{"id":"F2006B08879","name":"AD/DH 104/36 - Engine Mounting Frame Front Engine Support Spigots - Inspection","slug":"ad-dh-104-36-engine-mounting-frame-front-engine-support-spigots-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52348,"registerId":"commonwealth-F2006B08879-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DH 104/36 - Engine Mounting Frame Front Engine Support Spigots - 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)  DH 104 (Dove) Series Aeroplanes\n\n \n\n# AD/DH 104/36 Engine Mounting Frame Front Engine\n\nSupport Spigots - Inspection Applicability: All models equipped with front engine support spigot P/N 4EM.681. Document:               British Aerospace TNS Dove (104) No. 244 Issue 2.\n\nCompliance: Before 15 September 1981.\n\n# 5/81\n\n \n\nBackground: A case has been reported to the manufacturer where the front engine support spigot, on an engine mounting frame, was found fractured.\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":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive’s scope is limited to inspection of front engine support spigot P/N 4EM.681 on DH 104 (Dove) series aeroplanes and sets a one-off compliance deadline. The text supplied shows no change from that expressed intent: it prescribes inspection of the specified part by the stated date and references the manufacturer’s inspection procedure."},"complexity_factors":["Narrow technical scope: single aircraft family and single part number (Applicability).","Fixed, short-term compliance deadline (Compliance).","Dependence on an external manufacturer technical note for the inspection procedure (Document).","Limited regulatory text: requirement is a one-off inspection rather than an ongoing programme.","Operational logistics: arranging access, personnel and possible disassembly to inspect the spigot (implied implementation complexity)."],"plain_english_summary":"What this instrument does (mechanically)\n\n- Requires an inspection of the front engine support spigot with part number P/N 4EM.681 fitted to the engine mounting frame on DH 104 (Dove) series aeroplanes (Applicability).\n- Directs that the inspection be carried out in accordance with the referenced manufacturer document: British Aerospace TNS Dove (104) No. 244 Issue 2 (Document).\n- Sets a mandatory deadline for compliance: the inspection must be completed before 15 September 1981 (Compliance).\n\nWhy it was issued (official rationale, as stated)\n\n- The directive was issued because a fractured front engine support spigot was reported to the manufacturer (Background). The stated purpose is to identify any similar defects before they cause a structural failure.\n\nWho it affects and who pays\n\n- Affected parties: owners/operators of DH 104 (Dove) series aeroplanes that are fitted with front engine support spigot P/N 4EM.681 (Applicability).\n- Who pays: the operator or owner must arrange and fund the inspection (implicit from the Applicability/Compliance requirement to have the work done by the compliance date).\n\nHow it works in practice and what it requires from operators\n\n- Operators must obtain and follow the inspection procedure set out in British Aerospace TNS Dove (104) No. 244 Issue 2 (Document).\n- The action is a one-off mandatory inspection required before the stated deadline (Compliance).\n\nIncentives, costs and trade-offs (mechanical and economic effects)\n\n- Incentives: the AD creates a clear, time-bound incentive for operators to inspect the specified spigot to avoid operating with a potentially fractured component (Applicability; Compliance).\n- Direct compliance cost: time, labour and any access/disassembly required to inspect the spigot; costs are borne by the aircraft owner/operator (Applicability; Compliance).\n- Implementation dependency: the inspection procedure is specified by the manufacturer’s technical note; operators must obtain and follow that document to meet the AD (Document). If the procedure requires specialised tooling or approved maintenance organisation work, that increases cost and scheduling complexity (inference from the reliance on the manufacturer document).\n- Opportunity cost: resources (hangar time, maintenance slots, technician hours) devoted to this inspection cannot be used for other maintenance or commercial flying until completed.\n\nCompliance burden and administrative discretion\n\n- Compliance burden is narrowly targeted: a single inspection on aircraft that have the specific spigot fitted (Applicability). The AD sets a fixed deadline, leaving little administrative discretion about timing (Compliance).\n- The directive relies on the Civil Aviation Safety Authority’s Schedule of Airworthiness Directives as the regulatory vehicle (header). The AD itself prescribes the action and deadline; it does not set out discretionary waivers or alternatives in the text provided.\n\nEffects on private enterprise and markets\n\n- Maintenance providers may receive work to perform the inspection; small, short-term demand for maintenance services could result for affected aircraft (inference from the inspection requirement and Document).\n- The requirement imposes compliance costs on owners/operators which can affect operational availability and short-term productivity for the affected aircraft fleet (Compliance).\n\nTrade-offs and risk\n\n- Benefit mechanism: detecting fractured or cracked spigots before failure reduces the risk of structural/engine support failure (Background).\n- Trade-off: the safety benefit is balanced against the direct cost and operational disruption of performing the inspections before the deadline.\n- Implementation risk: if operators do not obtain or correctly apply the referenced manufacturer procedure, the inspection may not detect defects; the AD’s effectiveness therefore depends on faithful use of the referenced technical note (Document).\n\nScope and limits\n\n- The AD is narrowly scoped to a single part number and a specific aircraft family (Applicability). It does not, in the text provided, mandate replacement or recurring inspections; it mandates a one-time inspection by a fixed date (Compliance).\n\nReferences to the source text\n\n- Applicability: “All models equipped with front engine support spigot P/N 4EM.681.”\n- Document: “British Aerospace TNS Dove (104) No. 244 Issue 2.”\n- Compliance: “Before 15 September 1981.”\n- Background: “A case has been reported to the manufacturer where the front engine support spigot, on an engine mounting frame, was found fractured.”"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive issued in 1981 with a specific safety purpose. It has not expanded beyond its original intent — it addresses one reported defect in one aircraft type with one required action. Airworthiness directives are typically narrow by design and this exemplifies that approach."},"complexity_factors":["Single, specific technical requirement (one inspection task)","Narrow applicability (one aircraft series, one specific part number)","No defined terms section or interpretation provisions","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","Simple conditional structure: if you have this aircraft with this part, you must inspect by this date","No exceptions, exemptions, or nested conditions","Length: approximately 150 words of substantive content"],"plain_english_summary":"This is an **Airworthiness Directive** (a mandatory safety order) issued by Australia's Civil Aviation Safety Authority for a specific type of aircraft: the **DH 104 Dove series** (a British twin-engine propeller plane from the 1940s-60s).\n\n**What it requires:**\n- Owners and operators must inspect the **front engine support spigots** (metal mounting points that hold the engine to the airframe) on all Dove aircraft fitted with part number **4EM.681**\n- The inspection must be completed **before 15 September 1981**\n\n**Why it matters:**\n- A fractured (cracked/broken) engine support spigot was reported to the manufacturer. If this part fails in flight, the engine could detach from the wing — a catastrophic safety risk.\n- This directive forces operators to check for this specific defect before the deadline to prevent accidents.\n\n**Who it affects:**\n- Anyone operating or maintaining DH 104 Dove aircraft in Australia with the specified part installed.\n\nThis is a **time-critical safety mandate** — not optional. Non-compliance would mean the aircraft cannot legally fly."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dh-104-36-engine-mounting-frame-front-engine-support-spigots-inspection","history":"/api/acts/ad-dh-104-36-engine-mounting-frame-front-engine-support-spigots-inspection/history","analysis":"/api/acts/ad-dh-104-36-engine-mounting-frame-front-engine-support-spigots-inspection/analysis","conflicts":"/api/acts/ad-dh-104-36-engine-mounting-frame-front-engine-support-spigots-inspection/conflicts","importantCases":"/api/acts/ad-dh-104-36-engine-mounting-frame-front-engine-support-spigots-inspection/important-cases","documents":"/api/acts/ad-dh-104-36-engine-mounting-frame-front-engine-support-spigots-inspection/documents"}}