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 McDonnell Douglas Model DC-9-10, -20, -30, -40, and -50 series airplanes; and C-9 airplanes; was published in the Federal Register on September 20, 2001 (66 FR 48384). That action proposed to require repetitive general visual and x-ray inspections to detect cracks of the upper and lower corners and upper center of the door cutout of the aft pressure bulkhead; corrective actions, if necessary; and follow-on actions. For certain airplanes, the amendment also requires modification of the ventral aft pressure bulkhead. \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\nRequests To Revise Certain Inspection Requirements \n\n\tThree commenters request revision of the inspection requirements in paragraph (b) of the proposed rule. The rationales for these requests are as follows: \n\nOne commenter suggests revising paragraph (b) of the proposed rule to specify the same inspections cited in McDonnell Douglas Service Bulletin DC9-53-137, Revision 07, dated February 6, 2001, which was cited as the appropriate source of service information for this AD. The commenter states that paragraph (b) of the proposed rule is misleading because it incorrectly implies that a repair will always be required or that a preventive modification is required. In addition, that paragraph does not allow for continuing visual and x-ray inspections as specified in the previously referenced service bulletin. \n\nOne commenter requests clarification of the inspection procedures specified in the proposed rule. Paragraph (b) of the proposed rule specifies visual and eddy current inspections within 8,000 landings after accomplishment of the visual and x-ray inspections required by paragraph (a) of this AD. However, Service Bulletin DC9-53-137, Revision 07, specifies visual and eddy current inspections after a repair or preventive modification is installed. The proposed rule would not require a preventive modification if no cracks are found. However, the no-crack procedures specified in the service bulletin provide the option of either accomplishing the preventive modification and thereafter a visual and eddy current inspection, or not accomplishing the modification and continuing the visual and x-ray inspections at various intervals depending on the condition. \n\nOne commenter considers that the proposed rule should require visual and eddy current inspections only if no cracks are found and interim preventive repairs are performed per Service Bulletin DC9-53-137, Revision 07. The commenter suggests clarifying that interim preventive repairs are to be performed per the service bulletin, and that continued visual and x-ray inspections are required for unmodified corners. The inspection requirements of paragraph (b) are different from those specified in the previously referenced service bulletin. Although paragraph (b) of the proposed rule requires inspections at intervals of 8,000 landings after accomplishment of the inspections required by paragraph (a) of the proposed rule, the service bulletin specifies inspections after accomplishment of a repair or preventive modification. The service bulletin also provides the option of either accomplishing the preventive modification followed by the inspections, or not accomplishing the modification and continuing the inspections at specific intervals. \n\n\tThe FAA concurs with the commenter's requests to revise and clarify the inspection requirements. In making this decision, we have reviewed the Accomplishment Instructions of the service bulletin and the inspection requirements of paragraph (b) of the proposed rule. We point out that the intent of paragraph (b) of the proposed rule is to require the same inspections as those specified by the service bulletin. Therefore, we have revised paragraph (b) in the final rule to also include paragraphs (b)(1) and (b)(2). We consider that this change provides an acceptable level of safety for the fleet. \n\nRequest To Clarify the Repetitive Inspection Intervals \n\n\tOne commenter states that, if no crack is detected, paragraph (b) in the proposed rule requires visual and eddy current inspections per Revision 07 of Service Bulletin DC9-53-137, within 8,000 landings after accomplishing the visual and x-ray inspections required by paragraph (a) of the proposed rule. The commenter states that it had previously accomplished modifications per Revision 04, or earlier, of McDonnell Douglas DC-9 Service Bulletin 53-137, and that an alternative method of compliance (AMOC) to AD 85-01-02 R1, amendment 39-5241 (51 FR 6101, February 20, 1986), permits repetitive inspections at intervals of 15,000 landings until accomplishment of the terminating action per McDonnell DouglasDC-9 Service Bulletin 53-166. With this in mind, the commenter asks whether the repetitive intervals of previously modified airplanes will be reduced from 15,000 landings to 8,000 landings regardless of modification/repair status. \n\n\tThe FAA concurs that clarification of the repetitive inspection intervals for previously repaired or modified airplanes (interim preventive repairs) is necessary. We point out that McDonnell Douglas DC-9 Service Bulletin 53-137, Revision 05, dated August 29, 2000, changed the inspection method and the inspection intervals for the aft pressure bulkhead corners that previously have been repaired or modified per earlier revisions of the service bulletin. In addition, the inspection procedures specified in Revision 05 of the service bulletin also were approved as an AMOC for the accomplishment of AD 85-01-02 R1. Although earlier revisions of the service bulletin specify "visual and x-ray" inspections of previously repaired or modified corners, Revision 05 and later revisions of the service bulletin specify "visual and eddy current" inspections for those airplanes. After the type of inspection was changed, the manufacturer reconsidered the inspection intervals necessary for previously repaired or modified corners if no cracks are detected. As a result, for those airplanes, the manufacturer recommends inspection intervals of 8,000 landings for "visual and eddy current" inspections instead of 15,000 landings for "visual and x-ray" inspections. \n\n\tAfter reconsidering the manufacturer's recommendation, we have determined that the compliance times recommended in Revision 07 of the service bulletin are adequate in maintaining the safety of the fleet. It is necessary to revise paragraph (b) of the proposed rule to clarify our intent regarding the type of inspection and inspection intervals that are specified in paragraph 3.B. ("Work Instructions") of the service bulletin (which was cited in the proposed rule as the appropriate source of serviceinformation). We point out that the compliance times specified in Revision 07 of the service bulletin vary according to the conditions and groups of airplanes specified in paragraph 3.B. ("Work Instructions") of the service bulletin. As a result, we have reformatted paragraph (b) of the final rule to include paragraphs (b)(1) and (b)(2), which require accomplishment of the inspections at the times specified in Revision 07 of the service bulletin, as applicable. We consider that these changes only clarify the required inspections and related compliance times, and do not impose an additional burden on any operator or necessitate providing an additional opportunity for public comment. \n\nRequest To Revise Type of Inspection per the Service Information \n\n\tOne commenter states that the definition of a "general visual inspection" in Note 2 of the proposed rule is not the same as that of a "visual inspection" in Service Bulletin DC9-53-137, Revision 07. The commenter states that the service bulletin has specific visual inspection requirements that are included in Service Sketch 2934E and SN09530002. The commenter considers that the proposed rule should reflect the same type of inspection as that cited in the service information. \n\n\tThe FAA concurs and agrees that the final rule should reflect the same inspections specified by the service information. In the final rule we have deleted Note 2 to remove the definition of a "general visual inspection." We also have changed all references throughout the final rule, including paragraphs (a) and (b), to specify a "visual inspection" instead of a "general visual inspection." \n\nRequest To Give Credit for Previously Accomplished Alternative Methods of Compliance (AMOCs) \n\n\tOne commenter requests that credit be given to operators who have accomplished previously approved AMOCs per AD 85-01-02 R1 or AD 96-10-11, amendment 39-9618 (61 FR 24675, May 16, 1996). Another commenter asks how the requirements of this AD affect previous AMOC approvals for inspections, repairs, and modifications per AD 85-01-02 R1 and AD 96-10-11. In addition, this commenter asks whether AMOCs issued per AD 90-18-03, amendment 39-6701 (55 FR 34704, August 24, 1990), are still considered valid. \n\n\tThe FAA concurs. In addition, we point out that AD 90-18-03 was superseded by AD 96-10-11, which gave credit for AMOCs previously issued per AD 90-18-03. However, because AD 90-18-03 was removed from the regulations, it is only necessary to give credit for the prior accomplishment of AD 85-01-02 R1 and AD 96-10-11 in paragraph (i)(2) of the final rule. We have revised the final rule accordingly. \n\nRequest To Clarify Previously Issued ADs and Effect on Compliance Times in Follow-on ADs \n\n\tOne commenter requests clarification of the difference between a standalone AD that supersedes an earlier AD, and a separate AD with a later action to rescind that AD. The commenter also asks the following questions: \n\nIf the FAA rescinds AD 85-01-02 R1, what happens to AD 80-10-03, amendment 39-3769 (45 FR 31052, May 15, 1980), that was superseded by AD 85-01-02, amendment 39-4978 (50 FR 2043, January 15, 1985), and how are the concurrent service bulletin requirements affected by this decision? \n\nAD 85-01-02 R1 requires that the procedures specified by the service bulletins be accomplished within landing or time limits that have already passed for most applicable airplanes. How does rescinding AD 85-01-02 R1 affect this compliance? \n\n\tThe FAA concurs and agrees that it is necessary to clarify the difference between the two types of ADs. In response, we point out that in the preamble of the proposed AD, in "Other Relevant Rulemaking," we stated that the FAA normally would issue a proposed AD to supersede AD 85-01-02 R1. However, because of the complexity of the requirements in AD 85-01-02 R1, we issued a standalone AD, which includes terminating action for the repetitive inspection requirements of AD 85-01-02 R1. Once a final rule has been issued and becomes effective, we plan to rescind AD 85-01-02 R1. After considering the commenter's two questions, we infer that the commenter wants us to clarify how previously issued ADs affect the compliance times in follow-on ADs. In response, we point out that AD 80-10-03 was superseded by AD 85-01-02, which removed AD 80-10-03 from the regulations. As a result, the concurrent service bulletin procedures required by AD 80-10-03 are no longer in effect. Likewise, after AD 85-01-02 R1 is rescinded, the compliance times required by that AD per the service bulletins are no longer a factor. No change to the final rule is necessary in this regard. \n\nRequest To Include Additional Corrective Actions \n\n\tThe commenter states that the proposed rule needs to address what happens if an operator finds "something on a corner of an airplane" that they are unable to inspect per Revision 07 of Service Bulletin DC9-53-137. The commenter adds that guidance is needed when the proposed rule cannot be complied with, and operators need to know what to do. After contacting the manufacturer for clarification of what was meant by "something on a corner of an airplane," the commenter stated that the phrase refers to any previous repair on the aft pressure bulkhead that any operator may not be able to inspect per the service bulletin. \n\n\tThe FAA does not concur. We point out that the proposed rule does not need to include additional corrective actions because paragraph (i)(1) of this AD includes a provision for operators to request an AMOC for such an inspection requirement. No change to the final rule is \nnecessary in this regard. \n\nRequest To Cite an Additional Service Bulletin \n\n\tThe commenter asks why some of the Boeing service bulletins listed in AD 85-01-02 R1 are included in the proposed rule and others are not. For example, McDonnell Douglas DC-9 Service Bulletin A53-144 is cited in AD 85-01-02 R1, but is not cited in this proposed rule. The commenter considers that, if certain other service bulletins specified in that AD are included in this proposed rule, we also need to include DC-9 Service Bulletin A53-144. This is necessary in case any airplane that has not been modified per the AD is brought into the United States, and to prevent any operator from performing a repair in the area and not also accomplishing the modification. \n\n\tThe FAA does not concur. We point out that it is unnecessary to include a reference to a service bulletin unless the specified procedures are required by the proposed rule. Because the procedures specified in DC-9 Service Bulletin A53-144 are not required by the final rule, no change to the final rule is necessary in this regard. \n\nExplanation of Changes Made to the Proposal \n\n\tThe FAA has determined that it is necessary to revise the final rule and has made the following changes: \n\nIn the "Cost Impact" section, we have clarified that 5 work hours per airplane is required for accomplishment of the required "inspections" instead of the required "actions." \n\nParagraph (a) specifies that the requirements of that paragraph also apply to airplanes on which the modification has not been accomplished per paragraph (g) of this AD, which specifies terminating action for the repetitive inspections required by paragraphs (b) and (c) of this AD. This change clarifies that if the specified modification has not been done, visual and x-ray inspections must be done within the compliance time specified in paragraph (a) of this AD. \n\nParagraph (d)(2) specifies that accomplishment of the modification specified by paragraph (d)(2) constitutes terminating action for the repetitive inspection requirements of paragraphs (b) and (c)(2) of this AD. \n\nParagraph (i) includes two new subparagraphs. Paragraph (i)(2) is added to give credit for AMOCs previously accomplished in accordance with AD 85-01-02 R1 or AD 96-10-11. Paragraph (i)(3) is added to specify that, if an inspection of the aft pressure bulkhead cannot be accomplished per the service bulletin, operators also may accomplish the inspection per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings. \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 changes previously described. We also have determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nCost Impact \n\n\tThere are approximately 700 Model DC-9-10, -20, -30, -40, and -50 series airplanes; and C-9 airplanes of the affected design in the worldwide fleet. The FAA estimates that 397 airplanes of U.S. registry will be affected by this AD. \n\n\tIt will take approximately 5 work hours per airplane to accomplish the required inspections, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $119,100, or $300 per airplane. \n\n\tFor certain airplanes, it will take approximately between 21 and 26 work hours per airplane depending on the airplane configuration to accomplish the modification specified in McDonnell Douglas DC-9 Service Bulletin 53-165, Revision 3, dated May 3, 1989, at an average labor rate of $60 per work hour. Required parts will cost approximately between $3,470 and $11,831 per airplane, depending on the airplane configuration. Based on these figures, the cost impact of this modification on U.S. operators is estimated to be between $4,730, or $13,391 per airplane. \n\n\tFor certain airplanes, it will take approximately 9 work hours per airplane to accomplish the modification specified in McDonnell Douglas DC-9 Service Bulletin 53-157, Revision 1, dated January 7, 1985, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this modification on U.S. operators is estimated to be $540 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. 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 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 part39 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: