Airworthiness Directive · Amendment 39-17803 · Equipment/furnishings
The Boeing Company Airplanes
This AD applies to The Boeing Company airplanes, certificated in any category, as specified in paragraphs (c)(1) and (c)(2) of this AD.
(1) Model 747-400F series airplanes, as identified in Boeing Alert Service Bulletin 747-25A3580, Revision 2, dated May 13, 2013.
(2) Model 747-400 series airplanes, as identified in Boeing Alert Service Bulletin 747-25A3581, Revision 1, dated June 30, 2011.
We are superseding Airworthiness Directive (AD) 2008-08-25 that applied to certain The Boeing Company Model 747-400 and 747-400F series airplanes. AD 2008-08-25 required installing drains and drain tubes to eliminate water accumulation in the drip shield above the M826 cardfile in the main equipment center. This new AD requires installing modified drain tubes, relocating wire bundle routing, installing a new drip shield and drip shield deflectors, and replacing insulation blankets. For certain airplanes, this new AD also concurrently requires sealing the drain slot, installing spuds, and installing drain tubes. This AD was prompted by reports of continued water damage to diode fire card 285U0072-1 in the M826 automatic fire overheat logic test system cardfile following a false FWD CARGO FIRE message, with no change in frequency, which resulted in an air turn back. We are issuing this AD to prevent water from exiting over the edge of the existing drip shield and contaminating electrical components in the M826 cardfile, which could result in an electrical short and potential loss of several functions essential for safe flight.
Within 24 months after the effective date of this AD, install aft and forward drain tubes, relocate wire bundle routing, install a new drip shield and drip shield deflectors, and replace insulation blankets, in accordance with the Accomplishment Instructions of the service information identified in paragraph (g)(1), (g)(2), or (g)(3); as applicable; of this AD.
(1) (For Model 747-400F series airplanes) Boeing Alert Service Bulletin 747-25A3580, Revision 2, dated May 13, 2013.
(2) (For Model 747-400 series airplanes) Boeing Alert Service Bulletin 747-25A3581, Revision 1, dated June 30, 2011.
(3) (For Model 747-400 series airplanes) Boeing Alert Service Bulletin 747-25A3581, Revision 2, dated September 11, 2012 (for Model 747-400 series airplanes).
For Group 1 airplanes as identified in Boeing Alert Service Bulletin 747-25A3581, Revision 1, dated June 30, 2011: Prior to or concurrently with the actions required by paragraph (g) of this AD, seal the drain slot, install spuds, and install left- and right-side drain tubes, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-25A3526, Revision 1, dated February 20, 2009 (for Model 747-400 series airplanes), except as specified in paragraphs (h)(1) and (h)(2) of this AD.
(1) Steps 1 through 5 of Figure 2 of Boeing Alert Service Bulletin 747-25A3526, Revision 1, dated February 20, 2009, are not required if work is being accomplished concurrently with the actions specified in Boeing Alert Service Bulletin 747-25A3581, Revision 1, dated June 30, 2011 (for Model 747-400 series airplanes).
(2) The portion of “More Data” in step 8 of Figure 3 of Boeing Alert Service Bulletin 747-25A3526, Revision 1, dated February 20, 2009, which says “Attach drain tube and strap above bead on the spud,” is not required.
