91-10-09 BOEING: Amendment 39-6993. Docket No. 90-NM-238-AD. \n\n\tApplicability: Model 767 series airplanes, line number 300 through 307, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent structural failure of the vertical stabilizer from overpressurization in the event of a rupture of the fuselage under the dorsal fin, accomplish the following: \n\n\tA.\tWithin the next 18 months after the effective date of this amendment, install a cover plate and a panel assembly over the lightening and access holes in the vertical stabilizer forward closure rib, in accordance with Boeing Alert Service Bulletin 767-55A0007, dated June 22, 1989, or Revision 1, dated May 24, 1990. \n\n\tB.\tAn alternative method 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.NOTE: The request should be forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Seattle ACO. \n\n\tC.\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 Avenue S.W., Renton, Washington. \n\n\tThis amendment (39-6993, AD 91-10-09) becomes effective on June 17, 1991.