What was found
ON DESCENT, A-SYSTEM HYDS FAILED, A/C WAS TOWED OFF RUNWAY TO GATE. MX FOUND CHECK VALVE BLOWN OUT OF A-SYSTEM HYD PRESSURE MANIFOLD, R / R A-SYSTEM HYD PRESSURE MODULE ASSY IAW BMM. DUE TO LOSS OF FLUID REPLACED A-SYSTEM HYD EDP IAW T/C R5M29001, A-SYSTEM HYD ELECTRIC PUMP IAW T/C R4M29002, & A-SYSTEM HYD FILTERS, OPS & LEAK CHECK GOOD. TEARDOWN ANALYSIS OF HYD PRESSURE MODULE ASSY CONFIRMED FAILURE OF UNIT. FOUND UNIT IN OVERALL WORN CONDITION REQUIRING OVERHAUL, CHECK VALVE MISSING & WRONG P/N PRESSURE SWITCH INSTALLED. INSTALLED A NEW CHECK VALVE & REPLACED PRESSURE SWITCH, 10 EACH O-RINGS, 5 EACH BACK-UP RINGS, AND FILTER ELEMENT.