{"id":"F2006B09039","name":"AD/DHC-2/21 - Flight Controls, Elevator Root Rib - Inspection","slug":"ad-dhc-2-21-flight-controls-elevator-root-rib-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52745,"registerId":"commonwealth-F2006B09039-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-2/21 - Flight Controls, Elevator Root Rib - 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)  DHC-2 (Beaver) Series Aeroplanes\n\n \n\nAD/DHC-2/21 Flight Controls, Elevator Root Rib - Inspection 10/80\n\nApplicability: All Model DHC-2 Mk. I, Mk. II and Mk. III. Document:  De Havilland Aircraft of Canada SB No. 2/30.\n\nCompliance: Within 100 hours time in service after 31 December 1980 and thereafter at intervals not exceeding 400 hours time in service.\n\n \n\nBackground: Cracking of the elevator root rib at the torque tube attachment and cracking of the reinforcing doubler in the same area has been reported to the manufacturer.\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, single-issue safety directive from 1980 addressing a specific structural defect in a specific aircraft type. It has not expanded beyond its original purpose of mandating repetitive inspections for elevator root rib cracking."},"complexity_factors":["Extremely short document — approximately 150 words of substantive content","Only one defined term implicitly referenced ('time in service' — standard aviation term)","No cross-references to other legislation or regulations beyond the parenthetical mention of Civil Aviation Regulations 1998, Part 39","Single, straightforward compliance requirement with clear numerical thresholds (100 hours, 400 hours)","No conditional logic, exceptions, or alternative compliance methods","Simple applicability statement covering all variants of a single aircraft model"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific maintenance actions on aircraft.\n\n**What it does:**\nThis directive (AD/DHC-2/21) orders owners and operators of **De Havilland DHC-2 \"Beaver\" aircraft** (all Mark I, II, and III models) to inspect the **elevator root rib** — a structural part near where the elevator control surface attaches to the aircraft's tail.\n\n**Why it matters:**\nCracks had been found in this area, specifically at the torque tube attachment point and on a reinforcing doubler (a metal plate that strengthens the structure). Cracks in flight controls can lead to control failure, which is obviously catastrophic.\n\n**What must be done:**\n- **First inspection:** Within 100 hours of flying time after 31 December 1980\n- **Repeat inspections:** Every 400 hours of flying time thereafter\n\n**Who it affects:**\nAnyone operating these specific Canadian-built bush planes in Australia — common in remote and regional aviation.\n\n**Key point:** This is not optional. Airworthiness Directives are legally binding safety mandates. Ignoring them means the aircraft cannot legally fly."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive's scope, as presented in the text, aligns with its stated purpose: to detect reported cracking at the elevator root rib/torque tube attachment and the reinforcing doubler on all DHC-2 Mk I/II/III aircraft. It prescribes a mandatory inspection schedule and refers to the manufacturer's service bulletin for action. The text does not expand the scope beyond inspection for that specific defect."},"complexity_factors":["Narrow and specific applicability: applies only to DHC-2 Mk I, II and III (Applicability).","Simple, fixed compliance timing: initial inspection within 100 hours after a date, then every 400 hours (Compliance).","Technical inspection requirement referencing a manufacturer service bulletin rather than prescribing detailed procedures in the directive (Document).","No additional regulatory options or complex conditional tests in the text—directive mandates inspection only (Compliance/Background).","Potential implementation dependence on maintenance quality and the referenced SB, not detailed in the AD (Document)."],"plain_english_summary":"What this instrument changes, mechanically:\n\n- It makes inspection of the elevator root rib mandatory for all De Havilland DHC-2 (Beaver) Mk I, Mk II and Mk III aeroplanes. (Applicability: \"All Model DHC-2 Mk. I, Mk. II and Mk. III.\")\n- The first inspection must be done within 100 hours time in service after 31 December 1980 and then repeated at intervals not exceeding 400 hours time in service. (Compliance: \"Within 100 hours time in service after 31 December 1980 and thereafter at intervals not exceeding 400 hours time in service.\")\n- The directive refers operators and maintainers to a manufacturer document for details: De Havilland Aircraft of Canada SB No. 2/30. (Document: \"De Havilland Aircraft of Canada SB No. 2/30.\")\n\nWhy it was issued (as stated):\n\n- The directive states cracking has been reported in the elevator root rib at the torque tube attachment and cracking of the reinforcing doubler in the same area. (Background: \"Cracking of the elevator root rib at the torque tube attachment and cracking of the reinforcing doubler in the same area has been reported to the manufacturer.\")\n\nWho is affected and who decides:\n\n- Aircraft owners and operators of DHC-2 Mk I/II/III are required to comply with the inspection schedule. (Applicability/Compliance.)\n- The Civil Aviation Safety Authority issued the airworthiness directive under the Part 39 schedule of airworthiness directives. (Header: \"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY / SCHEDULE OF AIRWORTHINESS DIRECTIVES\")\n\nMechanics of incentives, costs and implementation risks (grounded in the text):\n\n- Compliance imposes direct maintenance actions on operators: periodic inspections at the specified intervals, using the referenced De Havilland service bulletin for procedure. (Compliance; Document.) This translates to time in service lost to inspection and likely labour and parts costs if defects are found.\n- The directive is narrowly targeted at a specific structural location (elevator root rib/torque tube attachment and its doubler). That concentrates the inspection effort on a defined part rather than on whole-aircraft overhaul. (Background; Applicability.)\n- The text does not set out mandatory repair instructions or limits; it prescribes inspection timing and points to the manufacturer bulletin for action details. The absence of repair steps in the directive means operators must follow the SB or established maintenance practices to decide corrective work. (Document; Compliance.)\n- Implementation depends on inspectors/maintainers correctly following the referenced service bulletin and on operators meeting the time-in-service intervals; effectiveness therefore rests on maintenance quality and record keeping. (Document; Compliance.)\n\nTrade-offs and likely practical effects (based on the directive's mechanics):\n\n- The measure raises ongoing maintenance burden for affected aircraft owners/operators through recurring inspections and any subsequent rectification work. (Compliance.)\n- It targets a safety risk reported to the manufacturer; the mechanism prioritises detection by inspection rather than, for example, grounding or mandatory component replacement. (Background; Compliance.)\n- Because the directive applies to all DHC-2 Mk I/II/III aircraft, the burden is broadly distributed across operators of these types, while the problem being inspected is a structurally localised cracking issue. (Applicability; Background.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-2-21-flight-controls-elevator-root-rib-inspection","history":"/api/acts/ad-dhc-2-21-flight-controls-elevator-root-rib-inspection/history","analysis":"/api/acts/ad-dhc-2-21-flight-controls-elevator-root-rib-inspection/analysis","conflicts":"/api/acts/ad-dhc-2-21-flight-controls-elevator-root-rib-inspection/conflicts","importantCases":"/api/acts/ad-dhc-2-21-flight-controls-elevator-root-rib-inspection/important-cases","documents":"/api/acts/ad-dhc-2-21-flight-controls-elevator-root-rib-inspection/documents"}}