What was found
DTW - FLT 1461 - EN ROUTE DCA-ORD, EXPERIENCED LOSS OF NR 1 HYDRAULIC SYSTEM FLUID IN FLIGHT. COMPLIED WITH ALL RELEVANT EMERGENCY PROCEDURES. GEAR WAS EXTENDED USING ALTERNATE LANDING GEAR CONTROL. LANDED DTW WITHOUT INCIDENT. REPLACED O-RING ON NR 1 HYDRAULIC PUMP FOR NR 2 ENGINE PRESSURE LINE. BAD O-RING. PERFORMED OPERATIONAL AND LEAK CHECK. OPERATIONS AND LEAK CHECK GOOD. RESERVICED NR 1 HYDRAULIC SYSTEM. PERFORMED MAIN LANDING GEAR SELECTOR VALVE RESET PROCEDURE. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)