What was found
DURING APPROACH INTO MSP, THE LEFT MAIN LANDING GEAR UNSAFE LIGHT ILLUMINATED ON GEAR EXTENSION. CONFIRMED VISUALLY THROUGH PERISCOPE THAT GEAR WAS DOWN AND LOCKED. EMERGENCY EQUIPMENT WAS CALLED OUT AS A PRECAUTION AND AIRCRAFT LANDED WITHOUT INCIDENT. REPLACED THE LEFT MAIN GEAR DOWNLOCK SWITCH. OPERATIONAL CHECK OK ON GEAR SWING. AIRCRAFT RETURNED TO SERVICE.