As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 2528 AIRCRAFT RETURNED TO FIELD DUE TO, LEFT ENGINE FAN VIBRATION 1.6 AFTER TAKEOFF, INCREASED TO 2.2 DURING CLIMB AT 25K, REDUCED TO AS LOW AS 1.6 WHEN POWER WAS AT IDLE. DEFINITE AIRFRAME VIBRATION FELT AND INCREASE CABIN NOISE. AIRCRAFT LANDED WITHOUT INCIDENT. REMOVED AND LUBED NR 1 ENGINE FAN BLADES AND REINSTALLED BLADES AND SPINNER IAW CRJ TASK 72-21-02-400-801.