Narrative:

Approximately 100 mi west of msp at 41000 ft we had the first warning of possible medical problem. The first officer started preparing in the event we had to divert. Checking WX and getting out approach plates, advising system operations control. Overhead msp the flight attendant advised we needed to land. I gave control of the aircraft to the first officer and took care of ATIS approach. Set up company communication, approach briefing, etc. Msp approach control brought us right in. The WX had been good but rain was in area. We were on approach at 4000 ft, were cleared to intercept the localizer, cleared for approach. We intercepted the localizer and tracking on autoplt, APU armed. Shortly thereafter the aircraft turned right, autoplt tripped and alarm, ILS flag. We were now right of course for runway 12L and asked for landing clearance on runway 12R which we could see through the rain -- tower cleared us. However we were now high and hot for a short wet runway and executed a missed approach. ATC brought us right around for approach and landing on runway 12L. After landing on the second attempt we noticed a long line of aircraft awaiting takeoff from runway 12L. I suspect the localizer interference may have come from a cellphone or other electrical device aboard one of these aircraft in line for departure. An aircraft 3 or 4 mi behind us reported problems with the localizer as well. The tower however reported that it was monitoring normal. Supplemental information from acn 436290: diverted en route to msp for medical emergency. During vectors for ILS runway 12L approach captain verified ILS identifier and autoplts captured the approach course. Just outside of the OM command bars began steering for course correction to the right. Shortly thereafter autoplt disconnected, command bars disappeared and loss of localizer signal was displayed. Approach queried us as we were drifting right of course and we began correcting back to the left. WX at the time was approximately 2 mi visibility with moderate rain showers. At about the same time, a flight behind us commented on loss/intermittent localizer signal. At this time approach controller offered a visual approach to runway 12R and as it came into view we were out of position to land. Go around was accomplished and vectors for ILS runway 12R and landing was completed uneventfully. ATC did not indicate any conflicts with traffic during first approach or go around. Msp approach and tower were very helpful and professional throughout divert and landing.

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Original NASA ASRS Text

Title: BECAUSE OF PAX ILLNESS, ACR FLC MAKES PRECAUTIONARY LNDG AT MSP. FIRST ATTEMPT TO LAND RESULTS IN MISSED APCH ACCOUNT NAVAID MALFUNCTION.

Narrative: APPROX 100 MI W OF MSP AT 41000 FT WE HAD THE FIRST WARNING OF POSSIBLE MEDICAL PROB. THE FO STARTED PREPARING IN THE EVENT WE HAD TO DIVERT. CHKING WX AND GETTING OUT APCH PLATES, ADVISING SYS OPS CTL. OVERHEAD MSP THE FLT ATTENDANT ADVISED WE NEEDED TO LAND. I GAVE CTL OF THE ACFT TO THE FO AND TOOK CARE OF ATIS APCH. SET UP COMPANY COM, APCH BRIEFING, ETC. MSP APCH CTL BROUGHT US RIGHT IN. THE WX HAD BEEN GOOD BUT RAIN WAS IN AREA. WE WERE ON APCH AT 4000 FT, WERE CLRED TO INTERCEPT THE LOC, CLRED FOR APCH. WE INTERCEPTED THE LOC AND TRACKING ON AUTOPLT, APU ARMED. SHORTLY THEREAFTER THE ACFT TURNED R, AUTOPLT TRIPPED AND ALARM, ILS FLAG. WE WERE NOW R OF COURSE FOR RWY 12L AND ASKED FOR LNDG CLRNC ON RWY 12R WHICH WE COULD SEE THROUGH THE RAIN -- TWR CLRED US. HOWEVER WE WERE NOW HIGH AND HOT FOR A SHORT WET RWY AND EXECUTED A MISSED APCH. ATC BROUGHT US RIGHT AROUND FOR APCH AND LNDG ON RWY 12L. AFTER LNDG ON THE SECOND ATTEMPT WE NOTICED A LONG LINE OF ACFT AWAITING TKOF FROM RWY 12L. I SUSPECT THE LOC INTERFERENCE MAY HAVE COME FROM A CELLPHONE OR OTHER ELECTRICAL DEVICE ABOARD ONE OF THESE ACFT IN LINE FOR DEP. AN ACFT 3 OR 4 MI BEHIND US RPTED PROBS WITH THE LOC AS WELL. THE TWR HOWEVER RPTED THAT IT WAS MONITORING NORMAL. SUPPLEMENTAL INFO FROM ACN 436290: DIVERTED ENRTE TO MSP FOR MEDICAL EMER. DURING VECTORS FOR ILS RWY 12L APCH CAPT VERIFIED ILS IDENTIFIER AND AUTOPLTS CAPTURED THE APCH COURSE. JUST OUTSIDE OF THE OM COMMAND BARS BEGAN STEERING FOR COURSE CORRECTION TO THE R. SHORTLY THEREAFTER AUTOPLT DISCONNECTED, COMMAND BARS DISAPPEARED AND LOSS OF LOC SIGNAL WAS DISPLAYED. APCH QUERIED US AS WE WERE DRIFTING R OF COURSE AND WE BEGAN CORRECTING BACK TO THE L. WX AT THE TIME WAS APPROX 2 MI VISIBILITY WITH MODERATE RAIN SHOWERS. AT ABOUT THE SAME TIME, A FLT BEHIND US COMMENTED ON LOSS/INTERMITTENT LOC SIGNAL. AT THIS TIME APCH CTLR OFFERED A VISUAL APCH TO RWY 12R AND AS IT CAME INTO VIEW WE WERE OUT OF POS TO LAND. GAR WAS ACCOMPLISHED AND VECTORS FOR ILS RWY 12R AND LNDG WAS COMPLETED UNEVENTFULLY. ATC DID NOT INDICATE ANY CONFLICTS WITH TFC DURING FIRST APCH OR GAR. MSP APCH AND TWR WERE VERY HELPFUL AND PROFESSIONAL THROUGHOUT DIVERT AND LNDG.

Data retrieved from NASA's ASRS site as of July 2007 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.