{"id":"F2006B09052","name":"AD/DHC-2/33 - Exhaust Collector Ring Segments","slug":"ad-dhc-2-33-exhaust-collector-ring-segments","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52777,"registerId":"commonwealth-F2006B09052-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n![](image.001.png)  \n\nDHC-2 (Beaver) Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/DHC-2/33 Exhaust Collector Ring Segme","sectionType":"part","heading":"AD/DHC-2/33 Exhaust Collector Ring Segments 7/2003","content":"# AD/DHC-2/33 Exhaust Collector Ring Segments 7/2003\n\nApplicability: All Bombardier Inc. DHC-2 Mk. 1 aeroplanes.\n\nRequirement: 1. Remove the carburettor heater muff, part number (P/N) C2-EE-181A, \\-161A, \\- 171A, and \\-1155A and inspect the exhaust collector ring segments, P/N C2- EE251A, \\-253A, \\-255A, and \\-257A, for cracks or burnt holes.\n\n    2. Replace segments that have developed major breaks, cracks other than minor, or burning.\n\n    3. Segments with minor cracks must either be replaced or repaired by welding as per DHC-2 Beaver Maintenance Manual Para. 5.4.3, and DHC-2 Beaver Repair Manual Para. 6-13.\n    4. Replace segments that have developed further cracking from repair welds.\n\nNote: Transport Canada AD CF-2002-49 refers.\n\nCompliance: 1. Within 150 flight hours from the effective date of this directive and thereafter at intervals not to exceed 150 flight hours.\n\n2, 3 and 4. Before further flight.\n\nThis Airworthiness Directive becomes effective on 10 July 2003.\n\nBackground: To prevent the possibility of a carburettor fire upon starting, particularly when the hot air valve control is in the “hot” position, this Directive requires a 150- hour repetitive inspection on exhaust collector ring segments to verify their integrity.\n\n![Signature of Jim Coyne Delegate of the Civil Aviation Safety Authority](image.002.png)  \n\nJim Coyne\n\nDelegate of the Civil Aviation Safety Authority 28 May 2003\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 18 June 2003.","sortOrder":1}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD is narrowly targeted at a single unsafe condition (potential carburettor fire on start) for a single aircraft type and prescribes inspection and corrective actions for specific part numbers. It does not expand the regulatory scope beyond those aircraft, parts, and the stated risk; it adds a recurring inspection requirement but stays within the original corrective-intent scope described in the Background."},"complexity_factors":["Short document: single-aircraft-type AD with clear applicability (DHC-2 Mk.1)","Few procedural steps (Remove/Inspect; Replace; Repair; Replace if repaired part cracks again)","Simple compliance schedule (initial and repetitive inspections every 150 flight hours)","Small number of part numbers specified (4 muff P/Ns; 4 collector segment P/Ns)","One external cross-reference to Transport Canada AD and two references to specific Maintenance/Repair Manual paragraphs (adds moderate technical dependency but not legal complexity)","No nested exceptions or conditional chains beyond straightforward before-further-flight and interval rules"],"plain_english_summary":"**What this instrument does (mechanical change)\n\n- Requires owners/operators and maintenance personnel of Bombardier Inc. DHC-2 Mk.1 (Beaver) aeroplanes to inspect specific exhaust collector ring segments (part numbers C2-EE251A, -253A, -255A, -257A) for cracks or burnt holes and to take immediate corrective action when defects are found. (Applicability; Requirement 1–4)\n\n- Specifically: remove the carburettor heater muff (P/Ns C2-EE-181A, -161A, -171A, -1155A) to access and inspect the exhaust collector ring segments; replace segments with major breaks/cracks or burning; either replace or repair (weld) segments with only minor cracks following the DHC-2 Maintenance/Repair Manual procedures; and replace any segment that develops further cracking after a repair weld. (Requirement 1–4)\n\n- Inspection timing and recurrence: do the first inspection within 150 flight hours of the AD’s effective date and then repeat every 150 flight hours. If a segment requires repair or replacement under items 2–4, those actions must be completed before the aeroplane is flown again. (Compliance)\n\n**Who it affects\n\n- Aircraft owners/operators of Bombardier DHC-2 Mk.1 aeroplanes.\n- Licensed maintenance organisations and engineers who perform the inspections, welding repairs, and parts replacement.\n- Parts suppliers who provide the specified collector ring segments and carburettor heater muffs.\n\n**Why it matters (stated purpose and mechanical effect)\n\n- The AD’s stated purpose is to reduce the risk of a carburettor fire at engine start-up when the hot-air valve control is in the \"hot\" position by ensuring the exhaust collector ring segments are intact and free of cracking or burning. (Background)\n\n**Practical consequences, costs and incentives\n\n- Who pays: aircraft owners/operators pay for the inspections, parts, repairs or replacements, and for any down-time while maintenance is carried out. (Requirement; Compliance)\n- Behaviour change: operators must add a 150‑hour recurring inspection to their scheduled maintenance and either replace or weld-repair items found with minor cracking; they must ground aircraft until items with major damage are replaced or repairs are completed. (Compliance; Requirement 2–4)\n- Choice incentives: because the AD requires replacement if a repaired part develops further cracking, operators face a trade-off between the lower upfront cost of repair-welding and the risk of repeated maintenance or mandatory replacement after subsequent cracking. (Requirement 3–4)\n- Implementation risk: effectiveness depends on access to the specified parts and on mechanics following the referenced maintenance and repair manual procedures (DHC-2 Beaver Maintenance Manual para. 5.4.3; Repair Manual para. 6-13). If parts or skilled labour are scarce, compliance could be delayed, increasing operational disruption. (Requirement; Note)\n- Compliance burden: recurring inspections every 150 flight hours impose recurring labour and administrative costs; for high-utilisation aircraft this is frequent and may affect availability and operating costs. (Compliance)\n- Regulatory linkage: the AD references an equivalent Transport Canada AD (CF-2002-49) and requires compliance with the DHC-2 manuals, adding cross-jurisdictional and technical references maintenance staff must follow. (Note; Requirement)\n\n**Trade-offs and opportunity costs\n\n- The AD trades increased maintenance cost and aircraft downtime for a reduced probability of carburettor fire on start. Operators must weigh immediate maintenance expenditure and reduced availability against the safety benefit and avoided risk of in-flight or ground incidents.\n\n**Who decides now vs before\n\n- The Civil Aviation Safety Authority (CASA), through its delegate, mandates the inspection and corrective actions; maintenance personnel still decide whether to repair (weld) or replace minor-cracked segments, within the AD’s constraints and the manuals it references. (Header; Requirement)\n\n**References in the instrument\n\n- Applicability: all Bombardier DHC-2 Mk.1 aeroplanes.\n- Requirement 1–4: removal, inspection, replace/repair, and replacement-after-failure rules.\n- Compliance: timing (150 flight hours) and before-further-flight requirement.\n- Background: rationale (prevent carburettor fire when hot-air valve is in \"hot\").\n- Cross-references: DHC-2 Beaver Maintenance Manual para. 5.4.3; Repair Manual para. 6-13; Transport Canada AD CF-2002-49.\n\n(Sections noted in parentheses refer to the stated parts of the Airworthiness Directive.)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow airworthiness directive targeting a specific unsafe condition in a specific aircraft type. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (under 500 words)","Only 4 specific part numbers mentioned in the requirement","Single, clearly defined applicability (one aircraft model)","Straightforward compliance timeline (150 flight hours, repetitive)","No cross-references to other legislation (only a note about a Canadian equivalent AD)","Simple conditional logic: inspect → if damaged, repair/replace → if repaired and cracks again, replace","No defined terms section; all technical terms are standard aviation maintenance terminology"],"plain_english_summary":"The CASA safety order targets a fire hazard in Bombardier DHC‑2 Mk.1 Beavers: cracked or burned exhaust collector ring segments can leak hot exhaust and ignite carburettor heat on startup. Owners/operators must inspect segments every 150 flight hours, immediately replace severely damaged parts, and repair minor cracks only per manufacturer procedures (welds allowed but must be replaced if they crack again). Compliance is mandatory to prevent startup engine fires and maintain airworthiness."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-2-33-exhaust-collector-ring-segments","history":"/api/acts/ad-dhc-2-33-exhaust-collector-ring-segments/history","analysis":"/api/acts/ad-dhc-2-33-exhaust-collector-ring-segments/analysis","conflicts":"/api/acts/ad-dhc-2-33-exhaust-collector-ring-segments/conflicts","importantCases":"/api/acts/ad-dhc-2-33-exhaust-collector-ring-segments/important-cases","documents":"/api/acts/ad-dhc-2-33-exhaust-collector-ring-segments/documents"}}