What was found
PERFORMED AN EMERGENCY DESCENT DUE TO RED CABIN ALTITUDE CAS MESSAGE. WHILE DESCENTING FROM FL 470 TO 340, CYCLED ALL ANTI ICE SWITCHES TO THE ON POSITION. RECEIVED AMBER CABIN ALTITUDE CAS MESSAGE FOLLOWED BY RED CABIN ALTITUDE CAS MESSAGE. DONNED MASK, PERFORMED EMERGENCY DESCENT, AND TURNED OFF ALL ANTI ICE SWITCHES. CABIN ALTITUE REACHED A MAX OF 11,000 FT AND STABILIZED OUT SHORTLY AFTER LEVELING AT FL340. AIRCRAFT LANDED WITHOUT INCIDENT. FOUND LT LP REGULATING VALVE FAULTY AND NOT REGULATING PROPERLY. REPLACED LT LP REGULATING VALVE. GROUND OPS CHECK GOOD.