EMB ERJ 170/175 ER/LR
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Distraction
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew Overcame Equipment Problem; Flight Crew Returned To Clearance
Aircraft; Human Factors
We were flying the ILS the approach in Runway XX in ZZZ. We were given to crossing restriction ZZZZZ at 3;000. We push the TSO button to descend to 3;000 feet we were getting closer than what we could make the autopilot do. After recrossed ZZZZZ at 3;000; the airplane was supposed to level off at 2;000 for ZZZZZ1. The airplane went into ALT capture at 2;000 feet but the aircraft itself descended down to 1;500 feet before we were able to turn off the autopilot and climb back up to 2;000 feet. In that time frame we got a message from ATC about altitude alert. By the time we were correcting our altitude back to 2;000 feet.In that time frame we had an issue with one of the passengers possibly unconscious in the back that we were also dealing with.Multiple things going on at the same time that made us a little slow to response to the altitude. We did not catch the airplane fast enough. We got below our given altitude on the arrival five 500 feet. Also; we were in VMC conditions with the airport insight.Cause - Relying on the autopilot to level off at the appropriate next altitude.Suggestions - Make sure aircraft does what we intend it to do and correct the aircraft faster.
[Report narrative contained no additional information].
EMB-175 flight crew reported the autopilot did not capture the altitude selected of 2;000 feet during approach.  The crew did not notice the issue until they were at 1;500 feet and immediately corrected back to 2;000 feet.