What was found
DURING CLIMB OUT FOR A STAGING FLIGHT, CREW PULLED THROTTLE BACK AT APPROX 4000 FT, NR 1 ENGINE MADE A POPPING NOISE, FOLLOWED BY TORQUE DECREASING TO 2100 FT LBS, FOLLOWED BY AN ADDITIONAL POPPING NOISE FROM THE NR 1 ENGINE. THE CREW PULLED THE POWER ON THE NR 1 ENGINE TO IDLE, DECLARED AN EMERGENCY, RETURNED AND LANDED WITHOUT FURTHER INCIDENT. DURING SHUTDOWN, CREW HEARD A GRINDING NOISE FROM NR 1 ENGINE AND FELT SLIGHT VIBRATION IN CONTROL YOKE. INSPECTION REVEALED SEVERAL COMPRESSOR BLADES WITH CURL-UP AND SHARP EDGES. ALSO COMPRESSOR SECTION DID NOT ROTATE FREELY WITH ACCESORIES REMOVED AND AN OCCASIONAL GRINDING NOISE WAS HEARD DURING ROTATION. OPEN