Narrative:

I was working local control east and runway 17 was my runway. I had cleared single engine cessna; to land on runway 17 from the downwind. In the meantime I did several other things: made several xmissions; and entered a code of a VFR helicopter off of skypark airport into stars (radar data). I was coordinating the helicopter with local city (VFR local controller) and looked up to check on the progress of the cessna. I could not see the data tag for the aircraft as it was covered by a runway 16L IFR arrival aircraft and some other aircraft. It took me a moment to realize that the other aircraft was on final to runway 17. Because of the data tag overlap and the proximity of the aircraft; I did not want to change the altitude of either the citation or the cessna. I issued an immediate left turn; fly eastbound to the cessna as the citation finally attempted to check in on my frequency. The frequency had not been busy before this; the citation had either not been switched by approach or chose not to call until he was 1 - 1 1/2 mi final at twice the speed of the cessna who was about a 1 mi final. By the time I could see the call sign of the citation and clear him to land; he was over the threshold. The cessna had turned; as instructed; and I brought him back around to land; and apologized. I do not know how close they got. I had been looking through my binoculars earlier as it was hazy and the aircraft were hard to see. Another controller said that the citation had flown a nonstandard pattern from about the FAF of the west runway to the numbers of runway 17. He was twice the speed of the cessna and not talking to me. I told the supervisor and he asked if I lost separation. I said that they did not hit because of the data tag overlap. I do not know how close they got.

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Original NASA ASRS Text

Title: SLC TWR CTLR WITNESSED NMAC WHEN ACFT ON FINAL EITHER FAILED TO CONTACT TWR OR APCH CTLR FAILED TO XFER ACFT IN SUFFICIENT TIME TO AVOID CONFLICT.

Narrative: I WAS WORKING LCL CTL E AND RWY 17 WAS MY RWY. I HAD CLRED SINGLE ENG CESSNA; TO LAND ON RWY 17 FROM THE DOWNWIND. IN THE MEANTIME I DID SEVERAL OTHER THINGS: MADE SEVERAL XMISSIONS; AND ENTERED A CODE OF A VFR HELI OFF OF SKYPARK ARPT INTO STARS (RADAR DATA). I WAS COORDINATING THE HELI WITH LCL CITY (VFR LCL CTLR) AND LOOKED UP TO CHK ON THE PROGRESS OF THE CESSNA. I COULD NOT SEE THE DATA TAG FOR THE ACFT AS IT WAS COVERED BY A RWY 16L IFR ARR ACFT AND SOME OTHER ACFT. IT TOOK ME A MOMENT TO REALIZE THAT THE OTHER ACFT WAS ON FINAL TO RWY 17. BECAUSE OF THE DATA TAG OVERLAP AND THE PROX OF THE ACFT; I DID NOT WANT TO CHANGE THE ALT OF EITHER THE CITATION OR THE CESSNA. I ISSUED AN IMMEDIATE L TURN; FLY EBOUND TO THE CESSNA AS THE CITATION FINALLY ATTEMPTED TO CHK IN ON MY FREQ. THE FREQ HAD NOT BEEN BUSY BEFORE THIS; THE CITATION HAD EITHER NOT BEEN SWITCHED BY APCH OR CHOSE NOT TO CALL UNTIL HE WAS 1 - 1 1/2 MI FINAL AT TWICE THE SPD OF THE CESSNA WHO WAS ABOUT A 1 MI FINAL. BY THE TIME I COULD SEE THE CALL SIGN OF THE CITATION AND CLR HIM TO LAND; HE WAS OVER THE THRESHOLD. THE CESSNA HAD TURNED; AS INSTRUCTED; AND I BROUGHT HIM BACK AROUND TO LAND; AND APOLOGIZED. I DO NOT KNOW HOW CLOSE THEY GOT. I HAD BEEN LOOKING THROUGH MY BINOCULARS EARLIER AS IT WAS HAZY AND THE ACFT WERE HARD TO SEE. ANOTHER CTLR SAID THAT THE CITATION HAD FLOWN A NONSTANDARD PATTERN FROM ABOUT THE FAF OF THE W RWY TO THE NUMBERS OF RWY 17. HE WAS TWICE THE SPD OF THE CESSNA AND NOT TALKING TO ME. I TOLD THE SUPVR AND HE ASKED IF I LOST SEPARATION. I SAID THAT THEY DID NOT HIT BECAUSE OF THE DATA TAG OVERLAP. I DO NOT KNOW HOW CLOSE THEY GOT.

Data retrieved from NASA's ASRS site as of January 2009 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.