DURING FIRST LEG OF SEQUENCE; FLC QUESTIONED MECH ABOUT WHINING SOUND; HE SAID NOT UNUSUAL. AFTER THIRD LEG AND OVERNIGHT; FURTHER INVESTIGATION REVEALED BENT IMPELLER BLADES IN COMPRESSOR. SUSPECT ENGS STARTED WITH ICE ON BLADES.

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WE STARTED OUR TRIP SEQUENCE ON JAN/THU/96. ACFT WAS BROUGHT OVER FROM THE MAINT HANGAR BY A MECH. THE LOG INDICATED THAT THE ACFT HAD NOT BEEN FLOWN FOR 2 DAYS. PREFLT INDICATED ONLY A TRIM INDICATION PROB; WHICH WAS WRITTEN UP AND SUBSEQUENTLY CORRECTED BY A MECH. BOTH PROPS TURNED NORMALLY ON THE PREFLT. WE WERE DISPATCHED AS FLT XX TO JLN AND BROUGHT A MECH WITH US TO FIX A BROKEN ACFT IN JLN. ENG START WAS NORMAL; HOWEVER; AS RPM LEVERS WERE BROUGHT FORWARD; A SLIGHT WHINE WAS NOTICED. AFTER LNDG IN JLN WE ASKED THE MECH; NOT OUT OF CONCERN; BUT CURIOSITY ABOUT THE NOISE. WE WERE TOLD THAT IT WAS NOTHING UNUSUAL. AFTERWARDS WE WENT BACK TO STL AND THEN TO ALO FOR OUR OVERNIGHT. UPON RETURNING FROM ALO THE NEXT MORNING; WE WERE CURIOUS ENOUGH ABOUT THE NOISE TO INVESTIGATE FURTHER. MECHS WERE AGAIN ASKED TO CHK OUT THE SOUND. BENT IMPELLER BLADES WERE FOUND. DURING THE OVERNIGHT IN ALO; THE ACFT HAD BEEN IN A HEATED HANGAR AND AT NO TIME THAT THE ACFT HAD BEEN IN OUR POSSESSION HAD IT BEEN EXPOSED TO OTHER THAN LIGHT PRECIPITATION ON THE GND. WE BELIEVE THAT PRIOR TO US TAKING POSSESSION OF THE ACFT; IT WAS DAMAGED BY ICE IN THE INLETS DURING A START.