FLC OF ACR MDT DECLARED AN EMER AND RETURNED TO LAND AFTER FAILURE OF 1 ENG.

Narrative

COMING INTO HSV ON PRIOR LEG; THE R ENG N1 GAUGE BEGAN TO FLUCTUATE PLUS OR MINUS 20 PERCENT. ON THE GND; CALLED MAINT CTL AND MADE ENTRY INTO LOGBOOK. ALL OTHER ENG INDICATIONS WERE NORMAL. SINCE ALL OTHER PARAMETERS WERE NORMAL; WE AGREED TO DEFER THE GAUGE PER THE MEL. NEXT LEG -- START; TAXI; TKOF WERE ALL NORMAL AND ALL ENG PARAMETERS WERE NORMAL; INCLUDING THE R ENG N1. AT ABOUT 12000 FT; THERE WAS A LOUD BANG FOLLOWED BY A TOTAL FAILURE OF THE R ENG. WE SECURED THE ENG; DECLARED AN EMER; AND RETURNED TO HSV AND LANDED WITHOUT FURTHER INCIDENT. IT SEEMS THAT THE FLUCTUATING N1 WAS NOT A BAD GAUGE BUT A SIGN THAT THE ENG WAS GOING BAD EVEN THOUGH FUEL FLOW; TORQUE AND ITT WERE ALL NORMAL. THE MEL ALLOWED THE GAUGE TO BE DEFERRED WITHOUT A MECH TROUBLE- SHOOTING IT. THE N1 IS THE ONLY ENG GAUGE THAT CAN BE DEFERRED IN OUR MEL. HAD A MECH COME OUT AND SWAPPED GAUGES AND RUN THE ENG UP; AN INFLT ENG SHUTDOWN MIGHT HAVE BEEN AVOIDED. I SHOULD HAVE INSISTED ON A MECH COMING OUT ALSO. INCIDENTALLY; THE FO IS ALSO TYPED IN THE ACFT AND IS ALSO A MECH WITH IA AUTH; AND HE ALSO BELIEVED IT WAS A BAD N1 GAUGE GIVEN THE INFO WE HAD.