{"id":"F2006B02820","name":"AD/B737/118 - Standby Hydraulic System - Hydraulic Fuse Operation","slug":"ad-b737-118-standby-hydraulic-system-hydraulic-fuse-operation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42162,"registerId":"commonwealth-F2006B02820-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/118 - Standby Hydraulic System - Hydraulic Fuse Operation","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/B737/118 Standby Hydraulic System \\- Hydraulic\n\nFuse Operation\n\n  \n7/98\n\nApplicability: Model 737-300, 400 & 500 series aeroplanes having line numbers 1001 through 2791 (inclusive).\n\nRequirement: 1. For aeroplanes listed in Boeing Service Bulletin 737-29-1070 dated 8 June 1995, interchange the location of the hydraulic fuse and the flow limiter of the standby hydraulic system of the leading edge so that the hydraulic fuse is positioned upstream of the flow limiter in accordance with Boeing Service Bulletin 737-29- 1070 dated 8 June 1998.\n\n2. For aeroplanes listed in Boeing Service Bulletin 737-29-1071 dated 16 May 1996, replace the existing hydraulic fuses in the standby hydraulic system with new fuses that are not adversely affected during low temperature operation, in accordance with Boeing Service Bulletin 737-29-1071 dated 16 May 1996.\n\nNote: FAA AD 98-07-16 Amdt 39-10436 dated 7 May 1998 refers.\n\nCompliance: 1. Within 18 months or 4000 flight hours after the effective date of this Directive whichever is the later.\n\n2. Within 18 months or 4000 flight hours after the effective date of this Directive, whichever is the later.\n\nThis airworthiness directive becomes effective on 18 June 1998.\n\nBackground: Tests have shown that the standby hydraulic system is designed such that possible adverse operation of the hydraulic fuses could result in the loss of all standby hydraulic system pressure and consequent severely reduced controllability of the aeroplane during certain flight phases. This AD mandates the incorporation of two Boeing Service Bulletins which correct this situation.","sortOrder":0}],"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":2,"scope_assessment":{"changed":false,"description":"This is a standard Airworthiness Directive (AD) with focused, original scope. It addresses a specific safety-critical hydraulic system defect in defined aircraft models without expansion into unrelated systems or aircraft types."},"complexity_factors":["Single, specific technical subject matter (hydraulic fuse replacement/repositioning)","Only 2 defined applicability criteria (aircraft model range and line numbers)","Two straightforward compliance requirements with identical timeframes","Minimal cross-referencing (only references 2 Boeing Service Bulletins and 1 FAA AD)","No nested exceptions or conditional logic","Short document (approximately 250 words)","Clear, unambiguous operative language ('interchange', 'replace')"],"plain_english_summary":"This safety order requires operators of certain Boeing 737-300/400/500 aircraft (S/N 1001–2791) to correct a cold-weather failure risk in the backup hydraulic system that could lead to loss of control.  \n\nBoeing’s service instructions mandate two technical fixes — repositioning components and installing cold-rated hydraulic fuses — within the specified compliance window to restore reliable backup hydraulics."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive enforces corrective actions described in two Boeing service bulletins for the specified 737-300/400/500 line numbers to address standby hydraulic fuse behaviour. The text does not expand or narrow applicability beyond those listed aeroplanes and the stated corrective measures."},"complexity_factors":["Safety‑critical hardware change affecting flight control hydraulics","Two distinct physical modifications: interchange of components and replacement with low‑temperature parts","Requirement tied to specific models and a defined range of line numbers","Mandated compliance window (18 months or 4,000 flight hours)","Dependence on manufacturer Boeing Service Bulletins for procedural and parts specifications","Potential operational disruption during modifications and need to source approved parts","Cross-reference to an FAA Airworthiness Directive"],"plain_english_summary":"Requires relocating the standby hydraulic fuse ahead of the flow limiter and replacing standby hydraulic fuses with parts tolerant of low‑temperature operation on certain Boeing 737-300/400/500 aeroplanes, following two Boeing service bulletins. Affects operators of the listed line‑number aeroplanes; it responds to test results showing that fuse malfunction could cause loss of standby hydraulic pressure and reduced controllability. Compliance is mandated within 18 months or 4,000 flight hours."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-118-standby-hydraulic-system-hydraulic-fuse-operation","history":"/api/acts/ad-b737-118-standby-hydraulic-system-hydraulic-fuse-operation/history","analysis":"/api/acts/ad-b737-118-standby-hydraulic-system-hydraulic-fuse-operation/analysis","conflicts":"/api/acts/ad-b737-118-standby-hydraulic-system-hydraulic-fuse-operation/conflicts","importantCases":"/api/acts/ad-b737-118-standby-hydraulic-system-hydraulic-fuse-operation/important-cases","documents":"/api/acts/ad-b737-118-standby-hydraulic-system-hydraulic-fuse-operation/documents"}}