Narrative:

I was working west arrival; vectoring aircraft for the ILS to runway 28C at ord. There was adverse winter weather in the area at this time; restricting ord to a 2 runway arrival operation. Due to this; demand was high; and constant. All day; the runway 28R glideslope had been out (presumed due to weather issues). During a busy period of traffic; the city wanted to have RWY28C groomed; cleaned and inspected due to the continuing ice conditions. At this point; 28R glideslope was returned to service. I was informed by the main arrival coordinator to begin vectoring arrivals to the new runway; and told the [glideslope] would be fully functional. I made the challenging switch to the new runway; and immediately had a full final to about 40 NM. I noticed the low altitude alert go off for aircraft X; and issued the warning. Aircraft X arrested their descent; and noted they were having an issue with the glideslope. At this point I noticed aircraft Y that was also descending well below the glideslope. I immediately climbed them; and issued missed approach instructions. From this point; it was obvious there was still an issue with the glideslope; so I went ahead with the arduous task of reissuing every aircraft the localizer approach for runway 28R. This; along with what was already a busy airspace full of airplanes; aircraft X and aircraft Y both then needed to go around for unstable approaches. I was unable to make the coordination with the tower as I was too busy managing my aircraft. At this point the glideslope was taken out of service and deemed unreliable. This caused several ATIS changes; to reflect the equipment malfunction; and approach changes. Along with the rapidly changing weather; I again was oversaturated giving the new ATIS and weather conditions to pilots. It seems the appropriate work wasn't completed to remedy the problem on the glideslope; and nearly caused aircraft X and aircraft Y to descend below the MVA (minimum vectoring altitude) as they crossed downtown chicago in IFR conditions. This seems like a serious safety issue. Have some better form of verification equipment is working prior to resuming using that equipment.

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Original NASA ASRS Text

Title: Chicago TRACON Controller reported adverse weather and a malfunctioning glideslope caused aircraft to go around.

Narrative: I was working West Arrival; vectoring aircraft for the ILS to RWY 28C at ORD. There was adverse winter weather in the area at this time; restricting ORD to a 2 runway arrival operation. Due to this; demand was high; and constant. All day; the RWY 28R glideslope had been out (presumed due to weather issues). During a busy period of traffic; the city wanted to have RWY28C groomed; cleaned and inspected due to the continuing ice conditions. At this point; 28R glideslope was returned to service. I was informed by the main arrival coordinator to begin vectoring arrivals to the new runway; and told the [glideslope] would be fully functional. I made the challenging switch to the new runway; and immediately had a full final to about 40 NM. I noticed the low altitude alert go off for Aircraft X; and issued the warning. Aircraft X arrested their descent; and noted they were having an issue with the glideslope. At this point I noticed Aircraft Y that was also descending well below the glideslope. I immediately climbed them; and issued missed approach instructions. From this point; it was obvious there was still an issue with the glideslope; so I went ahead with the arduous task of reissuing every aircraft the localizer approach for runway 28R. This; along with what was already a busy airspace full of airplanes; Aircraft X and Aircraft Y both then needed to go around for unstable approaches. I was unable to make the coordination with the tower as I was too busy managing my aircraft. At this point the glideslope was taken out of service and deemed unreliable. This caused several ATIS changes; to reflect the equipment malfunction; and approach changes. Along with the rapidly changing weather; I again was oversaturated giving the new ATIS and weather conditions to pilots. It seems the appropriate work wasn't completed to remedy the problem on the glideslope; and nearly caused Aircraft X and Aircraft Y to descend below the MVA (Minimum Vectoring Altitude) as they crossed Downtown Chicago in IFR conditions. This seems like a serious safety issue. Have some better form of verification equipment is working prior to resuming using that equipment.

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.