{"id":"F2006B02554","name":"AD/AT/5 - Engine Mount Ring on Vibro-Damp Mount Assembly - Inspection","slug":"ad-at-5-engine-mount-ring-on-vibro-damp-mount-assembly-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41810,"registerId":"commonwealth-F2006B02554-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AT/5 - Engine Mount Ring on Vibro-Damp Mount Assembly - 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)  Airtractor AT-300, 400 and 500 Series Aeroplanes\n\n \n\nAD/AT/5 Engine Mount Ring on Vibro-Damp Mount Assembly - Inspection\n\nApplicability: All models AT-300 and AT-301.\n\n \n\nDocument: Snow Engineering Co. Service Letter No. 50.\n\n \n\nCompliance: 1. Within 100 hours time in service after 31st July 1983 and thereafter as per requirement document.\n\n \n\n2. Repeat bolt removal at each 1000 hours time in service.\n\n \n\nBackground: The manufacturer reports cracking of attach brackets and excessive wear of attachment bolts.\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\n7/83\n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive’s scope, as given in the text, covers all Airtractor AT-300 and AT-301 models and specifies inspection and bolt-removal intervals. The AD does not indicate any change from a prior or different scope within the document itself; it sets a narrow, model-specific inspection requirement and defers procedural detail to the referenced service letter (Applicability; Document; Compliance)."},"complexity_factors":["Narrow applicability limited to two aircraft models (AT-300 and AT-301) — reduces scope complexity (Applicability).","Simple, time-based compliance schedule with two clear items: initial inspection within 100 hours and bolt removal every 1,000 hours — straightforward to schedule (Compliance paragraphs 1–2).","Dependence on an external document (Snow Engineering Co. Service Letter No. 50) for procedural detail and ongoing requirements introduces an external dependency and potential ambiguity (Document; Compliance paragraph 1).","Background identifies the defect (cracking and bolt wear) but the AD does not specify corrective actions or acceptance criteria — those are deferred to the service letter, increasing practical complexity for operators who must obtain and interpret that document (Background; Document).","Historical dating (initial compliance tied to 31 July 1983) makes the instrument procedural and retrospective; modern interpretation may require cross-checking records, but the AD text itself is concise."],"plain_english_summary":"This directive requires Airtractor AT-300 and AT-301 owners/operators to inspect the engine mount ring on the vibro-damp mount assembly per Snow Engineering Co. Service Letter No. 50 — initially within 100 hours TIS after 31 July 1983 and thereafter per the service-letter schedule, with bolt removal for inspection every 1,000 hours.\n\nIt responds to reported bracket cracking and bolt wear, shifting recurring labour, downtime and repair costs onto operators to mitigate those safety risks."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive from 1983 addressing a specific mechanical defect in specific aircraft models. It has not expanded beyond its original narrow safety purpose."},"complexity_factors":["Single, specific mechanical component addressed (engine mount ring on one aircraft series)","Only two compliance requirements: initial inspection at 100 hours and recurring inspection at 1000 hours","No defined terms section — uses plain language and references external technical document","No conditional logic, exceptions, or nested provisions","Extremely short document (approximately 150 words of substantive content)","Single applicability criterion (two specific aircraft models)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) under the Civil Aviation Regulations 1998.\n\n**What it does:**\nThis directive requires owners and operators of specific Air Tractor crop-dusting aeroplanes (AT-300 and AT-301 models) to inspect the **engine mount ring** — the metal structure that attaches the engine to the airframe via a vibration-dampening system.\n\n**Who it affects:**\n- Owners and operators of Air Tractor AT-300 and AT-301 agricultural aircraft\n- Maintenance engineers responsible for keeping these planes airworthy\n\n**What must be done:**\n1. **Initial inspection:** Within 100 flight hours after 31 July 1983, inspect the engine mount ring following Snow Engineering Service Letter No. 50\n2. **Ongoing checks:** Every 1,000 flight hours thereafter, remove and inspect the attachment bolts\n\n**Why it matters:**\nThe manufacturer discovered **cracking in attach brackets** and **excessive wear on bolts** — defects that could cause the engine to detach from the airframe in flight, with catastrophic consequences. This AD makes inspection mandatory (not optional) to prevent engine separation accidents.\n\n**Key point:** Unlike a service bulletin (which is advisory), an Airworthiness Directive is **legally enforceable**. Non-compliance grounds the aircraft."}},"importantCases":[],"_links":{"self":"/api/acts/ad-at-5-engine-mount-ring-on-vibro-damp-mount-assembly-inspection","history":"/api/acts/ad-at-5-engine-mount-ring-on-vibro-damp-mount-assembly-inspection/history","analysis":"/api/acts/ad-at-5-engine-mount-ring-on-vibro-damp-mount-assembly-inspection/analysis","conflicts":"/api/acts/ad-at-5-engine-mount-ring-on-vibro-damp-mount-assembly-inspection/conflicts","importantCases":"/api/acts/ad-at-5-engine-mount-ring-on-vibro-damp-mount-assembly-inspection/important-cases","documents":"/api/acts/ad-at-5-engine-mount-ring-on-vibro-damp-mount-assembly-inspection/documents"}}