Airworthiness Directive · Amendment 39-17238 · Fuselage
The Boeing Company Airplanes
Superseded. A later AD replaced this one: AD 2016-25-09. Comply with the one in force.
This AD applies to The Boeing Company Model 747-400, -400D, and -400F series airplanes, certificated in any category, as specified in Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011.
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 reports of crown frame web cracking at left buttock line (LBL) 15.0, station (STA) 320. This AD requires measuring the web at STA 320 and, depending on findings, various inspections for cracks and missing fasteners, web and fastener replacement, and related investigative and corrective actions if necessary. We are issuing this AD to prevent complete fracture of the crown frame assembly, and consequent damage to the skin and in-flight decompression of the airplane.
At the applicable compliance time specified in paragraph 1.E., “Compliance,” of Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011, except as specified in paragraph (k)(1) of this AD, measure the thickness of the crown frame web at STA 320, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011. For airplanes with a 0.136- to 0.145-inch-thick web, no further action is required by this AD.
For airplanes on which the web measures 0.078- to 0.083-inch-thick during the measurement required by paragraph (g) of this AD, and on which a repair doubler is not installed: At the applicable time specified in paragraph 1.E., “Compliance,” of Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011, except as specified in paragraph (k)(1) of this AD, do a detailed inspection for cracks and a general visual inspection for missing fasteners of the crown frame web at STA 320; and do all applicable related investigative and corrective actions; in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011, except as specified in paragraph (k)(2) of this AD. Do the applicable related investigative and corrective actions at the applicable times specified in paragraph 1.E., “Compliance,” of Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011, except as specified in paragraph (k)(1) of this AD. Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011, provides options for accomplishing the actions that are required for airplanes on which no cracking is found in the crown frame web.
For airplanes on which the web measures 0.078- to 0.083-inch-thick during the measurement required by paragraph (g) of this AD, and on which a repair doubler is installed: At the applicable compliance time specified in paragraph 1.E., “Compliance,” of Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011, except as specified in paragraph (k)(1) of this AD, do the actions specified in paragraphs (i)(1) and (i)(2) of this AD, and do all applicable corrective actions, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011, except as specified in paragraph (k)(2) of this AD. Do all applicable corrective actions before further flight.
(1) Replace the web with a new web and do all applicable related investigative actions.
(2) Do a detailed inspection for cracks in the upper or lower chord of the crown frame web at STA 320.
Following any web replacement required by this AD, at the times specified in paragraph 1.E., “Compliance,” of Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011: Do a detailed inspection for cracks of the web, upper chord, lower chord, and lower chord splice, and do all applicable corrective actions, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011, except as specified in paragraph (k)(2) of this AD. Do all applicable corrective actions before further flight. If no crack is found, repeat the inspection thereafter at the intervals specified in paragraph 1.E., “Compliance,” of Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011. Accomplishment of the inspections required by AD 2009-19-05, Amendment 39-16022 (74 FR 48138, September 22, 2009), terminates the requirements of this paragraph.
(1) Where Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011, specifies a compliance time “after the original issue date of the service bulletin,” this AD requires compliance within the specified compliance time after the effective date of this AD.
(2) Where Boeing Service Bulletin 747-53A2784, Revision 1, dated September 14, 2011, specifies to contact Boeing for appropriate action, accomplish applicable actions before further flight using a method approved in accordance with the procedures specified in paragraph (m) of this AD.
