{"id":"F2006B07345","name":"AD/TB20/4 - Wing Drainage - Modification","slug":"ad-tb20-4-wing-drainage-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49428,"registerId":"commonwealth-F2006B07345-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TB20/4 - Wing Drainage - Modification","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/TB20/4 Wing Drainage - Modification 4/85 DM\n\nApplicability: All model TB20 with S/Nos up to 433 and No 444. Requirement: Aerospatiale SOCATA TB SB No. 26.\n\nCompliance: Unless already accomplished, within the next 50 hours time in service after 8 March 1985.\n\n \n\nBackground: The purpose of this modification is to provide proper drainage of the wing tip forward spar box.\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\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 airworthiness concern (wing drainage) for a limited aircraft population. It has not expanded beyond its original technical purpose."},"complexity_factors":["Very short document (under 200 words)","Only 4 operative provisions: applicability, requirement, compliance deadline, and background","Single cross-reference to manufacturer service bulletin (SB No. 26)","No defined terms section","No nested conditions or exceptions — straightforward command structure","Single compliance trigger (time-in-service hours) with one exemption (already accomplished)"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires aircraft owners to fix a specific problem.\n\n**What it does:** It orders owners of certain **Aerospatiale (Socata) TB20 Trinidad aeroplanes** to modify the wing drainage system. Specifically, they must install a fix to ensure the **wing tip forward spar box** (a structural part inside the wing near the tip) drains properly.\n\n**Who it affects:** Owners and operators of TB20 aircraft with **serial numbers up to 433 and serial number 444**.\n\n**What they must do:** Follow the manufacturer's Service Bulletin No. 26 (a technical instruction from the plane maker) to modify the wing drainage. This must be done **within 50 hours of flying time** after 8 March 1985, unless already completed.\n\n**Why it matters:** Poor drainage in the wing structure can lead to water accumulation, which causes **corrosion** (rust) or **structural damage** — potentially compromising wing strength and flight safety."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive's text specifies a single modification objective and a defined set of affected aircraft (Applicability; Requirement; Background). It does not indicate any expansion or narrowing of scope beyond requiring implementation of Aerospatiale SOCATA TB Service Bulletin No. 26 within the stated compliance window (Requirement; Compliance). No change of scope from the stated purpose is indicated in the document."},"complexity_factors":["Narrow, clearly defined applicability (specific serial numbers) (Applicability)","Single, discrete technical action required (modification for wing drainage) (Requirement)","Reference to an external service bulletin for technical detail, so AD text is short but requires consulting another document (Requirement)","Short statutory compliance window (50 hours TIS after a specified date) imposes scheduling constraints (Compliance)","Administrative burdens limited to arranging and funding maintenance; no new regulatory regimes or ongoing reporting requirements (Requirement; Compliance)"],"plain_english_summary":"This AD mandates that owners/operators of SOCATA TB20 aeroplanes (S/Ns up to 433 and S/No 444) carry out the Service Bulletin No. 26 wing tip forward spar box modification within 50 hours TIS after 8 March 1985. It’s required to provide proper drainage, reduces corrosion risk, and is carried out and funded by the aircraft owner/operator."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tb20-4-wing-drainage-modification","history":"/api/acts/ad-tb20-4-wing-drainage-modification/history","analysis":"/api/acts/ad-tb20-4-wing-drainage-modification/analysis","conflicts":"/api/acts/ad-tb20-4-wing-drainage-modification/conflicts","importantCases":"/api/acts/ad-tb20-4-wing-drainage-modification/important-cases","documents":"/api/acts/ad-tb20-4-wing-drainage-modification/documents"}}