What was found
(CAN) PILOT REPORTED UNCOMMANDED IN-FLIGHT LH ENGINE SHUT-DOWN. WAS CRUISING STRAIGHT AND LEVEL AT APPROX. 80% POWER, WHEN OVER THE PERIOD OF ONE-MINUTE POWER GRADUALLY REDUCED TO 30%, PROPELLER FEATHERED, ENGINE SHUT-DOWN. TESTED SERVICEABLE AND NORMAL ON GROUND, BOTH ECU`S TESTED NORMAL, GEARBOX FOUND CLEAN INTERNALLY. DOWNLOADS SENT TO AUSTRO ENGINE, WIRING AND ELECTRICAL CHECKS BEING INVESTIGATED AND CHECKED BY OPERATOR`S MAINTENANCE FACILITY AND ALSO BY AUSTRO ENGINE. A SIMILAR OCCURRENCE IN PAST WAS RELATED TO ELECTRICAL.