90-25-10 BOEING: Amendment 39-6822. Docket No. 90-NM-145-AD. \n\n\tApplicability: Model 747 series airplanes, line numbers 001 through 635, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent loss of redundancy in the elevator control, accomplish the following: \n\n\tA.\tFor airplanes identified as Group 1 in Boeing Alert Service Bulletin 747-27A2253, Revision 4, dated January 25, 1990, accomplish the following inspections, in accordance with the service bulletin: \n\n\t\t1.\tPrior to the accumulation of 6 years time-in-service, or within the next 6 months after the effective date of this AD, whichever occurs later, visually inspect the inboard elevator power control package (PCP) input rods, inboard elevator control rods, and elevator aft quadrant for corrosion, cracking, and deformation; and repeat thereafter at intervals not to exceed 15 months. \n\n\t\t2.\tWithin 15 months after the visual inspection required by paragraph A.1. of this AD, internally borescope inspect the inboard elevator PCP input rods, inboard elevator control rods, and elevator aft quadrant tube for corrosion, cracking, and deformation; and repeat thereafter at intervals not to exceed 30 months. \n\n\tB.\tFor airplanes identified as Group 2 in Boeing Alert Service Bulletin 747-27A2253, Revision 4, dated January 25, 1990, accomplish the following inspections in accordance with the service bulletin: \n\n\t\t1.\tPrior to the accumulation of 6 total years time-in-service, or within the next 6 months after the effective date of this AD, whichever occurs later, visually inspect the inboard elevator control rods and elevator aft quadrant for corrosion, cracking, and deformation; and repeat thereafter at intervals not to exceed 15 months. \n\n\t\t2.\tWithin 15 months after the visual inspection required by paragraph B.1. of this AD, internally borescope inspect the inboard elevator control rods and elevator aft quadrant tube for corrosion, cracking, and deformation; and repeat thereafter at intervals not to exceed 30 months. \n\n\tC.\tFor airplanes identified as Group 3 in Boeing Alert Service Bulletin 747-27A2253, Revision 4, dated January 25, 1990, accomplish the following inspections in accordance with the service bulletin: \n\n\t\t1.\tPrior to the accumulation of 6 total years time-in-service, or within the next 6 months after the effective date of this AD, whichever occurs later, visually inspect the elevator aft quadrant for corrosion, cracking, and deformation; and repeat thereafter at intervals not to exceed 15 months. \n\n\t\t2.\tWithin 15 months after the visual inspection required by paragraph C.1. of this AD, internally borescope inspect the elevator aft quadrant tube for corrosion, cracking, and deformation; and repeat thereafter at intervals not to exceed 30 months. \n\n\tD.\tIf corrosion is found as a result of the inspections required by paragraphs A., B., or C. of this AD, prior to further flight, accomplish the following: \n\n\t\t1.\tIf corrosion is found to be in excess of the allowable limits specified in Boeing Alert Service Bulletin 747-27A2253, Revision 4, dated January 25, 1990, accomplish the terminating modification for the affected component specified in paragraph F. of this AD. \n\n\t\t2.\tIf corrosion is found to be within the allowable limits specified in Boeing Alert Service Bulletin 747-27A2253, Revision 4, dated January 25, 1990, refinish in accordance with the service bulletin. \n\n\tE.\tIf cracks or deformations are found as a result of the inspections required by paragraphs A., B., or C., of this AD, prior to further flight, accomplish the terminating modification for the affected component defined in paragraph F. of this AD. \n\n\tF.\tAccomplishment of the terminating modification for all affected components, as specified in Boeing Alert Service Bulletin 747-27A2253, Revision 4, dated January 25, 1990, constitutes termination for the inspections required by paragraphs A., B., and C. of thisAD. \n\n\tG.\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, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\tNOTE: The request should be submitted directly to the Manager, Seattle ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Seattle ACO. \n\n\tH.\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 Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind AvenueS.W., Renton, Washington. \n\n\tAirworthiness Directive 90-25-10 supersedes AD 85-13-01, Amendment 39-5084. \n\tThis amendment (39-6822, AD 90-25-10) becomes effective on January 7, 1991.