MD80 CAPT WONDERS WHETHER HIS AFTER MARKET GFMS CAN BE USED TO IDENT FIXES ON APCHS.

Narrative

IN REVIEWING LOC RWY 27 APCH TO SAN; FOUND THE DME TO RWY 27 NOTAMED OTS. IN DISCUSSION ABOUT IDENTING THE VARIOUS INTXNS WITHOUT THE USE OF THE DME; TRIED TO FIND IN THE BOOK WHERE WE COULD USE THE GFMS TO IDENT THE FIXES INSTEAD OF RAW DATA. COULD NOT FIND THAT ANYWHERE. USED THE RADIALS OF POGGI VOR TO IDENT SWATT AND REEBO INTXNS AND USED TIME FOR MISSED APCH POINT. USING POGGI 304 DEG RADIAL; I STARTED DOWN OUT OF 2000 FT MSL. GFMS INDICATED THAT WE WERE ALMOST .5 MI FROM REEBO INTXN. TWR CALLED AND SAID 'ALT ALERT; CHK YOUR ALT. NEED TO CROSS REEBO AT 2000 FT MSL.' AT THAT POINT; I WAS AT 1650 FT MSL. I LEVELED FOR JUST A FEW SECONDS UNTIL THE GFMS INDICATED THAT WE WERE PAST REEBO AND CONTINUED APCH. A COUPLE OF QUESTIONS ARISE HERE. FIRST; IF IT IS LEGAL TO USE GFMS TO IDENT INTXNS; WHY ISN'T IT IN THE BOOK INSTEAD OF SOME OBSCURE ADVISORY CIRCULAR? BOOK IS VERY VAGUE ON USING GFMS FOR NAV ON LOC; ILS; LOC BACK COURSE; LDA AND SDF. IT SUGGESTS IT CANNOT BE USED FOR NAV PERIOD. SAYS NOTHING ABOUT USING IT TO IDENT INTXNS. THIS NEEDS TO BE CLRED UP. I JUST GOT OUT OF TRAINING AND THIS WAS BROUGHT UP BUT ABOUT HOW THIS NEEDS TO BE CHANGED. DON'T THINK ATC HAD A PROB; WANTED TO SEND THIS IN CASE.