Air carrier flight crew reported receiving terrain and pull up warnings during final approach. Flight crew climbed the aircraft and continued approach.
Synopsis
Air carrier flight crew reported receiving terrain and pull up warnings during final approach. Flight crew climbed the aircraft and continued approach.
Narrative
We were on radar vectors for landing runway 24 into BHM and I was the pilot flying. While on a right base leg the aircraft sounded the audible whoop whoop; terrain; pull up. I immediately increased power; disconnected autopilot and began to pull back on the control wheel. Almost immediately the warning disappeared and everything was normal again. The event was cleared so fast I never made it past the climb detent and we only climbed a few hundred feet before I leveled the aircraft again. It was day VMC conditions; the terrain was clearly in sight as we were still approximately 1500 AGL and the airfield was in sight. After asking my FO if he was okay to continue we elected to continue the approach and landing without further incident. After landing we had a discussion about the event. We cross checked where we were in relation to obstacles and terrain and although we were slightly lower than ideal it should not have warranted the pull up warning. There was also no caution prior to the 'pull up' which leads us to believe it may have been an anomaly being either a 5G interference with the radar altimeter or a momentary GPS position error.Allow more of an altitude buffer even when on a visual approach with terrain and obstacles in sight.
Second reporter narrative
I was PM CA was PF. We were decending very slowly (approximately 200fpm) just north of the FAF for the RNAV 24. 2200 was the selected altitude as we were about to intercept the approach course at approximately 12 miles from the airport. The weather was dry VMC; and we had the airport in sight (we had previously been cleared for the visual 24 and were using the RNAV to back it up). Suddenly the master caution flashed once; and 'TERRAIN' was heard once; followed Immediately by 'WOOP WOOP PULL UP'. The CA immediately disengaged the autopilot; starting to pull back on the yoke; and advanced the thrust levers. Before he had even completed advancing the thrust levers (he was just hitting the climb detent) everything cleared. We had only climbed a maximum of maybe 500 feet. After noticing his quick reaction; I scanned out the window looking for obstacles; none were observed. After a quick discussion; we both agreed we were still close enough to the approach profile to safely continue. After landing much discussion was had trying to find a cause; we could not determine anything; as the tower near there was still several miles off and the system did not say 'OBSTACLE' at any time.Cause: Slightly low on approach segment caused an inadvertent GPWS warning. Possible aircraft database glitch or gps error caused the system to possibly trigger too early.Suggestion: Stay higher on this approach the we did on the event flight; and check the aircraft database for abnormalities.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.