What was found
WHILE ON TAKEOFF ROLL THE FLIGHT CREW NOTED A METALLIC SMELL & EVENTUALLY BLUE SMOKE AS THEY ROTATED. SUSPECTING AN AIR CONDITION PACK FAILURE THE PACK WAS TURNED OFF & RAM AIR OPENED TO CLEAR THE SMOKE. AN EMER WAS DECLARED & ON RETURN THE SMOKE & SMELL DISSIPATED. AN UNEVENTFUL LANDING WAS ACCOMPLISHED. FOUND THE TURBINE WHEEL BEARING SEIZED ON THE ACM PN 3471A020000. THE ACM WAS REPLACED WITH A REPAIRED UNIT & ALL LEAK & OPERATIONS CHECKS PERFORMED, WITH NO DEFECTS NOTED. ACFT WAS RETURNED TO SERVICE.