Showing papers on "Blade pitch published in 1996"

Application of a Genetic Algorithm to Wind Turbine Design

Abstract: This paper presents an optimization procedure for stall-regulated horizontal-axis wind-turbines. A hybrid approach is used that combines the advantages of a genetic algorithm and an inverse design method. This method is used to determine the optimum blade pitch and blade chord and twist distributions that maximize the annual energy production. To illustrate the method, a family of 25 wind turbines was designed to examine the sensitivity of annual energy production to changes in the rotor blade length and peak rotor power. Trends are revealed that should aid in the design of new rotors for existing turbines. In the second application, a series of five wind turbines was designed to determine the benefits of specifically tailoring wind turbine blades for the average wind speed at a particular site. The results have important practical implications related to rotors designed for the Midwest versus those where the average wind speed may be greater.

Force and Flow Characteristics of a Partially Submerged Propeller

Abstract: Model experiments have been conducted to determine the average and dynamic performance of a high-speed partially submerged propeller. The purpose of the experiments was to examine the influence of shaft yaw and inclination angles on the propeller characteristics at different Froude and cavitation numbers and to study the flow around the propeller blades in different conditions. The loads on an individual blade were measured by a stiff five-component balance and a camera equipment recorded flow phenomena of interest. Test results showed on the one hand that a partially submerged propeller, given a proper shaft yaw angle, offers a possible solution for very high efficiency. On the other hand serious vibration and strength problems may arise from resonant blade vibrations. The results have been analysed to ascertain the hydrodynamic origin of various observed force and flow phenomena. Through this analysis, implications for performance prediction theory as well as practice have been pointed out. In addition, basic problems and involved approximations of measurement of dynamic blade load have been addressed. General criteria for the design of an unsteady force measuring system have been outlined, for the case when resonant blade vibration is present. Outlined have been also special similarity law requirements, necessary if the effect of blade vibration observed for a model is to apply to vibrations of larger propellers. Throughout this report, attempts have been made to provide sufficient material so that the experimental results really can be used to validate future theory or repeated experiments.

Hub for rotary wing aircraft

Abstract: A rotor hub for a rotary wing aircraft is described which allows the use of more than three blades on the rotor head while providing all of the required functional features. The rotor head is constructed using a central barrel (2) to which is attached a plurality of blade attachment points on its exterior surface. The pitch arm (14) actuating points (24) are located inside of the hub barrel (2) extending from the outer surface into the hub barrel (2) through arcuate slots (30) in the barrel (2). The hub is particularly adapted for use with tilt rotor rotary wing aircraft and provides a negative Delta 3 blade pitch input in response to wind gusts and abrupt pilot control inputs.

HHC Aeroacoustic Rotor Tests in the German-Dutch Wind Tunnel: Improving Physical Understanding and Prediction Codes

Abstract: Within an international research program jointly conducted by US Army's Aeroflightdynamics Directorate (AFDD), NASA Langley, DNW, ONERA and DLR, the effects of a higher harmonic blade pitch angle on the rotor noise and vibrations were internsively studied. The program, denoted with Higher Harmonic Control Aeroacoustic Rotor Tests (HART) comprised both theoretical and experimental activities,the latter ones being represented by a comprehensive wind tunnel test campaign. Besides aeroacoustic measurements it comprised flow visualization tests and flow field measurements which were applied along with optical methods to determine the blade deflections. The measurements were preceded by extensive simulations performed with the analytical models of the individual participating organizations. Within these simulating different models for the rotor downwash, the blade aerodynamics and the rotor dynamics were used, leading to a very comprehensive theoretical data base.

Wind turbine generator rotor blade

Abstract: The rotor blade has a fully enclosed surface (6) at the tip (2) of the rotor blade, through which the air can pass without any additional air resistance. The closed surface is pref. provided by a ring, formed by a tube section (5) attached to the tip of the rotor blade, with or without a gap(s) in its peripheral surface.Pref. the tube section is made of a conductive material, e.g. high quality steel, for additionally providing a lightning protection function, the dia., length and relative spacing of the ring surface from the blade rear edge selected to provide the optimum compromise between the noise reduction and the increase in air resistance.

Power limitation in variable speed wind turbines with fixed pitch angle

Abstract: Variable speed operation of wind turbines has the potential to increase energy capture, to reduce fatigue damage and to reduce aerodynamic noise level. However, one of the most important characteristics of variable speed wind turbines is operational flexibility, which allows the use of different control strategies for above and below rated wind speed. One control strategy which is possible to implement is power capture limitation without using pitch control. In this paper, a control system for power limitation driving the wind turbine to an aerodynamic area is proposed and experimental results obtained from an experimental rig which uses a high performance switched reluctance generator are discussed.

Higher harmonic Control Aeroacustic Rotor Test (HART) - Test Documentation and Representative Results

Abstract: In a major cooperative research program within existing US-German and US-French Memoranda of Understandings (MoU's) a very comprehensive experimental study was conducted with a 40-percent geometrically and dynamically scaled BO-105 main rotor operated in the open-jet anechoic test section of the German-Dutch-Wind Tunnel (DNW). The objectives of the program were to improve the physical understanding and the mathematical modelling of the effects of the higher harmonic blade pitch control technique on blade-vortex interaction (BVI) impulsive noise and vibration reduction. A unique set of acoustic, aerodynamic, dynamic response, performance, and rotor vortex wake data were acquired with a pressure and strain gauge instrumented blade and by application of non-intrusive measurement techniques. This report documents the experimental part of this research program, termed Higher-harmonic-control Aeroacustic Rotor Test (HART) which was jointly performed by researchers from.

Adaptive flight control surfaces, wings, rotors, and active aerodynamics

Abstract: This study outlines active flight control materials, structural arrangements, and several new active flight control methods for rotorcraft, airplanes and missiles. A system-level comparison shows that flight control actuator systems using materials like piezoceramics have approximately double the mass-specific energy and 4 to 6 times the volume specific energy of conventional actuators. New fabrication techniques centered on the principal of directional attachment allow wings and rotor blades to become twist active. Using these new methods, directionally attached piezoelectric (DAP) actuator elements were built into graphite-epoxy sandwich structures. When compared to conventionally attached piezoelectric (CAP) elements, twist deflections (important for flight control) of DAP plates were an order of magnitude greater. By using such twist-active elements in a torque-plate configuration, an active helicopter rotor was built. This Froude-scaled solid state rotor was whirl-stand tested and showed steady blade pitch deflections in excess of plus or minus 8 degrees with good correlation between theory and experiment rates up to 42 Hz (which corresponded to 2.5/rev) and no degradation in deflection as RPM was increased. DAP elements were also used in high aspect ratio subsonic and supersonic wings, demonstrating static twist deflections of plus or minus 2 degrees and plus or minus 6 degrees respectively, with good correlation between experiment and finite element results. The final section compares all-moving active stabilator structural arrangements and pitch deflections, which range up to plus or minus 12 degrees, generating lift coefficient changes in excess of plus or minus 0.8.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Marine propulsion device

Abstract: A marine propulsion device improves the handling characteristics and the responsiveness of the watercraft on which it is used. The propulsion device includes a pair of counter-rotating propellers. At least the blades of the front propeller each have a mean camber line in cross-section which has a generally constant radius of curvature. This blade shape reduces cavitations and permits the rear propeller to be mounted closer to the front propeller, and consequently closer to the steering axis of the outboard drive. As a result, steering torque is reduced. The blades of the rear propeller also are not more than thirty percent smaller than the blades of the front propeller, and the average pitches of the propellers do not differ by more than one to four percent. These blade configurations of the front and rear propellers improve the stability of the watercraft when turning, thereby reducing chine walk, as well as improve the responsiveness of the watercraft.

The Influence of Detailed Blade Design on the Aerodynamic Performance of Straight-Bladed Vertical Axis Wind Turbines

Abstract: The recent development of an unsteady, three-dimensional aerodynamic model has provided the opportunity to determine the influence of detailed blade geometry on the performance of straight-bladed vertical axis wind turbines In particular, the present paper examines the effect of blade pitch, twist, taper and aerofoil section by comparison with a simplistic baseline configuration The study concentrates on the low tip-speed ratio regime where the blade aerodynamics are inherently unsteady and the most severe loadings are experienced In general, the effects of pitch and twist are similar, with both presenting only limited scope for enhanced design Moderate taper is shown to improve the overall aerodynamic performance while having the structural benefit of reducing the bending moment at the cross-arm The potential of a blade with varying cross-section to produce passive stall regulation is also demonstrated Finally, the influence of unsteady blade stall is considered in more detail for each of the confi

System and method for providing cyclic and collective pitch control in a rotary wing aircraft

Abstract: A cyclic and collective control system is provided for controlling rotor pitch in a rotary wing aircraft. The rotor blades are pivotally mounted on a hollow, spinning shaft. An angularly and vertically displaceable control shaft is mounted with the spinning shaft and carries a rotatable control hub at its end. The control hub is coupled through pitch link rods to the rotor blades. When the control shaft is displaced vertically within the spinning shaft, the rotor blade pitch is changed collectively. When the control shaft is displaced angularly relative to the spinning shaft, the rotational plane of the control hub becomes skewed relative to the rotor axis. This has the effect of changing the pitch of the rotor blades in accordance with their rotational position around the rotor axis and has the further effect of providing cyclic control.

Analysis of helicopter blade vortex structure by laser velocimetry

Abstract: In descent flight, helicopter external noise is mainly generated by the Blade Vortex Interaction (BVI). To under-stand the dynamics of this phenomenon, the vortex must be characterized before its interaction with the blade, which means that its viscous core radius, its strength and its distance to the blade have to be determined by non-intrusive measurement techniques. As part of the HART program (Higher Harmonic Control Aeroacoustic Rotor Test, jointly conducted by US Army, NASA, DLR, DNW and ONERA), a series of tests have been made in the German Dutch Wind Tunnel (DNW) on a helicopter rotor with 2 m long blades, rotating at 1040 rpm; several flight configurations, with an advance ratio of 0.15 and a shaft angle of 5.3°, have been studied with different higher harmonic blade pitch angles superposed on the conventional one (corresponding to the baseline case). The flow on the retreating side has been analyzed with an especially designed 3D laser velocimeter, and, simultaneously, the blade tip attitude has been determined in order to get the blade-vortex miss distance, which is a crucial parameter in the noise reduction.

Connection device for the deicer of a helicopter rotor

Abstract: The cable connections feed the drive for the helicopter rotor blades, to change their slant position. The cable connections (18) come up vertically through the rotor blade hub (17). The rotor blade is attached to a holder section (5) which in turn is attached to the helicopter hub. The cable is connected across the interface to the rotor blade hub by an elongated U-shaped section (32) which flexes with helicopter blade movement. The U-shaped section is flattened accommodating all conductors along a single line of conductors.

Propeller propulsion unit for aircrafts in general

Abstract: A propeller propulsion unit for aircrafts in general including a rotation shaft driven by a motor, the unit including a single-blade propeller and a counterweight that are connected to the shaft, the counterweight being arranged in a substantially diametrical position with respect to the single blade in order to balance the moment generated by centrifugal force and being variably offset with respect to the axis of the blade in order to balance the moment generated by the traction force of the single-blade propeller.

Propeller for marine propulsion drive

Abstract: A blade design for a counter-rotating propeller system improves the performance of the outboard drive on which is it employed when the propellers are run partially exposed. The propeller system includes a pair of counter-rotating propellers that rotate in opposite directions about a common axis. The rear propeller has a smaller diameter--about 92% of the front propeller--and a total blade face surface area of about 85% of the total blade face surface area of the front propeller. The blades of the front and rear propellers desirably have the same camber and generally the same pitch. The rear propeller pitch is between 90% and 110% of the front propeller pitch. These blade parameters improve the efficiency of the rear propeller over prior designs when the propellers run partially exposed in order to maximize the thrust produced by the propulsion system.

Ship propulsion system with two contra=rotating propellers

Abstract: The propulsion system has at least one IC engine (14) driving the first propeller (2) and at least one electric motor (24) driving the second propeller (4). The electric motors are supplied by one or more generators (16,16'). One propeller, i.e. the first, is variable pitch and the other is fixed pitch.The first propeller is arranged behind the second propeller, looking in the direction of travel of the ship. The two propellers are mounted on two mutually coaxial shafts. The sum of the powers of the one or more IC engines and the one or more electric motors correspond to the maximum required propulsive power of the ship.

Propeller-driven educational vehicle apparatus

Abstract: A propeller-driven educational vehicle for teaching science, mathematics, technology, and research methodology. The educational vehicle includes a body, one pair of wheels at the front end of the body and a second pair of wheels at the front end of the body, and a number of interchangeable propellers of different sizes for attachment by means of a propeller shaft to the front end of the body. A rubber band connects the rear end of the body to the propeller shaft. Rotation of the propeller and the propeller shaft in one direction winds and tightens the rubber band, thus storing in the rubber band potential energy which is transformed into kinetic energy and causes the propeller and propeller shaft to rotate in the opposite direction as the rubber band unwinds and loosens, causing the vehicle to move at an acceleration and speed which are directly related to the size of the propeller, and illustrating the conversion of potential energy into kinetic energy.

Hot wire measurements during rotating stall in a variable pitch axial flow fan

Abstract: This work deals with a series of experiments on the influence of the blade pitch on the rotating stall phenomenon in an industrial variable pitch, low-speed axial flow fan with low hub-to-tip ratio.Two simple hot wires were used to detect the rotating stall. One in the absolute frame and the other in the relative frame rotating with the rotor. The rotating stall features were determined, ranging from the non-existence in the whole flow range with the lowest pitch tested to one and two flow cells with the greatest pitch.Then, a triple hot wire, calibrated by a direct method, was used to measure the absolute flow field upstream and downstream from the rotor, before and during rotating stall for five distinct blade pitches. These measurements allow us to characterize different rotating stall structures.To understand the phenomena better, some tests were carried out in the relative frame, with the probe rotating with the rotor. An intermediate blade pitch with a single rotating cell was selected and measurements were taken at three radial positions. Velocity maps for all these measurements are presented.Copyright © 1996 by ASME

Ship drive with a driving engine and a directly driven propeller shaft

Abstract: A ship propulsion system in which the ship's propeller is connected with its propeller shaft directly to a drive mechanism. A thrust bearing in the drive mechanism receives directly the thrust of the propeller shaft. An auxiliary drive with an electrical machine is operable selectively as a motor or as a generator, and a coupling is provided between the electrical machine and transmission linkage in the auxiliary drive. A gear on the transmission surrounds the propeller shaft, and a flexible coupling connects the transmission to the propeller shaft. Mounted on a separate section of the propeller shaft between the transmission and the drive mechanism, is a shiftable coupling which is free of play and transmits torque from the drive mechanism to the propeller shaft as well as the thrust of the propeller shaft. An auxiliary thrust bearing is connected to the shiftable coupling and is actuated when the ship is in auxiliary or emergency operation during which the propeller shaft has a reduced thrust.

Multiblade rotary body

Abstract: PURPOSE: To reduce a periodical noise by making the array pattern of the blade pitch angles in a periodical pseudo-random series in which the autocorrelation function is made in about a delta function at every rotating cycle CONSTITUTION: The M series to be a pseudo-random series is a sequence of two values 0 and 1 having a cycle 2 -1, the number of the sequence in one cycle is an odd number, and the difference of the number of 0 and the number of 1 is made 1 And the 0 and 1 are made correspondent to 1 and -1, and, considering the time function held at t0 , the autocorrelation function is made close to the repetition of a delter function In this case, the design is made to make the pitch angle small in the time of 0, and the pitch angle large in the time of 1, and the respective angles are made θ1 and θ2 , and θ2 =(1+Δ)θ1 is set And the angles θ1 and θ2 are found, and then, in case of the angle is 7, for example, the angles θ1 and θ2 are aligned in order according to 0, 1, 0, 1, 1, 0, 1, and the blade pitches are to be set

Miss distance for rotor blade-vortex interaction noise reduction

Abstract: Blade-vortex interaction noise generated by helicopter main rotor blades is one of the most important noise mechanisms both in military aspects and community acceptance. Noise generating mechanisms and controlling concepts are studied, particularly in terms of a blade-vortex miss distance. A comprehensive code (CAMRAD-JA) coupled with a finite difference code(FPR) has been used to assess airloads and blade aeroelastic deformations. The results are compared with existing BO-105 test results. Potential methods to control the blade-vortex miss distance are studied by exploiting the blade flapping and torsional characteristics through active blade control technology. Introduction Rotor blade-vortex interaction(BVI) noise is generated from unsteady pressure fluctuations on the blade's leading edge due to interactions with previously generated tip vortices during descent or maneuvering flight conditions. This BVI noise is loud and impulsive in nature and it plays an important role both in military aspects and community annoyance. This paper is work of the US Government and is not subject to copyright protection in the United States. * Associate Fellow Understanding of the noise generating mechanisms has advanced substantially in recent years, but the progress of controlling this noise has been limited. Major controlling parameters for rotor BVI noise have been analytically investigated (ref.l) and several parameters were identified, such as tip vortex strength, blade-vortex miss distance, and blade pitch. Among many efforts to control these parameters, active blade control concepts have recently achieved some success in reducing BVI noise. In particular, the higher harmonic blade pitch control (HHC) and individual blade control (IBC) concepts have been tested and significant mid-frequency noise reductions of 5-6 dB have been reported (refs. 2-10). Meanwhile, several analyses (refs. 2,4,6, and 11) reported that the HHC concept with a proper blade pitch control schedule changes blade-vortex miss distances, vortex geometry, and blade circulation. Results also indicated that pitch control would not only modify the pitch, but would also modify the strengths of the shed vortices as well as possibly the interaction locations. Decreased blade loading in specific azimuthal regions has been identified to reduce BVI noise (ref.5); in addition, blade-vortex miss distances are definitely affected by HHC, and they evidently represent a dominant factor in the BVI noise reductions (refs.4 and 6). A vibration suppression mechanism by HHC was also analytically investigated through the flapping moment at the blade root (ref.6). Results showed that a vibration suppression can be achieved by reducing the blade flapping motion, thus decreasing the blade-vortex miss distance and, in turn, increasing the BVI noise. An international cooperative program, called Higher-Harmonic Control Aeroacoustics Rotor Test(HART), was carried out with a 40%-geometricalIy and dynamically scaled model of a BO-105 main rotor in the DNW in order to investigate the effects of HHC inputs on BVI noise reduction(refs.!2-18). This program concluded that a blade-vortex miss distance is strongly influenced by both a tip vortex trajectory and blade aeroelastic characteristics. In this paper, results of a study of the effect of a blade-vortex miss distance on rotor BVI noise reduction are presented. Potential concepts using active blade control technology to control the miss distance are also discussed. For this study, the in-house CAMRAD-JA/FPR codes (ref. 19) were used; the results are compared with the existing HART test data (ref.18). Blade Deformation and Airload From a blade-vortex interaction geometry and acoustic radiation, it has been known that the major contribution to acoustic radiation comes from near-parallel interactions between a blade and a vortex, which happen in both the advancing and the retreating sides. For example, a fourbladed model rotor of BO-105 shows that the major contribution of noise comes from the interaction of a blade at the azimuthal angle(y) of 50° with a vortex generated at y of 130° in the advancing side. In the retreating side, it comes from the interaction at 310° of the blade position with the vortex generated at y of approximately 230° (refs.14 and 15). Blade tip deflection, blade-vortex miss distance, airload, and vortex circulation will be discussed at these two azimuthal angles of 50° and 130° for the following three flight conditions: baseline case(run 140, without HHC), low noise case (run 138, with HHC inputs of 0.8° amplitude and 300° phase angle) and low vibration case (run 133, with HHC inputs of 0.8° amplitude and 180° phase angle) from the HART test (ref.18). Other common parameters are: advance ratio=0.15, tip Mach number =0.64, shaft angle=5.3° and thrust coefficient(Cr) = 0.0044. Blade tip deflection: Blade tip deflections along azimuthal angles play an important role in determining blade-vortex miss distances during interactions. In particular, blade positions at the time of both vortex generation and blade-vortex interaction are important to determine the miss distance. Figure 1 shows a blade tip deflection history over azimuthal angles from the HART test, along with results from the AFDD in-house analysis for rigid and soft blades. In this figure, measured blade tip deflec-tions show I/rev characteristics for the baseline case and 3/rev characteristics for cases with HHC 3P inputs(run 138 and 133). In the analytical results, the tip deflection history for a rigid blade shows substantially different characteristics compared to the experimental data. However, the results with a CAMRAD-JA elastic blade model show characteristics similar to those with the measured one in mode shapes, but not in amplitudes. This result has a serious implication in determining a miss distance. The measured blade tip positions at v=130° and \|/ = 50° show an interesting phenomenon. For the low noise case(run 138), the blade tip position is 3.5 cm at \y=130°, the point at which the vortex is generated, and the blade tip position is 9 cm at y=50°, the point at which the blade interacts with the vortex. The relative separation distance of blade tip positions at the two azimuthal angles is about 5.5 cm, which is much larger compared to 1.5 cm for the baseline case. This large separation distance of the blade tip positions directly contributes to the large bladevortex miss distance. For the low vibration case (run 133), the relative separation distance of blade tip positions at v = 130° and 50° is much smaller compared to those of the baseline case. The relative separation distance can also be obtained through the blade flapping deformations at y = 50° and Y = 130° as shown in figure 2. These figures suggest that blade tip deflections and flapping deformations can be controlled by adjusting HHC inputs.

Integrated actuation system for individual control of helicopter rotor blades

Abstract: Integrated actuation system for individual control ofhelicopter rotor bladesDariusz Bushko, Ralph Fenn, Mike Gerver, John Berry, Frank PhilipsSatCon Technology CorporationCambridge, Massachusetts 02142Donald J. MerkleyU.S. Aiiny AATDFort Eustis, VirginiaABSTRACTThe unique configuration ofthe rotorcraft generates problems unknown to fixed wing aircraft. These problems includehigh vibration and noise levels. This paper presents the development and test results of a Terfenol-D based actuator designedto operate in an individual blade control system in order to reduce vibration and noise and increase performance on ArmyUH-60A helicopter. The full -scale, magnetostrictive, Terfenol-D based actuator was tested on a specially designed testbedthat simulated operational conditions of a helicopter blade in the laboratory. Tests of actuator performance (stroke, forcemoment, bandwidth, fatigue life under operational loading) were performed.Keywords: smart structures, magnetostrictive actuators, vibration control, helicopters, actuators1. ROTORCRAVF VIBRATION ATTENUATIONHelicopters have unique problems resulting from the continuously changing aerodynamic conditions as blade is travelingthrough various angles around its axis of rotation. Depending on the particular helicopter's mode of operation (hover, forwardflight, etc.) the rotor blade is subjected to the combination of typically highly turbulent air streams induced by motion of theentire helicopter and its rotor blades. At given moment each section of the blade in span direction may actually be exposed todramatically different aerodynamic conditions. Consequently, vibration, noise and considerable degradation of rotorcraftperformance are observed. In fact, aerodynamic interactions taking place in the vicinity of the helicopter rotor are typically aprinciple source of helicopter noise. Vibration induced problems include pilot and passenger fatigue, increased maintenance,payload damage, additional structural weight to carry fatigue loading, and undesired noise signature. Vibration reductionsystem ofthe helicopter rotor blade is the goal ofthe presented work.The primaiy objective here is to design a practical vibration reduction system for the Army UH-60A helicopter. Since thepresented technology is well scaleable towards larger systems the choice ofthis particular aircraft is specially suitable due to itssizable blade profile and relatively low revolution rate of the rotor. The adopted approach is to attack the problem at its roots,namely, rotor blades. The idea is to control aerodynamic response ofthe rotor by inducing a pre-defined pitch angle variation ofvarious sections of the rotor blades in order to dampen momentary blade vibrations. Obviously this additional control functionfor the blade pitch angle tuust be virtually negligible to primary flight control functions (cyclic and collective pitch anglecontrols).

Active Control of Helicopter Blade Stall

Abstract: In an effort to expand the helicopter flight envelope, this analytical study proposes the concept of using high frequency blade pitch actuation to alleviate blade stall at high speed and/or high thrust flight conditions. The availability of high-frequency blade-mounted actuators has made this concept realizable. This study is carried out using the University of Maryland Advanced Rotorcraft Code (or UMARC), which employs state-of-the-art structural and aerodynamic modelings. The salient features of this code include the application of the finite element methods in both space and time domains, and the incorporation of an advanced unsteady aerodynamic and nonuniform inflow models. Preliminary results indicate that two-per-rev blade pitch control can reduce retreating blade stall for a rotor operating at high speed and high thrust flight condition. Current efforts concentrate on developing an automatic stall suppression system which employs a combination of higher harmonic blade pitch schedule.

Propeller for use on ship or aeroplane

Abstract: The propeller may be used on a ship or an aeroplane, but preferably a manned aeroplane. There are one or more blades (44) that have an adjustable device to adjust the climb angle of the blades during its operation. A folding device (32,42) is shown, with the blades in a rotational axis (29) with the propeller (18) in a parallel orientation. The blades on the folding axis may be orientation a free hinge on the hub (20) of the propeller. The folding axis may be travelling in a direction approximately tangential to the rotational axis of the propeller.

Helicopter rotor blade structure

Abstract: The main rotor blades protrude horizontally sideways from the hull of the helicopter. The additional blade (2) is parallel to the main one (7), on which it hinges (8) downwards from a flush-fitting position into an extended one clear of it. The hinge can consists of streamlined bars at intervals in the lengthwise direction of the blades, and hinging at opposite ends on the latter. Where it bears against their rotor head, the main blade can have an additional vibration damper filled with fluid. A piston in the cylinder has links to the main blade, to adjust the blade pitch.

Blade pitch control for main rotor of helicopter

Abstract: The hydraulic actuating mechanism is used to set the pitch of the blades (8) of the main rotor of a helicopter. The hydraulic circuit includes a bypass valve (20) in addition to the first valve (34) in the hydraulic line (38A,B) between the working chambers (16,18) of the piston and cylinder assembly (2) connected (6) to a rotor blade. There is a servo control valve (10) connected to the cyclic pitch control lever (14). The system also includes a hydraulic pressure source which varies according to the rotational speed of the main rotor.

System and method for adjusting a variable-step propeller with feedback

Abstract: The invention relates to aviation engineering. The technical result of using it is increased accuracy in the measurement of current blade angles and improved operational reliability of the system, achieved by the incorporation of means of guarding against uncontrollable shifts of the propeller to large blade angles, said means using a current blade position signal. To that end, the system of adjusting a variable-step propeller (1) with feedback in the form of a beta tube (6) and a sensor (7) which detects the angular position of the blades (2) and co-operates with the beta tube comprises an electronic control unit (32), an electro-hydraulic converter (33), a hydromechanical maximum frequency limiter (34), and propeller control channels with a regulator element in the form of, for example, slide valves. A particular feature of the system is the mechanical connection in the axial direction of the housing (16) of the sensor (7) with the housing (1) of the propeller or shaft of the propeller drive through the assembly of the bearing (25), and the fact that the control channels are in addition provided with a slide valve (40) actuated by an electromagnetic valve (41) for effecting transition from control by the electronic unit to control by the hydromechanical maximum rotation frequency limiter. The electromagnet (41) is electrically connected to the sensor for detecting the angular position of the blades via the electronic control unit.