What was found
FLT 184 - INBOUND TO PIT, THE MAIN LANDING GEAR WAS SELECTED TO THE DOWN POSITION THE CREW GOT A MOMENTARY SAFE THEN UNSAFE INDICATION ON THE MLG DOWN AND LOCKED LIGHTS. ATC WAS NOTIFIED EMERGENCY WAS DECLARED. THE MLG WAS CYCLED UP AND DOWN RESULTING IN A SAFE INDICATION OF DOWN AND LOCKED. AN UNEVENTFUL LANDING WAS MADE. INSPECTION FOUND AIR HAD BEEN TRAPPED IN THE HYDRAULIC SYSTEM CAUSING A FALSE READING ON THE HYDRAULIC SIGHT GAUGE, THE HYDRAULIC SYSTEM WAS SERVICED, AN OPERATIONAL CHECK OF THE HYDRAULIC SYSTEM WAS PERFORMED NO DEFECTS WERE NOTED. AIRCRAFT RETURNED TO SERVICE. (M)