Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 22000
Distraction; Situational Awareness
ATC Issue All Types; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Environment - Non Weather Related; Procedure
We were told to expect 28C; however; just before we turned final from downwind ATC told us that our landing runway was changed to 27L. We had noted that other aircraft were being given 27L LOC just prior to our instructions. Both myself and the FO changed our frequencies and I gave a very quick brief on the 27 LOC approach. As we turned final; ATC told us to slow to 180kts until TAFFS; call ORD Tower etc. I manually disconnected the AP; followed shortly by the autothrottles; called for gear down; and manually began slowing the speed and descent while the FO put the LOC (GS out) mins; 1080 ft; in the altitude. I was attempting to descend from 2200 to 1080 ft after the Final Approach Fix while looking outside for the PAPI. The sun was right down the runway and I couldn't pick up the lights because of the glare. I knew I was above the MDA but also realized that the aircraft was lower than it should be at that distance. At the same time ATC informed us that their low altitude alert had gone off and to check our altitude. I leveled the aircraft and continued until I finally could see the PAPI as we got closer. They showed all red for a matter of moments then changed to 3 red; one white. I continued the visual to an uneventful landing. ATC changed the runway on downwind. There was very little time to do a complete briefing. It was a visual backed up by the LOC approach. Although the weather was clear; the sun was at such an angle that it totally obscured the PAPI's and I descended lower than a normal 3 to 1. I suspect as I was attempting to descend to the MAP altitude. ATC should not change runways on such a short notice; however; that being said; with the limitations of the aircraft; I would suggest flying to the FAF mins; set a 700 fpm on the VS and continue to the MAP. Especially if the PAPI's are obscured or there are other visual limitations. Without a GS and cleared for visual approaches without a PAPI system to rely on; we pilots have to be cognizant of aircraft/distance/descent points. Mentally exercising basic 3 to 1 approaches at all times.
Air carrier Captain reported receiving a low altitude alert from ORD Tower while descending on a visual approach with LOC backup to Runway 27L. PAPI lights were obscured by the sun.