What was found
A .2500 INCH X .5000 INCH PIECE OF FOD (A SHIM GLUED ONTO THE RT THROTTLE LEVER TO (MAKE) THE SWITCH ,( NOT INSTALLED BY CURRENT OPER)FELL ONTO A HOT TERMINAL OF THE RT THROTTLE SWITCH AND GROUND CAUSING AN ELECTRICAL ARC WHICH RESULTED IN A PRECAUTIONARY LANDING IMMEDIATELY AFTER ROTATION AT TAKEOFF, DURING DAYTIME OPS. DAMAGE WAS LIMITED TO A BLOWN DIODE, WHICH RESULTED IN A FALSE GEAR WARNING LIGHT. AFTER RETRACTION OF LANDING GEAR, THROTTLE SWITCHES WERE ADJUSTED, DIODE WAS REPLACED AND A HARD LANDING INSPECTION WITH 12 CYCLES WAS ACCOMPLISHED. AIRCRAFT WAS THEN RETURNED TO PART OPS. (NM11200502069) (NM11200502176)