PLT MISSES APCH WHEN TWR GIVES A LOW ALT ALERT WARNING. ON SUBSEQUENT APCH IN VISUAL CONDITIONS ON PROFILE FOR LNDG; TWR GAVE THE SAME WARNING.

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OPERATING AS AN ACFT X FLT INTO CLARKSBURG; WV; WE HAD TO FLY THE VOR 3 APCH; DUE TO LOW CEILINGS AND RAIN SHOWERS. WE WERE VECTORED ON TO FINAL AND CLEARED FOR THE APCH. I WAS CALLING OUT THE STEP-DOWN ALTS; WHILE THE FO WAS FLYING. WE WERE INSTRUCTED TO MAINTAIN 3300 FT UNTIL ESTABLISHED AND THEN WE WERE CLRED FOR APCH. WE DIDN'T INTERCEPT UNTIL WE WERE CLOSE TO THE VOR; AT THAT TIME WE CROSSED AND BEGAN OUR DSCNT TO THE MDA OF 1800 FT. AS WE CROSSED THE VOR AND WERE DESCENDING THE TWR SAID 'I'M SHOWING A LOW-ALT ALERT; I SUGGEST YOU CHECK YOUR ALT.' FOLLOWED; AGAIN BY THE SAME MESSAGE. I ELECTED TO GO MISSED APCH AND TRY IT AGAIN. THE NEXT APCH; SAME WARNING. THE FINAL APCH COURSE TRAVERSES THROUGH SOME HIGH MOUNTAINOUS TERRAIN. ON THE GND I CALLED AND SPOKE WITH CKB APCH. HE EXPLAINED THAT THEIR COMPUTER HAS PARAMETERS THAT SENSE RATE OF DSCNT AND TERRAIN AREAS; AND IF THEY GET A 'WARNING' THEY NEED TO PASS IT ALONG TO THE PLTS. WE TALKED IT OVER AND IT BECAME CLR THAT THE EQUIPMENT MAY BE A LITTLE PREMATURE IN ITS WARNINGS. WE DID THE SAFEST THING AND WENT 'MISSED APCH.' CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: PLT RPTS THAT HIS RATE OF DSCNT ON THE FIRST APCH WAS A CONCERN AND WITH THE TWR WARNING HE WENT AROUND. THE SECOND APCH WAS NORMAL AND HE WAS AT LEVEL AT THE MDA WITH THE RWY IN SIGHT WHEN THE TWR GAVE THE LOW ALT ALERT. HE ELECTED TO LAND. RPTR SAID THAT IN HIS DISCUSSION WITH THE TWR ABOUT THE INCIDENT; THE OPERATOR INDICATED THAT THIS HAPPENS ALL THE TIME.