What was found
(CAN) AIR TURN BACK DUE LANDING GEAR TILT AND MONITOR MESSAGES ON TAKEOFF. REPLACED PSEU PER FIM TROUBLESHOOTING PROCEDURE. SECOND TAKEOFF SAME PROBLEM RECURRED. FOUND HYDRAULIC LEAK ON TILT ACTUATOR HOSE. PROXIMITY SENSOR SWITCHES CHECKED, RESISTANCE ALL NORMAL. THIRD TAKEOFF SAME PROBLEM. AIRCRAFT GROUNDED. PSEU REPLACED. ALL SYSTEMS NOW NORMAL. AIRCRAFT RETURNED TO SERVICE.