What was found
CREW REPORTED HYD 3 LOW PRESSURE CAUTION MESSAGE AND INBOARD GROUND SPOILERS CAUTION MESSAGE AFTER TAKEOFF. CREW RETURNED TO FIELD AND LANDED SAFELY. AIRCRAFT TOWED FROM RUNWAY DUE TO INOPERABLE NOSE WHEEL STEERING AND PASSENGERS TAKEN BY BUS TO TERMINAL. MAINTENANCE INSPECTED AND FOUND LEFT AILERON NUMBER 3 PCU (POWER CONTROL UNIT) LEAKING. MAINTENANCE REMOVED AND REPLACED LEFT AILERON PCU FOR NUMBER 3 SYSTEM AND PERFORMED CHECKS USING AIRCRAFT MAINTENANCE MANUALS. AIRCRAFT RELEASED FOR SERVICE.