A STAFF SPECIALIST WORKING LCL CTL POS FOR CURRENCY CLRED A MIL G4 FOR A LOW APCH ON RWY 6 AND THEN CLRED A BE23 FOR TKOF ON RWY 24. THE CTLR ALSO HAD TFC SHOOTING TOUCH- AND-GOES ON RWY 33 AND DID NOT SEE THE POTENTIAL CONFLICT LTSS BTWN THE G4 AND THE BE23 UNTIL JUST BEFORE THEY PASSED. TFC WAS GIVEN TO THE BE23 WHO LEVELED OFF 600 FT BELOW THE G4.

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I WAS WORKING AS A TWR CTLR ON MAY/XA/97 AT XA47 LCL. I AM A STAFF SPECIALIST AND REQUIRED TO MAINTAIN CURRENCY BY WORKING 8 HRS OF CTL POS TIME. I HAD WORKED THE TWR POS PREVIOUSLY ON APR/XA/97. ON THIS DAY OF MAY/XA/97 I HAD 3 SINGLE ENG ACFT IN THE TOUCH-AND-GO PATTERN WHEN THE G4 CHKED ON THE FREQ; ON APCH TO THE XING RWY. I HAD ALSO 2 OTHER ACFT INBOUND FROM THE RADAR APCH CTL ON THE FREQ. I ALSO HAD 3 ACFT WAITING TO DEPART THE ARPT -- 2 ON THE ACTIVE (RWY 33) AND 1 ON THE XING (RWY 24) RWY. THIS RWY 24 DEP WAS IN OPPOSITION TO THE G4 ARR (RWY 6). THE G4; ON INITIAL CONTACT WITH ME; REQUESTED TO OVERFLY THE ARPT AND ENTER R TFC FOR RWY 33 TO DO A TOUCH-AND-GO. I WAS VERY BUSY AND APPROVED THE REQUEST AND INSTRUCTED THE PLT TO RPT THE CIRCLE. THE 3 BE23'S WERE MAKING TOUCH-AND-GOES TO RWY 33 IN THE L DOWNWIND PATTERN. I TURNED THE BE23 BASE; CLOSE TO THE ARPT TO GET HIM IN FRONT ON AN INBOUND FROM RADAR. I WATCHED THE SEPARATION ON RWY 33 TO ENSURE THE INBOUND (BE36) DIDN'T OVERTAKE THE BE23. THE BE23 TOUCHED DOWN AND BEGAN ACCELERATING AT THE SAME MOMENT THE G4 RPTED 'ON THE GO' ON THE XING RWY. HE WAS AT 700 FT AGL WHEN HE OVERFLEW THE BE23; WHO LEVELED OFF AT 100 FT AGL WHEN HE SAW THE G4. I CALLED TFC TO HIM AS SOON AS HE WAS AIRBORNE; AND HE RPTED THE ACFT IN SIGHT. THERE WERE MANY FACTORS INVOLVED IN THIS LOSS OF SEPARATION. MOST; IF NOT ALL; WERE FACTORS WITHIN MY CTL. 1) I APPROVED AH APCH TO THE XING RWY. 2) I APPROVED A LOW APCH ON THAT XING RWY. 3) I TURNED THE BE23 BASE EARLY TO GET HIM IN FRONT OF THE INBOUND WHEN HE COULD HAVE EXTENDED AND FOLLOWED THE INBOUND AND NOT HAVE BEEN IN CONFLICT WITH THE G4. 4) AS A STAFF SPECIALIST; MY OFFICE DUTIES TAKE PRECEDENCE OVER WORKING TFC AND; AS A RESULT; MY SKILLS AS A CTLR DETERIORATE FROM INFREQUENT USE. 5) THE ABOVE SIT OCCURRED WITHIN 10 MINS AFTER I HAD ASSUED THE TWR POS. 6) I DIDN'T INSTRUCT THE APCH CTL TO METER THE INBOUND FLOW SO THEY WOULD BE SPACED APART IN SUCH A MANNER AS TO NOT BE TOO TAXING OF AN INBOUND RATE. SUGGESTIONS: 1)STAFF SPECIALISTS; AND ANY OTHER CTLRS AND SUPVRS WHO; FOR WHATEVER REASON; WORK TFC INFREQUENTLY; SHOULD NOT WORK PEAK TFC. 2) PRACTICE APCHES AND PATTERN WORK SHOULD BE MONITORED AND MANAGED SO AS NOT TO BECOME UNMANAGEABLE; ESPECIALLY WHEN TOUCH AND GO ACFT ARE OF DISSIMILAR TYPES.