AD 99-12-08

This amendment supersedes an existing airworthiness directive (AD), applicable to all Boeing Model 737-200C series airplanes, that currently requires a one-time external detailed visual inspection to detect cracks of the fuselage skin in the lower lobe cargo compartment; repetitive internal detailed visual inspections to detect cracks of the frames in the lower lobe cargo compartment; and repair of cracked parts. That AD also provides for an optional preventative modification that constitutes terminating action for the repetitive inspections. This amendment requires accomplishment of the previously optional terminating modification. This amendment is prompted by reports of cracking in the body frames between stringers 19 left and 25 left and at body stations 360 to 500B. The actions specified by this AD are intended to prevent opening or loss of the cargo door during flight, and consequent rapid decompression of the airplane.

Final rule

99-12-08 BOEING: Amendment 39-11192. Docket 98-NM-273-AD. Supersedes AD 93-13-02, Amendment 39-8615. \n\n\tApplicability: All Model 737-200C series airplanes, certificated in any category. \n\tNOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (d)(1) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent opening or loss of the cargo door during flight, and consequent rapid decompression of the airplane, accomplish the following: \n\nRESTATEMENT OF REQUIREMENTS OF AD 93-13-02: \n\n\t(a)\tPrior to the accumulation of 29,000 flight cycles or within 250 flight cycles after August 9, 1993 (the effective date AD 93-13-02, amendment 39-8615), whichever occurs later, accomplish an external detailed visual inspection to detect cracks of the fuselage skin between stringers 19 left and 25 left and at body stations 360 to 540, in accordance with Boeing Alert Service Bulletin 737-53A1160, dated October 24, 1991; or Boeing Service Bulletin 737-53A1160, Revision 1, dated April 29, 1993. If any crack is found, prior to further flight, accomplish the requirements of paragraphs (a)(1) and (a)(2) of this AD. \n\n\t\t(1)\tPerform an internal detailed visual inspection to detect cracks of the frames between stringers 19 left and 25 left and at body stations 360 to 500B, in accordance with either service bulletin. \n\n\t\t(2)\tRepair all cracks in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\t(b)\tWithin 3,000 flight cycles after completing the requirements of paragraph (a) of this AD, unless accomplished within the last 6,000 flight cycles prior to August 9, 1993, perform an internal detailed visual inspection to detect cracks of the frames between stringers 19 left and 25 left and at body stations 360 to 500B, in accordance with Boeing Alert Service Bulletin 737-53A1160, dated October 24, 1991; or Boeing Service Bulletin 737-53A1160, Revision 1, dated April 29, 1993. Thereafter, repeat the internal detailed visual inspection at intervals not to exceed 9,000 flight cycles. If any crack is found, prior to further flight, accomplish the requirements of paragraph (b)(1) or (b)(2) of this AD, as applicable. \n\n\t\t(1)\tIf any crack is found that does not exceed the limits specified in the Boeing 737 Structural Repair Manual (SRM), repair the crack in accordance with the Boeing 737 SRM. Repeat the internal detailed visual inspection thereafter at intervals not to exceed 9,000 flight cycles. \n\n\t\t(2)\tIf any crack is found that exceeds the limits specified in the Boeing 737 SRM, repair the crack in accordance with a method approved by the Manager, Seattle ACO. Repeat the internal detailed visual inspection thereafter at intervals not to exceed 9,000 flight cycles. \n\nNEW REQUIREMENTS OF THIS AD: \n\n\t(c)\tPrior to the accumulation of 75,000 total flight cycles, or within 3,000 flight cycles after the effective date of this AD, whichever occurs later, install doublers on the frames located between stringers 19 left and 25 left and at body stations 360 to 500B, in accordance with Boeing Service Bulletin 737-53A1160, Revision 1, dated April 29, 1993. Accomplishment of this modification constitutes terminating action for the requirements of this AD. \n\nAlternative Methods of Compliance \n\n\t(d)\t(1)\tAn alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. \n\n\t\t(2)\tAlternative methods of compliance approved previously in accordance with AD 93-13-02, amendment 39-8615, are approved as alternative methods of compliance with this AD. \n\n\tNOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. \n\nSpecial Flight Permits \n\n\t(e)\tSpecial flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. \n\nIncorporation by Reference \n\n\t(f)\tExcept as provided by paragraphs (a)(2), (b)(1), and (b)(2) of this AD, the actions shall be done in accordance with Boeing Alert Service Bulletin 737-53A1160, dated October 24, 1991; or Boeing Service Bulletin 737-53A1160, Revision 1, dated April 29, 1993. The incorporation by reference of these documents was approved previously by the Director of the Federal Register as of August 9, 1993 (58 FR 36863, July 9, 1993). Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\n\t(g)\tThis amendment becomes effective on July 16, 1999.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 93-13-02, amendment 39-8615 (58 FR 36863, July 9, 1993), which is applicable to all Boeing Model 737-200C series airplanes, was published in the Federal Register on February 1, 1999 (64 FR 4791). The action proposed to continue to require a one-time external detailed visual inspection to detect cracks of the fuselage skin in the lower lobe cargo compartment; repetitive internal detailed visual inspections to detect cracks of the frames in the lower lobe cargo compartment; and repair of cracked parts. The action also proposed to require accomplishment of the previously optional terminating modification. \nComments \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the single comment received. \n\tThe commenter supports the proposed rule. \n\nConclusion \n\n\tAfter careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed.\n\n Cost Impact \n\n\tThere are approximately 90 airplanes of the affected design in the worldwide fleet. The FAA estimates that 18 airplanes of U.S. registry will be affected by this AD. \n\n\tThe inspections that are currently required by AD 93-13-02, and retained in this AD, take approximately 12 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required inspections on U.S. operators is estimated to be $12,960, or $720 per airplane, per inspection cycle. \n\n\tThe new modification that is required by this new AD will take approximately 160 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $5,500 per airplane. Based on these figures, the cost impact of the modification required by this AD on U.S. operators is estimated to be $271,800, or $15,100 per airplane. \n\n\tThe cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. \n\nRegulatory Impact \n\n\tThe regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. \n\n\tFor the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." \n\nList of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\n\tAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:\n \nPART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 (Amended) \n\n\t2. Section 39.13 is amended by removing amendment 39-8615 (58 FR 36863, July 9, 1993), and by adding a new airworthiness directive (AD), amendment 39-11192, to read as follows: