Airworthiness Directive · Amendment 39-17713 · Equipment/furnishings
The Boeing Company Airplanes
This AD applies to The Boeing Company Model 747-400, -400D, and -400F series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 747-25A3613, dated June 22, 2012.
We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 747-400, -400D, and -400F series airplanes. This AD was prompted by a report of water leakage into the main deck cargo wire integration unit (WIU). The water flowed from the main deck floor panels, through disbonded seams in the aft main equipment center (MEC) drip shield gutter, then onto the WIU. This AD requires cleaning the aft MEC drip shield gutter; and doing a one-time general visual inspection for disbonded seams, and repair if necessary. This AD also requires installing a fiberglass reinforcement overcoat to the underside of the bonded seams of the aft MEC drip shield gutters. We are issuing this AD to prevent water penetration into the MEC, which could result in the loss of flight critical systems.
Within 24 months after the effective date of this AD: Do the actions specified in paragraphs (g)(1) and (g)(2) of this AD, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-25A3613, dated June 22, 2012. Accomplishing paragraphs 3.B.1. and 3.B.4. of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-25A3613, dated June 22, 2012, is optional.
(1) Clean the aft MEC drip shield gutter, and do a general visual inspection for disbonded seams; repair before further flight if any seam disbonding is found.
(2) Install a fiberglass reinforcement overcoat to the underside of the bonded seams of the aft MEC drip shield gutters.
