B737-300 FLC HAS ALT EXCURSION DURING APCH TO KBNA.

Narrative

DSNDED BELOW GSI ALT EARLY; MISIDENTED DEST AIRFIELD. WHILE ON FINAL APCH TO NASHVILLE; ON THE ILS TO RWY 31; WE DSNDED BELOW THE GS INTERCEPT ALT EARLY; MISIDENTING SMYRNA AIRFIELD FOR NASHVILLE. APCHING 1500 FT MSL; THE APCH CTLR RECOGNIZED OUR MISTAKE AND DIRECTED US TO CLB BACK TO 2300 FT INFORMING US THAT WE WERE ATTEMPTING TO LAND AT THE WRONG AIRFIELD AND THAT NASHVILLE WAS STILL 10 NM AWAY. THE INCIDENT OCCURRED FOR MULTIPLE REASONS; BUT WAS PREVENTABLE THROUGH PROPER MONITORING OF THE ACFT NAV INSTS. DUE TO TFC; WE WERE VECTORED TO AN ABNORMALLY LONG FINAL; APPROX 30 NM. WE WERE ALSO DIRECTED TO SLOW TO 170 KTS EARLY IN THE APCH. WHILE BEING VECTORED; WE WERE IN AND OUT OF THE BASES OF THE CLOUDS SO WE COULD NOT IMMEDIATELY VISUALLY PICK OUT THE AIRFIELD. THE WINDS AT ALT WERE STRONG (APPROX 40 KT HEADWIND). ALL OF THIS CREATED A VERY SLOW AIRSPD; WHICH MADE THE LONG FINAL APPEAR EVEN LONGER THAN NORMAL. AT APPROX 15 NM (DME); WE VISUALLY PICKED UP AN AIRFIELD. WE COULD SEE THE VASI; AND WE WERE HIGH. I TUNED THE ILS FOR BNA RWY 31 (NO DME) AND GOT A GS COMPARATOR LIGHT BTWN THE CAPT'S AND MY ILS GS. THIS MADE US BELIEVE THE GS MAY NOT BE CORRECT; AS IT WAS SHOWING FULL DEFLECTION LOW (A NORMAL DISPLAY FOR WHERE WE WERE). WE QUICKLY CONFIGURED AND STARTED A DSCNT TO THE WRONG AIRFIELD. APCH CTL RECOGNIZED OUR ERROR AND DIRECTED US TO CLB BACK TO 2300 FT. WE STARTED A CLB; AND I RE-TUNED THE BNA VOR; NOW RECOGNIZING THAT WE WERE STILL 10 NM AWAY FROM BNA. MULTIPLE FACTORS TO INCLUDE A LONG FINAL; SLOW GND SPD; MARGINAL VFR WX AND INST COMPARATOR LIGHT ALL HELPED ME CONVINCE MYSELF THAT THE AIRFIELD WE SAW WAS BNA. I DID NOT XCHK THE DME TO BNA WITH THE APCH PLATE TO SEE THAT WE WERE STILL OUTSIDE THE FAF. THERE IS NO REF TO SMYRNA ARPT ON THE 10-7 PAGE FOR NASHVILLE. I BELIEVE A NOTE ON THE ARR SECTION OF THE 10-7 CAUTIONING CREWS NOT TO MISTAKE SMYRNA FOR NASHVILLE WHEN FLYING AN APCH TO RWY 31 WOULD HELP PREVENT THIS TYPE OF MISTAKE IN THE FUTURE. OVERALL; THIS MISTAKE WAS PREVENTABLE. WHILE ON AN ILS APCH; CONTINUE TO MONITOR ALL REQUIRED NAVAIDS TO DETERMINE YOUR POS AND PROGRESS. DON'T LET VISUAL CUES CONFUSE YOUR TRUE POS.