M209P PLT DSNDED TO THE MDA OUTSIDE THE LOM ON THE NDB RWY 3 APCH AT SAT.

Narrative

ABOUT THE TIME THAT WE DEPARTED SSF FIELD ON THE SECOND MISSED; SAT; ATC ANNOUNCED THAT THE ILS TO RWY 3 WAS INOP AND THE APCH IN USE WOULD BE THE NDB TO RWY 3. I RECEIVED VECTORS TO THE APCH COURSE; CLRED FOR THE APCH; AND BEGAN A DSCNT FROM 2500 FT. HERE IS WHERE I SCREWED UP ROYAL: CONTINUED A DSCNT RIGHT ON DOWN TO 1380 FT; WHICH IS AUTHORIZED ONLY AFTER PASSING THE SA (BLUIE) NDB. WAS NOTIFIED BY ATC OF THE MINIMUM ALT UP TO THE NDB (2200 FT). CLBED; UP TO THIS ALT AND CONTINUED THE APCH; FINAL TO A LOW PASS RWY 3; AND A L TURN OUT TO T94. I THINK THIS EXCURSION FROM ALT OCCURRED DUE TO: LACK OF FAMILIARITY WITH THIS APCH; COUPLED WITH A DOSE OF SURPRISE THAT WE WOULD BE DOING IT FOR REAL AT THIS ARPT (SAT). MARGINAL VFR WX (WHICH ALONG WITH THE PRESENCE OF THE SAFETY PLT SEDUCED ME INTO FORGETTING THAT I WAS ON A 'LCL IFR' FLT PLAN). THOROUGH FAMILIARITY WITH THE TERRAIN ALONG THIS SEGMENT OF THE APCH; WHICH I HAVE FLOWN VFR MANY TIMES. IN THE LIGHT RAIN; SLIGHT HAZE; AND 2000 FT CEILING; AND ATTENDING MOSTLY TO THE INSTS; THE GND DID NOT SEEM OVERLY CLOSE. I WAS CLRED FOR THE APCH; AND ALL SEEMED WELL. THIS SPEAKS TO A PHENOMENON WITH WHICH I HAVE HAD SOME SIMILAR EXPERIENCE BEFORE; BUT CAN ONLY BE EXPRESSED THUSLY: WHEN YOUR FRIENDLY HOME FIELD EXPERIENCES A MAJOR OUTAGE OF NAV FACILITIES; YOU ARE DEALING WITH A WHOLE NEW AND NOW UNFAMILIAR ARPT. WOW.