Narrative:

The pilot of the bellanca reported overhead the airport and was instructed to make right traffic for runway 21R and to report a 2 mi 45 degree to the downwind. He advised that he needed to lose altitude and was instructed to proceed west of the airport and maneuver for the right 45 degree for runway 21R. The bellanca pilot read back 'right 45 degree for runway 21R.' the bellanca pilot reported right base and then corrected himself and said he was now entering downwind opposite the tower. ATC personnel had been looking for the bellanca without luck, and there were many aircraft in the area and pattern. The bellanca should have been visible at this point. I looked toward the opposite downwind (left downwind) back and observed the duchess making a steep, climbing, right turn to avoid collision with the bellanca that was opposite direction to the left downwind for runway 21L. The bellanca was on a right downwind for runway 3R instead of right downwind for runway 21R. Prescott tower works 350000 operations per yr without any radar. We work unfamiliars inbound 10% of the time and many don't enter where they are supposed to be, but most are lucky and do not end up close to other aircraft.

Related reports:

Google
 

Original NASA ASRS Text

Title: PLT OF A BELLANCA ENTERED THE TFC PATTERN CONTRARY TO ATCT LCL CTLR'S INSTRUCTIONS CAUSING AN NMAC WITH A BEECH DUCHESS ON A DOWNWIND LEG IN THE OPPOSITE DIRECTION. THE DUCHESS MADE A STEEP CLBING TURN TO AVOID THE BELLANCA.

Narrative: THE PLT OF THE BELLANCA RPTED OVERHEAD THE ARPT AND WAS INSTRUCTED TO MAKE R TFC FOR RWY 21R AND TO RPT A 2 MI 45 DEG TO THE DOWNWIND. HE ADVISED THAT HE NEEDED TO LOSE ALT AND WAS INSTRUCTED TO PROCEED W OF THE ARPT AND MANEUVER FOR THE R 45 DEG FOR RWY 21R. THE BELLANCA PLT READ BACK 'R 45 DEG FOR RWY 21R.' THE BELLANCA PLT RPTED R BASE AND THEN CORRECTED HIMSELF AND SAID HE WAS NOW ENTERING DOWNWIND OPPOSITE THE TWR. ATC PERSONNEL HAD BEEN LOOKING FOR THE BELLANCA WITHOUT LUCK, AND THERE WERE MANY ACFT IN THE AREA AND PATTERN. THE BELLANCA SHOULD HAVE BEEN VISIBLE AT THIS POINT. I LOOKED TOWARD THE OPPOSITE DOWNWIND (L DOWNWIND) BACK AND OBSERVED THE DUCHESS MAKING A STEEP, CLBING, R TURN TO AVOID COLLISION WITH THE BELLANCA THAT WAS OPPOSITE DIRECTION TO THE L DOWNWIND FOR RWY 21L. THE BELLANCA WAS ON A R DOWNWIND FOR RWY 3R INSTEAD OF R DOWNWIND FOR RWY 21R. PRESCOTT TWR WORKS 350000 OPS PER YR WITHOUT ANY RADAR. WE WORK UNFAMILIARS INBOUND 10% OF THE TIME AND MANY DON'T ENTER WHERE THEY ARE SUPPOSED TO BE, BUT MOST ARE LUCKY AND DO NOT END UP CLOSE TO OTHER 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.