Airworthiness Directive · Amendment 39-17428 · Fuselage
The Boeing Company Airplanes
(1) This AD applies to The Boeing Company Model 737-900 and -900ER series airplanes, certificated in any category, as identified in Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012.
(2) Installation of Supplemental Type Certificate (STC) ST00830SE (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgstc.nsf/0/408E012E008616A7862578880060456C?OpenDocument&Highlight=st00830se) does not affect the ability to accomplish the actions required by this AD. Therefore, for airplanes on which STC ST00830SE is installed, a “change in product” alternative method of compliance (AMOC) approval request is not necessary to comply with the requirements of 14 CFR 39.17.
We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-900 and -900ER series airplanes. This AD was prompted by reports of early fatigue cracks at chem-mill areas on the crown skin panels. This AD requires repetitive inspections for cracking of the fuselage skin along chem-mill steps at certain crown skin and shear wrinkle areas, and repair if necessary. We are issuing this AD to detect and correct fatigue cracking of the skin panel at the specified chem-mill step locations, which could result in rapid decompression of the airplane.
At the applicable time specified in paragraph 1.E., “Compliance,” of Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012, except as required by paragraph (k) of this AD: Do an external detailed inspection and an external nondestructive inspection (a medium frequency eddy current (MFEC), magneto optic imager (MOI), C-scan, or ultrasonic phased array (UTPA) inspection) for cracking in the fuselage skin along the chem-mill steps at certain locations specified in, and in accordance with, the Accomplishment Instructions of Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012. Repeat the inspections thereafter at the applicable times specified in paragraph 1.E., “Compliance,” of Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012.
For Group 1 airplanes as identified in Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012: At the applicable time specified in paragraph 1.E., “Compliance,” of Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012, except as required by paragraph (k) of this AD, do an external detailed inspection and an external nondestructive inspection (MFEC, MOI, C-scan, or UTPA) for cracking in the fuselage skin along the chem-mill steps at certain shear wrinkle locations specified in, and in accordance with, the Accomplishment Instructions of Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012. Repeat the inspections thereafter at the applicable times specified in paragraph 1.E., “Compliance,” of Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012.
If any cracking is found during any inspection required by either paragraph (g) or (h) of this AD, before further flight, repair the cracking using a method approved in accordance with the procedures specified in paragraph (m) of this AD. Accomplishing the repair approved in accordance with the procedures specified in paragraph (m) of this AD terminates the repetitive inspection requirement for that area under the repair only.
Modification of an inspection area specified in paragraph (g) of this AD, including doing an external detailed inspection and an external nondestructive inspection (MFEC, MOI, C-scan, or UTPA) for cracking of the area to be modified, and a high frequency eddy current inspection of all existing holes for cracking as applicable, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012, terminates the repetitive inspections required by paragraph (g) of this AD for that modified area only. If any cracking is found during any inspection described by this paragraph, before further flight, repair the cracking using a method approved in accordance with the procedures specified in paragraph (m) of this AD.
Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012, specifies compliance times “after the original issue date of this service bulletin.” However, this AD requires compliance within the specified compliance times “after the effective date of this AD.”
The post-modification inspections specified in Tables 3 and 4 of paragraph 1.E., “Compliance,” of Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012, are not required by this AD.
Note 1 to paragraph (l) of this AD: The damage tolerance inspections specified in Tables 3 and 4 of paragraph 1.E., “Compliance,” of Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012, may be used in support of compliance with section 121.1109(c)(2) or 129.109(b)(2) of the Federal Aviation Regulations (14 CFR 121.1109(c)(2) or 14 CFR 129.109(b)(2)). The actions specified in Part 5 of the Accomplishment Instructions and corresponding figures of Boeing Service Bulletin 737-53-1312, dated October 21, 2011, as revised by Boeing Service Bulletin 737-53-1312, Revision 1, dated March 14, 2012, are not required by this AD.
