{"id":"F2008L00532","name":"AD/B747/370 - Heat Exchanger Shells","slug":"ad-b747-370-heat-exchanger-shells","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":119416,"registerId":"commonwealth-F2008L00532-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Boeing 747 Series Aeroplanes","sectionType":"division","heading":"Boeing 747 Series Aeroplanes","content":"### Boeing 747 Series Aeroplanes\n\n| AD/B747/370 | Heat Exchanger Shells | 3/2008 |\n| ----------- | --------------------- | ------ |\n\n| Applicability: | Boeing Model 747-400 series aeroplanes, as identified in Boeing Service Bulletin (SB) 747-21A2439, Revision 2, dated 24 May 2007. |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement: | 1. Do the actions sspecified in 1a) and 1b) of this AD by accomplishing all the actions specified in the Accomplishment Instructions of the service bulletin.a) Do repetitive general visual inspections to detect discrepancies (i.e., cracks, creases, deformation, deflection, and interference with the rudder and/or elevator cables) of the forward and rear heat exchanger shells of the air distribution system of the crew rest area, and do the applicable corrective actions, until the actions required by 1b) of this AD are done.b) Do an inspection to identify the part number, shop code, and build date of the forward and rear heat exchanger shells of the air distribution system of the crew rest area, and do the applicable corrective actions.Accomplishing the actions in Requirement 1b) ends the repetitive inspections as detailed in Requirement 1a) of this AD.Actions done before the effective date of this AD in accordance with Boeing Alert Service Bulletin 747-21A2439, dated 3 November 2005; or Boeing Service Bulletin 74721A2439, Revision 1, dated 24 July 2006; are acceptable for compliance with the corresponding actions specified in this AD.If a forward heat exchanger shell, part number 65B41601-52, is found installed during the replacement required by AD/B747/232 Amdt 1, or was installed during the inspection required by AD/B747/232 Amdt 1 (AD/B747/232 Amdt 1 refers to Boeing Alert Service Bulletin 747-21A2412, dated 20 January 2000; or Revision 2, dated30 November 2000; as the appropriate sources of service information for accomplishing the required actions): Actions detailed in Requirements 1a) and 1b) of this AD are not required for that forward heat exchanger shell only.2. Do not install a heat exchanger shell having a part number identified in the “Existing Part Number” column of the table specified in paragraph 2.C. of Boeing Service Bulletin 747-21A2439, Revision 2, on any aeroplane.Note: FAA AD 2007-25-19 Amdt 39-15301 dated 30 November 2007 refers. |\n\n| Compliance: | 1. At the applicable times specified in the Table 1 of paragraph 1.E. of Boeing Service Bulletin 747-21A2439, Revision 2, except where Boeing Service Bulletin 747-21A2439, Revision 2, specifies a compliance time “after the release date of the service bulletin” or “after the date of Revision 02 of the service bulletin,” this AD requires compliance within the specified compliance time after the effective date of this AD.The applicable corrective actions must be done before further flight.2. From the effective date of this AD. |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| | This Airworthiness Directive becomes effective on 13 March 2008. |\n| Background: | The FAA has received a report of an uncommanded up and down pitch movement of an aeroplane in flight and resistance in the elevator controls on the ground during taxi. The issuing of this AD is intended to prevent cracking and buckling of the forward or rear heat exchanger shell of the air distribution system of the crew rest area, which could result in jamming of the rudder and/or elevator control cables and consequent reduced controllability of the aeroplane. |\n\n![](image.001.png) \nCharles Lenarcic \nDelegate of the Civil Aviation Safety Authority\n\n21 January 2008","sortOrder":0},{"sectionNumber":"AD/B747/370","sectionType":"part","heading":"AD/B747/370","content":"## AD/B747/370","sortOrder":1},{"sectionNumber":"Heat Exchanger Shells","sectionType":"part","heading":"Heat Exchanger Shells","content":"## Heat Exchanger Shells","sortOrder":2},{"sectionNumber":"3/2008","sectionType":"part","heading":"3/2008","content":"## 3/2008","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific safety defect in heat exchanger shells on Boeing 747-400 aircraft. The references to prior directives (AD/B747/232) and alternative compliance paths represent standard aviation regulatory practice for avoiding redundant work, not scope creep."},"complexity_factors":["Multiple cross-references to external Boeing Service Bulletins (747-21A2439 Revision 2, and earlier versions)","Conditional logic: Requirement 1b) terminates the repetitive inspections required by 1a)","Exception clause: Specific exemption for forward heat exchanger shells already addressed under previous directive AD/B747/232 Amdt 1","Dual compliance timelines: one for inspections (based on flight hours/cycles per Boeing tables) and one for installation prohibition (from effective date)","Technical aviation terminology requiring specialized knowledge (heat exchanger shells, shop codes, build dates, rudder/elevator cables)","Incorporation by reference to FAA AD 2007-25-19, creating transnational regulatory dependency"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspections and, where needed, replacement of specific heat exchanger shells in the crew rest area of Boeing 747-400s because cracked or deformed shells can interfere with rudder/elevator control cables. It affects operators of 747-400s using the parts identified in Boeing Service Bulletin 747-21A2439, requires repetitive inspections until permanent fixes, and orders corrective work before the aircraft may next fly to prevent possible loss of control."},"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":7,"scope_assessment":{"changed":true,"description":"This AD expands and clarifies operational obligations compared with earlier service guidance by (a) mandating part identification/repair as a way to end repetitive inspections (Requirement 1a/1b), (b) prohibiting future installation of parts listed in the service bulletin table (Requirement 2), and (c) explicitly accepting prior actions done under earlier service bulletins while carving out an exemption when part 65B41601-52 was installed per AD/B747/232 Amdt 1 (Requirement 1). These elements alter compliance pathways and installation permissions relative to prior measures."},"complexity_factors":["Dependence on external service document for applicability and actions (Boeing Service Bulletin 747-21A2439, Revision 2) (Applicability; Requirement 1; Compliance).","Two-step inspection regime: repetitive general visual inspections until a one-time identification/repair ends them (Requirement 1a and 1b).","Technical identification requirement: must record part number, shop code and build date to stop repetitive inspections (Requirement 1b).","Conditional exemption tied to another AD and specific part number (65B41601-52) installed per AD/B747/232 Amdt 1 (Requirement 1).","Prohibition on installing parts listed in a specific table of the service bulletin (Requirement 2), requiring cross-referencing SB paragraph 2.C.","Acceptance of earlier service bulletin compliance for meeting current AD obligations creates multiple compliance pathways (Requirement 1).","Operational constraint that corrective actions must be completed before further flight increases potential grounding and logistic cost (Compliance).","Compliance timing references a table in the service bulletin with caveats about wording (Compliance: Table 1 of paragraph 1.E.)."],"plain_english_summary":"This AD requires operators of Boeing 747‑400 series aeroplanes (as listed in Boeing Service Bulletin 747‑21A2439 Rev 2) to inspect forward and rear crew‑rest heat exchanger shells for cracks, deformation or interference, identify part number/shop code/build date, carry out corrective actions, and forbids installation of certain existing part numbers. Repetitive inspections stop once identification/repairs required by the AD are done.\n\nIt states the aim is to prevent shell cracking that could jam rudder/elevator cables. Operators pay for inspections/repairs; compliance times and methods are set by the referenced Boeing service bulletin."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-370-heat-exchanger-shells","history":"/api/acts/ad-b747-370-heat-exchanger-shells/history","analysis":"/api/acts/ad-b747-370-heat-exchanger-shells/analysis","conflicts":"/api/acts/ad-b747-370-heat-exchanger-shells/conflicts","importantCases":"/api/acts/ad-b747-370-heat-exchanger-shells/important-cases","documents":"/api/acts/ad-b747-370-heat-exchanger-shells/documents"}}