What was found
(CAN) PILOT REPORTED LOSS OF NR 1 SYSTEM HYDRAULIC FLUID, WITH A RESULTING 0 DEGREE FLAP LANDING AT DEPARTING AIRPORT. CREW WAS NOT DECLARED EMERGENCY LANDING, BUT THE AIRPORT WAS PREPARED AS IF THEY WERE DECLARED. FOUND GROUND CART RETURN PORT O-RING BROKEN. O-RING REPLACED IAW AMM:20-20-11-40-801, REV 52. DUE TO OPERATION OF EDP 1 WITHOUT HYD FLUID AND EVIDENCE OF METAL PARTICES IN HYD SYS 1 FILTERS. EDP 1 REPLACED IAW AMM 29-11-01-000/400-801, REV 52. FLUSHING OF HYD SYS NR 1, FULL FLUSHING, CARRIED OUT WITH FILTERS REPLACEMENT IAW AMM 29-10-00-280-802, REV 52. HYD SYS 1 SERVICING CARRIED OUT IAW AMM 12-10-29-611-801, REV 52 OPT OF HYD SYS NR 1 IAW AMM 29-11-00-710-801, REV 52 CARRIED OUT. TEST PASS.