{"id":"F2006B02852","name":"AD/B737/15 Amdt 3 - Fuel Boost Pump Bypass Valve","slug":"ad-b737-15-amdt-3-fuel-boost-pump-bypass-valve","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42194,"registerId":"commonwealth-F2006B02852-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/15 Amdt 3 - Fuel Boost Pump Bypass Valve","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nBoeing 737 Series Aeroplanes\n\nAD/B737/15\n\nAmdt 3\n\n  \nFuel Boost Pump Bypass Valve 11/90\n\nApplicability: Model 737 series aeroplanes listed in Boeing Service Bulletin 737-28A1072 Revision 4.\n\nRequirement: 1. Action in accordance with Part I of Boeing Service Bulletin 737-28A1072 Revision 4.\n\n    2. Unless already modified in accordance with Part II of Boeing Service Bulletin 737-28A1072 Revision 2 or 3, action in accordance with Part II of Boeing Service Bulletin 737-28A1072 Revision 4.\n\n    3. For those aircraft which exhibited bracket preload when previously modified in accordance with Boeing Service Bulletin 737-28A1072 Revision 2 or 3; unless already accomplished, conduct an inspection of the suction feed bypass system for preloading in accordance with Boeing Service Bulletin 737-28A1072 Revision 4.\n\nNote: FAA AD 90-15-17 Amdt 39-6673 refers.\n\nCompliance: 1. At each maintenance interval coinciding with approximately 300 hrs time in service, until improved bypass valves are installed in accordance with Requirement 2.\n\n    2. Prior to 31 March 1992.\n\n    3. Prior to 31 March 1992.\n\nBackground: The manufacturer has determined that two separate incidents of engine flame out during cruise conditions was caused by small accumulations of water freezing in the Fuel Boost Pump Bypass Valve, and preventing fuel flow to the engine while on suction feed. Amendment 3 is raised in response to a revision of the country of origin AD which required modification of those aircraft not previously modified and an inspection for bracket preload for aircraft modified prior to Revision 4 of the Service Bulletin.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Amendment 3 broadened the AD to require modification of aircraft not previously modified and added an inspection for bracket preload on aircraft modified under earlier revisions. (See Requirements 2 and 3 and Background: amendment raised in response to a revision of the country of origin AD.)"},"complexity_factors":["Cross-reference to an external manufacturer document: Boeing Service Bulletin 737-28A1072 (Requirements 1–3)","Multiple conditional requirements depending on prior compliance with earlier SB revisions (Requirement 2 and 3)","Recurring inspection obligation tied to maintenance intervals (~300 hrs) until modification is done (Compliance 1)","Fixed calendar compliance deadlines for modifications and inspections (Compliance 2 and 3: prior to 31 March 1992)","Technical diagnosis and targeted inspection (bracket preload) limited to a subset of aircraft (Requirement 3 and Background)","Coordination implied with foreign authority action (Note referencing FAA AD)"],"plain_english_summary":"This AD requires operators of the Boeing 737 models listed in Boeing Service Bulletin 737-28A1072 to fit improved fuel boost pump bypass valves, perform interim suction-feed checks about every 300 flight hours until the fix is fitted, and inspect for bracket preload on aircraft modified under earlier revisions. CASA enforces compliance; aircraft operators and their maintenance organisations pay for and schedule the inspections and modifications. The action responds to two flameouts traced to ice-blocked bypass valves (Background)."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is Amendment 3 to an existing Airworthiness Directive. The amendments expand the original directive to cover aircraft modified under earlier revisions of the Service Bulletin (adding the bracket preload inspection) and incorporate updated technical instructions from the manufacturer. This represents normal iterative refinement of aviation safety requirements rather than scope creep beyond the original safety purpose of preventing fuel system icing."},"complexity_factors":["Short, single-purpose document (1 page)","Only 3 defined compliance requirements with clear deadlines","Minimal cross-referencing (one FAA AD reference, one Boeing Service Bulletin referenced multiple times)","Technical aviation terminology requires industry knowledge but is standard for the field","Conditional logic limited to simple 'unless already modified' exceptions","No nested definitions or interpretive sections"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspections and fixes to address ice formation in Boeing 737 fuel boost pump bypass valves that can block fuel flow and cause in‑flight engine flameouts. It affects owners, operators and maintenance personnel of the 737s covered by Boeing Service Bulletin 737‑28A1072 Rev 4. Operators must perform repeated inspections (~300 flight‑hour intervals) until a required permanent valve modification is installed (and a bracket‑preload check done where earlier mods were used) to eliminate the hazard."},"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-b737-15-amdt-3-fuel-boost-pump-bypass-valve","history":"/api/acts/ad-b737-15-amdt-3-fuel-boost-pump-bypass-valve/history","analysis":"/api/acts/ad-b737-15-amdt-3-fuel-boost-pump-bypass-valve/analysis","conflicts":"/api/acts/ad-b737-15-amdt-3-fuel-boost-pump-bypass-valve/conflicts","importantCases":"/api/acts/ad-b737-15-amdt-3-fuel-boost-pump-bypass-valve/important-cases","documents":"/api/acts/ad-b737-15-amdt-3-fuel-boost-pump-bypass-valve/documents"}}