{"id":"F2006B11324","name":"AD/MSR/25 - Carburettor Heat Valve - Modification","slug":"ad-msr-25-carburettor-heat-valve-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":57181,"registerId":"commonwealth-F2006B11324-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/MSR/25 - Carburettor Heat Valve - Modification","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)  Aerospatiale Rallye Series Aeroplanes\n\n \n\nAD/MSR/25 Carburettor Heat Valve - Modification 9/78\n\nApplicability: Models MS883, MS886, MS887, Rallye 150T, 150TD, 150ST, 150ST-D, 180T and 180TD with S/Nos. 1 to 3072. Models MS892A, 150, MS892E, 150, MS892E, 150D, MS893A, MS893E, MS893ED, MS894A, MS894C, MS894E, Rallye 235E, and\n\n235ED with S/Nos. 1 to 13072.\n\n \n\nDocument: 1. Rallye SB No. 137; or\n\n \n\n2. Bureau Veritas AD 78-147(A).\n\n \n\nCompliance: Within 100 hours time in service after 31 October 1978.\n\n \n\nNote: Previous compliance with AD/MSR/14 satisfies compliance with this Directive.\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 Directive limits its requirements to the listed Rallye models and serial-number ranges and specifies two external documents as the methods for compliance (source: \"Applicability\", \"Document\"). It also recognises prior compliance with AD/MSR/14 as satisfying this Directive (source: \"Note\"). The text does not indicate an expansion or contraction of scope beyond those explicit model/SN ranges and the accepted compliance methods, so there is no textual evidence here that the Directive's scope has changed from its stated requirements."},"complexity_factors":["Narrow technical scope: requirement targets a single component (carburettor heat valve) on specified models/SNs (source: \"Applicability\").","External procedural dependence: the modification method and technical detail are in two referenced documents, not in the Directive text itself (source: \"Document\").","Time-limited compliance window: an explicit deadline (100 hours TIS after 31 October 1978) imposes scheduling constraints (source: \"Compliance\").","Alternative compliance path: prior compliance with AD/MSR/14 is accepted, creating a conditional exemption that must be verified (source: \"Note\").","Serial-number-based applicability increases administrative checking: operators must confirm S/Ns against the lists to determine applicability (source: \"Applicability\")."],"plain_english_summary":"This directive requires a modification to the carburettor heat valve on specified Aerospatiale Rallye series aeroplanes (listed by model and serial number) using either Rallye Service Bulletin No.137 or Bureau Veritas AD 78‑147(A). Affected owners/operators and maintenance organisations must complete the work within 100 hours TIS after 31 Oct 1978 (unless already compliant under AD/MSR/14). Costs, scheduling and technical implementation are the responsibility of the owner/operator."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive focused on a specific mechanical modification. It has not expanded beyond its original purpose of mandating a carburettor heat valve fix for specific Rallye aircraft models."},"complexity_factors":["Very short document (approximately 200 words)","Only 2 defined compliance paths (the two documents referenced)","Simple applicability test based on aircraft model and serial number","Single deadline with straightforward extension (100 hours time in service after a fixed date)","No nested exceptions or conditional logic — only one simple note about previous compliance","No cross-references to other legislation beyond the two technical documents"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — essentially a mandatory safety notice issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it requires:** Owners and operators of certain **Aerospatiale Rallye series aeroplanes** must modify the **carburettor heat valve** (a component that prevents engine icing by warming the fuel-air mixture). The modification must be done according to either:\n- Rallye Service Bulletin No. 137, or  \n- Bureau Veritas AD 78-147(A)\n\n**Who it affects:** Specific models of Rallye aircraft with serial numbers up to 3072 or 13072 (depending on the model) — including variants like the MS883, MS886, Rallye 150 series, 180 series, and 235 series.\n\n**When it had to be done:** Within 100 hours of flying time after 31 October 1978.\n\n**Why it matters:** Carburettor icing can cause engine failure. This directive ensures a critical safety modification is made to prevent accidents.\n\n**Good news if you already complied:** If you already followed the earlier directive AD/MSR/14, you're done — that counts as compliance with this one too."}},"importantCases":[],"_links":{"self":"/api/acts/ad-msr-25-carburettor-heat-valve-modification","history":"/api/acts/ad-msr-25-carburettor-heat-valve-modification/history","analysis":"/api/acts/ad-msr-25-carburettor-heat-valve-modification/analysis","conflicts":"/api/acts/ad-msr-25-carburettor-heat-valve-modification/conflicts","importantCases":"/api/acts/ad-msr-25-carburettor-heat-valve-modification/important-cases","documents":"/api/acts/ad-msr-25-carburettor-heat-valve-modification/documents"}}