Airworthiness Directive · Amendment 39-17297 · Fuselage
The Boeing Company Airplanes
This AD applies to The Boeing Company Model 737-300, −400, and −500 series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010.
We are superseding an existing airworthiness directive (AD) for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. That AD currently requires repetitive inspections for cracking of the crown area of the fuselage skin, and corrective actions if necessary. This new AD adds repetitive inspections for cracking using different inspection methods and inspecting additional areas, and corrective actions if necessary. This new AD also requires additional repairs to previously repaired areas and repetitive inspections for loose fasteners and replacement if necessary in certain previously repaired areas. This AD also reduces certain compliance times and extends certain other compliance times. This AD was prompted by additional reports of cracking at the horizontal chem-mill steps away from the lap joints over the entire crown area, and vertical chem-mill cracks adjacent to the butt joints. We are issuing this AD to detect and correct fatigue cracking of the fuselage skin, which could cause the fuselage skin to fracture and fail, and result in rapid decompression of the airplane.
This paragraph restates the requirements of paragraph (g) of AD 2005-13-27, Amendment 39-14164 (70 FR 36821, June 27, 2005). At the later of the times specified in paragraphs (g)(1) and (g)(2) of this AD, perform detailed and eddy current inspections for cracking of the crown area of the fuselage skin in accordance with Part 1, including the “Note,” of the Work Instructions of Boeing Special Attention Service Bulletin 737-53-1234, Revision 1, dated March 31, 2005, except as provided by paragraph (j) of this AD. Doing the inspections required by paragraph (m) of this AD terminates the inspections required by this paragraph for the corresponding inspection areas.
(1) Before the accumulation of the applicable total flight cycles specified in the “Threshold” column of Table 1 of Figure 1 of Boeing Special Attention Service Bulletin 737-53-1234, Revision 1, dated March 31, 2005.
(2) Within 4,500 flight cycles after August 1, 2005 (the effective date of AD 2005-13-27, Amendment 39-14164 (70 FR 36821, June 27, 2005).
This paragraph restates the requirements of paragraph (h) of AD 2005-13-27, Amendment 39-14164 (70 FR 36821, June 27, 2005). Repeat either the detailed or eddy current inspections specified in paragraph (g) of this AD at the applicable intervals specified in paragraph (h)(1) or (h)(2) of this AD until paragraph (i)(1) or (i)(2) of this AD has been done, as applicable. Doing the inspection required by paragraph (m) of this AD terminates the inspections required by this paragraph for the corresponding inspection area.
(1) Repeat the detailed inspections thereafter at intervals not to exceed 1,200 flight cycles.
(2) Repeat the eddy current inspections thereafter at intervals not to exceed 3,000 flight cycles.
This paragraph restates the requirements of paragraph (i) of AD 2005-13-27, Amendment 39-14164 (70 FR 36821, June 27, 2005). If any cracking is found during any inspection required by paragraph (g) or (h) of this AD, do the actions specified in paragraph (i)(1) or (i)(2) of this AD, in accordance with Boeing Special Attention Service Bulletin 737-53-1234, Revision 1, dated March 31, 2005, except as provided by paragraphs (j) and (k) of this AD.
(1) Before further flight, do a permanent repair (including related investigative actions and applicable corrective actions) in accordance with Part 2 of the Work Instructions of Boeing Special Attention Service Bulletin 737-53-1234, Revision 1, dated March 31, 2005. Doing a permanent repair ends the repetitive inspections required by paragraph (h) of this AD for the repaired area only.
(2) Do the actions specified in paragraphs (i)(2)(i) and (i)(2)(ii) of this AD at the time specified in the applicable paragraph. Doing a time-limited repair ends the repetitive inspections required by paragraph (h) of this AD for the repaired area only.
(i) Before further flight, do a time-limited repair (including related investigative actions and applicable corrective actions) in accordance with Part 3 of the Work Instructions of Boeing Special Attention Service Bulletin 737-53-1234, Revision 1, dated March 31, 2005.
(ii) At the times specified in Figure 8 of Boeing Special Attention Service Bulletin 737-53-1234, Revision 1, dated March 31, 2005, do the related investigative and corrective actions in accordance with Part 3 of the Work Instructions of Boeing Special Attention Service Bulletin 737-53-1234, Revision 1, dated March 31, 2005.
This paragraph restates the requirements of paragraph (j) of AD 2005-13-27, Amendment 39-14164 (70 FR 36821, June 27, 2005). Where Boeing Special Attention Service Bulletin 737-53-1234, Revision 1, dated March 31, 2005, specifies to contact Boeing for appropriate action: Before further flight, repair according to a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or according to data meeting the certification basis of the airplane approved by an Authorized Representative for the Boeing Delegation Option Authorization Organization who has been authorized by the Manager, Seattle ACO, to make those findings; or using a method approved in accordance with the procedures specified in paragraph (x) of this AD. For a repair method to be approved, the approval must specifically reference this AD.
This paragraph restates the provisions of paragraph (k) of AD 2005-13-27, Amendment 39-14164 (70 FR 36821, June 27, 2005). Although Boeing Special Attention Service Bulletin 737-53-1234, Revision 1, dated March 31, 2005, specifies reporting certain information to Boeing, this AD does not require that action.
This paragraph restates the requirements of paragraph (l) of AD 2005-13-27, Amendment 39-14164 (70 FR 36821, June 27, 2005). Actions done before August 1, 2005, in accordance with Boeing Special Attention Service Bulletin 737-53-1234, dated June 13, 2002 (which is not incorporated by reference in this AD), are acceptable for compliance with the corresponding actions required by paragraphs (g), (h), and (i) of this AD.
Except as provided by paragraph (v)(1) of this AD, at the applicable time specified in Tables 1 and 2 of paragraph 1.E, “Compliance,” of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010: Do a non-destructive inspection (NDI) (medium frequency eddy current, magneto optical imaging, C-scan, or ultrasonic phased array) for horizontal chem-mill cracking above the S-4 and S-10 lap joints, in accordance with paragraph 3.B.1.a. of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, except as provided by paragraph (r) of this AD. Repeat the applicable inspections thereafter at intervals not to exceed those specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010. Accomplishment of the inspections required by this paragraph terminates the requirements of paragraphs (g) and (h) of this AD for the corresponding inspection areas.
Note 1 to paragraph (m) of this AD: Option 1 of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, specifies doing one of the following NDI: Medium frequency eddy current inspection, magneto optical imaging inspection, or C-scan inspection. Option 2 specifies doing one NDI—an external ultrasonic phased array inspection. These options have different compliance times after the initial inspection.
If any cracking is found during any inspection required by paragraph (m) of this AD, do the actions specified in paragraph (n)(1) or (n)(2) of this AD.
(1) Before further flight, do a permanent repair, including related investigative actions and applicable corrective actions, in accordance with Part 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, except as provided by paragraph (v)(2) of this AD. Doing a permanent repair ends the repetitive inspections required by paragraph (m) of this AD for the repaired area only.
(2) Do the actions specified in paragraphs (n)(2)(i), (n)(2)(ii), and (n)(2)(iii) of this AD at the time specified in the applicable paragraph. Doing a time-limited repair ends the repetitive inspections required by paragraph (m) of this AD for the repaired area only.
(i) Before further flight, do a time-limited repair, including related investigative actions and applicable corrective actions, in accordance with Part 4 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, except as provided by paragraph (v)(2) of this AD.
(ii) Within 3,000 flight cycles after the time-limited repair was installed as specified in paragraph (n)(2)(i) of this AD, or within 500 flight cycles after the effective date of this AD, whichever occurs later, do a detailed inspection for loose fasteners, in accordance with Part 4 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010. Repeat the inspection thereafter at intervals not to exceed 3,000 flight cycles until the permanent repair required by paragraph (n)(2)(iii) of this AD is done. If any loose fasteners are found, before further flight, replace the fasteners with new fasteners of the same type and size, as specified in Figures 6, 35, and 36 of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010.
(iii) Within 6,000 flight cycles after the time-limited repair was installed, as specified in paragraph (n)(2)(i) of this AD, do the permanent repair, in accordance with Part 4 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, except as provided by paragraph (v)(2) of this AD.
Except as provided by paragraph (v)(1) of this AD, at the applicable time specified in Table 3 of paragraph 1.E, “Compliance,” of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010: Do an NDI (medium frequency eddy current, magneto optical imaging, C-scan, or ultrasonic phased array) for horizontal chem-mill cracking in the shear wrinkle areas, in accordance with paragraph 3.B.1.b of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010. Repeat the applicable inspections thereafter at intervals not to exceed those specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010.
Except as provided by paragraph (v)(1) of this AD, at the applicable time specified in Table 4 of paragraph 1.E, “Compliance,” of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010: Do an NDI (medium frequency eddy current, magneto optical imaging, C-scan, or ultrasonic phased array) for vertical chem-mill cracking at locations specified in, and in accordance with paragraph 3.B.1.c. of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010. Repeat the applicable inspections thereafter at intervals not to exceed those specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010.
Except as provided by paragraph (v)(1) of this AD, at the applicable time specified in Tables 5 and 6 of paragraph 1.E, “Compliance,” of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010: Do an NDI (medium frequency eddy current, magneto optical imaging, C-scan, or ultrasonic phased array) for horizontal chem-mill cracking in general pocket-to-pocket areas at specified locations in and in accordance with paragraphs 3.B.1.d., 3.B.1.e., and 3.B.1.f., as applicable, of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010. Repeat the applicable inspections thereafter at intervals not to exceed those specified in Tables 5 and 6 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010.
For inspections required by paragraph (m) of this AD: It is not necessary to inspect the chem-mill steps under an existing repair installed using Boeing Special Attention Service Bulletin 737-53-1234, dated June 13, 2002 (which is not incorporated by reference in this AD); or Revision 1, dated March 31, 2005.
If any crack is found during any inspection required by paragraph (o), (p), or (q) of this AD, before further flight, repair the crack using a method approved in accordance with the procedures specified in paragraph (x) of this AD. Doing this repair ends the repetitive inspections required by paragraphs (o), (p), and (q) of this AD for the repaired area only.
(1) For airplanes on which permanent repairs have been done as specified in Boeing Special Attention Service Bulletin 737-53-1234, dated June 13, 2002 (which is not incorporated by reference in this AD); or Revision 1, dated March 31, 2005; except airplanes on which internal tear strap doublers were previously installed using a repair plan approved using the procedures specified in paragraph (x) of this AD: Within 6,000 flight cycles after the effective date of this AD, install internal tear strap doublers, in accordance with paragraph 3.B.3. of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, except as provided by paragraph (v)(2) of this AD.
(2) For airplanes on which time-limited repairs have been installed as specified in Boeing Special Attention Service Bulletin 737-53-1234, dated June 13, 2002 (which is not incorporated by reference in this AD); or Revision 1, dated March 31, 2005; except airplanes on which the permanent repair has been installed before the effective date of this AD as specified in Boeing Special Attention Service Bulletin 737-53-1234, dated June 13, 2002 (which is not incorporated by reference in this AD); or Revision 1, dated March 31, 2005: Within 3,000 flight cycles after the time limited repair is installed, or within 500 flight cycles after the effective date of the AD, whichever occurs later, do a detailed inspection for loose fasteners, in accordance with paragraph 3.B.4. of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010. Repeat the inspection thereafter at intervals not to exceed 3,000 flight cycles until the permanent repair is installed in accordance with paragraph (t)(3) of this AD. If any loose fasteners are found, before further flight, replace the fasteners with new fasteners of the same type and size, as specified in Figures 6, 35, and 36, as applicable, of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010.
(3) For airplanes on which time-limited repairs have been installed as specified in Boeing Special Attention Service Bulletin 737-53-1234, dated June 13, 2002 (which is not incorporated by reference in this AD); or Revision 1, dated March 31, 2005; except airplanes on which the permanent repair has been installed before the effective date of this AD as specified in Boeing Special Attention Service Bulletin 737-53-1234, dated June 13, 2002, or Revision 1, dated March 31, 2005; before the effective date of this AD: Within 6,000 flight cycles after the time-limited repair is installed, or within 1,000 flight cycles after the effective date of this AD, whichever occurs later, make the repair permanent by replacing the blind fasteners in the time-limited repair with solid rivets, and install internal tear strap doublers, in accordance with paragraph 3.B.4. of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, except as provided by paragraph (v)(2) of this AD.
If any crack is found after the time-limited or permanent repair is installed, and Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, 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 (x) of this AD.
(1) Where paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, specifies a compliance time relative to the “release of Revision 2 of this service bulletin,” this AD requires compliance within the specified compliance time after the effective date of this AD.
(2) Where Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, specifies to contact Boeing for appropriate action: Before further flight, repair the cracking using a method approved in accordance with the procedures specified in paragraph (x) of this AD.
(3) Although Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, specifies reporting certain information to Boeing, this AD does not require that action.
The post-repair inspection specified in Table 7 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, is not required by this AD.
Note 2 to paragraph (w) of this AD: The damage tolerance inspections specified in Table 7 of paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, may be used in support of compliance with section 121.1109(c)(2) or 129.109(c)(2) of the Federal Aviation Regulations (14 CFR 121.1109(c)(2) or 14 CFR 129.109(c)(2)). The corresponding actions specified in the Accomplishment Instructions and Figures 40 and 41 of Boeing Alert Service Bulletin 737-53A1234, Revision 2, dated November 24, 2010, are not required in this AD.
