What was found
(CAN) ON APPROACH THE FLAP CAWS LIGHT CAME ON WHEN FLAPS WERE SELECTED DOWN FOR APPROACH. THE AIRCRAFT LANDED WITH 0 FLAP SETTING. MAINTENANCE WAS ABLE TO PRODUCE AN ASSYMETRIC FLAP CONDITION ON THE GROUND THRU THE USE OF THE FLAP MAINTENANCE SWITCH. INSPECTION REVEALED THE LT INBOARD FLAP FLEX DRIVE SHAFT SHEARED IN TWO PIECES INSIDE THE HOUSING. A NEW DRIVESHAFT WAS INSTALLED AND FLAP SYSTEM RIGGED. FURTHER INSPECTION OF THE 3 REMAINING DRIVESHAFTS FOUND EXCESS CORROSION ON THE CABLE. THE AIRCRAFT WAS GROUNDED UNTIL REPLACEMENT DRIVESHAFTS WERE INSTALLED.