Regional Jet 900 (CRJ900)
Flight Crew Air Transport Pilot (ATP)
Confusion; Situational Awareness
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 Became Reoriented
Human Factors
Enroute to AZO; I had briefed the 35 ILS approach. When we were close to AZO; the wind speed and direction made 35 unusable. We asked for vectors to set up for the RNAV 17 approach. I briefed the approach and we took vectors to the approach. During the approach; AZO tower advised us of a low altitude alert. I had inadvertently started down to minimums just prior to WURAX. I started back up; but we were crossing WURAX so I continued down to my MDA of 1200 feet MSL and continued to a normal landing. While discussing the approach at the gate; I realized I had descended to the LNAV/VNAV minimums 1200 feet. I should have stopped at the LNAV minimums of 1400 feet.After reviewing the Approach Plate; I realized that this approach plate had minimums for 3 different approaches. LPV; LNAV/VNAV; and LNAV. I had looked at the second box where LNAV minimums are on many charts. In the future I will be aware of the fact that there could be a LPV approach listed. In the future I will pay closer attention to the advisory VNAV.
This situation highlighted how workload can divert attention. I will be much more vigilant when plans change from the expected in the future. Great learning experience.
CRJ-900 flight crew reported receiving a low altitude alert from ATC on approach to AZO when they descended below charted altitude.