Narrative:

I was training on local and we gave the inbound decathlon left downwind entry for runway 21L. We had 3 aircraft in right closed traffic on runway 21R and 1 aircraft in left closed traffic on runway 21L. The decathlon reported left downwind while the C172 on runway 21L was turning left crosswind. At that point; it was impossible to give instructions for separation because the aircraft position could not be accurately determined. The decathlon should have been restr 500 ft above pattern altitude or given a 45 degree entry. It's important not to have too many situations to 'watch' while in the training process. Both aircraft were equipped with adsb and probably helped the decathlon with their situational awareness. The decathlon did climb to avoid the C172.

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Original NASA ASRS Text

Title: PRC LCL CTLR EXPERIENCED CONFLICT AS INBOUND; ISSUED DOWNWIND ENTRY; HAD TO CLB TO AVOID ACFT ON XWIND FOR SAME RWY.

Narrative: I WAS TRAINING ON LCL AND WE GAVE THE INBOUND DECATHLON L DOWNWIND ENTRY FOR RWY 21L. WE HAD 3 ACFT IN R CLOSED TFC ON RWY 21R AND 1 ACFT IN L CLOSED TFC ON RWY 21L. THE DECATHLON RPTED L DOWNWIND WHILE THE C172 ON RWY 21L WAS TURNING L XWIND. AT THAT POINT; IT WAS IMPOSSIBLE TO GIVE INSTRUCTIONS FOR SEPARATION BECAUSE THE ACFT POS COULD NOT BE ACCURATELY DETERMINED. THE DECATHLON SHOULD HAVE BEEN RESTR 500 FT ABOVE PATTERN ALT OR GIVEN A 45 DEG ENTRY. IT'S IMPORTANT NOT TO HAVE TOO MANY SITUATIONS TO 'WATCH' WHILE IN THE TRAINING PROCESS. BOTH ACFT WERE EQUIPPED WITH ADSB AND PROBABLY HELPED THE DECATHLON WITH THEIR SITUATIONAL AWARENESS. THE DECATHLON DID CLB TO AVOID THE C172.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.