90-24-09 BOEING: Amendment 39-6815. Docket No. 90-NM-231-AD. \n\n\tApplicability: Model 747 series airplanes, listed in Boeing Service Bulletin 747-57- 2231, Revision 2, dated September 27, 1990, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\tTo prevent failure of the flap tracks, accomplish the following: \n\n\tA.\tVisually inspect the forward end clevis lugs of flap tracks for evidence of cracking, in accordance with Boeing Service Bulletin 747-57-2231, Revision 2, dated September 27, 1990, and in accordance with the following schedule: \n\n\t\t1.\tFor Group 1 airplanes: Perform the inspection at flap track positions 1 through 8 within the next 30 days after the effective date of this AD. \n\n\t\t2.\tFor Group 2 airplanes: Perform inspection at flap track positions 1, 2, 7, and 8 prior to the later of the following: \n\n\t\t\ta.\tPrior to the accumulation of 30,000 flight hours or 8 years after airplane delivery, whichever occursfirst; or \n\n\t\t\tb.\tWithin 120 days after the effective date of this AD. \n\n\t\t3.\tFor Group 3 airplanes: Perform the inspection at flap track positions 1 through 8 prior to the later of the following: \n\n\t\t\ta.\tPrior to the accumulation of 30,000 flight hours or 8 years after airplane delivery, whichever occurs first; or \n\n\t\t\tb.\tWithin 120 days after the effective date of this AD. \n\n\tB.\tIf cracking is found, replace the flap track prior to further flight, in accordance with Boeing Service Bulletin 747-57-2231, Revision 2, dated September 27, 1990. \n\n\tC.\tIf no cracking is found, repeat the inspection required by paragraph A. of this AD, at intervals not to exceed 300 flight cycles for Group 1 airplanes, and 1,200 flight cycles for Group 2 and Group 3 airplanes. \n\n\tD.\tAccomplishment of the modification of the forward end clevis lugs of flap tracks as specified in Boeing Service Bulletin 747-57-2231, Revision 2, dated September 27, 1990, constitutes terminating action for the inspections required by paragraphs A. and C. of this AD. \n\n\tE.\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\tF.\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 information from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington. \n\n\tThis amendment (39-6815, AD 90-24-09) becomes effective on December 5, 1990.