ACR LTT HAS GPWS ACTIVATE ON DSCNT TO FAF.

Narrative

FLT DEPARTED BNA OVER 3 HRS BEHIND SCHEDULE DUE TO MAINT/EQUIP DELAY. I WAS EVALUATING A FO DUE TO A PREVIOUS IRREGULARITY THAT THE PLT HAD BEEN INVOLVED. THERE WAS ALSO AN INSTRUCTOR/CHK AIRMAN ON THE JUMP SEAT FULFILLING AN ANNUAL OBSERVATION FLT REQUIREMENT. A FLT ATTENDANT AND 28 NOT VERY HAPPY PAX WERE ALSO ON BOARD. AT A CRUISE OF 15000 FT MSL WE WERE CLRED TO CROSS 30 NM W OF TYS VORTAC AT 11000 FT. A STRONG TAILWIND RESULTED IN A DSCNT GND SPD OF GREATER THAN 385 KTS. PROGRESSIVE ALTS WERE GIVEN -- 11; 7; 4; AND FINALLY 2500 FT UNTIL FAF. ATC ISSUED VECTORS FOR SPACING; DSCNT; AND INTERCEPTING THE LOC; THE REQUIRED RATE OF DSCNT WAS 1850-2000 FPM TO ATTAIN THE 2400 FT AT BUZBY OM (FAF). AS THE ACFT PASSED 2500 FT MSL; THE GPWS ISSUED 'TERRAIN' AND 'PULL UP' ALERTS. I IMMEDIATELY DISCONNECTED THE AUTOPLT AND INITIATED A LEVEL OFF AND THE CLB FROM 2300 FT TO 2400 FT MSL; CONTINUING THE ILS 23 R APCH AND LNDG WITHIN NORMAL PROFILE. I HAD DISTRACTED MY ATTN FROM MONITORING THE AUTOPLT INPUT/OUTPUT TO MAKE FINAL NAV TUNING AND SET-UP. THE FO HAD RESPONDED TO ATC CLRNC TO 2500 FT JUST PRIOR TO REACHING 4000 FT MSL. HE SET 5500 FT ON THE ALT ALERT (REASON UNKNOWN) SO THE AUTOPLT DID NOT INITIATE LEVEL OFF AS EXPECTED. DUE TO THE HIGH RATE OF DSCNT; THE GPWS GAVE WARNING IN TIME TO PREVENT IMPACT WITH OBSTACLE/TERRAIN. ON BEHALF OF MY CREW AND THE 28 UNKNOWING PAX; I WOULD LIKE TO THANK ALL OF THOSE RESPONSIBLE FOR GPWS ENGINEERING AND LEGAL REQUIREMENTS FOR PREVENTING THIS ACCIDENT.