AD 99-04-06

This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model MD-90-30 series airplanes, that requires modification of the right and left main landing gear (MLG) hydraulic damper assemblies or replacement of the MLG hydraulic damper assemblies with modified and re-identified hydraulic damper assemblies. This amendment is prompted by reports indicating that, during overhauls, the MLG hydraulic dampers assemblies failed or had damaged spring retainers due to insufficient material thickness of the spring retainers. The actions specified by this AD are intended to prevent failure of the hydraulic damper assemblies of the MLG, which could result in vibration damage and collapse of the MLG.

Final rule.

99-04-06 MCDONNELL DOUGLAS: Amendment 39-11030. Docket 98-NM-269-AD. \n\n\tApplicability: Model MD-90-30 series airplanes, as listed in McDonnell Douglas Service Bulletin MD90-32-032, dated July 8, 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 failure of the hydraulic damper assemblies of the main landing gear (MLG), which could result in vibration damage and collapse of the MLG, accomplish the following: \n\n\t(a)\tWithin 2 years after the effective date of this AD, accomplish the requirements specified in either paragraph (a)(1) or (a)(2) of this AD. \n\n\t\t(1)\tModify the right and left MLG hydraulic damper assemblies in accordance with McDonnell Douglas Service Bulletin MD90-32-032, dated July 8, 1998; or \n\n\t\t(2)\tReplace the right and left MLG hydraulic damper assemblies with modified and re-identified hydraulic damper assemblies having part number (P/N) SR09320057-7005, SR09320057-7007, SR09320057-7009, or 5923142-5513, in accordance with paragraph B.5. of the Accomplishment Instructions of the service bulletin. \n\n\t(b)\tAs of the effective date of this AD, no person shall install on any airplane a damper sub assembly having P/N SR09320057-9, SR09320057-17, or 5923142-5017; or a damper assembly having P/N SR09320057-7001, SR09320057-7003, or 5923142-5511, unless the part is modified in accordance with paragraph (a)(1) of 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 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 modification and replacement shall be done in accordance with McDonnell Douglas Service Bulletin MD90-32-032, dated July 8, 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 Boeing Commercial Aircraft Group, Long Beach 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 March 17, 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 MD-90-30 series airplanes was published in the Federal Register on October 21, 1998 (63 FR 56125). That action proposed to require modification of the right and left main landing gear (MLG) hydraulic damper assemblies or replacement of the MLG hydraulic damper assemblies with modified and re-identified hydraulic damper assemblies. \n\nComments \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the two comments received. \n\n\tOne commenter supports the proposed rule. \n\nComment Concerning Availability of Parts \n\n\tOne commenter states no objection to the proposed rule, however, the commenter questions whether parts will be available within the proposed compliance time. The FAA has consulted with the manufacturer, and finds that parts will be available within the required compliance time. \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 111 airplanes of the affected design in the worldwide fleet. The FAA estimates that 40 airplanes of U.S. registry will be affected by this AD. \n\n\tIt will take approximately 18 work hours per airplane (including access, removal, and close-up) to accomplish the required modification, at an average labor rate of $60 per work hour. Required parts will cost approximately $598 per airplane. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $1,678 per airplane. \n\n\tIt will take approximately 5 work hours per airplane to accomplish the required replacement at an average labor rate of $60 per work hour.Based on these figures, the cost impact of the replacement required by this AD on U.S. operators is estimated to be $300 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: