C152 AND C421 HAD NMAC AT OLV.

Narrative

ACFT X WAS CONDUCTING TOUCH-AND-GO TFC PATTERN TRAINING OPS AS ACFT Y RPTED 3 MI E OF OLV ON CTAF. ON UPWIND LEG; ACFT X RPTED LOCATION AND ALT AND ASKED IF ACFT Y HAD ACFT X IN SIGHT. HE SAID YES; HE HAD TFC ON THE DOWNWIND IN SIGHT. ACFT X RESPONDED WITH RESTATEMENT OF POS AS WE TURNED XWIND FOR RWY 18. ACFT Y RPTED MAKING A 360 DEG TURN TO SLOW DOWN AND KEEP SPACING IN THE PATTERN. ACFT X TURNED ON DOWNWIND AND MADE APPROPRIATE RADIO CALL. AS ACFT X ROLLED WINGS TO LEVEL; ACFT Y WAS TO OUR 10-11 O'CLOCK POS; SAME ALT HDG DIRECTLY TOWARDS ACFT X. ACFT X THEN MADE A DIVING R TURN TO AVOID ACFT Y (20 DEGS R AND 10 DEGS NOSE DOWN). ACFT Y PASSED BEHIND ACFT X AND THEN PROCEEDED TO FLY PARALLEL OF ACFT X ABOUT 600 FT TO THE R WINGTIP IN THE PATTERN. CONTRIBUTING FACTORS: ACFT Y'S FAILURE TO BE PROPERLY CONFIGURED (SLOWED) PRIOR TO ENTERING THE PATTERN. ACFT Y PERFORMED A 360 DEG L TURN 'INSIDE' THE TFC PATTERN. ACFT X WAS HIGH-WINGED; WHICH LIMITED VISIBILITY TO THE 'INSIDE' OF TURNS. (OLV USES L-HAND TFC PATTERNS FOR RWY 18.) THERE IS NO TWR CTL AT OLV; WHICH IS THE BUSIEST ARPT IN MISSISSIPPI BY NUMBER OF ARRS AND DEPS ON A DAILY BASIS.