AD 95-22-06

This amendment adopts a new airworthiness directive (AD) that is applicable to certain McDonnell Douglas Model DC-9-80 series airplanes and Model MD-88 airplanes. This action requires repetitive inspections to detect fatigue cracking of the shock strut cylinder of the main landing gear (MLG), and replacement of any cracked shock strut cylinder with a serviceable part. This action also provides for installation of brake line hydraulic restrictors on the MLG brake systems, which, if accomplished, terminates the repetitive inspection requirement. This amendment is prompted by a report indicating that fatigue cracking and subsequent fracturing of the shock strut cylinder of the MLG occurred due to high stress loads on the cylinder as a result of braking induced vibration. The actions specified in this AD are intended to prevent such fracturing, which could result in collapse of the MLG and consequent reduced controllability of the airplane during landing.

Final rule; request for comments.

95-22-06 MCDONNELL DOUGLAS: Amendment 39-9413. Docket 95-NM-183-AD.\n\n\tApplicability: Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes, and Model MD-88 airplanes; as listed in McDonnell Douglas Alert Service Bulletin MD80-32A286, dated September 11, 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 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 use the authority provided in paragraph (e) of this AD to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition; or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any airplane from the applicability of this AD.\n\n\tCompliance: Required as indicated, unless accomplished previously.\n\n\tTo prevent collapse of the main landing gear (MLG) due to fracturing of the shock strut cylinder, accomplish the following:\n\n\t(a)\tFor airplanes on which brake line hydraulic restrictors have not been installed on the left and right MLG brake systems in accordance with McDonnell Douglas Alert Service Bulletin MD80-32A286, dated September 11, 1995, prior to the effective date of this AD: Within 90 days after the effective date of this AD, perform dye penetrant and magnetic particle inspections to detect cracking of the shock strut cylinder of the MLG, in accordance with McDonnell Douglas Alert Service Bulletin MD80-32A286, dated September 11, 1995.\n\n\t\t(1)\tIf no cracking is found, repeat the inspections thereafter at intervals not to exceed 1,200 landings.\n\n\t\t(2)\tIf any cracking is found, prior to further flight, replace the shock strut cylinder with a crack-free serviceable part in accordance with the alert service bulletin. After replacement, repeat the inspections at intervals not to exceed 1,200 landings.\n\n\t(b)\tFor airplanes on which brake line hydraulic restrictors have been installed on the left and right MLG brake systems in accordance with McDonnell Douglas Alert Service Bulletin MD80-32A286, dated September 11, 1995, prior to the effective date of this AD: Within 90 days after the effective date of this AD, perform dye penetrant and magnetic particle inspections to detect cracking of the shock strut cylinder of the MLG, in accordance with McDonnell Douglas Alert Service Bulletin MD80-32A286, dated September 11, 1995.\n\n\t\t(1)\tIf no cracking is found, no further action is required by this AD.\n\n\t\t(2)\tIf any cracking is found, prior to further flight, replace the shock strut cylinder with a crack-free serviceable part in accordance with the alert service bulletin. After the cylinder is replaced and the brake line hydraulic restrictors are reinstalled, no further action is required by this AD.\n\n\t(c)\tInstallation of brake line hydraulic restrictors on the left and right MLG brake systems, in accordance with McDonnell Douglas Alert Service Bulletin MD80-32A286, dated September 11, 1995, constitutes terminating action for the repetitive requirements of this AD only if it is accomplished prior to further flight after a dye penetrant and magnetic particle inspection is performed in accordance with this AD and no cracking is found during that inspection.\n\n\t(d)\tAs of the effective date of this AD, no person shall install on any airplane a MLG shock strut cylinder or MLG assembly unless that part has been inspected and found to be crack free, in accordance with McDonnell Douglas Alert Service Bulletin MD80-32A286,dated September 11, 1995.\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 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(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 initial inspection required by this AD can be accomplished. Such special flight permits may not be issued for airplanes on which cracking is found during an inspection required by this AD.(g)\tThe actions shall be done in accordance with McDonnell Douglas Alert Service Bulletin MD80-32A286, dated September 11, 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, 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(h)\tThis amendment becomes effective on November 8, 1995.

The FAA received a report indicating that the shock strut cylinder of the left main landing gear (MLG) fractured on a McDonnell Douglas Model DC-9-80 series airplane. The fractured MLG collapsed during landing rollout. The affected shock strut cylinder had accumulated 6,386 total landings and 18,236 total hours time-in-service. Investigation revealed that the fracturing was the result of fatigue cracking caused by high stress loads on the shock strut cylinder. These high stress loads were induced by vibration, which occurs during landing rollout when the aircraft is at speeds between 40 and 50 knots, with the anti-skid system on during moderate to heavy braking. Fatigue cracking and subsequent fracturing of the shock strut cylinder, if not corrected, could result in collapse of the MLG; such a collapse could adversely affect the controllability of the airplane during landing.\n\n\tThe FAA has reviewed and approved McDonnell Douglas Alert Service BulletinMD80-32A286, dated September 11, 1995, which describes procedures for repetitive dye penetrant and magnetic particle inspections to detect cracking of the shock strut cylinder of the MLG, and replacement of any cracked shock strut cylinder with a serviceable part. The alert service bulletin also describes procedures for installation of brake line hydraulic restrictors on the left and right MLG brake systems, which eliminates the need for the repetitive inspections. Accomplishment of the installation will minimize stress loads induced by vibration and the possibility of fatigue cracking of the shock strut cylinder.\n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other Model DC-9-80 series airplanes and Model MD-88 airplanes of the same type design, this AD is being issued to prevent fracturing of the shock strut cylinder of the MLG, which could result in collapse of the MLG and consequent reduced controllability of the airplane during landing.This AD requires repetitive dye penetrant and magnetic particle inspections to detect cracking of the shock strut cylinder of the MLG, and replacement of any cracked shock strut cylinder with a crack-free serviceable part. This AD also provides for the installation of brake line hydraulic restrictors on the left and right MLG brake systems, which terminates the repetitive inspection requirement if it is accomplished prior to further flight after inspections are performed and no cracking is found. However, all airplanes, including those on which brake line hydraulic restrictors have been installed previously, are required to perform the inspections at least one time. The actions are required to be accomplished in accordance with the alert service bulletin described previously.\n\n\tOperators should note that, McDonnell Douglas Alert Service Bulletin MD80-32A286, dated September 11, 1995, recommends that the accomplishment of the inspections be completed within 6 months (from the issue date of the service bulletin). While the FAA agrees that 6 months is an appropriate time interval in which the inspections can be accomplished and an adequate level of safety maintained, this AD specifies a compliance time of 90 days for the accomplishment of the inspections. This 90-day compliance time was developed by taking into account the manufacturer's recommended 6-month time interval from September 11, 1995 (the service bulletin issue date), as well as the number of days that are normally required for the rulemaking process to be completed (approximately 90 days). In consideration of both of these factors, the FAA finds that a compliance time of 90 days after the effective date of this final rule will fall approximately at the same time (calendar date) for compliance that has been recommended by the manufacturer. By adjusting the compliance time interval in this way:\n\n\t1.\toperators will be provided, in effect, with a full 6 months in which to complete the inspections;2.\tthe inspections can be accomplished within an interval of time that parallels normal scheduled maintenance for a majority of affected operators; and\n\n\t3.\tthe inspections will be accomplished within an appropriate interval to prevent the initiation and propagation of fatigue cracking in the shock strut cylinder.\n\n\tIn addition, the McDonnell Douglas service bulletin recommends that the installation of brake line hydraulic restrictors be accomplished within 12 months. However, this AD does not require such installation at a specified time; it is provided in this AD as an optional terminating action. The FAA may consider additional rulemaking to require accomplishment of the installation, but has determined that the repetitive inspections will maintain an adequate level of safety in the fleet in the meantime.\n\n\tSince a situation exists that requires the immediate adoption of this regulation, 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\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 light of 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 95-NM-183-AD." The postcard will be date stamped and returned to the commenter.\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\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.\n\nAdoption of the Amendment\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\t1. The authority citation for part 39 continues to read as follows:\nAuthority: 49 USC 106(g), 40101, 40113, 44701.\n\n§ 39.13 - (Amended)\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: