Narrative:

Our aircraft, a C172, was set up for a straight-in approach for runway 21L at prc. Prc tower told us to maintain 6500 ft (500 ft above traffic pattern altitude), over-fly the runway, and report above the threshold. We complied. After reporting the threshold, we were told to execute a turn to the left downwind and descend to traffic pattern altitude. Traffic reported to us was a twin beech turning downwind from crosswind. During our turning descent from above the runway to the downwind, I noticed a shadow on the ground that was not ours. The instructor in the aircraft looked back for the beech and we determined the shadow was neither ours nor that of the beech. Once established on downwind, I noticed that an unidented aircraft approximately 20 ft to our left and 200 ft below was climbing into our flight path from left to right. Prc tower cleared us to land and advised us of an aircraft departing the left downwind. Upon realizing that standard evasive maneuvers to the right would prove fatal, we immediately turned sharply to the left to overfly the runway again. Leading to this were many factors. The unidented beech did not depart using a standard downwind departure as suggested by the aim. If he had, he would not have been a factor. Additionally, the tower failed to properly sequence the aircraft. A cessna was told to enter the downwind in front of a twin engine aircraft and on top of an aircraft climbing through traffic pattern altitude, a situation that would have been no factor had we flown a normal sized pattern.

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Original NASA ASRS Text

Title: C172 TRAINEE AND UNKNOWN BEECH ACFT HAD NMAC OVER PRC ARPT.

Narrative: OUR ACFT, A C172, WAS SET UP FOR A STRAIGHT-IN APCH FOR RWY 21L AT PRC. PRC TWR TOLD US TO MAINTAIN 6500 FT (500 FT ABOVE TFC PATTERN ALT), OVER-FLY THE RWY, AND RPT ABOVE THE THRESHOLD. WE COMPLIED. AFTER RPTING THE THRESHOLD, WE WERE TOLD TO EXECUTE A TURN TO THE L DOWNWIND AND DSND TO TFC PATTERN ALT. TFC RPTED TO US WAS A TWIN BEECH TURNING DOWNWIND FROM XWIND. DURING OUR TURNING DSCNT FROM ABOVE THE RWY TO THE DOWNWIND, I NOTICED A SHADOW ON THE GND THAT WAS NOT OURS. THE INSTRUCTOR IN THE ACFT LOOKED BACK FOR THE BEECH AND WE DETERMINED THE SHADOW WAS NEITHER OURS NOR THAT OF THE BEECH. ONCE ESTABLISHED ON DOWNWIND, I NOTICED THAT AN UNIDENTED ACFT APPROX 20 FT TO OUR L AND 200 FT BELOW WAS CLBING INTO OUR FLT PATH FROM L TO R. PRC TWR CLRED US TO LAND AND ADVISED US OF AN ACFT DEPARTING THE L DOWNWIND. UPON REALIZING THAT STANDARD EVASIVE MANEUVERS TO THE R WOULD PROVE FATAL, WE IMMEDIATELY TURNED SHARPLY TO THE L TO OVERFLY THE RWY AGAIN. LEADING TO THIS WERE MANY FACTORS. THE UNIDENTED BEECH DID NOT DEPART USING A STANDARD DOWNWIND DEP AS SUGGESTED BY THE AIM. IF HE HAD, HE WOULD NOT HAVE BEEN A FACTOR. ADDITIONALLY, THE TWR FAILED TO PROPERLY SEQUENCE THE ACFT. A CESSNA WAS TOLD TO ENTER THE DOWNWIND IN FRONT OF A TWIN ENG ACFT AND ON TOP OF AN ACFT CLBING THROUGH TFC PATTERN ALT, A SIT THAT WOULD HAVE BEEN NO FACTOR HAD WE FLOWN A NORMAL SIZED PATTERN.

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.