AD 2006-21-05

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, accomplish the following:

(a) For Model 747-400 series airplanes identified as Group 1 in Boeing Service Bulletin 747-21A2414, Revision 3, dated May 12, 2006: Within 90 days after the effective date of this AD, do the replacement specified in paragraph (a)(1) or (a)(2) 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 March 15, 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 July 29, 1999.

Note 1: Boeing Service Bulletin 747-21A2414, Revision 3, dated May 12, 2006, specifies Group 1 as “all 747-400 airplanes with Hamilton Sundstrand flight deck humidifier 821486-01.” The correct part number (P/N) for the humidifier is 821486-1.

(1) 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, dated May 12, 2006.

(2) 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, dated May 12, 2006.

Note 2: Boeing Service Bulletin 747-21A2414, Revision 3, dated May 12, 2006, refers to Boeing Service Bulletin 747-21-2405, Revision 4, dated July 29, 1999, as an additional source of service information for deactivating the humidifier.

Note 3: Boeing Service Bulletin 747-21A2414, Revision 3, dated May 12, 2006, refers to Hamilton Sundstrand Service Bulletin 821486-21-01, dated March 15, 2000, as an additional source of service information for the cell stack replacements.

(b) 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 applicable requirements of paragraphs (a)(1) and (a)(2) of this AD.

(c) For Model 747-400 series airplanes identified as Groups 2 and 3 in Boeing Service Bulletin 747-21A2414, Revision 3, dated May 12, 2006: Within 90 days after the effective date of this AD, 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, dated May 12, 2006. Instead of inspecting the flight deck humidifier, a review of airplane 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 airplane.

(1) 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 paragraph.

(2) 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 airplane 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 paragraph.

(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 paragraph (a) of this AD.

(d) For Model 777-200 and 777-300 series airplanes identified as Groups 1 through 5 in Boeing Service Bulletin 777-21A0048, Revision 3, dated May 12, 2006: Within 90 days after the effective date of this AD, do the replacement specified in paragraph (d)(1) or (d)(2) of this AD. For flight deck humidifiers with a blanking plate: If a blanking plate is removed and a new or supplier-tested cell stack installed, the cell stack installation must be done in accordance with Part 3 of the Accomplishment Instructions of Boeing Service Bulletin 777-21A0048, Revision 3, dated May 12, 2006; and after the installation, the humidifier system may be activated in accordance with Accomplishment Instructions of Boeing Service Bulletin 777-21-0035, Revision 1, dated October 19, 2000.

(1) Replace the cell stack with a blanking plate, in accordance with Part 1 of the Accomplishment Instructions of Boeing Service Bulletin 777-21A0048, Revision 3, dated May 12, 2006; and, before further flight, deactivate the humidifier system in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, or in accordance with data meeting the certification basis of the airplane approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization who has been authorized by the Manager, Seattle ACO, to make those findings. For a deactivation method to be approved, the deactivation must meet the certification basis of the airplane, and the approval must specifically reference this AD.

(2) Replace the cell stack with a supplier-tested cell stack, in accordance with Part 2 of the Accomplishment Instructions of Boeing Service Bulletin 777-21A0048, Revision 3, dated May 12, 2006.

Note 4: Boeing Service Bulletin 777-21A0048, Revision 3, dated May 12, 2006, refers to Hamilton Sundstrand Service Bulletin 816086-21-01, dated March 15, 2000, as an additional source of service information for the cell stack replacement.

(e) Replacement of the cell stack before the effective date of this AD in accordance with Boeing Service Bulletin 777-21A0048, Revision 1, dated September 7, 2000; or Boeing Alert Service Bulletin 777-21A0048, Revision 2, dated July 14, 2005; is acceptable for compliance with the applicable requirements of paragraphs (d)(1) and (d)(2) of this AD.

(f) For Model 777-200 and 777-300 series airplanes identified as Groups 6 and 7 in Boeing Service Bulletin 777-21A0048, Revision 3, dated May 12, 2006: Within 90 days after the effective date of this AD, inspect the flight deck humidifier to determine if it is P/N 816086-1, in accordance with Part 4 of the Accomplishment Instructions of Boeing Service Bulletin 777-21A0048, Revision 3, dated May 12, 2006. Instead of inspecting the flight deck humidifier, a review of airplane 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 airplane.

(1) If a P/N other than P/N 816086-1 is installed or if the flight deck humidifier is not installed, no further action is required by this paragraph.

(2) If P/N 816086-1 is installed, inspect the flight deck humidifier cell stack to determine whether P/N 822976-2 is installed and “DEV 13433” is not marked next to the cell stack P/N, in accordance with Part 4 of the Accomplishment Instructions of the service bulletin. Instead of inspecting the flight deck humidifier cell stack, a review of airplane 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 822976-3 or 1003111-1, or if “DEV 13433” is marked next to P/N 822976-2, no further action is required by this paragraph.

(ii) If the cell stack has P/N 822976-2 and does not have “DEV 13433” marked next to the cell stack P/N, before further flight, do the replacement specified in paragraph (d) of this AD. Doing the replacement of the cell stack with a blanking plate, in accordance with paragraph 3.A. of the Accomplishment Instructions of Hamilton Sundstrand Service Bulletin 816086-21-01, dated March 15, 2000; and the deactivation of the humidifier system, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 777-21-0087, dated June 17, 2004; is acceptable for compliance with paragraph (d)(1) of this AD for those Group 7 airplanes listed in Boeing Service Bulletin 777-21-0087, dated June 17, 2004.

(g) Inspections accomplished before the effective date of this AD in accordance with Boeing Alert Service Bulletin 747-21A2414, Revision 2, dated July 7, 2005, are considered acceptable for compliance with the corresponding action specified in paragraph (c) of this AD.

(h) Inspections accomplished before the effective date of this AD in accordance with Boeing Alert Service Bulletin 777-21A0048, Revision 2, dated July 14, 2005, are considered acceptable for compliance with the corresponding action specified in paragraph (f) of this AD.

(i) On Model 747-400 series airplanes: As of the effective date of this AD, no person may 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.

(j) On Model 777-200 and 777-300 series airplanes: As of the effective date of this AD, no person may install a flight deck humidifier cell stack having P/N 822976-2, unless “DEV 13433” is also marked next to the cell stack P/N.

(k)(1) In accordance with 14 CFR 39.19, the Manager, Seattle ACO, is authorized to approve alternative methods of compliance for this AD.

(2) Before using any AMOC approved in accordance with 14 CFR 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office.

(l) Unless otherwise specified in this AD, the actions must be done in accordance with the applicable service bulletins listed in Table 1 of this AD. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. To get copies of this service information, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. To inspect copies of this service information, go to the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. For information on the availability of this material at the NARA, call (202) 741-6030, or go to http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.