A B737-800 crew executed a go-around in IMC conditions after ord tower reported a low altitude alert...

Attributes
ACN	1092182
Time
Date	201306
Local Time Of Day	1801-2400
Place
Locale Reference	ORD.Airport
State Reference	IL
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Person 1
Function	Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	ATC Issue All Types Deviation - Altitude Excursion From Assigned Altitude Inflight Event / Encounter CFTT / CFIT Inflight Event / Encounter Weather / Turbulence

Narrative:

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.

Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2013 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.

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.