What was found
ON CLIMBOUT RECEIVED MLG DOOR DISAGREE INDICATION AFTER MLG RETRACTION. PERFORMED MLG DISAGREE CHECKLIST: LT MLG GREEN WITH GEAR HANDLE OFF, NOSE & RT MAIN BLANK. ACFT FEEL INDICATED LT MLG NEVER RETRACTED, TURNED BACK & LANDED WITHOUT EVENT. MX R & R MLG DOOR-OPERATED GEAR SEQUENCE VALVE, DID NOT CORRECT PROBLEM. AFTER DUPLICATING PROBLEM & GETTING MLG TO RETRACT BY APPLYING WEIGHT TO BACK OF TRUCK, MX REPLACED LT MLG TRUCK POSITIONER ACT, AS A PRECAUTION REPLACED LT TRUCK TILT PROXIMITY SENSORS 1 & 2, PROBLEM STILL PERSISTS. R & R DOWNLOCK ACTUATOR, OPS & LEAK CK GOOD, GEAR CYCLED W/O DEFECT. VENDOR BENCH TEST & TEARDOWN OF DOWNLOCK ACTUATOR CONFIRMED FAILURE OF UNIT.