B737-700 flight crew reported they received a Ground Proximity Warning and Low Altitude Alert from the Tower while conducting a Charted Visual Approach.
Synopsis
B737-700 flight crew reported they received a Ground Proximity Warning and Low Altitude Alert from the Tower while conducting a Charted Visual Approach.
Narrative
On arrival to ZZZ; we were cleared for the Park Visual Runway XX at night. We were configured and stabilized at the 1000 ft. call. As the aircraft was in the final arcing left turn; just prior to the 500 ft. callout to the runway; we received a caution obstacle call out. Simultaneously; the ZZZ Tower called us with a Low Altitude Alert; which we acknowledged; and the First Officer disconnected the autopilot and auto-throttles and performed a smooth maneuver to stop the descent and start a climb. The First Officer and I were both sensing that the approach started to look low to us; in reference to the runway; and the runway VASI information showing us a little low. The maneuvering would not have caused the Passengers any concern.The approach remained stabilized and we agreed to continue to the runway and land; since we had the runway and VASI information. The landing was on speed and in the Touchdown Zone. Taxi to the gate was uneventful. After discussing the approach with the First Officer numerous times; (that night and the next day) to go over what might have happened; or if we missed something; we could not conclude that we knew the exact cause. However; from our reviews; we both saw that the Flight Director was 'centered' throughout the approach. We both cannot be 100 [percent] certain that when this event occurred; that the FMA (Flight Mode Annunciator) was in VNAV Path or another mode that could have caused the aircraft to drift too low. When I got to the hotel that night; I called the [Company] Chief Pilot and explained what had happened; and to verify that the FDAP (Flight Data Analysis Program) data would be captured that would help in this event.
Second reporter narrative
On arrival to ZZZ; we were cleared for the Park Visual Runway XX at night with the First Officer flying the approach. We were configured and stable at the 1000 ft. call. Around the base turn with autopilot and auto-throttle coupled; after (base turn) but prior to the 500 ft. callout; we both noticed that we looked low visually. The next events happened in rapid succession; so I'm unsure of the order; but I believe the ZZZ Tower called us with a Low Altitude Alert; which we acknowledged. I; [the] Pilot Flying; disconnected the autopilot and auto-throttles and performed a smooth maneuver to stop the descent and start a climb. During that maneuver; we received a Caution Obstacle Alert from the GPWS. The maneuvering would not have caused the Passengers any concern. The approach remained stabilized so we agreed to continue to land since we had the runway and VASI information. The landing was on speed and in the touchdown zone; and the taxi to the gate was uneventful.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.