91-13-06 McDONNELL DOUGLAS: Amendment 39-7037. Docket No. 91-NM-03-AD. Supersedes AD 90-03-17. \n\n\tApplicability: Model DC-9 series, Model DC-9-80 series, C-9 (Military), and Model MD-88 airplanes, equipped with Westinghouse bus control unit (BCU) Part Number 947F946-2, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent the loss of generator electrical power, accomplish the following: \n\n\tA.\tWithin 30 days after February 15, 1990 (the effective date of AD 90-03-17, Amendment 39-6496), add the following to the LIMITATIONS section of the approved Airplane Flight Manual (AFM). This may be accomplished by inserting a copy of this AD into the AFM. \n\n\t\t1.\tOn takeoff with both engine generators and APU generator operating and APU bus switches selected to the ON position, the AC BUS X-TIE switch must be placed in the OPEN position. At or above 10,000 feet MSL with both engine generators operating, the APU may be shut down and the AC BUS X-TIE switch placed in the AUTO position. \n\n\t\tNOTE: In the event of an in-flight failure of an engine generator that results in the APU generator powering an AC bus, de-activate all galley power and place the other APU BUS switch in the ON position. \n\n\t\t2.\tOn takeoff with the APU generator inoperative, or an engine generator inoperative, dispatch is permitted in accordance with the present MMEL conditions except that the AC BUS X-TIE switch must be in the OPEN position. Verify that all transformer rectifiers (TR's) are operating and place the DC BUS X-TIE switch in the CLOSE position. Takeoff minimums are restricted to ceiling 1,000 foot and visibility 3 miles. The Captain must make the takeoff with his instrument incandescent flood lights adjusted to a level which would adequately compensate for the subsequent potential loss of his instrument integral lights. At or above 10,000 feet MSL, place the DC BUS X-TIE switch in the OPEN position and the AC BUSX-TIE switch in the AUTO position. \n\n\t\tNOTE: In the event of an in-flight failure of an engine generator following dispatching with the APU generator powering an AC bus, de-activate all galley power and place the other APU BUS switch in the ON position. \n\n\t\t3.\tWhen operating with the AC BUS X-TIE switch in the AUTO position, if rapid cycling of the AC cross-tie relay occurs, manifested by a buzzing/chattering sound from the electrical power center and any combination of random circuit breaker trips, inappropriate aural warning messages, loss of some flight instruments, and/or flashing cockpit annunciators, place the AC BUS X-TIE switch to the OPEN position. If a generator trips off-line, it may be reset only once. If the engine generator fault cannot be cleared, the APU should be utilized, if available. \n\n\t\t4.\tPrior to the approach with both engine generators operating, start the APU and place both APU BUS switches to the ON position. Place the AC BUS X-TIE switch to the OPENposition after APU electrical power becomes available. \n\n\t\t5.\tPrior to the approach with only two generators operating, place the AC BUS X-TIE switch in the OPEN position. Landing minimums are restricted to Category I and the Captain must make the approach with his instrument incandescent flood lights adjusted to a level which would adequately compensate for the subsequent potential loss of his instrument integral lights. \n\n\t\t6.\tIn the event of an in-flight failure that results in an AC bus not powered, place the DC BUS X-TIE switch in the CLOSE position. \n\n\t\t7.\tIn the event of an in-flight failure that results in both AC BUSES being powered by only one generator, the landing minimums are restricted to ceiling 1,000 feet and 3 miles visibility. The Captain must make the approach and landing. \n\n\t\t8.\tAutoland is permitted with two engine generators operating and APU generator operating with both APU BUS switches in the ON position and the AC BUS X-TIE switch in the OPEN position. Reconfirm APU generator availability after "AUT LND/AUT LND" is indicated on the Flight Mode Annunciator (FMA). An autoland approach must be discontinued following a failure of an engine generator. \n\n\tB.\tWithin 2 years after the effective date of this AD, replace the Westinghouse Bus Control Unit, Part Number 947F946-2 with the Westinghouse Bus Control Unit, Part Number 947F946-3, in accordance with McDonnell Douglas DC-9 Service Bulletin 24-119 dated January 24, 1990. The limitations on the electrical operating procedures and restricted operation of the automatic landing system required by paragraph A. of this AD may be removed from the AFM when the modified Westinghouse BCU is installed. \n\n\tC.\tAn alternate means of compliance and adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Los Angeles Aircraft Certification (ACO), FAA, Transport Airplane Directorate. \n\n\tNOTE: The request should be submitted directly to the Manager, Los Angeles ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Los Angeles 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 requirement 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 McDonnell Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Business Unit Manager, Technical Publications, C1-HCW (54-60). These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington, or the Los Angeles Aircraft Certification Office, 3229 East Spring Street, Long Beach, California. \n\n\tThis amendment supersedes Amendment 39-6496, AD 90-03-17. \n\n\tThis amendment(39-7037, AD 91-13-06) becomes effective on July 15, 1991.