{"id":"F2006B07316","name":"AD/TB20/13 Amdt 1 - Fuel Tanks","slug":"ad-tb20-13-amdt-1-fuel-tanks","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49339,"registerId":"commonwealth-F2006B07316-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TB20/13 Amdt 1 - Fuel Tanks","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Aerospatiale (Socata) TB20 (Trinidad) Series Aeroplanes\n\n \n\n# AD/TB20/13\n\nAmdt 1\n\nApplicability: Model TB20 and TB21.\n\n# Fuel Tanks 5/90\n\n \n\nRequirement: 1. Unless modified in accordance with Requirement 2, carry out the following action:\n\n \n\n(a)     Position the aircraft in a wings level and a nose-down ground attitude of about 2 degrees.\n\n \n\nNote: This is achieved on level ground when the height from the ground to the spinner centre equals the height from the ground to the lower part of the rear mooring fitting.\n\n \n\n(b)     Leave the aircraft in this attitude for at least 20 minutes, then drain as described in (c) below; drain from each point at least 500 ml of fuel.\n\n \n\n(c)     Aircraft S/N 1 to 730:\n\n \n\nDrain L.H wing fuel tank then R.H wing fuel tank.\n\n \n\nNote: On TB20 and TB21 airplanes, the fuel filter which is located under engine cowling should not be drained as it is not the low point of fuel system. Should filter be drained, apply procedure given in Maintenance Manual concerning filter installation and removal.\n\n \n\nAircraft from S/N 731:\n\n \n\n(i)       Select L.H fuel tank\n\n \n\n(ii)    Drain L.H wing fuel tank\n\n \n\n(iii)  Drain fuel filter under fuselage\n\n \n\n(iv)   Drain R.H wing fuel tank.\n\n \n\n(d)     Visually inspect fuel filter caps seals (broken, cracked, torn, kinked) and replace if necessary.\n\n \n\nInstall caps and check security.\n\n \n\n2. Modify the fuel tanks in accordance with Socata TB Service Bulletin No. 48.\n\n \n\nNote: DGAC AD 89-177(A) and Socata TB Service Bulletin No 48 refer.\n\n \n\nCompliance:  1. For aircraft which have not been flown for one week or more; prior to the next flight after 22 February 1990, and thereafter prior to the next flight any time a period of one week or more occurs between flights.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\nFor aircraft which are flying at periods of less than one week between flights; within 25 hours time in service after 22 February 1990, and thereafter at periods not exceeding 50 hours time in service.\n\n \n\n2. Prior to 28 February 1991.\n\n \n\nNote: This Directive shall be entered on the Maintenance Release as maintenance required. The inspection required by Para 1 may be performed by the pilot in command, in which case certification is required. A copy of this Directive shall be carried in the aircraft.\n\n \n\nBackground:  This Airworthiness Directive is issued to reflect a Country of origin AD which requires regular inspections to detect any water/contamination in the fuel tanks until a modification is incorporated. This relocates the tank drain and outlet holes and reworks rib sections to ensure all drainable water/contamination collects at the tank drain point when the aircraft is in normal ground attitude.\n\n \n\nAmendment 1 is raised to introduce revisions to the manufacturers document, which clarifies aircraft nose down attitude, and the country of origin AD which increases the period between inspections.\n","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":5,"scope_assessment":{"changed":true,"description":"Amendment 1 modifies compliance mechanics rather than broadening affected aircraft: it clarifies the required nose‑down ground attitude and adopts a longer inspection interval as reflected in the country‑of‑origin AD and revised manufacturer documentation. The set of affected models (TB20/TB21) and the option to incorporate the Service Bulletin remain the same, but timing and procedural clarity were changed."},"complexity_factors":["Conditional draining procedure that depends on serial number ranges (S/N 1–730 vs S/N 731+) with different drain points and sequence (Requirement 1(c)).","Precise pre‑drain aircraft attitude and hold time (wings level, ~2° nose‑down for at least 20 minutes) that affects where contaminants collect (Requirement 1(a),(b)).","Multiple compliance timing paths: inspections before next flight after one week of storage, recurring before next flight after any one‑week gap, or for frequently flown aircraft within 25 hours TIS after 22 Feb 1990 and thereafter every 50 hours TIS (Compliance).","Modification alternative (Socata TB Service Bulletin No. 48) that, once incorporated before 28 Feb 1991, terminates the recurring drain requirement (Requirement 2; Compliance).","Pilot‑performed inspection option with required certification and requirement to carry a copy of the Directive on board, which shifts compliance burden and introduces recordkeeping responsibility (Compliance Note).","Maintenance detail sensitivity (do not drain engine‑cowl fuel filter on some models; maintenance manual actions required if drained) creating procedural risk if misunderstood (Requirement 1(c) Note)."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of Aerospatiale (Socata) TB20 and TB21 aeroplanes to place the aircraft in a wings‑level, about 2° nose‑down attitude, hold it 20 minutes, then drain specified fuel tank points and inspect fuel filter cap seals. If modified per Socata TB Service Bulletin No. 48 the recurring drains are not required. Amendment 1 clarifies how to set the nose‑down attitude and adopts a longer inspection interval referenced from the country‑of‑origin AD."},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This is Amendment 1 to an existing AD. The amendment scope is narrow: it clarifies the nose-down attitude measurement and extends inspection intervals based on updated manufacturer and French aviation authority (DGAC) guidance. The core purpose — interim fuel draining inspections plus mandatory tank modification — remains unchanged from the original AD."},"complexity_factors":["Multiple compliance paths based on aircraft usage patterns (flown weekly vs. not flown weekly)","Serial number-dependent procedural variations (S/N 1-730 vs. 731+)","Dual-phase compliance (interim inspections + permanent modification)","Specific physical positioning requirements (2-degree nose-down attitude with measurement guidance)","Cross-references to external documents (Socata Service Bulletin No. 48, DGAC AD 89-177(A))","Conditional logic for pilot-performed vs. mechanic-performed certification"],"plain_english_summary":"CASA has issued a mandatory AD for Socata TB20/TB21 aircraft requiring regular draining and inspection of fuel tanks for water/contamination and, by a set deadline, installation of a manufacturer tank modification to correct a drainage/design flaw. It affects TB20/TB21 owners and pilots; interim inspections and recordkeeping are required to prevent fuel-related engine failure until the permanent fix is fitted."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tb20-13-amdt-1-fuel-tanks","history":"/api/acts/ad-tb20-13-amdt-1-fuel-tanks/history","analysis":"/api/acts/ad-tb20-13-amdt-1-fuel-tanks/analysis","conflicts":"/api/acts/ad-tb20-13-amdt-1-fuel-tanks/conflicts","importantCases":"/api/acts/ad-tb20-13-amdt-1-fuel-tanks/important-cases","documents":"/api/acts/ad-tb20-13-amdt-1-fuel-tanks/documents"}}