Airworthiness Directive · Amendment 39-18268 · Air conditioning
The Boeing Company Airplanes
This AD applies to The Boeing Company Model 747-400 and -400F series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 747-21A2523, Revision 2, dated June 7, 2013.
We are superseding Airworthiness Directive (AD) 2012-24-10 for certain The Boeing Company Model 747-400 and -400F series airplanes. AD 2012-24-10 required installing new software, replacing the duct assembly with a new duct assembly, making wiring changes, and routing certain wire bundles. This new AD retains the requirements of AD 2012- 24-10 and requires installing a new or serviceable pressure switch bracket and altitude pressure switch. This new AD also adds an airplane to the applicability. This AD was prompted by reports of intermittent or blank displays of a certain integrated display unit (IDU) that were due to an intermittent false electrical ground that was not addressed by the software installation or wiring changes required by AD 2012-24- 10. We are issuing this AD to prevent IDU malfunctions, which could affect the ability of the flightcrew to read primary displays for airplane attitude, altitude, or airspeed, and consequently reduce the ability of the flightcrew to maintain control of the airplane.
This paragraph restates the requirements of paragraph (g) of AD 2012-24-10, Amendment 39-17280 (77 FR 73908, December 12, 2012), with revised service information. Within 12 months after January 16, 2013 (the effective date of AD 2012-24-10), except as provided by paragraph (j) of this AD: Install integrated display system software, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-21A2523, Revision 1, dated October 3, 2011; or Boeing Alert Service Bulletin 747-21A2523, Revision 2, dated June 7, 2013. As of the effective date of this AD, only Boeing Alert Service Bulletin 747-21A2523, Revision 2, dated June 7, 2013, may be used to accomplish the actions required by this paragraph.
Note 1 to paragraphs (g) and (j) of this AD: Boeing Alert Service Bulletin 747-21A2523, Revision 1, dated October 3, 2011; and Boeing Alert Service Bulletin 747-21A2523, Revision 2, dated June 7, 2013; refer to Boeing Service Bulletin 747-31-2426, dated July 29, 2010 (for airplanes with Rolls-Royce engines); Boeing Service Bulletin 747-31-2427, dated July 29, 2010 (for airplanes with General Electric engines); and Boeing Service Bulletin 747-31-2428, dated July 29, 2010 (for airplanes with Pratt & Whitney engines); as additional sources of guidance for the software installation specified by paragraph (g) of this AD.
This paragraph restates the requirements of paragraph (h) of AD 2012-24-10, Amendment 39-17280 (77 FR 73908, December 12, 2012), with revised service information. Within 60 months after January 16, 2013 (the effective date of AD 2012-24-10), except as provided by paragraph (j) of this AD: Replace the duct assembly with a new duct assembly, do wiring changes, and route certain wire bundles, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-21A2523, Revision 1, dated October 3, 2011; or Boeing Alert Service Bulletin 747-21A2523, Revision 2, dated June 7, 2013. As of the effective date of this AD, only Boeing Alert Service Bulletin 747-21A2523, Revision 2, dated June 7, 2013, may be used to accomplish the actions required by this paragraph.
Within 60 months after the effective date of this AD: Install a new or serviceable pressure switch bracket and a new or serviceable altitude pressure switch on the forward side of the station 400 bulkhead, do wiring changes, route certain wire bundles, install a new hose assembly, and perform a leak check and a functional logic test, in accordance with the Accomplishment Instructions of the service information specified in paragraph (i)(1) or (i)(2) of this AD, as applicable.
(1) For Model 747-400F series airplanes: Boeing Special Attention Service Bulletin 747-21-2532, dated February 13, 2014.
(2) For Model 747-400BCF series airplanes: Boeing Special Attention Service Bulletin 747-21-2533, dated February 13, 2014.
For Group 21 airplanes, as identified in Boeing Alert Service Bulletin 747-21A2523, Revision 2, dated June 7, 2013, do the actions specified in paragraphs (j)(1) and (j)(2) of this AD, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-21A2523, Revision 2, dated June 7, 2013.
(1) Within 12 months after the effective date of this AD, install integrated display system software.
(2) Within 60 months after the effective date of this AD, replace the duct assembly with a new duct assembly, do wiring changes, and route certain wire bundles.
