Air carrier flight crew reported they descended below glidepath on approach and received a low altitude alert from ATC.
Synopsis
Air carrier flight crew reported they descended below glidepath on approach and received a low altitude alert from ATC.
Narrative
In a non VNAV 700; flying the GPS Approach to XXL ZZZ which did not have PAPIs or VASIs. ATC kept us high for this approach as there were multiple aircraft in the vicinity. Cloud bases were broken and around the same altitude as the final Altitude on the approach. We were cleared for the approach inside ZZZZZ with vectors to final and cleared to an altitude until established. It's been a good amount of time since (FO) First Officer flew a Continuous Descent Final Approach (CDFA) approach; and got behind the aircraft; so I coached. I might have thrown him off by telling him to fly in NAV not APPCH; but I had to remind to set next altitude and that he would need 1500 fpm to get to the next altitude by the Final approach fix. I said 'point 2' and we were going through landing checklists or talking to ATC because next thing I know I see that we're at 1700 FPM VSI; low; and at the same time ATC is telling us we are registering a low altitude event. I tell the FO to go around but it doesn't register immediately so I walk him through the go around. As we go around ATC asked the reason for the go around and I said unstable. We go around and get the same exact set up for the approach from ATC; but this time the FO was prepared; setting up for the approach early; and making sure we only go 700 FPM descent after the final approach fix. The second approach and landing was stable and uneventful.The FO was behind the aircraft; was reminded to go from heading to NAV (or APPCH) then set next altitude; then set minimums after arriving at 2000. Possibly rolled the vertical speed knob too quickly; was paying attention to the Flight director and not the snowflake. Without the VASI or PAPIs had no visual frame of reference if we were high or low.Suggestion: Preparing for the approach a little earlier; understanding the descent rate needed before the FAF; and only doing 1 click at a time on the vertical speed knob while flying with autopilot. I told him to practice more CDFA approaches where the autopilot isn't coupled to VNAV.
Second reporter narrative
We were flying a non-VNAV CRJ-700 into ZZZ on the RNAV (GPS) Runway XXL approach; which does not have PAPI or VASI guidance. ATC kept us high due to multiple aircraft in the vicinity. Cloud bases were broken and near the same altitude as the final approach altitude. We were cleared for the approach inside ZZZZZ and vectored to intercept final at an altitude until established; with a published step-down altitude prior to the FAF.Because of the late vector and high intercept altitude; a standard CDFA profile was not possible. While configuring for the descent; the vertical speed was inadvertently set at approximately -1;700 FPM instead of the intended ~700-800 FPM for our approach speed. This resulted in descending about 300 feet below the published altitude near the FAF. ZZZ Tower issued a low altitude alert. Upon hearing this; we immediately initiated a missed approach.On the second attempt; we received the same vectoring but were better prepared. Vertical speed was correctly set at ~700 FPM after the FAF; and the approach and landing were stable and uneventful.Contributing Factors:Late vector to final with high intercept altitudeIncreased workload in IMC near FAFIncorrect vertical speed setting in a non-VNAV descentCorrective Actions:Immediate missed approach upon receiving low altitude alertEnsured correct vertical speed setup for the second approachWill request earlier descent or extended final in similar situations to enable CDFAThe combination of flying a non-VNAV aircraft; being vectored high and close to the FAF; and operating to a runway without vertical guidance increased workload and complexity. My proficiency with non-precision; non-CDFA approaches is less exercised due to their infrequent use in regular operations. This contributed to the incorrect vertical speed setting and subsequent low altitude event.As ZZZ1 continues to operate more CRJ-700 aircraft without VNAV capability; pilots should ensure their skills in flying non-precision approaches--particularly those without vertical guidance--remain sharp. These approaches are relatively uncommon; especially to runways without ILS; so targeted practice and review are beneficial. I plan to intentionally incorporate more of these approaches during training events or when operationally feasible to maintain proficiency.
More incidents for this aircraft family →
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.