Air carrier flight crew reported receiving a low altitude alert from ATC and two glide slope warnings during approach. Flight crew pitched up to correct.
Synopsis
Air carrier flight crew reported receiving a low altitude alert from ATC and two glide slope warnings during approach. Flight crew pitched up to correct.
Narrative
First officer was pilot flying. We briefed for a visual approach including the mental model of appropriate altitudes and distances from runway when not directly using electronic guidance. I also added to his brief that the low sun position could also be a threat. Sunglasses and visor up.Pairing traffic on XXL added to the briefed threats; however we had significant separation ahead of that traffic which I had in sight and told FO it was not a concern; although he was remaining a bit right of course. ATC had also issued a very shallow intercept which they amended but still inside of FAF.Trying to continue with automation use; the aircraft leveled and soon thereafter the FO correctly disconnected autopilot. I reminded him that the cyan diamond indicated correct glide slope for vertical guidance; that we were trending high and cancelled the flight director. I double checked position of the pairing traffic; and then went to select green needles for the FO; which took an additional few seconds for me to locate V/L button on FO guidance panel. Immediately thereafter ATC issued a low altitude alert with simultaneous Glide slope" aural warning. I commanded he pitch up but we received a second glide slope aural warning before adequate corrective action. My lack of maintaining awareness of primary flight display for even a few seconds prevented my alerting the FO to the deviation before it worsened. The FO also did not vocalize at the time that the sun was making his view of not only the runway but he said the instrument panel difficult. Being over water also did not cue me that he suddenly began descending too rapidly. The FO has well over 1000 hours in seat and I had some complacency that he would again perform adequately as he had on earlier legs flown.Airline schedule; ATC and operational delays were also a definite contributor. It was the last day of a 4 day trip with 2 of the overnights being 10-11 hours and the 5th leg flown on a very tiring day. My prior trip finishing only 2 days earlier also had 2 overnights shortened to min rest 10 hours by operational delays. I need to maintain constant vigilance especially during critical phases of flight; query the FO if the situation becomes challenging and more assistance or input is needed. I already strive to maintain a very open communication; no ego style in the flight deck; and now I have another good teaching experience to relate how not speaking up when any flying pilot loses Situational Awareness (SA) is such a threat. "I can't see your controls" is not a show of weakness or failure. This event never became truly unsafe; but was an excellent reminder to me just how quickly a situation can deteriorate. I also do not think schedules should be created with 5 legs in and out of major airports on the last day of a 4-day trip. In my opinion; 12 hours should also be the minimum rest time on overnights. Especially for us regional folks who are required to fly such demanding schedules."
Second reporter narrative
Was vectored in the north side of Location X in anticipation of a turn to intercept XXR. Was given a heading (HDG) to fly and was flying the appropriate HDG and Flight Path Angle (FPA) with Autopilot (A/P) and Autothrottles (A/T) armed and active. Course and path were all standard for an approach to the Visual for XXR. While flying the given vectors and path for descent; the intercept course was intercepting the final course later than expected; because of this; the plane stopped its descent from the altitude pre-select. With the heavy workload from the approach; looking for parallel traffic; opposing traffic; watching the runway to clear; in the moment; the most appropriate action was to turn off autopilot and hand fly the airplane with the runway insight. During the turn to final with autopilot off; PF was temporarily blinded by the opposing sunset. With the sunvisor in place; and wearing non-polarized glasses; for about 5 seconds; PF had minimal forward sight. The plane was descending below course; and received an altitude warning as well as an altitude alert from ATC. The PM responded 'correcting' and helped to guide the PF back to a proper approach. The aircraft passed through the FAF configured and stabilized on a proper course and path; and landed successfully and taxi'd to the gate with no further incident.The most direct cause was the close in shallow vectoring accompanied by the sun causing temporary restriction of the forward view. Additional factors were the long duty day; currently on day 4 with multiple minimum rest overnights; having already flown 4 other flights (incident flight was flight #5) and having been on duty for over 12 hours at the time of incident.Consider the sun shining directly down the runway as a meteorological condition; not necessarily as a requirement for an IMC approach; but consider limiting short in vectors during VMC periods with the sun directly down the runway. Additionally consider the effect of a 5 leg day; especially when it extends beyond 12 hours.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.