{"id":"F2006B02962","name":"AD/B737/62 Amdt 1 - Main Fuel Tank Float Switch Electrical Harness","slug":"ad-b737-62-amdt-1-main-fuel-tank-float-switch-electrical-harness","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42304,"registerId":"commonwealth-F2006B02962-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/62 Amdt 1 - Main Fuel Tank Float Switch Electrical Harness","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/B737/62\n\nAmdt 1\n\n  \nMain Fuel Tank Float Switch Electrical Harness 2/94\n\nApplicability: All model 737 series aeroplanes identified in Boeing Service Letters 737-SL-28-36 and 737-SL-28-42 dated 30 November 1990 and 15 December 1992 respectively.\n\nRequirement: 1. For aircraft identified in Service Letter 737-SL-28-36 inspect the wing main tank float switch electrical conduit for fuel leaks and condensation build up in accordance with the Service Letter 737-SL-28-36. If evidence of fuel leakage or water condensation is found then, before the next flight, purge and install a new vapour seal assembly in accordance with the Service Letter.\n\n    2. For aircraft identified in Service Letter 737-SL-28-42 inspect the wing main tank float switch electrical conduit for fuel leaks and condensation build up in accordance with the Service Letter 737-SL-28-36. If evidence of fuel leakage or water condensation is found then, before the next flight, purge and install a new vapour seal assembly in accordance with Service Letter 737-SL-28-36.\n\n    3. Fill the interior of the wing main tank float switch electrical conduits with grease in accordance with either:\n\n    Boeing Service Letter 737-SL-28-42 dated 15 December 1992,\n\n    b. Boeing Service Letter 737-SL-28-42A dated 15 July 1993; or\n\n    c. Ansett Airlines Engineering Release B73-28-10-6B.\n\nNote: FAA AD 93-17-02 Amdt 39-8672 refers.\n\nCompliance: 1 \\- The Compliance was originally prior to 7 February 1992, and thereafter at intervals not exceeding 1500 hours time in service.\n\nThis amendment is effective from 3 February 1994 and thereafter at intervals not exceeding 1500 hours time in service.\n\n    2 \\- Prior to 1 April 1994 and thereafter at intervals not exceeding 1500 hours time in service.\n\n    3 \\- Prior to 1 January 1997. This Requirement is considered terminating action for the repetitive 1500 hour inspections.\n\nBackground: Several incidents of wing main tank float switch electrical conduit failure have been reported. This condition, if not corrected, could result in a fuel leak from the wing main tank which could propagate down the wing leading edge cavity to the respective engine tail pipe, and cause an external fire under the wing.\n\nThis amendment introduces initial and repetitive inspections for additional aeroplanes and provides terminating action for the repetitive inspections.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This amendment expands the operational scope compared with the earlier directive by (a) introducing inspections for additional aeroplanes identified in the later Boeing Service Letter (737-SL-28-42) in addition to those in 737-SL-28-36, and (b) adding an explicit terminating action (filling conduits with grease per one of three approved documents) that removes the need for the recurring 1,500-hour inspections. Mechanically, the instrument moves from a regime of recurring inspections only to a two-track regime: recurring inspections for aircraft that have not adopted the terminating modification, and a one-off modification that eliminates recurring inspection obligations. This changes operator incentives (one-off cost vs continuing inspection costs), increases the set of affected aircraft, and creates additional compliance tracking complexity due to differing initial compliance dates and the need to record completion of the terminating action."},"complexity_factors":["Three discrete substantive requirements (Requirements 1–3)","Cross-references to three external technical documents (Boeing 737-SL-28-36, 737-SL-28-42 / 42A, and Ansett Engineering Release B73-28-10-6B)","Multiple compliance deadlines and a recurring inspection interval (originally prior to specified dates and thereafter at intervals not exceeding 1,500 hours TIS)","Terminology tied to aircraft-specific Service Letter applicability (requires mapping of serial numbers/models to Service Letters)","Reference to related FAA AD (93-17-02) for background/related actions"],"plain_english_summary":"**What this instrument does (mechanical changes)\n\n- Requires inspections and corrective work on the electrical conduit for the wing main tank float switch on affected Boeing 737 aeroplanes. (The float switch detects fuel level inside the wing tank; the conduit is the wiring passage.)\n- Sets three discrete requirements (see Requirements 1–3):\n  - Requirement 1: For aeroplanes identified in Boeing Service Letter 737-SL-28-36, inspect the float-switch conduit for fuel leaks and water/condensation; if leakage or condensation is found, before the next flight purge the conduit and install a new vapour-seal assembly as described in that Service Letter. (Section labelled Requirement 1.)\n  - Requirement 2: For aeroplanes identified in Boeing Service Letter 737-SL-28-42, perform the same inspection steps using the procedures in Service Letter 737-SL-28-36; if leakage/condensation is found, purge and install a vapour-seal assembly before the next flight. (Requirement 2.)\n  - Requirement 3: As a terminating action for the repetitive inspections, fill the interior of the wing main tank float-switch electrical conduits with grease in accordance with one of three approved technical documents (Boeing 737-SL-28-42, Boeing 737-SL-28-42A, or Ansett Airlines Engineering Release B73-28-10-6B). Completing Requirement 3 ends the need for the 1,500-hour recurring inspections. (Requirement 3.)\n- Prescribes compliance timing: initial and recurring inspections at intervals not exceeding 1,500 flight hours for most affected aircraft, with specified deadlines for initial compliance in some cases (see Compliance section).\n- Cross-refers to FAA AD 93-17-02 for related material. (Note in instrument.)\n\n**Who this affects\n\n- Aircraft operators and owners of the Boeing 737 models listed in the two referenced Boeing Service Letters (737-SL-28-36 and 737-SL-28-42). The instrument applies to \"all model 737 series aeroplanes\" identified by those Service Letters (Applicability).\n- Licensed maintenance organisations and engineers who carry out inspections, purging, installation of vapour-seal assemblies and the grease-filling terminating action.\n- The Civil Aviation Safety Authority (CASA) and operator maintenance planning functions for tracking compliance and scheduling work.\n\n**Why it matters (stated purpose and practical effects)\n\n- Stated safety purpose: incidents of conduit failure have been reported; an unsealed or failed conduit can permit fuel to leak into wing cavities and possibly migrate to engine tail pipes, creating a risk of an external wing fire. The measures aim to detect leakage/condensation early and fix the sealing to prevent fuel escape. (Background.)\n\n**Costs, incentives and trade-offs (how it changes behaviour and who pays)\n\n- Who pays: aircraft operators/owners pay direct maintenance costs — technician labour, parts (vapour-seal assemblies, grease), ground time and possible flight cancellations or schedule disruption while the work is done. Operators also bear administrative costs to record inspections and to schedule recurring checks every 1,500 hours unless terminating action is taken. (See Requirements 1–3 and Compliance.)\n- Who decides/implements: operators decide scheduling within the mandated time windows; licensed maintenance personnel must perform the inspections and corrective work per the referenced Service Letters. CASA enforces compliance. (Requirements and Compliance sections.)\n- Behavioural effects: operators face a choice: continue periodic inspections every 1,500 hours (and perform purge/repair as needed) or perform the terminating grease-fill action by the specified deadline, which stops the need for further 1,500-hour inspections. That creates an economic incentive for operators to adopt the terminating action where feasible to avoid repeated inspection costs.\n- Trade-offs and opportunity costs: terminating action has an upfront cost and a one-time operational disruption, but removes recurring inspection labour and scheduling costs. Repeated inspections impose recurring labour and tracking costs. There may be supply or logistics constraints for parts (vapour seals or approved grease and documentation) which could delay compliance in some fleets.\n- Implementation risk and compliance burden: compliance requires access to the specific Boeing Service Letters or the Ansett Engineering Release, accurate identification of affected aeroplanes, and record-keeping of inspection intervals and completion of terminating action. Different compliance deadlines for different groups (e.g. \"prior to 1 April 1994\" or \"prior to 1 January 1997\") increase administrative complexity. Non-compliance risks enforcement action and, in the operational context, continued safety risk.\n\n**Concrete effects on private choice and markets\n\n- Small effect on competition among operators: those with better maintenance planning or economies of scale may find it easier/cheaper to adopt the terminating grease-fill and thus reduce ongoing costs; smaller operators may prefer recurring inspections if the one-off terminating action has higher immediate cost.\n- No change to aircraft ownership or operating privileges; the instrument modifies maintenance obligations only.\n\n**Official rationale vs practical costs (short test)\n\n- Rationale (as stated): reduce risk of external wing fire by detecting and sealing conduit failures (Background). The required inspections and sealing directly address that mechanism.\n- Practical costs: routine maintenance expense, potential aircraft downtime, parts and labour. The rule designs a clear path to end recurring costs via a specified terminating action (Requirement 3), shifting the burden from indefinite recurring inspections to a one-off modification if operators choose it.\n\nReferences: Requirements 1–3 and Compliance section in the instrument."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The amendment expands the original directive's scope from one set of aircraft (covered by Service Letter 737-SL-28-36) to include additional aircraft (covered by Service Letter 737-SL-28-42). It also introduces a terminating action (the grease filling requirement) that wasn't in the original, effectively changing the directive from an ongoing inspection regime to one with a defined endpoint."},"complexity_factors":["Multiple cross-references to external Boeing Service Letters (737-SL-28-36, 737-SL-28-42, 737-SL-28-42A) and an Ansett Airlines Engineering Release","Three distinct requirements with different compliance dates and intervals","Conditional logic: inspections trigger mandatory pre-flight repairs if defects found","Reference to corresponding FAA Airworthiness Directive (93-17-02 Amdt 39-8672)","Amendment structure requires understanding of what changed from previous version"],"plain_english_summary":"This Australian safety directive requires Boeing 737 operators to inspect the float-switch electrical harnesses inside main fuel tanks for fuel leaks or moisture, grounding any aircraft until defects are fixed. Inspections repeat every 1,500 flight hours until operators perform the terminating action: filling the wiring conduits with grease. Issued after multiple in-flight fire incidents, the amendment expands the inspection scope to additional aircraft and provides the grease fill as a permanent fix."},"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-b737-62-amdt-1-main-fuel-tank-float-switch-electrical-harness","history":"/api/acts/ad-b737-62-amdt-1-main-fuel-tank-float-switch-electrical-harness/history","analysis":"/api/acts/ad-b737-62-amdt-1-main-fuel-tank-float-switch-electrical-harness/analysis","conflicts":"/api/acts/ad-b737-62-amdt-1-main-fuel-tank-float-switch-electrical-harness/conflicts","importantCases":"/api/acts/ad-b737-62-amdt-1-main-fuel-tank-float-switch-electrical-harness/important-cases","documents":"/api/acts/ad-b737-62-amdt-1-main-fuel-tank-float-switch-electrical-harness/documents"}}