Skylane 182/RG Turbo Skylane/RG
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor
Flight Crew Last 90 Days 80; Flight Crew Total 15000; Flight Crew Type 100
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Provided Assistance; Flight Crew Became Reoriented
Aircraft; Weather; Procedure; Human Factors
During the approach to HDC; New Orleans was vectoring me for the ILS to Runway 18. They gave me a heading to join the LOC and cleared me for the ILS to Runway 18. Moments later they ask if I was receiving the LOC; and advised me that a previous aircraft had let them know that they had not received it. I replied that I was not receiving the LOC; and they ask if I would like the RNAV to Runway 18. I replied yes; and they immediately cleared me for the RNAV to Runway 18. I had expected that ATC was going to vector me back around in a box pattern to set up for the RNAV to Runway 18; and when they simply cleared me for that approach; I started scrambling; since I was single pilot to reset the radios for the approach and join the inbound course. I was able to join the inbound course; a couple of miles outside the FAF; however upon being handed over to HDC Tower; Tower immediately advised me of a low altitude alert from New Orleans Approach. I had descended below the minimum altitude on the approach; prior to the FAF. I broke out of the clouds into VMC at approximately 1200 ft.; 600 ft. below the minimum altitude. I believe that the cause for this event is my failure to NOT accept the clearance for an approach that I was not completely set up and ready for. I should have asked for vectors in a box pattern to join the approach; and give myself time to fully brief the approach; have the radios set up; and be completely prepared prior to joining the final approach course. My hurried effort to set up the radios for the approach and join the course distracted me from flying the airplane and cause me to bust the altitude.
Cessna 182 Pilot reported being alerted by Air Traffic Control that LOC Approach was not working and therefore being cleared for an RNAV approach completely unprepared which caused a descent below minimum altitude.