91-21-02 MCDONNELL DOUGLAS: Amendment 39-8049. Docket No. 91-NM-187-AD. \n\n\tApplicability: Model DC-9-80 series airplanes; equipped with Sundstrand Data Control management control units (MCU), part number (P/N) 960-0511-001, -002, or -003; certificated in any category. \n\n\tCompliance: Required within 15 days after the effective date of this AD, unless previously accomplished. \n\n\tTo prevent in-flight electrical shorting of the MCU that could cause the MCU battery to burst and blow the MCU case open and damage other aircraft systems in the electrical and electronics compartment, accomplish the following: \n\n\t(a)\tRemove Sundstrand MCU, P/N 960-0511-001, -002, or -003, in accordance with McDonnell Douglas Alert Service Bulletin A31-39, dated August 15, 1991 (telex), or August 19, 1991 (service bulletin). \n\n\tNOTE: In accordance with Federal Aviation Regulation (FAR) 121.367, any operator who currently uses the MCU specified in paragraph (a) of this AD to record maintenance data required by its FAA-approved maintenance program must obtain approval from its FAA Principal Maintenance Inspector for an alternative method of recording this data. \n\n\tNOTE: MCU's specified in paragraph (a) of this AD may be replaced with an FAA-approved Sundstrand MCU, P/N 960-0511-011. \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, Los Angeles 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, Los Angeles 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 shall be done in accordance with McDonnell Douglas Alert Service Bulletin A31-39, which was released as a telex dated August 15, 1991, and as a paper copy service bulletin dated August 19, 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 McDonnell Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 90846. Copies may be inspected at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington; or at the Los Angeles Aircraft Certification Office, 3229 East Spring Street, Long Beach, California; or at the Office of the Federal Register, 1100 L Street N.W., Room 8401, Washington, D.C. \n\n\tThis amendment (39-8049, AD 91-21-02) becomes effective on October 23, 1991.