What was found
(CAN) A LARGE AMOUNT OF STATIC ELECTRICITY WAS OCCURRING DURING SLINGING OPS ON LONG LINE. WHILE SLINGING A LOAD, THE STARTER/GENERATOR FOR ONE ENGINE WENT OFF-LINE. PILOT RESET THE GENERATOR AND IT CAME BACK ON-LINE. A SECOND BUILD-UP OF STATIC FOLLOWED BY A DISCHARGE CAUSED A COMPLETE POWER FAILURE (NO BATTERY, NO GEN). PILOT COULD NOT RELEASE THE LOAD ELECTRICALLY AND FUEL BOOST PUMPS INOPERATIVE. UNCOMMANDED ENGINE POWER ROLLBACK, POSSIBLY CAUSED BY FUEL BOOST PUMPS INOPERATIVE.