{"id":"F2006B04037","name":"AD/BEECH 55/90 - KA-33 Cooling Blower","slug":"ad-beech-55-90-ka-33-cooling-blower","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":43646,"registerId":"commonwealth-F2006B04037-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# ![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\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 CAR 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\nBeechcraft 55, 58 and 95-55 (Baron) Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/BEECH 55/90 KA-33 Cooling Blower 8/20","sectionType":"part","heading":"AD/BEECH 55/90 KA-33 Cooling Blower 8/2001","content":"# AD/BEECH 55/90 KA-33 Cooling Blower 8/2001\n\nApplicability: Beech Model 58 and 58A aeroplanes, serial numbers TH-1436 through TH-1883 inclusive.\n\nRequirement: 1. Inspect the aeroplane in accordance with Part I of the Accomplishment Instructions of Raytheon Mandatory Service Bulletin SB 34-3267, issued March 1999, to verify whether a KA-33 avionics cooling blower system is installed and operating correctly.\n\n    2. If the Requirement 1 inspection confirms that a KA-33 cooling blower is fitted, install a one ampere circuit breaker, part number 7277-2-1, in place of the factory installed three ampere or five ampere circuit breakers in accordance with Part II of the Accomplishment Instructions of SB 34-3267.\n\n    3. Three ampere or five ampere circuit breakers must not be installed on any aeroplane to protect the KA-33 cooling blower.\n\nNote: FAA AD 2001-11-03 Amdt 39-12244 refers.\n\nCompliance: For Requirement 1 - Within the next 600 hours time-in-service after the effective date of this Directive or the next six calendar months after the effective date of this Directive, whichever occurs first.\n\nFor Requirement 2 - Before further flight after the Requirement 1 inspection. For Requirement 3 - As of the effective date of this Directive.\n\nThis Airworthiness Directive becomes effective on 9 August 2001.\n\nBackground: The United States Federal Aviation Administration has received several reports of blower motors failing, seizing, smoking, and producing a burning odour that enters the cabin and passenger compartment. These events are the result of the blower motor having circuit protection of more than one ampere. This level of circuit protection does not prevent the blower motor from smoking and creating a burning odour should it fail or seize.","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"This directive is narrowly focused on correcting an identified unsafe condition (blower motors smoking/seizing due to excessive circuit-breaker rating). It does not expand the regulator's role beyond that safety task, nor does it broaden to unrelated equipment, aircraft types, or novel regulatory powers. The measures (inspection, replacement with a specified part, and prohibition of higher-rated breakers) align with the stated safety purpose."},"complexity_factors":["Single, narrow applicability: specific models and a single serial-number range (TH-1436–TH-1883).","Only three operative requirements (inspect; replace specific breaker if fitted; prohibition on 3A/5A breakers).","Short, fixed compliance timings: 600 hours TIS or six months (whichever first) for inspection; 'before further flight' for replacement; immediate prohibition for 3A/5A breakers.","One external cross-reference to manufacturer instructions (Raytheon Mandatory Service Bulletin SB 34-3267) that contains the detailed inspection/installation steps.","One external regulatory cross-reference (FAA AD 2001-11-03) cited in the Note.","Low conditional nesting: actions are conditional only on whether the KA-33 blower is present and operating correctly."],"plain_english_summary":"**What this directive does (in plain English)**\n\n- This is an airworthiness directive (safety order) that applies to certain Beechcraft Baron aeroplanes. It requires owners/operators to check whether a KA-33 avionics cooling blower is fitted, and if it is, to replace the existing circuit breaker that protects that blower with a smaller one and to stop using larger breakers on that blower. (Applicability; Requirement 1–3.)\n\n**Which aircraft are affected**\n\n- Beech Model 58 and 58A aeroplanes with serial numbers TH-1436 through TH-1883 inclusive. (Applicability.)\n\n**What you must do and when**\n\n- Inspect the aeroplane following Raytheon Mandatory Service Bulletin SB 34-3267 (Part I of the Accomplishment Instructions) to confirm whether a KA-33 blower is installed and operating correctly. (Requirement 1.)\n- If the inspection shows a KA-33 blower is fitted, replace the factory three-ampere or five-ampere circuit breaker protecting that blower with a one-ampere circuit breaker, part number 7277-2-1, following Part II of SB 34-3267. That replacement must be done before the aeroplane next flies after the inspection. (Requirement 2; Compliance.)\n- From the effective date of the directive, no three-ampere or five-ampere circuit breakers may be used to protect the KA-33 blower. (Requirement 3; Compliance.)\n- Timing: the inspection must be completed within the next 600 hours time-in-service or within six calendar months after the directive’s effective date, whichever happens first. The replacement (if required) must be done before further flight after the inspection. (Compliance.)\n\n**Why the regulator ordered this**\n\n- The US FAA reported several incidents where the KA-33 blower motors failed, seized, smoked or produced a burning odour in the cabin. The investigation linked those events to circuit breakers rated at three or five amperes providing insufficient protection against motor failure; using a one-ampere breaker reduces the chance that a failing blower will smoke and cause fumes in the cabin. (Background; FAA AD 2001-11-03 referenced.)\n\n**Who pays and who decides**\n\n- Aircraft owners/operators pay for the inspection and any replacement parts and labour required to install the one-ampere circuit breaker (Requirement 2). The regulator (the CASA delegate issuing the AD) requires compliance and sets the deadlines (opening paragraph; Compliance). Maintenance must be carried out in accordance with the Raytheon service bulletin the AD references (Requirement 1; Requirement 2). \n\n**Practical effects, trade-offs and implementation notes**\n\n- Direct costs: inspection labour and, if a KA-33 blower is fitted, the cost of the one-ampere breaker (part number 7277-2-1) and installation labour. (Requirement 2.)\n- Operational disruption: if a KA-33 blower is fitted and the breaker must be changed, the aeroplane cannot be flown until the replacement is done (Requirement 2 — \"before further flight\"). That creates potential aircraft downtime. (Compliance.)\n- Spare parts and logistics: the AD mandates a specific breaker part number and prohibits use of 3A/5A breakers for that blower (Requirement 2–3). Operators or MROs (maintenance organisations) will need to hold or source the specified 1A breakers, which may change spare inventory needs and supplier demand. (Requirement 2–3.)\n- Reliance on manufacturer instructions: the AD requires following Raytheon Mandatory Service Bulletin SB 34-3267 — compliance therefore depends on the availability and clarity of that service bulletin. (Requirement 1–2.)\n- Enforcement and identification: the directive applies only to a specific serial-number range and to aeroplanes with the KA-33 blower installed. Accurate records, inspections and maintenance documentation are needed to determine applicability and show compliance. (Applicability; Requirement 1; Compliance.)\n\n**Testing the stated purpose against practical costs and risks**\n\n- The stated safety objective is tighter circuit protection to reduce the risk of a blower motor smoking or producing fumes in the cabin (Background). That objective is mechanically achieved by changing to a lower-rated breaker (Requirement 2) and banning higher-rated breakers (Requirement 3). \n- Costs are concentrated on the aircraft owners/operators and maintenance providers (inspection and parts). Benefits (reduced risk of cabin smoke/odour) are diffuse — they accrue to occupants and the wider public safety environment. This creates clear incentives for owners to comply promptly, but also creates short-term opportunity costs (aircraft downtime, parts procurement). \n- Implementation risk areas: availability of the specified breaker, correct identification of KA-33 installations during inspection, and adherence to the Raytheon service bulletin. Incorrect substitutions of breakers (contrary to Requirement 3) would undermine the safety aim and breach the AD.\n\n**Bottom line**\n\n- The AD is a targeted safety mandate for a defined set of Beech 58/58A aeroplanes: inspect for a KA-33 blower, and if present, replace the existing 3A/5A breaker with the specified 1A breaker before further flight, while prohibiting use of 3A/5A breakers on that blower going forward. It imposes modest direct costs and some downtime on affected operators in order to reduce the risk of blower-related smoke/fumes in the cabin. (Applicability; Requirement 1–3; Compliance; Background.)"},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific identified hazard (overcurrent protection failure in KA-33 cooling blowers). The scope remains precisely limited to the affected aircraft serial numbers and the specific corrective action required. No scope creep is evident."},"complexity_factors":["Single-issue directive with only 3 requirements","Clear applicability section limiting scope to specific serial numbers","Straightforward compliance timeline with simple alternatives (hours OR months)","Only one external document reference (Raytheon Service Bulletin SB 34-3267)","No nested exceptions or conditional logic beyond the 'if found, then replace' structure","Minimal defined terms (only standard aviation terminology like 'time-in-service')"],"plain_english_summary":"This Airworthiness Directive requires owners/operators of Beechcraft Model 58 and 58A aeroplanes (S/N TH-1436 through TH-1883) to inspect for a KA-33 avionics cooling blower and, if present, replace its existing 3‑amp or 5‑amp circuit breaker with a 1‑amp breaker to prevent overheating, smoke, and fire. Reinstallation of 3‑amp or 5‑amp breakers for this blower is prohibited.\n\nInspection is required within 600 flight hours or 6 months after 9 August 2001; if the KA‑33 is found, the 1‑amp breaker must be fitted before the next flight."}},"importantCases":[],"_links":{"self":"/api/acts/ad-beech-55-90-ka-33-cooling-blower","history":"/api/acts/ad-beech-55-90-ka-33-cooling-blower/history","analysis":"/api/acts/ad-beech-55-90-ka-33-cooling-blower/analysis","conflicts":"/api/acts/ad-beech-55-90-ka-33-cooling-blower/conflicts","importantCases":"/api/acts/ad-beech-55-90-ka-33-cooling-blower/important-cases","documents":"/api/acts/ad-beech-55-90-ka-33-cooling-blower/documents"}}