AD 98-24-33

This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-9 and DC-9-80 series airplanes, Model MD-88 airplanes, and C-9 (military) series airplanes, that requires a one-time visual inspection to detect fatigue cracking of the lower left nose of certain longerons and the attaching frames; repair, if necessary; and installation of a preventive modification. This amendment is prompted by several reports of fatigue cracking of certain longerons and the attaching frames. The actions specified by this AD are intended to prevent such fatigue cracking, which could result in reduced structural integrity of the fuselage, and consequent loss of pressurization of the airplane.

Final rule.

98-24-33 MCDONNELL DOUGLAS: Amendment 39-10919. Docket 97-NM-21-AD. \n\n\tApplicability: Model DC-9-10, -20, -30, -40, -50 and C-9 (military) series airplanes, as listed in McDonnell Douglas DC-9 Service Bulletin 53-256, Revision 1, dated November 29, 1994; Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes and MD-88 airplanes, as listed in McDonnell Douglas MD-80 Service Bulletin 53-265, dated June 13, 1994; 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 (d) 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 fatigue cracking of longerons 22 through 26 and the attaching frames, which could result in reduced structural integrity of the fuselage, and consequent loss of pressurization of the airplane; accomplish the following: \n\n\t(a)\tPerform a visual inspection to detect cracking of the left lower nose of longerons 22 through 26 (inclusive) and the respective attaching frames at station frames Y=160.000 and Y=200.000; in accordance with McDonnell Douglas DC-9 Service Bulletin 53-256, dated August 12, 1993, or Revision 1, dated November 29, 1994 (for Models DC-9, -10, -20, -30, -40, -50, and C-9 (military) series airplanes); or McDonnell Douglas MD-80 Service Bulletin 53- 265, dated June 13, 1994 (for Model DC-9-81, -82, -83, and -87 series airplanes, and MD-88 airplanes); as applicable. Perform the inspection at the time specified in paragraph (a)(1) or (a)(2) of this AD, as applicable. \n\n\t\t(1)\tFor airplanes that have been inspected prior to the effective date of this AD in accordance with Corrosion Prevention and Control Program Document MDC-K4606, Corrosion Task No. 45-53301: Perform the inspection at the next scheduled repetitive corrosion task inspection. \n\n\t\t(2)\tFor airplanes other than those identified in paragraph (a)(1) of this AD: Perform the inspection prior to the accumulation of 40,000 total landings, or within 12,000 landings after the effective date of this AD, whichever occurs later: \n\n\t(b)\tIf no cracking is detected: Prior to further flight, install clips and doublers under the longeron flanges and shim the longerons in accordance with McDonnell Douglas DC-9 Service Bulletin 53-256, dated August 12, 1993, or Revision 1, dated November29, 1994 (for Models DC-9, -10, -20, -30, -40, -50, and C-9 (military) series airplanes); or McDonnell Douglas MD-80 Service Bulletin 53-265, dated June 13, 1994 (for Model DC-9-81, -82, -83, and -87 series airplanes, and MD-88 airplanes); as applicable. \n\n\t(c)\tIf any cracking is detected: Prior to further flight, repair the cracks and install clips and doublers under the longeron flanges and shim the longerons in accordance with McDonnell Douglas DC-9 Service Bulletin 53-256, dated August 12, 1993, or Revision 1, dated November 29, 1994 (for Models DC-9, -10, -20, -30, -40, -50, and C-9 (military) series airplanes); or McDonnell Douglas MD-80 Service Bulletin 53-265, dated June 13, 1994 (for Model DC-9-81, -82, -83, and -87 series airplanes, and MD-88 airplanes); as applicable. \n\n\t(d)\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, Los Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Los Angeles ACO. \n\n\tNOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles ACO. \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\n\t(f)\tThe actions shall be done in accordance with McDonnell Douglas DC-9 Service Bulletin 53-256, dated August 12, 1993; McDonnell Douglas DC-9 Service Bulletin 53-256, Revision 1, dated November 29, 1994; or McDonnell Douglas MD-80 Service Bulletin 53-265, dated June 13, 1994; as applicable. This incorporation by reference was approved by the Director of the FederalRegister in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from The Boeing Company, Douglas Products Division, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Technical Publications Business Administration, Dept. C1-L51 (2-60). Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Transport Airplane Directorate, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.\n\n\t (g) This amendment becomes effective on January 7, 1999.

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 and DC-9-80 series airplanes, Model MD-88 airplanes, and C-9 (military) series airplanes was published in the Federal Register on March 24, 1998 (63 FR 14047). That action proposed to require a one-time visual inspection to detect fatigue cracking of the lower left nose of certain longerons and the attaching frames; repair, if necessary; and installation of a preventive modification. \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\nSupport for the Proposal \n\n\tTwo commenters support the proposed rule. Request to Provide Option for Other Inspection Techniques \n\n\tOne commenter requests that the FAA revise the proposal to provide the option of using a dye check or a non-destructive testing (NDT) inspection method instead of (or in conjunction with) the required visual inspection. The FAA does not concur with this request. An inspection procedure was established several years ago to address inspections of the affected longerons. The FAA finds that introducing a new inspection procedure at this point would not be feasible. However, the FAA would consider a request for approval of a different inspection technique, in accordance with the provision of paragraph (d) of this AD, provided that adequate justification accompanies the request. \n\nRequests to Extend Compliance Time \n\n\tOne commenter states that the proposed grace period of 6,000 flight cycles is logistically impractical due to the heavy access required in the electrical/electric (E/E) equipment compartment to accomplish the inspection/modification. The commenter suggests that the compliance time for the modification be revised to coincide with the next scheduled inspection interval per Corrosion Task No. 45-53301 in the DC9/MD80 Corrosion Prevention and Control Document MDC-K4606, which is required by AD 92-22-08, amendment 39-8394 (57 FR 57895, December 8, 1992). \n\n\tAnother commenter also requests that, for airplanes that have accumulated 40,000 or more total landings, the FAA require an external eddy current inspection within 6,000 landings, and repetitive inspections every 2,500 landings until the terminating modification is accomplished. The commenter proposes that if a cracked longeron is found, only a repair per the SRM should be required prior to further flight - not the modification. The commenter suggests that the modification should be required at the next scheduled "D" check, but no later than 12,000 landings. The commenter indicates that it inspects the subject longerons at an interval of approximately 11,000 landings. Based on this inspection experience and the damage tolerance characteristics (i.e., crack detectability, crack growth rate, and residual strength) of the fuselage skin and longerons, the commenter states that the proposed grace period of 6,000 landings for airplanes that have accumulated 40,000 or more total landings is too restrictive and not justified. The commenter believes that an equivalent level of safety can be maintained with a repetitive inspection that is based on damage tolerance principles, while minimizing the operational impact to operators. Another commenter requests that, if no cracking is detected, the FAA allow the option of continuing repetitive inspections in lieu of accomplishing the modification prior to further flight, as specified in the proposal. \n\n\tThe FAA concurs partially. The FAA does not consider that repetitive inspections are warranted in this case since continual access to repetitively inspect the affected longerons is difficult. However, the FAA agrees that the proposed grace period can be extended. The FAA considers that an extension of that grace period to 12,000 landings will provide time for operators of large fleets to access, inspect, and modify. The FAA finds that such an extension of the grace period will not compromise the safety of the affected fleet. Paragraph (a)(2) of this AD has been revised accordingly. \n\n\tAdditionally, for airplanes that have been inspected prior to the effective date of this AD in accordance with Corrosion Task No. 45-53301 of DC9/MD80 Corrosion Prevention and Control Document MDC-K4606, the FAA has added a new paragraph (a)(1) to this final rule to require that the actions be accomplished at the next scheduled repetitive corrosion task inspection. \n\nRequests to Revise Cost Impact Information \n\n\tOne commenter does not object to the proposed rule, but requests that the cost impact information be revised to agree with the estimates presented in the referenced service bulletin (33.3 and 41.8 work hours) to provide industry with a more consistent cost estimate. Another commenter indicates that, based on the access requirements and actual work hours expended for similar actions, the proposed actions would take approximately 80 work hours per airplane with an elapsed time of 40 hours. The commenter believes that it is important to reflect accurate cost impact figures in the final rule since it will have a significant economic impact on operators. \n\n\tThe FAA does not concur. The number of work hours necessary to accomplish the required actions, specified as 25 in the cost impact information, was provided to the FAA by the manufacturer based on the best data available to date. No change to the cost impact information has been made. \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. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of theAD. \n\nCost Impact \n\n\tThere are approximately 2,000 Model DC-9, Model DC-9-80, and C-9 (military) series airplanes, and Model MD-88 airplanes, of the affected design in the worldwide fleet. The FAA estimates that 1,200 airplanes of U.S. registry will be affected by this AD, that it will take approximately 25 work hours per airplane (excluding work hours necessary to gain access and close up) to accomplish the required actions, 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 $1,800,000, or $1,500 per airplane. \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. \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\tAirtransportation, 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\nAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\n§ 39.13 (Amended) \n\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: