SR20
Air Traffic Control Fully Certified
Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict
Air Traffic Control Separated Traffic
Human Factors
An SR22 was inbound from the south on a modified right base entry; requesting pattern work. Aircraft was at 1;500 FT; was given the instruction to descend to pattern altitude at pilot's discretion; and to enter the right base to Runway 09R. Additional traffic was to this aircraft's left; making a base entry to Runway 09C for a full stop. Additional traffic was already established in the right traffic pattern of Runway 09R. I misjudged the timing of the inbound the SR22 with the other aircraft in the pattern. My plan was to have the SR22 be first to the runway; and the established aircraft follow the SR22. It ended up being a tie; and I tried to correct the situation by having the SR22 fly eastbound (opposite direction of the other aircraft) with the attempts of having the SR22 now follow the other aircraft. I issued traffic to the SR22 after I told him to make the eastbound turn. The pilot did so; and came close to the other aircraft. There are many things: keep the inbound aircraft at 1;500 FT altitude; could have had existing aircraft make a left 360 in the downwind to create more spacing; could have extended the existing aircraft's upwind; could have turned the SR22 westbound; could have had more urgency with the pilot to have him execute his eastbound turn immediately and give a traffic alert to advise him of the reason for the immediate turn.
SFB Controller described a pattern conflict resulting from ATC spacing misjudgments.