What was found
LOST B HYD SYS ENROUTE. "HYD B VOL LOW" CAS MSG AROUND FL 210. DURING DESCENT IN TO PHX "RUDDER STBY FAIL" CAS ILLUMINATED. VERIFIED DISCREPANCY, CLEANED RESIDUAL HYD FLUID FROM RUDDER TO JUST FWD OF TAILCONE ACCESS DOOR. FOUND HYD FLUID COLLECTING AT THE BOTTOM OF THE "HYD B" PCU. RAN HYDS & CYCLED RUDDER & FOUND PCU LEAKING. REMOVED AND REPLACED RUDDER PCU "B" IAW MM 27-22-00. OPS & LEAK CHECK GOOD. "RUDDER STANDBY FAIL" MESSAGE WAS A RESULT OF LOW RESEVOIR. SERVICED RESEVOIR AND OPS CHECK OF RUDDER STANDBY SYSTEM GOOD, IAW MM 29-20-05.