What was found
(CAN) THE FLIGHT CREW DECLARED AN EMERGENCY LANDING IN YOW, DUE TO A NUMBER 1 (ONE) HYDRAULIC SYSTEM FAILURE. THE FLIGHT LANDED WITHOUT INCIDENT AND WAS ABLE TO TAXI NORMALLY TO THE ARRIVAL GATE. LEVEL FL400 "HYD 1 LOW QTY" MSG. QUANTITY WAS "0". SYSTEM PRESS SLOWLY DECREASED UNTIL "HYD 1 LO PRESS" & "HYD 1 EDP FAIL" MSGS APPEARED SIMULTANEOUSLY. ELECTRIC HYD PUMP TURNED OFF MANUAL AFTER SYS PRESS DROPPED BELOW 2000 PSI. LH ENGINE EDP REPLACED PER AMM 29-11-01 AMM 05-50-23-200 PROCEDURE