Development of the technical solution to prevent a single-rotor helicopter from entering uncontrolled rotation

Abstract

The phenomenon of a single-rotor helicopter entering an unintended left rotation with the further development of an uncontrolled turn periodically arises while operating this type of helicopter, both in Russia and abroad. This phenomenon can lead to serious aviation incidents and even disasters. Currently, there is no unambiguous justification for the phenomenon of "uncontrolled" U-turn and the causes of occurrence, since the operating conditions of the tail rotor (TR), especially at low-speed modes, depend on many factors. These factors include, firstly, wind direction and speed, T/R “vortex ring", as well as the impact of the main rotor vortex trace. One of the explanations for this phenomenon lies in the special specifics of the yaw trim of a singlerotor helicopter, which is provided by the tail rotor. These papers emphasize that the change in wind speed and direction which affects the helicopter, and the TR is the main cause of the unintentional left turn. Currently, there are no tools and methods for determining the wind effect on the TR in order to develop a warning signal for a pilot about a change in the nature of the TR flow and an alert about the occurrence of uncontrolled rotation. This paper proposes the system for measuring the TR air flow using a special sensor that allows us to measure the inductive air flow velocity of a small value in an aerodynamic way without additional various electronic transformations that are inherent in conventional Pitot tube probes. The use of such a measurement system makes it possible to identify the probability of a dangerous situation, to inform the pilot and help him take the proper actions.