AD 96-18-11

This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-10-10 and -15 series airplanes, that requires repetitive inspections to detect cracks in the bulkhead tee caps, and repair and follow-on actions, if necessary. It also provides for an optional terminating modification for the repetitive inspections. This amendment is prompted by reports of cracking in the bulkhead tee caps at a fuselage station in the area of certain longerons due to fatigue. The actions specified by this AD are intended to prevent such fatigue cracking, which could result in loss of pressurization and damage to adjacent structure.

Final rule.

96-18-11 MCDONNELL DOUGLAS: Amendment 39-9735. Docket 95-NM-204-AD. \n\n\tApplicability: Model DC-10-10 and -15 series airplanes, as listed in McDonnell Douglas Service Bulletin DC10-53-168, dated August 9, 1995; 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 otherwise 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 (c) 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.Compliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent fatigue cracking, which could result in loss of pressurization and damage to adjacent structure, accomplish the following: \n\n\t(a)\tPrior to the accumulation of 20,000 total landings, or within 1,500 landings after the effective date of this AD, whichever occurs later, perform an eddy current and radiographic inspection, as applicable, to detect cracks in the bulkhead tee caps (left and right sides) in the area of longerons 38.0 through 41.0 at fuselage station Y=1156.000, in accordance with McDonnell Douglas Service Bulletin DC10-53-168, dated August 9, 1995. \n\n\t\t(1)\tIf no cracks are detected, repeat the inspections thereafter at intervals not to exceed 2,600 landings until paragraph (b) of this AD is accomplished. \n\n\t\t(2)\tIf any crack is detected, prior to further flight, accomplish the repair specified in either paragraph (a)(2)(i) or (a)(2)(ii) of this AD. \n\n\t\t\t(i)\tSplice in a new bulkhead tee cap section at cracked area of bulkhead tee cap in accordance with the service bulletin. Within 20,000 total landings after accomplishing this repair, perform eddy current inspections to detect cracks in accordance with the service bulletin. Repeat the inspections thereafter at intervals not to exceed 2,600 landings until paragraph (b) of this AD is accomplished. If any crack is detected, prior to further flight, repair it in accordance with a method approved by the Manager, Los Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\t\t\t(ii)\tRepair in accordance with a method approved by the Manager, Los Angeles ACO, FAA, Transport Airplane Directorate. \n\n\t(b)\tTerminating action for the repetitive inspections required by paragraphs (a)(1) and (a)(2)(i) of this AD is as follows: \n\n\t\t(1)\tAccomplish the preventative modification and eddy current open hole inspection in accordance with Condition 1 (no cracks in bulkhead tee cap), Option 2, of McDonnell Douglas Service Bulletin DC10-53-168, dated August 9, 1995. And \n\n\t\t(2)\tWithin 14,450 total landings following accomplishment of the modification specified in paragraph (b)(1) of this AD, perform an eddy current and radiographic inspection to detect cracks, in accordance with Condition 1 (no cracks in bulkhead tee cap), Option 2, of the service bulletin. \n\n\t\t\t(i)\tIf no cracks are detected, repeat the inspections thereafter at intervals not to exceed 3,950 landings. \n\n\t\t\t(ii)\tIf any crack is detected, prior to further flight, repair it in accordance with a method approved by the Manager, Los Angeles ACO, FAA, Transport Airplane Directorate. \n\n\t(c)\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(d)\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(e)\tThe inspections shall be done in accordance with McDonnell Douglas Service Bulletin DC10-53-168, dated August 9, 1995. 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 McDonnell Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Technical Publications Business Administration, Department C1-L51 (2-60). Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Los Angeles Aircraft Certification Office, Transport Airplane Directorate, 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(f)\tThis amendment becomes effective on October 10, 1996.

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-10-10 and -15 series airplanes was published in the Federal Register on March 28, 1995 (61 FR 13787). That action proposed to require repetitive inspections to detect cracks in the bulkhead tee caps, and repair and follow-on actions, if necessary. The proposal would also provide for an optional terminating modification for the repetitive inspections. \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 proposal. \n\nRequest to Ensure that Parts are Available \n\n\tOne commenter who supports the proposal is concerned that enough replacement parts may not be available to support the repair requirements of the proposed rule. \n\n\tThe FAA responds to this concern by stating that the manufacturer has advised that ample replacement tee cap splices will be available to the U.S. fleet in support any necessary repair that may be required as a result of the inspection required by this rule. \n\nRequest for a Revision of Initial Inspection Interval \n\n\tTwo commenters request that the proposed rule be revised to extend the initial inspection interval for airplanes on which the modification specified in the manufacturer's Structural Repair Manual (SRM), Chapter 53-40-00, Volume 1, has been accomplished. This modification involves installing an arrowhead doubler at station Y=1156.000. For airplanes with this modification, the commenters request that the initial inspection interval be changed from the proposed 1,500 landings to 2,200 landings. The commenters state that this extension will allow the inspection to be accomplished during regularly scheduled maintenance (i.e., a "C" check) at a main base. One commenter states that trying to accomplish a radiographic inspection at a field station (rather than at a main base) is very difficult and, if cracks are detected during the inspection, it is nearly impossible to repair them at a field station since trained personnel and appropriate equipment may not be available. \n\n\tThe FAA does not concur with the commenters' request for two reasons: \n\n\tFirst, the accomplishment of the SRM modification specified by the commenters has been determined -- via an assessment by both the airframe manufacturer and the FAA -- to have no effect on the time that cracks may initiate and grow in the bulkhead tee caps at fuselage station Y=1156.00. Although the McDonnell Douglas service bulletin cited in this rule does refer to that SRM modification, the reference is made only to discuss the fact that the accomplishment of the SRM modification affects the methodology that must be used for the inspection and installation of a preventative modificationof the bulkhead tee cap. Therefore, there is no basis to connect the inspection times required by this AD to whether or not the SRM modification has been accomplished. \n\n\tSecond, the compliance time for the initial inspection required by this AD is based on the reports of fatigue cracking in the bulkhead tee caps on airplanes that had accumulated between 56,394 and 72,931 total flight hours and between 21,629 and 26,094 total landings. The FAA has determined that inspections of this area by the time the airplane has accumulated at least 20,000 total landings will ensure that fatigue cracking is detected before it reaches a critical length. \n\n\tThe "1,500 landings" specified in the AD's compliance time is a "grace period" that was established to preclude grounding airplanes that have exceeded the 20,000-landing threshold. In determining an appropriate "grace period" for this action, the FAA not only considered the degree of urgency associated with addressing the unsafe condition,but normal scheduled maintenance for the majority of affected operators, recommendations of the manufacturer, analysis of the rate of crack growth, and reports of cracking found in the in-service fleet. In consideration of all of these factors, the FAA finds that the 1,500-landing "grace period" for initiating the required inspections on higher-time airplanes to be warranted, in that it represents an appropriate interval of time allowable for airplanes to continue to operate without compromising safety. \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 as proposed. \n\nCost Impact \n\n\tThere are approximately 133 Model McDonnell Douglas Model DC-10-10 and -15 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 121 airplanes of U.S. registry will be affected by this AD, that it will take approximately 3 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 $21,780, or $180 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. \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 discussedabove, 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. Theauthority 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: