What was found
SHORTLY AFTER TAKE OFF, CREW WITNESSED THE LT ENGINE INDICATIONS STARTING TO ROLL BACK. THIS INDICATION HAPPENED BETWEEN 500 & 1000 FOR AGL. FELT THE DECELERATION OF THE ACFT. THE FLIGHT CREW REPORTED THERE WERE NO CAUTION OR WARNING LIGHTS PRESENT DURING THIS EVENT. THE ENGINE STOPPED ROLLING BACK AT IDLE SPEED WHERE IT REMAINED FOR THE REST OF THE FLIGHT. THERE WAS NO CONTROL OF THE THRUST ON THE LEFT ENGINE AFTER THE ENGINE STARTED ROLLING BACK FROM THE TAKE OFF THRUST SETTING. THE FLIGHT CREW AFTER ATTEMPTING TO REGAIN THRUST INPUT TO THE ENGINE LEFT THE THRUST LEVER AT IDLE FOR A LEFT TURN DOWNWIND AND LANDING AT THE SAME AIRPORT THEY DEPARTED FROM KCHA. THERE WAS NO ABNORMAL NOISE OR VIBRATIONS.