Narrative:

Small aircraft X requested departure and to remain in the local traffic pattern. Small aircraft X was cleared for takeoff and instructed to make right traffic. Approximately 3 mins later, during the controller's routine scan of the pattern, a high winged aircraft was visually sighted on the left crosswind. The controller believed that the high winged aircraft sighted on left crosswind was small aircraft X. There were 2 small aircraft's approaching right downwind entries, and only 2 radar targets on the controller's scope to represent these visually sighted aircraft. No other targets were observed on the radar scope in the traffic pattern. The controller asked small aircraft X to say pilot's intentions. The pilot responded that he desired a touch and go. The controller instructed the pilot to make a right 360 degree turn and report entering the left downwind. The pilot responded, 'ok, a right 360?' the controller confirmed the pilot's inquiry about a right 360 degree turn, and then went on to say that the pilot had been instructed to make right traffic, but to now make a 360 degree turn and report entering the left downwind. The pilot answered with, 'ok, a right 360.' these responses by the pilot of small aircraft X further reinforced to the controller that the aircraft visually sighted on a left crosswind was small aircraft X. Following this conversation, the controller's attention was momentarily focused on other duties, including xmissions to other aircraft. The controller then sighted small aircraft X estimated to be at an altitude approximately 500' above small aircraft Y on right downwind, and flying a heading approximately perpendicular to that of the small aircraft. Small aircraft X was instructed to fly to a point located on the edge of the air traffic area and away from the pattern traffic. Small aircraft X advised the tower that he desired to depart the pattern. Small aircraft Y said that he had turned to avoid small aircraft X. When the controller advised small aircraft X that his transponder appeared inoperative, he acknowledged this information. This situation happened in an air traffic area which borders a terminal control area. Thus, even though the air traffic area was not a radar controled area, xponders are still required in this airspace located so close to a TCA. Had all aircraft been using their required xponders, the situation might have been avoided.

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Original NASA ASRS Text

Title: SMA Y HAD NMAC WITH SMA X. EVASIVE ACTION TAKEN. SEE AND AVOID CONCEPT.

Narrative: SMA X REQUESTED DEP AND TO REMAIN IN THE LCL TFC PATTERN. SMA X WAS CLRED FOR TKOF AND INSTRUCTED TO MAKE RIGHT TFC. APPROX 3 MINS LATER, DURING THE CTLR'S ROUTINE SCAN OF THE PATTERN, A HIGH WINGED ACFT WAS VISUALLY SIGHTED ON THE LEFT XWIND. THE CTLR BELIEVED THAT THE HIGH WINGED ACFT SIGHTED ON LEFT XWIND WAS SMA X. THERE WERE 2 SMA'S APCHING RIGHT DOWNWIND ENTRIES, AND ONLY 2 RADAR TARGETS ON THE CTLR'S SCOPE TO REPRESENT THESE VISUALLY SIGHTED ACFT. NO OTHER TARGETS WERE OBSERVED ON THE RADAR SCOPE IN THE TFC PATTERN. THE CTLR ASKED SMA X TO SAY PLT'S INTENTIONS. THE PLT RESPONDED THAT HE DESIRED A TOUCH AND GO. THE CTLR INSTRUCTED THE PLT TO MAKE A RIGHT 360 DEG TURN AND RPT ENTERING THE LEFT DOWNWIND. THE PLT RESPONDED, 'OK, A RIGHT 360?' THE CTLR CONFIRMED THE PLT'S INQUIRY ABOUT A RIGHT 360 DEG TURN, AND THEN WENT ON TO SAY THAT THE PLT HAD BEEN INSTRUCTED TO MAKE RIGHT TFC, BUT TO NOW MAKE A 360 DEG TURN AND RPT ENTERING THE LEFT DOWNWIND. THE PLT ANSWERED WITH, 'OK, A RIGHT 360.' THESE RESPONSES BY THE PLT OF SMA X FURTHER REINFORCED TO THE CTLR THAT THE ACFT VISUALLY SIGHTED ON A LEFT XWIND WAS SMA X. FOLLOWING THIS CONVERSATION, THE CTLR'S ATTN WAS MOMENTARILY FOCUSED ON OTHER DUTIES, INCLUDING XMISSIONS TO OTHER ACFT. THE CTLR THEN SIGHTED SMA X ESTIMATED TO BE AT AN ALT APPROX 500' ABOVE SMA Y ON RIGHT DOWNWIND, AND FLYING A HDG APPROX PERPENDICULAR TO THAT OF THE SMA. SMA X WAS INSTRUCTED TO FLY TO A POINT LOCATED ON THE EDGE OF THE ATA AND AWAY FROM THE PATTERN TFC. SMA X ADVISED THE TWR THAT HE DESIRED TO DEPART THE PATTERN. SMA Y SAID THAT HE HAD TURNED TO AVOID SMA X. WHEN THE CTLR ADVISED SMA X THAT HIS XPONDER APPEARED INOP, HE ACKNOWLEDGED THIS INFO. THIS SITUATION HAPPENED IN AN ATA WHICH BORDERS A TERMINAL CTL AREA. THUS, EVEN THOUGH THE ATA WAS NOT A RADAR CTLED AREA, XPONDERS ARE STILL REQUIRED IN THIS AIRSPACE LOCATED SO CLOSE TO A TCA. HAD ALL ACFT BEEN USING THEIR REQUIRED XPONDERS, THE SITUATION MIGHT HAVE BEEN AVOIDED.

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.