Postaccident Examination Of The Airplane Revealed That The Carburetor Heat Levers Remained In The OFF Position Analysis: The flight instructor and commercial pilot receiving multi-engine instruction intentionally shut down the left engine after they performed one-engine-inoperative (OEI) training. They restarted the left engine successfully on the second attempt and proceeded back to the departure airport. During the descent, the pilots noticed that the airplane required additional right rudder to maintain control and then noticed a decrease in left engine coolant temperature and rpm.