Airworthiness Directive · Amendment 39-17695 · Nacelles/pylons
The Boeing Company Airplanes
This AD applies to The Boeing Company Model 747-200B, 747-200C, 747-200F, 747-300, and 747SR series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 747-54A2237, dated March 14, 2013.
We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 747-200B, -200C, -200F, -300, and 747SR series airplanes. This AD was prompted by reports of cracks of both lower chords and web on certain outboard struts. This AD requires repetitive inspections for cracking of the lower spar chords and web, web lower spar chord modification, which includes inspections for cracking of the lower spar chords, and repetitive post modification inspections for cracking of the lower spar web and chord; and applicable corrective actions. We are issuing this AD to prevent cracked chords and web on certain outboard struts, which, if the chord severs, could result in reduced structural integrity of the diagonal brace load path and of the strut-to-wing attachment, and consequent separation of a strut and engine from the airplane during flight.
Except as required by paragraph (j)(1) of this AD, at the compliance time specified in table 1 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 747-54A2237, dated March 14, 2013: Do a detailed inspection for cracking of the lower spar chords and web, a high frequency eddy current (HFEC) inspection for cracking of the lower spar chords, and all applicable repairs and modifications, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2237, dated March 14, 2013, except as required by paragraph (j)(2) of this AD. If no cracking is found, repeat the inspections thereafter at intervals not to exceed 600 flight cycles, until the actions specified in paragraph (h) of this AD have been accomplished. Do all applicable corrective actions before further flight. Accomplishing a repair and modification, including open-hole HFEC inspections for cracking and applicable corrective actions required by this paragraph terminates the actions required by paragraphs (g) and (h) of this AD for the repaired and modified strut only. The open-hole HFEC inspection for cracking must be done before the modification.
Except as required by paragraph (j)(1) of this AD, at the compliance time specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 747-54A2237, dated March 14, 2013: Do a detailed inspection for cracking of the lower spar chords and web, an HFEC inspection for cracking of the lower spar chords, a lower spar chord modification, including open-hole HFEC inspections for cracking in the chord and all applicable corrective actions, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2237, dated March 14, 2013, except as required by paragraph (j)(2) of this AD. Do all applicable corrective actions before further flight. Doing the actions specified in this paragraph terminates the requirements of paragraph (g) of this AD for the modified strut only. The open-hole HFEC inspection for cracking must be done before the modification.
For airplanes on which a modification required by paragraph (g) or (h) of this AD has been done: At the compliance time specified in table 2 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 747-54A2237, dated March 14, 2013, do a detailed inspection for any cracking of the lower spar web and chord, and do all applicable corrective actions, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2237, dated March 14, 2013, except as required by paragraph (j)(2) of this AD. Repeat the inspection thereafter at intervals not to exceed 18 months. Do all applicable corrective actions before further flight.
(1) Where Boeing Alert Service Bulletin 747-54A2237, dated March 14, 2013, specifies a compliance time after the original issue date on the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD.
(2) Where Boeing Alert Service Bulletin 747-54A2237, dated March 14, 2013, specifies to contact Boeing for appropriate action: Before further flight, repair the crack using a method approved in accordance with the procedures specified in paragraph (k) of this AD.
