{"id":"F2006B03211","name":"AD/B747/317 - Inadvertent Commanded Shutdown of the Engine Bleed Air Systems","slug":"ad-b747-317-inadvertent-commanded-shutdown-of-the-engine-bleed-air-systems","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42583,"registerId":"commonwealth-F2006B03211-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/317 - Inadvertent Commanded Shutdown of the Engine Bleed Air Systems","content":"![](image.001.png)\n\n![](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 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\nBoeing 747 Series Aeroplanes\n\nAD/B747/317 Inadvertent Commanded Shutdown of the\n\nEngine Bleed Air Systems\n\n  \n13/2004\n\nApplicability: Boeing Model 747-400, \\-400D and –400F series aircraft as listed in Boeing Service Bulletin (SB) 747-36A2136 Revision 2, dated 13 May 2004.\n\nRequirement: 1. Perform the following modifications and functional tests of the wiring of the wire integration unit (WIU) and the air supply control test unit (ASCTU) of the engine bleed air distribution system in accordance with the Accomplishment Instructions of Boeing SB 747-36A2136, Revision 2:\n\n    (a) remove the existing ASCTU,\n\n    (b) do the wiring changes between the WIU and ASCTU and the wiring changes to the WIU,\n\n    (c) do the resistance tests, and\n\n    (d) install a new or reworked ASCTU.\n\n    2. After accomplishing paragraphs 1(b), 1(c) and 1(d) of this AD perform the post- installation tests in accordance with SB 747-36A2136.\n\nNote 1: Modifications and tests accomplished before the effective date of this AD in accordance with Boeing Alert Service Bulletin 747-36A2136, dated April 12, 2001; or Revision 1, dated January 17, 2002; are considered acceptable for compliance with the corresponding actions specified in Requirement 1 of this AD, provided the resistance tests were done with the ASCTU removed.\n\n    3. If the resistance tests were done with the ASCTU installed, perform the following actions in accordance with the Accomplishment Instructions of SB\n\n747-36A2136, Revision 2.\n\n    (a) remove the existing ASCTU,\n\n    (b) do the resistance tests, and\n\n    (c) reinstall the ASCTU.\n\nBoeing 747 Series Aeroplanes\n\nAD/B747/317 (continued)\n\n    4. After accomplishing paragraph 3(c) of this AD perform the post-installation tests in accordance with SB 747-36A2136, Revision 2.\n\n    5. An ASCTU having a part number listed in the \"Old Part Number\" column in the table specified in paragraph 3.C. of the Accomplishment Instructions of Hamilton Sundstrand Service Bulletin 36-186, dated 30 March 30 2001, shall not be installed on any aircraft.\n\nNote 2: FAA AD 2004-22-04 Amdt 39-13832 refers.\n\nCompliance: Requirement 1. Within 18 months after the effective date of this AD. Requirement 2. Before further flight following completion of Requirement 1\\. Requirement 3. Within 18 months after the effective date of this AD. Requirement 4: Before further flight following completion of Requirement 3\\. Requirement 5: From the effective date of this AD.\n\nThis Airworthiness Directive becomes effective on 23 December 2004.\n\nBackground: Boeing has advised that an engine configuration wiring fault could cause the ASCTU to erroneously identify the engine type fitted to the aircraft resulting in an inadvertent commanded shutdown of the engine bleed air distribution systems. This may cause depressurisation of the aircraft and ice build-up on the engine inlets during descent, which could result in ingestion of ice into the engine(s) and consequent loss of thrust on one or more engines.\n\n![Signature of James Coyne, Delegate of the Civil Aviation Safety Authority.](image.002.png)  \n\nJames Coyne\n\nDelegate of the Civil Aviation Safety Authority 11 November 2004\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 1 December 2004.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The AD remains focused on correcting a specific unsafe condition (inadvertent commanded shutdown of engine bleed air systems caused by wiring/ASCTU issues) for the listed Boeing 747-400 series aircraft. It clarifies compliance by specifying the required Service Bulletin revision, enumerates the test conditions that determine whether repeat work is needed, and prohibits installation of certain old ASCTU part numbers. Those are refinements to how the original safety objective is implemented, not an expansion of the AD's substantive scope to other systems or aircraft types."},"complexity_factors":["Directives tied to external documents: references to Boeing SB 747-36A2136 Revision 2 and Hamilton Sundstrand SB 36-186","Conditional compliance based on how earlier work was done (resistance tests performed with ASCTU installed vs removed)","Multiple sequential actions required (remove ASCTU; wiring changes; resistance tests; install new/reworked ASCTU; post-installation functional tests)","Several different compliance timepoints (primary work within 18 months; post-installation tests before further flight; prohibition effective immediately)","Prohibition on installing ASCTUs having certain old part numbers (cross-references a parts table in an external SB)","Reference to equivalent FAA AD (cross-jurisdictional linkage that may affect interpretation)"],"plain_english_summary":"**What this direction does (plain terms)**\n\n- This is an Airworthiness Directive (a legally binding safety order for aircraft operators) that requires specific wiring changes and unit replacements on certain Boeing 747-400 series aeroplanes to prevent the engine bleed air systems being shut down by mistake.\n\n**Who it affects**\n\n- Owners, operators and maintainers of Boeing Model 747-400, -400D and -400F aircraft listed in Boeing Service Bulletin (SB) 747-36A2136 Revision 2. It also affects maintenance organisations that supply or install the affected Air Supply Control Test Unit (ASCTU).\n\n**Why it matters**\n\n- A wiring fault can make the ASCTU incorrectly identify the engine type and inadvertently command the shutdown of the engine bleed air distribution systems. That failure can lead to aircraft depressurisation and ice build-up on engine inlets during descent. Ice ingestion could damage engines and cause loss of thrust on one or more engines.\n\n**What operators must do (mechanics of compliance)**\n\n- Carry out the modifications and functional tests specified in Boeing SB 747-36A2136 Revision 2, namely:\n  - remove the existing ASCTU,\n  - perform wiring changes between the Wire Integration Unit (WIU) and the ASCTU and wiring changes to the WIU,\n  - perform the resistance tests called for in the Service Bulletin,\n  - install a new or reworked ASCTU,\n  - and then complete the post-installation functional tests.\n\n- If earlier Service Bulletin revisions were used to carry out the work before this AD took effect, those earlier works are acceptable only if the resistance tests were done with the ASCTU removed. If resistance tests were done with the ASCTU installed, the AD requires removing the ASCTU, repeating the resistance tests, reinstalling the ASCTU and performing the post-installation tests.\n\n- Do not install ASCTU units with the “old” part numbers listed in Hamilton Sundstrand Service Bulletin 36-186 (30 March 2001).\n\n**Timing and enforcement**\n\n- The primary modifications and tests must be completed within 18 months from the AD’s effective date. Post-installation tests must be done before the aircraft next flies after the work. The prohibition on installing listed old ASCTU part numbers applies from the AD’s effective date.\n\n**Who pays and who decides**\n\n- Aircraft operators pay for the parts, labour and aircraft downtime required to perform the wiring changes, ASCTU replacement/rework and testing. The Civil Aviation Safety Authority (CASA), through its delegate, determines the required corrective actions and enforces compliance.\n\n**Costs, incentives and practical trade-offs**\n\n- Direct costs: purchase or rework of ASCTUs, wiring labour, and the fit-test cycles. Operators also incur opportunity costs from aircraft being out of service while modifications and testing are done.\n\n- Incentives and substitution: operators facing high modification cost or scarce parts may defer compliance until the last allowable moment, source reworked units, or consider routing the aircraft out of service permanently if that is economically preferable.\n\n- Concentrated benefits and diffuse costs: the immediate safety benefit accrues to flight crews and passengers and to the operator by reducing accident risk; maintenance shops and OEMs capture the business of parts and labour. The cost burden falls directly and concentratively on the affected operators.\n\n**Implementation risks and compliance friction**\n\n- Requires qualified maintenance personnel and access to specified parts and test equipment. If ASCTU replacements or reworks are in short supply, scheduling and aircraft availability will be affected. Recordkeeping must show which SB revision was used and whether resistance tests were done with the ASCTU removed (because that affects whether repeat work is required).\n\n**Cross-references and authority**\n\n- The AD mandates work in accordance with Boeing SB 747-36A2136 Revision 2 and refers to Hamilton Sundstrand SB 36-186. It also notes an equivalent FAA Airworthiness Directive (FAA AD 2004-22-04)."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope: addressing a specific unsafe wiring condition in the engine bleed air system of Boeing 747-400 series aircraft. The instrument remains tightly focused on the technical defect described in the background section without expanding to cover additional systems or aircraft types."},"complexity_factors":["Single specific aircraft model family (Boeing 747-400 series) with clear applicability","Straightforward sequential requirements (numbered 1-5) with clear dependencies","References to external technical documents (Boeing Service Bulletin 747-36A2136) for detailed instructions rather than embedding them","Simple conditional logic (Note 1 provides alternative compliance path for work done before effective date; Requirement 3 provides conditional path for resistance tests done with ASCTU installed)","Only two defined acronyms (WIU, ASCTU) explained in context","Clear compliance timeline structure with specific deadlines","No nested exceptions or complex cross-referencing between multiple legislative instruments"],"plain_english_summary":"This safety order fixes a dangerous wiring fault in the engine bleed-air control on Boeing 747-400 series jets by requiring wiring modification, replacement or rework of the Air Supply Control Test Unit (ASCTU), and banning certain faulty ASCTU parts.  \n\nIt affects 747-400, 747-400D, and 747-400F operators and prevents erroneous bleed-air shutdowns that could cause depressurisation, inlet icing, or engine damage."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-317-inadvertent-commanded-shutdown-of-the-engine-bleed-air-systems","history":"/api/acts/ad-b747-317-inadvertent-commanded-shutdown-of-the-engine-bleed-air-systems/history","analysis":"/api/acts/ad-b747-317-inadvertent-commanded-shutdown-of-the-engine-bleed-air-systems/analysis","conflicts":"/api/acts/ad-b747-317-inadvertent-commanded-shutdown-of-the-engine-bleed-air-systems/conflicts","importantCases":"/api/acts/ad-b747-317-inadvertent-commanded-shutdown-of-the-engine-bleed-air-systems/important-cases","documents":"/api/acts/ad-b747-317-inadvertent-commanded-shutdown-of-the-engine-bleed-air-systems/documents"}}