Air carrier flight crew reported while conducting an Autoland the aircraft did not begin its descent. While correcting they became unstable and received a Glideslope Alert and Altitude Alert from the Tower due to descending below the Glideslope.
Synopsis
Air carrier flight crew reported while conducting an Autoland the aircraft did not begin its descent. While correcting they became unstable and received a Glideslope Alert and Altitude Alert from the Tower due to descending below the Glideslope.
Narrative
I was the Captain/non flying pilot (NFP) on Aircraft X from ZZZ1 to ZZZ. The aircraft required an Autoland for currency; so we briefed the arrival; approach; and Autoland Procedural Guide for the ILS XXR. Approach vectored us onto the localizer; and we joined the course via the LOC Only button on the NAV page of the FMS. Once cleared for the ILS XXR approach the flying pilot (FP) selected APPR/LAND and I called LAND ARMED. We were instructed to maintain 170 kts. until ZZZZZ which is the final approach fix. Autopilot2 was the active Autopilot. As we were configuring and approaching ZZZZZ we were cleared over to the Tower. I called the Tower and advised them that we were conducting an Autoland. They confirmed the critical area was cleared and we were cleared to land XXR. At this point we were about to cross the final approach fix and looked over at my approach chart to confirm GS crossing altitude. I looked back at my Primary Flight Display (PFD) and immediately saw that NAV2 was now engaged; and we had not started to descend to capture the glidepath. I stated to the FP that you need to reengage APPR/LAND and start descending. We were on GS path at this time; but the aircraft was still in level flight. The FP tried to use vertical speed to start descending to capture the glidepath from approximated a 1/2 dot above the path. Due to trying to slow down and descend it was making it difficult to capture the glidepath from above. I felt we could safely establish a stabilized approach and land if we quickly started our descent. I could see the ground with good visibility of approximately 3 miles. I asked for the FP to disconnect Autopilot and hand fly the aircraft which would expedite capturing the GP with a normal descent rate. I continued with the landing checklist at this time. When I looked back at the PFD; I realized our descent rate was too high and ask for the FP to pitch the nose up to shallow our descent. I believe the FP was trying to be smooth on the controls as we descended below the glidepath very quickly. The G/S alert went off; as I was calling for the FP to GA. At about the same time the Tower advised us of a low altitude alert. I told them that we were going around; and they gave us runway heading up to 3000 ft. We flew the missed approach as instructed and were vectored back around for the ILS XXR approach. We landed without incident. In the future I will wait until I see the GS capture before looking at my approach plate to confirm the altitude is correct. I will also call for the GA sooner.
Second reporter narrative
I was the First Officer/pilot flying (PF) on Aircraft X from ZZZ1-ZZZ. The aircraft required an Autoland for currency; so as the flying pilot I briefed the arrival; the approach; the missed approach procedures and the Autoland Procedural Guide for the ILS XXR. ZZZ Approach vectored us onto the localizer; and we joined the course via the LOC Only button on the NAV page of the FMS. Once cleared for the ILS XXR approach I selected APPR/LAND and the Captain called LAND ARMED. We were instructed to maintain 170 kts. to ZZZZZ which is the final approach fix on the ILS XXR.At this time we were finishing up configuring. The Captain switched to Tower; he notified Tower we were performing an Autoland. Tower reported back the critical area was cleared. I looked down at the FMC and the Captain announced we are not descending. So I started to use the V/S to get the airplane to descend. That was taking too long; so I disconnected the Autopilot; pushed the nose over to catch the G/S. My descent rate was too excessive; so I pulled up smoothly. We received a G/S alert and at the same time the Captain called a GA. At the same time Tower called out a low altitude alert. Once we performed the GA; Tower gave us runway heading up to 4000 ft. We flew another ILS to XXR and landed without incident. What I learned from this; the company requested an Autoland for the aircraft. Since this is not a routine; maybe if I had configured early I would have been looking at my Primary Flight Display (PFD) watching the G/S. For now on if and when I or the Captain arm the approach. I will keep my eyes on the PFD watching to make sure the aircraft descends. Also anytime the aircraft does not descend when you want it to in an approach; disconnect the Autopilot first and leave the automation alone. Just hand fly right away.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.