{"id":"F2009L02784","name":"AD/B737/358 - Electronic Flight Instrument System Cooling","slug":"ad-b737-358-electronic-flight-instrument-system-cooling","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":79968,"registerId":"commonwealth-F2009L02784-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Boeing 737 Series Aeroplanes","sectionType":"division","heading":"Boeing 737 Series Aeroplanes","content":"### Boeing 737 Series Aeroplanes\n\n| AD/B737/358 | Electronic Flight Instrument System Cooling | 8/2009 |\n| ----------- | ------------------------------------------- | ------ |\n\n| Applicability: | Model 737-300, -400 and -500 series aeroplanes, as identified in Boeing Alert Service Bulletin (ASB) 737-21A1156, Revision 2, dated 11 December 2008.                                                                                                                                                 |\n| -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Modify the control power wiring of the normal supply fan and the low flow sensor for the equipment cooling system of the electronic flight instrument system (EFIS), by doing all the applicable actions specified in the Accomplishment Instructions of ASB 737-21A1156, Revision 2.                 |\n|                | For all aeroplanes - Actions accomplished before the effective date of this Directive in accordance with Boeing ASB 737-21A1156, Revision 1, dated 23 October 2007, are acceptable for compliance with the corresponding requirements of this Directive.                                              |\n|                | For Groups 1 and 2 aeroplanes identified in Boeing ASB 737-21A1156, Revision 1 - Actions accomplished before the effective date of this Directive in accordance with Boeing ASB 737-21A1156, dated 20 June 2006, are acceptable for compliance with the corresponding requirements of this Directive. |\n|                | Later revisions of the ASB 737-21A1156, approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2009-12-05 are considered acceptable for compliance with the equivalent Requirements of this Directive.                             |\n|                | Note: FAA AD 2009-12-05 Amdt 39-15928 refers.                                                                                                                                                                                                                                                         |\n| Compliance:    | Within 24 months after the effective date of this Directive.                                                                                                                                                                                                                                          |\n|                | This Airworthiness Directive becomes effective on 30 July 2009.                                                                                                                                                                                                                                       |\n\n| Background: | This Directive results from a report of loss of both the normal EFIS cooling supply and the indication of EFIS cooling loss due to a single failure of the battery bus, causing eventual power-down of the EFIS displays. The standby attitude indication is also powered by this battery bus. This Directive is issued to prevent loss of all attitude indications from both the standby indicator and EFIS displays, which could decrease the ability of the flightcrew to maintain the safe flight and landing of the aeroplane. |\n| ----------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n16 June 2009","sortOrder":0},{"sectionNumber":"AD/B737/358","sectionType":"part","heading":"AD/B737/358","content":"## AD/B737/358","sortOrder":1},{"sectionNumber":"Electronic Flight Instrument System Cool","sectionType":"part","heading":"Electronic Flight Instrument System Cooling","content":"## Electronic Flight Instrument System Cooling","sortOrder":2},{"sectionNumber":"8/2009","sectionType":"part","heading":"8/2009","content":"## 8/2009","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The Directive targets the same class of aeroplanes identified in the Boeing ASB and requires the specified wiring modification to EFIS cooling. It accepts earlier ASB revisions and FAA‑approved AMOCs for compliance but does not expand the affected fleet or add other systems beyond those named in the ASB and the Directive."},"complexity_factors":["Technical electrical modification to EFIS cooling wiring (safety‑critical avionics).","Applicability tied to aeroplanes identified in a specific Boeing ASB (requires cross‑checking serials in the ASB).","Multiple acceptable ASB revisions and acceptance of earlier compliance actions increase compliance-path options and recordkeeping complexity.","Interplay with FAA AD 2009-12-05 and acceptance of FAA‑approved AMOCs creates regulatory coordination requirements.","Fixed compliance timeframe (24 months) and effective date require scheduling within maintenance programs.","Work likely requires qualified maintenance personnel and potential aircraft downtime, imposing direct cost on operators."],"plain_english_summary":"Requires operators of Boeing 737-300, -400 and -500 aeroplanes (as identified in Boeing ASB 737-21A1156 Rev 2) to modify the control-power wiring for the EFIS cooling fan and the low‑flow sensor. CASA sets a 24‑month compliance deadline to prevent simultaneous loss of EFIS and the standby attitude indication; operators pay for and must follow the Boeing Alert Service Bulletin or acceptable earlier revisions / FAA‑approved AMOCs."},"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":3,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — a specific wiring modification for a specific safety issue on specific aircraft models. The grandfathering provisions for earlier service bulletin revisions and FAA-approved alternatives are standard aviation regulatory practice for ensuring continuity of compliance, not scope creep."},"complexity_factors":["Single technical requirement with clear cross-reference to external Boeing document (ASB 737-21A1156)","Three alternative compliance pathways (Revision 1, original ASB for Groups 1-2, and FAA AMOC)","Limited defined scope: only three specific aircraft models (-300, -400, -500 series)","Simple temporal compliance structure (single 24-month deadline)","No nested exceptions or conditional logic beyond the grandfathering provisions for prior work","Background explanation is straightforward safety rationale without regulatory cross-references"],"plain_english_summary":"This CASA Airworthiness Directive mandates rewiring the cooling-fan and sensor circuits in the EFIS on certain Boeing 737-300/400/500 aircraft to eliminate a single-failure that could disable both main flight displays and the standby attitude indicator. It affects owners/operators covered by Boeing ASB 737-21A1156 (Rev 2), required within 24 months of 30 July 2009 (by July 2011); prior FAA-approved or earlier-bulletin work remains acceptable."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-358-electronic-flight-instrument-system-cooling","history":"/api/acts/ad-b737-358-electronic-flight-instrument-system-cooling/history","analysis":"/api/acts/ad-b737-358-electronic-flight-instrument-system-cooling/analysis","conflicts":"/api/acts/ad-b737-358-electronic-flight-instrument-system-cooling/conflicts","importantCases":"/api/acts/ad-b737-358-electronic-flight-instrument-system-cooling/important-cases","documents":"/api/acts/ad-b737-358-electronic-flight-instrument-system-cooling/documents"}}