{"id":"F2006B09061","name":"AD/DHC-3/13 - Propeller Counterweight Bearing Shafts","slug":"ad-dhc-3-13-propeller-counterweight-bearing-shafts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52811,"registerId":"commonwealth-F2006B09061-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-3/13 - Propeller Counterweight Bearing Shafts","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-3 (Otter) Series Aeroplanes\n\n \n\nAD/DHC-3/13 Propeller Counterweight Bearing Shafts NK\n\nApplicability: All models fitted with 3D40-227 propellers. Requirement: Action in accordance with De H Canada EB “O” No 39.\n\nNote: Canadian AD 56-13 refers.\n\n \n\nCompliance: Before installation on an aircraft following each propeller reconditioning.\n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD's scope is limited to DHC-3 aeroplanes fitted with 3D40-227 propellers and requires action per De Havilland Canada EB \"O\" No. 39 before installation after each propeller reconditioning (\"Applicability\", \"Requirement\", \"Compliance\"). Nothing in the text indicates an expansion or narrowing of that scope from the instrument's stated applicability and compliance requirement."},"complexity_factors":["Narrow applicability (only DHC-3 models with 3D40-227 propellers) (\"Applicability\")","Single operative requirement that delegates technical detail to an external De Havilland Canada engineering bulletin (\"Requirement\")","Clear timing condition tied to propeller reconditioning and reinstallation (\"Compliance\")","Cross-reference to a foreign AD (Canadian AD 56-13) which may require checking another document (\"Note\")","Implementation depends on availability/clarity of the external bulletin, creating potential for interpretive variation (\"Requirement\")"],"plain_english_summary":"This AD requires DHC‑3 (Otter) aeroplanes fitted with 3D40‑227 propellers to have propeller counterweight bearing shaft work carried out in accordance with De Havilland Canada Engineering Bulletin \"O\" No. 39, and completed before a reconditioned propeller is reinstalled. \n\nIt affects DHC‑3 owners/operators and maintenance organisations; it alters the reinstallation sequence, may add labour/costs and delay returns to service, and relies on access to the cited bulletin."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow Airworthiness Directive targeting a specific technical issue on a specific aircraft/propeller combination. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (under 150 words)","Only one substantive requirement referencing an external technical document (De Havilland Canada EB 'O' No 39)","Single applicability criterion (3D40-227 propellers)","Single compliance trigger (before installation following reconditioning)","No defined terms section, no cross-references to other legislation beyond the note about Canadian AD 56-13","No conditional logic or nested exceptions"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to **DHC-3 Otter aircraft** (a type of Canadian-built bush plane) that are fitted with specific propellers (3D40-227 model).\n\n**What it requires:**\nWhenever a propeller is reconditioned (overhauled or repaired), the **propeller counterweight bearing shafts** must be inspected or dealt with according to instructions in a De Havilland Canada service bulletin called \"EB 'O' No 39\" before the propeller goes back on an aircraft.\n\n**Why it matters:**\nCounterweight bearing shafts are critical components that help balance the propeller. If they fail, the propeller could become unbalanced or fail entirely — potentially causing catastrophic damage to the engine or loss of control. This AD ensures a specific safety check happens at a specific time (after reconditioning, before reinstallation) to prevent accidents.\n\n**Who it affects:**\n- Owners and operators of DHC-3 Otter aircraft in Australia\n- Maintenance organisations that overhaul or recondition these propellers\n- CASA inspectors who enforce compliance\n\n**Key point:** This isn't optional — it's legally binding. Non-compliance means the aircraft isn't airworthy and cannot legally fly."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-3-13-propeller-counterweight-bearing-shafts","history":"/api/acts/ad-dhc-3-13-propeller-counterweight-bearing-shafts/history","analysis":"/api/acts/ad-dhc-3-13-propeller-counterweight-bearing-shafts/analysis","conflicts":"/api/acts/ad-dhc-3-13-propeller-counterweight-bearing-shafts/conflicts","importantCases":"/api/acts/ad-dhc-3-13-propeller-counterweight-bearing-shafts/important-cases","documents":"/api/acts/ad-dhc-3-13-propeller-counterweight-bearing-shafts/documents"}}