90-20-19 MCDONNELL DOUGLAS: Amendment 39-6738. Docket No. 90-NM-50-AD. \n\n\tApplicability: All Model DC-10-40 series airplanes equipped with engines installed in accordance with Rohr STC SA3139WE, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent the loss of structural integrity of the Rohr Common Nacelle System (CNS) forward engine mount cross beam, accomplish the following: \n\n\tA.\tPrior to the accumulation of 10,000 cycles or within 1,500 cycles after the effective date of this amendment, whichever occurs later, inspect and rework the CNS forward engine mount cross beam, Rohr part number 196-0328-1 or 196-0328-501, and replace, as specified below, in accordance with Rohr Alert Service Bulletin No. MDC-CNS A71-33, Revision 1, dated April 27, 1988. \n\n\t\t1.\tIf no cracks are found and the hardness is equal to or greater than C40 on the Rockwell hardness scale, \n\n\t\t\ta.\tWithin 3,000 cycles after the initial inspection, and thereafter at intervals not to exceed 3,000 cycles, conduct repetitive magnetic particle inspections in accordance with Rohr Alert Service Bulletin MDC-CNS A71-33, Revision 1, dated April 27, 1988, and \n\n\t\t\tb.\tPrior to the accumulation of 35,000 cycles on the part, remove the CNS forward engine mount cross beam, Rohr part number 196-0328-1 or 196-0328-501, and replace it with Rohr part number 196-1300-501, in accordance with Rohr Service Bulletin No. MDC-CNS 71-33, dated July 25, 1988. \n\n\t\t2.\tIf a crack is found or the hardness is below C40 on the Rockwell hardness scale, prior to further flight, remove the CNS forward engine mount cross beam, Rohr part number 196-0328-1 or 196-0328-501, and replace it with Rohr part number 196-1300-501, in accordance with Rohr Service Bulletin No. MDC-CNS 71-33, dated July 25, 1988. \n\n\tB.\tThe CNS forward engine mount cross beam, Rohr part number 196-1300-501, is life limited and must be replaced prior to the accumulation of 46,667 cycles on the part. \n\n\tC.\tAn alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region. \n\n\t\tNOTE: The request should be submitted directly to the Manager, Los Angeles ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Los Angeles ACO. \n\n\tD.\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD. \n\n\tAll persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Rohr Industries, Inc., P. O. Box 878, Chula Vista, California 92012. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 LindAvenue S.W., Renton, Washington, or at the Los Angeles Aircraft Certification Office, 3229 East Spring Street, Long Beach, California. \n\n\tThis amendment (39-6738, AD 90-20-19) becomes effective on October 22, 1990.