B737-800
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface; Distraction; Communication Breakdown; Workload
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Weather / Turbulence
Flight Crew Took Evasive Action; Flight Crew Executed Go Around / Missed Approach
ATC Equipment / Nav Facility / Buildings; Weather
On final ILS 28R; moderate chop maybe light turbulence in medium rain and IMC received verbal 'low altitude alert' from Tower. Cross checked instruments and appeared OK; shortly thereafter glideslope fluctuated almost full range and Captain executed a go around due to unreliable glideslope indication. Landed uneventful after go-around.We heard after the fact that there had been several reports by preceding aircraft that the glideslope appeared off. It would have been very helpful to know this information earlier in order to brief and setup for glideslope out of service approach or LNAV/VNAV approach. Also heard that an aircraft in or near the protected area may have caused the glideslope problems. Pass the word and protect the ILS areas during IMC operations.
A B737-800 crew executed a go-around in IMC conditions after ORD Tower reported a LOW ALTITUDE ALERT and subsequent full range Runway 28R glideslope fluctuation.