NMAC.

Narrative

ON SHORT FINAL IN B727 AT 900 FT AGL WHILE ON ILS TO STT; OUR TCASII ISSUED A TA ALERT AND ALMOST IMMEDIATELY THE CAPT SAW A C-172 IN FRONT OF US AND SLIGHTLY LOWER. I LEVELED OUR ACFT AND PASSED APPROX 100 FT ABOVE THE C- 172. TWR RADAR WAS OTS. TWR DID NOT HAVE A VISUAL ON US OR THE C-172. AFTER OUR EVASIVE ACTION THE TCASII ISSUED A RA; BUT WE ALREADY HAD THE CESSNA IN SIGHT. THE TWR HAD CLRED US TO LAND PRIOR TO THE FINAL APCH FIX. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE TWR HAD A RADAR; BUT IT WAS INOP AT THAT TIME. THE TWR NEVER DID ANSWER THE RPTR'S QUESTIONS RELATIVE TO THE C-172; AS TO HOW HE GOT THERE AND WHETHER THE TWR HAD EVER TALKED WITH HIM PRIOR TO THE EVENT. THE C-172 DEPARTED FROM SJU/PR AND WAS ATTEMPTING TO LAND AT STT; BEING ON A XCOUNTRY FLT. THE RPTR LANDED AND PULLED OFF TO THE SIDE OF THE RWY TO OBSERVE THE C-172'S APCH AND LNDG. THE C-172 PLT WAS OBSERVED TO ATTEMPT A LNDG AT STT; USING THE WHOLE RWY; BEING OUT OF CTL MUCH OF THE TIME. HE FINALLY WENT AROUND AND LEFT THE AREA; PRESUMABLY FOR SJU. THE PLT OF THE 172 NEVER WAS HEARD TO SAY ANYTHING ON THE RADIO; EVEN AFTER THE TWR TRIED TO CALL HIM. RPTR ASSUMES THAT HE 'WAS ALL SHOOK UP.' RPTR WAS FAMILIAR WITH GA ACTIVITY FROM SJU TO STT. HE SAID THAT THE GA ACFT USUALLY GO DOWN THE COAST UNTIL ALIGNING WITH THE ILS RWY 10 AT STT AND THEN CUT STRAIGHT ACROSS TO THE ARPT. IF THEY ARE LOW; THEY ARE HARD TO SEE. SUPPLEMENTAL INFO FROM ACN 309181: PLT OF CESSNA TFC DISPLAYED VERY LIMITED ENGLISH LANGUAGE COM SKILLS.