{"id":"F2006B09723","name":"AD/F27/156 - Fuel Tank Isolation Valve Selector Knobs","slug":"ad-f27-156-fuel-tank-isolation-valve-selector-knobs","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115906,"registerId":"commonwealth-F2006B09723-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# ![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\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\nFokker F27 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/F27/156 Fuel Tank Isolation Valve Sel","sectionType":"part","heading":"AD/F27/156 Fuel Tank Isolation Valve Selector Knobs 8/2004","content":"# AD/F27/156 Fuel Tank Isolation Valve Selector Knobs 8/2004\n\nDM\n\nApplicability: Model F.27 Mk.200, Mk.400, Mk.500 and Mk.600 aeroplanes, serial numbers 10505 through 10591, that are not equipped with inboard wing fuel tanks and that have not been modified in accordance with Fokker Services Service Bulletin (SB) F27/28-58.\n\nRequirement: 1. Check for the presence of a correctly installed sealwire (lockwire) between the two Fuel Tank Isolation Valve Selector Knobs and, if necessary, correct any deficiency in the installation in accordance with Part 2 - Accomplishment Instructions of Fokker Services SB F27/28-67 dated 23 February 2004.\n\n    2. Modify spare Fuel Tank Isolation Valve Selector Knobs part numbers (P/N) E16032-3, 10632-10003 and P80-004 in accordance with Part 2 - Accomplishment Instructions of SB F27/28-67 and re-identify the knobs as P/N Y000092-401.\n\n    3. Incorporate the applicable changes introduced with Fokker Services Manual Change Notification - Operation Documentation MCNO F27-018 dated 1 December 2003 in to the applicable Aircraft Flight Manual (AFM).\n\n    4. Incorporate the applicable changes introduced with Fokker Services Manual Change Notification \\- Maintenance Documentation MCNM F27-020 dated 23 February 2004 into the Maintenance Manual.\n\nNote : CAA-NL AD 2004-037 (A) Corr refers.\n\nCompliance: For Requirement 1 \\- Within the next three calendar months after the effective date of this Directive.\n\nFor Requirement 2 \\- Before installation as a replacement part.\n\nFor Requirement 3 \\- Within the next calendar month after the effective date of this Directive.\n\nFor Requirement 4 \\- Within the next three calendar months after the effective date of this Directive.\n\nThis Airworthiness Directive becomes effective on 16 June 2004.","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD targets a defined subset of Fokker F.27 aircraft (serials 10505–10591 without inboard tanks and not modified per SB F27/28-58) and prescribes inspections, modifications and manual updates. The instrument's scope as written is focused and consistent with addressing the stated unsafe condition; the text gives no indication the scope departs from that intent."},"complexity_factors":["Narrow applicability: limited to specific F.27 models and serial numbers and only aircraft without inboard wing tanks","Multiple discrete actions: inspection/rectification, spare-part modification/re-identification, AFM and Maintenance Manual updates","Dependence on external service documents: requires compliance with Fokker Services SB F27/28-67 and Manual Change Notifications","Staggered compliance deadlines: different timeframes for inspection (3 months), AFM update (1 month), manual update (3 months), and parts-before-installation rule","Logistics burden for operators: control of spare inventory and modification of spares before installation","Safety-critical component: fuel system selector knobs require correct installation and lockwiring, raising compliance and verification importance"],"plain_english_summary":"This AD requires operators of specific Fokker F.27 Mk.200/400/500/600 aircraft (certain serial numbers without inboard wing tanks) to inspect and, if needed, secure fuel tank isolation valve selector knobs with sealwire, modify specified spare knobs and re‑identify them, and incorporate related changes into the Aircraft Flight Manual and Maintenance Manual. CASA issued the directive to correct an unsafe condition; operators must pay for inspections, parts modification and paperwork changes and must comply within the deadlines set in the AD."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard, narrowly-scoped airworthiness directive addressing a specific technical defect in a specific aircraft type. The scope remains tightly focused on the fuel tank isolation valve selector knob issue as originally identified."},"complexity_factors":["Multiple applicability conditions combined with 'and/or' logic (four conditions: specific models, serial number range, absence of inboard tanks, absence of prior modification)","Four distinct requirements with different compliance timeframes (1 month vs 3 months vs 'before installation')","Cross-references to external technical documents (Fokker Service Bulletins and Manual Change Notifications) that are not reproduced in the directive itself","Specific part numbers and document dates that must be precisely matched","Reference to foreign aviation authority directive (CAA-NL AD 2004-037) for additional context"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of specified Fokker F27 Mk.200/400/500/600 (S/N 10505–10591) without inboard tanks and not already modified under SB F27/28‑58 to secure the fuel-tank isolation valve selector knobs with safety (lock) wire to prevent inadvertent movement. It also mandates modification/labeling of spare knobs before installation and updates to the Aircraft Flight Manual (operating note) and maintenance manual — short compliance timelines to prevent fuel-system mismanagement."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f27-156-fuel-tank-isolation-valve-selector-knobs","history":"/api/acts/ad-f27-156-fuel-tank-isolation-valve-selector-knobs/history","analysis":"/api/acts/ad-f27-156-fuel-tank-isolation-valve-selector-knobs/analysis","conflicts":"/api/acts/ad-f27-156-fuel-tank-isolation-valve-selector-knobs/conflicts","importantCases":"/api/acts/ad-f27-156-fuel-tank-isolation-valve-selector-knobs/important-cases","documents":"/api/acts/ad-f27-156-fuel-tank-isolation-valve-selector-knobs/documents"}}