FLT CREW OF DHC6 ENCOUNTER EXCESSIVE ENG TEMP INDICATIONS AND RETURN TO LAND AT GCN.

Narrative

WE DEPARTED THE RWY AT THE GCN. THE ACFT WAS ABLE TO REACH TKOF CALCULATED TORQUE WITHOUT EXCEEDING ANY TEMP LIMITATIONS OR ANY REDLINE LIMITATIONS. ON CLBOUT; THE R T5 (5TH STAGE TURBINE TEMP) GAUGE WAS AT THE TOP OF THE YELLOW ARC AT 725 DEGS C. AS WE CLBED OUT THE T5 LOWERED INTO THE GREEN ARC AS THE FO REDUCED PWR IN ORDER TO REDUCE THE PERCENTAGE ON THE PROPS. AFTER CALLING FOR THE AFTER TKOF CHKLIST THE FO AND I NOTICED THE GAS GENERATOR SPD HIGHER THAN NORMAL. AS WE REACHED CRUISE ALT THE GAS GENERATOR SPD WAS AT RED LINE. I ADVISED THE FO TO REDUCE PWR IN ORDER TO REDUCE PROP SPD; AS SOON AS POSSIBLE. I CHKED THE CAUTION LIGHTS FOR ANY DISCREPANCIES FOLLOWED BY CHKING THE OTHER ENG INSTS. EVERYTHING WAS IN THE SAFE ARC. I THEN CHKED THE ABNORMAL CHKLIST AND EMER CHKLIST. T5 NEVER WENT PAST THE RED LINE; IT WAS AT RED LINE. THE FO REDUCED THE PWR TO 35 LBS OF TORQUE. T5 STILL REMAINED IN THE RED. AT THAT TIME I MADE THE DECISION TO RETURN TO THE FIELD. I SAW NO NEED TO SHUT DOWN THE ENG BECAUSE THE OTHER ENG GAUGES WERE SHOWING IN THE GREEN; AND THE PWR PLANT SHOWED NO TREND OF EXCEEDING LIMITATIONS. I TOLD THE FO TO TURN AROUND AND RETURN TO THE SUITABLE ARPT. I ADVISED DISPATCH AND GOT AN AMENDMENT TO THE RELEASE. I ADVISED ATC OF THE RETURN AND OUR CONDITION. I ALSO ADVISED THE PAX THAT WE WERE RETURNING AND IT WAS JUST A PRECAUTIONARY LNDG. I THEN CALLED DISPATCH VIA SATELLITE PHONE AND GAVE THEM AN UPDATE. THE PAX REMAINED CALM THROUGHOUT THE FLT. I ADVISED THE FO TO PREPARE FOR A POSSIBLE ENG SHUTDOWN AND A SINGLE ENG APCH AND A POSSIBLE SINGLE ENG GAR. WE EXECUTED A NORMAL APCH TO THE ARPT.