Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 139
Confusion; Distraction; Situational Awareness
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Overrode Automation
Human Factors; Chart Or Publication; Procedure
Aircraft on vectors into ZZZ; NAV2 was not set correctly leading to an unexpected autopilot disconnect on intercept and loss of approximately 600 feet altitude. We arrested the descent and fixed the issue. ATC issued a low alt alert but at that point we were regaining lost alt and had the runway in sight. We advised ATC as such and continued visually for a normal landing. I incorrectly set the First Officer's RTU (Radio Tuning Unit) and did not catch it on the approach check.
CRJ-200 Captain reported they entered the wrong ILS frequency in the pilot flying's autopilot causing it to disconnect resulting in an altitude loss and a Low Altitude Alert from ATC. The crew corrected the altitude and had the airport in sight and continued to a normal landing.