What was found
EN ROUTE DEN-DFW, ON TAKEOFF ROLL, HEAR A FAN TYPE NOISE SIMILAR TO INSTRUMENT COOLING FAN CYCLING ON/OFF SEVERAL TIMES. PAST V1 HAD BLAST OF AIR AND SAW SMOKE (GRAY) IN COCKPIT WITH PACK FLOW OFF. TURNED LEFT PACK OFF, SMOKE STOPPED IMMEDIATELY. RETURNED TO DEN AND LANDED WITHOUT INCIDENT. INSPECTED COCKPIT, CABIN AND TAIL SECTION OF AIRCRAFT. NO SMOKE OR ODOR DETECTED. REPLACED LT PACK HEAT EXCHANGER COOLING FAN. SYSTEM GROND CHECKED NORMAL OPERATION. (M)