","history":"/api/acts/ad-b737-350-auxiliary-fuel-tanks/history","analysis":"/api/acts/ad-b737-350-auxiliary-fuel-tanks/analysis","conflicts":"/api/acts/ad-b737-350-auxiliary-fuel-tanks/conflicts","importantCases":"/api/acts/ad-b737-350-auxiliary-fuel-tanks/important-cases","documents":"/api/acts/ad-b737-350-auxiliary-fuel-tanks/documents"}}