Proceedings of the Academy . prof. N. E. Zhukovsky . Issue 239 - Academy Edition, 1947 - 8 s. In-flight Variable Step Screw (VSE) has significant advantages over Fixed Step Screw (MTW). Due to the replacement of fixed-step propellers on aircraft with variable-step propellers, the flight-tactical data of the aircraft has improved significantly. But the use on HIS aircraft led, in addition to the defects inherent in them, to limit the control over the operation of the engine, which is a significant operational disadvantage. The presence of a "fiometer" on the aircraft (a device showing the angle of installation of the HIS blades in flight) eliminates this drawback and gives a number of advantages in the operation of the aircraft.