{"id":"F2006B02164","name":"AD/AC-100/12 - Exhaust Muffler - Modification","slug":"ad-ac-100-12-exhaust-muffler-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41394,"registerId":"commonwealth-F2006B02164-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AC-100/12 - Exhaust Muffler - Modification","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-description: CASA Airworthiness Directive\nmeta-generator: Aspose.Words for .NET 22.10.0\nmeta-keywords: Issue 3/1973,Aircraft below 5700 kg,S.L. Industries Commander 100 Series and Volair 10 Series Aeroplanes,Exhaust Muffler - Modification,12\ntitle: Airworthiness Directive - AD/AC-100/12 - Exhaust Muffler - Modification\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)  S.L. Industries Commander 100 Series and Volair 10 Series Aeroplanes\n\n \n\nAD/AC-100/12 Exhaust Muffler - Modification 3/73\n\nApplicability: Models 100 and 100-180 as detailed in the compliance document. Document: 1. Aero Commander SB 1019; OR\n\n2. FAA AD 73-1-1.\n\n \n\nCompliance: Modify within 100 hours’ time in service after 30 March 1973.\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 AD’s scope remains focused on requiring an exhaust muffler modification for the specified aircraft models. It prescribes a compliance deadline and identifies the acceptable technical documents to use (Aero Commander SB 1019 or FAA AD 73-1-1). There is no textual indication in the AD itself that the scope has been broadened or narrowed from an earlier intent; the directive confines obligations to owners/operators of the listed models and delegates the technical method to the referenced documents (\"Applicability\", \"Document\", \"Compliance\")."},"complexity_factors":["Narrow and model-specific applicability (Models 100 and 100-180) reduces breadth of impacted parties.","Single, well-defined required action (muffler modification) lowers procedural complexity.","Clear, short compliance deadline (100 hours TIS after 30 March 1973) simplifies scheduling but imposes a fixed time constraint.","Reliance on external technical documents (Aero Commander SB 1019 or FAA AD 73-1-1) adds a layer of dependency and requires consultation of those sources for technical detail.","Absence of in-text technical detail or stated rationale increases need to consult external documents or historical records for full context."],"plain_english_summary":"What this directive changes (mechanical action)\n\n- This Airworthiness Directive (AD) requires a physical modification to the exhaust muffler on specified aeroplane models. The change is to be carried out in accordance with a specified service document: either Aero Commander Service Bulletin 1019 or FAA AD 73-1-1 (\"Document\"). (See: \"Applicability\" and \"Document\".)\n\nWho is affected and who decides\n\n- The AD applies to S.L. Industries Commander 100 Series and Volair 10 Series aeroplanes, specifically Models 100 and 100-180 as listed in the compliance document. Owners and operators of those aircraft must ensure the modification is completed. (See: \"Applicability\".)\n- The Civil Aviation Safety Authority (CASA) issues the AD and sets the compliance deadline. The AD delegates the technical method of modification to the referenced service documents. (See: \"Document\" and \"Compliance\".)\n\nWhen it must be done\n\n- The required modification must be completed within 100 hours’ time in service after 30 March 1973. That is the prescribed compliance window. (See: \"Compliance\".)\n\nStated purpose and how that links to costs and incentives\n\n- The AD itself does not include an explicit statement of the safety concern or problem being addressed. The directive’s requirement to modify the exhaust muffler and the fact it is an airworthiness directive imply the objective is to correct a technical or safety-related condition; that is a claim about purpose drawn from the form of the instrument, not an explicit statement in the text. (Source: the AD contains no express rationale text.)\n\nCosts, who pays, and compliance burden\n\n- Owners/operators of the affected aircraft bear the costs of arranging and paying for the modification (parts, labour, potential inspections). (Implied by the AD’s applicability and compliance requirement.)\n- The compliance burden is time-limited: the work must be done within 100 hours’ time in service after the stated date, which imposes scheduling and downtime costs on operators. (See: \"Compliance\".)\n- The AD points to external technical instructions (Aero Commander SB 1019 or FAA AD 73-1-1) as the method of compliance, so affected parties must obtain and follow those documents to confirm exact parts and procedures. That adds administrative steps and potential costs if special parts or certified shop work is required. (See: \"Document\".)\n\nImplementation risk and discretion\n\n- Implementation requires mechanical modification; the quality of the work will depend on the skills of the maintenance provider and adherence to the referenced service instructions. The AD itself does not specify alternative compliance methods or discretionary exemptions. Compliance choices are limited to the specified documents. (See: \"Document\".)\n\nEffects on private choice and markets\n\n- The measure imposes a targeted, model-specific compliance cost on owners/operators of the listed aircraft. It does not directly change ownership rules, market entry, or competition in a broad sense. However, owners may face short-term reductions in aircraft availability and may incur repair costs that affect operating economics for the affected fleet.\n- Because the AD references specific service instructions, markets for parts and approved maintenance services for these models may see concentrated increased demand for the modification work.\n\nTrade-offs, opportunity costs and observable risks\n\n- Opportunity costs include aircraft downtime and spend on modification instead of other maintenance or uses. The AD narrows the method of compliance to external documents, reducing flexibility but increasing uniformity in implementation.\n- The AD is brief and relies on external technical documents for detailed steps. That creates a risk that affected parties must consult multiple sources to confirm exact requirements and costs. (See: \"Document\" and lack of technical detail in the AD.)\n\nIn short\n\n- Mechanically: modify the exhaust muffler on Models 100 and 100-180 per the referenced service document.\n- Who pays: owners/operators of those aeroplanes.\n- Deadline: within 100 hours’ time in service after 30 March 1973.\n- Method: follow Aero Commander SB 1019 or FAA AD 73-1-1.\n\n(References in this summary: the AD’s \"Applicability\", \"Document\" and \"Compliance\" lines.)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a historical Airworthiness Directive from 1973 (Issue 3/1973). It remains focused on its original narrow purpose: mandating a specific exhaust muffler modification for specific aircraft models. There is no evidence of scope creep; it has not expanded beyond the original safety issue it was designed to address."},"complexity_factors":["Extremely short document (approximately 150 words of substantive content)","Only 2 defined references (the compliance documents)","Simple, single-condition compliance requirement (time-based deadline)","No nested exceptions or conditional logic","Clear applicability statement limiting scope to specific aircraft models","No cross-referencing to other legislation beyond the two named documents"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) issued by Australia's Civil Aviation Safety Authority (CASA). An Airworthiness Directive is essentially a mandatory safety notice that tells aircraft owners and operators they must fix a specific problem or risk their aircraft being grounded.\n\n**What it requires:** Owners of specific light aircraft models—the S.L. Industries Commander 100 Series and Volair 10 Series—must modify their exhaust muffler system. The modification must be completed within 100 hours of flying time after 30 March 1973.\n\n**Who it affects:** Anyone who owns or operates these particular small aircraft (weighing less than 5,700 kg). This includes private pilots, flying schools, and small aviation businesses using these specific models.\n\n**Why it matters:** Exhaust muffler failures can cause carbon monoxide leaks into the cabin (which can kill pilots and passengers) or engine fires. This directive forces a safety fix to prevent accidents.\n\n**How to comply:** Aircraft owners must follow either:\n- Aero Commander Service Bulletin 1019 (the manufacturer's official repair instructions), OR\n- FAA AD 73-1-1 (the equivalent American safety notice)\n\n**The bottom line:** If you own one of these planes, you had a deadline (100 flight hours after March 1973) to get this exhaust fix done. Flying without doing so would violate civil aviation law."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ac-100-12-exhaust-muffler-modification","history":"/api/acts/ad-ac-100-12-exhaust-muffler-modification/history","analysis":"/api/acts/ad-ac-100-12-exhaust-muffler-modification/analysis","conflicts":"/api/acts/ad-ac-100-12-exhaust-muffler-modification/conflicts","importantCases":"/api/acts/ad-ac-100-12-exhaust-muffler-modification/important-cases","documents":"/api/acts/ad-ac-100-12-exhaust-muffler-modification/documents"}}