Challenger 350
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Human Factors
On our way out to PIA we were cruising at 10;000 feet. I was the pilot monitoring. The weather was VMC. About a 100 miles from PIA we were cleared to go direct to our destination. The ATIS was advertising landing RW 31 and RW 22. We choose to land on RW 22 with the GPS approach. Once we got about 50 miles from the airport we asked ATC if we could go direct to WEKAR one of the fix on the approach. ATC agreed and cleared us for the GPS approach telling us to cross at or above 2;400 feet WEKAR waypoint. We decided to shoot the LNAV/VNAV. The Pilot Flying (PF) selected 2;400 in the FMS; selected approach mode and selected VNAV. I confirmed all the tasks. While descending I had my head down working on the performance in the FMS. All of a sudden ATC asked to check our altitude and asked us to get back to 2;400 feet. When I checked the altimeter we were at about 2120 feet. We got back immediately to 2;400 feet and the controller told us that he was showing again 2;400 feet on his radar and seemed satisfied. The rest of the approach and landing were uneventful.While debriefing the approach we realized that the PF set the MDA in the altitude alerter instead of the altitude at which to cross the FAF (2;400 feet). This caused the airplane to descent below 2;400 feet on its way to the MDA. I asked the PF to review the AOM (Aircraft Operations Manual) and the procedures for shooting an LNAV/VNAV or for shooting an LPV which he did and admitted the error. Although I confirmed the altitude set in the FMS I did not confirm the altitude set in the altitude alerter. I should have been more vigilant and make my FMS computations way in advance of the approach in order to properly monitor the approach.
CL-350 Captain reported receiving a low altitude alert from ATC on a day visual approach to PIA.