AN ACR MLG WAS REDUCING AIRSPD WHILE DSNDING THROUGH 10600 FT. A MIL S3; INSIDE THE CLASS B AIRSPACE WITHOUT CLRNC PASSED 100 FT DIRECTLY UNDER THEM FROM L TO R AFTER MLG TOOK EVASIVE ACTION CLB. THERE WAS NO TCASII WARNING SUGGESTING THAT THE MIL ACFT DID NOT HAVE THEIR MODE C OPERATING.

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WE WERE CLRED TO FLY A 220 DEG HDG TO INTERCEPT THE LOC FOR RWY 27 AT LINDBERGH FIELD AND TO DSND DOWN TO 8000 FT. I WAS FLYING AND THE CAPT WAS WORKING THE RADIO. AS WE DSNDED PAST 11000 FT; I STARTED EASING BACK ON THE CTL COLUMN TO SLOW TO 250 KTS AT 10000 FT. WE WERE PASSING THROUGH 10800 FT WHEN APCH CTL SAID WE HAD TFC AT 10 O'CLOCK -- ALT UNKNOWN. THE CAPT LOOKED OUT HIS WINDOW FOR THE TFC AND NOTICED AN S3 VIKING MIL JET APCHING FROM OUR 8:30-9 O'CLOCK POS AT ABOUT OUR ALT ON A WESTERLY HEADING. THE CAPT QUICKLY PULLED UP ON THE CTL COLUMN TO AVOID HITTING THE S3. HE TURNED HIS HEAD TO THE R WHICH MADE ME LOOK OUT OF MY WINDOW ON THE R (R-2) AND THE WINDOW WAS FULL OF THE MIL S3. HE APPEARED TO BE LESS THAN 100 FT BELOW US. WE HAD NO WARNING ON OUR TCASII PROVING THAT HE DID NOT HAVE HIS XPONDER ON. WE WERE PRETTY MUCH SHOOK UP AND JUST LEVELED OFF FOR A MIN. WE RPTED THE INCIDENT TO APCH CTL AND HE HAD THE CAPT TELEPHONE THE SUPVR UPON LNDG. HOPEFULLY THE FAA WILL GET TO THE BOTTOM OF THE SIT AND FIND OUT WHY THE S3 DID NOT HAVE HIS XPONDER ON AND WHY HE WAS IN CLASS B AIRSPACE WITHOUT TALKING TO APCH CTL.