What was found
DURING CRUISE FLIGHT AT FL200 PILOT NOTICED WHITE SMOKE IN COCKPIT, PILOT DONNED OXYGEN MASK & SMOKE GOGGLES, NOTIFIED ATC OF SITUATION & PERFORMED EMER PROCEDURES IN QRH. PILOT TURNED OFF BOTH BLEED AIR SOURCES & STARTED EMER DESCENT, PILOT LANDED WITHOUT FURTHER INCIDENT. TROUBLESHOOTING REVEALED THE LT ACM HAS AN INTERNAL LEAK CAUSING THICK WHITE SMOKE WITH BLEED AIR SYS ON. DEFERRED ACM, WE WILL SUBMIT A FOLLOW UP REPORT AFTER WE RECEIVE THE TEAR DOWN REPORT.