What was found
DURING CRUISE, SLOW AIRSPEED, FIRST NOTICED AT 210 KTS, NOTICEABLE VIBRATION. TRIED PUTTING ANVS ON PAUSE WITH NO CHANGE. VIBRATION WORSENED DURING POWER REDUCTION. PROPS WERE AT 850. TORQUE ABOUT 50%. REMOVED FROM SERVICE. IAW WO 247742, 00001 THROUGH 00004. NR 1 PROP BALANCE SOLUTION REQUIRED 350G OUT OF LIMITS. COMPLIED WITH INSPECTION AFTER REPORT OF UNUSUAL VIBRATION IAW AMM 05-50-12-200-801, STEPS 1-4 B, AND 5. NO OTHER DEFECTS NOTED. REMOVED FROM SERVICE. REPLACED THE NR 1 PROPELLER ASSEMBLY. RETURNED TO SERVICE.