ENG FAILURE-INFLT.

Narrative

DEPARTED CTLED ARPT AS CAPT IN PAX CARRYING COMMUTER OP AT XA07 LCL TIME; FO WAS FLYING. AT APPROX 7NM SE OR THE ARPT AND ABOUT 4000 FT MSL THE R ENG ABRUPTLY SEIZED AND THE PROP FEATHERED BY THE AUTOFEATHER SYS. WE NOTIFIED THE TWR AND COMPANY THAT WE WERE RETURNING TO THE ARPT. TWR ASKED THE REASON FOR OUR RETURN. AFTER INFORMING HIM OF OUR R ENG FAILURE HE ASKED FOR OUR DISTANCE OUT; NUMBER OF SOULS; FUEL ON BOARD THEN CLRED US TO LAND. WE PERFORMED THE ENG SECURE CHKLIST AND I NOTIFIED THE PAX THAT WE HAD A PROB WITH THE R ENG; THAT WE WERE RETURNING TO THE ARPT. I INSTRUCTED THEM TO FASTEN SEAT BELTS AND TO SECURE SEATBACKS AND TRAY TABLES FOR LNDG. WE LANDED WITHOUT INCIDENT AND TAXIED OFF THE RWY TO THE RAMP UNDER OUR OWN PWR. NO EMER WAS DECLARED NOR WAS PRIORITY ASKED FOR. THE FO FLEW THE ACFT THROUGHOUT. AN INTERESTING SIDE NOTE RELATES TO OUR TRAINING PROC OF VERIFYING THE FAILED ENG BY NOTING N1; AND FUEL FLOW. IN OUR CASE THE ENG SEIZURE WAS RELATED TO THE PROP GEARBOX. BECAUSE OF THE FREE TURBINE DESIGN OF THE PT6; THE COMPRESSOR SECTION CONTINUED TO FUNCTION AND GIVE NORMAL N1; AND FUEL FLOW INDICATIONS WHILE THE PWR/PROP SECTION HAD FROZEN. IN THIS CASE THE PROP RPM AND TORQUE INDICATIONS WERE ZERO WHICH WOULD NOT NECESSARILY HAVE BEEN THE CASE IN A 'NORMAL' ENG FAILURE. ANOTHER OBSERVATION WAS HOW UNUSUAL IT FELT TO BE THE NON-FLYING PLT DURING AN ENG FAILURE; SINCE IN TRAINING THESE THINGS ARE PRACTICED FROM THE STANDPOINT OF THE PF.