{"id":"F2006B07314","name":"AD/TB20/11 - Hydraulic Brake Line Clearance","slug":"ad-tb20-11-hydraulic-brake-line-clearance","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49333,"registerId":"commonwealth-F2006B07314-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TB20/11 - Hydraulic Brake Line Clearance","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\nAD/TB20/11 Hydraulic Brake Line Clearance 11/87\n\nApplicability: All model TB20 and TB21 up to S/No 755 inclusive, except S/Nos 630, 631, 634, 636, 643, 648, 649, 656, 657, 658, 659, 661, 662, 663, 664, 750, 751, 752 and 753.\n\n \n\nRequirement: Action in accordance with Aerospatiale Socata SB No 33.\n\n \n\nNote: Bureau Veritas AD 87-118(A) refers.\n\n \n\nCompliance: Within 100 hours time in service or at the next scheduled inspection for maintenance release issue after 30 October 1987 whichever is the earlier.\n\n \n\nBackground: The manufacturer has reported instances of the cockpit hydraulic brake lines being damaged by the aileron and rudder control rods.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in specific aircraft. It has not expanded beyond its original purpose of mandating a brake line clearance fix."},"complexity_factors":["Very short document (under 200 words)","Only 4 substantive sections: Applicability, Requirement, Note, and Compliance","Single cross-reference to manufacturer Service Bulletin and French aviation authority directive","Simple conditional applicability (serial number ranges with explicit exceptions)","Clear, unambiguous deadline (100 hours or next inspection, whichever earlier)","No defined terms section, no nested exceptions, no conditional logic beyond the applicability clause"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — essentially a mandatory safety notice issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:** It orders owners and operators of certain Socata TB20 and TB21 Trinidad aeroplanes to inspect and fix a dangerous design flaw where hydraulic brake lines in the cockpit can be damaged by the aileron (wing control) and rudder (tail control) rods.\n\n**Who it affects:** Owners and operators of TB20 and TB21 aircraft with serial numbers up to 755, **except** for a long list of specific serial numbers (630, 631, 634, 636, 643, 648, 649, 656–659, 661–664, and 750–753).\n\n**What must be done:** Follow the manufacturer's Service Bulletin No. 33 (a technical repair instruction) to fix the brake line clearance problem.\n\n**When it must be done:** Within 100 hours of flying time, or at the next scheduled maintenance check after 30 October 1987 — whichever comes first.\n\n**Why it matters:** Damaged brake lines could lead to brake failure, which is obviously catastrophic during landing or taxiing. This directive prevents accidents by forcing a fix before the problem causes an incident."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive does not alter scope from its apparent original intent: it targets specified TB20/TB21 serial-numbered aeroplanes and requires inspection/modification per the manufacturer's Service Bulletin No. 33 within the stated timeframe."},"complexity_factors":["Applicability is limited to TB20/TB21 aircraft up to S/N 755 with multiple serial-number exceptions, requiring accurate identification of affected airframes.","Mandates action by reference to an external document (Aerospatiale Socata Service Bulletin No. 33), creating dependency on that SB's content and availability.","Compliance timetable is precise (within 100 hours TIS or next scheduled inspection), affecting maintenance scheduling and logistics.","Regulatory enforcement by CASA implies record-keeping and proof of compliance obligations for owners/operators.","Cross-reference to another authority's AD (Bureau Veritas AD 87-118(A)) may require cross-checking multiple documents for full instructions."],"plain_english_summary":"*This Airworthiness Directive requires owners/operators of specified Socata TB20/TB21 aeroplanes (listed serial numbers) to follow Aerospatiale Socata Service Bulletin No. 33 to inspect and correct cockpit hydraulic brake‑line clearance to prevent contact with aileron and rudder control rods.* The Civil Aviation Safety Authority mandates compliance within 100 flight hours or at the next scheduled maintenance inspection after 30 October 1987. Aircraft owners/operators pay for and arrange the inspection or modification; CASA enforces the requirement."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tb20-11-hydraulic-brake-line-clearance","history":"/api/acts/ad-tb20-11-hydraulic-brake-line-clearance/history","analysis":"/api/acts/ad-tb20-11-hydraulic-brake-line-clearance/analysis","conflicts":"/api/acts/ad-tb20-11-hydraulic-brake-line-clearance/conflicts","importantCases":"/api/acts/ad-tb20-11-hydraulic-brake-line-clearance/important-cases","documents":"/api/acts/ad-tb20-11-hydraulic-brake-line-clearance/documents"}}