ILM CTLR FAILS TO OBSERVE ACFT MANEUVERS IN PATTERN RESULTING IN ACR GAR.

Narrative

LCL CTLR WAS WORKING COMBINED POS IN TWR. ONE CESSNA WAS IN TOUCH-AND-GO TRAINING; L TFC FOR RWY 24. THE ACR RPTED NE ON THE R BASE AND WAS TOLD TO CONTINUE. ANOTHER ACR WAS RELEASED RWY 24 WITH A CTLED DEP TIME. THE CESSNA WAS ON DOWNWIND AND TOLD TO MAKE A R 360 DEG TURN. THIS IS NORMAL PRACTICE TO KEEP TRAINING ACFT CLOSE IN AND DUE TO HAZY CONDITIONS; THE DEPARTING ACR WAS SWITCHED TO DEP OFF THE DEP END AND THE ARRIVING ACR WAS CLRED TO LAND AS HE TURNED A 4 MI FINAL. THE CTLR WAS DELIVERING A CLRNC TO ANOTHER ON THE GND WHEN THE ACR ASKED WHAT THE C172 WAS DOING. THE CTLR THEN GAVE TFC TO THE ACR AND QUESTIONED THE CESSNA. THE CESSNA HAD MADE THE 360 DEG TURN BACK TO DOWNWIND; BUT IMMEDIATELY STARTED A BASE TURN TOWARD THE ACR. THE CESSNA WAS TOLD TO TURN TO RE-ENTER DOWNWIND. THE ACR; BEING UNCOMFORTABLE WITH THE SIT; DECIDED TO GO AROUND TO THE R TO RE-ENTER FINAL. ALL LANDED WITH NO FURTHER PROBS. FACTORS: CTLR PERFORMING MULTIPLE TASKS CAUSED ATTN TO BE DIVERTED FOR SECONDS -- ENOUGH TO MISS THE CESSNA TURNING BASE. INSTRUCTIONS ON WHO TO FOLLOW WERE NOT GIVEN. THE CESSNA TURNED BASE TOO EARLY WHEN EXITING THE 360 DEG MANEUVER. TRAINING LED TO LACK OF AWARENESS OF ACR ON FINAL. ACR PLT'S ALERTNESS AVERTED WORSE SIT.