{"id":"F2006B08876","name":"AD/DH 104/33 - Nose Undercarriage Inner Casing - Inspection and Replacement","slug":"ad-dh-104-33-nose-undercarriage-inner-casing-inspection-and-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52300,"registerId":"commonwealth-F2006B08876-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DH 104/33 - Nose Undercarriage Inner Casing - 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\nAD/DH 104/33 Nose Undercarriage Inner Casing - Inspection\n\nand Replacement\n\n\n10/73\n\n \n\nApplicability: All models.\n\n \n\nDocument: Hawker Siddeley TNS CT(104) No. 232.\n\n \n\nCompliance: 1. Inspect casing in accordance with paras. 3.5 and 4.1 of TNS CT(104) No. 232 within 50 hours time in service after 29 October 1973 and thereafter at intervals not exceeding 600 hours time in service and after any reported heavy landings.\n\n \n\n2. Replace casing in accordance with para. 3.2 of TNS CT(104) No. 232 before 17 March 1975.\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":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The text does not indicate any change from a prior stated intent; it sets mandatory inspections and a replacement date for the nose undercarriage inner casing for all DH 104 models, referencing Hawker Siddeley TNS CT(104) No. 232 and specifying the required timing. There is no language in the instrument suggesting an expanded or narrowed scope relative to an earlier instrument within the provided text."},"complexity_factors":["Short, prescriptive requirements (initial inspection, recurring interval, replacement deadline) reduce procedural complexity.","Critical reliance on an external technical document (Hawker Siddeley TNS CT(104) No. 232) for the detailed inspection and replacement steps increases implementation dependency.","Subjective term \"heavy landings\" requires operator judgment and may produce inconsistent application.","Timekeeping requirement (hours time in service thresholds and a fixed calendar replacement deadline) imposes administrative tracking.","No alternative compliance paths or enforcement mechanisms are specified in the text, leaving practical follow‑up to operators and regulators."],"plain_english_summary":"What this instrument does (mechanically)\n\n- Requires operators of DH 104 (Dove) series aeroplanes to follow a specific inspection and replacement regime for the nose undercarriage inner casing. (Applicability; Document; Compliance 1–2)\n- Specifically: carry out an initial inspection per paragraphs 3.5 and 4.1 of Hawker Siddeley TNS CT(104) No. 232 within 50 hours time in service after 29 October 1973, then re‑inspect at intervals not exceeding 600 hours time in service and after any reported heavy landings. (Compliance 1)\n- Also requires replacement of the casing in accordance with paragraph 3.2 of the Hawker Siddeley document before 17 March 1975. (Compliance 2)\n\nWho is affected\n\n- All operators/owners of DH 104 (Dove) series aircraft. (Applicability)\n- Maintenance organisations and technicians who perform inspections and replacements under the referenced Hawker Siddeley procedure. (Document)\n\nWhy it matters (stated purpose and operational effects)\n\n- The directive ties mandatory maintenance actions to a manufacturer’s technical instruction (Hawker Siddeley TNS CT(104) No. 232) and sets specific timing requirements. (Document; Compliance 1–2)\n- Mechanically, it changes operator behaviour by imposing: (a) short‑term scheduling for an initial inspection (50 flight hours after 29 Oct 1973), (b) an ongoing inspection cadence (every 600 hours or after heavy landings), and (c) a hard deadline for part replacement (before 17 Mar 1975). (Compliance 1–2)\n\nWho pays, who decides, and how behaviour changes\n\n- Operators/owners pay for inspections, any required repairs, the replacement casing and associated labour and aircraft downtime. (Compliance 1–2)\n- Operators and their maintenance providers decide how to schedule the inspections and replacement so that the timing requirements and reference paragraphs in TNS CT(104) No. 232 are met. (Document; Compliance 1–2)\n- Behaviour changes include logging time in service to meet the hour thresholds, performing inspections after any reported heavy landing, and completing the mandated replacement by the specified date. (Compliance 1–2)\n\nCompliance burden, implementation risks and discretionary points\n\n- Compliance burden: recurring inspections (initial within 50 hours, then ≤600‑hour intervals) create recurring labour and downtime costs; a compulsory replacement by a fixed date creates a near‑term capital and scheduling cost. (Compliance 1–2)\n- Implementation risks: the directive relies on the operator’s interpretation of “heavy landings” and on access to the referenced Hawker Siddeley paragraphs for the detailed procedure; those two features can create variability in practical application. (Compliance 1; Document)\n- Discretion: the text mandates actions per the referenced manufacturer paragraphs and sets deadlines and intervals; it does not provide exemptions, alternative compliance routes or enforcement details in the text provided. (Document; Compliance 1–2)\n\nTrade-offs and market effects to note (mechanisms, not judgments)\n\n- Short term: operators incur scheduling and parts costs and may reduce flying until replacement is done. (Compliance 1–2)\n- Medium term: maintenance demand (parts, labour) for this specific casing will rise for affected aircraft while the replacement deadline and ongoing inspection cadence are in force. (Compliance 1–2)\n- The directive concentrates obligations on the owners/operators of the specified aircraft model; any economic effects (costs, scheduling) fall to them and to maintenance suppliers they engage. (Applicability; Compliance 1–2)\n\nKey source references within the instrument\n\n- Applicability: \"All models.\" (Applicability)\n- Action instructions reference: Hawker Siddeley TNS CT(104) No. 232. (Document)\n- Inspection timing and intervals: Compliance paragraph 1. (Compliance 1)\n- Replacement requirement and deadline: Compliance paragraph 2. (Compliance 2)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused specifically on nose undercarriage casing inspection and replacement for one aircraft type. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 defined compliance requirements (inspection and replacement)","Single cross-reference to manufacturer technical document (TNS CT(104) No. 232)","No nested exceptions or conditional logic beyond standard time-in-service intervals","Clear applicability statement ('All models')","Straightforward deadline structure (specific dates and hour limits)"],"plain_english_summary":"This is an **Airworthiness Directive** (a mandatory safety order) issued by Australia's Civil Aviation Safety Authority for **DH 104 Dove series aircraft** — a type of twin-engine propeller plane.\n\n**What it requires:**\n- **Inspection:** Aircraft operators must check the nose undercarriage (front landing gear) inner casing for cracks or damage within 50 flying hours after 29 October 1973, then repeat this inspection every 600 flying hours, and also after any hard landings.\n- **Replacement:** The casing must be completely replaced before 17 March 1975, following specific technical instructions from the manufacturer (Hawker Siddeley).\n\n**Who it affects:**\n- Owners and operators of all DH 104 Dove aircraft models\n- Maintenance engineers working on these planes\n\n**Why it matters:**\nThe nose undercarriage inner casing is a critical structural component. If it fails, the front landing gear could collapse during takeoff or landing, potentially causing a serious accident. This directive forces operators to proactively inspect and replace this part before it becomes dangerous."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dh-104-33-nose-undercarriage-inner-casing-inspection-and-replacement","history":"/api/acts/ad-dh-104-33-nose-undercarriage-inner-casing-inspection-and-replacement/history","analysis":"/api/acts/ad-dh-104-33-nose-undercarriage-inner-casing-inspection-and-replacement/analysis","conflicts":"/api/acts/ad-dh-104-33-nose-undercarriage-inner-casing-inspection-and-replacement/conflicts","importantCases":"/api/acts/ad-dh-104-33-nose-undercarriage-inner-casing-inspection-and-replacement/important-cases","documents":"/api/acts/ad-dh-104-33-nose-undercarriage-inner-casing-inspection-and-replacement/documents"}}