B737-300 CREW HAD ENG FAN BLADES THAT WERE DAMAGED.

Narrative

UPON SHUTDOWN AT GATE IN ZZZ; MECH ADVISED THERE WAS DAMAGE TO SEVERAL FAN BLADES ON #2 ENG. WE HAD FLOWN THE SAME PLANE THE NIGHT BEFORE. DEP ARPT WX: LOW OVC; LOW VIS; FZFG; -8C. ARR ARPT WX: 3500 OVC; GOOD VIS; 8C. AFTER PUSHBACK AND STARTING BOTH ENGS (THERMAL ANTI ICE ON) TAXIED TO DEICE PAD. DEICED TYPE I FLUID. DURING DEICE A MILD VIBRATION WAS FELT ON #2 ENG. VIBRATION CEASED ON TAXI TO RWY. PERFORMED 1ST RUN UP ON RWY 34 (70%; 30 SEC) AS 30 MIN HADN'T YET ELAPSED. NO VIBRATION FELT BUT #2 VIB IND SHOWED HIGH VIB. AFTER 30 SEC IDLE SELECTED. AFTER PAUSE; ANOTHER RUN UP PERFORMED. NO VIB FELT AND #2 IND MOVED TO LESS THAN 2. WE CONCLUDED ICE SHED AND TKOF WAS SAFE. TKOF UNEVENTFUL WITH THERMAL ANTI ICE AND WING ANTI ICE USED IN CLB TO 9800 FT MSL. LATER THERMAL ANTI ICE AND WING ANTI ICE USED PER SOP. SOME RIME OBSERVED ON WIPER NUT. ENG IND NORMAL. TRIP UNEVENTFUL. NO DAMAGE OBSERVED ON WALK AROUND IN ZZZ1. CLB; CRUISE AND DSCNT NORMAL. THERMAL ANTI ICE USED ON APCH TO ZZZ THRU THIN LAYER AND UNTIL SHUTDOWN. UPON SHUTDOWN; AMT ADVISED AND I OBSERVED VARYING DAMAGE TO 8 FAN BLADES (BENT) AT VARYING LOCATIONS ON THE CIRCUMFERENCE OF FAN FACE. PLANE TAKEN OUT OF SVC FOR REPAIR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRPLANE WAS DEICED PRIOR TO THE FLT INTO ZZZ AND BOTH ENGS AND LNDG GEAR WERE DEICED ON THE GATE THEN AFTER PUSHBACK WAS TAXIED TO A DEICING AREA FOR AIRFRAME DEICING. THE RPTR STATED ON TERMINATION OF THE FLT #2 ENG WAS FOUND TO HAVE FAN BLADE TIP DAMAGE. THE RPTR STATED NO VIBRATION WAS INDICATED OR DETECTED IN FLT AND THE #2 ENG OPERATED NORMALLY. THE RPTR SAID HE HAS NO IDEA HOW THE ICE COULD FORM AFTER DEICING AND ONLY DAMAGE #2 ENG. THE RPTR STATED COULD IT BE POSSIBLE TO FORM ICE ON ONE ENG WHILE TAXIING WITH A PREVAILING WIND BLOWING ON #2 ENG?