Air carrier flight crew reported receiving a caution obstacle warning message on final approach despite being on the glidepath and PAPI and landed without any other issues.
Synopsis
Air carrier flight crew reported receiving a caution obstacle warning message on final approach despite being on the glidepath and PAPI and landed without any other issues.
Narrative
We were going into LGA on the RNAV Z for Runway 31. The winds were 32 gusting to 40. Multiple aircraft were going around due to wind shear. I was the pilot flying and my CA was the PM. Once we got cleared for the approach and we were around 1;200 to 1;000 feet when I decided to turn off the autopilot because the autopilot was struggling to keep straight and was lagging due to the updrafts; downdrafts; and high winds. I remained on PAPIs; two red two white and on glidepath the entire approach. I was pretty focused on keeping the plane in a stable manner and staying on the autothrottles to keep our speed on point. Due to the updrafts and downdrafts the vertical speed and airspeed were fluctuating and I was responding and correcting. Around 3 miles we receive a caution obstacle message in yellow. I corrected and stopped the descent momentarily. I believe we got this because of the winds and turbulence. Both me and my CA saw we were on PAPIs and on glidepath during this caution message. We landed safely without any other messages and continued to the gate. Once at the gate we both looked up the SOPs and confirmed that we only saw and heard caution obstacle.
Second reporter narrative
We were flying into LGA. The FO was the PF. We were performing the RNAV Z 31. The winds were gusting up to 43 kt. from the west. To our knowledge they were slowly letting aircraft in due to multiple aircraft in a row going around due to windshear. Approach vectored out to the final where we were encountering shifts in the wind constantly that had the planes airspeed fluctuating quite a bit. Right before we started down on the glidepath Approach gave us the altimeter reading one more time. We ensured it was properly set in our altimeters again at this time. We started down on the glidepath as we saw another aircraft in front of us go around due to windshear. We continued down the approach with the plan on performing a windshear recovery whether it was a caution or a warning. My FO stayed on top of the autothrottles to ensure they weren't lagging behind and causing us to get too slow or fast as we descended. Approximately 3 miles out we got a 'caution obstacle' with a yellow GRND PROX message; to which my FO immediately and appropriately reduced her descent rate even though we were on glidepath and had two red and two white on the PAPI. We responded as the SOP said to do for a 'caution obstacle.' We were encountering +15 to -10 the entire descent which we imagine caused the airplane to think we were sinking even though we were perfectly on the glidepath and on the PAPI. We landed without any other issues and taxied to the gate. During debrief we covered the SOP policy on a 'caution obstacle' again and confirmed that we both heard 'caution obstacle' and saw a yellow GRND PROX message. We were both very focused on the approach due to the winds and multiple people going around.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.