What was found
DURING FLIGHT, AIRCRAFT WAS DOING TOUCH AND GO LANDINGS. PILOT PULLED BACK ON THROTTLE FOR MORE POWER BUT COULD NOT MOVE THROTTLE. LANDED SHORT OF RUNWAY, IN A FIELD. INVESTIGATION OF THROTTLE , FOUND CARBURETOR STUCK IN IDLE POSITION. REMOVED CARBURETOR AND FOUND COPPER BUTTERFLY RUBBING UP AGAINST INTERIOR OF THROTTLE ASSEMBLY.