A321
Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Training / Qualification; Distraction
Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Human Factors
We were descending on the KEPEC3 RNAV Arrival into LAS. We were cleared to cross CLARR at 13;000 feet and 250 kts. I used open descent to get down to altitude so that I would be at 250 kts early. As we approached CLARR we were told to descend via the arrival except maintain 210 kts at IPUMY. I was the pilot flying so I put in 8;000 feet in the altitude window and pushed the altitude button for a managed descent. At this point Las Vegas Approach told us to expect Runway 19R for landing. We had 25L set up and briefed. I was surprised by this and asked [First Officer] to set up the runway in the arrival. I looked in my approach plates for an approach to 19R and realized that we would need to request the RNAV visual. At this point I looked up to monitor the aircraft and noticed that we were in a descent through 11;000 feet. I felt that this was wrong and went back to the arrival chart to double check. I saw that we were below the arrival altitude and went to vertical speed 0; put 13;000 feet back in and did an open climb back to 13;000 feet. We crossed KEPEC at 13;000 feet and continued with the descent. I believe we were between 11;000 and 10;500 feet when I made the correction. We never got a call from approach control.I realize how dangerous this was and I failed to verify on my PFD that I was level at 13;000 feet and in managed descent. I took [the First Officer] out of the monitoring position by having him put in the new runway. I got distracted by looking up the approaches and took too much time away from monitoring by set up the [charts] to have the approach page ready. It was a clear night and I had terrain selected in my Navigation Display (ND); but this was a huge mistake. Should always have one pilot monitoring. Should have transferred control to [First Officer] and set up the runway and approach myself.
Being new to the Airbus; the Captain was unsure about 'managed' approaches. Our divided attentions at the time; due to FMS inputs; took attention from our crossing restrictions.
A320 flight crew reported overshooting a crossing restriction on an RNAV arrival into LAS when they were distracted with a late runway change.