Narrative:

The previous controller had told us to expect an ILS to 10L. We briefed the approach for 10 left and also loaded the FMC for runway 10 left. We were south of the airport on a downwind leg when we were handed off to the final approach controller. A small band of cumulonimbus was passing through the area. The line of storms was running north and south about even with the field and a little to the west. One controller was working both runways and radio congestion was very busy because aircraft had started asking for deviations around the weather. We got the vector to final to join the localizer late; and when he gave it to us neither of us were sure that he said one zero left; we both thought he might have said 10R. We tried to break in the radio chatter to clarify our clearance; but it was such rapid fire we could not get word in edgewise. About this time I noticed traffic 900 feet below us and slightly behind us that looked like they were tracking the 10 left localizer; so I called for a go-around and the first officer executed a missed approach. We finally got a radio call in and told approach control we were going missed. He was so busy; he told us to contact the tower for missed approach instructions. We then had an uneventful go-around and return to land on 10L.

Related reports:

Google
 

Original NASA ASRS Text

Title: B737 flight crew reported executing a missed approach due to confusion over which runway was assigned to his aircraft. The confusion was attributed to ATC workload and communication issues exacerbated by radio congestion.

Narrative: The previous Controller had told us to expect an ILS to 10L. We briefed the approach for 10 left and also loaded the FMC for Runway 10 Left. We were south of the airport on a downwind leg when we were handed off to the Final Approach Controller. A small band of cumulonimbus was passing through the area. The line of storms was running north and south about even with the field and a little to the west. One Controller was working both runways and radio congestion was very busy because aircraft had started asking for deviations around the weather. We got the vector to final to join the Localizer late; and when he gave it to us neither of us were sure that he said one zero left; we both thought he might have said 10R. We tried to break in the radio chatter to clarify our clearance; but it was such rapid fire we could not get word in edgewise. About this time I noticed traffic 900 feet below us and slightly behind us that looked like they were tracking the 10 Left Localizer; so I called for a go-around and the First Officer executed a missed approach. We finally got a radio call in and told Approach Control we were going missed. He was so busy; he told us to contact the Tower for missed approach instructions. We then had an uneventful go-around and return to land on 10L.

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.