AD 94-20-10

This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-10-10, -15, -30, and -40 series airplanes and KC-10A (military) airplanes, that requires inspections to detect fatigue-related cracking in certain areas of the horizontal stabilizer; and repair of cracked parts. It also requires installation of terminating modifications, which, when accomplished, would eliminate the repetitive inspections. This amendment is prompted by reports of fatigue-related cracks found on the horizontal stabilizer. The actions specified by this AD are intended to prevent loss of the load carrying and fail safe capability of the horizontal stabilizer, damage to the adjacent structure, and subsequent reduced structural integrity of the airplane, due to the problems associated with fatigue cracking.

Final rule; request for comments.

94-20-10 MCDONNELL DOUGLAS: Amendment 39-9039. Docket 93-NM-221-AD. \n\n\tApplicability: Model DC-10-10, -15, -30, and -40 series airplanes and KC-10A (military) airplanes; as listed in McDonnell Douglas DC-10 Service Bulletins 55-24 and 55-25, Revision 1, both dated August 3, 1994; certificated in any category. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent reduced structural integrity of the airplane, accomplish the following: \n\n\t(a)\tFor Model DC-10-10 and -15 series airplanes: Prior to the accumulation of 12,000 total landings, or within 90 days after the effective date of this AD, whichever occurs later, unless previously accomplished within the last 4,500 landings, perform either an initial an eddy current inspection or visual inspection to detect fatigue-related cracking of the forward spar upper caps on the horizontal stabilizer, in accordance with McDonnell Douglas DC-10 Service Bulletin 55-24, Revision 1, dated August 3, 1994.NOTE 1: Eddy current inspections accomplished in accordance with McDonnell Douglas DC-10 Service Bulletin 55-24, dated October 25, 1993, are considered acceptable for compliance with this paragraph. \n\n\t\t(1)\tIf any crack is detected, prior to further flight, repair the crack in accordance with a method approved by the Manager, Los Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\t\t(2)\tIf no crack is detected, perform repetitive inspections thereafter in accordance with the service bulletin and in accordance with the following schedule: \n\n\t\t\t(i)\tIf the initial inspection was performed using visual techniques, perform an eddy current inspection within 1,000 landings after the visual inspection. Thereafter, repeat the eddy current inspection at intervals not to exceed 4,500 landings. \n\n\t\t\t(ii)\tIf the initial inspection was performed using eddy current techniques, repeat the eddy current inspection thereafter at intervals not to exceed 4,500landings. \n\n\t(b)\tFor Model DC-10-10 and -15 series airplanes: Prior to the accumulation of 10,000 total landings, or within 120 days after the effective date of this AD, whichever occurs later, unless previously accomplished within the last 4,500 landings, perform either an initial eddy current inspection or visual inspection to detect fatigue-related cracking of the forward upper skin panel of the horizontal stabilizer, in accordance with McDonnell Douglas DC-10 Service Bulletin 55-25, Revision 1, dated August 3, 1994. \n\n\tNOTE 2: Eddy current inspections performed in accordance with McDonnell Douglas DC-10 Service Bulletin 55-25, dated October 25, 1993, are considered acceptable for compliance with this paragraph. \n\n\t\t(1)\tIf any crack is detected, prior to further flight, repair the crack in accordance with a method approved by the Manager, Los Angeles ACO, FAA, Transport Airplane Directorate. \n\n\t\t(2)\tIf no crack is detected, perform repetitive eddy current inspections thereafter in accordance with the service bulletin and in accordance with the following schedule: \n\n\t\t\t(i)\tIf the initial inspection was performed using visual techniques, perform an eddy current inspection within 1,000 landings after the visual inspection. Thereafter, repeat the eddy current inspection at intervals not to exceed 4,500 landings. \n\n\t\t\t(ii)\tIf the initial inspection was performed using eddy current techniques, repeat the eddy current inspection thereafter at intervals not to exceed 4,500 landings. \n\n\t(c)\tFor Model DC-10-30 and -40 series airplanes: Prior to the accumulation of 17,500 total landings, or within 120 days after the effective date of this AD, whichever occurs later, unless previously accomplished within the last 4,500 landings, perform either an initial eddy current inspection or visual inspection to detect fatigue-related cracking of the forward upper skin panel of the horizontal stabilizer, in accordance with McDonnell Douglas DC-10 Service Bulletin 55-25, Revision 1, dated August 3, 1994. \n\n\tNOTE 3: Eddy current inspections performed in accordance with McDonnell Douglas DC-10 Service Bulletin 55-25, dated October 25, 1993, are considered acceptable for compliance with this paragraph. \n\n\t\t(1)\tIf any crack is detected, prior to further flight, repair the crack in accordance with a method approved by the Manager, Los Angeles ACO, FAA, Transport Airplane Directorate. \n\n\t\t(2)\tIf no crack is detected, perform repetitive eddy current inspections thereafter in accordance with the service bulletin and in accordance with the following schedule: \n\n\t\t\t(i)\tIf the initial inspection was performed using visual techniques, perform an eddy current inspection within 1,000 landings after the visual inspection. Thereafter, repeat the eddy current inspection at intervals not to exceed 4,500 landings. \n\n\t\t\t(ii)\tIf the initial inspection was performed using eddy current techniques, repeat the eddy current inspection thereafter at intervals notto exceed 4,500 landings. \n\n\t(d)\tFor all airplanes: Install the preventative modifications specified in McDonnell Douglas DC-10 Service Bulletin 55-24, Revision 1, dated August 3, 1994; and McDonnell Douglas DC-10 Service Bulletin 55-25, Revision 1, dated August 3, 1994; in accordance with the following schedule. Accomplishment of these preventative modifications constitutes terminating action for the repetitive inspections required by this AD. \n\n\tNOTE 4: Accomplishment of these preventative modifications in accordance with McDonnell Douglas DC-10 Service Bulletin 55-24, dated October 25, 1993; or McDonnell Douglas DC-10 Service Bulletin 55-25, dated October 25, 1993; as applicable; is considered acceptable for compliance with this paragraph. \n\n\t\t(1)\tFor Model DC-10-10 and -15 series airplanes: \n\n\t\t\t(i)\tPrior to the accumulation of 21,000 total landings, or within 5 years after the effective date of this AD, whichever occurs later, accomplish the preventative modificationsof the forward spar upper cap on the horizontal stabilizer in accordance with McDonnell Douglas DC-10 Service Bulletin 55-24, Revision 1, dated August 3, 1994. \n\n\t\t\t(ii)\tPrior to the accumulation of 19,000 total landings, or within 5 years after the effective date of this AD, whichever occurs later, accomplish the modification of the forward upper skin panel on the horizontal stabilizer in accordance with McDonnell Douglas DC-10 Service Bulletin 55-25, Revision 1, dated August 3, 1994. \n\n\t\t(2)\tFor Model DC-10-30 and -40 series airplanes: \n\n\t\t\t(i)\tPrior to the accumulation of 44,250 total landings, or within 5 years after the effective date of this AD, whichever occurs later, accomplish the modification of the forward spar upper cap on the horizontal stabilizer in accordance with McDonnell Douglas DC-10 Service Bulletin 55-24, Revision 1, dated August 3, 1994. \n\n\t\t\t(ii)\tPrior to the accumulation of 26,500 total landings, or within 5 years after the effective date of this AD, whichever occurs later, accomplish the modification of the forward upper skin panel on the horizontal stabilizer in accordance with McDonnell Douglas DC-10 Service Bulletin 55-25, Revision 1, dated August 3, 1994. \n\n\t(e)\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 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 5: 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(f)\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(g)\tThe inspections and modifications shall be done in accordance with McDonnell Douglas DC-10 Service Bulletin 55-24, Revision 1, dated August 3, 1994; and McDonnell Douglas DC-10 Service Bulletin 55-25, Revision 1, dated August 3, 1994. 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(h)\tThis amendment becomes effective on October 31, 1994.

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, -15, -30, and -40 series airplanes and KC-10A (military) airplanes was published as a notice of proposed rulemaking (NPRM) in the Federal Register on March 30, 1994 (59 FR 14800). That action proposed to require inspections to detect fatigue-related cracking in certain areas of the horizontal stabilizer; and repair of cracked parts. It also proposed to require the installation of certain terminating modifications that would eliminate the need for the repetitive inspections. \n\nImmediate Adoption of this Regulation \n\n\tSince issuance of the NPRM, one operator has reported finding a crack in the area of the forward spar upper cap on the horizontal stabilizer on a Model DC-10-10 series airplane that had accumulated approximately 16,000 landings. This evidence indicates that fatigue cracking may begin in this area much earlier than what was previously considered. In light of this, the FAA has reconsidered the compliance time proposed for the initiation of inspections to detect cracking in this subject area on these airplanes. The FAA now has determined that the initiation of inspections of Model DC-10-10 and -15 series airplanes must begin prior to the accumulation of 12,000 total landings or 90 days after the effective date of this AD, whichever occurs later. (The compliance time for this action that was proposed in the notice was 18,000 total landings.) The lowered threshold of 12,000 total landings is necessary to ensure that cracking is detected and corrected in a timely manner, and to prevent the loss of load-carrying and fail safe capability of the horizontal stabilizer due to the problems associated with fatigue cracking. The compliance time for the inspections specified in paragraph (a) of this final rule has been revised accordingly.In making this revision, the FAA finds that, with respect to the reduced compliance threshold, a situation exists that requires the immediate adoption of this regulation. Therefore, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. \n\nComments Invited \n\n\tAlthough this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in lightof the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed. \n\n\tComments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket. \n\n\tCommenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 93-NM-221-AD." The postcard will be date stamped and returned to the commenter. \n\nDiscussion of Comments Received to the NPRM \n\n\tInterested persons have been afforded an opportunity to participate in the making of a portion this amendment. Due consideration has been given to the comments received. \n\n\tOne commenter supports the proposal. \n\n\tSeveral commenters request that the proposed rule be revised to exclude the Models DC-10- 30 and -40 from the applicability until more information is gathered to substantiate that these airplanes are subject to the addressed unsafe condition. These commenters point out that cracks have been reported on Model DC-10-10 series airplanes only. One commenter states that the airframe manufacturer previously had requested that operators of Model DC-10 series airplanes inspect their airplanes for cracking and, as a result, none was found on any models other than the Model DC-10-10 and -15 series. Another commenter suggests that the spar cap and skin panel installed on Models DC-10-30 and -40 are thicker than those on Models DC-10-10 and -15; therefore, the possibility of these items cracking on the Model DC-10-30 and -40 airplanes is very low. \n\n\tThe FAA does not concur with these commenters' request. Although fatigue cracking may not have been detected on in-service Model DC-10-30 and -40 series airplanes, the airframe manufacturer has conducted load, fatigue, and damage-tolerance analyses, which indicate that fatigue-related cracking is likely to occur on all Model DC-10 series airplanes as these airplane accumulate flight cycles. The compliance thresholds specified in this AD, as well as the compliance times for the required initial and repetitive inspections, were developed in consideration of these analyses and with the participation of the airframe manufacturer. \n\n\tSeveral commenters request that the rule be revised to give credit for visual inspections of the area that were performed previously, and to add a visual inspection as an option for accomplishment of the initial eddy current inspection.These commenters state that a damage tolerance assessment conducted by the airframe manufacturer has shown that an initial visual inspection will ensure that the structural integrity of the horizontal stabilizer spar cap and skin is maintained. Additionally, by permitting a visual inspection to be performed, which takes less time and materials than an eddy current inspection, the economic impact of non-scheduled maintenance and removal of aircraft from service would be reduced for operators, as well as the corresponding inconvenience for the traveling public. \n\n\tThe FAA concurs with these commenters' request. Subsequent to the issuance of the notice, the FAA reviewed and approved Revision 1 to McDonnell Douglas DC-10 Service Bulletins 55-24 and 55-25, both dated August 3, 1994. These revised service bulletins contain revised instructions for accomplishing the eddy current inspection (to make it less complicated), and instructions for performing an optional visual inspection in lieu of the initial eddy current inspection to determine if cracks exist in the horizontal stabilizer forward cap and skin panel. The FAA has revised the final rule to permit operators to perform this optional visual inspection as the initial inspection only. All repetitive inspections must be performed using eddy current techniques. \n\n\tSeveral commenters request that the proposed rule be revised to eliminate the compliance time for the terminating modifications. These commenters consider that these modifications should be optional instead of mandatory. Other commenters indicate that fatigue-related cracks are cycle-dependent, not calendar time-dependent; therefore, it is inappropriate to impose a calendar time compliance time on a cycle-dependent phenomenon. The commenters also consider that the proposed compliance time of five years for installation of the terminating modifications could be unfair to operators of low-time airplanes, since, in some cases, an operator could be required to install the terminating modifications before the airplane has reached the threshold for the initial inspection. \n\n\tThe FAA does not concur with the commenters' request to allow the terminating action to be optional. The FAA has determined that long term continued operational safety will be better assured by design changes to remove the source of the problem, rather than by repetitive inspections. Long term inspections may not be providing the degree of safety assurance necessary for the transport airplane fleet. This, coupled with a better understanding of the human factors associated with numerous continual inspections, has led the FAA to consider placing less emphasis on inspections and more emphasis on design improvements. The modifications required by this AD are in consonance with these considerations. \n\n\tThe FAA does acknowledge, however, that the proposed compliance time for installation of the terminating modifications could present an unfair situation to operators of low-time airplanes. This was not the FAA's intent. Therefore, the FAA has revised paragraph (d) of the final rule to specify modification prior to the accumulation of a certain number of cycles (depending upon airplane model) or within 5 years, whichever occurs later. \n\n\tThe FAA has revised paragraphs (a)(1), (b)(1), and (c)(1) of the final rule to delete the previously proposed requirement to continue inspections after installation of a repair that has been approved by the Manager of the Los Angeles Aircraft Certification Office. The FAA has determined that deletion of this requirement is appropriate, since some repairs that have been approved have incorporated a terminating action, thereby eliminating the need for continuing repetitive inspections. \n\nCost Impact \n\n\tThere are approximately 427 Model DC-10-10, -15, -30, and -40 series airplanes and KC- 10A (military) airplanes of the affected design in the worldwide fleet. The FAA estimates that 241 airplanes of U.S. registry will be affected by this AD. \n\n\tThe accomplishment of the optional initial visual inspection will take approximately 1 work hour per airplane per inspection, at an average labor charge of $55 per work hour. Based on these figures, the total cost impact of this optional inspection on U.S. operators who elect to accomplish it is estimated to be $55 per airplane. \n\n\tThe accomplishment of the eddy current inspections will take approximately 3 work hours per airplane per inspection, at an average labor charge of $55 per work hour. Based on these figures, the total cost impact of the this inspection requirement on U.S. operators is estimated to be $39,765, or $165 per airplane, per inspection cycle. \n\n\tThe accomplishment of the modification of the forward spar upper cap will take approximately 248 work hours per airplane. Likewise, the accomplishment of the modification of the forward upper skin panel will take approximately 248 work hours per airplane. The average labor rate is $55 per work hour. Required parts will cost approximately $10,600 per airplane. Based on these figures, the total cost impact of the modification actions AD on U.S. operators is estimated to be $9,129,080, or $37,880 per airplane. \n\n\tThe FAA recognizes that the required modifications require a large number of work hours to accomplish. However, the 5-year compliance time specified in paragraph (d) of this proposed AD should allow ample time for the modifications to be accomplished coincidentally with scheduled major airplane inspection and maintenance activities, thereby minimizing the costs associated with special airplane scheduling. \n\n\tThe total 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\tThe FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, 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\n Adoption 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.\tThe authority citation for part 39 continues to read as follows:\n\n Authority: 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: