{"id":"F2006L02525","name":"AD/B737/291 - Auxiliary Fuel Tank Float Switch","slug":"ad-b737-291-auxiliary-fuel-tank-float-switch","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":59766,"registerId":"commonwealth-F2006L02525-current","compilationNumber":null,"startDate":"2026-04-02","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/B737/291 | Auxiliary Fuel Tank Float Switch | 9/2006 |\n| ----------- | -------------------------------- | ------ |\n\n| Applicability: | Model 737-200, -300, and -400 series aeroplanes, equipped with auxiliary fuel tanks.                                                                                                                                                                                                                                               |\n| -------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Replace the existing fuelling float switch in the auxiliary fuel tank with a new, improved fuelling float switch, install a new liner system inside the float switch conduit in accordance with Part A of the Accomplishment Instructions of Boeing Service Bulletin (SB) 737-28A1192, Revision 2, dated 27 April 2006.         |\n|                | Note 1: This Directive does not require doing the actions in Part B of the Accomplishment Instructions of Boeing Service Bulletin 737- 28A1192, Revision 2.                                                                                                                                                                        |\n|                | Replacements and conduit liner system installations accomplished before the effective date of this Directive in accordance with Boeing Alert Service Bulletin 737-28A1192, dated 27 March 2003; or Boeing SB 737-28A1192, Revision 1, dated 21 August 2003; are acceptable for compliance with the requirements of this Directive. |\n|                | 2. Fuelling float switch part number (P/N) F8300-146 may not be installed on the auxiliary fuel tank of any aeroplane as a replacement spare.                                                                                                                                                                                      |\n|                | Note 2: FAA AD 2006-15-05 Amdt 39-14685 refers.                                                                                                                                                                                                                                                                                    |\n| Compliance:    | For Requirement 1 - Within 24 months after the effective date of this Directive.                                                                                                                                                                                                                                                   |\n|                | For Requirement 2 - As of the effective date of this Directive.                                                                                                                                                                                                                                                                    |\n|                | This Airworthiness Directive becomes effective on 31 August 2006.                                                                                                                                                                                                                                                                  |\n\n| Background: | The United States Federal Aviation Administration (FAA) has received reports of chafing of the direct-current-powered float switch wiring insulation in the centre fuel tank. This Directive requires actions designed to prevent contamination of the fuelling float switch of the auxiliary fuel tank by moisture or fuel, together with chafing of the float switch wiring against the float switch conduit in the fuel tank, which could present an ignition source inside the fuel tank that could cause a fire or explosion. |\n| ----------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n21 July 2006","sortOrder":0},{"sectionNumber":"AD/B737/291","sectionType":"part","heading":"AD/B737/291","content":"## AD/B737/291","sortOrder":1},{"sectionNumber":"Auxiliary Fuel Tank Float Switch","sectionType":"part","heading":"Auxiliary Fuel Tank Float Switch","content":"## Auxiliary Fuel Tank Float Switch","sortOrder":2},{"sectionNumber":"9/2006","sectionType":"part","heading":"9/2006","content":"## 9/2006","sortOrder":3}],"analysis":{"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"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"Scope remains narrowly focused on preventing contamination/chafing of the auxiliary fuel-tank fuelling float switch for Boeing 737-200/300/400 aircraft with auxiliary tanks. The Directive updates required hardware and installation method (per SB Rev 2), accepts earlier compliant work, and adds an immediate ban on a specific spare P/N; it does not broaden the class of affected aircraft or add new risk categories beyond the float-switch ignition concern."},"complexity_factors":["Technical requirement: replacement of a fuel-tank float switch and installation of an internal conduit liner (requires specialised maintenance work).","Limited applicability: only Boeing 737-200/300/400 series with auxiliary fuel tanks (narrows affected population but concentrates technical demand).","Service bulletin cross-references: mandates compliance with a specific Boeing SB revision and accepts prior SB versions as alternative compliance paths.","Two-tier compliance timing: 24-month window to complete retrofit versus immediate prohibition on installing specified spare P/N F8300-146.","Parts-control and logistics burden: operators must track and prevent use of a banned spare part number.","Safety-critical context: maintenance must meet airworthiness standards and likely requires certified maintenance organisations and documentation.","Low administrative discretion: the AD prescribes actions and timing rather than delegating broad regulatory choice, but implementation scheduling is left to operators."],"plain_english_summary":"Requires replacement of the auxiliary fuel-tank fuelling float switch and installation of a conduit liner per Boeing Service Bulletin 737-28A1192 Revision 2, and bans use of float switch P/N F8300-146 as a replacement spare. Applies to Boeing 737-200, -300 and -400 series aircraft fitted with auxiliary tanks. The measure aims to prevent wiring chafing and contamination that could create an ignition source in the tank. Operators must complete the replacement within 24 months and meet the immediate spare-part prohibition."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific wiring safety defect in auxiliary fuel tanks of particular Boeing 737 models. The scope has not expanded beyond this targeted safety fix."},"complexity_factors":["Single technical requirement with clear mechanical action (replace switch, install liner)","Only 2 substantive requirements with straightforward compliance dates","Limited applicability (3 specific aircraft models with auxiliary tanks only)","References external technical document (Boeing Service Bulletin) but provides specific revision and date","Contains one explicit exemption (Part B of Service Bulletin not required)","Grandfathering clause for prior compliant work is clearly stated","No nested definitions, conditional logic, or cross-references to other legislation"],"plain_english_summary":"This CASA Airworthiness Directive requires operators of Boeing 737‑200/‑300/‑400 aircraft fitted with auxiliary fuel tanks to replace the existing fuel‑tank float switch with an improved unit and fit a wiring protective liner, and immediately prohibits use of spare part F8300‑146. It addresses chafing of fuel‑tank wiring that can expose conductors to moisture or fuel and create a spark/fire hazard; the replacement must be completed within two years."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-291-auxiliary-fuel-tank-float-switch","history":"/api/acts/ad-b737-291-auxiliary-fuel-tank-float-switch/history","analysis":"/api/acts/ad-b737-291-auxiliary-fuel-tank-float-switch/analysis","conflicts":"/api/acts/ad-b737-291-auxiliary-fuel-tank-float-switch/conflicts","importantCases":"/api/acts/ad-b737-291-auxiliary-fuel-tank-float-switch/important-cases","documents":"/api/acts/ad-b737-291-auxiliary-fuel-tank-float-switch/documents"}}