Airworthiness Directive · Amendment 39-19056 · Fuselage
The Boeing Company Airplanes
(1) This AD applies to The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015.
(2) Installation of Supplemental Type Certificate (STC) ST00830SE [ http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgstc.nsf/0/184DE9A71EC3FA5586257EAE00707DA6?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 superseding Airworthiness Directive (AD) 2008-12-04, which applied to certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes. AD 2008-12-04 required various repetitive inspections to detect cracks along the chem-milled steps of the fuselage skin, and to detect missing or loose fasteners in the area of a certain preventive modification or repairs; replacement of the time-limited repair with a permanent repair, if applicable; and applicable corrective actions which would end certain repetitive inspections. This AD reduces the post-modification inspection compliance times, limits installation of the preventive modification to airplanes with fewer than 30,000 total flight cycles, and adds repetitive inspections for modified airplanes. This AD was prompted by an evaluation by the design approval holder (DAH) that indicated that the upper skin panel at the chem-milled step above the lap joint is subject to widespread fatigue damage (WFD) if the modification was installed after 30,000 total flight cycles. We are issuing this AD to address the unsafe condition on these products.
At locations where a preventive modification, time-limited repair, or permanent repair has not been installed as specified in Boeing Service Bulletin 737-53A1232: At the applicable time specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, do an external detailed inspection and an inspection specified in either paragraph (g)(1) or (g)(2) of this AD, for any crack in the fuselage skin at the chem-milled steps at specified locations, in accordance with Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015. Do all applicable related investigative and corrective actions before further flight in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, except as required by paragraph (l)(1) of this AD, and except as provided in paragraphs (l)(3) and (l)(4) of this AD. Repeat the inspections thereafter at the applicable time specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015.
(1) Do an external medium frequency eddy current (MFEC), or magneto optic imager (MOI), or C-Scan inspection.
(2) Do an external ultrasonic phased array (UTPA) inspection.
At any location with a preventive modification installed as specified in Boeing Service Bulletin 737-53A1232: At the applicable time specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, except as required by paragraph (l)(2) of this AD, do the actions specified in paragraphs (h)(1) and (h)(2) of this AD.
(1) Do external detailed and external high frequency and medium frequency eddy current inspections for any crack, in accordance with Part 7 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015. If no crack is found during the inspection, repeat the inspections thereafter at the applicable time specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015. If any crack is found during any inspection required by this paragraph, repair before further flight, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, except as required by paragraph (l)(1) of this AD.
(2) Do a detailed inspection for any crack and any loose or missing fasteners, in accordance with Part 7 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015. Repeat the inspections thereafter at applicable time specified in paragraph 1.E, “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015. If any crack is found during any inspection, or any loose or missing fastener is found, before further flight, do all applicable corrective actions, in accordance with Part V of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, except as specified in paragraph (l)(1) of this AD.
(1) At any location where a preventive modification as specified in Boeing Service Bulletin 737-53A1232 was installed after the accumulation of 30,000 total flight cycles, at the applicable time specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, except as required by paragraph (l)(2) of this AD, do all applicable investigative and corrective actions using a method approved in accordance with the procedures specified in paragraph (p) of this AD. For preventive modifications installed on airplanes listed in Appendix A of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, at the specified total flight cycles: The actions specified in this paragraph are not required.
(2) For airplanes which have installed STC ST01697SE (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgstc.nsf/0/0812969a86af879b8625766400600105/$FILE/ST01697SE.pdf) and the preventive modification has been installed after 15,000 total flight cycles: Before the accumulation of 25,000 total flight cycles, do all applicable investigative and corrective actions using a method approved in accordance with the procedures specified in paragraph (p) of this AD.
At any location where a permanent repair has been installed as specified in Boeing Service Bulletin 737-53A1232: At the applicable time specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, do the inspections specified in paragraph (j)(1) or (j)(2) of this AD, in accordance with Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015. Repeat the inspections thereafter at the applicable time specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015. Do all applicable related investigative and corrective actions before further flight in accordance with Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, except as required by paragraph (l)(1) of this AD.
(1) Do an external low frequency eddy current (LFEC) inspection for any crack, and doubler external LFEC and external detailed inspections for any crack and loose or missing fasteners.
(2) Do an external LFEC inspection for any crack, a doubler external LFEC and external detailed inspections for any crack and loose or missing fasteners, and an internal MFEC for any crack.
At any location where a chem-milled time-limited repair is installed, do the actions specified in paragraphs (k)(1) and (k)(2) of this AD, at the applicable time specified in 1.E. “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015.
(1) Do internal and external detailed inspections of the time-limited repair for any crack, or loose or missing fasteners, in accordance with Part IV of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015. Repeat the inspections thereafter at the applicable time specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015. If any crack is found during any inspection, or if any loose or missing fastener is found, before further flight, do all applicable corrective actions, in accordance with Part IV of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, except as specified in paragraph (l)(1) of this AD.
(2) Replace the time-limited repair with the permanent repair, in accordance with Part IV of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015.
(1) Where Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, specifies to contact Boeing for repair instructions, this AD requires repair before further flight using a method approved in accordance with the procedures specified in paragraph (p) of this AD.
(2) Where paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, specifies a compliance time “after the date of Revision 2 of this service bulletin,” this AD requires compliance within the specified compliance time after the effective date of this AD.
(3) For airplanes on which the actions specified in paragraph (g) of this AD are required: Inspections specified in table 1 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, are not required in areas that are spanned by an FAA-approved repair that has a minimum of 3 rows of fasteners above and below the chem-milled step, provided that the repair was installed before the effective date of this AD. Operators must accomplish post-repair inspections at the applicable time specified in table 2 of paragraph 1.E, “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015.
(4) For any airplane that has an external doubler covering the chem-milled step, but the doubler does not span the step by a minimum of 3 rows of fasteners above and below the chem-milled step and the doubler was installed before the effective date of this AD: One method of compliance with the inspection requirement of paragraph (g) of this AD is to inspect all chem-milled steps covered by the repair using non-destructive test (NDT) methods approved in accordance with the procedures specified in paragraph (p) of this AD. These repairs are to be considered time-limited and are subject to the post-repair supplemental inspections and replacement at the times specified in table 3 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015.
Note 1 to paragraph (l)(4) of this AD: Guidance for the procedures for the alternative inspection specified in paragraph (l)(4) of this AD can be found in the Boeing 737 NDT Manual, Part 6, Subject 53-30-20.
(1) For airplanes that have accumulated 30,000 total flight cycles or fewer, or for airplanes on which STC ST01697SE was installed and that have accumulated 15,000 total flight cycles or fewer, accomplishment of the preventive modification specified in Part V of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, terminates the inspections required by paragraph (g) of this AD in the modified areas only.
(2) Installation of a permanent repair as specified in Part III of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, or a time-limited repair as specified in Part IV of Boeing Alert Service Bulletin 737-53A1232, Revision 3, dated July 27, 2015, terminates the inspections required by paragraph (g) of this AD in the repaired areas only.
As of the effective date of this AD, installation of the preventive modification specified in Boeing Service Bulletin 737-53A1232 is prohibited on the airplanes identified in paragraphs (n)(1) and (n)(2) of this AD.
(1) Airplanes that have accumulated more than 30,000 total flight cycles.
(2) Airplanes which have installed STC ST01697SE and that have accumulated more than 15,000 total flight cycles.
