Abstract: Turbine for flowing fluid, especially a turbine having a vertical power output shaft and formed with several wings projecting radially out from the power output shaft, which wings are rotatable over an angle of about 90° about horizontal shafts extending closely adjacent and along the trailing edge of the wing as seen in the flow direction, so that the wings, in an operative, first position, are positioned at right angle to the flowing fluid and in a second, non-operative position, are located horizontally or nearly horizontally and on plane with the flowing fluid. Each wing is formed with a fin portion for catching, at a very early stage of an operation cycle, flow medium passing by and to thereby initiate a pressing down of the wing to a portion at right angle to the flow medium for, as far as possible, maintaining the flow medium against the wing during the active moving path thereof.