AD 2006-26-09 Airworthiness Directives; Boeing Model 737-200, -300, -400, and -500 Series Airplanes

Models named: 737-200, -300, -400, -500 series. Read the applicability below — it usually turns on serial or part numbers too.

This AD applies to Boeing Model 737-200, -300, -400, and -500 series airplanes; certificated in any category; as identified in Boeing Special Attention Service Bulletin 737-53-1216, Revision 1, dated June 8, 2006.

You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done. Inspection to Determine Subject Support Brackets (f) Perform a one-time general visual inspection of the frames between station 360 and station 907 to identify the support brackets for the air conditioning outlet extrusion attached with a two-rivet configuration, in accordance with Part I of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1216, Revision 1, dated June 8, 2006. Do this inspection at the applicable time specified in paragraph 1.E., “Compliance,” of the service bulletin, except, where the service bulletin specifies a compliance time after the issuance of the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD. Repetitive Inspections for Cracking (g) For each frame with a subject support bracket identified during the inspection in accordance with paragraph (f) of this AD: Perform a medium-frequency eddy current inspection for cracking of the frame around the attachment rivets of the support bracket, and a high-frequency eddy current inspection for cracking of the frame adjacent to the inboard fastener hole, by doing all the actions specified in and in accordance with Part I of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1216, Revision 1, dated June 8, 2006, except for paragraph 3.B.2. of Part I (which was already done in accordance with paragraph (f) of this AD). Do the initial inspections at the applicable time specified in paragraph 1.E., “Compliance,” of the service bulletin, except, where the service bulletin specifies a compliance time after the issuance of the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD. If no cracking is found, repeat the inspections thereafter at intervals not to exceed the repeat interval specified in paragraph 1.E., “Compliance,” of the service bulletin, until paragraph (h) or (i) of this AD is done. Repair (h) For any frame in which cracking is found during any inspection required by paragraph (g) of this AD: Before further flight, repair the cracking by doing all applicable actions in accordance with Part III of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1216, Revision 1, dated June 8, 2006. Then, do paragraph (k) of this AD, at the time specified in that paragraph. Doing this repair ends the repetitive inspections required by paragraph (g) of this AD for each modified frame. Optional Preventive Modification (i) For any frame on which a support bracket for the air conditioning outlet extrusion attached with a two-rivet configuration is installed: Doing all actions associated with the preventive modification in accordance with Part II of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1216, Revision 1, dated June 8, 2006, ends the repetitive inspections required by paragraph (g) of this AD for each modified frame. Do the requirements of paragraph (k) of this AD on each modified frame at the time specified in that paragraph. Actions Accomplished According to Related Service Information (j) Actions accomplished before the effective date of this AD according to Boeing Communication M-7200-02-01292, dated August 20, 2002; are considered acceptable for compliance with the corresponding actions specified in paragraphs (f), (g), (h), and (i) of this AD, as applicable. Post-Modification/Repair Inspections (k) For each frame repaired or modified in accordance with paragraph (h), (i), or (j) of this AD, as applicable: Within 24,000 flight cycles after doing the modification/repair, but after a minimum of 18,000 flight cycles after doing the modification/repair, do one-time detailed inspections for cracking of the repaired/modified frame, air conditioning attach brackets, and stringer clips, by doing all actions in accordance with Part IV of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-53-1216, Revision 1, dated June 8, 2006. If any cracking is found during the post-modification/repair inspections, before further flight, repair the cracking using a method approved in accordance with paragraph (m) of this AD. Actions Accomplished Previously (l) Inspections/modifications/repairs done before the effective date of this AD in accordance with Boeing Special Attention Service Bulletin 737-53-1216, dated January 27, 2005, are acceptable for compliance with the corresponding actions required by this AD. Alternative Methods of Compliance (AMOCs) (m)(1) The Manager, Seattle Aircraft Certification Office (ACO), has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19. (2) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD, if it is approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization who has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the repair must meet the certification basis of the airplane, and the approval must specifically refer to this AD. (3) Before using any AMOC approved in accordance with 14 CFR 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office. Material Incorporated by Reference (n) You must use Boeing Special Attention Service Bulletin 737-53-1216, Revision 1, dated June 8, 2006, to perform the actions that are required by this AD, unless the AD specifies otherwise. The Director of the Federal Register approved the incorporation by reference of this document in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207, for a copy of this service information. You may review copies at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., Room PL-401, Nassif Building, Washington, DC; on the Internet at http://dms.dot.gov ; or at the National Archives and Records Administration (NARA). For information on the availability of this material at the NARA, call (202) 741-6030, or go to http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. Issued in Renton, Washington, on December 21, 2006. Ali Bahrami, Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. E6-22462 Filed 1-3-07; 8:45 am] BILLING CODE 4910-13-P

This AD results from numerous reports indicating that frame cracks have been found at the attachment holes for support brackets for the air conditioning outlet extrusion. We are issuing this AD to detect and correct such cracking, which, if the cracking were to continue to grow, could result in a severed frame. A severed frame, combined with existing multi-site damage at the stringer 10 lap splice, could result in rapid decompression of the airplane.