Parameterization and methods to ensure durability of bearingless main rotors (including rigid rotors)

Аuthors

Pavlenko N. S.

National Helicopter Center Mil & Kamov, 26/1, Garshina str., Tomilino, Moscow region, 140070, Russia

e-mail: npavlenko@mi-helicopter.ru

Abstract

Parameterization algorithms for main structural elements of helicopter BMR, i. e. bearingless main rotor, (including rigid rotors) is a multiphase task.

The first stage involves the static calculations and construction of blade resonance diagram.

The calculations of alternative stresses is the content of the second phase of the parameterization.

The calculations of the local strength and stiffness is the final phase of calculations based on finite-elements model.

This article is devoted to the first stage of BMR parameters selection algorithm and BMR durability analysis. Its main results are also used at subsequent stages of calculations and design.

The first stage contains calculations of rotor hub stiffness matrix, blade free vibration modes and frequencies, construction of blade resonance diagram, blade deformation calculations and constant stresses caused by centrifugal force impact during the flight, and blade droop caused by gravity when the helicopter is on the ground.

To provide static strength, stability (self-oscillations of flutter type) and dynamic strength of bearingless main rotors its essential to use more complicated calculation models and methods than those used for conventional hinged rotors, due to the complexity of the boundary conditions, used to solve differential equations of natural and forced oscillations of a blade. The paper proposes the solution of this problem by introducing hub stiffness matrix to analytic model, and offers the methodology of its elements calculation.

The article describes the design variant of light helicopter bearingless main rotor and presents the results of of BMR rotorhead main parameters selection, which can be generalized for a wide range of designs.

Keywords:

main rotor, vibrations, oscillations, blade deformation, torsion, differential equations

References

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3. Kartashov V.B., Michylox S.A., Nikolaev E.I., Khlebnikov A.A. Mathematical modeling of loading of bearingless main rotor with elastic elements of torsional type. 25th European rotorcraft forum. Rome-Italy September, 1999, pp. 14-16.

4. Carta Franklin O., Niebanck Charles F. Prediction of rotor instability at high forward speeds. United Aircraft Corporation Sikorsky Aircraft Division, Stratford, Connecticut, 1969, vol. III, p. 88.