Small Transport; Low Wing; 2 Turboprop Eng
Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 100; Flight Crew Total 5000; Flight Crew Type 2300
Workload; Training / Qualification; Situational Awareness; Human-Machine Interface; Distraction; Confusion
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 Returned To Clearance; Flight Crew Took Evasive Action
Human Factors; Weather
While flying an unfamiliar light twin aircraft with avionics that I was unfamiliar with; I flew an RNAV approach to about 200 FT above minimums.  While distracted with the avionics; I flew below the prescribed altitude for the segment I was on.  I was not past the final approach fix; but believed I was and the Tower asked me to check my altitude due to a low altitude warning they got on my aircraft.  I checked and saw that I started the descent too early and climbed back up and regained the glide path for this approach and completed the approach and landing without further incident.
A pilot unfamiliar with an aircraft's RNAV equipment became distracted during the approach and descended below the final approach fix altitude where ATC notified him of a low altitude warning.