Narrative:

I cleared aircraft Y for take-off on runway 20L. This aircraft was on a VFR flight plan with departure instructions to turn left heading 080. The local 1 controller cleared aircraft X for take-off on runway 20R. Aircraft X was on a departure SID that had a left turn of 175. Aircraft that depart runway 20L are supposed to make a left turn of 15 degrees after take-off to avoid aircraft departing runway 20R; this is published in the AFD. Aircraft Y departed and I then issued instructions to a helicopter that was waiting for a taxiway departure that would go westbound across runway 20R. I was carefully watching the helicopter to make sure it cleared runway 20LR and I did not see aircraft Y on the upwind. The radar (stars) did not show any target or primary on the upwind however other controllers ask me what aircraft Y was doing. I could not see aircraft Y out the window because I was looking at the wrong place (where he should have been) while the aircraft had actually flown straight out and was in the vicinity of aircraft X. Aircraft X asked the local 1 controller about the aircraft Y and took evasive action by staying at an extremely low altitude to avoid him. Aircraft Y finally acquired on the radar and approximately 2 miles south of sna. I told aircraft Y to turn left to 080 degrees and he complied.during this session on local 2 I experienced several incorrect data tags in my airspace. The tags were not correctly depicting the position of the aircraft. Several times the radar indicated that an aircraft in the pattern was 1 or 2 miles north of the runway on base or final when in fact the aircraft was on short final. This is very unsafe because if you do not immediately have your aircraft in sight you may think your runway is clear and issue crossings etc.I recommend that the stars system be adjusted to work correctly or to put a different system in place as this provides a false sense of security that aircraft are in a particular when they are not.

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Original NASA ASRS Text

Title: SNA Local Controllers and commercial flight crew reported a NMAC on departure from Runway 20R. GA aircraft departing the left runway was supposed to turn 15 degrees left on departure. The aircraft did not comply with the procedure and drifted into the path of the commercial aircraft which had departed the right runway. The Captain of the commercial aircraft from the right runway observed the GA departure and took evasive action by stopping their climb. ATC did not detect the left departure was not complying with the procedure. The left runway aircraft did not show up on the Tower radar display. The Tower Controller had limited visibility out of the window due to sunlight and both Tower shades drawn down.

Narrative: I cleared Aircraft Y for take-off on Runway 20L. This aircraft was on a VFR flight plan with departure instructions to turn left heading 080. The Local 1 controller cleared Aircraft X for take-off on Runway 20R. Aircraft X was on a departure SID that had a left turn of 175. Aircraft that depart Runway 20L are supposed to make a left turn of 15 degrees after take-off to avoid aircraft departing Runway 20R; this is published in the AFD. Aircraft Y departed and I then issued instructions to a helicopter that was waiting for a taxiway departure that would go westbound across Runway 20R. I was carefully watching the helicopter to make sure it cleared Runway 20LR and I did not see Aircraft Y on the upwind. The radar (STARS) did not show any target or primary on the upwind however other controllers ask me what Aircraft Y was doing. I could not see Aircraft Y out the window because I was looking at the wrong place (where he should have been) while the aircraft had actually flown straight out and was in the vicinity of Aircraft X. Aircraft X asked the Local 1 controller about the Aircraft Y and took evasive action by staying at an extremely low altitude to avoid him. Aircraft Y finally acquired on the radar and approximately 2 miles south of SNA. I told Aircraft Y to turn left to 080 degrees and he complied.During this session on Local 2 I experienced several incorrect data tags in my airspace. The tags were not correctly depicting the position of the aircraft. Several times the radar indicated that an aircraft in the pattern was 1 or 2 miles north of the runway on base or final when in fact the aircraft was on short final. This is very unsafe because if you do not immediately have your aircraft in sight you may think your runway is clear and issue crossings etc.I recommend that the STARS system be adjusted to work correctly or to put a different system in place as this provides a false sense of security that aircraft are in a particular when they are not.

Data retrieved from NASA's ASRS site 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.