{"id":"F2007L02359","name":"AD/B747/359 - Flight Deck Humidifier","slug":"ad-b747-359-flight-deck-humidifier","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":67691,"registerId":"commonwealth-F2007L02359-current","compilationNumber":null,"startDate":"2026-04-02","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/B747/359 | Flight Deck Humidifier | 9/2007 |\n| ----------- | ---------------------- | ------ |\n\n| Applicability: | Boeing Model 747-400 series aeroplanes as identified in Boeing Service Bulletin747-21A2414, Revision 3, dated 12 May 2006. |\n| -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement: | 1. For Model 747-400 series aeroplanes identified as Group 1 in Boeing Service Bulletin 747-21A2414, Revision 3:(a) Do the replacement specified in Requirement 1(b) or 1(c) of this AD. For flight deck humidifiers with a blanking plate: If the blanking plate is removed and a new or supplier-tested cell stack is installed, the replacement must be done in accordance with the Accomplishment Instructions of Hamilton Sundstrand Service Bulletins 821486-21-01, dated 15 March 2000; and after the replacement, the flight deck humidifier may be activated in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-21-2405, Revision 4, dated 29 July 1999.Note 1: Boeing Service Bulletin 747-21A2414, Revision 3, specifies Group 1 as \"all 747-400 aeroplanes with Hamilton Sundstrand flight deck humidifier 821486-01.\" The correct part number (P/N) for the humidifier is 821486-1.(b) Replace the cell stack of the flight deck humidifier with a supplier-tested cell stack, in accordance with Part 1 of the Accomplishment Instructions of Boeing Service Bulletin 747-21A2414, Revision 3.(c) Replace the cell stack of the flight deck humidifier with a blanking plate and, before further flight, deactivate the flight deck humidifier, in accordance with Part 2 of the Accomplishment Instructions of Boeing Service Bulletin 747-21A2414, Revision 3.Note 2: Boeing Service Bulletin 747-21A2414 Revision 3 refers to Boeing Service Bulletin 747-21-2405 Revision 4, as an additional source of service information for deactivating the humidifier.Note 3: Boeing Service Bulletin 747-21A2414 Revision 3 refers to Hamilton Sundstrand Service Bulletin 821486- 21-01, as an additional source of service information for the cell stack replacements. |\n\n| | Replacement of the cell stack before the effective date of this AD in accordance with Boeing Alert Service Bulletin 747- 21A2414, dated April 13, 2000; Revision 1, dated October 26, 2000; or Revision 2, dated July 7, 2005; is acceptable for compliance with the corresponding action specified in Requirement 1 of this AD.2. For Model 747-400 series aeroplanes identified as Groups 2 and 3 in Boeing Service Bulletin 747-21A2414, Revision 3: Inspect the flight deck humidifier to determine whether P/N 821486-1 is installed, in accordance with Part 3 of the Accomplishment Instructions of Boeing Service Bulletin 747-21A2414, Revision 3. Instead of inspecting the flight deck humidifier, a review of aeroplane maintenance records along with any other applicable data is acceptable if the P/N of the flight deck humidifier can be positively determined from that review or if it can be positively determined that the flight deck humidifier is not installed on the aeroplane.(a) If a P/N other than P/N 821486-1 is installed or if the flight deck humidifier is not installed, no further action is required by this Requirement.(b) If P/N 821486-1 is installed, inspect the flight deck humidifier cell stack to determine whether P/N 821482-1 is installed and \"DEV 13433\" is not marked next to the cell stack P/N, in accordance with Part 3 of the Accomplishment Instructions of the service bulletin. Instead of inspecting the flight deck humidifier cell stack, a review of aeroplane maintenance records is acceptable if the P/N, including whether \"DEV 13433\" is marked next to the P/ N, of the flight deck humidifier cell stack can be positively determined from that review.(i) If the cell stack has P/N 821482-2 or 1003111-2, or if \"DEV 13433\" is marked next to P/N 821482-1, no further action is required by this Requirement.(ii) If the cell stack has P/N 821482-1 and does not have \"DEV 13433\" marked next to the cell stack P/N: Before further flight, do the replacement specified in Requirement 1 of this AD.Inspections accomplished before the effective date of this AD in accordance with Boeing Alert Service Bulletin 747-21A2414, Revision 2, dated 7 July 2005, are considered acceptable for compliance with the corresponding action specified in Requirement 2 of this AD.3. Do not install a flight deck humidifier cell stack having P/N 821482-1, unless \"DEV 13433\" is also marked next to the cell stack P/N.Note 4: FAA AD 2006-21-05 dated 6 October 2006 refers. |\n| --- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n| Compliance: | For Requirement 1 and 2:Within 90 days after the effective date of this AD, unless previously accomplished.For Requirement 3:From the effective date of this AD. |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| | This Airworthiness Directive becomes effective on 30 August 2007. |\n| Background: | The requirements detailed in this AD are intended to prevent an increased pressure drop across the humidifier and consequent reduced airflow to the flight deck, which could result in the inability to clear any smoke that might appear in the flight deck. |\n\n![](image.001.png) \nDavid Punshon \nDelegate of the Civil Aviation Safety Authority\n\n26 June 2007","sortOrder":0},{"sectionNumber":"AD/B747/359","sectionType":"part","heading":"AD/B747/359","content":"## AD/B747/359","sortOrder":1},{"sectionNumber":"Flight Deck Humidifier","sectionType":"part","heading":"Flight Deck Humidifier","content":"## Flight Deck Humidifier","sortOrder":2},{"sectionNumber":"9/2007","sectionType":"part","heading":"9/2007","content":"## 9/2007","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":7,"scope_assessment":{"changed":false,"description":"The AD applies to the aeroplanes and parts identified in Boeing Service Bulletin 747-21A2414 Rev 3 and accepts prior listed service-bulletin work as compliant, so it does not expand applicability beyond the referenced service information. The directive consolidates replacement, deactivation and inspection options but does not add aircraft or part numbers outside those in the referenced service bulletins (see Applicability; Requirements; Notes)."},"complexity_factors":["Multiple part-number conditionality: different obligations depending on humidifier P/N (821486-1) and cell stack P/Ns (821482-1, 821482-2, 1003111-2) increase decision complexity (Requirement 2, Requirement 3).","Group-based applicability: aircraft are split into Groups 1–3 per Boeing Service Bulletin 747-21A2414 Rev 3, requiring different actions per group (Applicability; Requirement 1–2).","Alternative compliance paths: operators may either replace cell stack, fit blanking plate and deactivate, or perform inspections/records review as acceptable alternatives (Requirement 1(b)/(c); Requirement 2).","Interdependence on external service bulletins: the AD references multiple Boeing and Hamilton Sundstrand service bulletins and accepts prior revisions as compliant, requiring cross‑checking documents (Notes; Requirement text).","Marking-based exception: permissibility hinges on the presence of the “DEV 13433” marking next to a P/N, creating a narrow evidentiary requirement (Requirement 2(b); Requirement 3).","Timing constraints: a 90‑day mandatory compliance window plus 'before further flight' obligations where unmarked parts are found increases operational scheduling pressure (Compliance).","Record-review option: inspections may be satisfied by maintenance‑record review if positive identification is possible, shifting burden to record accuracy and traceability (Requirement 2)."],"plain_english_summary":"This AD requires operators of Boeing 747-400 aeroplanes fitted with Hamilton Sundstrand flight-deck humidifier P/N 821486-1 to either replace the humidifier cell stack with a supplier‑tested unit or install a blanking plate and deactivate the humidifier; it also mandates inspections for other groups and prohibits installing cell stack P/N 821482-1 unless it is marked “DEV 13433” (Requirements 1–3). Operators must complete required actions within 90 days or, where specified, before further flight; certain earlier service‑bulletin replacements are accepted as compliance."},"kimi_summary":{"content_quality":"ok","complexity_score":6,"scope_assessment":{"changed":false,"description":"This AD maintains a narrow, technical scope focused specifically on flight deck humidifier safety in Boeing 747-400 aircraft. It does not expand beyond its original safety purpose of preventing airflow obstruction in the cockpit. The grouping structure and alternative compliance paths are typical of aviation safety directives and represent standard regulatory precision rather than scope creep."},"complexity_factors":["Multiple aircraft groupings (Groups 1, 2, and 3) with different compliance paths","Nested conditional logic: Requirement 2(b)(i) and 2(b)(ii) create decision trees based on part numbers and markings","Cross-references to three external documents: Boeing Service Bulletin 747-21A2414 Rev 3, Boeing Service Bulletin 747-21-2405 Rev 4, and Hamilton Sundstrand Service Bulletin 821486-21-01","Specific part number dependencies (P/N 821486-1, 821482-1, 821482-2, 1003111-2) and marking requirements (\"DEV 13433\")","Alternative compliance methods allowed (maintenance records review instead of physical inspection)","Grandfathering provisions for work done under earlier revisions of service bulletins before the AD effective date","Multiple action options for Group 1 (replacement with tested stack OR deactivation with blanking plate)"],"plain_english_summary":"This AD mandates inspection and corrective action for certain Hamilton Sundstrand flight deck humidifiers (Boeing 747‑400) that can block cockpit airflow. Operators of affected aircraft must inspect, repair/replace, or deactivate the humidifier to prevent restricted ventilation — a hazard if smoke enters the flight deck. Compliance was required within 90 days of the 30 Aug 2007 effective date, and the faulty cell‑stack part may not be installed thereafter."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-359-flight-deck-humidifier","history":"/api/acts/ad-b747-359-flight-deck-humidifier/history","analysis":"/api/acts/ad-b747-359-flight-deck-humidifier/analysis","conflicts":"/api/acts/ad-b747-359-flight-deck-humidifier/conflicts","importantCases":"/api/acts/ad-b747-359-flight-deck-humidifier/important-cases","documents":"/api/acts/ad-b747-359-flight-deck-humidifier/documents"}}