91-07-01 BOEING: Amendment 39-6945. Docket No. 91-NM-45-AD. \n\n\tApplicability: Model 737 series airplanes, line numbers 1975 through 1989; and Model 757 series airplanes, line numbers 338 through 343; equipped with an Electronic Flight Instrument System (EFIS) using symbol generators, part number S242T404-420; certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent blanking of either pilot's EFIS display and loss of one pilot's primary flight instruments, accomplish the following: \n\n\tA.\tWithin 10 days after the effective date of this AD, inspect the EFIS symbol generators installed on the airplane and record the modification status. EFIS symbol generators which do not have Modification 3 implemented, must be removed and modified in accordance with Collins Service Bulletin EFIP-701E-34-03, dated February 1, 1991, prior to further flight. \n\n\tB.\tAny EFIS Symbol Generators with part number S242T404-420 which do nothave Modification 3 implemented, must be modified in accordance with Collins Service Bulletin EFIP-701E-34-03, dated February 1, 1991, before installation on an airplane. \n\n\tC.\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 Avionics Inspector, who may concur or comment and then send it to the Manager, Seattle 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 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 (39-6945, AD 91-07-01) becomes effective on April 3, 1991.