helicopter main rotor
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helicopter main rotor

helicopter main rotor

 

 

Helicopter rotor blades and consists of a sleeve.

The blades create lift needs.

Sleeve a kinematic mechanism for the movement and angular movements of the blade in the vertical and horizontal plane under the influence of aerodynamic and inertial forces, as well as the rotation of the blade to control its buoyancy.

HB creation process is performed in sequence:

  • 1. The choice of the main parameters of HB: diameter D, the number of blades g; filling a; peripheral rotation speed with D.

  • 2. Aerodynamic layout of the blade (external appearance of the blade): choice of shapes in plan; the shape of the section profiles, the relative thickness of the sections c and the distribution of the twist φ along the radius of the blade.

  • 3. Determination of the limiting angles of deflection of the blade φ, (3, £, when controlling the helicopter in all design modes of its flight.

  • 4. Blade design:

 

- the choice of the material of the spar and the frame, the shape of the spar, taking into account the previous experience and the existing design, technological and operational restrictions; formation of the spar section along the chord and radius of the blade based on static strength calculation;

 

Helicopter rotor 2

Helicopter rotor pictures

 

- correction of the mass-stiffness characteristics of the blade in order to detune from resonance at the operating frequencies of rotation of the NV and to ensure sufficient reserves of aeroelastic stability (calculated types of flutter, divergence, “ground” resonance).

 

  • 5. Design of the HB sleeve:

- selection of the kinematic scheme of the bushing, taking into account the given histogram of the angles of deflection of the blades and the requirements of operation (folding the blades in the parking lot, etc.);

- selection of the material of the bushing elements;

- selection of the type of hinges (rolling bearings, sliding, elastic elements);

- selection of the type of damper of the vertical hinge;

- constructive and technological development of bushing elements (determination of geometric dimensions and shape, surface hardening technology, etc.).

 

 

helicopter main rotor

 

  • 6. Manufacturing of experimental full-scale samples of HB elements.

  • 7. Tests for strength and life tests of NV elements on a full-scale stand, updating of technical documentation for the manufacture of IV elements.

  • 8. Flight research of the kinematic characteristics of the hub and blades of the HB.

  • 9. Serial production of HB blades and hubs.

 

GENERAL REQUIREMENTS FOR ELEMENTS helicopter rotor

 

HB helicopter of its attachments, including: blade bushing joints and bearings, damper lever pivot blade attachment sleeve helicopter rotor shaft of the main gearbox (GR), the shaft GR Carter GR (if it is included in the power circuit design) GR mount to the fuselage (the gear rack), wild boar or column NV and its attachment to the fuselage - must meet the following requirements.

The design of the blades should provide the specified characteristics of the aerodynamic contour and balance within that allow to operate the helicopter, taking into account speed limits, resources and service life.

 

Helicopter rotor 2

 

Helicopter rotor blade must be designed so as to prevent normal operation, preventing accumulation of water in any portion thereof.

The blades should be equipped with an alarm system damage spar. In the presence of signaling resource blades since its operation shall not be less than the maximum duration of the flight, set for this type of helicopter.

Durability trim blades HB should be checked for the joint action of bending loads on blades in the plane of the highest and lowest hardness, torsion, as well as the maximum local aerodynamic loads and internal pressure.

Torsional Rigidity blade about its longitudinal axis in combination with the stiffness of the control wiring must be sufficient for acceptable levels of loads from a flutter safety and loss of control.

Static strength of HB and its attachment must be checked to load the flight and ground load cases that are under consideration for the settlement of the structure. In addition, the static tightness HB checked for landing load cases of loading.

To reduce the risk to the strength calculation of load resonance phenomena must precede the determination of natural frequencies of the blade in the plane of rotation and stroke. It should take into account the boundary conditions for its consolidation in the operational speed range HB.

 

Helicopter rotor and everything about it

 

Static strength of the bearing sleeve HB must be sufficient to withstand the load falling on the bearings in the case of loading in maneuvering flight, and under the influence of turbulent air. Bearing life should be determined on the basis of tests for wear isolated articulations and (or) assemblies generally form at the stands or ground endurance test. To determine the bearing life is taken minimum result obtained by testing a minimum of three samples.

In drawing up the program of tests for wear permitted to take that length of horizontal flight at low speeds is 10% of the resource, flying at cruising speed

- 80% of the resource and flight at maximum speed - 10% of the resource.

Results of land or natural resource test bench can be used to assess the strength of the individual units of helicopters, if the level of current at this voltage is not less than the flight.

To determine the intensity, checking inventories to self-oscillation, vibration studies, determining the dynamic characteristics of the structure of the blade held bench tests under the given loads.

Furthermore bench are also other types of tests: to determine the strength characteristics of materials, the stress determination using different models of optical active material, endurance tests and trials in an actual operation. Tests are carried out in various ways: without turning the screws on special stands in the laboratory, with the rotation of the stands - special towers or screw devices on the basis of full-scale helicopter in wind tunnels.

 

Helicopter rotor 545

 

The HB blades must undergo fatigue testing in order to determine the durability of the structure under the influence of variable loads for the subsequent determination of the resource and for quality control of the serial production. Typically, a sample compartment and a lumpy section are tested. Tests are carried out on resonant stands. Loads are created using an inertial vibrator mounted on the blade compartment. In addition to the variable lateral loads, an application of static loading from the centrifugal force is provided. Often, the rate of growth of fatigue cracks is also recorded, which makes it possible to reasonably establish the periodicity of structural inspections in operation, and to increase the survivability of the structure.

A feature of fatigue testing is the need to repeat them many similar objects, due to random variations in the characteristics of a significant durability.

The tests on flutter screws are manufactured on models in wind tunnels, necessarily on full-scale helicopter to the ground conditions at the promotion of HB.

Measurements of loads on the blade in flight could be properly placed and held only on the basis of preliminary calculations and bench tests.

The value of full-scale flight tests is that all phenomena occur without distortion associated with the violation of similarity, with the schematization of the design, the methods of applying the load, etc. It is possible to create helicopters-flying laboratories for the study of new structures that have not previously been studied. The disadvantage is the increased risk of testing in some cases. During flight tests, the stresses in the side member of the HB blade, in its skin, the torsional moments and hinge moments of the blades, the forces in the control systems, the moments and forces in the shafts HB and RV, the stresses or bending moments in the blades of the RV, the details of the bushings are measured.

 

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