What was found
AIR TURN BACK DUE TO BLEED 1 OFF AND BLEED 1 FAIL CAS. RAN QRH, TURNED BLEED 1 SWITCH OFF FOR 60 SECONDS. DURING 60 SECOND PERIOD, BLEED 2 OFF AND BLEED 2 FAIL CAS ILLUMINATED. PERFORMED EMERGENCY DESCENT; DECLARED EMERGENCY; MANUAL PAX MASK DEPLOYMENT. CABIN ALTITUDE SEEN AT 19,000'. AT 20,000’ RE-PERFORMED QRH AND ALL BLEED FAULTS CLEARED. AIRCRAFT LANDED SAFELY AT KNEW. REPLACED RH PRECOOLER DUE TO BROKEN INTERNAL FIN. COMPLETED SL505-36-0003 REV 2. OPS AND LEAK CHECK GOOD IAW PH 300 AMM 36-11-05/400 AND SL505-36-0003 REV 2.