PC-12
Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 67; Flight Crew Total 8500; Flight Crew Type 1500
Human-Machine Interface; Situational Awareness
Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued New Clearance; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Became Reoriented
Environment - Non Weather Related; Human Factors; Procedure; Airspace Structure; Chart Or Publication
I was told to cross ZZZZZ at or above 12;300 feet and I was cleared for the RNAV (GPS) Approach. As I was descending past ZZZZZ I set my altitude at 10;000 feet. I should have set 11;800 feet per the approach chart; which is the altitude between ZZZZZ and ZZZZZ1. After ZZZZZ1 it is 10;000 feet until ZZZZZ2. About 10 to 15 miles from ZZZZZ1; Approach asked me to report ZZZZZ1. This seemed like an odd request; so I looked at the chart to make sure where ZZZZZ1 was and realized the error in altitude. As I started to initiate a climb; the TAWS (Terrain Alert Warning) activated and I got the terrain warning. The rest of the approach was normal after that.I think that I had 11;800 [ft.] set before ZZZZZ because the altitude I was descending from and my rate of descent was going to have me cross ZZZZZ well above 12;300 [ft.]. Then after crossing ZZZZZ I set 10;000 [ft.] because I was mentally one step ahead of where I actually was. While I was being proactive and efficient; I did not double check and confirm where I was on the approach. While I wasn't fatigued or distracted; I think complacency played a role due to the nice weather and the length of the flight.
A Medevac pilot reported they set too low an altitude for the approach procedure and received a terrain warning alert.