Narrative:

We were proceeding direct to jadop at 5000 feet and had been cleared for the ILS 9 approach at cvg. The captain asked if I had identified the localizer. I replied that I was listening for it; but had not yet heard it; and remarked that as we were getting close to the localizer; I should be able to hear it. I informed approach control that we were not receiving the runway 9 localizer. Approach control asked the tower; and the tower said that it was up and in the green. We turned inbound on the final approach course based on FMS RNAV data and I was able to see the runway at that point. We were descending on the final approach course and configuring for landing. At this point; the exact sequence becomes very hazy because my task loading was fairly high - listening through the ambient noise (the packs in this aircraft are noisier than most; even in single pack operation) for the captain's configuration commands and responding to ATC questions about our status. It eventually reached a point where I had to tell approach control to standby; prioritizing the first item of 'aviate; navigate; communicate' over the third. Approach control called with a low altitude alert somewhere around 2;400 feet and the captain called for a go-around. We had visual contact with the runway throughout this event and were not in IMC at any time prior to the go-around. After the go-around; the captain found that the localizer frequency had been changed from 111.9 to 110.9. I do not know how that could have happened; as I had not been doing anything in that area. I had changed frequencies on the left comm radio a number of times during the arrival; but I don't remember ever reaching for or turning the wrong knob during that time. I was able to identify the localizer; so we informed approach control that we could take vectors for the approach again. While being vectored; the captain had me set up the ILS 9 in the FMS again; and while doing that; I saw in the scratchpad a runway/localizer frequency mismatch message. I did not see that; an 'FMC message' EICAS message; or the FMC discrete light at any time before then. We completed the approach and landed normally.reviewing the event afterward; I don't know why it didn't occur to me to check the localizer frequency on the ILS receiver. It seems so obvious a thing to check; but I suppose there was a bias toward believing that it was set correctly since it had already been set up and briefed prior to top of descent. That in combination with being at a point where there was a lot of intra-cockpit communication; aircraft configuration; and the flurry of non-routine ATC communications left me without a lot of brain cycles to do logical troubleshooting of what is a relatively uncommon occurrence.

Google
 

Original NASA ASRS Text

Title: B767 First Officer reported executing a go-around after TRACON issued a low altitude alert on approach to CVG. The localizer was later found to be mistuned.

Narrative: We were proceeding direct to JADOP at 5000 feet and had been cleared for the ILS 9 approach at CVG. The Captain asked if I had identified the localizer. I replied that I was listening for it; but had not yet heard it; and remarked that as we were getting close to the localizer; I should be able to hear it. I informed Approach Control that we were not receiving the Runway 9 localizer. Approach Control asked the Tower; and the Tower said that it was up and in the green. We turned inbound on the final approach course based on FMS RNAV data and I was able to see the runway at that point. We were descending on the final approach course and configuring for landing. At this point; the exact sequence becomes very hazy because my task loading was fairly high - listening through the ambient noise (the packs in this aircraft are noisier than most; even in single pack operation) for the Captain's configuration commands and responding to ATC questions about our status. It eventually reached a point where I had to tell Approach Control to standby; prioritizing the first item of 'aviate; navigate; communicate' over the third. Approach Control called with a low altitude alert somewhere around 2;400 feet and the Captain called for a go-around. We had visual contact with the runway throughout this event and were not in IMC at any time prior to the go-around. After the go-around; the Captain found that the localizer frequency had been changed from 111.9 to 110.9. I do not know how that could have happened; as I had not been doing anything in that area. I had changed frequencies on the left comm radio a number of times during the arrival; but I don't remember ever reaching for or turning the wrong knob during that time. I was able to identify the localizer; so we informed Approach Control that we could take vectors for the approach again. While being vectored; the Captain had me set up the ILS 9 in the FMS again; and while doing that; I saw in the scratchpad a runway/localizer frequency mismatch message. I did not see that; an 'FMC Message' EICAS message; or the FMC discrete light at any time before then. We completed the approach and landed normally.Reviewing the event afterward; I don't know why it didn't occur to me to check the localizer frequency on the ILS receiver. It seems so obvious a thing to check; but I suppose there was a bias toward believing that it was set correctly since it had already been set up and briefed prior to top of descent. That in combination with being at a point where there was a lot of intra-cockpit communication; aircraft configuration; and the flurry of non-routine ATC communications left me without a lot of brain cycles to do logical troubleshooting of what is a relatively uncommon occurrence.

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.