84-26-01 McDONNELL DOUGLAS: Amendment 39-4971. Applies to McDonnell Douglas Model DC-9-10, -20, -30, -40, -50, C-9 (Military) series airplanes, certificated in all categories, which have accomplished Option I of McDonnell Douglas DC-9 Service Bulletin 57-125, Revision 2, or prior issues and have installed MLG attach fitting fabricated from forging alloy 7075-T73. \n\n\tSpecific corresponding factory serial numbers for the production effectivity are listed in McDonnell Douglas DC-9 Service Bulletin 57-148, Revision 1, dated June 8, 1983, hereinafter referred to as SB 57-148, R1. Compliance is required as indicated, unless previously accomplished. To detect cracks and prevent failure of the MLG attach fitting and its interrelated structure, accomplish the following: \n\n\tA.\tFor aircraft with fittings having 15,000 to 19,999 landings, inspect the affected MLG attach fittings for cracks within 3,600 additional landings in accordance with SB 57-148, R1. \n\n\tB.\tFor aircraft with fittings having 20,000 or more landings, inspect the affected MLG attach fittings for cracks within 1,800 additional landings, in accordance with SB 57-148, R1. \n\n\tC.\tRepetitive inspections must be performed at 3,600 landings intervals until replaced with a new fitting or preventative modification is accomplished in accordance with SB 57-148, R1. \n\n\tD.\tIf an MLG attach fitting is found cracked, the affected MLG attach fitting(s) must be reworked in accordance with SB 57-148, R1, or later FAA approved revisions, prior to further flight. \n\n\tE.\tIf cracks are found in locations in the fitting(s) other than those identified in SB 57-148, R1, replace the fitting(s) before further flight in accordance with SB 57-125, R4, Option 1, or rework in a manner approved by the Manager, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region. \n\n\tF.\tIf preventative modification is not accomplished prior to 37,000 landings, continue repetitive inspections at 3,600 landing intervals, until such time terminating action is accomplished. \n\n\tG.\tCompletion of the preventative modification in accordance with SB 57-148, R1, or the replacement of cracked fitting(s) in accordance with SB 57-125, R4, or later FAA approved revisions, constitutes terminating action for this AD. \n\n\tH.\tAlternative inspections, modifications, or other actions which provide an equivalent level of safety may be used when approved by the Manager, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region. \n\n\tI.\tUpon request of operator, an FAA Maintenance Inspector, subject to prior approval of the Manager, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region, may adjust the repetitive inspection intervals specified in this AD to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for that operator. \n\n\tAll persons affected by this directive who have not already received these documents from the manufacturer may obtain copies upon request to McDonnell Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Director, Publications and Training, C1-750 (54-60). These documents also may be examined at the FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or the Los Angeles Aircraft Certification Office, 4344 Donald Douglas Drive, Long Beach, California. \n\n\tThis amendment becomes effective January 27, 1985.