A LEAR 35 FLT CREW; WHILE ON A VISUAL APCH AND TO MAINTAIN 2600 FT 'TIL PAST MCF AFB;' EXPERIENCES AN ALTDEV ALT EXCURSION 7 NM S OF TPA; FL.

Narrative

WHILE ON THE BRIDGE 5 APCH INTO TAMPA ARPT; WE WERE ASSIGNED AN ALT OF 2600 FT TO BE MAINTAINED UNTIL AFTER CLRING A NEIGHBORING ARPT. SINCE THE WX WAS CLR; WE WERE ASSIGNED A VISUAL APCH INTO TAMPA. WE HAD LOADED IN A GPS APCH FOR BACKUP. WHILE I WAS LOOKING FOR THE APPROPRIATE RWY; MY FELLOW PLT REALIZED THE AUTOPLT HAD STARTED THE DSCNT INTO TAMPA ON THE GPS APCH. HE IMMEDIATELY ANNOUNCED THE CONDITION AND STARTED A CLB BACK TO THE ASSIGNED ALT OF 2600 FT. MAX ALT LOSS WAS 200 FT OR LESS. HE THEN GAVE THE CTLS BACK TO ME; SINCE I WAS THE PF. I LOST ALT AWARENESS WHILE LOOKING FOR THE UNFAMILIAR ASSIGNED RWY. AFTER THIS OCCURRENCE; I WILL BE MORE AWARE WHEN IN AUTOPLT MODE. SUPPLEMENTAL INFO FROM ACN 580950: I WAS SITTING IN THE R SEAT ACTING AS THE PNF. THE SIC WAS SITTING L SEAT; AND WAS ACTING AS THE PF. ABOUT 20 MI SE OF TPA; THE SIC CALLED THE FIELD IN SIGHT AT THE 1 O'CLOCK POS. I COMMENTED THAT THIS WAS NOT TPA; BUT A MIL AIRFIELD S OF TPA; AND THAT THIS AIRFIELD WAS BENEATH THE APCH COURSE FOR THE ANTICIPATED RWY; RWY 36R. ADDITIONALLY; I MENTIONED THAT WHILE ON A VISUAL APCH TO RWY 36R; IT WOULD BE NECESSARY TO STAY ABOVE THE AIRSPACE FOR THIS ARPT UNTIL N. I LOADED THE GPS RWY 36R APCH INTO THE FMS AND INFORMED THE SIC THAT IT WAS AVAILABLE TO ASSIST IN RWY VERIFICATION AS WELL AS TO PROVIDE HORIZ AND VERT GUIDANCE. DUE TO THE EXCELLENT WX CONDITIONS; A VISUAL APCH WAS ANTICIPATED; AND THE APCH WAS NOT FORMALLY BRIEFED. APCH SUBSEQUENTLY PLACED THE ACFT ON A VECTOR TO VISUALLY INTERCEPT THE FINAL APCH COURSE FOR RWY 36R AND NOTIFIED US THAT AN MD80 WOULD BE PARALLEL FOR RWY 36L. ONCE THE SIC IDENTED RWY 36R; ATC WAS NOTIFIED; AND THE ACFT WAS CLRED FOR THE VISUAL APCH TO RWY 36R WITH THE RESTR TO MAINTAIN 2600 FT UNTIL N OF MACDILL AFB. THE CLRNC WAS ACKNOWLEDGED TO ATC; AND THEN BTWN MYSELF AND THE SIC. THE ACFT WAS LEVEL AT 2600 FT FLYING ON THE AUTOPLT. I ACTIVATED THE GPS APCH AND INFORMED THE SIC. I KEPT MY ATTN PRIMARILY OUTSIDE THE ACFT; VERIFYING CTRLINE ALIGNMENT WHILE ATTEMPTING TO VISUALLY LOCATE THE PARALLEL MD80 TFC ON RWY 36L. IT WAS AT THIS POINT THAT I XCHKED THE ALTIMETER AND NOTICED A DSCNT THROUGH 2400 FT. I VERIFIED THAT THE ACFT WAS NOT YET N OF THE MACDILL AFB AND GAVE A VERBAL WARNING TO THE SIC; AND BRIEFLY ASSUMED COMMAND OF THE ACFT BY ADVANCING THE THROTTLES AND ARRESTING THE DSCNT. RECOVERY TO 2600 FT OCCURRED AS THE ACFT CROSSED OVER THE MAIN RWY AT MACDILL AFB. I WAS CAUGHT OFF-GUARD BY THE EARLY DSCNT. AT THE TIME; ATTN WAS FOCUSED OUTSIDE THE AIRPLANE; AND THERE WAS NEITHER A VERBAL INDICATION FROM THE SIC OR AN AUTOPLT DISCONNECT TONE TO BRING IMMEDIATE ATTN TO THE CHANGE OF ACFT ALT. AT NO POINT DID THE SIC INDICATE CONFUSION OVER THE CLRNC. I BELIEVE THAT THE ERROR OCCURRED AS A RESULT OF A LOSS OF SITUATIONAL AWARENESS ON THE PART OF THE SIC AND A MOMENTARY DISTR ON MY PART. THE SIT WAS COMPOUNDED BY AN UNUSUAL CLRNC FOR A VISUAL APCH; THAT ALSO INCLUDED AN ALT RESTR. COMPANY PROCS CLRLY DEFINE PF AND PNF COM DURING INST APCHS; BUT OFFER LITTLE FORMAL GUIDANCE FOR A VISUAL APCH. IN THIS CASE; A SIMPLE VERBAL INDICATION ON THE PART OF THE PF THAT THEY WERE BEGINNING THE DSCNT FOR LNDG WOULD HAVE ALLOWED THE PNF TO DETECT THE ERROR EARLIER.