{"id":"F2006B11303","name":"AD/ML-M5/6 - Auxiliary Fuel Tank Venting - Inspection, Testing and Modification","slug":"ad-ml-m5-6-auxiliary-fuel-tank-venting-inspection-testing-and-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":57138,"registerId":"commonwealth-F2006B11303-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ML-M5/6 - Auxiliary Fuel Tank Venting - Inspection, Testing and Modification","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)  \nMaule M-5 Series Aeroplanes\n\nAD/ML-M5/6 Auxiliary Fuel Tank Venting \\- Inspection,\n\nTesting and Modification\n\n  \n6/84\n\nApplicability: Maule models (equipped with auxiliary fuel tank vent line check valves only):\n\nM-5-180 S/N 8004C to 8014C S/N 8016C to 8019C;\n\nM-5-20 S/N 8022C;\n\nM-5-21-TC S/N 9001C to 9010C\n\nM-5-235C S/N 7290C to 7355C S/N 7357C to 7376C S/N 7451C;\n\nand all aircraft retrofitted with auxiliary fuel tank vent line check valves.\n\nDocument: Maule aircraft S.B. No. 6.\n\nCompliance: Within 100 hours time in service after 30 June 1984.\n\nBackground: Check valves fitted in the vent lines of aircraft fitted with auxiliary tanks may be incorrectly assembled causing the valves to be ineffective. Modifications to “STANT” fuel caps are also included to revert them to the vented type.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive’s scope, as written, covers specific Maule M-5 series serial numbers and any aircraft retrofitted with the auxiliary tank vent line check valves and requires inspection/testing/modification within a specified time. The text’s stated purpose (remedying possibly incorrectly assembled check valves and reverting certain fuel caps to vented type) aligns with that scope; the instrument does not, on its face, expand beyond that stated aim (Applicability; Background; Compliance)."},"complexity_factors":["Serial-number-specific applicability requires owners to check aircraft identity against a precise list (Applicability).","Technical nature of fault (auxiliary tank vent line check valve assembly and STANT fuel cap venting) requires qualified inspection, testing and possible modification (Background, Document).","Fixed and relatively short compliance window (100 hours TIS after 30 June 1984) creates scheduling pressure (Compliance).","Dependence on an external procedural document (Maule aircraft S.B. No. 6) means practitioners must obtain and follow manufacturer guidance (Document).","Inclusion of retrofitted aircraft broadens scope beyond factory-built serial-number ranges and may require records checks to determine applicability (Applicability)."],"plain_english_summary":"What this directive does (mechanical change):\n\n- Requires inspection, testing and any necessary modification of auxiliary fuel tank venting hardware on specific Maule M-5 series aeroplanes and on any aircraft that have been retrofitted with auxiliary fuel tank vent line check valves. The work should be done to the procedures set out in Maule aircraft Service Bulletin No. 6 (Document) and completed within 100 hours time in service after 30 June 1984 (Compliance).\n\nWho is affected:\n\n- Owners and operators of the listed Maule M-5 series aeroplanes by serial number and any aircraft retrofitted with auxiliary tank vent line check valves (Applicability).\n- Maintenance organisations, technicians and parts suppliers who will perform the inspections, tests and modifications and supply any replacement parts (Document).\n\nWhy it matters (stated purpose and test of that purpose):\n\n- The directive’s stated purpose is to address a risk that check valves fitted in auxiliary tank vent lines may be incorrectly assembled so they are ineffective, and to require modifications to certain “STANT” fuel caps to revert them to the vented configuration (Background).\n\n- Who pays and who decides: aircraft owners/operators pay for the inspection, testing and any modification work and must decide to arrange that work within the specified 100-hour deadline (Compliance). The procedures to follow are those in Maule aircraft S.B. No. 6 (Document). The directive is issued as a Schedule of Airworthiness Directives under the Civil Aviation Regulations, Part 39 (header), which prescribes the obligation.\n\n- Incentives and behavioural effects: owners/operators are incentivised to commission the required work to comply with the directive and to restore the venting function. Maintenance providers have an incentive to offer the inspection and modification work; this generates demand for parts, labour and shop time.\n\n- Costs, trade-offs and opportunity cost: the principal direct cost is the inspection, testing and any required modification (parts and labour) borne by owners/operators within the 100-hour TIS window. There is an opportunity cost in aircraft downtime and use of maintenance capacity during that window.\n\n- Implementation risk and compliance burden: the directive imposes a time-limited compliance requirement (100 hours TIS after 30 June 1984). A practical implementation task is identifying whether a particular aircraft is within the applicable serial number ranges or has been retrofitted with the specified check valves (Applicability). The work must follow the manufacturer’s service bulletin (Document), so access to that bulletin and to qualified technicians is necessary.\n\n- Effects on private choice and market actors: the directive constrains owners/operators to take specified maintenance actions to meet the airworthiness requirement; independent maintenance providers can compete to supply the work and parts. The immediate benefit of corrected venting accrues to the affected aircraft and their operators; the cost burden is concentrated on those owners/operators required to comply.\n\n- Concentrated benefits and costs: benefits (restored vent function) are concentrated on operators of affected aircraft; costs (inspection/modification expense and downtime) are likewise concentrated on those same operators. The directive does not, in its text, describe broader industry-wide subsidies, exemptions or displaced regulatory obligations.\n\nKey textual references: the list of affected models and serial numbers and the inclusion of retrofitted aircraft are in the Applicability paragraph; the procedural document is Maule aircraft S.B. No. 6 (Document); the compliance timeframe is in Compliance; the stated reason for the directive is in Background."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope. It addresses a specific manufacturing defect in a limited production run of Maule aircraft and does not appear to have expanded beyond its initial safety purpose."},"complexity_factors":["Very short document (approximately 150 words)","Only 4 defined applicability categories (specific aircraft models by serial number)","Single compliance requirement with clear deadline (100 hours time in service after 30 June 1984)","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","No conditional logic or nested exceptions","Single technical reference document (Maule S.B. No. 6)","Straightforward cause-and-effect: identified defect → mandatory inspection/fix"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by the Civil Aviation Safety Authority (CASA) that requires specific aircraft owners to inspect and fix a potentially dangerous fuel system problem.\n\n**What it does:**\n- Requires owners of specific **Maule M-5 series aeroplanes** (small single-engine aircraft) to inspect the check valves in their auxiliary fuel tank vent lines\n- These valves may have been assembled incorrectly at the factory, meaning they might not work when needed\n- Also requires modifications to \"STANT\" fuel caps to make them vented again\n\n**Who it affects:**\n- Owners of specific Maule models with serial numbers listed above (M-5-180, M-5-20, M-5-21-TC, M-5-235C)\n- Anyone who has retrofitted auxiliary fuel tank vent line check valves to their Maule aircraft\n\n**Why it matters:**\n- Fuel tank vents prevent dangerous pressure build-ups or vacuum formation that could cause engine fuel starvation or tank damage\n- If check valves fail, the auxiliary tanks may not vent properly, creating a serious flight safety risk\n- This is a **mandatory compliance** — owners must complete the work within 100 flight hours after 30 June 1984\n\n**What owners must do:**\n- Follow the manufacturer's Service Bulletin No. 6 for the specific inspection, testing and modification procedures\n- Complete the work within the specified timeframe or the aircraft cannot legally fly"}},"importantCases":[],"_links":{"self":"/api/acts/ad-ml-m5-6-auxiliary-fuel-tank-venting-inspection-testing-and-modification","history":"/api/acts/ad-ml-m5-6-auxiliary-fuel-tank-venting-inspection-testing-and-modification/history","analysis":"/api/acts/ad-ml-m5-6-auxiliary-fuel-tank-venting-inspection-testing-and-modification/analysis","conflicts":"/api/acts/ad-ml-m5-6-auxiliary-fuel-tank-venting-inspection-testing-and-modification/conflicts","importantCases":"/api/acts/ad-ml-m5-6-auxiliary-fuel-tank-venting-inspection-testing-and-modification/important-cases","documents":"/api/acts/ad-ml-m5-6-auxiliary-fuel-tank-venting-inspection-testing-and-modification/documents"}}