Narrative:

I was working local. On the other side of the airport; runway 25r was closed and they were using their one runway for both arrivals and departures. Multiple cross-overs had been happening; and I had most of the departures and arrivals on my side of the airport due to their runway closure.many aircraft were catching [up to] the ones in front on final and I was really keeping an eye on this. Aircraft X was number 2 on final for 24r when he checked in; and they were very fast and catching the aircraft in front of them. I knew based on experience that they would have to be sent around; so I offered for aircraft X runway 24l instead. There was one aircraft in position on 24l; and aircraft X was approaching 4-mile final when I offered them 24l. I told aircraft X about the aircraft holding in position; and I told the aircraft in position about aircraft X on final; then I cleared them for takeoff. I saw that the spacing was good between the departure and aircraft X on 24l; so my focus went back to making a good departure sequence reference my traffic and traffic off the south complex.I set the sequence for aircraft Y to depart first from the full length; and I told the next aircraft to hold short of 24l at V (they would be number two for departure). Then I told aircraft Y to line up and wait on 24l. Aircraft X was still on final; and was tagged up for 24r still; so my scan saw 24r and I my brain processed 24r while scanning aircraft X on final. Out the window; aircraft X appeared to be in final for 24r. All of the visual signals and cues I was receiving confirmed that aircraft X was landing on 24r. Aircraft Y had not lined up on 24l; and they asked me to verify that they were cleared to line up and wait. I scanned again told him yes; lineup and wait on 24l. Aircraft Y's pilot asked what the aircraft on final was doing. Then I realized that I had switched aircraft X to his runway; and I immediately sent aircraft X around. Aircraft X went around; and then the asde-X (airport surface detection equipment) alarmed.socal had been running aircraft tight the entire time I was sitting on local controller (which they do very frequently). When the pilots are told to maintain visual separation from preceding traffic on final; there are a lot of squeeze plays and a lot of close calls with aircraft barely exiting the runway before the next arrival crosses the threshold. Something can be done about this; perhaps; socal could take some of the responsibility for their final and make sure they are not consistently handing us close calls.when I switch someone to the arrival runway; I need to do something that is a visual reminder for myself. Maybe turn over the next departure strip immediately so that this information stays in the forefront of my memory; and so that it will be a reminder that something out of the ordinary is happening on that runway. Or take my pad of paper that I'm using for my arrivals and set it on top of the departure strips. Aircraft on final that are switched to the inboard runway need to be tagged up for the correct runway to allow for this information to be accurately.

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Original NASA ASRS Text

Title: LAX Tower Controller reported instructing an aircraft to lineup and wait; while another aircraft was on final approach. After a query from the flight crew; the Tower Controller promptly issued go-around instructions.

Narrative: I was working local. On the other side of the airport; runway 25r was closed and they were using their one runway for both arrivals and departures. Multiple cross-overs had been happening; and I had most of the departures and arrivals on my side of the airport due to their runway closure.Many aircraft were catching [up to] the ones in front on final and I was really keeping an eye on this. Aircraft X was number 2 on final for 24r when he checked in; and they were very fast and catching the aircraft in front of them. I knew based on experience that they would have to be sent around; so I offered for Aircraft X runway 24l instead. There was one aircraft in position on 24l; and Aircraft X was approaching 4-mile final when I offered them 24l. I told Aircraft X about the aircraft holding in position; and I told the aircraft in position about Aircraft X on final; then I cleared them for takeoff. I saw that the spacing was good between the departure and Aircraft X on 24l; so my focus went back to making a good departure sequence reference my traffic and traffic off the south complex.I set the sequence for Aircraft Y to depart first from the full length; and I told the next aircraft to hold short of 24l at V (they would be number two for departure). Then I told Aircraft Y to line up and wait on 24l. Aircraft X was still on final; and was tagged up for 24r still; so my scan saw 24r and I my brain processed 24r while scanning Aircraft X on final. Out the window; Aircraft X appeared to be in final for 24r. All of the visual signals and cues I was receiving confirmed that Aircraft X was landing on 24r. Aircraft Y had not lined up on 24l; and they asked me to verify that they were cleared to line up and wait. I scanned again told him yes; lineup and wait on 24l. Aircraft Y's pilot asked what the aircraft on final was doing. Then I realized that I had switched Aircraft X to his runway; and I immediately sent Aircraft X around. Aircraft X went around; and then the ASDE-X (Airport Surface Detection Equipment) alarmed.SOCAL had been running aircraft tight the entire time I was sitting on local controller (which they do very frequently). When the pilots are told to maintain visual separation from preceding traffic on final; there are a lot of squeeze plays and a lot of close calls with aircraft barely exiting the runway before the next arrival crosses the threshold. Something can be done about this; perhaps; SOCAL could take some of the responsibility for their final and make sure they are not consistently handing us close calls.When I switch someone to the arrival runway; I need to do something that is a visual reminder for myself. Maybe turn over the next departure strip immediately so that this information stays in the forefront of my memory; and so that it will be a reminder that something out of the ordinary is happening on that runway. Or take my pad of paper that I'm using for my arrivals and set it on top of the departure strips. Aircraft on final that are switched to the inboard runway need to be tagged up for the correct runway to allow for this information to be accurately.

Data retrieved from NASA's ASRS site 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.