{"id":"F2006B09271","name":"AD/DHE/21 - Minimum Modification Standard at Major Reconditioning","slug":"ad-dhe-21-minimum-modification-standard-at-major-reconditioning","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":53297,"registerId":"commonwealth-F2006B09271-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHE/21 - Minimum Modification Standard at Major Reconditioning","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 - 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  De Havilland Piston Engines\n\n \n\n# AD/DHE/21 Minimum Modification Standard at Major Reconditioning\n\nApplicability: Gipsy Major 1D and 1J Series.\n\n# 6/72\n\n \n\nDocument: R.R Gipsy TNSG No 15 of 18 February 1970 & Appendix 1 dated 27 June 1963. Compliance:               Before installation following next reconditioning completed after 30 June 1972.\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\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":870},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive maintains its original narrow scope targeting specific De Havilland engine models for mandatory upgrades during overhauls. No expansion beyond the original technical safety requirement is evident."},"complexity_factors":["Single, clearly defined applicability (only two specific engine models)","Straightforward compliance trigger (reconditioning after fixed date)","No nested exceptions or conditional logic","Minimal cross-referencing (only one technical document referenced)","Extremely brief text with no interpretation section"],"plain_english_summary":"**What this does:** This directive sets a safety standard for specific vintage aircraft engines. It requires that De Havilland Gipsy Major 1D and 1J engines must meet minimum modification requirements whenever they undergo major reconditioning (a complete overhaul).\n\n**Who it affects:** Owners and operators of aircraft using Gipsy Major 1D or 1J engines — these are piston engines commonly found in older aircraft like the Tiger Moth and Chipmunk.\n\n**What must happen:** If one of these engines is reconditioned after 30 June 1972, it must be modified according to technical specifications in De Havilland document TNSG No. 15 (1970) before being reinstalled. This ensures old engines aren't returned to service with outdated, potentially unsafe configurations.\n\n**Why it matters:** Prevents safety risks from obsolete engine components by mandating upgrades during major overhauls rather than allowing grandfathered (historically permitted but now outdated) configurations to persist indefinitely."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhe-21-minimum-modification-standard-at-major-reconditioning","history":"/api/acts/ad-dhe-21-minimum-modification-standard-at-major-reconditioning/history","analysis":"/api/acts/ad-dhe-21-minimum-modification-standard-at-major-reconditioning/analysis","conflicts":"/api/acts/ad-dhe-21-minimum-modification-standard-at-major-reconditioning/conflicts","importantCases":"/api/acts/ad-dhe-21-minimum-modification-standard-at-major-reconditioning/important-cases","documents":"/api/acts/ad-dhe-21-minimum-modification-standard-at-major-reconditioning/documents"}}