What was found
AFTER APPROXIMATELY 15 MINUTES OF LEVEL FLIGHT AT FL310 COCKPIT FILLED WITH SMOKE. POPPING AND SPARKING OCCURRED AT THE JUMP SEAT (OBSERVERS) RT SHOULDER AREA. FOUR AC BUS CIRCUIT BREAKERS POPPED BEHIND CAPTAINS SEAT. AIRCRAFT DIVERTED TO BHM. FOUND 15 WIRES DAMAGED TO AC POWER SYSTEM (REF W/D 34-51-01). REPLACED ALL DAMAGED WIRES PER 20-00-13 AND 20-10-03. REPLACED 6 LT AC BUS BREAKERS AND 6 RT AC BREAKERS AS PRECAUTION. DAMAGE TO WIRES CAUSED BY CHAFING ON SCREW. POWERED UP AC ELECTRICAL SYSTEM. CHECKS NORMAL.