Narrative:

I approached mle from northeast at 3500 ft MSL with radar advisories from omaha approach. After crossing oma at 3500 ft, I was cleared to descend to pattern altitude, and began a descent to 2000 ft, 5 mi northeast. I spotted the beacon, reported the field in sight, and was told to squawk 1200 and change to advisory frequency. I was also told aircraft were seen between me and the field. I had been monitoring CTAF and announced my position and intention to join the left downwind for runway 12. A bonanza then reported crosswind for runway 12. I again announced my position and asked the bonanza to confirm his. He reported that he was at the departure end of runway 30 and that he had me in sight. I asked him again to confirm his position as I announced my entry to downwind at the midfield. At that moment, I observed the bonanza pass overhead on downwind above 200 ft above me, just as he repeated that he had me in sight. I again reported my position, flew a left 360 degrees for spacing, and followed the bonanza at a safe interval. If the bonanza had flown the correct pattern altitude, a midair collision would have occurred. See and avoid is very difficult at night over a densely populated area, as aircraft lights blend with ground lights. Accuracy of position reporting by aircraft in the pattern cannot be relied on. One should not enter a traffic pattern until the aircraft in the pattern have been positively idented. TCASII or radar advisories are unreliable if the other pilot does not turn on his transponder. The bonanza never saw me and must have been looking at ground lights.

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Original NASA ASRS Text

Title: M20P PLT AND A BE35 HAD AN NMAC WHILE ENTERING THE TFC PATTERN FOR RWY 12 AT MLE.

Narrative: I APCHED MLE FROM NE AT 3500 FT MSL WITH RADAR ADVISORIES FROM OMAHA APCH. AFTER XING OMA AT 3500 FT, I WAS CLRED TO DSND TO PATTERN ALT, AND BEGAN A DSCNT TO 2000 FT, 5 MI NE. I SPOTTED THE BEACON, RPTED THE FIELD IN SIGHT, AND WAS TOLD TO SQUAWK 1200 AND CHANGE TO ADVISORY FREQ. I WAS ALSO TOLD ACFT WERE SEEN BTWN ME AND THE FIELD. I HAD BEEN MONITORING CTAF AND ANNOUNCED MY POS AND INTENTION TO JOIN THE L DOWNWIND FOR RWY 12. A BONANZA THEN RPTED XWIND FOR RWY 12. I AGAIN ANNOUNCED MY POS AND ASKED THE BONANZA TO CONFIRM HIS. HE RPTED THAT HE WAS AT THE DEP END OF RWY 30 AND THAT HE HAD ME IN SIGHT. I ASKED HIM AGAIN TO CONFIRM HIS POS AS I ANNOUNCED MY ENTRY TO DOWNWIND AT THE MIDFIELD. AT THAT MOMENT, I OBSERVED THE BONANZA PASS OVERHEAD ON DOWNWIND ABOVE 200 FT ABOVE ME, JUST AS HE REPEATED THAT HE HAD ME IN SIGHT. I AGAIN RPTED MY POS, FLEW A L 360 DEGS FOR SPACING, AND FOLLOWED THE BONANZA AT A SAFE INTERVAL. IF THE BONANZA HAD FLOWN THE CORRECT PATTERN ALT, A MIDAIR COLLISION WOULD HAVE OCCURRED. SEE AND AVOID IS VERY DIFFICULT AT NIGHT OVER A DENSELY POPULATED AREA, AS ACFT LIGHTS BLEND WITH GND LIGHTS. ACCURACY OF POS RPTING BY ACFT IN THE PATTERN CANNOT BE RELIED ON. ONE SHOULD NOT ENTER A TFC PATTERN UNTIL THE ACFT IN THE PATTERN HAVE BEEN POSITIVELY IDENTED. TCASII OR RADAR ADVISORIES ARE UNRELIABLE IF THE OTHER PLT DOES NOT TURN ON HIS XPONDER. THE BONANZA NEVER SAW ME AND MUST HAVE BEEN LOOKING AT GND LIGHTS.

Data retrieved from NASA's ASRS site as of July 2007 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.