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. Selection of basic parameters HB: the diameter D of the number of blades z; and filling; circumferential speed of rotation with a D.
2. Aerodynamic design of the blade (the appearance of the blades): choice of shapes in the plan; shaped profile cross-sections, cross sections with the relative thickness and distribution of the twist along the radius of the blade f.
3. Determination of the limiting blade deflection angles f, (3, £, in the management of the helicopter at all design modes of the flight.
4. Construction of the blades:
- Choice of material and the frame spar, spar forms based on previous experience and existing design and technological and operational constraints; forming section of the spar chord and the radius of the blades on the basis of static strength calculation of the PA;
Helicopter rotor pictures
- Adjustment of mass stiffness characteristics of the blades for the purpose of detuning from resonance at the operating speed NV and ensure sufficient reserves of aeroelastic stability (calculated kinds of flutter, divergence, "terrestrial" response).
- 5. Construction of the hub HB:
- The choice of the kinematic scheme sleeve with specified histogram deviation angles of the blades and operation requirements (folding blades in the parking lot, etc.);
- Choice of material elements of the sleeve;
- Select the type of joints (rolling bearings, sliding elastic elements);
- Select the type of damper vertical hinge;
- Design and technological development of the sleeve elements (determination of dimensions and shape, surface hardening technology, etc.).
6. Production of full-scale models of experimental elements HB.
7. Tests of strength and endurance tests on full-scale elements HB stand, adjusting the technical documentation for manufacturing of elements IV.
8. Flight Research kinematic characteristics of the blades and the hub HB.
9. Serial production of the blades and the hub HB.
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 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 the 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.
HB Blades necessarily undergo fatigue tests to determine the durability of the structure under the influence of variable loads for the subsequent establishment of the resource and to control the quality of serial production. As a rule, tested a sample compartment and the butt portion. Tests are performed on resonance stands. Pressures created using the inertial vibrator compartment mounted on blades. Further variables transverse loads, and provides static podgruzki application of centrifugal force. Often recorded as the growth rate of fatigue cracks that can reasonably establish the frequency of inspections of construction operation, improve the survivability of the design.
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 natural flight tests that all phenomena occur without distortion associated with the violation of the similarity with the schematization design methods of load application, etc.. You can create a helicopter - flying laboratory for testing new designs not previously studied phenomena. The downside is increased in some cases the risk of testing. During the flight tests measure the voltage of the blade spar NV, in its casing, the torque and pivot points of the blades, power management systems, moments and forces in the trees HB and PB, tension or bending moments in the blades PB details sleeves.
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