{"id":"F2006B10115","name":"AD/G21/1 - Below Floor Control System Components - Inspection","slug":"ad-g21-1-below-floor-control-system-components-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55643,"registerId":"commonwealth-F2006B10115-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/G21/1 - Below Floor Control System Components - Inspection","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)  Grumman G21 (Goose) Series Aeroplanes\n\n \n\nAD/G21/1 Below Floor Control System Components - Inspection\n\n\n10/77\n\n \n\nApplicability: All models.\n\n \n\nRequirement: 1. Remove and disassemble:\n\n \n\n(i)       Elevator Torque Tube Assembly P/N 12755,\n\n \n\n(ii)    Rudder Torque Tube Assembly P/N 12756,\n\n \n\n(iii)  Rudder Pedal Torque Tube Assembly LH and RH P/N 12757 and 12758,\n\n \n\n(iv)   Hinge Support Assembly P/N 12725.\n\n \n\n2. Inspect all parts for corrosion and/or cracks using visual and dye penetrant or magnetic particle techniques.\n\n \n\nNote: FAA AD 73-12-6 Amendment 39-1657 refers.\n\n \n\nCompliance: Initially before issue of Certificate of Airworthiness and there- after at intervals not exceeding 2000 hours time in service or two years whichever occurs first.\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 airworthiness directive with a narrow, specific purpose: inspecting control components on a single aircraft type. It has not expanded beyond its original safety intent."},"complexity_factors":["Very short document (under 300 words)","Only 4 specific part numbers listed for removal","Simple binary compliance trigger (time-based: 2000 hours OR 2 years)","No defined terms section","No cross-references to other Australian legislation (only mentions US FAA AD for context)","Single straightforward requirement with no exceptions or conditional logic"],"plain_english_summary":"This is a **safety directive for old seaplanes**. Specifically, it applies to all models of the **Grumman G21 'Goose'** — a vintage amphibious aircraft from the 1930s-40s.\n\n**What it requires:**\nOwners and operators must **periodically inspect critical control components** located beneath the aircraft floor. This involves:\n- **Removing and taking apart** four specific mechanical assemblies (elevator torque tubes, rudder torque tubes, rudder pedal assemblies, and hinge supports)\n- **Checking for corrosion and cracks** using visual inspection plus specialised crack-detection methods (dye penetrant or magnetic particle testing)\n\n**When it must be done:**\n- **First time:** Before the plane can get its airworthiness certificate\n- **Repeat:** Every **2,000 flight hours** or **2 years** — whichever comes first\n\n**Why it matters:**\nThese components control the plane's pitch (elevator) and yaw (rudder). If they fail due to corrosion or metal fatigue, the pilot could lose control. Given these aircraft are now 80+ years old and often operate in salty, corrosive marine environments, this directive prevents catastrophic accidents by catching metal fatigue before it causes structural failure.\n\nThe directive references an older American FAA safety order, showing Australia adopted this requirement from US aviation safety findings."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive as presented sets inspections for the listed parts across all models and specifies initial and recurring compliance intervals. The text contains no indication the instrument's scope was altered from its original stated purpose."},"complexity_factors":["Applicability to all models increases the number of affected aircraft (Applicability).","Specific parts with part numbers must be removed and disassembled (Requirement 1: P/N 12755, 12756, 12757, 12758, 12725).","Requires non‑destructive testing methods (visual plus dye penetrant or magnetic particle) rather than simple visual checks (Requirement 2).","Initial compliance required before Certificate of Airworthiness plus recurring interval (2000 hours or 2 years) imposes both pre‑certification and ongoing schedules (Compliance).","Disassembly and NDT create operational downtime and direct maintenance costs for operators; defects will trigger further repair or replacement.","Cross-reference to an FAA AD (Note) may require alignment with external service/inspection practices or records."],"plain_english_summary":"Requires removal, disassembly and non‑destructive inspection of below‑floor control components — elevator, rudder and rudder‑pedal torque tubes, and hinge support (specified part numbers) — for corrosion or cracks using visual, dye‑penetrant or magnetic‑particle methods.\n\nAffects operators and maintenance organisations of Grumman G21 (Goose) aircraft; inspections must be done before issue of the Certificate of Airworthiness and thereafter every 2,000 flight hours or two years (whichever occurs first). Operators pay for inspections and any rectification; the regulator enforces timing and compliance."}},"importantCases":[],"_links":{"self":"/api/acts/ad-g21-1-below-floor-control-system-components-inspection","history":"/api/acts/ad-g21-1-below-floor-control-system-components-inspection/history","analysis":"/api/acts/ad-g21-1-below-floor-control-system-components-inspection/analysis","conflicts":"/api/acts/ad-g21-1-below-floor-control-system-components-inspection/conflicts","importantCases":"/api/acts/ad-g21-1-below-floor-control-system-components-inspection/important-cases","documents":"/api/acts/ad-g21-1-below-floor-control-system-components-inspection/documents"}}