Narrative:

I was PNF while approaching tus. I advised the first officer (PF) that he needed to stay high to avoid GPWS warnings due to high terrain west through northwest of the airport. After having briefed him he continued to descend even below the GS for the ILS runway 11L. We were not on the localizer course but were approaching the localizer south of the course. The airport was clearly in sight. As we cross a ridge, approach controller advised that they were switching runways to runway 29R. While I was talking to approach and acknowledging the clearance the first officer continued to descend and shortly after accepting the new runway assignment the GPWS warning annunciated. We executed the pull up maneuver and entered a left downwind for runway 29R. The first officer did not execute an immediate go around and I initiated the initial go around, then returned the aircraft to him. The automatic thrust was not responding to commands and I had to tell him to use manual thrust until I could reengage the automatic thrust. The first officer was a reserve who has not been flying much. His normal procedures performance was excellent but the non normal operations were weak. For my part I should have been more insistent on him maintaining better altitude awareness. As PIC I try not to intervene while the first officer is flying but review the procedural errors after the flight. This is one situation in which I should have intervened and been much more assertive about his altitude control.

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Original NASA ASRS Text

Title: AN A320 CREW RESPONDED TO A GPWS WARNING DSNDING INTO TUC.

Narrative: I WAS PNF WHILE APCHING TUS. I ADVISED THE FO (PF) THAT HE NEEDED TO STAY HIGH TO AVOID GPWS WARNINGS DUE TO HIGH TERRAIN W THROUGH NW OF THE ARPT. AFTER HAVING BRIEFED HIM HE CONTINUED TO DSND EVEN BELOW THE GS FOR THE ILS RWY 11L. WE WERE NOT ON THE LOC COURSE BUT WERE APCHING THE LOC S OF THE COURSE. THE ARPT WAS CLRLY IN SIGHT. AS WE CROSS A RIDGE, APCH CTLR ADVISED THAT THEY WERE SWITCHING RWYS TO RWY 29R. WHILE I WAS TALKING TO APCH AND ACKNOWLEDGING THE CLRNC THE FO CONTINUED TO DSND AND SHORTLY AFTER ACCEPTING THE NEW RWY ASSIGNMENT THE GPWS WARNING ANNUNCIATED. WE EXECUTED THE PULL UP MANEUVER AND ENTERED A L DOWNWIND FOR RWY 29R. THE FO DID NOT EXECUTE AN IMMEDIATE GAR AND I INITIATED THE INITIAL GAR, THEN RETURNED THE ACFT TO HIM. THE AUTO THRUST WAS NOT RESPONDING TO COMMANDS AND I HAD TO TELL HIM TO USE MANUAL THRUST UNTIL I COULD REENGAGE THE AUTO THRUST. THE FO WAS A RESERVE WHO HAS NOT BEEN FLYING MUCH. HIS NORMAL PROCS PERFORMANCE WAS EXCELLENT BUT THE NON NORMAL OPS WERE WEAK. FOR MY PART I SHOULD HAVE BEEN MORE INSISTENT ON HIM MAINTAINING BETTER ALT AWARENESS. AS PIC I TRY NOT TO INTERVENE WHILE THE FO IS FLYING BUT REVIEW THE PROCEDURAL ERRORS AFTER THE FLT. THIS IS ONE SIT IN WHICH I SHOULD HAVE INTERVENED AND BEEN MUCH MORE ASSERTIVE ABOUT HIS ALT CTL.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.