{"id":"F2005L02380","name":"AD/HS 125/176 - Cockpit Ventilation and Avionics Cooling System Blowers","slug":"ad-hs-125-176-cockpit-ventilation-and-avionics-cooling-system-blowers","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":36788,"registerId":"commonwealth-F2005L02380-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"British Aerospace BAe 125 Series Aeropla","sectionType":"division","heading":"British Aerospace BAe 125 Series Aeroplanes","content":"### British Aerospace BAe 125 Series Aeroplanes\n\n| AD/HS 125/176 | Cockpit Ventilation and AvionicsCooling System Blowers | 10/2005 |\n| ------------- | ------------------------------------------------------ | ------- |\n\n| Applicability: | Raytheon Model HS.125 series 700A aeroplanes, BAe.125 series 800A aeroplanes, and Model Hawker 800 and Hawker 800XP aeroplanes, equipped with Brailsford TBL-2.5 blowers, as identified in Raytheon Service Bulletin SB 24-3272, Revision 1, dated October 2000.                  |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. If not accomplished previously, inspect the aeroplane in accordance with the Accomplishment Instructions of Raytheon SB 24-3272, Revision 1 to determine the current rating of the circuit breakers of certain cockpit ventilation and avionics cooling system blowers.        |\n|                | 2. If, as a result of the Requirement 1 inspection, incorrect circuit breakers are found to be installed replace the circuit breakers and modify the blower wiring, as applicable, in accordance with the Accomplishment Instructions of Raytheon SB 24-3272, Revision 1.         |\n|                | Note: FAA AD 2005-16-02 Amdt 39-14207 refers.                                                                                                                                                                                                                                     |\n| Compliance:    | For Requirement 1 - Within 600 hours time in service or six months after the effective date of this Directive, whichever occurs first.                                                                                                                                            |\n|                | For Requirement 2 - Before further flight, after completing the Requirement 1 inspection.                                                                                                                                                                                         |\n|                | This Airworthiness Directive becomes effective on 29 September 2005.                                                                                                                                                                                                              |\n| Background:    | This Directive requires an inspection to determine the current rating of the circuit breakers of certain cockpit ventilation and avionics cooling system blowers and, if necessary, the replacement of the circuit breakers and modification of the blower wiring, as applicable. |\n\n|     | Actions required by this Directive are intended to prevent smoke and fumes in the cockpit in the event that a blower motor seizes and overheats due to excessive current draw. |\n| --- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n18 August 2005","sortOrder":0},{"sectionNumber":"AD/HS 125/176","sectionType":"part","heading":"AD/HS 125/176","content":"## AD/HS 125/176","sortOrder":1},{"sectionNumber":"Cockpit Ventilation and AvionicsCooling ","sectionType":"part","heading":"Cockpit Ventilation and AvionicsCooling System Blowers","content":"## Cockpit Ventilation and Avionics  \nCooling System Blowers","sortOrder":2},{"sectionNumber":"10/2005","sectionType":"part","heading":"10/2005","content":"## 10/2005","sortOrder":3}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","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 (incorrect circuit breaker ratings). It has not expanded beyond its original technical scope."},"complexity_factors":["Single, specific technical issue (circuit breaker ratings)","Only 2 requirements with clear sequential logic","Minimal defined terms (relies on external service bulletin for technical details)","Straightforward compliance timeline","No nested exceptions or conditional logic beyond the 'if found incorrect' trigger","Short document (approximately 250 words of substantive content)"],"plain_english_summary":"This mandatory CASA Airworthiness Directive requires operators of certain BAe 125/Hawker 700A/800 series aircraft fitted with Brailsford TBL‑2.5 blowers to inspect the circuit breakers for cockpit ventilation and avionics cooling. If incorrect breakers are found they must be replaced and the wiring modified before further flight. The measures, to prevent overheating, smoke and fumes from seized blower motors, must be completed within 600 flight hours or six months, whichever is sooner."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD remains narrowly focused on the original technical problem: preventing smoke/fumes from blower motor overheating by ensuring correct circuit breaker ratings and appropriate wiring. It does not broaden regulation to other systems or aircraft beyond those explicitly listed, nor does it add unrelated obligations. Therefore the scope has not grown beyond the original safety purpose as expressed in the directive and the referenced Raytheon service bulletin."},"complexity_factors":["Single focused subject: cockpit ventilation and avionics cooling blowers","Applicability limited to a small set of aircraft models and a specific blower model (Brailsford TBL-2.5)","Two-step requirement: (1) inspection; (2) conditional corrective action","Relies on one external document: Raytheon Service Bulletin SB 24-3272, Revision 1 (cross-reference increases operational complexity)","Simple compliance timing: one inspection deadline (600 hours or six months) and an immediate 'before further flight' requirement if defects found","One cross-reference to FAA AD 2005-16-02 (informational)"],"plain_english_summary":"**What this directive does (mechanically)**\n\n- This Airworthiness Directive (AD) requires operators of certain BAe 125 / Hawker 800 series aeroplanes to inspect the circuit breakers fitted to specific cockpit ventilation and avionics cooling blowers and, if necessary, replace the breakers and modify the blower wiring. (See \"Applicability\" and \"Requirement\".)\n\n**Which aeroplanes are covered**\n\n- Applies only to Raytheon Model HS.125 series 700A, BAe.125 series 800A, and Model Hawker 800 and Hawker 800XP aeroplanes that are fitted with Brailsford TBL-2.5 blowers and identified in Raytheon Service Bulletin SB 24-3272, Revision 1 (October 2000). (See \"Applicability\".)\n\n**Required steps and timing**\n\n- Inspection: Inspect the aeroplane to determine the current rating of the circuit breakers for the affected blowers, following the instructions in Raytheon SB 24-3272, Revision 1. (Requirement 1.)\n- Corrective action: If the inspection finds incorrect circuit breakers, replace them and modify the blower wiring as required by the Raytheon service bulletin. (Requirement 2.)\n- Compliance times: Complete the inspection within 600 flight hours or six months from the AD's effective date (whichever is first). If incorrect breakers are found, the replacements/wiring changes must be done before the aircraft flies again. (See \"Compliance\".)\n\n**Why the regulator requires this**\n\n- The AD states the technical aim is to prevent smoke and fumes in the cockpit that could arise if a blower motor seizes and overheats because of excessive current draw. The AD cites FAA AD 2005-16-02 as related material. (See \"Background/Note\".)\n\n**Who pays and who decides**\n\n- Aircraft owners/operators pay for the inspection, any replacement parts (circuit breakers), wiring work, and associated maintenance labour and downtime. Maintenance providers perform the work under the operator's direction, following the Raytheon service bulletin. The aviation regulator (CASA) enforces the AD; compliance is mandatory for continued legal operation of the aircraft.\n\n**Costs, incentives and trade-offs**\n\n- Direct costs: inspection labour and potential parts and wiring modification costs. Indirect costs: aircraft downtime while work is completed and any scheduling disruption.\n- Incentive structure: Operators must comply to keep aircraft airworthy and legally flyable. The AD shifts the immediate cost burden to the small set of operators who have the affected blower model installed.\n- Benefits vs costs: The intervention substitutes a small, upfront inspection/repair cost for a reduced risk of in-flight smoke/fumes—an operational and safety benefit. The AD does not monetise risk reduction; operators must weigh downtime and parts availability against that safety aim.\n\n**Implementation and compliance risks**\n\n- The AD relies on an external service bulletin (Raytheon SB 24-3272, Revision 1). If parts are scarce or service-bulletin instructions need interpretation, operators may face delays or varying repair costs.\n- The AD contains one conditional branch only (do work before further flight if incorrect breakers are found), so enforcement hinges on accurate inspection records and competent maintenance.\n\n**Effects on markets and third parties**\n\n- Maintenance shops and parts suppliers servicing these specific aeroplane models may see increased short-term demand for breakers and wiring work. The directive is narrowly targeted; it does not create broad regulatory change for other models or systems.\n\n**Source-claimed purpose vs practical implications**\n\n- The AD claims its purpose is to prevent smoke/fumes from an overheated blower motor. Mechanically, it enforces an inspection and correction cycle to ensure correct circuit-breaker ratings and wiring. The practical trade-offs are concentrated compliance costs for affected operators, modest commercial opportunity for maintenance suppliers, and a reduction of the specific technical risk identified.\n\n(References in the directive: \"Applicability\", \"Requirement 1\", \"Requirement 2\", \"Compliance\", \"Background\" and the reference to FAA AD 2005-16-02.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-hs-125-176-cockpit-ventilation-and-avionics-cooling-system-blowers","history":"/api/acts/ad-hs-125-176-cockpit-ventilation-and-avionics-cooling-system-blowers/history","analysis":"/api/acts/ad-hs-125-176-cockpit-ventilation-and-avionics-cooling-system-blowers/analysis","conflicts":"/api/acts/ad-hs-125-176-cockpit-ventilation-and-avionics-cooling-system-blowers/conflicts","importantCases":"/api/acts/ad-hs-125-176-cockpit-ventilation-and-avionics-cooling-system-blowers/important-cases","documents":"/api/acts/ad-hs-125-176-cockpit-ventilation-and-avionics-cooling-system-blowers/documents"}}