Narrative:

Was on a post maintenance check flight; VFR with flight following south of ZZZ1. After maintenance items were checked started to return to home airport; but on spur of the moment decided to divert to ZZZ for practice lndgs. Advised ATC; canceled flight following; made a descending 270 degree turn away from airport; so as to be at pattern altitude while approaching airport. Leveled out about 3.5 mi; made standard 45 degree entry to downwind pattern. ZZZ does not have an instrument approach; so did not have a reference pattern advisory frequency in the approach plates; no time to dig out the sectional; so I scanned for conflicting traffic carefully. As I turned downwind; I saw 1 aircraft just lifting off departure end; nothing else. Continued to look for traffic; configured the aircraft for landing; was stabilized on altitude and airspeed; but may have been (in retrospect) a little wide in the pattern. At the 180 degree; turned for left base and began descent. Before I was wings level for base; saw a C172 pass very close (50 yards or less) from my 8 O'clock position; crossing my flight path just behind me. I abandoned the approach and departed the pattern to home base. Considerations: spur of the moment decision led to improper preparation; even though not required; I did not have the great advantage of being able to query and announce in the pattern. I tried to compensate for this by carefully scanning for aircraft; unsuccessfully. Markings may have helped the aircraft to blend into backgnd.

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Original NASA ASRS Text

Title: BE33 PLT HAS NMAC WITH C172 ON BASE LEG AT UNCONTROLLED AIRPORT.

Narrative: WAS ON A POST MAINT CHK FLT; VFR WITH FLT FOLLOWING S OF ZZZ1. AFTER MAINT ITEMS WERE CHKED STARTED TO RETURN TO HOME ARPT; BUT ON SPUR OF THE MOMENT DECIDED TO DIVERT TO ZZZ FOR PRACTICE LNDGS. ADVISED ATC; CANCELED FLT FOLLOWING; MADE A DSNDING 270 DEG TURN AWAY FROM ARPT; SO AS TO BE AT PATTERN ALT WHILE APCHING ARPT. LEVELED OUT ABOUT 3.5 MI; MADE STANDARD 45 DEG ENTRY TO DOWNWIND PATTERN. ZZZ DOES NOT HAVE AN INST APCH; SO DID NOT HAVE A REF PATTERN ADVISORY FREQ IN THE APCH PLATES; NO TIME TO DIG OUT THE SECTIONAL; SO I SCANNED FOR CONFLICTING TFC CAREFULLY. AS I TURNED DOWNWIND; I SAW 1 ACFT JUST LIFTING OFF DEP END; NOTHING ELSE. CONTINUED TO LOOK FOR TFC; CONFIGURED THE ACFT FOR LNDG; WAS STABILIZED ON ALT AND AIRSPD; BUT MAY HAVE BEEN (IN RETROSPECT) A LITTLE WIDE IN THE PATTERN. AT THE 180 DEG; TURNED FOR L BASE AND BEGAN DSCNT. BEFORE I WAS WINGS LEVEL FOR BASE; SAW A C172 PASS VERY CLOSE (50 YARDS OR LESS) FROM MY 8 O'CLOCK POS; XING MY FLT PATH JUST BEHIND ME. I ABANDONED THE APCH AND DEPARTED THE PATTERN TO HOME BASE. CONSIDERATIONS: SPUR OF THE MOMENT DECISION LED TO IMPROPER PREPARATION; EVEN THOUGH NOT REQUIRED; I DID NOT HAVE THE GREAT ADVANTAGE OF BEING ABLE TO QUERY AND ANNOUNCE IN THE PATTERN. I TRIED TO COMPENSATE FOR THIS BY CAREFULLY SCANNING FOR ACFT; UNSUCCESSFULLY. MARKINGS MAY HAVE HELPED THE ACFT TO BLEND INTO BACKGND.

Data retrieved from NASA's ASRS site as of May 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.