Abstract: The principle of control of a turbosupercharged piston engine wih Turbo Control Unit(TCU) is described.The parameters:ambient air pressure,engine speed and the throttle position(Tp) are detected and processed by TCU,which controls the waste gate of turbosupercharger.The charged air pressure and temperature are fed back.The Tp is setting by the pilot.TCU maintains the power of engine under critical altitude and keeps turbo speed beyond it.The engine performance can be calculated under standard and nonstandard atomosphere condition.The results coincide with the datum from the production corp.Bombardier Rotax,Austria,and the performance above critical altitude can be calculated either.