{"id":"F2006B02203","name":"AD/AC-SNOW/12 - Rudder Control Surface Upper Hinge - Inspection and Modification","slug":"ad-ac-snow-12-rudder-control-surface-upper-hinge-inspection-and-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41433,"registerId":"commonwealth-F2006B02203-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AC-SNOW/12 - Rudder Control Surface Upper Hinge - Inspection and Modification","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nAyres Thrush (Snow) Commander Series Aeroplanes\n\nAD/AC-SNOW/12 Rudder Control Surface Upper\n\nHinge \\- Inspection and Modification\n\n  \n6/79\n\nApplicability: All model S-2D and S-2R with rudder assembly with single upper hinge P/N 54030- 87.\n\nRequirement: To prevent the possible separation of the single upper hinge from the rudder assembly accomplish the following:\n\n    (a) Remove rudder assembly from aeroplane.\n\n    (b) Strip fabric and dope from area around upper hinge.\n\n    (c) Inspect with 10X glass in and around weld head on upper hinge attachment for cracks.\n\n    (d) If cracks are discovered comply with para. 2.\n\n    2. If cracks are discovered in the upper hinge area comply with one of the following options:\n\n    (a) Replace rudder ith rudder P/N 54030-987 having triple upper hinges.\n\n    (b) Modify existing rudder P/N 54030-87 by installing Ayres Custom Kit No.\n\nCK-AG-18; or\n\n    (c) Replace defective rudder P/N 54030-87 with serviceable rudder P/N 54030- 87.\n\nNote: FAA AD 79-10-10 Amendment 39-3469 refers to this subject.\n\nCompliance: 1. Within 100 hours’ time in service after 31 July 1979 and thereafter at intervals not exceeding 100 hours’ time in service until para. 2(a) or (b) accomplished.\n\n2. Modify in accordance with para. 2(a) or (b) not later than 300 hours’ time in service after 31 July 1979.\n\nBackground: There are three reports of failures of the single upper hinge type rudders on overseas aeroplanes.","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"},"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 preventing rudder hinge failures."},"complexity_factors":["Single, clearly defined applicability (two specific aircraft models with one specific part number)","Straightforward sequential requirements (inspect first, then modify if needed)","Only three compliance paths with clear alternatives (replace, modify, or swap)","Simple time-based compliance framework (100-hour and 300-hour intervals)","No nested definitions, cross-references to other legislation, or conditional exceptions","Minimal legal drafting — reads more like a maintenance manual than statute"],"plain_english_summary":"Australia's CASA has issued a mandatory Airworthiness Directive for Ayres Thrush S-2D/S-2R crop-dusters with the single upper rudder hinge (P/N 54030‑87) after hinge cracking and separations overseas. Owners must inspect the hinge every 100 flight hours (first inspection by late 1979) and, if cracks are found, within 300 hours either fit a triple‑hinge rudder, install a reinforcement kit, or replace with a serviceable rudder. Compliance is mandatory under aviation law."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The directive applies specifically to S-2D and S-2R aeroplanes fitted with rudder P/N 54030-87 and prescribes inspection and remedial choices to prevent upper-hinge separation. The source text sets applicability and corrective measures; it does not indicate any expansion or narrowing of that applicability beyond the models and part-number listed, so no change in scope from the instrument's stated purpose is evident."},"complexity_factors":["Applicability limited to specific airframe models and a single part number (Applicability).","Task requires removal of the rudder and stripping fabric/dope before inspection, increasing labour and downtime (Requirement (a)–(b)).","Inspection uses 10X magnification to detect cracks, a technical inspection standard (Requirement (c)).","Multiple remedial options: replace with alternate P/N, modify with a kit, or replace with a serviceable identical P/N (Requirement 2(a)–(c)), creating choices for operators and supply-chain dependence on parts/kits.","Interim recurring inspections mandated until modification is done, with specified time-in-service intervals (Compliance para. 1), raising ongoing compliance burden until permanent fix.","A firm modification deadline is imposed (300 hours TIS after 31 July 1979) which creates a bounded planning horizon for operators (Compliance para. 2).","Safety rationale is event-driven and narrow: based on three overseas failure reports (Background), concentrating the directive on a particular failure mode and subset of aircraft."],"plain_english_summary":"This airworthiness directive requires owners/operators of Ayres Thrush (Snow) Commander S-2D and S-2R aircraft fitted with the single-upper-hinge rudder P/N 54030-87 to remove the rudder, strip surrounding fabric/dope and inspect the upper-hinge weld for cracks; if cracks are found they must replace or modify the rudder by one of the prescribed options. The measure is aimed at preventing possible separation of the upper hinge following reported failures and imposes inspection and modification deadlines on operators."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ac-snow-12-rudder-control-surface-upper-hinge-inspection-and-modification","history":"/api/acts/ad-ac-snow-12-rudder-control-surface-upper-hinge-inspection-and-modification/history","analysis":"/api/acts/ad-ac-snow-12-rudder-control-surface-upper-hinge-inspection-and-modification/analysis","conflicts":"/api/acts/ad-ac-snow-12-rudder-control-surface-upper-hinge-inspection-and-modification/conflicts","importantCases":"/api/acts/ad-ac-snow-12-rudder-control-surface-upper-hinge-inspection-and-modification/important-cases","documents":"/api/acts/ad-ac-snow-12-rudder-control-surface-upper-hinge-inspection-and-modification/documents"}}