B787 flight crew reported they descended two dots below the glide slope on a visual approach; citing automation mode awareness; fatigue; and workload as contributing.
Synopsis
B787 flight crew reported they descended two dots below the glide slope on a visual approach; citing automation mode awareness; fatigue; and workload as contributing.
Narrative
Our flight was delayed on departure due to ZZZ1 weather. The inbound flight diverted and arrived in ZZZ1 late. We had a 2-hour delay from XA25 to XC29. We were all pretty tired by the time we started the descent into ZZZZ. The captain was PM the FO was PF. The descent was a series of descend to altitudes with a VVI (Vertical Velocity Indicator). For example; descend to FL250 at 2500 FPM; continue descent to FL130 at 2000 FPM; speed 310. A high-speed descent was approved. Our arrival was the ZZZZZ for Runway XXL; high speed approved; the FO slowed speed from 290 to 270; then slow to 240 kts. Flaps 1. We descended thru the area with some storms and with minor course deviations. Before ZZZZZ we were cleared direct to ZZZZZ1 on LOC XXL on a very tight approach. Cleared to descend to 6000 ft; turn left heading 110 to intercept localizer; descend to 5000 ft. Then ATC apologized and said we had traffic off right side now we must level at 5500. I set the MCP (Mode Control Panel) altitude to 5500 and we quickly leveled there. We went above the glide path and got high. I extended ZZZZZ2. ATC asked us if we could get down; we discussed and agreed we could continue the approach. We were level at 5500. Then cleared for the approach; approach was selected. The captain set 5000 then the Relief Pilot said we needed lower and we set 3000 to capture. Fully configured with f30 gear; speed at 165kts; In visual conditions runway in sight. The tower offers a visual approach as the field was visible; the captain accepted. We were in visual conditions throughout the approach.We were high and in alt capture; the captain (PM); asked the FO(PF) to descend; the Relief Pilot also said to descend. The captain selected FLCH for the FO; the FO turned off the AP (Autopilot) and selected speed brakes. We were fully configured and at target speed by this point. We quickly got 2 dots below path down to 3000 ft and more slowly down to 2500 feet. The GS captured briefly; but we descended thru the GS and lost the vertical guidance bar in the PFD (Primary Flight Display) and the HUD. The captain directed FO to level off to recapture from below. Tower again offered visual approach we accepted visual approach. The tower asked if we were able to continue and we said yes. FO continued to slowly descend at 2-300 fpm but still below path. The captain and the Relief Pilot directed the FO to level off again. Glide path came alive at 2500 feet. We slowly got back within a dot of the path by 2000 ft (550 AGL). The tower asked if we were OK to land; we said yes. The landing was OK. We had a long debriefing after we set brakes at the gate.
Second reporter narrative
13'k 310 kts; some storms/TCU (Towering Cumulonimbus) in vicinity-minor deviations.Cleared to 6'; no speed.Started slowing thru 9'; slam dunk with short vectors.Cleared to 5500' f20 speed about 200.Held hi for tfc then twr asked if we could make it when cleared to 5'k; cleared the visual.Gr down slowed to 180kts; descent to capture; vfr; field in sight.Disconnected AP (Autopilot); Relief Pilot suggested 3'k for alt; capt rec flch to start down.GS capture about 2'k? Called for tdz but didn't decrease descent rate enough to maintain it.Capt called to lvl off; slowed descent to ~2-300 fpm but thought I had zeroed it. Capt repeated; again thought I'd leveled but still had slight descent; lo on glide path. Finally reintercepted path approx 800-1000'a; fully stable; on spd at 500'.Landing uneventful.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.