Aerospace Technic and Technology

Under certain conditions of a helicopter flight, the main rotor can exert a rather strong effect on the tail rotor, changing its traction and power characteristics. The calculated and experimental characteristics of an isolated tail rotor under such operating conditions can differ significantly from those under conditions of interaction with the main rotor. The study of this phenomenon is an urgent task, since a change in the characteristics of the tail rotor and the conditions of its operation in the presence of the main rotor can cause a decrease in controllability margins and, as a consequence, the cause of an aircraft accident, for example, the so-called. "left rotation" of the helicopter. Since 1985, on helicopters from M. L. Mile, 42 aviation accidents occurred in units and subdivisions of the state and civil aviation of the USSR (and now Russia) due to helicopters falling into spontaneous left rotation. Over the past 10 years, 29 accidents (8 accidents and 21 accidents) have occurred for this reason. 29 helicopters were lost: 20 Mi-8, 5 Mi-24, 4 Mi-2. Experience shows that getting into an uncontrolled left rotation in almost 100% of cases ends with a collision of the helicopter with the ground and overturning it on the starboard side. The interaction of the main and tail rotor is most significantly manifested in the modes of horizontal flight with sliding at low speeds and hovering in crosswind conditions. This is due to the peculiarities of the formation of the main rotor vortex wake. In this article, the case of aerodynamic interference of the main rotor and several helicopter configurations in horizontal flight mode with the low speed with sliding (hovering in a crosswind) is considered. Using the methods of computational fluid dynamics, the degree of influence of the main rotor on the tail rotor was investigated in the described modes. The most severe operating modes of the tail rotor of each configuration have been determined. Based on the results of calculations, the most rational configuration of the tail rotor has been chosen, which has the greatest reserves of controllability under unfavorable operating conditions. The results obtained have been used in the design of a new perspective helicopter, modernization of the existing fleet, as well as improving the flight safety level.

numerical simulation; main rotor; tail rotor; aerodynamic characteristics; interference; vortex track; horizontal flight with sliding; hovering in crosswinds

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