AD 97-02-10

This amendment adopts a new airworthiness directive (AD) that is applicable to certain McDonnell Douglas Model DC-9, DC-9-80, and C-9 (military) series airplanes, Model MD- 88 airplanes, and Model MD-90 airplanes. This action requires a visual check to determine the part and serial numbers of the upper lock link assembly of the nose landing gear (NLG); repetitive inspections of certain upper lock link assemblies to detect fatigue cracking; and modification of the NLG. This action also provides for terminating action for the repetitive inspections. This amendment is prompted by a report indicating that, due to fatigue cracking, the upper lock link assembly on an airplane fractured, and consequently prevented the NLG from extending fully. The actions specified in this AD are intended to prevent this assembly from fracturing due to fatigue cracking, and the NLG consequently failing to extend fully; this condition could result in injury to passengers and flight crew, and damage to the airplane.

Final rule; request for comments.

97-02-10 MCDONNELL DOUGLAS: Amendment 39-9895. Docket 97-NM-01-AD. \n\n\tApplicability: Model DC-9, DC-9-80, and C-9 (military) series airplanes, Model MD-88 airplanes, and Model MD-90 airplanes; as listed in McDonnell Douglas Alert Service Bulletins DC9-32A298 (for Model DC-9, DC-9-80, and C-9 (military) series airplanes, and Model MD-88 airplanes), and McDonnell Douglas Alert Service Bulletin MD90-32A019 (for Model MD-90 airplanes), both dated December 19, 1996; 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 otherwise 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 (e) 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 fracturing of the upper lock link assembly of the nose landing gear (NLG) due to fatigue cracking, and the consequent failure of the NLG to extend fully, which could lead to injury to passengers and flight crew, and damage to the airplane, accomplish the following: \n\n\t(a)\tPrior to the accumulation of 10,000 total cycles of the NLG, or within 90 days after the effective date of this AD, whichever occurs later, conduct a visual check of the upper lock link assembly of the NLG to determine its part and serial number, in accordance with McDonnell Douglas Alert Service Bulletin DC9-32A298 (for Model DC-9, DC-9-80, and C-9 (military) series airplanes, and Model MD-88 airplanes), or McDonnell Douglas Alert Service Bulletin MD90-32A019 (for Model MD-90 airplanes), both dated December 19, 1996, as applicable. \n\n\t(b)\tIf the part number and serial number of the upper lock link assembly are listed in paragraph (b)(1) or (b)(2) of this AD ("an exempt upper lock link assembly"), no further action is required. \n\n\tNOTE 2: An "exempt upper lock link assembly" as specified in paragraph (b) of this AD is an assembly that is manufactured of forged aluminum. \n\n\t\t(1)\tFor Model DC-9, DC-9-80, and C-9 (military) series airplanes, and Model MD-88 airplanes: Part Number (P/N) 3914464-(any configuration) having serial numbers (S/N) HMI001 through HMI172 inclusive, or S/N WPI1000 and subsequent; or P/N 5920472-(any configuration) having any serial number. \n\n\t\t(2)\tFor Model MD-90 airplanes: P/N 3914464-503 having S/N HMI001 through HMI172 inclusive, or S/N WPI1000 and subsequent. \n\n\t(c)\tIf the part number and serial number of the upper lock link assembly are not listed in paragraph (b)(1) or (b)(2) of this AD ( a "possible discrepant upper lock link assembly"), except as provided by paragraph (c)(3) of this AD, prior to further flight, conduct either a high frequency eddy current inspection or a Type I fluorescent penetrant inspection of this assembly to detect fatigue cracks, in accordance with McDonnell Douglas Alert Service Bulletin DC9-32A298 (for Model DC-9, DC-9-80, and C-9 (military) series airplanes, and Model MD-88 airplanes), or McDonnell Douglas Alert Service Bulletin MD90-32A019 (for Model MD-90 airplanes), both dated December 19, 1996. \n\n\tNOTE 3: A "possible discrepant upper lock link assembly" as specified in paragraph (c) of this AD is an assembly that may be manufactured from aluminum plate. \n\n\t\t(1)\tIf no crack is detected, repeat either type of inspection required by paragraph (c) of this AD at intervals not to exceed 5,000 cycles of the NLG. \n\n\t\t(2)\tIf any crack is detected, prior to further flight,replace the pin assembly of the NLG in accordance with the applicable alert service bulletin. \n\n\t\t(3)\tA Type I fluorescent penetrant inspection of the upper lock link assembly that has been conducted within the last 12 months prior to the effective date of this AD and in accordance with the DC-9 Overhaul Manual or MD-90 Component Manual, Chapter 20-70-2, is considered acceptable for compliance with the initial inspection required by paragraph (c) of this AD. If no crack was detected during that inspection, subsequent repetitive inspections are required to be accomplished at the intervals specified in paragraph (c)(1) of this AD. \n\n\t(d)\tWhen replacement of the pin assembly of the NLG is required in accordance with paragraph (c)(1) or (c)(2) of this AD: \n\n\t\t(1)\tIf the pin assembly is replaced with a new assembly that contains a possible discrepant upper lock assembly: After the pin assembly has been replaced, repeat the inspection required by paragraph (c) of this AD prior to theaccumulation of 10,000 cycles of the NLG. \n\n\t\t(2)\tIf the pin assembly is replaced with a serviceable assembly that contains a possible discrepant upper lock assembly: After the pin assembly has been replaced, repeat the inspection required by paragraph (c) of this AD either prior to the accumulation of 10,000 total cycles of the NLG for that pin assembly, or prior to further flight, whichever occurs later. \n\n\t\t(3)\tIf the pin assembly is replaced with a pin assembly that contains an exempt upper lock link assembly: No further action is required. This installation constitutes terminating action for the repetitive inspections required by this AD. \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 MaintenanceInspector, who may add comments and then send it to the Manager, Los Angeles ACO. \n\n\tNOTE 4: 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 visual check, repetitive inspections, and replacement of the pin assembly of the NLG shall be done in accordance with McDonnell Douglas Alert Service Bulletin DC9-32A298, dated December 19, 1996; or McDonnell Douglas Alert Service Bulletin MD90-32A019, dated December 19, 1996; as applicable. 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 February 11, 1997.

The FAA has recently received a report indicating that the upper lock link assembly of the nose landing gear (NLG) on a McDonnell Douglas DC-9-80 series airplane failed prior to landing. As a result of this failure, the airplane sustained moderate damage to the forward lower fuselage. \n\n\tAn investigation by the operator revealed that this assembly had fractured and jammed against the shock strut, which prevented the NLG from extending fully. This fracture was caused by fatigue cracking that originated at the lower end of the assembly where the flange and inner radius meet. The operator also detected similar fatigue cracking in two other upper lock link assemblies during an inspection of other airplanes in its fleet. \n\n\tAn upper lock link assembly can be either manufactured from aluminum plate or forged from aluminum. The three cracked assemblies that were detected were aluminum plate, a material which has a much shorter fatigue life than forged aluminum. In addition to Model DC-9- 80 series airplanes, assemblies of aluminum plate may be installed on Model DC-9 and C-9 (military) series airplanes, Model MD-88 airplanes, and Model MD-90 airplanes. \n\n\tFracturing of the upper lock link assembly due to fatigue cracking, if not corrected, can result in the failure of the NLG to extend fully, which could lead to injury to passengers and flight crew, and damage to the airplane. \n\nExplanation of Relevant Service Information \n\n\tThe FAA has reviewed and approved McDonnell Douglas Alert Service Bulletin DC9-32A298 (for Model DC-9, DC-9-80, and C-9 (military) series airplanes, and Model MD-88 airplanes), and McDonnell Douglas Alert Service Bulletin MD90-32A019 (for Model MD-90 airplanes), both dated December 19, 1996. Both alert service bulletins describe procedures for conducting a visual check of the part number and serial number on the upper lock link assembly of the NLG to identify whether an assembly has been forged from aluminum(an "exempt upper lock link assembly"), or has been manufactured from aluminum plate (a "possible discrepant upper lock link assembly"). No further action is necessary if an exempt upper lock link assembly is installed. \n\n\tBoth alert service documents also describe procedures for conducting repetitive high frequency eddy current inspections or Type I fluorescent penetrant inspections to detect fatigue cracking in a possible discrepant upper lock link assembly. When fatigue cracking is detected in this upper lock link assembly or when the assembly's safe life (46,500 cycles of the NLG) has been reached, the pin assembly of the NLG is to be replaced with a new or serviceable pin assembly. (The upper lock link assembly is contained within the pin assembly.) If the pin assembly is replaced with one that contains an exempt upper lock link assembly, the need for subsequent repetitive inspections and replacement of parts is eliminated. \n\nExplanation of the Requirements of the RuleSince an unsafe condition has been identified that is likely to exist or develop on other McDonnell Douglas Model DC-9, DC-9-80, and C-9 (military) series airplanes, Model MD-88 airplanes, and Model MD-90 airplanes, of the same type design, this AD is being issued to prevent fracturing of the upper lock link assembly due to fatigue cracking, and the consequent failure of the NLG to extend fully, which could lead to injury to passengers and flight crew, and damage to the airplane. \n\n\tThis AD requires a visual check of the part number and serial number on the upper lock link assembly to identify whether this assembly is a possible discrepant assembly or an exempt assembly. (No further action is required if an upper lock link assembly is an exempt assembly.) \n\n\tThis AD also requires repetitive high frequency eddy current inspections or Type I fluorescent penetrant inspections of any possible discrepant upper lock link assembly to detect fatigue cracking. When fatigue cracking is detected in the upper lock link assembly, this AD requires that the pin assembly of the NLG be replaced with a new or serviceable pin assembly. The operator, at its option, may install a replacement pin assembly that contains an exempt, rather than a possible discrepant, upper lock link; this substitution terminates the requirement for repetitive inspections. \n\n\tThe actions are required to be accomplished in accordance with the applicable alert service bulletin described previously. \n\nInterim Action \n\n\tThis is considered to be interim action. The manufacturer has advised that it currently is developing a modification that will positively address the unsafe condition addressed by this AD. Once this modification is developed, approved, and available, the FAA may consider additional rulemaking. \n\nDetermination of Rule's Effective Date \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\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.Comments 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 97-NM-01-AD." The postcard will be date stamped and returned to the commenter. \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 variouslevels 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\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: