{"id":"F2006B08874","name":"AD/DH 104/31 - Drag Bracing Member, Centre Section Spar Lower Boom - Inspection and Replacement","slug":"ad-dh-104-31-drag-bracing-member-centre-section-spar-lower-boom-inspection-and-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52298,"registerId":"commonwealth-F2006B08874-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DH 104/31 - Drag Bracing Member, Centre Section Spar Lower Boom - Inspection and Replacement","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)  DH 104 (Dove) Series Aeroplanes\n\n \n\n# AD/DH 104/31 Drag Bracing Member, Centre Section Spar\n\nLower Boom - Inspection and Replacement\n\nApplicability: All models.\n\n \n\nDocument: Hawker Siddeley TNS CT(104) No. 230.\n\n# 5/73\n\n \n\nCompliance: 1. Inspect fittings in accordance with para. 4 of TNS CT(104) No. 230 within 100 hours time in service after 29 June 1973 or before 1 August 1973 whichever occurs first.\n\n \n\n2. Replace fittings in accordance with para. 5 of TNS CT(104) No. 230 before 1 July 1974.\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 historical Airworthiness Directive from 1973 with a narrow, specific scope: addressing a known structural defect in a particular aircraft type. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (approximately 200 words)","Only 2 compliance requirements with clear deadlines","Single defined technical reference (Hawker Siddeley TNS CT(104) No. 230)","No nested exceptions or conditional logic beyond simple date/hours alternatives","Straightforward applicability (all models of one aircraft type)","No cross-references to other legislation or regulations beyond the enabling Civil Aviation Regulations 1998"],"plain_english_summary":"This is an **Airworthiness Directive** (AD) — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\nThis directive requires owners and operators of **DH 104 (Dove) series aeroplanes** — a British twin-engine aircraft from the 1940s-60s — to inspect and potentially replace a specific structural part called the **\"drag bracing member\"** located at the **centre section spar lower boom**. This is a critical wing structure component.\n\n**Who it affects:**\n- Anyone who owns or operates a DH 104 Dove aircraft in Australia\n- Maintenance engineers working on these aircraft\n\n**What must be done:**\n1. **Inspection:** Within 100 flight hours after 29 June 1973 **or** before 1 August 1973 (whichever comes first), inspect the fittings following the technical instructions in Hawker Siddeley document TNS CT(104) No. 230, paragraph 4.\n\n2. **Replacement:** If needed, replace the fittings following paragraph 5 of that same technical document — and this must be completed before 1 July 1974.\n\n**Why it matters:**\nAirworthiness Directives are legally binding safety instructions. Failing to comply means the aircraft cannot legally fly. This particular AD addresses potential structural failures in the wing spar — a critical safety issue that could lead to catastrophic wing failure if not addressed."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The text itself sets out its scope clearly: it applies to all DH 104 models and mandates inspection and replacement per the referenced technical note with specific deadlines. The directive does not indicate any change to that scope within the text provided."},"complexity_factors":["Cross-reference to an external technical document (TNS CT(104) No. 230 paras 4 and 5) for procedural detail increases reliance on that document.","Two different deadlines and a hybrid time-or-calendar requirement for inspection (100 hours after 29 June 1973 or before 1 August 1973, whichever occurs first) add scheduling complexity for operators. (Compliance para. 1)","A later absolute date for replacement (before 1 July 1974) requires planning for parts and labour within a firm timeframe. (Compliance para. 2)","Applicability to all models concentrates the obligation across the entire DH 104 fleet but does not differentiate by configuration or usage, which can simplify scope but may overlook model-specific differences. (Applicability)","The AD contains no enforcement, cost, or alternative-compliance detail in the text provided, requiring operators to consult the referenced technical note and regulatory authority for further guidance. (Document reference)"],"plain_english_summary":"What this directive does (mechanically)\n\n- This is an airworthiness directive issued under the Commonwealth Civil Aviation Regulations (Part 39, Schedule of Airworthiness Directives) that applies to the DH 104 (Dove) series aeroplanes (Applicability: All models). (Applicability)\n- It requires operators to inspect specific fittings of the drag bracing member on the centre section spar lower boom according to paragraph 4 of the manufacturer/technical document TNS CT(104) No. 230. The inspection must be done within 100 hours time in service after 29 June 1973 or before 1 August 1973, whichever comes first. (Compliance: para. 1; Document reference)\n- It also requires replacement of the fittings in accordance with paragraph 5 of TNS CT(104) No. 230, to be completed before 1 July 1974. (Compliance: para. 2; Document reference)\n\nWho is affected and who decides\n\n- Aircraft owners/operators of DH 104 (Dove) series aeroplanes must carry out the mandated inspections and replacements. (Applicability; Compliance paras 1–2)\n- The directive cross‑references the technical instructions in TNS CT(104) No. 230 (paras 4 and 5) for how to inspect and replace the fittings; those technical procedures are the required method. (Document reference)\n- The directive is issued under the Commonwealth Civil Aviation Regulations, Part 39 (Civil Aviation Safety Authority schedule), which is the legal instrument creating the obligation. (Header)\n\nWhy it matters (stated purpose and practical implications)\n\n- The title and requirements identify the subject as the drag bracing member, centre section spar lower boom. The directive therefore directs inspection and replacement of those fittings so that those specific structural fittings are checked and, where required by the referenced procedures, replaced. (Title; Compliance)\n\nCosts, incentives, trade-offs and who pays\n\n- The text requires action by operators; it therefore places the direct cost and operational burden of the inspection and the subsequent replacement on aircraft owners/operators or their maintenance providers. The AD itself does not specify funding or compensation. (Compliance paras 1–2)\n- Because the AD mandates compliance with the procedures set out in TNS CT(104) No. 230 (paras 4 and 5), operators have an incentive to engage qualified maintenance personnel who can follow that document. (Document reference)\n\nCompliance burden, timing and implementation risks\n\n- The compliance requirements impose fixed deadlines: an inspection window (100 hours in service after 29 June 1973 or before 1 August 1973, whichever is earlier) and a replacement deadline (before 1 July 1974). Operators must schedule maintenance to meet those deadlines. (Compliance paras 1–2)\n- The AD delegates technical detail to the referenced technical note (TNS CT(104) No. 230, paras 4 and 5). The AD does not itself contain inspection/removal/replacement procedures, so compliance depends on access to and application of that external document. (Document reference)\n- The directive does not specify enforcement measures, costs, or acceptable alternatives in the text provided. (Compliance)\n\nEffect on private service providers and market choices\n\n- The AD requires a specific inspection and replacement procedure; independent maintenance organisations and contracted technicians can perform the work provided they use the referenced procedures. The text does not restrict who may perform the work. (Document reference)\n\nSummary in one line\n\n- Operators of DH 104 (Dove) aeroplanes must inspect the centre section spar lower boom drag bracing member fittings per TNS CT(104) No. 230 within the stated short inspection window, and must replace those fittings per the same technical note by the stated replacement deadline. (Applicability; Compliance; Document reference)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-dh-104-31-drag-bracing-member-centre-section-spar-lower-boom-inspection-and-replacement","history":"/api/acts/ad-dh-104-31-drag-bracing-member-centre-section-spar-lower-boom-inspection-and-replacement/history","analysis":"/api/acts/ad-dh-104-31-drag-bracing-member-centre-section-spar-lower-boom-inspection-and-replacement/analysis","conflicts":"/api/acts/ad-dh-104-31-drag-bracing-member-centre-section-spar-lower-boom-inspection-and-replacement/conflicts","importantCases":"/api/acts/ad-dh-104-31-drag-bracing-member-centre-section-spar-lower-boom-inspection-and-replacement/important-cases","documents":"/api/acts/ad-dh-104-31-drag-bracing-member-centre-section-spar-lower-boom-inspection-and-replacement/documents"}}