{"id":"F2006B02845","name":"AD/B737/143 - Fuel Low Pressure Switches and Boost Pumps","slug":"ad-b737-143-fuel-low-pressure-switches-and-boost-pumps","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42187,"registerId":"commonwealth-F2006B02845-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\n![](image.002.png)  \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 CAR 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.","sortOrder":0},{"sectionNumber":"AD/B737/143 Fuel Low Pressure Switches a","sectionType":"part","heading":"AD/B737/143 Fuel Low Pressure Switches and Boost Pumps 7/2000","content":"# AD/B737/143 Fuel Low Pressure Switches and Boost Pumps 7/2000\n\nApplicability: Model 737-100, \\-200, \\-300, \\-400 and \\-500 series aeroplanes line number 1 through\n\n3002 inclusive.\n\nRequirement: 1. Inspect main tank fuel boost pumps to determine if one or more pumps were manufactured by General Electric Company (GEC) of the United Kingdom. If GEC pumps are fitted test each pump in accordance with instructions in Boeing Alert Service Bulletin 737-28A1114 Revision 2 dated January 28, 1999. If the fuel boost pump output pressure is less that 23 pounds per square inch gauge (psig) as measured at the inlet to the engine fuel pump; or less than 36 psig as measured at the fuel boost pump low pressure switch, replace the fuel boost pump with a new or serviceable fuel pump in accordance with the Alert SB.\n\n    2. No aircraft shall be dispatched with any main fuel boost pump inoperative unless initial testing and any follow on corrective action in accordance with Requirement 1 have been complied with.\n\n    3. Replace all 4 low pressure switches installed downstream of the main fuel boost pumps with higher threshold low pressure switches in accordance with Boeing SB 737-28A1114 Revision 2.\n\nNote : FAA AD 2000-04-02 Amendment 39-11584 refers.\n\nCompliance: 1. Prior to the accumulation of 3,000 flight hours or within 1 year from the aircraft date of manufacture, or within 90 days from the effective date of this Directive whichever occurs first. Thereafter, retest at intervals not exceeding 6 months time in service until Requirement 3 has been complied with.\n\n    2. Prior to further flight after the effective date of this Directive.\n\n    3. Within 2 years time in service from the effective date of this Directive. This Airworthiness Directive becomes effective on 13 July 2000.","sortOrder":1}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard, narrowly-targeted airworthiness directive addressing a specific unsafe condition in specific aircraft models. The scope remains tightly focused on fuel system safety for early Boeing 737 variants, with no evidence of scope creep beyond the original safety purpose."},"complexity_factors":["Short, single-purpose directive with only 3 requirements","Clear applicability section limiting scope to specific Boeing 737 models and line numbers","Straightforward conditional logic (if GEC pumps fitted → test → if pressure low → replace)","Specific technical references to Boeing Service Bulletin 737-28A1114 Revision 2","Three-tiered compliance schedule with different deadlines for each requirement","No nested definitions or extensive interpretation sections","Single cross-reference to FAA AD 2000-04-02 for context"],"plain_english_summary":"This CASA Airworthiness Directive requires operators of Boeing 737 Classic (models 100–500, s/n 1–3002) to inspect and test certain General Electric fuel boost pumps and replace any that fail, and to fit upgraded low‑pressure switches. It prevents fuel‑pressure loss that can cause engine flame‑out. Affected aircraft must comply within specified deadlines and cannot fly with defective pumps until corrected."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive remains focused on correcting a narrowly-defined unsafe condition (low boost-pump output pressure and related low pressure switch settings) on specified early-model 737 aeroplanes. It does not broaden the regulatory reach beyond that technical objective: the measures are inspection, testing, short-term operational restriction, recurring checks until hardware replacement, and replacement of the low pressure switches. There is no evident expansion beyond the original safety-focused purpose."},"complexity_factors":["Applicability limited to specific Boeing 737 series and line numbers 1–3002 (narrow scope)","Three substantive requirements (inspect/test/replace pumps; dispatch prohibition; replace four low pressure switches)","Numeric pass/fail thresholds for tests: 23 psig at engine fuel pump inlet and 36 psig at the boost-pump low pressure switch","Conditional compliance timing with multiple 'whichever occurs first' triggers (3,000 flight hours OR 1 year from manufacture OR 90 days from effective date)","Recurring test frequency (every 6 months) until a hardware replacement obligation is met","Cross-reference to Boeing Alert Service Bulletin 737-28A1114 Revision 2 for test and replacement procedures","Reference to FAA AD 2000-04-02 (external regulatory cross-reference)","Operational constraint (no dispatch with an inoperative main boost pump unless testing and corrective action completed) introduces immediate compliance checks"],"plain_english_summary":"**What this directive does (mechanically)**\n\n- Requires operators of certain Boeing 737-100/200/300/400/500 aeroplanes (line numbers 1–3002) to inspect the main fuel boost pumps to see whether they are the model manufactured by General Electric Company (GEC) of the UK and, if so, to test those pumps and take corrective action per Boeing Alert Service Bulletin 737-28A1114 Rev 2. (Requirement 1)\n- Sets pass/fail pressure limits for those tests: a pump fails if output pressure is under 23 psig measured at the inlet to the engine fuel pump, or under 36 psig measured at the fuel boost pump low pressure switch. Failed pumps must be replaced with new or serviceable pumps following the Alert Service Bulletin. (Requirement 1)\n- Prohibits dispatching an aircraft with any main fuel boost pump inoperative unless the initial testing and any corrective action required by Requirement 1 have been completed. (Requirement 2)\n- Requires replacement of all four low pressure switches (downstream of the main boost pumps) with switches that have a higher activation threshold, in accordance with the same Boeing Service Bulletin. (Requirement 3)\n\n**Who this affects**\n\n- Airline operators and aircraft maintenance organisations that operate or maintain Boeing 737-100/200/300/400/500 series aeroplanes within the listed line-number range.\n- Maintenance shops and parts suppliers that source, test or install main fuel boost pumps and low pressure switches for those aeroplanes.\n\n**Compliance timing and testing frequency (how and when it must be done)**\n\n- Initial action: before the aircraft accumulates 3,000 flight hours OR within 1 year from the aircraft's date of manufacture OR within 90 days from the directive's effective date — whichever of those happens first. (Compliance 1)\n- If GEC pumps are fitted and initial testing is done, retest every 6 months until you have completed the Requirement 3 replacement of the low pressure switches. (Compliance 1)\n- You may not dispatch an aircraft with a main boost pump inoperative unless you have done the initial testing and any corrective action required by Requirement 1. (Requirement 2 / Compliance 2)\n- Replacement of all four low pressure switches must be completed within 2 years from the effective date of the directive. (Requirement 3 / Compliance 3)\n\n**Why the regulator says it matters**\n\n- The stated safety concern is that certain fuel boost pumps (identified as GEC pumps) may produce insufficient output pressure, which could lead to inadequate fuel feed to the engine fuel pump. Replacing the low pressure switches with higher-threshold units and removing underperforming pumps are intended to detect and correct that unsafe condition. (Requirement 1–3; Note: FAA AD referenced)\n\n**Who pays, who decides, and what behaviour changes**\n\n- Who pays: aircraft operators and their maintenance providers bear the direct costs (inspection labour and equipment, recurrent testing, buying and installing replacement pumps and higher-threshold switches, aircraft downtime). Parts suppliers and maintenance organisations may incur increased workload and parts procurement activity. \n- Who decides: the CASA delegate issues and enforces the directive; the technical action and test procedures are carried out by the operator or maintenance organisation in accordance with Boeing Alert Service Bulletin 737-28A1114 Rev 2. \n- Behaviour changes required: identify pump manufacturer, perform pressure tests at specified measurement points; replace non-conforming pumps; install higher-threshold low pressure switches across all four boost-pump channels; comply with recurring tests until switches are replaced; do not dispatch aircraft with any main boost pump inoperative unless tests and corrective work have been completed.\n\n**Costs, incentives, trade-offs and implementation considerations**\n\n- Direct costs: purchase and installation of replacement pumps and four higher-threshold switches per aircraft; labour for inspections, testing and replacements; scheduled and unscheduled downtime while parts are sourced and work is completed.\n- Ongoing compliance burden: where GEC pumps are present, operators must retest every 6 months until the switches are replaced — an ongoing maintenance and record-keeping burden until Requirement 3 is satisfied. \n- Incentives and substitution effects: operators may choose between (a) repeated testing and short-term fixes, or (b) a one-off investment to replace pumps and switches proactively to remove the recurring testing obligation. That choice affects cash flow and scheduling decisions. Maintenance providers and parts suppliers stand to gain near-term demand. \n- Implementation risks: correct identification of pump manufacturer and correct pressure measurement location are necessary for consistent compliance; parts availability (GEC vs alternative pumps, replacement switches) can affect how quickly operators meet the 2-year replacement deadline; reliance on Boeing Alert Service Bulletin procedures means operators must follow an external technical document to meet the regulatory requirement. \n- Enforcement discretion and practical effect: the regulator prescribes outcomes and references a Service Bulletin for methods; operational restriction (no dispatch with an inoperative main pump unless initial testing/corrective action done) creates a conservative operational constraint aimed at immediate risk control.\n\n**Net, mechanically**\n\n- The directive creates a time-limited program of identification, testing, periodic retesting, and component replacement targeted at certain boost pumps and low pressure switches on early-model 737s. It forces short-term operational constraints (dispatch prohibition with inoperative pumps unless tested) and a medium-term hardware change (replace low pressure switches within 2 years), shifting the financial and operational burden onto aircraft operators and maintenance suppliers. (Requirements 1–3; Compliance 1–3)"},"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-b737-143-fuel-low-pressure-switches-and-boost-pumps","history":"/api/acts/ad-b737-143-fuel-low-pressure-switches-and-boost-pumps/history","analysis":"/api/acts/ad-b737-143-fuel-low-pressure-switches-and-boost-pumps/analysis","conflicts":"/api/acts/ad-b737-143-fuel-low-pressure-switches-and-boost-pumps/conflicts","importantCases":"/api/acts/ad-b737-143-fuel-low-pressure-switches-and-boost-pumps/important-cases","documents":"/api/acts/ad-b737-143-fuel-low-pressure-switches-and-boost-pumps/documents"}}