Document ID: chunk:federal_register_of_legislation:F2007L02359:body:0:p2
Version: federal_register_of_legislation:F2007L02359
Segment Type: other
Provision Reference: 
Character Range: 2945–5848

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.

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.
             This Airworthiness Directive becomes effective on 30 August 2007.
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,