Air carrier flight crew reported receiving a brief obstacle warning during visual approach at night. Flight continued approach and questioned whether a go around should have been performed.
Synopsis
Air carrier flight crew reported receiving a brief obstacle warning during visual approach at night. Flight continued approach and questioned whether a go around should have been performed.
Narrative
Operated [a flight] to SAT on Day 0. I was acting as PM (Pilot Monitoring) on this leg. SAT was advertising visuals to runway 13R and upon contacting approach control; we requested vectors for ILS 13R. The controller responded that she would vector us for the ILS 13R and proceeded to descend and vector us as expected. The controller stated that she would vector us to the new waypoint on the approach just outside of the FAF ALAMO. On our base leg at 3000 msl; the controller asked us if we had the airport in sight. I had a full visual with the runway and PAPI in sight and told the FO (First Officer) as such. I replied yes to her inquiry and she proceeded to clear us for the visual to 13R. We had briefed the ILS with visual and were set up properly for either the visual or the ILS and since we were already slowing and configuring it made sense to accept the clearance. The leg segment altitude is 2200 msl and that was set in the MCP (Mode Control Panel) and we began our descent to the glide slope intercept altitude of 2200 msl. When we were level at 2200 msl and just as we were beginning to intercept the 13R localizer; we had a very brief and momentary CAUTION OBSTACLE aural alert and message on our PFD (Primary Flight Display). While reading the message and taking a moment to assess; the message was now gone and we were turning onto the localizer level at intercept altitude. Once again; we as a crew assessed the situation; verified our situational awareness; could see the lighted tower below us visually; we continued the approach and landed uneventfully. After our shutdown checklist; we both had a lingering feeling that maybe even though the caution message was so short in duration; we were required to execute the CFIT maneuver regardless. After reviewing the procedure and requirements for executing the maneuver; even though we had the tower we believed to be the obstacle in sight; we were required because it was still NIGHT to execute the CFIT maneuver. Since the CAUTION message was so short in duration; I believe I used that information as a major factor in my decision making process. Before we had a chance to begin the CFIT maneuver; the CAUTION message was gone. Every situation has its own specific nuances; but in retrospect; to follow our procedures fully; we should have executed the CFIT maneuver even though the message would have been gone already when we would have began the manuever. I remembered the procedure for CAUTION OBSTACLE incorrectly. It was still NIGHT; and even though we had visual contact and confirmation with the obstacle; a CFIT maneuver would have been required. Only in DAYLIGHT should we have continued with the same conditions.
Second reporter narrative
First officer pilot flying to SAT 13R. We had requested radar vectors to the ILS and the controller said to expect that but we were cleared the visual on a left base leg between NUGIT and ALAMO (the FAF). I was at 3;000 and set 2;200 (FAF altitude) in the window and continued to configure and descend. While intercepting the final course; the caution obstacle aural alert sounded once. We were VMC with the runway in sight and the only obstacle was a tower that was clearly illuminated. We were well clear of the tower and both verbalized it was in sight. The approach and landing continued uneventfully. After landing we looked in the AOM and found I should have performed the CFIT recovery maneuver because it was night. To avoid getting in that position; I should not have accepted clearance for a visual approach when I was expecting and preferred vectors to an ILS. Also; I think all of the simulator CFIT training had been obvious cases; like flying toward a mountain. When I have heard whoop whoop; pull up in the sim; there is no doubt in my mind that I need to immediately perform CFIT and there is no decision lag. When I heard caution obstacle in the aircraft in VMC while flying my assigned vector from ATC to the published ILS final approach course and not descending below the approach plate altitudes; I did have a decision lag. What? Am I supposed to go around; do CFIT; or just spot and avoid the obstacle? Ive looked at that table numerous times and I made the wrong choice. I wont do it again.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.