ACFT RETURNS TO LAND DUE TO ENG PWR INDICATIONS.

Narrative

ON TKOF CLB THE L ENG STARTED TORQUE FLUCTUATIONS. I CALLED FOR THE QUICK REF CHKLIST (AS IS OUR COMPANY PROC). AFTER CALLING FOR THE CHKLIST; AND LEVELING THE ACFT AT 8000 FT MSL; TORQUE ON THE L ENG FELL TO 20 PERCENT AND EGT CLBED TO 680 DEGS CENTIGRADE (ABOVE MAX EGT). THE 'QRH' CHKLIST WAS PERFORMED; DURING WHICH IT WAS DETERMINED THAT THE TEMP -- TORQUE LIMITING COMPUTER WAS THE PROBABLE CAUSE; AND IT WAS SWITCHED OFF AS PER THE CHKLIST. AFTER THE 'TTL' WAS SWITCHED OFF; ALL ENG INDICATIONS AND FUNCTIONS APPEARED TO RETURN TO NORMAL. I MADE THE DECISION TO RETURN TO IAD FOR LNDG WITH BOTH ENGS RUNNING; AND MY FO SUGGESTED WE HAVE CRASH EQUIP STANDING BY; WHERE THE ENG COULD NO LONGER BE CONSIDERED 100 PERCENT RELIABLE AND AN ILS TO 300 FT ON 1/2 MI WAS TO BE MADE. I AGREED AND WE DID SO. ALL APPROPRIATE CHKLIST WERE PERFORMED PRIOR TO LNDG; AND THE LNDG WAS SUCCESSFUL. CLRING THE RWY; AFTER APPROPRIATE CHKLISTS WERE PERFORMED THE L ENG WAS SHUT DOWN MANUALLY DURING THE TAXI TO OUR GATE; TO AVOID OTHER POSSIBLE PROBS.