{"id":"F2006B07340","name":"AD/TB20/35 - Fuel System","slug":"ad-tb20-35-fuel-system","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49410,"registerId":"commonwealth-F2006B07340-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TB20/35 - Fuel System","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)  \nAerospatiale (Socata) TB20 (Trinidad) Series Aeroplanes\n\nAD/TB20/35 Fuel System 12/99\n\nApplicability: Model TB20 and TB21 aeroplanes serial numbers 1 to 822, 850 to 889 and 889 to 947 equipped with an engine monitoring cluster at amendment D and having a 14 volt electrical system.\n\nNote 1: This Directive is not applicable to aeroplanes with a 24 volt electrical systems.\n\nNote 2: The amendment D engine monitoring cluster is not a production fit and is only available as a spare. The amendment D cluster may be identified by markings on the engine monitoring cluster identification plate.\n\nRequirement: 1. Install a placard adjacent to the fuel indicator, in accordance with Socata Service Bulletin SB 10-099-28 dated February 1999, stating:\n\nIf voltage is lower than 13 VOLTS (below green range), fuel quantity is over-estimated.\n\n    2. Incorporate the following amendments in the Flight Manual (Pilots Operating Handbook). This may be accomplished by inserting a copy of this Directive in the Flight Manual.\n\n    In SECTION 3 ‘EMERGENCY PROCEDURES’, immediately following the ‘ALTERNATOR FAILURE’ procedure insert:\n\n![](image.002.png)\n\n    b. In SECTION 4 ‘NORMAL PROCEDURES’, in ‘PRE-FLIGHT INSPECTIONS’ of the ‘ELECTRICAL SYSTEMS’ procedure, at paragraph ‘a — Cabin’, insert immediately following the entry\n\n‘Fuel gages check’:\n\n![](image.003.png)\n\n    c. In SECTION 4 ‘NORMAL PROCEDURES’, in ‘AFTER STARTING ENGINE’ procedure, insert immediately before the entry\n\n‘Fuel selector set to fullest tank’:\n\n![](image.004.png)\n\nNote 3: DGAC AD 1999-062(A) refers.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nCompliance: 1. Before 31 December 1999.\n\n2. Before 31 December 1999.\n\nThis Airworthiness Directive becomes effective on 2 December 1999.\n\nBackground: This Directive is issued to ensure that pilots are aware that fuel contents may be over- estimated.","sortOrder":0}],"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":3,"scope_assessment":{"changed":false,"description":"The Directive keeps a limited scope: it targets awareness and operational documentation for specific TB20/TB21 aeroplanes with amendment D clusters and 14‑volt systems to mitigate fuel‑gauge over‑reading. It does not expand applicability beyond the listed serial ranges or require hardware replacement, and explicitly excludes 24‑volt systems."},"complexity_factors":["Narrow applicability: limited to TB20/TB21 serial numbers and only aircraft with amendment D engine monitoring cluster and 14‑volt electrical systems (excludes 24‑volt systems).","Simple physical and administrative actions required: install a placard and insert text into the Flight Manual.","Deadline-driven compliance: both actions required before 31 December 1999.","Identification requirement: amendment D cluster is a non‑standard spare and must be identified by markings on the cluster identification plate.","Low technical intervention: no structural modification or engineering work mandated, reducing regulatory and maintenance complexity."],"plain_english_summary":"**What it changes:** Requires owners/operators of Socata TB20/TB21 aeroplanes (specific serial ranges) fitted with an amendment D engine monitoring cluster and a 14‑volt electrical system to install a placard by the fuel gauge and insert prescribed warnings into the Flight Manual that fuel quantity may be over‑estimated when voltage is below 13 volts.  \n**Who pays and acts:** The aircraft owner/operator must carry out the placard installation and manual amendment; pilots must follow the updated pre‑flight and emergency checks to account for possible over‑reading of fuel gauges."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope: addressing a specific safety issue (fuel gauge inaccuracy at low voltage) for a specific aircraft model with specific equipment configurations. There is no evidence of scope creep beyond the original safety purpose."},"complexity_factors":["Single, specific applicability criteria (serial number ranges, electrical system voltage, specific equipment amendment)","Two straightforward requirements with clear compliance deadlines","Simple conditional logic (if voltage < 13V, then fuel over-estimated)","No cross-references to other legislation beyond a reference to a French aviation authority directive (DGAC AD 1999-062(A))","Minimal defined terms (only standard aviation terminology)","Short document length (approximately 300 words)"],"plain_english_summary":"This is a safety notice (called an Airworthiness Directive) for specific Socata TB20 and TB21 aeroplanes. It applies to certain planes with 14-volt electrical systems and a specific type of engine monitoring equipment (amendment D cluster). The directive requires two things: First, installing a warning label near the fuel gauge telling pilots that if voltage drops below 13 volts, the fuel gauge will show more fuel than is actually in the tank. Second, updating the plane's flight manual with new emergency and normal procedures to help pilots check for this problem. All changes must be done by 31 December 1999. The directive became effective on 2 December 1999."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tb20-35-fuel-system","history":"/api/acts/ad-tb20-35-fuel-system/history","analysis":"/api/acts/ad-tb20-35-fuel-system/analysis","conflicts":"/api/acts/ad-tb20-35-fuel-system/conflicts","importantCases":"/api/acts/ad-tb20-35-fuel-system/important-cases","documents":"/api/acts/ad-tb20-35-fuel-system/documents"}}