PA28 INSTRUCTIONAL FLT IN IMC WITH UNRELIABLE NAV INSTS CAUSES LOW ALT ALERT AT FRG.

Narrative

AFTER SEVERAL MISSED APCHS INTO FRG ILS RWY 14 AND WITH UNRELIABLE VOR/LOC/GS EQUIP; I REQUESTED EXTENDED CTRLINE APCH TO GET LINED UP WITH MORE THAN THE 2-3 MI DISTANCE ATC WAS GIVING TO IAF. AFTER ATC INFORMED ME THAT THEY WERE UNWILLING UNLESS I DECLARED AN EMER. I CHOSE UPON GETTING TO WHAT MY UNRELIABLE INSTS TO BE AS ESTABLISHED TO IMMEDIATELY PERFORM A LOC APCH AND DROP TO MDA (520 FT) (ALTHOUGH I WENT TO 600 FT) AND GET UNDER THE LAYER FOR A VISUAL APCH. UPON MY DSCNT AND VISUAL ACQUIREMENT OF THE RWY; ATC (NEW YORK TRACON) ADVISED ME OF A GND PROX ALERT AND INFORMED ME OF REQUIRED ALT OF 1400 FT AGL FOR THAT PORTION OF APCH. I INFORMED ATC OF VISUAL OF FRG RWY 14. ATC CANCELED IFR AND XFERRED ME TO TWR. UPON INITIAL CONTACT WITH TWR; THEY ALSO INFORMED ME OF GND PROX ALERT. I AGAIN STATED I HAD VISUAL OF ARPT AND RWY 14. I WAS CLRED FOR LNDG. I HAD EXPERIENCED INOP OR UNRELIABLE INSTS ON ALL APCHS THAT DAY (12 TOTAL; 10 MISSED DUE TO UNRELIABLE INSTS). I SHOULD HAVE WAITED UNTIL VFR CONDITIONS PREVAILED BEFORE MAKING THE IFR APCH ATTEMPT. EQUALLY MY DECISION TO FLY IN THE FIRST PLACE SHOULD HAVE BEEN QUESTIONED MORE. AN INST STUDENT IN POOR IMC FOLLOWED BY OUR ORIGINAL POINT OF DEP DROPPING TO 1/4 MI AND 100 FT; SHOULD HAVE LET ME KNOW THAT THESE WERE CONDITIONS NOT SUITABLE FOR TRAINING AT A BEGINNER LEVEL. MY FRUSTRATION OF 10 MISSED APCHS DUE TO UNRELIABLE EQUIP AND THE DESIRE TO COMPLETE THE FLT LED ME TO CHOOSE THIS UNSAFE METHOD TO LAND IN AN EXPEDITIOUS MANNER. I HAVE LEARNED TO TRUST MY FIRST INSTINCTS; CAREFULLY MONITOR THE WX; AND MOST OF ALL NOT TO INTRODUCE ANY STUDENT INTO POOR IMC THAT WILL OR POSSIBLY DROP SIGNIFICANTLY TO EITHER NEAR OR BELOW MINIMUMS.