{"id":"F2006B02918","name":"AD/B737/221 - Potable Water Pressure Relief Valve","slug":"ad-b737-221-potable-water-pressure-relief-valve","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42260,"registerId":"commonwealth-F2006B02918-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)  \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 737 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/B737/221 Potable Water Pressure Relie","sectionType":"part","heading":"AD/B737/221 Potable Water Pressure Relief Valve 4/2004","content":"# AD/B737/221 Potable Water Pressure Relief Valve 4/2004\n\nApplicability: Model 737-100, \\-200, \\-200C, \\-300, \\-400, and \\-500 series aeroplanes; line numbers 1\n\nthrough 2696 inclusive.\n\nRequirement: 1. For those aeroplanes listed in the effectivity section of Boeing Service Bulletin (S/B)737-38-1029, Revision 1, dated August 19, 1993, on which the modification of the potable water pressurization system specified in the service bulletin has not been accomplished:\n\n    Modify the potable water pressurization system; in accordance with Boeing S/B 737-38-1029, dated June 6, 1991; or Revision 1 dated 19 August 1993 except for the following:\n\n    i Do not reinstall the existing pressure relief valve having part number (P/N) 520A6DB50.\n\n    ii Do not perform the leak test procedures specified in the referenced service bulletin.\n\n    b. Install a new pressure relief valve having P/N RV05-362, in accordance with Boeing S/B 737-38A1047, Revision 2, dated July 18, 2002 or earlier revisions.\n\n    2. For those aeroplanes listed in the effectivity section of Boeing S/B 737-38-1029, or Revision 1; on which the modification of the potable water pressurization system specified in that service bulletin has been accomplished: remove the existing pressure relief valve from the potable water tank, and replace the valve with a new pressure relief valve having P/N RV05-362; in accordance with Boeing S/B 737-38A1047 Revision 2 or earlier revisions.\n\n    3. For all other aeroplanes having line numbers 1 through 2523 inclusive: remove the existing pressure relief valve from the potable water tank, and replace the valve with a new pressure relief valve having P/N RV05-362, in accordance with Boeing S/B 737-38A1047, Revision 2 or earlier revisions.","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD confines its effect to the Boeing 737 models and line‑number ranges stated and to actions on the potable water pressure relief valve/modification per the cited Boeing Service Bulletins. It does not broaden the affected models, systems, or tasks beyond those specified in the Applicability and Requirement sections."},"complexity_factors":["Multiple aircraft groups split by prior modification status (Requirement 1 applies where modification not done; Requirement 2 where it has been done; Requirement 3 for other line‑numbers).","Several Boeing Service Bulletins and specific revision dates are referenced (S/B 737‑38‑1029 original and Rev 1; S/B 737‑38A1047 Rev 2 or earlier), creating version‑selection choices for compliance.","Explicit prohibitions (do not reinstall P/N 520A6DB50; do not perform the leak test in the referenced SB) which alter standard maintenance steps and may cause operational interpretation questions.","Applicability is limited to specific model variants and line‑number ranges (Models 737‑100/‑200/‑200C/‑300/‑400/‑500; line numbers 1–2696 or 1–2523), requiring operators to determine exact eligibility.","Technical installation work and parts replacement obligations fall on operators/maintenance organisations and require sourcing the specified replacement valve (P/N RV05‑362)."],"plain_english_summary":"This AD requires operators of early Boeing 737 models (specified line numbers) to modify the potable‑water pressurisation system or remove the existing potable‑water pressure relief valve and install a replacement valve P/N RV05‑362. It prohibits reinstalling the old valve P/N 520A6DB50 and omits the leak test called for in the earlier Boeing service bulletin. Affected operators and maintenance organisations must follow the Boeing Service Bulletins referenced to correct the unsafe condition in the potable water system."},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope — addressing a specific unsafe condition in the potable water pressurization system of Boeing 737 aircraft. The three-tiered requirement structure reflects different aircraft modification histories rather than scope creep. The directive remains tightly focused on the pressure relief valve replacement issue."},"complexity_factors":["Three distinct compliance pathways depending on prior modification status (Group 1, Group 2, Group 3)","Multiple cross-references to Boeing Service Bulletins (S/B 737-38-1029 and S/B 737-38A1047) with specific revision dates","Specific part numbers (P/N 520A6DB50 and RV05-362) that must be tracked","Nested exceptions within Requirement 1 (two specific prohibitions on reinstalling old valve and skipping leak tests)","Line number ranges (1-2696, 1-2523) create overlapping but distinct applicability groups","Technical aviation terminology throughout (effectivity sections, service bulletins, line numbers)"],"plain_english_summary":"This Airworthiness Directive mandates replacing an unsafe potable-water pressure relief valve on certain Boeing 737-100 through -500 aeroplanes (built up to line 2696). Operators must fit the approved replacement valve to prevent tank over-pressurization and potential rupture.\n\nIt’s a compulsory safety action for affected operators — aircraft may not fly legally until the required valve replacement and associated modifications are completed."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-221-potable-water-pressure-relief-valve","history":"/api/acts/ad-b737-221-potable-water-pressure-relief-valve/history","analysis":"/api/acts/ad-b737-221-potable-water-pressure-relief-valve/analysis","conflicts":"/api/acts/ad-b737-221-potable-water-pressure-relief-valve/conflicts","importantCases":"/api/acts/ad-b737-221-potable-water-pressure-relief-valve/important-cases","documents":"/api/acts/ad-b737-221-potable-water-pressure-relief-valve/documents"}}