CFTT. GS INDICATOR MALFUNCTION.

Narrative

WHILE BEING VECTORED FOR THE ILS TO RWY 30 AT HTS; I NOTICED THAT THE GS INDICATOR SHOWED THAT WE WERE ABOVE THE GS; WHICH CORRESPONDED WITH OUR VECTORING ALT OF 3000 FT MSL. APCH CLRED US FOR THE APCH AND WE DSNDED TO 2600 FT MSL AS INSTRUCTED AND IT STILL INDICATED THAT WE WERE ABOVE THE GS. ONCE ESTABLISHED WE COULD DSND TO 2100 FT MSL. ONCE WE BECAME ESTABLISHED ON THE LOC; WE WERE STILL SHOWING 1/2 DOT ABOVE THE GS. I ASSUMED THAT WE HAD RECEIVED A BAD VECTOR FROM ATC; AND BEGAN TO DSND TO CATCH THE GS; BUT WAS NOT AWARE OF THE ALT/RATE OF DSCNT. THE GND PROX WARNING STARTED GOING OFF AND I COULDN'T FIGURE OUT WHY; BECAUSE I WAS STILL INDICATING ABOVE THE GS. WE GET A LOT OF FALSE WARNINGS; SO I ASSUMED THIS WAS ANOTHER ONE; UNTIL I LOOKED AT THE RATE OF DSCNT; AND REALIZED THAT THE GS INDICATOR NEEDLE HAD STUCK IN POS SHOWING US 1/2 DOT HIGH AND I WAS BELOW THE GS. I IMMEDIATELY INITIATED A GAR AND CLBED. MEANWHILE ATC HAD NOTICED THE DEV FROM THE GS AND WAS RECEIVING A LOW ALT ALERT AND CALLED FOR US TO CLB IMMEDIATELY. WHAT THE FO WAS DOING; I DO NOT KNOW. I KNOW THAT HE WAS EXTREMELY TIRED FROM BEING ON DUTY 6 STRAIGHT DAYS (RESERVE FO). HE SAID THAT HE HAD RECEIVED THE SAME INDICATION ON HIS GS INDICATOR; BUT IT WORKED PERFECTLY ON THE NEXT ILS APCH. IF IT HAD NOT BEEN FOR THE GPWS AND ATC; WE WOULD HAVE HAD A CFIT INSTEAD OF A CFTT.