As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX - AIRCRAFT RETURNED TO FIELD WHEN AFTER TAKEOFF THE CREW RECEIVED A RUDD FULL PRESS CAUTION LIGHT FOLLOWED BY A RUDD PRESS CAUTION LIGHT. BOTH LIGHTS WENT OUT WHEN FLAPS WERE AT 15 DEGREES PRIOR TO LANDING. MAINTENANCE INSPECTED THE AIRCRAFT AND FOUND AIR IN THE HYDRAULIC SYSTEM. SYSTEM WAS BLED AND SERVICED. OPERATIONAL CHECKS WERE GOOD AND THE AIRCRAFT WAS RETURNED TO SERVICE.