AD 94-12-05

This amendment adopts a new airworthiness directive (AD), applicable to all McDonnell Douglas Model DC-10 series airplanes and Model KC-10A (military) airplanes, that requires inspections to detect cracks in wing stringer number 41; installation of a repair, if necessary; and modification of that stringer. This amendment is prompted by reports of fatigue cracks in outer wing stringer number 41. The actions specified by this AD are intended to prevent reduced structural integrity of the wing.

Final rule.

94-12-05 MCDONNELL DOUGLAS: Amendment 39-8933. Docket 93-NM-90-AD. \n\n\tApplicability: All Model DC-10-10, -10F, -15, -30, -30F, -40, and -40F series airplanes and Model KC-10A (military) airplanes; certificated in any category. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent reduced structural integrity of the wing, accomplish the following: \n\n\t(a)\tFor Model DC-10-10, -10F, and -15 series airplanes: Accomplish paragraphs (a)(1), (a)(2), (a)(3), and (a)(4) of this AD in accordance with McDonnell Douglas DC-10 Service Bulletin 57-114, Revision 1, dated July 26, 1993. \n\n\t\t(1)\tPrior to the accumulation of 6,500 total landings, or within 1,500 landings after the effective date of this AD, whichever occurs later: Perform an eddy current surface inspection or an eddy current bolt hole inspection to detect cracks on stringer number 41 on the left- and right-hand wings, in accordance with the service bulletin. \n\n\t\t(2)\tIf no crack is found,repeat the inspection thereafter at intervals not to exceed 4,000 landings. \n\n\t\t(3)\tIf any crack is found, prior to further flight, accomplish paragraph (a)(3)(i), (a)(3)(ii), or (a)(3)(iii) of this AD, as applicable. \n\n\t\t\t(i)\tIf any crack is found that extends upward from the fastener hole, and if that crack is outside the limits specified in Condition 2 of the service bulletin, accomplish a temporary repair in accordance with Condition 2, Phase I of the service bulletin, or a permanent repair in accordance with Condition 2, Phase II of the service bulletin. If the temporary repair is accomplished, prior to the accumulation of 5,000 landings after accomplishing that temporary repair, accomplish the permanent repair in accordance with Condition 2, Phase II of the service bulletin. After accomplishment of the permanent repair, no further action is required by this AD. \n\n\t\t\t(ii)\tIf any crack is found that extends downward from the fastener hole, and if that crack is outside thelimits specified in Condition 2 of the service bulletin, accomplish the permanent repair in accordance with Condition 2, Phase II of the service bulletin. After such repair, no further action is required by this AD. \n\n\t\t\t(iii)\tIf any crack is found in a fastener hole, and if that crack is within the limits specified in Condition 2 of the service bulletin, accomplish the preventative modification in accordance with Condition 1, Option II of the service bulletin. If the crack was detected using techniques other than the eddy current bolt hole inspection described in the service bulletin, prior to accomplishing the preventative modification, perform an eddy current bolt hole inspection to detect cracks, in accordance with the service bulletin, and accomplish paragraph (a)(3)(iii)(A), (a)(3)(iii)(B), or (a)(3)(iii)(C) of this AD, as applicable. \n\n\t\t\t\t(A)\tIf any crack is found that extends upward from the fastener hole, and if that crack is outside the limits specified in Condition 2of the service bulletin, accomplish the requirements of paragraph (a)(3)(i) of this AD. \n\n\t\t\t\t(B)\tIf any crack is found that extends downward from the fastener hole, and if that crack is outside the limits specified in Condition 2 of the service bulletin, accomplish the requirements of paragraph (a)(3)(ii) of this AD. \n\n\t\t\t\t(C)\tIf any crack is found that is within the limits specified in Condition 2 of the service bulletin, accomplish the preventative modification in accordance with Condition 1, Option II of the service bulletin. After accomplishment of the preventative modification, no further action is required by this AD. \n\n\t\t(4)\tExcept for airplanes on which the preventative modification (Condition 1, Option II) or the permanent repair (Condition 2, Phase II) has been accomplished, prior to the accumulation of 6,500 total landings, or within 5 years after the effective date of this AD, whichever occurs later: Perform an eddy current bolt hole inspection to detect cracks inthe fastener holes in accordance with the service bulletin. \n\n\t\t\t(i)\tIf no crack is found, or if any crack is found that is within the limits specified in Condition 2 of the service bulletin, prior to further flight, accomplish the preventative modification in accordance with Condition 1, Option II of the service bulletin. After accomplishment of the preventative modification, no further action is required by this AD. \n\n\t\t\t(ii)\tIf any crack is found that exceeds the limits specified in Condition 2 of the service bulletin, prior to further flight, accomplish a permanent repair in accordance with Condition 2, Phase II of the service bulletin. After accomplishment of the permanent repair, no further action is required by this AD. \n\n\t(b)\tFor Model DC-10-30, -30F, -40, and -40F series airplanes and Model KC-10A (military) airplanes: Accomplish paragraphs (b)(1), (b)(2), (b)(3), and (b)(4) of this AD in accordance with McDonnell Douglas DC-10 Service Bulletin 57-114, Revision 1, dated July 26, 1993. \n\n\t\t(1)\tPrior to the accumulation of 6,500 total landings, or within 1,500 landings after the effective date of this AD, whichever occurs later: Perform an eddy current surface inspection or an eddy current bolt hole inspection to detect cracks on stringer number 41 on the left- and right-hand wings in accordance with the service bulletin. \n\n\t\t(2)\tIf no crack is found, repeat the inspection thereafter at intervals not to exceed 3,200 landings. \n\n\t\t(3)\tIf any crack is found, prior to further flight, accomplish paragraph (b)(3)(i), (b)(3)(ii), or (b)(3)(iii) of this AD, as applicable. \n\n\t\t\t(i)\tIf any crack is found that extends upward from the fastener hole, and if that crack is outside the limits specified in Condition 2 of the service bulletin, accomplish a temporary repair in accordance with Condition 2, Phase I of the service bulletin, or a permanent repair in accordance with Condition 2, Phase II of the service bulletin. If the temporary repair is accomplished, prior to the accumulation of 5,000 landings after accomplishing that temporary repair, accomplish the permanent repair in accordance with Condition 2, Phase II of the service bulletin. After accomplishment of the permanent repair, no further action is required by this AD. \n\n\t\t\t(ii)\tIf any crack is found that extends downward from the fastener hole, and if that crack is outside the limits specified in Condition 2 of the service bulletin, accomplish the permanent repair in accordance with Condition 2, Phase II of the service bulletin. After such repair, no further action is required by this AD. \n\n\t\t\t(iii)\tIf any crack is found in a fastener hole, and if that crack is within the limits specified in Condition 2 of the service bulletin, accomplish the preventative modification in accordance with Condition 1, Option II of the service bulletin. If the crack was detected using techniques other than the eddy current bolt hole inspection described in the service bulletin, prior toaccomplishing the preventative modification, perform an eddy current bolt hole inspection to detect cracks, in accordance with the service bulletin, and accomplish paragraph (b)(3)(iii)(A), (b)(3)(iii)(B), or (b)(3)(iii)(C) of this AD, as applicable. \n\n\t\t\t\t(A)\tIf any crack is found that extends upward from the fastener hole, and if that crack is outside the limits specified in Condition 2 of the service bulletin, accomplish the requirements of paragraph (b)(3)(i) of this AD. \n\n\t\t\t\t(B)\tIf any crack is found that extends downward from the fastener hole, and if that crack is outside the limits specified in Condition 2 of the service bulletin, accomplish the requirements of paragraph (b)(3)(ii) of this AD. \n\n\t\t\t\t(C)\tIf any crack is found that is within the limits specified in Condition 2 of the service bulletin, accomplish the preventative modification in accordance with Condition 1, Option II of the service bulletin. After accomplishment of the preventative modification, no furtheraction is required by this AD. \n\n\t\t(4)\tExcept for airplanes on which the preventative modification (Condition 1, Option II) or the permanent repair (Condition 2, Phase II) has been accomplished, prior to the accumulation of 6,500 total landings, or within 5 years after the effective date of this AD, whichever occurs later: Perform an eddy current bolt hole inspection to detect cracks in the fastener holes in accordance with the service bulletin. \n\n\t\t\t(i)\tIf no crack is found, or if any crack is found that is within the limits specified in Condition 2 of the service bulletin, prior to further flight, accomplish the preventative modification in accordance with Condition 1, Option II of the service bulletin. After accomplishment of the preventative modification, no further action is required by this AD. \n\n\t\t\t(ii)\tIf any crack is found that exceeds the limits specified in Condition 2 of the service bulletin, prior to further flight, accomplish a permanent repair in accordance withCondition 2, Phase II of the service bulletin. After accomplishment of the permanent repair, no further action is required by this AD. \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: 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 Federal Aviation Regulations (FAR) 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, repairs, and modification shall be done in accordance with McDonnell Douglas DC-10 Service Bulletin 57-114, Revision 1, dated July 26, 1993. 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, P.O. Box 1771, Long Beach, California 90801-1771, Attention: Business Unit Manager, Technical Administrative Support, Dept. L51, M.C. 2-98. 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, 3229 East Spring Street, Long Beach, 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 July 13, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations to include an airworthiness directive (AD) that is applicable to all McDonnell Douglas Model DC-10 series airplanes and Model KC-10A (military) airplanes was published in the Federal Register on September 24, 1993 (58 FR 49946). That action proposed to require inspections to detect cracks in wing stringer number 41; installation of a repair, if necessary; and modification of that stringer. \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\tOne commenter supports the proposed rule. \n\n\tThe Air Transport Association (ATA) of America, on behalf of one of its members, requests that the FAA include a flow diagram in the proposal since its provisions are complex. The FAA does not concur. The FAA considers that the requirements of this AD are presented in a reasonably clear mannerin the text of the final rule. In addition, McDonnell Douglas DC-10 Service Bulletin 57-114, Revision 1, dated July 26, 1993, which is referenced in the AD as the appropriate source of service information, provides corresponding guidance for accomplishment of the actions required by this AD. \n\n\tATA also suggests that, prior to issuance of the final rule, the FAA should verify that the service bulletin will not create problems for operators, and that accomplishment of the service bulletin should be verified by an operator before the AD is finalized. One ATA member experienced difficulty accomplishing the permanent repair specified in the service bulletin because parts listed did not fit, drawings were erroneous, and fastener grip lengths were inadequate for the repair. The FAA concurs with the commenter's request. The FAA has conveyed these concerns to the manufacturer, and has verified that the initial problems expressed by the commenter have been corrected in Revision 1 of theservice bulletin. Since Revision 1 of the service bulletin was cited in the proposal as the appropriate source of service information, the FAA finds that no change to the AD is necessary. \n\n\tOne commenter requests that the FAA allow visual inspection methods to be used in lieu of the proposed eddy current inspection methods. The commenter indicates that fastener accessibility enables accomplishment of a visual inspection and provides an equivalent level of crack detection. The FAA does not concur. Based on the results of crack growth analysis, the FAA has determined that a visual inspection of the stringer cannot provide an acceptable level of crack detection. In addition, the FAA based the repetitive inspection intervals on the crack growth analysis results based upon the minimum crack length detectable by eddy current inspection. \n\n\tThe commenter also requests that credit be given for general visual inspections accomplished previously. A second commenter supports the proposed rule, but requests that the AD be revised to state that inspections accomplished within 1,500 landings prior to the effective date of the AD are acceptable in lieu of the initial inspection. The commenters provide no justification for these requests. Since the FAA has determined that a visual inspection of the stringer does not provide an acceptable level of crack detection, as discussed previously, the FAA considers that the requirement for eddy current inspections is appropriate and credit cannot be extended for general visual inspections accomplished previously. However, the phrase "unless accomplished previously," which appears in the "Compliance" paragraph of the final rule, provides credit for operators that have accomplished the required inspection prior to the effective date of this AD in accordance with McDonnell Douglas DC-10 Service Bulletin 57-114, Revision 1, dated July 26, 1993. \n\n\tOne commenter requests that the first inspection accomplished to comply with this AD be required during the airplane's next heavy maintenance visit if a general visual inspection has been accomplished prior to the effective date of the AD. The FAA does not concur. A general visual inspection of the stringer does not provide an acceptable level of crack detection, as discussed previously. In developing an appropriate initial compliance time for this action, the FAA considered the safety implications and normal maintenance schedules for timely accomplishment of the inspection. In consideration of these items, the FAA has determined that 6,500 total landings or 1,500 landings after the effective date of the AD, whichever occurs later, represents the maximum interval of time allowable wherein the inspection can reasonably be accomplished and an acceptable level of safety can be maintained. \n\n\tThe same commenter states that the service bulletin cited in the AD specifies that one reason for accomplishing the actions described in the service bulletin is to prevent unscheduled maintenance downtime for replacement of a cracked stringer; therefore, the commenter questions the need for this AD. The commenter adds that, to date, stringer 41 cracking has not impacted its maintenance due to the viable maintenance program currently in place. The commenter states that imposing an AD at this time would only complicate its maintenance program and would contribute little toward ensuring that the airplane wing structure is operating in good condition. \n\n\tThe FAA does not concur. As explained in the preamble of the proposal, the FAA has received reports of fatigue cracks in outer wing stringer number 41 and, in one case, complete failure of the stringer. Such fatigue cracking presents an unsafe condition in airplanes, since it could eventually lead to failure of the stringer and reduced structural integrity of the wing. The FAA has determined that this unsafe condition could exist or eventually develop on Model DC-10 series airplanes and Model KC-10A (military) airplanes, and that repetitive inspections of the affected area must be mandated to ensure that safety is not degraded. The appropriate vehicle for mandating such action to correct an unsafe condition is the airworthiness directive. \n\n\tOne commenter requests that the proposed compliance time for accomplishment of the initial inspection specified in paragraph (b)(1) of the proposal be changed from "(prior to the accumulation of 6,500 total landings, or within 1,500 landings after the effective date of the AD, whichever occurs later," to "(prior to the accumulation of 6,500 total landings, or within one year after the effective date of this AD, whichever occurs later." The commenter operates Model DC-10- 40 series airplanes of non-U.S. registry for training flights for cockpit crews. The commenter explains that, during one training flight period of a few weeks, the number of flight cycles accumulated may be more than 1,500 landings. The commenter adds that the proposed inspections and modifications require entry into the fuel tanks; therefore, the commenter plans to accomplish the initial inspections and the modifications during regularly scheduled maintenance. \n\n\tThe FAA does not concur with the commenter's request. Compliance times for AD's are normally based on a parameter related to failure of a particular component. In this case, fatigue cracking in outer wing stringer number 41 and subsequent failure of the stringer are undoubtedly related to the number of landings. The FAA has determined, in this case, that there is no apparent direct relationship between failure of the stringer and calendar time. In light of this, and in consideration of the average utilization rate of the affected U.S. operators and the practical aspects of orderly inspections of the U.S. fleet during regular maintenance periods, the FAA established the compliance times specified in this AD. The FAA maintains that those compliance times are appropriate. However, the FAA would consider a request for adjustment of the compliance time, in accordance with the provisions of paragraph (c) of this AD, provided that, for example, continued operational safety of the airplane could be assured until the required action is accomplished. \n\n\tOne commenter requests that, in order for the AD requirements to align with the actions described in the service bulletin, accomplishment of the preventative modification should be considered optional, and that operators should be permitted to accomplish repetitive inspections at intervals of 4,000 landings in lieu of the preventative modification. The FAA does not concur. The degree of assurance necessary as to the adequacy of inspections needed to maintain the safety of the aging transport airplane fleet, coupled with a better understanding of the human factors associated with numerous repetitive inspections, has caused the FAA to place less emphasis on repetitive inspections and more emphasis on design improvements and material replacement. Thus, in lieu of its previous position of continual inspection, and repair or modification on condition if cracks are found, the FAA has decided to require, whenever practicable, airplane modifications necessary to remove the source of the particular aging phenomena. \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 the AD. \n\n\tThere are approximately 426 Model DC-10 series airplanes and Model KC-10A (military) airplanes of the affected design in the worldwide fleet. The FAA estimates that 121 Model DC-10-10 and -15 series airplanes of U.S. registry will be affected by this AD, that it will take approximately 13.6 work hours per airplane to accomplish the required actions,and that the average labor rate is $55 per work hour. Required parts for Model DC-10-10 and -15 series airplanes will cost approximately $586 per airplane. Based on these figures, the total cost impact of the AD on U.S. operators of Model DC-10-10 and -15 series airplanes is estimated to be $161,414, or $1,334 per airplane. \n\n\tThe FAA estimates that 148 Model DC-10-30 and -40 series airplanes and Model KC-10A (military) airplanes of U.S. registry will be affected by this AD, that it will take approximately 13.6 work hours per airplane to accomplish the required actions, and that the average labor rate is $55 per work hour. Required parts for Model DC-10-30 and -40 series airplanes and Model KC-10A (military) airplanes will cost approximately $1,420 per airplane. Based on these figures, the total cost impact of the AD on U.S. operators of Model DC-10-30 and -40 series airplanes and Model KC-10A (military) airplanes is estimated to be $320,864, or $2,168 per airplane. \n\n\tBased on these figures, the total cost impact of the AD on U.S. operators is estimated to be $482,278. The total cost impact figure 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\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 14 CFR part 39 of the Federal Aviation Regulations as follows: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1.\tThe authority citation for part 39 continues to read as follows: \n\nAuthority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. \n\n§ 39.13 -(Amended) \n\n\t2.\tSection 39.13 is amended by adding the following new airworthiness directive: