What was found
SYSTEM 'C' HYD RSVR QTY LOW AND DECREASING. SWITCHING PUMP OFF DID NOT STOP FLUID LOSS. REF MANUAL GEAR EXTENSION, ATM TURNED OFF FLUID LOSS STOPPED AT AROUND THREE-EIGHTHS TANK QTY. AIRCRAFT LANDING NORMAL. FOUND PIN HOLE LEAK IN HYD C-CHECK SYSTEM RETURN LINE IN LEFT WING. LINE REPAIRED BY 'PERMASWAGE' COUPLING IAW 20-29-04 LEAK CHECK GOOD. AIRCRAFT RETURNED TO SERVICE. (M)