92-02-12 BOEING: Amendment 39-8148. Docket No. 91-NM-142-AD. \n\n\tApplicability: Model 767 series airplanes, listed in Boeing Alert Service Bulletin 767- 21A0098, dated May 9, 1991, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent halon from escaping through the bulk cargo ventilation flapper valve when the fire extinguishing system is activated, accomplish the following: \n\n\t(a)\tWithin 4,000 flight hours after the effective date of this AD, remove the bulk cargo ventilation flapper valve in accordance with Boeing Alert Service Bulletin 767-21A0098, dated May 9, 1991. \n\n\t(b)\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. \n\n\tNOTE: The request should be forwarded through an FAA Principal Maintenance Inspector, whomay concur or comment and then send it to the Manager, Seattle ACO. \n\n\t(c)\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\t(d)\tThe removal requirements of this AD shall be done in accordance with Boeing Alert Service Bulletin 767-21A0098, dated May 9, 1991. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. Copies may be inspected at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington, or at the Office of the Federal Register, 1100 L Street N.W., Room 8401, Washington, D.C. \n\n\t(e)\tThis amendment (39-8148, AD 92-02-12) becomes effective on March 2, 1992.