Narrative:

Small aircraft X nearly missed collision with another aircraft while on short final to runway 1L at buchanan field in concord, ca. I was approximately 1/2 mi from the threshold about 200 ft AGL when I was passed on the left by another high wing single engine small aircraft Y. The other aircraft was very close -- about 10 ft above me and 40 ft to the side. I reported being passed to the tower and declared that I was going around. The tower confirmed that I would go around and cleared the other small aircraft Y to land. The other pilot confessed that he had not seen my aircraft. I made a circuit in the pattern and landed. The other aircraft was following me in the pattern but he apparently never saw me. The tower was very busy and was instructing aircraft to hold outside the air traffic area at the time of the incident. The incident occurred at dusk in an area surrounded by city lights (all position lights on my aircraft were operating). My aircraft may have been masked by city lights. The tower was conducting lndgs at night on parallel runways. The tower controllers were not properly handling the traffic flow. I was resequenced twice during my approach because the tower did not accurately know the position of landing aircraft.

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Original NASA ASRS Text

Title: SMA Y NON ADHERENCE TO ATC INSTRUCTION TO FOLLOW SMA X HAD NMAC WITH SMA X. PLTDEV. SEE AND AVOID CONCEPT.

Narrative: SMA X NEARLY MISSED COLLISION WITH ANOTHER ACFT WHILE ON SHORT FINAL TO RWY 1L AT BUCHANAN FIELD IN CONCORD, CA. I WAS APPROX 1/2 MI FROM THE THRESHOLD ABOUT 200 FT AGL WHEN I WAS PASSED ON THE L BY ANOTHER HIGH WING SINGLE ENG SMA Y. THE OTHER ACFT WAS VERY CLOSE -- ABOUT 10 FT ABOVE ME AND 40 FT TO THE SIDE. I RPTED BEING PASSED TO THE TWR AND DECLARED THAT I WAS GOING AROUND. THE TWR CONFIRMED THAT I WOULD GAR AND CLRED THE OTHER SMA Y TO LAND. THE OTHER PLT CONFESSED THAT HE HAD NOT SEEN MY ACFT. I MADE A CIRCUIT IN THE PATTERN AND LANDED. THE OTHER ACFT WAS FOLLOWING ME IN THE PATTERN BUT HE APPARENTLY NEVER SAW ME. THE TWR WAS VERY BUSY AND WAS INSTRUCTING ACFT TO HOLD OUTSIDE THE ATA AT THE TIME OF THE INCIDENT. THE INCIDENT OCCURRED AT DUSK IN AN AREA SURROUNDED BY CITY LIGHTS (ALL POS LIGHTS ON MY ACFT WERE OPERATING). MY ACFT MAY HAVE BEEN MASKED BY CITY LIGHTS. THE TWR WAS CONDUCTING LNDGS AT NIGHT ON PARALLEL RWYS. THE TWR CTLRS WERE NOT PROPERLY HANDLING THE TFC FLOW. I WAS RESEQUENCED TWICE DURING MY APCH BECAUSE THE TWR DID NOT ACCURATELY KNOW THE POS OF LNDG ACFT.

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.