Narrative:

A C172 checked in for runway 16L about 5 miles northwest of the airport at about 7;000 ft; I cleared him to land and noticed that a C560 was also inbound; but had not checked in. It looked like the C560 was going to descend through the C172; so I reached out for the C560; he reported the cessna in sight and at this point I thought they were going to hit. I asked the C560 if he was going to hit the cessna and he said no and told me he was inbound for runway 16L. I told the C560 to change to the runway 16R and cleared him to land. I then told the C172 the traffic was a citation right on top of him descending now for the parallel runway. It was my understanding that the cessna was on a base leg entry which means the TRACON should sequence all aircraft behind him. The TRACON said that he was given a downwind entry so they didn't have to sequence but there was no indication in the scratch pad or any form of communication that the aircraft was on a downwind entry. In my opinion; even if the cessna was on a downwind entry it was too late and the traffic situation had already developed. I feel like there was nothing I could do to separate the two aircraft considering the citation's speed. On initial contact the C560 reported the cessna in sight which tells me he was given traffic before he was switched. If the controller issued the traffic; he should have pulled him off his approach for re-sequencing.

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Original NASA ASRS Text

Title: Tower Controller described a traffic pattern conflict when allegedly the TRACON's sequencing resulted in one aircraft being on top another on final.

Narrative: A C172 checked in for Runway 16L about 5 miles northwest of the airport at about 7;000 FT; I cleared him to land and noticed that a C560 was also inbound; but had not checked in. It looked like the C560 was going to descend through the C172; so I reached out for the C560; he reported the Cessna in sight and at this point I thought they were going to hit. I asked the C560 if he was going to hit the Cessna and he said no and told me he was inbound for Runway 16L. I told the C560 to change to the Runway 16R and cleared him to land. I then told the C172 the traffic was a Citation right on top of him descending now for the parallel runway. It was my understanding that the Cessna was on a base leg entry which means the TRACON should sequence all aircraft behind him. The TRACON said that he was given a downwind entry so they didn't have to sequence but there was no indication in the scratch pad or any form of communication that the aircraft was on a downwind entry. In my opinion; even if the Cessna was on a downwind entry it was too late and the traffic situation had already developed. I feel like there was nothing I could do to separate the two aircraft considering the Citation's speed. On initial contact the C560 reported the Cessna in sight which tells me he was given traffic before he was switched. If the Controller issued the traffic; he should have pulled him off his approach for re-sequencing.

Data retrieved from NASA's ASRS site as of July 2013 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.