What was found
AFTER START UP AND TAXI OUT, RUNNING ALL CHECK LISTS, CLEARED FOR TAKE OFF. MONITORED THE ENGINES ON TAKEOFF. HAD NO WARNING LIGHTS AND TAKE OFF POWER WAS SET . DEPARTED. ABOUT 1000 FT OFF THE GROUND THE NR 1 ENGINE STARTED TO SPOOL BACK. IT TOOK MAYBE 10-15 SECONDS IT WASN'T ABRUPT. BUT THE FUEL GAUGE WENT FROM ABOUT 2000 LBS AN HOUR TO 400 AS N1 AND N2 AND ITT ROLLED BACK ON NR 1. EVEN WITH THE THROTTLE AT FULL POWER ON NR 1, IT WAS PRODUCING IDLE POWER. IT NEVER FULLY FAILED OR WENT TO ZERO N1. INFORMED TOWER AND WHERE CLEARED TO LAND. DECLARED AN EMERGENCY. AFTER LANDING, CUT OFF THE NR 1 ENGINE.