Airworthiness Directive · Amendment 39-15894 · Boeing Model 747 Airplanes
Boeing Model 747 Airplanes
This AD applies to Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SR, and 747SP series airplanes, certificated in any category; as identified in Boeing Alert Service Bulletin 747-53A2651, dated June 12, 2008.
We are adopting a new airworthiness directive (AD) for certain Boeing Model 747 airplanes. This AD requires repetitive external surface high frequency eddy current inspections to detect cracks in the radius detail of the upper lobe doubler on both sides of the airplane, and applicable corrective action. This AD results from reports of cracks in the radius detail of the upper lobe doublers. We are issuing this AD to detect and correct cracks in the upper lobe doublers. Such cracks could result in significant degradation of the fuselage structure and reduce its ability to carry flight loads from the vertical stabilizer, which could adversely affect the controllability of the airplane.
Comply with this AD within the compliance times specified, unless already done.
At the applicable times specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 747-53A2651, dated June 12, 2008, except as required by paragraph (i) of this AD, do an external surface high frequency eddy current inspection to detect cracks in the radius detail of the upper lobe doubler on both sides of the airplane, and the applicable corrective action, by accomplishing all the applicable actions specified in the Accomplishment Instructions of the service bulletin, except as required by paragraphs (g) and (h) of this AD. The applicable corrective action must be done before further flight. As applicable, repeat the inspection thereafter at the applicable times specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 747-53A2651, dated June 12, 2008.
(g) Where Boeing Alert Service Bulletin 747-53A2651, dated June 12, 2008, paragraph 3.B., Work Instructions, PART 3, Step 1, specifies a sealant application “from STA 2520 to STA 2521,” this AD requires a sealant application “from STA 2491 to STA 2521” on both sides of the airplane.
(h) Where Boeing Alert Service Bulletin 747-53A2651, dated June 12, 2008, specifies to contact Boeing for repair instructions instead of repairing or replacing any cracked upper lobe doubler in accordance with the service bulletin, this AD requires, before further flight, repairing any cracked upper lobe doubler using a method approved in accordance with the procedures specified in paragraph (j) of this AD.
(i) Where Boeing Alert Service Bulletin 747-53A2651, dated June 12, 2008, specifies a compliance time after the date on the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD.
