What was found
CREW REPORTED DURING PREFLIGHT PACK 2 SHUT DOWN, SMOKE FILLED THE FLIGHT DECK AND FUSELAGE. PACK 2 NO LONGER TURNS ON. CORR ACTION MX PERFORMED VISUAL INSPECTION OF PACK 2 FOUND WHITE POWDER AROUND DUCTS ON AIR CYCLE MACHINE. RAN PACK 2 FAINT SMOKE STARTED TO COME OUT OF ALL VENTS SHUT DOWN IMMEDIATELY AFTER SEEING SMOKE. REMOVED AND REPLACED PACK 2 ACM. OPS CHECKS GOOD RAN PACKS CYCLING 1 & 2 EVERY 10 MINS FOR 30 MINS NO SMOKE. AIR BLOWS COLD, NO