Air carrier crew reported receiving a low altitude alert from ATC while on the initial approach when above the glide path on a training flight at night. The Captain made the vertical correction and stabilized the aircraft and landed.
Synopsis
Air carrier crew reported receiving a low altitude alert from ATC while on the initial approach when above the glide path on a training flight at night. The Captain made the vertical correction and stabilized the aircraft and landed.
Narrative
Conducting the RNAV GPS X- RWY 31 into LGA. Capt was PF; I was PM. On the final turn around DCTRK ATC issued a low altitude alert to us on short final. We continued in for a normal landing.In the approach briefing Cap; asked to be notified of the how she was doing vs the 'check altitudes' listed on the plate. Through DRRYL I called slightly high we were about 1200 ft on the altimeter; I saw a correction back down. I noted on profile at KEYTH. As we began the final turn ATC issued a check altitude for our aircraft. I looked at the altimeter; called look slightly low; but still on profile; I also noted the PAPIs which were now coming in sight as we passing through 30 degrees to runway heading were showing 3 white. Once lined up with the runway heading we still had three white. The Cap made a correction; then made a touchdown normally in the touchdown zone.Cause: I think an excessive sink rate might have led to a trip of the low altitude alert.Suggestions: RNAV would probably be easier having the final extended out by 500 feet. And possibly limit its use at night.
Second reporter narrative
We flew ZZZ-LGA and it was our last leg of a 4 day trip; and it was a 3 leg day. I was doing OE (Operational Evaluation) with a new hire and we had delays the entire day because of ATC flow; but we had made up lost time by not having long sits and so we were arriving about 45 minutes later than scheduled; landing around XA:30 pm eastern. I took this last leg since we were going into LGA and doing the RNAV X 31 late at night. Beginning the approach everything looked great; we had heavily briefed threats for the flight and briefed the RNAV X super in depth since it was my Foster second time doing it; first at night. I began the approach and my FO was being a good active PM and calling out my altitudes. The wind was 320/330 at 13 which I had briefed how it would affect our flight path. Right around the turn over the lake just past DRRYL is where I became slightly high as I was turning inbound; and I believe my turn was not shallow enough. At KEYTH I was at 834 feet which should be at 782 feet so just 52 feet high. I made a correction but my correction was too steep; because my FPM increased to 1.1; the increased descent rate in combination with a steeper turn than needed caused me to be slightly low. I saw the PAPIs and made immediate corrections and verbally announced my corrections. My FO called out that my altitude was right on and we continued. We heard 'low altitude alert' from ATC but at that point I was corrected and I asked the FO if that was for us. We continued the approach because it was stable and I was on the PAPIs. After landing I had my FO confirm if that altitude alert was for us; and they confirmed it was. We determined that I must have turned slightly inward of the lateral navigation because my wind correction was too much; and that in combination with my temporarily increased descent rate triggered the low altitude alert.Cause: We determined that I must have turned slightly inward of the lateral navigation on RNAV X 31 because my wind correction was too much (320/330 at 13); and that in combination with my temporarily increased descent rate (1.1 for more than 5 seconds) triggered the low altitude alert. I later confirmed this with flight pulse. I've flown the RNAV X 31 many times into LGA and am comfortable with it. It had been a while since I had done it at night and my second time doing it with a new hire on OE. I felt like going into it I briefed it well; I honestly think that I just misjudged the visual cues at night and wasn't in tune enough with the lateral path like I am during day time.Suggestions: I do feel like we followed TEM (Threat and Error Management) and adequately briefed the approach to prepare for it. I think because it had been a while since doing it at night it threw my sight picture off slightly. Maybe when we practice this approach in the sims we also add in the night sight picture as well.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.