THE USAF KC-135 WAS ON AN IFR FLT PLAN & EXECUTING A TACAN 3L APCH TO LUKE AFB. THE AA-1 HAD DEPARTED SKY HARBOUR ARPT &HAD BEEN RELEASED BY PHOENIX TRSA. THE AA-1 WAS HEADING WESTERLY IN AIRSPACE DESIGNATED AS A SPECIAL TRAFFIC AREA & WAS REQUIRED TO HAVE BEEN AT OR BELOW 2,000 FT MSL. A PLT OF ANOTHER ACFT WHO WAS TRAILING THE AA-1 STATED THAT A LOW BROKENCLOUD COVER WAS ENCOUNTERED & HE HAD TO DESCEND TO ABOUT 2,000 FT TO REMAIN 500 FT BELOW THE BASES. HE STATED THE PLT OFTHE AA-1 DID NOT DESCEND BUT APPEARED TO BE SKIMMING ALONG IN & OUT OF THE BASES OF THE CLOUDS. HE NOTICED THE KC-135 DESCENDING THROUGH THE CLOUD DECK FOLLOWED IMMEDIATELY BY THE COLLISION. THE COLLISION OCCURRED ABOUT 5 MI SOUTH OF LUKE AFB AT AN ALTITUDE OF 2,500 FT MSL. THE LOGBOOK OF THE AA-1 PLT INDICATES THIS WAS HIS FIRST TRIP TO THE PHOENIX AREA. LUKE AFB WAS DEPICTED ON THE NORTH SIDE OF THE SECTIONAL CHART ONLY. VOR AIRWAY #16 WAS SPLIT ALONG AN E-W LINE WITH THE NORTHERN & SOUTHERN HALVES BEING DEPICTED ON EACH SIDE OF THE CHART.