AD 2001-16-06

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737 series airplanes, that requires initial and repetitive inspections of certain areas of the wing spars to detect cracking or corrosion; and follow-on corrective actions and repair, if necessary. This amendment is prompted by reports of cracks and corrosion in the upper chord of the front and rear spars of the wing and reports of cracks propagating from previously repaired areas. The actions specified by this AD are intended to detect and correct such cracking or corrosion of the upper and lower chords of the wing spars, which could result in reduced structural integrity of the wing.

Final rule.

2001-16-06 Boeing: Amendment 39-12374. Docket 99-NM-367-AD. \n\n\tApplicability: Model 737-100 and -200 series airplanes, line number 1 through 310 inclusive, and 323; certificated in any category. \n\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 (g) 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 detect and correct cracking or corrosion of the upper and lower chords of the front and rear spars of the wing, which could result in reduced structural integrity of the wing, accomplish the following: \n\nInitial Detailed Visual and Eddy Current Inspections (Part I) \n\n\t(a) Within 12 months after the effective date of this AD: Do an initial detailed visual inspection to detect cracking or corrosion of the upper and lower chords of the front and rear spars, and an eddy current inspection to detect cracking of the vertical legs of the upper chords of the front and rear spars, per Part I of the Accomplishment Instructions of Boeing Service Bulletin 737-57-1067, Revision 4, dated November 7, 1991. Before further flight following the inspections, do the follow-on corrective actions required by paragraph (d) of this AD. \n\n\tNote 2: For the purposes of this AD, a detailed visual inspection is defined as: "An intensive examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate by the inspector. Inspection aids such as mirrors, magnifying lenses, etc. may be used. Surface cleaning and elaborate access procedures may be required." \n\nRepetitive Detailed Visual and Eddy Current Inspections (Part II) \n\n\t(b) Repeat the initial detailed visual inspection required by paragraph (a) of this AD at intervals not to exceed 12 months per Part II of the Accomplishment Instructions of Boeing Service Bulletin 737-57-1067, Revision 4, dated November 7, 1991. Before further flight following the inspection, do the follow-on corrective actions required by paragraph (d) of this AD. \n\n\t(c) Repeat the initial eddy current inspection required by paragraph (a) of this AD at intervals not to exceed 48 months per Part II of the Accomplishment Instructions of Boeing Service Bulletin 737-57-1067, Revision4, dated November 7, 1991. Before further flight following the inspection, do the follow-on corrective actions required by paragraph (d) of this AD. \n\nFollow-on Corrective Actions (Parts I, II, and III) \n\n\t(d) Do the follow-on corrective actions (including cleaning spar cavities, removing corrosion, and applying corrosion-inhibiting compound) required by paragraphs (d)(1), (d)(2), (d)(3), and (d)(4) of this AD, as applicable. \n\n\t\t(1) If no cracking or corrosion is found, apply a corrosion-inhibiting compound to the accessible areas of the upper and lower chords of both the front and rear spars per Part I or Part II of the Accomplishment Instructions of Boeing Service Bulletin 737-57-1067, Revision 4, dated November 7, 1991, as applicable. \n\n\t\t(2) If any corrosion is found, repair per Part III of the Accomplishment Instructions of Boeing Service Bulletin 737-57-1067, Revision 4, dated November 7, 1991. \n\n\t\t(3) If a horizontal crack is found in the upper chords of the front orrear spars, repair per paragraph (f) of this AD. \n\n\t\t(4) If any cracking is found other than that identified in paragraph (d)(3) of this AD, repair per paragraph (d)(4)(i) or (d)(4)(ii) of this AD, as applicable. \n\n\t\t\t(i) If damage of the chords of the front or rear spar is within the limits specified in the service bulletin, before further flight, repair per Part III of the Accomplishment Instructions of Boeing Service Bulletin 737-57-1067, Revision 4, dated November 7, 1991. \n\n\t\t\t(ii) If damage of the chords of the front or rear spar exceeds the limits specified in the service bulletin, before further flight, repair per paragraph (f) of this AD. \n\nInitial and Repetitive Eddy Current Inspections of Previous Repairs \n\n\t(e) For airplanes on which a previous repair to the upper chord of the front or rear spar was made per Boeing Service Bulletin 737-57-1067, Revision 3, dated May 24, 1990, or earlier revisions: Within 12 months after the effective date of this AD, do an eddy current inspection of the repair area to detect cracking per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA. Repeat this inspection thereafter at intervals not to exceed 12 months. If any discrepancy is found, before further flight, repair per paragraph (f) of this AD. For a repair method to be approved by the Manager, SACO, as required by this paragraph, the approval letter must specifically reference this AD. \n\nRepair \n\n\t(f) Repair (including removing corrosion; inspecting the rework area for cracks; refinishing the blend-out area; installing a nesting angle repair; and applying chemical film treatment, primer, sealant, and corrosion-inhibiting compound) any discrepancy specified in paragraphs (d)(3), (d)(4)(ii), and (e) of this AD, per a method approved by the Manager, Seattle ACO; or per data meeting the type certification basis of the airplane approved by a Boeing Designated Engineering Representative who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD. \n\nAlternative Methods of Compliance \n\n\t(g) An 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, FAA. 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\tNote 3: 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(h) Special 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(i) Except as provided by paragraphs (e) and (f) of this Ad, the actions shall be done in accordance with Boeing Service Bulletin 737-57-1067, Revision 4, dated November 7, 1991. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. 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\nEffective Date \n\n\t(j) This amendment becomes effective on September 24, 2001.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 737-100 and -200 series airplanes was published in the Federal Register on May 1, 2001 (66 FR 21700). That action proposed to require initial and repetitive inspections of certain areas of the wing spars to detect cracking or corrosion; and follow-on corrective actions and repair, if necessary. \n\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 comments received. \n\n\tThe manufacturer recommends adding certain wording for clarification to the section of the Notice of Proposed Rulemaking (NPRM) which is entitled "Explanation of Relevant Service Information." The FAA acknowledges that the suggested wording is more precise. However, since that wording does not reappear in the AD itself, no change is necessary. \n\n\tThe manufacturer also suggests that the "Applicability" section be changed to read "Model 737-100 and -200 series airplanes, line number 1 through 310 inclusive, and 323; certificated in any category." The effect of the suggested wording would be to clarify that the next generation of 737 models is specifically excluded. The FAA agrees with the need for this clarification and has changed the AD accordingly. \n\nConclusion \n\n\tAfter careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nCost Impact \n\n\tThere are approximately 168 Boeing Model 737 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 45 airplanes of U.S. registry will be affectedby this AD. \n\n\tThe FAA estimates that it will take approximately 30 work hours per airplane to do the initial detailed visual and eddy current inspections, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the initial inspections on U.S. operators is estimated to be $81,000, or $1,800 per airplane. \n\n\tThe FAA estimates that it will take approximately 30 work hours per airplane to do the repetitive inspections, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the inspections on U.S. operators is estimated to be $81,000, or $1,800 per airplane, per inspection cycle. \n\n\tThe cost impact figure discussed above is 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. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions. \n\nRegulatory Impact \n\n\tThe regulations adopted herein will not have a substantial direct effect 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, it is determined that this final rule does not have federalism implications under Executive Order 13132. \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 smallentities 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: \n\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\nSec. 39.13 (Amended) \n\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: