Air carrier flight crew reported receiving a GPWS terrain warning on descent into BUF in night IFR conditions.
Synopsis
Air carrier flight crew reported receiving a GPWS terrain warning on descent into BUF in night IFR conditions.
Narrative
Going into Buffalo NY we were getting vectors for the ILS to Runway 5. I was the PF (Pilot Flying) the Captain. We briefed the surrounding terrain noting the highest obstacle and the associated MSA which was 3900 feet for that sector. We were cleared to descend to 4000 and reaching 5000 reduce speed from 250 to 210 kt. I was using descent mode function of speed mode prior to 5000 feet. Reaching 5000 I entered vertical speed mode and started to scroll up the descent rate to start the speed reduction to 210. Almost immediately we received a 'too low terrain pull up' oral. Having briefed the terrain I had a slight moment of surprise knowing that we should be safe of terrain. But then immediately disengaged the autopilot and initiated the escape maneuver. We leveled momentarily at 6800 feet and reported to ATC then resumed ATC vectors and altitudes and landed safely. The whole time of the event we were in IMC. In hindsight I believe our descent rate must have been what triggered aural. Noting from memory I do not believe our VS in speed mode was greater than 1600 fpm.Cause: I believe it was due to the decent rate triggering the terrain pull up. All charts and from what I saw on the terrain page we were never in danger of contacting the depicted obstacle and never went below the published MSA.Suggestion: I feel that sim training helped me revert to basic instinct and perform the escape maneuver.
Second reporter narrative
GPWS\terrain warning. During descent into BUF at ~4800 ft. after being cleared down to 4000 ft. by approach we received a GPWS warning and executed the proper procedure. We had briefed the MSA and ATC advised that their MVA was not that low so we confirmed that there was no terrain on any charts that should have tripped it off. Captain was pilot flying and executed maneuver and I was Pilot Monitoring and advised ATC. Cause: ATC cleared down to 4000 ft; we briefed the MSA on the approach and we had all green on the terrain. While going though 5000 they had us slow to 210 during the slow down about 4800 ft we got the terrain 'pull up'. Capt pulled up and I as pm advised ATC. Who informed us that they had an MVA of 3000 and our MSA on our charts was 2900 so we confirmed there was no terrain in area.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.