Airworthiness Directive · Amendment 39-15050 · Boeing Model 747-400 Series Airplanes
Boeing Model 747-400 Series Airplanes
This AD applies to Boeing Model 747-400 series airplanes, certificated in any category; as identified in Boeing Alert Service Bulletin 747-53A2660, dated November 16, 2006.
The FAA is adopting a new airworthiness directive (AD) for certain Boeing Model 747-400 series airplanes. This AD requires repetitive inspections for any crack in the upper deck floor beam at station 400, which include inspecting the floor beam web and chords, certain fastener holes at the intersection of the floor beam and frame on both sides of the airplane, and certain floor panel attachment fastener holes at the floor beam upper chords. This AD also requires corrective action if necessary. This AD results from several reports indicating that fatigue cracking was found in upper deck floor beams made from 7000 series aluminum alloy. We are issuing this AD to detect and correct cracking in the upper deck floor beam at station 400, which could extend and sever the floor beam. A severed floor beam could result in loss of controllability and rapid decompression of the airplane.
You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.
At the applicable times specified in Table 1 of paragraph 1.E. of Boeing Alert Service Bulletin 747-53A2660, dated November 16, 2006, do the actions specified in paragraphs (f)(1), (f)(2), and (f)(3) of this AD and do all applicable corrective actions, by accomplishing all the applicable actions specified in the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2660, dated November 16, 2006; except where the service bulletin specifies to contact Boeing for appropriate action: Before further flight, repair the crack using a method approved in accordance with paragraph (g) of this AD. Do all applicable corrective actions before further flight.
(1) Repetitive detailed inspections for any crack in the upper deck floor beam at the intersection of the floor beam and frame on both sides of the airplane.
(2) Repetitive open hole high frequency eddy current (HFEC) inspections for any crack in certain fastener holes at the intersection of the floor beam upper chord and the frame inner chord on both sides of the airplane.
(3) Repetitive open hole HFEC inspections for any crack in the upper deck floor beam at all floor panel attachment fastener holes through the forward and aft horizontal flanges of the floor beam upper chord, from the left body frame to the right body frame.
