{"id":"F2006B03513","name":"AD/BAe 146/64 - Pitot-Static System - True Airspeed Computer No.2","slug":"ad-bae-146-64-pitot-static-system-true-airspeed-computer-no-2","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":43075,"registerId":"commonwealth-F2006B03513-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BAe 146/64 - Pitot-Static System - True Airspeed Computer No.2","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 146/64 Pitot-Static System \\- True Airspeed Computer No.2\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 2 installed in accordance with BAe Avro modification HCM40160C (SB.34-52-40160C) or HCM40298G 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 constructors number E3198 and subsequent aeroplanes, if the modifications referenced above were also incorporated.\n\nRequirement: Install new pitot and static lines between the TAS 2 unit and the drain valve in accordance with either British Aerospace (Commercial Aircraft) Limited, Modification Service Bulletin SB.34-132-46042A dated 24 June 1991 or British Aerospace, Regional Aircraft Limited, Avro International Division, Modification Service Bulletin SB.34-132-46042A Revision 2 dated 1 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 2 unit being moved from its position on the avionics rack. This resulted in the pitot and static flexible hoses between the TAS 2 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":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The Directive remains narrowly focused on correcting a water-trap risk created when TAS 2 was relocated after Mode 'S' transponder installation. It does not expand beyond that original safety remediation (no new types of work, broader systems, or additional operational constraints were added). The measure stays within its original purpose of a targeted airworthiness fix."},"complexity_factors":["Single clear mandatory action (replace pitot/static hoses)","Narrow applicability defined by four specific BAe modification numbers and series models","References to two BAe Service Bulletins (original and a revision) for technical procedure","Short document with limited cross-references (main external references are the Service Bulletins and prior BAe modifications)","Includes a compliance deadline and an effective date"],"plain_english_summary":"**What this directive does (mechanically)**\n\n- Requires the replacement of the pitot and static flexible hoses between the True Airspeed (TAS) Computer No. 2 and the drain valve on certain BAe 146 aeroplanes.\n- The replacement must follow the procedures and parts listed in one of two British Aerospace (BAe) Service Bulletins (SB.34-132-46042A dated 24 June 1991, or Revision 2 dated 1 July 1996).\n\n**Which aircraft are affected**\n\n- BAe 146 Series 100, 100A, 200, 200A, 300 and 300A aircraft only if BOTH of the following are true:\n  - A TAS Computer No. 2 was installed by BAe Avro modification HCM40160C (or HCM40298G), and\n  - A Dual Mode 'S' transponder was installed by BAe Avro modification HCM30118B (or HCM40277A).\n- Aircraft delivered from constructor number E3198 onward already had these modifications fitted if the above modifications were incorporated before delivery (so the Directive’s work may already have been done on some newer airframes).\n\n**Why the change was required (stated reason)**\n\n- When the Mode 'S' transponder was fitted, the TAS 2 unit was moved on the avionics rack. That relocation produced longer pitot/static flexible hoses that could trap water between the TAS unit and the drain valve. The new, shorter hoses are intended to reduce the risk of water accumulation in those lines.\n\n**Who pays and who decides**\n\n- Aircraft operators or the aircraft owner pay for the parts and labour to accomplish the hose replacement.\n- The Civil Aviation Safety Authority (CASA) issued the directive; the actual installation work is carried out by maintenance organisations or authorised personnel following the BAe Service Bulletin instructions.\n\n**How it changes behaviour and operations**\n\n- Affected operators must schedule and carry out a one-time maintenance action (hose replacement) compliant with the specified Service Bulletin before the stated compliance date.\n- Aircraft may be unavailable for service while the work is performed, and maintenance records must show compliance in accordance with airworthiness rules.\n\n**Costs, incentives, trade-offs and implementation issues**\n\n- Direct costs: parts (new hoses and any fittings) and maintenance labour. These are concentrated on the operators of the specific affected airframes.\n- Opportunity cost: aircraft downtime while the work is scheduled and carried out (may require out-of-service time or scheduling within existing maintenance checks).\n- Compliance burden: low technical complexity but mandatory—work must be done to the Service Bulletin standard and recorded to maintain legal airworthiness. A certified maintenance organisation or appropriately authorised personnel will generally be required to perform and sign off the work.\n- Implementation risk: incorrect installation or use of non-conforming parts could leave the issue unresolved or create new airworthiness concerns; following the Service Bulletin reduces this risk.\n- Effects on competition and independent providers: independent maintenance organisations can perform the work if they have the necessary approvals and conform to the Service Bulletin, so the measure does not inherently restrict who performs the work.\n\n**Concentrated benefits and diffuse costs**\n\n- The safety benefit (reduced risk of water ingress affecting pitot/static lines and related instruments) accrues to the operators and their passengers/crew and is concentrated in the affected fleet. Costs are concentrated on those same operators.\n\n**Summary assessment**\n\n- This is a narrowly targeted airworthiness action to fix a specific water-trap risk introduced by relocating the TAS 2 unit after installation of Mode 'S' transponders. The directive prescribes a single, mandatory maintenance action using BAe-approved instructions. The principal practical impacts are the cost and downtime for operators, and the requirement that approved maintenance organisations or personnel carry out and record the work in compliance with airworthiness rules.\n\n(References in the directive: sections titled “Applicability”, “Requirement”, “Compliance”, and “Background” describe the affected types, the work required, the time for compliance, and the reason for the change.)"},"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 discrete, targeted safety directive addressing a specific technical defect identified in a specific aircraft configuration. It has not expanded beyond its original purpose of mandating hose replacement to prevent water trapping in the pitot-static system."},"complexity_factors":["Single, specific technical requirement with clear alternative compliance paths (two acceptable Service Bulletin versions)","Narrow applicability limited to specific aircraft series with specific modifications installed","No nested exceptions or conditional logic — straightforward 'if applicable, then comply' structure","Only one defined term requiring explanation (Mode 'S' transponder, explained in context)","Single compliance deadline with simple 'unless previously accomplished' exception","Short document (approximately 250 words) with clear Background section explaining the safety rationale"],"plain_english_summary":"This CASA Airworthiness Directive mandates replacement of over‑long pitot and static hoses to the True Airspeed Computer No. 2 on certain BAe 146 Series 100/200/300 aircraft that have a TAS‑2 installed under the specified mods and a Mode S transponder.  \n\nThe shorter hoses prevent water accumulation that can produce false airspeed/altitude readings — a critical flight‑safety hazard — and must be done per British Aerospace instructions by the directive’s compliance date."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bae-146-64-pitot-static-system-true-airspeed-computer-no-2","history":"/api/acts/ad-bae-146-64-pitot-static-system-true-airspeed-computer-no-2/history","analysis":"/api/acts/ad-bae-146-64-pitot-static-system-true-airspeed-computer-no-2/analysis","conflicts":"/api/acts/ad-bae-146-64-pitot-static-system-true-airspeed-computer-no-2/conflicts","importantCases":"/api/acts/ad-bae-146-64-pitot-static-system-true-airspeed-computer-no-2/important-cases","documents":"/api/acts/ad-bae-146-64-pitot-static-system-true-airspeed-computer-no-2/documents"}}