As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOTH RT AND LT ALTERNATOR BELTS BROKE IN FLIGHT, POSSIBLE CAUSE WAS BOTH ENGINES MAY HAVE BEEN STARTED WITH NOSE COWL PLUG WOOL BLANKETS INSTALLED, THUS, BINDING UP THE PULLEYS AND/OR BELTS WHILE THE REST OF THE MOVING PARTS SEVERELY CUT INTO THE BELTS. BOTH BELTS HAD LESS THAN 10 HOURS TIME IN SERVICE. (K)