Narrative:

I was working precision runway monitoring (prm) operations. A CRJ2; lead aircraft; was on the 27L final talking to tower; and a B767; trail aircraft; started about 3.1 in trail. As the crj descended; his speed reduced and the in trail disappeared. The B767 checked in; the first transmission was to cancel his approach clearance and maintain 6;000. I reported the incident and it was determined we had 97% of separation. The more difficult part is to describe how we got here. The first 'link of the chain' was another air carrier that went around short final and later divulged he had a flap problem. I turned him to the downwind and switched him to the final controller per SOP. Normally a go around would land runway 28; but with his issue; he declared an emergency and ended up on runway 27L. In a 'trips' operation; the middle final (27L) is the high side. Being slower at lower altitudes created issues behind him when we got him back on the final. As the B767 was being vectored in the downwind; another aircraft failed to join the localizer; and when I felt he was no longer in a safe area to complete an approach; I sent him around while this was going on. With multiple issues in a short time span; it really increased the workload of everyone on the wall. It was just a strange session; I just don't know what else to say. The feeder and final controller on 27L just didn't appear to have enough room to build in any more delay/in trail in this situation; and it caused the go-around. We were short staffed. Where normal staffing is 24 or 25; we were at 21; held over both mid shift controller; and called in all the 1100 shift personnel for 2 hours extra to start their shifts. I don't feel this has relevance; but may need to be mentioned. It was a tough day today; and had something worse happened; this could have had an influence on it. The personnel on the approach wall; including supervisors and tmc all did an amazing job.

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Original NASA ASRS Text

Title: TRACON PRM Controller described a loss of separation event during complicated/busy simultaneous procedures complicated further by an emergency aircraft.

Narrative: I was working Precision Runway Monitoring (PRM) operations. A CRJ2; lead aircraft; was on the 27L final talking to Tower; and a B767; trail aircraft; started about 3.1 in trail. As the CRJ descended; his speed reduced and the in trail disappeared. The B767 checked in; the first transmission was to cancel his approach clearance and maintain 6;000. I reported the incident and it was determined we had 97% of separation. The more difficult part is to describe how we got here. The first 'link of the chain' was another Air Carrier that went around short final and later divulged he had a flap problem. I turned him to the downwind and switched him to the Final Controller per SOP. Normally a go around would land Runway 28; but with his issue; he declared an emergency and ended up on Runway 27L. In a 'trips' operation; the middle final (27L) is the high side. Being slower at lower altitudes created issues behind him when we got him back on the final. As the B767 was being vectored in the downwind; another aircraft failed to join the localizer; and when I felt he was no longer in a safe area to complete an approach; I sent him around while this was going on. With multiple issues in a short time span; it really increased the workload of everyone on the wall. It was just a strange session; I just don't know what else to say. The Feeder and Final Controller on 27L just didn't appear to have enough room to build in any more delay/in trail in this situation; and it caused the go-around. We were short staffed. Where normal staffing is 24 or 25; we were at 21; held over both Mid Shift Controller; and called in all the 1100 shift personnel for 2 hours extra to start their shifts. I don't feel this has relevance; but may need to be mentioned. It was a tough day today; and had something worse happened; this could have had an influence on it. The personnel on the approach wall; including supervisors and TMC all did an amazing job.

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.