What was found
AFTER TAKEOFF FROM AVB EN ROUTE TO FRA, WHEN THE LANDING GEAR WAS RETRACTED THE MAIN GEAR DOOR NOT LATCHED LIGHT REMAINED ILLUMINATED. THE FLIGHT CREW CYCLED THE LANDING GEAR WITH THE WARNING INDICATION REMAINING THE SAME. THE FLIGHT CONTINUED TO FRA FOR AN UNEVENTFUL LANDING. MAINTENANCE INSPECTED THE AIRCRAFT GEAR DOOR WARNING SYSTEM AND LUBRICATED THE LEFT GEAR DOOR UPLATCH MECHANISM AND PERFORMED A SUCCESSFUL GEAR SWING IN ACCORDANCE WITH THE MAINTENANCE MANUAL.