{"id":"F2006B08548","name":"AD/CHA/21 - Wing Rib/Spar Attachment and L.E. Support Block Nails","slug":"ad-cha-21-wing-rib-spar-attachment-and-l-e-support-block-nails","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":51339,"registerId":"commonwealth-F2006B08548-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CHA/21 - Wing Rib/Spar Attachment and L.E. Support Block Nails","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)  American Champion (Aeronca, Bellanca) Series Aeroplanes\n\n \n\nAD/CHA/21 Wing Rib/Spar Attachment and\n\nL.E. Support Block Nails\n\n\n4/80\n\n \n\nApplicability: All models 7GC, 7GCA, 7GCB, 7GCBA, 7HC, 7KC and 7KCAB; All models 7ECA with S/Nos. 1 to 1350-80; All models 7GCAA with S/Nos. 1 to 396-80; All models 7GCBC with S/Nos. 1 to 1213-80; All models 8KCAB with S/Nos. 3-70 to 638-80; All models 8GCBC with S/Nos. 1-74 to 355-80.\n\n \n\nRequirement: Action in accordance with Bellanca SL No. C-139. Compliance: In accordance with Requirement Document.\n\nBackground: The manufacturer has received reports of the rib/spar attachment and leading edge support block nails loosening and backing out of the spar.\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 manufacturing defect in specific aircraft. It has not expanded beyond its original purpose of mandating inspection/repair of wing nail attachments."},"complexity_factors":["Very short document (approximately 200 words)","Only 2 substantive operative provisions: applicability and requirement","No defined terms section — uses plain language and manufacturer references","Single cross-reference to external document (Bellanca SL No. C-139)","No conditional logic, exceptions, or nested provisions","Applicability determined by simple model/serial number matching"],"plain_english_summary":"This is an **Airworthiness Directive** (AD) — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires owners and operators of specific American Champion aeroplane models to inspect and fix a structural problem with the wings.\n\n**What the problem is:**\nThe manufacturer discovered that nails securing the wing ribs to the main spar (the central structural beam of the wing), and nails in the leading edge support blocks, can loosen and fall out. This is a serious safety risk because it weakens the wing structure.\n\n**Who must comply:**\nOwners of specific American Champion (formerly Aeronca and Bellanca) aircraft models, including various 7-series and 8-series models with particular serial number ranges. The directive lists exact model numbers and serial numbers — if your plane matches, you must act.\n\n**What you must do:**\nFollow the manufacturer's Service Letter No. C-139. This document contains the detailed inspection and repair instructions. The directive itself doesn't repeat those instructions — it simply makes them legally mandatory.\n\n**Why it matters:**\nWing structural failures can be catastrophic. This AD ensures potentially dangerous aircraft are identified and repaired before they fly."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The directive is narrowly targeted to specific American Champion (Aeronca, Bellanca) models and serial-number ranges and requires action as set out in Bellanca SL No. C-139. Nothing in the text indicates an expansion or contraction of that scope from the stated purpose (to address reported loosening/backing out of rib/spar attachment and L.E. support block nails). (Applicability; Background; Requirement)"},"complexity_factors":["Short AD that defers substantive technical actions to an external document (Bellanca SL No. C-139), requiring operators to obtain and follow another document (Requirement).","Narrow, serial-numbered applicability requiring careful identification of affected airframes (Applicability).","Technical nature of the issue (rib/spar attachment and L.E. support block nails loosening/backing out) which requires skilled maintenance work and parts, though the AD does not specify procedures (Background; Requirement).","Compliance verification depends on the content and clarity of the referenced Service Letter rather than the AD text itself (Requirement).","Regulatory context (issued under Civil Aviation Regulations, Part 39) which implies formal mandatory status and possible enforcement, adding procedural oversight complexity (header)."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of the listed American Champion (Aeronca, Bellanca) models/serial ranges to carry out the work in Bellanca Service Letter No. C‑139 because rib/spar attachment and leading‑edge support block nails have been found loosening. Compliance is mandatory, costs (inspection/repair, parts, downtime) fall to operators, and affected operators/technicians must obtain and follow SL C‑139 to complete the required inspections and repairs."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cha-21-wing-rib-spar-attachment-and-l-e-support-block-nails","history":"/api/acts/ad-cha-21-wing-rib-spar-attachment-and-l-e-support-block-nails/history","analysis":"/api/acts/ad-cha-21-wing-rib-spar-attachment-and-l-e-support-block-nails/analysis","conflicts":"/api/acts/ad-cha-21-wing-rib-spar-attachment-and-l-e-support-block-nails/conflicts","importantCases":"/api/acts/ad-cha-21-wing-rib-spar-attachment-and-l-e-support-block-nails/important-cases","documents":"/api/acts/ad-cha-21-wing-rib-spar-attachment-and-l-e-support-block-nails/documents"}}