Narrative:

At about XA15 on apr/sat/05; I was on left downwind for runway 19L at ccr. I had called the tower from just west of mt diablo; and was instructed to make left traffic for runway 19L. The pattern was fairly busy; and I was having some trouble hearing all tower communications. In fact; prior to calling tower; I had just completed a 360 degree turn near diablo since the frequency was so crowded. This was my first landing at ccr; so I wanted to be extra cautious about making the correct approach. As I entered left downwind for runway 19L from the 45 degree entry; I was aware from the radio that there was other landing traffic in the area; but I did not have it in sight. I believe it was a bonanza; but I'm not certain. After passing abeam the numbers for runway 19L; I still did not have traffic in sight. About this time; tower called to 'aircraft north of the airport' (or similar phrase). As I was then passing to the north; I assumed he was talking to me and idented myself. Within the next few seconds; I asked the tower to call my base; and the near midair collision with the other aircraft occurred. I don't remember which of these 2 events was first. The other aircraft (probably bonanza) passed nearly head-on from slightly above at my 1 O'clock position; and then across to my left. I was still on (now extended) downwind as it passed. At about this point; tower reassigned me to runway 19R. I turned base and final and made a normal landing on runway 19R. If NASA has access to tower voice records and/or radar traces; please call me with any information. I would like to better understand the circumstances leading to this incident; plus any hints for avoiding same/similar.

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Original NASA ASRS Text

Title: A PA28 PLT RPTS AN NMAC EVENT WITH A BONANZA IN A BUSY CCR TFC PATTERN.

Narrative: AT ABOUT XA15 ON APR/SAT/05; I WAS ON L DOWNWIND FOR RWY 19L AT CCR. I HAD CALLED THE TWR FROM JUST W OF MT DIABLO; AND WAS INSTRUCTED TO MAKE L TFC FOR RWY 19L. THE PATTERN WAS FAIRLY BUSY; AND I WAS HAVING SOME TROUBLE HEARING ALL TWR COMS. IN FACT; PRIOR TO CALLING TWR; I HAD JUST COMPLETED A 360 DEG TURN NEAR DIABLO SINCE THE FREQ WAS SO CROWDED. THIS WAS MY FIRST LNDG AT CCR; SO I WANTED TO BE EXTRA CAUTIOUS ABOUT MAKING THE CORRECT APCH. AS I ENTERED L DOWNWIND FOR RWY 19L FROM THE 45 DEG ENTRY; I WAS AWARE FROM THE RADIO THAT THERE WAS OTHER LNDG TFC IN THE AREA; BUT I DID NOT HAVE IT IN SIGHT. I BELIEVE IT WAS A BONANZA; BUT I'M NOT CERTAIN. AFTER PASSING ABEAM THE NUMBERS FOR RWY 19L; I STILL DID NOT HAVE TFC IN SIGHT. ABOUT THIS TIME; TWR CALLED TO 'ACFT N OF THE ARPT' (OR SIMILAR PHRASE). AS I WAS THEN PASSING TO THE N; I ASSUMED HE WAS TALKING TO ME AND IDENTED MYSELF. WITHIN THE NEXT FEW SECONDS; I ASKED THE TWR TO CALL MY BASE; AND THE NMAC WITH THE OTHER ACFT OCCURRED. I DON'T REMEMBER WHICH OF THESE 2 EVENTS WAS FIRST. THE OTHER ACFT (PROBABLY BONANZA) PASSED NEARLY HEAD-ON FROM SLIGHTLY ABOVE AT MY 1 O'CLOCK POS; AND THEN ACROSS TO MY L. I WAS STILL ON (NOW EXTENDED) DOWNWIND AS IT PASSED. AT ABOUT THIS POINT; TWR REASSIGNED ME TO RWY 19R. I TURNED BASE AND FINAL AND MADE A NORMAL LNDG ON RWY 19R. IF NASA HAS ACCESS TO TWR VOICE RECORDS AND/OR RADAR TRACES; PLEASE CALL ME WITH ANY INFO. I WOULD LIKE TO BETTER UNDERSTAND THE CIRCUMSTANCES LEADING TO THIS INCIDENT; PLUS ANY HINTS FOR AVOIDING SAME/SIMILAR.

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.