C182 PLT DSNDS BELOW LOC MDA WHILE FLYING AN ILS APCH WITH THE GLIDE PATH OTS AT ORL.

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UNFORECAST WX MOVED INTO THE ORLANDO; FL; AREA WHILE I WAS FLYING VFR. RPTED WX IN ORLANDO WAS 400 FT OVCST AND 1 MI VISIBILITY. UPON CONTACT WITH ORLANDO APCH; I REQUESTED AN IFR CLRNC TO THE ORLANDO EXECUTIVE ARPT. I WAS CLRED DIRECT AND TOLD TO EXPECT THE LOC BACK COURSE RWY 25 APCH. WX DETERIORATED TO 200 FT OVCST. A LAST MIN RWY CHANGE WAS MADE AND I WAS TOLD TO EXPECT RWY 7. I SET UP FOR THE ILS RWY 7 ORL AND WAS GIVEN VECTORS TO THE FINAL APCH COURSE. I WAS CLRED FOR THE ILS RWY 7 AND PROCEEDED INBOUND AS PLANNED. I BEGAN MY DSCNT AT GS INTERCEPT AND TRACKED THE LOC AND GS INBOUND. THE RWY ENVIRONMENT WAS IN SIGHT 50 FT ABOVE DECISION ALT. HOWEVER; UPON ACQUIRING THE VASI; I DISCOVERED I WAS WELL BELOW GLIDE PATH AND MADE A CORRECTION TO INTERCEPT. UPON LNDG; I DISCOVERED THE GS WAS RPTED OTS. WITH THE GS INOP; THE MDA FOR THE LOC APCH SHOULD HAVE BEEN 660 FT. THE CHAIN OF EVENTS LEADING TO THE FLT BEGAN WITH THE UNFORECAST IFR CONDITIONS IN THE ORLANDO AREA. I FAILED TO THOROUGHLY LISTEN TO ATIS AND OVERLOOKED AN IMPORTANT PIECE OF FLT INFO. THE CHANGE FROM THE LOC BACK COURSE RWY 25 TO THE ILS RWY 7 MADE ME COMPLACENT IN THINKING THE CHOICE FOR AN APCH TO LOWER MINIMUMS WAS THE REASON THE RWY CHANGE WAS MADE. I COULD NOT THINK OF ANY OTHER REASON FOR SWITCHING TO RWY 7 OPS SINCE ALL OTHER APCH MINIMA WERE ABOVE THE LOC BACK COURSE RWY 25 MINIMUMS. THE WIND WAS SOUTHERLY AT ABOUT 8 KTS. MY MIND WAS SET ON SHOOTING THE ILS APCH. IN ADDITION; THE ORLANDO APCH CTLR DID CLR ME FOR THE ILS RWY 7 APCH; NOT THE LOC RWY 7 APCH. MY RPT TO EXECUTIVE TWR WAS FOR THE ILS RWY 7; AND NO COMMENT OR CORRECTION WAS MADE. UNFORTUNATELY; I DISCOVERED THE ERROR AFTER I LANDED. CORRECTIVE ACTIONS INCLUDE THOROUGHLY LISTENING TO ALL ATIS AND NOTAMS REGARDLESS OF ARPT FAMILIARITY. THE LOC WAS TUNED AND IDENTED; HOWEVER THE GS CONTAINS NO SEPARATE IDENT. THE GS WAS SEEMINGLY FUNCTIONING PROPERLY PRIOR TO GS INTERCEPT; HOWEVER; I DID NOT NOTICE IF I RECEIVED A NAV FLAG AFTER PASSING THE OM. LACK OF CTLR SPECIFICITY REGARDING THE APCH I WAS TO FLY WAS ALSO A FACTOR.