As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA - BEFORE START, THE NR 1 HYDRAULIC QUANTITY READ 100 PERCENT. AFTER START, QUANTITY DROPPED TO 50 PERCENT. ALSO AFTER START, THE STANDBY PRESSURE FLUCTUATED. MAINTENANCE BLED THE NR 1 HYDRAULIC SYSTEM IAW Q400 29-10-00 AND SERVICED THE SYSTEM IAW 12-10-29. HYDRAULIC SYSTEM OPERATES NORMALLY AND AIRCRAFT RETURNED TO SERVICE.