What was found
AFTER TAKEOFF, LANDING GEAR FAILED TO RETRACT. PRIOR TO TAKEOFF, PILOT REPORTED FLAPS SEEMED SLUGGISH. AFTER RECYCLING GEAR SEVERAL TIMES, SYSTEM APPEARED TO BE WORKING PROPERLY. AFTER NEXT TAKEOFF, GEAR RETRACTED NORMALLY, BUT WHEN GEAR WAS SELECTED DOWN, GEAR FAILED TO EXTEND. GEAR WAS BLOWN DOWN SUCCESSFULLY. REPLACED VALVE, OPERATIONAL CHECKED OKAY.