Narrative:

On approach to ZZZ; [I] experienced glideslope fluctuations with autopilot engaged. Around 600' the glideslope fluctuated down and flight director followed it enough to give a sink rate warning. Captain (ca) disconnected the autopilot and initiated go-around. Passing through 1;000 feet airspeed rolled back quickly and received a red windshear warning. Flew through the windshear with minimal loss of altitude and diverted to filed alternate.we were generally aware of weather approaching the area but nothing from our onboard radar indicated a threat to our safety. ATC also was unaware of imminent threat of windshear so we were all caught a little bit off guard by this event. The fluctuations of the glideslope also helped to destabilize our approach at a critical time. Use of the autopilot was also a factor in the cause for go-around.the approach had the feeling of a windshear training event in the sim; so we were primed to go-around; but didn't expect the sink rate warning as the reason for the go-around; and the subsequent windshear encounter. Typically; we will allow the autopilot to fly until visual contact is made with the runway. In this case; the autopilot following a fluctuating glideslope likely induced the sink rate warning and caused the go-around. It may have been wise to click off the autopilot before this happened. Also; more accurate information would have been helpful in making a decision to continue or abandon the approach; but the traditional threat indications like strong radar returns or windshifts/windshear warnings from ATC were absent. The good news is that our windshear training in the sim proved valuable to us in this event. Subsequent to our go-around; aircraft behind us were warned of the deteriorating conditions and were able to benefit from our experience.

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Original NASA ASRS Text

Title: EMB-145 Captain reported that they experienced glideslope fluctuations; the glideslope fluctuated down and flight director followed it and gave a sink rate warning.

Narrative: On approach to ZZZ; [I] experienced glideslope fluctuations with autopilot engaged. Around 600' the glideslope fluctuated down and flight director followed it enough to give a sink rate warning. Captain (CA) disconnected the autopilot and initiated go-around. Passing through 1;000 feet airspeed rolled back quickly and received a red windshear warning. Flew through the windshear with minimal loss of altitude and diverted to filed alternate.We were generally aware of weather approaching the area but nothing from our onboard radar indicated a threat to our safety. ATC also was unaware of imminent threat of windshear so we were all caught a little bit off guard by this event. The fluctuations of the glideslope also helped to destabilize our approach at a critical time. Use of the autopilot was also a factor in the cause for go-around.The approach had the feeling of a windshear training event in the sim; so we were primed to go-around; but didn't expect the sink rate warning as the reason for the go-around; and the subsequent windshear encounter. Typically; we will allow the autopilot to fly until visual contact is made with the runway. In this case; the autopilot following a fluctuating glideslope likely induced the sink rate warning and caused the go-around. It may have been wise to click off the autopilot before this happened. Also; more accurate information would have been helpful in making a decision to continue or abandon the approach; but the traditional threat indications like strong radar returns or windshifts/windshear warnings from ATC were absent. The good news is that our windshear training in the sim proved valuable to us in this event. Subsequent to our go-around; aircraft behind us were warned of the deteriorating conditions and were able to benefit from our experience.

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.