Narrative:

Given a go around by ATC in ord after [the aircraft in front of us] slowed to 150 early when they were assigned 170 on final. ATC tried to adjust aircraft in front of us; but we were all speed limited to 156 and higher due to arrival wind conditions. ATC initiated a missed approach using improper phraseology then [said it] correctly the second time; during which we went to control wheel steering (cws) mode when; coincidentally; the localizer GS and FD blanked on both sides of the aircraft on autopilot a. We successfully completed the go around and returned to autopilot a as the navigation equipment came back and identified after reset.the approach that followed had the exact same blanking of all navigation data at 500 until the ground; this time hand flying and under visual conditions. We queried ATC and were the only ones who reported an issue. We wrote up the localizer GS sensing in the electronic logbook (elb) and switched aircraft. I followed up [later] and it appeared my write up was released under MEL for the autopilot a; which never failed or was written up by us. I called maintenance control to query him on the decision and he agreed it did not sound like an autopilot issue based on my write up and our conversation. I also briefed the crew on the issue on our arrival to ord. The maintenance controller said he would follow up with an inflight uplink to make the crew aware.my concern rested with the; in my opinion; incorrect diagnosis and remedy to the approach navaid sensing issue; and the repeated issue occurring in the future if it happened to another crew during another similar situation on approach low to the terrain. Especially with the new; descent checklist and arrival flows; increased weather and the go around simultaneously happening the same time; this issue needed more attention than I feel it received.

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Original NASA ASRS Text

Title: B737 Captain reported the localizer; glideslope; and flight director blanked on both sides during approach.

Narrative: Given a go around by ATC in ORD after [the aircraft in front of us] slowed to 150 early when they were assigned 170 on final. ATC tried to adjust aircraft in front of us; but we were all speed limited to 156 and higher due to arrival wind conditions. ATC initiated a missed approach using improper phraseology then [said it] correctly the second time; during which we went to Control Wheel Steering (CWS) mode when; coincidentally; the LOC GS and FD blanked on both sides of the aircraft on autopilot A. We successfully completed the go around and returned to autopilot A as the navigation equipment came back and identified after reset.The approach that followed had the exact same blanking of all NAV data at 500 until the ground; this time hand flying and under visual conditions. We queried ATC and were the only ones who reported an issue. We wrote up the LOC GS sensing in the Electronic Logbook (ELB) and switched aircraft. I followed up [later] and it appeared my write up was released under MEL for the autopilot A; which never failed or was written up by us. I called Maintenance Control to query him on the decision and he agreed it did not sound like an autopilot issue based on my write up and our conversation. I also briefed the crew on the issue on our arrival to ORD. The maintenance controller said he would follow up with an inflight uplink to make the crew aware.My concern rested with the; in my opinion; incorrect diagnosis and remedy to the approach navaid sensing issue; and the repeated issue occurring in the future if it happened to another crew during another similar situation on approach low to the terrain. Especially with the new; descent checklist and arrival flows; increased weather and the go around simultaneously happening the same time; this issue needed more attention than I feel it received.

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.