59-16-05\tBOEING: Applies to 707-100 series aircraft with the following serial numbers: Model 707-121 serial numbers 17586 through 17591, Model 707-124 serial number 17609, Model 707-123 serial numbers 17628 through 17643, Model 707-131 serial numbers 17659 through 17672, Model VC-137A serial numbers 17925 through 17927. \n\tCompliance required not later than August 21, 1959. \n\tAs a result of complete loss of fluid during service operation of the utility hydraulic system, primarily due to failure of engine driven hydraulic pump the following must be accomplished: \n\t(a)\tInstall new pump, Vickers No. AS-61689-L-2E, in place of the AS-61689-L-2B or - 2C, or install pump external by-pass valve No. A-90073-Y6 with the -2B or -2C pump. If the pump external by-pass valve is installed the shaft seal on each hydraulic pump must be replaced at the same time. \n\t(b)\tInstall return line filter. \n\tBoeing Service Bulletin No. 379 and Vickers Service Letter dated June 17, 1959, pertain to item (a). Boeing Service Bulletins Nos. 69 and 213 pertain to item (b).