Narrative:

I was working local control one at las tower. Air carrier X called about between 6 and 7 miles out on a visual approach to runway 25L; his data tag did not indicated that he had visual on the aircraft in front of him. My first transmission to air carrier X was that he had a 40 knot overtake on the preceding aircraft two miles ahead of him and asked him if he had the aircraft in sight. Air carrier X replied negative that he did not see the traffic and he had 'everything out trying to slow' or something to that effect. I then immediately called the final controller to initiate a turn away from the traffic and that air carrier X didn't have visual separation on the traffic. The final controller asked me if I have visual separation which I did not. I then immediately went back to air carrier X and called traffic again now just 1.5 miles ahead of him and he replied that he did now see him; I visually acquired air carrier X as he was reporting traffic in sight. I then issued 'south' turns to air carrier X south of the final for spacing and asked the other carrier if possible to exit the runway at A5 high speed for traffic landing behind him. The other carrier replied that he could comply; I then cleared air carrier X to land. Both aircraft landed safely. Recommendation; we here in las rely heavily on the use of visual separation; so much so that we take it for granted and assume we can and will always be able to use it to our advantage in providing the necessary safety margin for the flying public. The use; or in this case the perceived overuse of visual separation; put us into a position where one controller made the assumption that the next controller would be able to use visual separation and didn't take the necessary actions to ensure the standard separation would be maintained until visual separation could be established. I believe that it would be beneficial to establish days maybe biweekly or monthly where no forms of reduced separation are used. An IFR training and proficiency day to help not only training new controllers but to also maintain a high level of proficiency for certified controllers. I believe this will help in awareness of separation and will trend in the direction of less overtake problems both on final approach and with aircraft departing las. It wasn't weather that was the problem in this case; it was the assumption on visual separation. I think the above type training will reduce the assumption factor.

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Original NASA ASRS Text

Title: LAS controller described a minimal separation event on final during visual approach procedures; noting the facility's reliance on visual separation needs to be reviewed and other forms of separation practiced.

Narrative: I was working Local Control One at LAS tower. Air Carrier X called about between 6 and 7 miles out on a visual approach to Runway 25L; his data tag did not indicated that he had visual on the aircraft in front of him. My first transmission to Air Carrier X was that he had a 40 knot overtake on the preceding aircraft two miles ahead of him and asked him if he had the aircraft in sight. Air Carrier X replied negative that he did not see the traffic and he had 'everything out trying to slow' or something to that effect. I then immediately called the final controller to initiate a turn away from the traffic and that Air Carrier X didn't have visual separation on the traffic. The final controller asked me if I have visual separation which I did not. I then immediately went back to Air Carrier X and called traffic again now just 1.5 miles ahead of him and he replied that he did now see him; I visually acquired Air Carrier X as he was reporting traffic in sight. I then issued 'S' turns to Air Carrier X south of the final for spacing and asked the other carrier if possible to exit the runway at A5 high speed for traffic landing behind him. The other carrier replied that he could comply; I then cleared Air Carrier X to land. Both aircraft landed safely. Recommendation; we here in LAS rely heavily on the use of visual separation; so much so that we take it for granted and assume we can and will always be able to use it to our advantage in providing the necessary safety margin for the flying public. The use; or in this case the perceived overuse of visual separation; put us into a position where one controller made the assumption that the next controller would be able to use visual separation and didn't take the necessary actions to ensure the standard separation would be maintained until visual separation could be established. I believe that it would be beneficial to establish days maybe biweekly or monthly where no forms of reduced separation are used. An IFR training and proficiency day to help not only training new controllers but to also maintain a high level of proficiency for certified controllers. I believe this will help in awareness of separation and will trend in the direction of less overtake problems both on final approach and with aircraft departing LAS. It wasn't weather that was the problem in this case; it was the assumption on visual separation. I think the above type training will reduce the assumption factor.

Data retrieved from NASA's ASRS site as of April 2012 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.