What was found
DURING CRUISE ECAM INDICATED YELLOW SYSTEM LOW PRESSURE. FOLLOWED ECAM AND QRH AND TURNED OFF PUMP. FLUID STABILIZED SLIGHTLY ABOVE THE RED DOT. DECLARED EMERGENCY WITH APPROACH CONTROL AND LANDED UN EVENTFULLY. FOUND YELLOW SYSTEM NON RETURN CHECK VALVE EXTRACTOR LEAKING. REF AIRBUS IPC 29-13-03-23. REMOBED AND REPLACED NON RETURN EXTRACTOR CHECK VALVE O-RING PER AMM 29-13-34-04. SERVICED YELLOW HYD SYSTEM PER AMM 12-12-29-00. NO LEAKS NOTED. A/C OK FOR SERVICE.