{"id":"F2006B08360","name":"AD/CESSNA 400/77 - Aft Auxiliary Wing Spar Attachment - Modification","slug":"ad-cessna-400-77-aft-auxiliary-wing-spar-attachment-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115767,"registerId":"commonwealth-F2006B08360-current","compilationNumber":null,"startDate":"2026-04-03","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 400/77 - Aft Auxiliary Wing Spar Attachment - 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)  Cessna 400 Series Aeroplanes\n\n \n\n# AD/CESSNA 400/77  Aft Auxiliary Wing Spar Attachment - Modification\n\nApplicability: All model 421C with S/Nos. 421C0801 to 421C0886. Document:  Cessna Multi-Engine Customer Care SIL ME80-38. Compliance:               Before issue of Australian Certificate of Airworthiness.\n\n# 1/81\n\nBackground: The manufacturer advises that fasteners used in the attachment of the Aft Auxiliary Wing Spar Caps to the stub wing require replacement with NAS517-3-5 Screws and HL70-6 Hylok collars.\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":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1474},"content_quality":"ok","complexity_score":1,"scope_assessment":{"changed":false,"description":"The directive maintains its original narrow technical scope, targeting only the specific safety defect in wing spar fastener installation for the identified Cessna 421C aircraft models."},"complexity_factors":["Single, unambiguous mechanical requirement with no exceptions","Narrow applicability limited to one aircraft model and specific serial number range","No defined terms, interpretation sections, or cross-references to other legislation","Simple binary compliance trigger (prior to Certificate of Airworthiness issuance)"],"plain_english_summary":"This **Airworthiness Directive** is a safety order requiring a specific mechanical fix on certain Cessna aircraft before they can legally fly in Australia.\n\n**Who it affects:**\nOwners and operators of Cessna 421C aircraft with serial numbers 421C0801 through 421C0886.\n\n**What you must do:**\nBefore the aircraft can be issued an Australian Certificate of Airworthiness (the official document allowing it to fly), you must replace specific fasteners (screws and locking collars) where the rear auxiliary wing spar connects to the stub wing. The old parts must be replaced with **NAS517-3-5 screws** and **HL70-6 Hylok collars**.\n\n**Why it matters:**\nThe manufacturer identified that the original fasteners could fail, potentially causing structural problems with the wing attachment. This modification prevents a safety hazard that could endanger the aircraft in flight.\n\n**Compliance deadline:**\nThis must be completed before the aircraft receives its Certificate of Airworthiness."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-400-77-aft-auxiliary-wing-spar-attachment-modification","history":"/api/acts/ad-cessna-400-77-aft-auxiliary-wing-spar-attachment-modification/history","analysis":"/api/acts/ad-cessna-400-77-aft-auxiliary-wing-spar-attachment-modification/analysis","conflicts":"/api/acts/ad-cessna-400-77-aft-auxiliary-wing-spar-attachment-modification/conflicts","importantCases":"/api/acts/ad-cessna-400-77-aft-auxiliary-wing-spar-attachment-modification/important-cases","documents":"/api/acts/ad-cessna-400-77-aft-auxiliary-wing-spar-attachment-modification/documents"}}