Air carrier flight crew reported ATC advised of a low altitude alert during approach to land.
Synopsis
Air carrier flight crew reported ATC advised of a low altitude alert during approach to land.
Narrative
VFR conditions. I was the PF (Pilot Flying); FO (First Officer) was the PM (Pilot Monitoring). PM had initially set the ILS 36R in the FMC as a back up to the briefed visual approach. Prior to waypoint BOWTZ (the final waypoint on the arrival with a 4000 ft. crossing altitude); ATC gave clearance to descend to 2000 ft. PF selected Level Change; verified with PM and continued descent. Captain (PF) then asked FO to request the RNAV A Approach as a backup for the briefed visual approach. ATC cleared us the RNP Z 36R Approach. RNAV approach was loaded in FMC and briefed as the backup to the visual approach. Prior to the IAF waypoint (BOWTZ); I failed to select/ confirm VNAV; leaving the vertical mode in Level Change. I then set zeros in the MCP altitude window thinking more of a visual approach verses the RNP. At waypoint MYOPE; Tower called a low altitude alert. We were at 1800 ft. MSL with a minimum of 2200 ft. at MYOPE per the approach plate. Vertical deviation was immediately corrected and the approach/landing was continued uneventfully. Weather was clear and we were visual with the field the entire approach. [Automation Management] breakdown with Pilot-to-Pilot communication. There was some initial distractions with Approach Control having difficulty understanding FO's radio transmission saying the radio was scratchy; resulting in a brief discussion between the FO and me on transmission clarity. PM was also distracted with a frequency change that disrupted [Automation Management] as well as the late change to the RNP backup versus the ILS. PF complicated a simple visual approach by task loading the PM with the late ILS to RNP backup. [Automation Management] must be brought to a conclusion despite interruptions and distractions and additive conditions. Minimize the risk by planning and sticking to the plan. I take full responsibility for late changes; task loading and not using [Automation Management] to its entirety.
Second reporter narrative
VFR condition. Captain Pilot Flying; I was Pilot Monitoring. I had programmed the ILS 36R as backup for a visual approach on the ground [prior to departure]; but en route; the Captain elected to change it to the RNP 36R. It was correctly programmed and briefed. We were given a descent to 2000 ft. and Captain selected LVL CHNG. It was clear and I announced I had the airport in sight. He acknowledged. There was no distractions of note; and we were cleared for the approach. 1600 ft. was set and verified. LVL CHNG was still selected. We were sent over to Tower; and I changed the frequency and looked up Ground frequency. I checked in and Tower cleared us to land. Captain stated; 'It's not slowing down as I expected;' at which time I said; 'It's still in LVL CHNG.' Realizing the mistake; he called; 'Gear down;' to slow up as Tower called to advise us we were low on the approach by MYOPE fix. Approximately 1800 ft. I asked to be cleared for the visual; which we got. At no point we're we unsafe or low; compared to a visual approach which I believe was stuck in my mind; so I didn't notice the deviation. The remaining approach and landing was uneventful. I should have suggested VNAV mode rather than LVL CHNG; which would have negated the entire deviation.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.