Narrative:

On downwind to base I advised small aircraft X to change runway to runway 18L and cleared for touch and go to make left traffic for runway 18L. On departure small aircraft X was told fly runway heading and I would call crosswind. Small aircraft Y inbound on left downwind for runway 18L. 3 mi southeast of airport when small aircraft Y and small aircraft X were abeam of each other. I told small aircraft X to start crosswind and to follow small aircraft Y. Small aircraft Z called 4 mi northwest already in the air traffic area. I pointed out traffic to follow at 12 O'clock, less than 1 mi on final for runway 18R. Gave small aircraft Z a straight in for runway 18R and the pilot reported traffic in sight. Small aircraft X never received transmission to start crosswind, blocked. 3 south of airport turned crosswind. I changed small aircraft Z to runway 18L on 1 1/2 mi final as aircraft he was following in trail too close and small aircraft Z cleared to land runway 18L. When small aircraft X reported downwind he was abeam #south on runway 18L. Small aircraft X told to follow small aircraft Z on 3/4 mi and reported traffic in sight. Relieving controller plugged in to take the position. Small aircraft X asked if cleared to land. I scanned and saw small aircraft Z short final (over the #south for runway 18L) and did not scan finals. I cleared small aircraft X to land traffic short final. Then my attention diverted for other traffic. When I scanned the runways several seconds later saw small aircraft X approximately 2000' from the approach end of the runway slowed to taxi speed and small aircraft Z landing long behind small aircraft X, about 1000'. At that point to send one around would have made the second aircraft (small aircraft Z) in dangerous position with small aircraft X. Small aircraft X picked out wrong aircraft to follow--he followed the small aircraft for runway 18R, not small aircraft Z. He turned in front of small aircraft Z on final to runway 18L.

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Original NASA ASRS Text

Title: 2 ACFT LANDED ON SAME RWY WITH LESS THAN STANDARD SEPARATION.

Narrative: ON DOWNWIND TO BASE I ADVISED SMA X TO CHANGE RWY TO RWY 18L AND CLRED FOR TOUCH AND GO TO MAKE LEFT TFC FOR RWY 18L. ON DEP SMA X WAS TOLD FLY RWY HDG AND I WOULD CALL XWIND. SMA Y INBND ON LEFT DOWNWIND FOR RWY 18L. 3 MI SE OF ARPT WHEN SMA Y AND SMA X WERE ABEAM OF EACH OTHER. I TOLD SMA X TO START XWIND AND TO FOLLOW SMA Y. SMA Z CALLED 4 MI NW ALREADY IN THE ATA. I POINTED OUT TFC TO FOLLOW AT 12 O'CLOCK, LESS THAN 1 MI ON FINAL FOR RWY 18R. GAVE SMA Z A STRAIGHT IN FOR RWY 18R AND THE PLT RPTED TFC IN SIGHT. SMA X NEVER RECEIVED XMISSION TO START XWIND, BLOCKED. 3 S OF ARPT TURNED XWIND. I CHANGED SMA Z TO RWY 18L ON 1 1/2 MI FINAL AS ACFT HE WAS FOLLOWING IN TRAIL TOO CLOSE AND SMA Z CLRED TO LAND RWY 18L. WHEN SMA X RPTED DOWNWIND HE WAS ABEAM #S ON RWY 18L. SMA X TOLD TO FOLLOW SMA Z ON 3/4 MI AND RPTED TFC IN SIGHT. RELIEVING CTLR PLUGGED IN TO TAKE THE POS. SMA X ASKED IF CLRED TO LAND. I SCANNED AND SAW SMA Z SHORT FINAL (OVER THE #S FOR RWY 18L) AND DID NOT SCAN FINALS. I CLRED SMA X TO LAND TFC SHORT FINAL. THEN MY ATTN DIVERTED FOR OTHER TFC. WHEN I SCANNED THE RWYS SEVERAL SECS LATER SAW SMA X APPROX 2000' FROM THE APCH END OF THE RWY SLOWED TO TAXI SPD AND SMA Z LNDG LONG BEHIND SMA X, ABOUT 1000'. AT THAT POINT TO SEND ONE AROUND WOULD HAVE MADE THE SECOND ACFT (SMA Z) IN DANGEROUS POS WITH SMA X. SMA X PICKED OUT WRONG ACFT TO FOLLOW--HE FOLLOWED THE SMA FOR RWY 18R, NOT SMA Z. HE TURNED IN FRONT OF SMA Z ON FINAL TO RWY 18L.

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.