B737 flight crew reported receiving a low altitude alert from ATC during approach. Flight crew corrected and continued approach.
Synopsis
B737 flight crew reported receiving a low altitude alert from ATC during approach. Flight crew corrected and continued approach.
Narrative
FO was PF and I was PM. Arrival/approach briefing and preparation was good and completed prior to TOD. Our STAR into ZZZ was the ZZZZZ; but we were vectored off the arrival to the east of ZZZ and for a visual approach. Weather at ZZZ was completely day VMC with higher clouds at the time. Consequently; we never lost visual on the airport or terrain throughout the approach. All was normal until we received the visual approach clearance. Our visual approach clearance to XXR was a little different because it occurred with a vector that would have us intercept final after ZZZZZ [fix]. This confused the FO where he wasn't clear on what or if any certain altitudes needed to be maintained (he didn't verbalize this in flight). We were also told to stay visual with another aircraft in front of us and landing XXL.After the approach clearance; the FO asked for TDZE to be set. I told him we couldn't do that because LV CH was currently selected. He then asked me to select V/S and 900 FPM down. After I selected V/S 900 FPM down for him; he then asked for TDZE to be set. While I wouldn't have made this MCP (Mode Control Panel) choice; I didn't want to fly the airplane for him; and since it wasn't an SOP violation; I did as he asked and figured we could debrief other options after landing. I knew 900 FPM down was too much; but at this point; I thought it was best to let him figure that out and make corrections on his own.From here; it was a case of 'how far do you let an FO go before you direct another action?' Quite simply; I waited too long because I didn't account for the fact I was PM and would become more distracted by ATC comm; setting flaps; setting speeds; and doing the Landing Checklist as we got closer to the airport. Additionally; I was also distracted in staying visual with the aircraft in front of us landing XXL.The FO crossed abeam ZZZZZ about 300 ft below the 1800 ZZZZZ charted altitude. I did notice we were below GS at this point but chose not say anything yet and let the FO correct on his own. Unfortunately; the debrief revealed that the FO was 'tunnel vision' on the FD (Flight Director) and not looking at the PAPI or the GS indications. Since he also got behind in configuring the aircraft; I became concerned with stabilized approach criteria and prioritized proper gear/flap configuration over the fact we were well below GS. I reported 1000' and the need for Flaps 30 since we were still at Flaps 25. The landing checklist was completed late at about 800 ft. Keep in mind we were VMC; never slow and always had airport and terrain easily in sight. That said we were now showing full scale deflection below GS. Now at 800 ft is when I became very verbal and directive stating the need to level off and capture the GS before 500' or we would have to go around. Essentially; the fact I was visual with airport/terrain combined with my concern over making the 500' gate; caused me to forget how grossly we were in violation of the WARNING in both the FOM and FM (Flight Manual) regarding the need to follow a normal GS after the visual approach clearance. We fully met stabilized approach criteria by 500' and the remainder of the approach/landing was without incident or concern.Looking back; it's easy for me to say that I needed to speak up much earlier and be more directive abeam ZZZZZ. However; I also know the previously mentioned PM approach phase duties/distractions; and me being awake for over 13 hours; hindered my actions.This was thoroughly debriefed between me and the FO.
Second reporter narrative
We were being vectored to a visual approach for Runway XXR at ZZZ via a right downwind. At 3000 feet msl we were given a vector to intercept final inside of the XXR ILS final approach fix and cleared for a visual approach. I was flying at this point and requested a vertical speed descent of 900 fpm recognizing that we would intercept the final course after ZZZZZ and knowing that the GS crossing point was 1800 feet MSL at ZZZZZ. I wanted to ensure that I was not too high as I intercepted final knowing the glide slope would be below 1800 feet since the intercept vector placed us between the known altitude of 1800 and the end of the runway. I continued to follow Flight Director guidance on a 900 FPM descent until reaching 1000 feet AGL at which point I slowed my descent but continued. I did not recognize that GS had fully deflected above but was fully configured crossing through. I then continued to shallow out my descent recognizing that the PAPI guidance was showing 4 red in order to correct back to path. Concurrently; we received a low altitude alert from Tower as I shallowed and pilot monitoring also directed a level off. We leveled off just above 500 feet AGL. We continued to remain level until intercepting normal PAPI guidance of 2 red and 2 white. The remaining approach and landing was uneventful.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.