Air carrier flight crew reported receiving a GPWS alert and a low altitude alert from ATC on a nighttime River Visual approach to DCA.
Synopsis
Air carrier flight crew reported receiving a GPWS alert and a low altitude alert from ATC on a nighttime River Visual approach to DCA.
Narrative
We were cleared for the River Visual to Runway 19; and I loaded in LDA-Z as a backup. I began to track the fixes on the LDA approach but decided to click off the autopilot and hand fly the River approach. Around 900 [ft.]; we got a ground obstacle warning; but 1) we were still over the river; and 2) using the 300 [ft.]/1NM rule; it seemed like I was on a good descent path. So I turned a little more to the left to avoid the buildings on the right side of the river; but that distracted me enough to where we received a low altitude alert from DCA Tower. My FO (First Officer) said we should have crossed the Rochambeau Bridge at 600 [ft.]; but he said we were between 350 [ft.]-400 [ft.]. I pulled back a bit; but we were still low. I could not see the runway and asked my FO if he saw it. He said he did; and then I got it in sight. Tower also asked us to square the base. This made for a fairly sharp bank angle (20-30 degrees); and I really need to stay further to the right of the bridge so as to make the turn less steep. We still had 4 red PAPIs; which should be a go-around; but I corrected and got some white PAPIs. The landing was smooth and uneventful; but the experience no doubt frightened people on the aircraft.Experience really is the best teacher. I have a very limited number of night time approaches with the River Visual; and I believe that more night flying to Runway 19 will make any pilot feel much more comfortable. Flying the River Visual in the daytime is one thing; flying it at night is much more difficult. I should have been looking for the airport sooner; but I was preoccupied with my descent rate and not getting violated by entering prohibited airspace (which is probably on a lot of pilots' minds). It was also pretty busy and very difficult to see the runway; which exacerbated the situation. But things snowballed with the ground obstacle warning. If I had to do it again; I would have included the airport in my scan (which I didn't do); stayed just a bit higher; and finally I would have started slightly turning right over the George Mason Bridge rather than set too steep of a bank angle at that low of an altitude.
Second reporter narrative
We had a shallow approach into DCA and on the approach we had an obstacle warning at 800 [ft.] between 4 DME and 3 DME from DCA. The recommended altitude was 900 ft. Our approach angle shallowed from the Key Bridge. We crossed Roosevelt Bridge around 700 feet and that is where we received a low altitude warning from ATC around there. [The Captain] shallowed the descent between the bridges [and] we made a shallow approach from the Roosevelt Bridge. We descended to 350 [ft.] to 400 [ft.] over Rochambeau Bridge and then I saw 4 red on the VASI. I did not verbalize the altitude deviation callouts aloud. I was thinking of calling for a Go Around but [then] I saw an airplane depart and we would have been an unsafe traffic separation.I had the airport in sight the entire approach. The low light following the Potomac River led to [the Captain] becoming disoriented. The lateral approach along the river was fine but the rate of descent was too steep causing us to go below the VASI. We had an obstacle callout before Key Bridge at 900 feet around downtown Arlington; VA. I had verbalized; 'Too Low' but [the Captain] did not hear me. I had to point out the runway to [the Captain]. What I would do differently is add my audible cues I used to put the 1100 [ft.] MDA at JEVGA on the LDA Y 19 as an altitude reference on previous flights to DCA. This has helped me on the River Visual 19 before.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.