During final approach to sfo in weather; the glideslope became intermittent. Flight crew executed a ...

Narrative:

The first officer (first officer) was the pilot flying the ILS 19L into sfo. The weather there was IMC with strong winds at about 30 knots gusting to about 40 knots and rain. He captured the localizer and glide scope for ILS 19L while on the auto pilot. Everything seemed normal till just outside of rogge intersection when I notice a yellow line through the glideslope on the [flight computer].I waited a second to see if it was momentary loss of the electronic glide [slope]. As I was just about ready to tell the first officer I saw the autopilot kicked off. I thought he turned it off; but later I found out it was an uncommanded disconnect. I then saw that I got my glideslope back and the first officer was still having some problem with his side.I took over the plane at that moment and notice we were about a dot and a half high on the glide [slope]. I slowly pulled back power and lowered the nose and got to one dot high but I could not get any closer because our target airspeed was 145 knots and because of the gusty winds I could not push the nose down further in fear I can over speed the flaps with the airspeed bouncing around because of the winds.I did see the runway but did a go around at about 1;000ft. ATC did ask us why we went around I told him we were not stable for the approach. Later on while being vectored back for the ILS; I also told ATC that we lost the signal to the glideslope and that coupled with the winds /weather was why we went around. We notice on the radio another aircraft asking about the glide scope it seems that they lost the signal momentaryarily too. We then did a second approach with no loss of glideslope and landed in sfo safely.

Original NASA ASRS Text

Title: During final approach to SFO in weather; the glideslope became intermittent. Flight crew executed a go-around and landed on the second attempt. Other crews commented about the quality of the ILS signal.

Narrative: The First Officer (FO) was the pilot flying the ILS 19L into SFO. The weather there was IMC with strong winds at about 30 knots gusting to about 40 knots and rain. He captured the localizer and glide scope for ILS 19L while on the auto pilot. Everything seemed normal till just outside of ROGGE intersection when I notice a yellow line through the glideslope on the [flight computer].I waited a second to see if it was momentary loss of the electronic glide [slope]. As I was just about ready to tell the First Officer I saw the autopilot kicked off. I thought he turned it off; but later I found out it was an uncommanded disconnect. I then saw that I got my glideslope back and the FO was still having some problem with his side.I took over the plane at that moment and notice we were about a dot and a half high on the glide [slope]. I slowly pulled back power and lowered the nose and got to one dot high but I could not get any closer because our target airspeed was 145 knots and because of the gusty winds I could not push the nose down further in fear I can over speed the flaps with the airspeed bouncing around because of the winds.I did see the runway but did a go around at about 1;000ft. ATC did ask us why we went around I told him we were not stable for the approach. Later on while being vectored back for the ILS; I also told ATC that we lost the signal to the glideslope and that coupled with the winds /weather was why we went around. We notice on the radio another aircraft asking about the glide scope it seems that they lost the signal momentaryarily too. We then did a second approach with no loss of glideslope and landed in SFO safely.

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.

Attributes
ACN	1337572
Time
Date	201603
Local Time Of Day	0601-1200
Place
Locale Reference	SFO.Airport
State Reference	CA
Environment
Flight Conditions	IMC
Aircraft 1
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Flight Plan	IFR
Component
Aircraft Component	ILS/VOR
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 150 Flight Crew Total 10082 Flight Crew Type 9235
Person 2
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Inflight Event / Encounter Unstabilized Approach Inflight Event / Encounter Weather / Turbulence

During final approach to sfo in weather; the glideslope became intermittent. Flight crew executed a go-around and landed on the second attempt. Other crews commented about the quality of the ILS signal.