AD 99-08-22

This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-10 series airplanes and KC-10 (military) airplanes, that requires repetitive inspections to detect fatigue cracking of the rear spar cap of the horizontal stabilizer; and repair, if necessary. The amendment also would require a preventive modification of the rear spar cap of the horizontal stabilizer, which would constitute terminating action for the repetitive inspections. This amendment is prompted by reports of fatigue cracking of the rear spar cap of the horizontal stabilizer. The actions specified by this amendment are intended to prevent fatigue cracking of the rear spar cap of the horizontal stabilizer, which could result in reduced structural integrity of the horizontal stabilizer, and consequent reduced controllability of the airplane.

Final rule.

99-08-22 MCDONNELL DOUGLAS: Amendment 39-11131. Docket 98-NM-197-AD. \n\n\tApplicability: Model DC-10 series airplanes and KC-10 (military) airplanes, as listed in McDonnell Douglas Alert Service Bulletin DC10-55A028, dated April 27, 1998; 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 (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. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent fatigue cracking of the rear spar cap of the horizontal stabilizer, which could result in reduced structural integrity of the horizontal stabilizer, and consequent reduced controllability of the airplane, accomplish the following: \n\n\t(a)\tPrior to the accumulation of 18,000 total landings, or within 1,500 landings after the effective date of this AD, whichever occurs later: Perform a penetrant inspection or a high frequency eddy current inspection to detect fatigue cracking of the rear spar cap of the horizontal stabilizer, in accordance with McDonnell Douglas Alert Service Bulletin DC10-55A028, dated April 27, 1998. \n\n\tNOTE 2: Accomplishment of a penetrant inspection or a high frequency eddy current inspection to detect fatigue cracking of the rear spar cap of the horizontal stabilizer, in accordance with McDonnell Douglas Comtwx DC-10-COM-0047/SFY, dated December 11, 1997, prior to the effective date of this AD, is acceptable for compliance with the initial inspection requirements required by paragraph (a) of this AD. \n\n\t\t(1)\tIf no cracking is detected, repeat the inspection thereafter at intervals not to exceed 2,200 landings until accomplishment of the requirements of paragraph (b) of this AD. \n\n\t\t(2)\tIf any cracking is detected, prior to further flight, repair in accordance with the alert service bulletin. Repeat the inspection thereafter at intervals not to exceed 2,200 landings until accomplishment of the requirements of paragraph (b) of this AD. \n\n\t(b)\tWithin 5 years after the effective date of this AD or prior to the accumulation of 18,000 total landings, whichever occurs later: Perform a penetrant inspection or a high frequency eddy current inspection to detect fatigue cracking of the rear spar cap of the horizontal stabilizer, in accordance with McDonnell Douglas Alert Service Bulletin DC10-55A028, dated April 27, 1998. \n\n\t\t(1)\tIf no cracking is detected, prior to further flight, perform the preventive modification of the rear spar cap of the horizontal stabilizer, in accordance with the alert service bulletin. Accomplishment of this modification constitutes terminating action for the requirements of this AD. \n\n\t\t(2)\tIf any cracking is detected, prior to further flight, repair, and perform the preventive modification of the rear spar cap of the horizontal stabilizer, in accordance with the alert service bulletin. Accomplishment of the modification constitutes terminating action for the requirements of this AD. \n\nAlternative Methods of Compliance \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 andthen send it to the Manager, Los Angeles 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 Los Angeles ACO. \n\nSpecial Flight Permits \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\nIncorporation by Reference \n\n\t(e)\tThe actions shall be done in accordance with McDonnell Douglas Alert Service Bulletin DC10-55A028, dated April 27, 1998. 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 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(f)\tThis amendment becomes effective on May 21, 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-10 series airplanes and KC-10 (military) airplanes was published in the Federal Register on August 4, 1998 (63 FR 41479). That action proposed to require repetitive penetrant inspections or high frequency eddy current inspections to detect fatigue cracking of the rear spar cap of the horizontal stabilizer; and repair, if necessary. That action also proposed to require a preventive modification of the rear spar cap of the horizontal stabilizer, which would constitute terminating action 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\tOne commenter supports the proposed rule. \n\nRequest to Revise theCompliance Time of the Terminating Action \n\n\tOne commenter requests that the proposed compliance time for accomplishment of the terminating modification be revised from "within 5 years" to "within 5 years or prior to the accumulation of 18,000 landings after the effective date of the AD, whichever occurs later." The commenter contends that such a revision of the compliance time would allow the preventive modification installation on low-time DC-10 series airplanes to be consistent with the initial inspection threshold of the proposal. \n\n\tThe FAA concurs partially. It is appropriate to specify an 18,000-landing compliance time for accomplishment of the terminating action. However, to be consistent with the compliance time specified in paragraph (a) of this AD, that threshold must include total landings accumulated on the airplane, not just those accumulated after the effective of this AD, as requested by the commenter. \n\nRequests for Credit for Previous Accomplishment of the AD Requirements \n\n\tOne commenter requests that credit be given for previous accomplishment of the proposed initial inspection. That commenter specifically requests that credit for the initial inspection be given if it was accomplished in accordance with McDonnell Douglas Comtwx DC-10-COM-0047/SFY, dated December 11, 1997. Another commenter requests that credit be given for initial inspections and installation of the preventive modification that were accomplished prior to the effective date of the AD in accordance with the service bulletin specified in the proposal. \n\n\tThe FAA has reviewed the referenced comtwx and concurs that credit may be given for the accomplishment of the initial inspection required by this AD if it was done in accordance with the comtwx referenced by the commenter. The FAA also notes that the comtwx is referenced in McDonnell Douglas Alert Service Bulletin DC10-55A028, dated April 27, 1998, (which is the appropriate service information for this AD), as an additional source of service information. Therefore, the FAA has revised the final rule to add a new "Note 2" to give credit to operators that may have accomplished previously the initial inspection in accordance with McDonnell Douglas Comtwx DC-10-COM-0047/SFY, dated December 11, 1997. \n\n\tThe FAA also concurs with the request to allow credit for accomplishment of actions specified in McDonnell Douglas Alert Service Bulletin DC10-55A028, dated April 27, 1998, that were accomplished prior to the effective date of this AD. The FAA notes that operators are generally given credit for work accomplished previously if the work is performed in accordance with the final rule by means of the phrase in the compliance section of the AD that states, "Required as indicated, unless accomplished previously." Therefore, no change in the final rule is necessary in this regard. \n\nRequest to Justify That Unsafe Condition Exists on Certain Airplanes \n\n\tOne commenter notes that the horizontal stabilizer center section of Model DC-10-30/40 series airplanes is different than that of Model DC-10-10 series airplanes, and that reports of cracking of the rear spar cap of the horizontal stabilizer have only occurred on Model DC-10-10 series airplanes. Therefore, the commenter questions the need to require installation of the proposed modification on DC-10-30/40 series airplanes, and requests that the FAA provide justification that an unsafe condition actually exists on the Model DC-10-30/40 series airplanes. The FAA infers that the commenter is requesting the FAA remove Model DC-10-30/40 series airplanes from the applicability of the proposal if the FAA cannot justify that an unsafe condition exists for that model. \n\n\tThe FAA does not concur that further justification of an unsafe condition on DC-10-30/40 series airplanes is necessary, or that Model DC-10-30/40 series models should be removed from the applicability of this AD. Although the structure of the horizontal stabilizer center section is thicker on Model DC-10-30/40 series airplanes than the same structure on Model DC-10-10 series airplanes, the FAA finds that the thicker structure is necessary because of the higher loads sustained by Model DC-10-30/40 series airplanes. The airplane manufacturer also concurs that fatigue cracking of the horizontal stabilizer is as likely to develop on a Model DC-10-30/40 series airplane as on a Model DC-10-10 series airplane. Therefore, no change to the final rule is necessary. \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 the AD. \n\nCost Impact \n\n\tThere are approximately 420 airplanes of the affected design in the worldwide fleet. The FAA estimates that 242 airplanes of U.S. registry (124 Group 1 airplanes; 118 Group 2 airplanes) will be affected by this AD. \n\n\tIt will take approximately 2 work hours per airplane to accomplish the required inspections, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the inspections required by this AD on U.S. operators for Groups 1 and 2 airplanes is estimated to be $29,040, or $120 per airplane, per inspection cycle. \n\n\tIt will take approximately 34 work hours per airplane to accomplish the terminating modification, at an average labor rate of $60 per work hour. Required parts will cost approximately $6,236 per airplane for Group 1 airplanes, or $6,349 per airplane for Group 2 airplanes. Based on these figures, the cost impact of the modification required by this AD on U.S. operators of Group 1 airplanes is estimated to be $1,026,224, or $8,276 per airplane; and, for Group 2 airplanes, $989,902, or $8,389 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. \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\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\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: