78-20-10 MCDONNELL DOUGLAS: Amendment 39-3310. Applies to DC-10-10, -10F, -30, -30F, and -40 airplanes certificated in all categories.\n\n\tCompliance required within the next 1800 hours time in service after the effective date of this AD, unless already accomplished. \n\n\tTo prevent the loss of related powered flight controls due to loss of fluid through brake return line failure accomplish the following:\n\n\t(a)\tRevise hydraulic system 1 and 3 by installing three check valves and, when applicable, new hydraulic piping, in accordance with McDonnell Douglas DC-10 Service Bulletin No. A29-113, Revision 2, dated April 4, 1978.\n\n\tNOTE: Service Bulletin A29-113, Revision 2, dated April 4, 1978, is the only version of this service bulletin suitable for compliance with paragraph (a) of this AD.\n\n\t(b)\tEquivalent modifications may be used when approved by the Chief, Aircraft Engineering Division, FAA Western Region.\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 for the accomplishment of the inspections required by this AD.\n\n\tThis amendment becomes effective December 6, 1978.