{"id":"F2006B03512","name":"AD/BAe 146/63 - Pitot-Static System - True Airspeed Computer No.1","slug":"ad-bae-146-63-pitot-static-system-true-airspeed-computer-no-1","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":43073,"registerId":"commonwealth-F2006B03512-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BAe 146/63 - Pitot-Static System - True Airspeed Computer No.1","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nBritish Aerospace BAe 146 Series Aeroplanes\n\nAD/BAe 146/63 Pitot-Static System \\- True Airspeed Computer No.1\n\n  \n10/96\n\nApplicability: This Directive is applicable to BAe 146 Series 100, 100A, 200, 200A, 300 and 300A aeroplanes equipped with a True Airspeed (TAS) Computer No 1 installed in accordance with BAe Avro modification HCM40159B (SB.34-69-40159B) or HCM40297G and where a Dual Mode \\`S' Transponder has been installed in accordance with BAe Avro modification HCM30118B (SB.34-90-30118B) or HCM40277A (SB.34-91-40277A).\n\nNote: The requirements of this Directive were incorporated prior to delivery on the following constructors number aeroplanes, if the modifications referenced above were also incorporated:\n\nSeries 100 and 100A \\- E1199 and subsequent.\n\nSeries 200 and 200A \\- E1270, E2178, E2188, E2196 and subsequent.\n\nSeries 300 and 300A \\- E3118, E3163, E3165, E3169, E3181, E3185, E3187, E3189,\n\nE3191 and subsequent.\n\nRequirement: Install new pitot and static lines between the TAS 1 unit and the drain valve in accordance with either British Aerospace (Commercial Aircraft) Limited, Modification Service Bulletin SB.34-131-46041A dated 24 June 1991 or British Aerospace, Regional Aircraft Limited, Avro International Division, Modification Service Bulletin SB.34-131-46041A Revision 2 dated 2 July 1996.\n\nNote: Both Service Bulletins have been classified as mandatory by the CAA(UK).\n\nCompliance: Unless previously accomplished, then prior to 31 December 1996.\n\nThis directive becomes effective on 12 September 1996.\n\nBackground: The introduction of the Mode \\`S' transponder resulted in the TAS 1 unit being moved from its position on the avionics rack. This resulted in the pitot and static flexible hoses between the TAS 1 unit and the drain valve forming an unacceptable water trap. This Directive introduces new shorter flexible hoses designed to minimise the likelihood of water being trapped.","sortOrder":0}],"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"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"This directive addresses a narrow technical problem that arose after relocation of the TAS 1 unit (the pitot/static hoses forming a water trap). The required action—installing shorter hoses per a BAe service bulletin—is consistent with that original, stated purpose. It does not broaden regulatory scope beyond correcting that specific installation/configuration issue; it is a focused airworthiness retrofit rather than an expansion into unrelated regulatory areas."},"complexity_factors":["Short, single-issue Airworthiness Directive focused on a single modification (pitot/static hoses).","Applicability limited to six model variants (Series 100, 100A, 200, 200A, 300, 300A) with two specific TAS and two specific transponder modification references.","Cross-references to two versions of a single Service Bulletin (SB.34-131-46041A and Revision 2).","Contains a compliance deadline and effective date (time-bound requirement).","Notes on constructor-number aircraft where modification was incorporated pre-delivery (conditional applicability for specific serial numbers)."],"plain_english_summary":"**What this directive does**\n\n- Requires certain BAe 146 aeroplanes to have new pitot and static flexible hoses fitted between the True Airspeed (TAS) Computer No.1 unit and the drain valve. (See \"Requirement\")\n\n**Which aeroplanes are affected**\n\n- BAe 146 Series 100, 100A, 200, 200A, 300 and 300A that have both:\n  - a TAS Computer No.1 installed under BAe Avro modification HCM40159B or HCM40297G, and\n  - a Dual Mode 'S' transponder installed under BAe Avro modification HCM30118B or HCM40277A. (See \"Applicability\")\n\n- The directive notes some constructor-number aeroplanes already had these modifications incorporated before delivery; those aircraft do not need a separate retrofit. (See \"Note\" under Applicability)\n\n**What operators must do and by when**\n\n- Install the replacement pitot/static hoses in accordance with the specified British Aerospace (Avro) Service Bulletin SB.34-131-46041A (either the 24 June 1991 issue or the Revision 2 dated 2 July 1996). (See \"Requirement\")\n- If not already done, the work must be completed prior to 31 December 1996. The directive took effect on 12 September 1996. (See \"Compliance\" and effective date)\n\n**Why this work is required (mechanics, not opinion)**\n\n- According to the directive, moving the TAS 1 unit to accommodate the Mode 'S' transponder changed the routing/length of the flexible pitot and static hoses. That re-routing created an unacceptable water trap between the TAS unit and the drain valve. The replacement hoses are shorter and intended to minimise the likelihood of water collecting in the line. (See \"Background\")\n\nAnalytical note (purpose claims and practical effects):\n\n- The directive explicitly claims the change reduces the chance of water being trapped in the pitot/static lines (\"Background\"). That is the stated safety rationale and the mechanical change (shorter hoses) is proportionate to that goal.\n\n- Who pays: Aircraft operators/owners pay for the parts and labour to carry out the modification. The work will typically be performed by a licensed maintenance organisation (MRO) authorised to perform BAe modifications. (See \"Requirement\" and industry practice.)\n\n- Who decides and enforces: The regulator (Civil Aviation Safety Authority via this Airworthiness Directive) requires compliance; operators must schedule and complete the work and record compliance in maintenance logs. The directive references BAe service bulletins as the method of compliance. (See \"Requirement\" and \"Compliance\")\n\n- Cost, downtime and supply effects: The directive imposes a one-time retrofit on affected aircraft. Costs are concentrated on the owners/operators of affected BAe 146s. Demand for the specific hoses/parts and MRO capacity may rise temporarily. For new-build aircraft listed by constructor number the modification was incorporated prior to delivery, shifting the cost onto the manufacturer for those serial numbers. (See \"Note\" under Applicability.)\n\n- Implementation risks and compliance burden: The mechanical change is narrowly scoped (replace hoses per a specific service bulletin). Implementation risk rests mainly on availability of parts, scheduling with an authorised maintainer, and correct installation per the SB. Misinstallation or use of non-conforming parts would reduce the intended effect.\n\n- Effects on private choice and market competition: The directive mandates a technical standard for specific aircraft configurations, reducing operator discretion on that point. It creates predictable demand for authorised BAe parts and qualified maintenance services for the modification; it does not directly regulate pricing or broader competitive behaviour in the MRO market.\n\n- Trade-offs and opportunity costs: The immediate trade-off is paying for parts and maintenance time now to reduce the future risk of water accumulation in pitot/static lines. There is no continuing regulatory burden after the one-off modification other than normal continued airworthiness obligations.\n\n- Concentrated benefits and diffuse costs: Benefits (reduced water-trap risk) accrue directly to each modified aircraft (owners, pilots, passengers). Costs are concentrated on the owners/operators of the listed BAe 146 aircraft. The directive does not create an ongoing recurring fee or reporting burden beyond the standard maintenance record requirements.\n\nSource references within the directive: \"Applicability\", \"Requirement\", \"Compliance\", \"Background\", and the Service Bulletin references (SB.34-131-46041A and its Revision 2)."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific technical issue (water trapping in hoses) caused by a specific equipment relocation. The scope remains tightly focused on the original safety concern without expansion into unrelated systems or broader operational requirements."},"complexity_factors":["Highly specific applicability criteria requiring cross-referencing of multiple modification service bulletins (4 different modification numbers)","Serial number-based exemptions requiring operators to check constructor numbers against 3 separate lists","Technical aviation terminology throughout (pitot-static system, True Airspeed Computer, Mode S transponder, drain valve)","References to external technical documents (British Aerospace Service Bulletins) that contain the actual implementation instructions","Conditional compliance language ('Unless previously accomplished')","Nested conditions in applicability: must have BOTH specific TAS computer modification AND specific transponder modification"],"plain_english_summary":"This CASA Airworthiness Directive mandates replacing certain pitot‑static flexible hoses on specified British Aerospace BAe 146 Series aircraft that have a particular True Airspeed computer and Dual Mode 'S' transponder combination (some newer serials exempt). \n\nOwners/operators must install shorter pitot/static lines per British Aerospace service instructions to eliminate a water‑trap that can freeze and give false airspeed/altitude indications. Compliance was required by 31 December 1996."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bae-146-63-pitot-static-system-true-airspeed-computer-no-1","history":"/api/acts/ad-bae-146-63-pitot-static-system-true-airspeed-computer-no-1/history","analysis":"/api/acts/ad-bae-146-63-pitot-static-system-true-airspeed-computer-no-1/analysis","conflicts":"/api/acts/ad-bae-146-63-pitot-static-system-true-airspeed-computer-no-1/conflicts","importantCases":"/api/acts/ad-bae-146-63-pitot-static-system-true-airspeed-computer-no-1/important-cases","documents":"/api/acts/ad-bae-146-63-pitot-static-system-true-airspeed-computer-no-1/documents"}}