A321
Flight Crew Air Transport Pilot (ATP)
Distraction; Workload
Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Wake Vortex Encounter
Flight Crew Returned To Clearance
Environment - Non Weather Related; Human Factors
We were descending on the TYSSN3 arrival into Las Vegas. The KADDY Intersection has a crossing restriction of 12;000 FT and 250 KTS. The automation was used and we were meeting all altitude crossings accordingly. Prior to reaching KADDY we began picking up moderate wake turbulence from the preceding aircraft. The Captain (pilot flying) overrode the aircraft and shallowed the descent and it was now in a non-managed configuration. Also the aircraft was put into heading for maybe 5 seconds and he rearmed the NAV. The KADDY fix showed magenta and we were clearly going to make the restriction no problem.I was watching the descent and was waiting for it to level at the alt constraint of 12;000 FT before continuing down after KADDY. What happened is it went below 12;000 FT; I said to the Captain to watch his altitude; KADDY has a 12;000 FT restriction. At this time we were at 11;600 FT and ATC gave us direct to PRINO essentially deleting the KADDY crossing. ATC never said anything about going below 12;000 FT but we clearly descended early. We talked about what happened and realized the aircraft was not put back into managed descent so it didn't honor the constraint. We needed to make sure we continue to use our CAMI procedures especially in those high workload environments.
[Report narrative contained no additional information.]
A321 flight crew reported overshooting a crossing restriction on the TYSSN3 arrival to LAS; with a wake vortex encounter cited as contributing to the workload.