What was found
LAS - IN CRUISE AND DESCENT LEFT AND RIGHT MAIN GEAR DOORS OPENED. HEARD AND FELT THUMP AS WELL AS LT & RT GEAR UNSAFE LIGHTS. AIRSPEED WAS 255K USED ALT GEAR EXTENSION TO LOWER GEAR. UNEVENTFUL LANDING. TOWED AIRCRAFT FROM THE RUNWAY. FERRY TO PDX FOR REPAIR. FOUND FAULT LGDRCL RIGGING GAP TOO LARGE. RIGGED SENSOR S17. CLEARED FAULT HISTORY. PERFORMED OPERATIONAL CHECK FLIGHT WITH NO DEFECTS. EXTENSION RETRACTION CHECK OF GEAR GOOD. RETURNED TO SERVICE. NO PARTS REPLACED.