Analysis of hinge moments occurring on helicopter main rotor blades

Аuthors

Kruchinin M. M.^*, Artamonov B. L.^**

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

*e-mail: mmkruchinin@mi-helicopter.ru
**e-mail: k102@mai.ru; abl-6124554@yandex.ru

Abstract

The paper considers computational results of moments relative to main rotor axial hinge caused by action of inertial and aerodynamic forces occurring on the blades. The computational method is based on the generalized disk vortex theory of rotor in an oblique flow in its most simple version, when the air load over rotor disk is assumed constant in computing inductive speed vector components. Flapping movement coefficients of hinge-suspended in thrust plane rotor blades are defined by analytical relations with an accuracy to the first harmonic of Fourier series. This assumption reduces the problem of hinge moments calculation with specified rotor control law to the method of successive iteration on thrust force ratio.

As an example, the authors considered the rotor blades operation of helicopters Mi-34 and Mi-28. They studied the change of hinge moment value depending on the blade azimuthal position, and evaluated each components contribution to it.

The wobble plate rod strain dependence on flight speed, blade angles and control action was analyzed. It was established that with wobble plate ring deviation in forward longitudinal direction law of azimuthal strain variation demonstrates harmonic character with pronounced maximum near the retreating blade. With wobble plate ring deviation in transverse direction the similar dependence is of the same character, but its amplitude is negligible compared to longitudinal control.

Calculations were executed for helicopter main rotors with various structures of a hub and blades. The results were compared with experiments and calculations of the other authors. It is shown that mathematical model of absolutely rigid blade combined with disk rotor vortex model allows evaluate control system loading level at various helicopter flight modes with adequate accuracy. The ways of model improvement allowing define the obtained results more exactly are outlined.

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Keywords:

helicopter, main rotor blade, control system, hinge moment, rod loads, mathematical modeling

References

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