What was found
DURING TRAINING FLIGHT, AFTER 2ND TOUCH & GO LANDING, GEAR UNSAFE LIGHT STAYED ON AFTER THE GEAR WAS RETRACTED. LANDING GEAR TOOK MUCH LONGER TO EXTEND & LOCK THAN NORMAL. ACFT LANDED WITHOUT INCIDENT. UPON INSPECTION, MX FOUND HYD FLUID ON THE LT FLAP AREA. THE HYD RESERVIOR WAS EMPTY & HYD FLUID DRIPPING FROM THE LT HYD PUMP DRAIN. HYD FILTERS WERE CHECKED AND THE LT FILTER HAD PIECES OF SEAL MATERIAL IN IT. REPLACED FILTER, SERVICED & BLED HYD SYS IAW MM. OPS CHECK WITH RUNING ENGINES SHOWED LT PUMP FAILED PRESSURE CHECK AND HYD FLIUD COMING OUT OF LT PUMP DRAIN. PUMP TO BE REPLACED.