Small Aircraft
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 20; Flight Crew Total 30000; Flight Crew Type 350
Situational Awareness
Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance
Human Factors; Aircraft
I was cleared the RNAV 16 approach to PWK.  I had been proceeding direct to HIGUH and after passing HIGUH I descended to the MDA.  I was supposed to descend to the MDA after passing PAMME; the next fix after HIGUH.  The Control Tower called a Low Altitude Alert and I responded by climbing back up into the clouds to an altitude appropriate to the position I was located.  I realized my error of descending too soon at about the same time as I received the alert from the Tower.  This was totally an error on my part.  I needed to pay more attention to the names of the fixes I was crossing; and the altitude I was supposed to be at crossing each fix.  My GPS is a Garmin 430; non-WAAS; so I was executing this approach as a non-precision descent to an MDA.  I am scheduled to have an improved GPS installed; which will have WAAS and therefore glide path capability; and an error such as I made will be less likely.In the meantime I will not make this error again.  My life depends on it.
GA pilot reported an altitude deviation and CFTT while on the RNAV 16 Approach to PWK airport. The Tower Controller advised the pilot of a Low Altitude warning prompting the pilot to climb back to assigned altitude.