Showing papers on "Blade pitch published in 1992"

Electromechanical apparatus for varying blade of variable-pitch fan blades

Abstract: Blade pitch of variable pitch blades is changed by an actuator having first and second ac machines. The first ac machine is excited with ac power to apply a motoring torque to a control shaft of the actuator, thereby causing blade pitch to change in one direction. The second ac machine is excited with appropriate power to apply a braking torque to the control shaft, thereby causing blade pitch to change in an opposite direction. When the second ac machine is an induction machine, dc excitation will brake the control shaft. When the second ac machine is a synchronous machine, an ac excitation causing a retarding magnetic field will brake the control shaft.

Blade pitch change control system

Abstract: A pitch change actuation system is disclosed for adjusting the pitch of a variable pitch propeller blade (120) operatively connected for pitch change to a pitch change actuator piston (140). A pitch change control system (10) is operatively connected to the pitch change actuator piston (140) for selectively pressuring the pitch change actuator piston to effectuate a desired change in the pitch of the propeller blades (120). The pitch change control system (10) comprises a primary electrohydraulic valve (30), a protection valve (60), an electronic controller (20) and a protection solenoid (50). During normal operation, the primary electrohydraulic valve (30) is modulated under control of the electronic controller (20) to effect pitch change. In the event of failure of the electronic controller (20), the protection solenoid (50) is operative to activate the protection valve (60) to assume pitch change authority over the primary electrohydraulic valve (30) thereby providing emergency feathering capability, overspeed protection, low pitch stop limit protection, and in place pitchlock despite failure of the electronic controller.

Paddle wheel rotorcraft

Abstract: An aircraft having vertical takeoff and landing capability having at least first and second laterally extending paddle wheels rotatable on a central axis generally perpendicular to the longitudinal axis of the aircraft and between its nose and tail. Each of the paddle wheels has a plurality of blades pivoted by a system of linear actuators to a determined optimum blade pitch angle. One paddle wheel is positioned adjacent the port side of the aircraft and the other paddle wheel is positioned adjacent the starboard side. The pilot is able to operate the aircraft in all regimes of flight by differentially adjusting the pivot angle of each of the blades. In one embodiment utilizing only a pair of paddle wheels, differential operation of the blades provides lift, thrust, roll, and yaw control of the aircraft, while an aircraft pitch control rotor rotatable about a vertical axis distant from the paddle wheels is provided for controlling pitch of the aircraft. In another embodiment of the invention, the aircraft is provided with both forward and aft pairs of paddle wheels such that differential operation of the blades of the forward and aft paddle wheels provides pitch control of the aircraft without need of a separate pitch control rotor, while also providing lift, thrust, roll, and yaw control.

Helicopter servoflap actuator having mechanical stop and oil pump

Abstract: In a servoflap system for helicopters, angular positions of the helicopter's servoflaps are controlled by actuators located near the tips of the helicopter blades Each actuator contains a pump for circulating a lubricant onto the actuator's gears when blade pitch is being changed The pump is built into the actuator's mechanical stops

Analysis of the effects of blade pitch on the radar return signal from rotating aircraft blades

Abstract: The analysis considers only propeller blades. This is partly because rotor blades will also have cyclic pitch, in order to reduce the roll caused by the asymmetry of lift between advancing and retreating blades, and partly because rotor blades are so large and their pitch is so small that the effect of any AM on the return signal will be small in comparison. Simulated returns and frequency spectra are plotted and discussed.

Effects of higher harmonic control on rotor performance and control loads

Abstract: An analytical study, based on an advanced Higher Harmonic Control (HHC) analysis for helicopter rotor systems, is carried out to investigate HHC application for rotor performance enhancement. The effects of HHC on stall characteristics of rotor and blade pitch-link loads when the system is configured to suppress vibration are also examined. For vibration control, simulated results indicate that HHC may promote early blade stall. Effects of blade torsion frequencies on HHC performance are moderate, and torsionally stiff blades require less actuator power than torsionally soft blades. For rotor performance improvement, a 3 to 5 percent reduction in rotor shaft power can be achieved with 2 deg of two-per-rev blade pitch control.

Method for folding helicopter main rotor blades

Abstract: A method of folding the main rotor blades (21, 23, 25, 27) of a helicopter (11) for storage in which blade supports (31, 33) are removeably attached to the nose (13) and tail (15) of the fuselage of the helicopter (11).

Propeller blade tip path plane inclining device

Abstract: A propeller blade tip path plane-inclining device which is provided with a fuselage, a propeller including a center piece rotating unitary with a rotation shaft in association therewith and a plurality of blades extending substantially horizontally from the center piece and differing the variation in pitch during the rotation thereof from one another, a motor for driving the propeller for rotation, a position detector for detecting the position of the propeller in the propeller rotation plane, and a control device for controlling the motor in accordance with an output signal of the position detector.

Classical control of active pitch regulation of constant speed horizontal axis wind turbines

Abstract: Owing to current concern over the environment, there is much interest in renewable sources of electrical power generation of which one of the most promising is wind power. However, it is not yet a mature technology and many basic issues have yet to be resolved. One such issue is the best means of regulating the wind turbines. Many horizontal axis grid-connected wind turbines have the capability to vary the angle of pitch of the blades which can be exploited to provide regulation. The purpose of this paper is to report on an extensive investigation into the control of active pitch regulation of constant speed, grid-connected horizontal axis wind turbines. The performance attainable by PI control design and classical Nyquist-Bode loop shaping is determined and compared

Pitch stop assembly for variable pitch propulsor

Abstract: A pitch change system (30) for varying the pitch of the blades (16) of a multibladed propulsor (10) comprises a pitch change actuation assembly (40) and a pitch change drive assembly (70) for selectively actuating the pitch change actuation assembly (40) whenever it is desired to change blade pitch. The pitch change actuation assembly (40) comprises a ballscrew (42), a ballscrew nut (44) threadably mounted to the ballscrew (42), and a pitch stop assembly (100) having a retractable feather stop (135) which in its normal position prevents the ballscrew (42) from driving the ballscrew nut (44) to move the blades (16) beyond the coarse pitch setting corresponding to blade feather, but in its retracted position permits the ballscrew (42) to drive the ballscrew nut (44) to move the blades (16) through feather to a desired reverse pitch setting.

Ducted fan and pitch controls for tail rotor of rotary wing aircraft

Abstract: A tail rotor (8) for a rotary wing aircraft is located in a laterally directed duct (9) located at the end of a tail cone (7) extending rearward from the aircraft cabin and at the base of an empennage (5) extending upward from the duct. The rotor includes a rotor shaft (50) driveably connected to a power source, a rotor hub (10) connected to the rotor shaft (50), a rotating control shaft (64), a stationary control shaft (124), and an actuator (132) connected to the stationary control shaft (124) for moving the rotating control shaft (64) axially. The rotor hub (10) includes rotor arms (12) each supporting a pitch shaft-blade spar (18, 16) assembly for pivotable movement about a pitch axis. A pitch beam (96) supports flexures (94), each connected to a pitch arm (80) offset laterally from the associated pitch axis. The flexures (94) driveably connect the pitch arms (80) to the pitch beam (96) and transmit pitch control motion to the blades (14) as the pitch beam (96) moves along the rotor axis. Pitch bearings (20, 22), on which the pitch shafts (18) turn about the pitch axes, are supported on a rotor hub shell (46) fixed to the rotor hub (10).

Fault-tolerant apparatus for controlling blade pitch

Abstract: Fault-tolerant apparatus for controlling first and second input members of a mechanical actuator includes first and second electrical machines and at least two controllers. The first and second electrical machines, which apply braking forces to the first and second input members, respectively, are provided with stators having pluralities of isolated phase windings. Each controller is coupled to a phase winding of the first electrical machine, and also to a phase winding of the second electrical machine. Any one controller can excite the first electrical machine to apply the braking force to the first input member or the second electrical machine to apply the braking force to the second input member.

Electric pitch control apparatus for variable-pitch propeller

Abstract: An electric pitch control apparatus for a variable-pitch propeller equipped with a pitch control mechanism having an electrically controlled actuator for controlling a pitch angle of the propeller blade in accordance with a control current applied thereto. The electric pitch control apparatus is designed to compensate a difference between target and actual pitch control amounts caused by a secular change of the pitch control mechanism thereby to effect an accurate control of the propeller pitch.

Wind tunnel performance results of swirl recovery vanes as tested with an advanced high speed propeller

Abstract: Tests of swirl recovery vanes designed for use in conjunction with advanced high speed propellers were carried out at the NASA Lewis Research Center. The eight bladed 62.23 cm vanes were tested with a 62.23 cm SR = 7A high speed propeller in the NASA Lewis 2.44 x 1.83 m Supersonic Wind Tunnel for a Mach number range of 0.60 to 0.80. At the design operating condition for cruise of Mach 0.80 at an advance ratio of 3.26, the vane contribution to the total efficiency approached 2 percent. At lower off-design Mach numbers, the vane efficiency is even higher, approaching 4.5 percent for the Mach 0.60 condition. Use of the swirl recovery vanes essentially shifts the peak of the high speed propeller efficiency to a higher operating speed. This allows a greater degree of freedom in the selection of rpm over a wider operating range. Another unique result of the swirl recovery vane configuration is their essentially constant torque split between the propeller and the swirl vanes over a wide range of operating conditions for the design vane angle.

An exploratory investigation of the flight dynamics effects of rotor rpm variations and rotor state feedback in hover

Abstract: This paper presents the results of an analytical study conducted to investigate airframe/engine interface dynamics, and the influence of rotor speed variations on the flight dynamics of the helicopter in hover, and to explore the potential benefits of using rotor states as additional feedback signals in the flight control system. The analytical investigation required the development of a parametric high-order helicopter hover model, which included heave/yaw body motion, the rotor speed degree of freedom, rotor blade motion in flapping and lead-lag, inflow dynamics, a drive train model with a flexible rotor shaft, and an engine/rpm governor. First, the model was used to gain insight into the engine/drive train/rotor system dynamics and to obtain an improved simple formula for easy estimation of the dominant first torsional mode, which is important in the dynamic integration of the engine and airframe system. Then, a linearized version of the model was used to investigate the effects of rotor speed variations and rotor state feedback on helicopter flight dynamics. Results show that, by including rotor speed variations, the effective vertical damping decreases significantly from that calculated with a constant speed assumption, thereby providing a better correlation with flight test data. Higher closed-loop bandwidths appear to be more readily achievable with rotor state feedback. The results also indicate that both aircraft and rotor flapping responses to gust disturbance are significantly attenuated when rotor state feedback is used.

Pitch change control system

Abstract: A pitch change actuation system is disclosed for adjusting the pitch of a variable pitch propeller blade (20) rotatably mounted to a hub (10) of the propeller. The pitch change actuator comprises a blade actuation piston (30) operatively connected to the propeller blade (20), a pitchlock piston (50) having a longitudinally directed annular shaft (56) extending therefrom about the shaft (34) of the blade actuation piston (30), pitchlock assembly (130, 140, 150) operatively interconnected between the pitchlock piston (50) and the blade actuation piston (30) for restraining inadvertent blade pitch reduction, bias spring (60) for exerting a preload force against the pitchlock piston (50), and fluid supply conduit (70) operatively interconnected in fluid communication between control valve (100) and the pitch change actuator.

Electric pitch control apparatus for variable pitch propeller capable of controlling the pitch angle based instantaneous operational conditions of the propeller

Abstract: An electric pitch control apparatus for a variable-pitch propeller capable of properly controlling the pitch angle of the propeller blade in accordance with instantaneous operational conditions of the propeller and of effecting adjustment of the pitch angle of the propeller blade without any delay of a time in response to operation of the engine output lever for promptly coinciding an actual rotational number of the prime engine with a target rotational number.

Self-actuated rotor system

Abstract: The present invention discloses a main rotor collective pitch control assly for rotary wing aircraft. The assembly uses segmented rotor blades. The collective pitch of each movable segment may be independently varied, or may be adjusted in unison with one or more other segments on the same or different rotor blades. Control inputs may be made manually by the pilot or may be made by a computer which interprets data pertaining to the vibrational level and velocity of each rotor span. The pilot may override the computer in the event of system failure or if otherwise desired.

Propeller speed control having control parameters based on system dynamic characteristics

Abstract: An aircraft propeller speed control defines values for propeller speed governing control law parameters, such as gains and dynamic compensations, based on known values of propeller and engine dynamic characteristics over the complete propeller operating envelope. Adjusting control law gains and dynamic compensations as functions of propeller and engine dynamic characteristics over the entire flight envelope provides for control of propeller speed to obtain optimum stability and consistent propulsion performance over the entire flight envelope.

Marine counter-rotating propeller

Abstract: PURPOSE:To increase gain of a counter-rotating propeller by aiming at a fact that the center of a turning flow, generated by rotation of a front propeller, is displaced from its center of rotation, and placing the center of rotation of a rear propeller, constituted of a pod propeller, in a center position of this turning flow. CONSTITUTION:Front/rear propellers 2, 3, rotated in an opposite direction to each other by drive shafts 1, 4 opposed to each other, are juxtaposed to form a counter rotating propeller, and the rear propeller 3 is constituted of a pod propeller suspended through a strut 6 from the upper part of a stern frame 5. A rotational center 3a of the rear propeller 3 is placed in almost the center position of a turning flow by the front propeller 2 displaced from its rotational center 2a. The front propeller 2 is driven by a main engine E, and the rear propeller 3 is driven to be electrically connected to a shaft generator G connected to the main engine E.

Variable-pitch multi-blade rotor, in particular for the rear anti-torque system of a rotating wing aircraft

Abstract: A variable-pitch multi-blade rotor for use as the anti-torque rear rotor of a rotating wing aircraft has a rotor with a central shaft rotated about a central axis, a hub constrained to rotate with the central shaft about the central axis, blades distributed around the central axis with each blade being connected to the central shaft by a twistable element, a pitch control disk for the blades which is constrained to rotate with the central shaft but free to slide axially relative to the central shaft, and a member for controlling the sliding of the pitch control disk along the central shaft. Each blade root is secured to a transverse thrust and pitch control lever forming a yoke having one end hinged to the hub and another end hinged to the pitch control disk.

Wind rotor apparatus

Abstract: A wind rotor is disclosed for turning electrical generators or other mechanical equipment. The wind rotor contains multiple curved blades which are in a single plane of rotation, and which are spaced closely together so as to maximize the efficiency of the captured wind. The open blades are designed to overlap one another to an extent that there are always at least two blades positioned to capture the wind regardless from which direction the wind is blowing. The curved blades allow the rotor to always rotate in the correct direction regardless of the direction of the wind without the use of moving vanes or housings to help direct the wind at certain portions of the wind rotor. If the rotor is made to turn in the incorrect direction, it will, as wind from any direction blows against it, slow down, stop momentarily, and then begin to rotate in the correct direction.

Device for automatically stabilizing the yaw motion of a helicopter

Abstract: In a helicopter having a tail rotor (11) with a plurality of rotor blades (23) extending radially from a hollow rotor shaft (17) which is mounted for rotation about a transverse rotor axis (19), and having a push-pull rod (31) extending through the hollow shaft (17) and operably connected to the blades (23) to manually vary the collective pitch of the blades (23), a device for automatically stabilizing the yaw motion of the helicopter includes a gyroscopic assembly having a gyro rotor (37) mounted to rotate with the tail rotor (11), to pivot about a substantially longitudinal pivot axis by and at the outboard end of the push-pull rod (31) and to automatically vary the collective pitch of the blades (23) in response to yaw motion.

Propeller or rotor blades - are designed to reduce eddies and air or water resistance and have toothed leading and trailing edges

Abstract: The low eddy loss blades may be used for propellers for water craft and aircraft, and for rotors for helicopters. Each blade has pointed teeth (A) along the edge on either side. The number, size, shape, width, and relative distance of the blades is dependent upon the size of the propeller, rotor, etc. The relative angular position of the blades is adjustable, and this increases the blade surface. USE/ADVANTAGE - Toothed leading and trailing edges on propeller blades are designed to reduce thrust force losses.

Flip block assembly for changing dozer blade pitch

Abstract: The invention is an in a dozer blade pitch adjustment assembly of the type having a blade pivot pin spaced from a reference line on a dozer blade assembly. The improvement comprises a flip block eccentrically mounted between lugs of the blade assembly for pivoting movement between a first position and a second position. Flipping the block to the first position or to the second position changes the spacing between the pivot pin and the reference line and the pitch of the blade is thereby changed. The block is retained in one position or the other by bolts extending through the lugs and into the block.

Marine propulsion unit with controlled cyclic and collective blade pitch

Abstract: An integral marine propulsion unit utilizes both collective and cyclic propeller blade pitch angle variations to generate a thrust vector in any of three degrees of motion for use with both the submersible and surface marine vessels. The present marine propulsion unit eliminates the need for extraneous drag generating control surfaces and rudders for motion control of a marine vessel by incorporating a flat plate mechanism which includes an Oldham coupler coupled to a pair of plates and a slotted plate coupled with one of the plates. The slotted plate and the one plate coupled to the slotted plate are relatively rotatable about a fixed axis. The flat plate mechanism permits relative angular displacement between the slotted plate and the one plate to collectively pivot all of the propeller blades and permits radial movement of the slotted plate along with propeller blades.

Compensation for kinematic foreshortening effect in pitch control system for rotary wing aircraft.

Abstract: A rotor for a rotary wing aircraft includes a rotor shaft (78) driveably connected to a power source, a rotor hub (10) connected to the rotor shaft, rotor arms (12) inclined with respect to a plane perpendicular to the rotor axis (A) and pitch shafts (16) supported on each rotor arm. The rotor arms (12) each support a pitch shaft (16) for pivotable movement about a pitch axis (B). A pitch beam (54) carries flexures (48), each connected to a pitch arm (42) at a location offset laterally from the associated pitch axis. The flexures (48) driveably connect the pitch arms (42) to the pitch beam (54) and transmit pitch control motion to the blades (14) as the pitch beam (54) moves along the rotor axis (A). Each flexure (48) is intentionally displaced by bending radially during installation in a direction that reduces forces among components of the flexure bearings developed during operation.

Aeromechanical stability of helicopters with composite rotor blades in forward flight

Abstract: The aeromechanical stability, including air resonance in hover, air resonance in forward flight, and ground resonance, of a helicopter with elastically tailored composite rotor blades is investigated. Five soft-inplane hingeless rotor configurations, featuring elastic pitch-lag, pitch-flap and extension-torsion couplings, are analyzed. Elastic couplings introduced through tailored composite blade spars can have a powerful effect on both air and ground resonance behavior. Elastic pitch-flap couplings (positive and negative) strongly affect body, rotor and dynamic inflow modes. Air resonance stability is diminished by elastic pitch-flap couplings in hover and forward flight. Negative pitch-lag elastic coupling has a stabilizing effect on the regressive lag mode in hover and forward flight. The negative pitch-lag coupling has a detrimental effect on ground resonance stability. Extension-torsion elastic coupling (blade pitch decreases due to tension) decreases regressive lag mode stability in both airborne and ground contact conditions. Increasing thrust levels has a beneficial influence on ground resonance stability for rotors with pitch-flap and extension-torsion coupling and is only marginally effective in improving stability of rotors with pitch-lag coupling.

On a finite-state inflow application to flap-lag-torsion damping in hover

Abstract: An aerodynamic model with a coupled set of generalized dynamic wake equations and hybrid equations of motion for an elastic blade are applied here to a two-blade untwisted stiff in-plane hingeless small-scale model rotor with torsionally soft blades. Blade root offset, precone, blade droop, pitch control stiffness, and blade pitch angle are included in the model rotor. Numerical results show that 3D tip relief effects within the nonuniform steady-state inflow are significant to predict steady-state aerodynamic loads and blade deflections. Eigenvalue results confirm the importance of unsteady 3D aerodynamics in predicting lead-lag damping and frequency. Eigenvector analysis correlations reinforced qualitative and quantitative shortcomings associated with quasi-steady 2D aerodynamic theory for aeroelastic applications in hover.

Location for propeller blade made of fibre cpd. - has loop rail with bearing shaft extending through propeller blade root with loop rail extending around bearing shaft

Abstract: The bearing shaft (2) is formed at approximately 90 deg. to the longitudinal axis of the propeller blade and the loop rail (12) is of one-piece construction. The loop rail is arranged at approximately 90 deg. to the profile longitudinal axis parallel to the bearing shaft (2) on the propeller blade rail (1). The propeller blade root (13) is rectangular and to accommodate the bearing shaft has a bearing bush (8). On the outside (14) of the propeller blade root damping elements are arranged (5). The accommodation aperture (15) of the propeller blade casing (4) for the propeller blade root (13) widens outwards in the area of the damping elements (5). USE/ADVANTAGE - A propeller blade location for aircraft and of ground effect vehicles in which the bearing shaft is arranged at 90 deg. to the profile longitudinal axis of the propeller blade, with the loop rail being of one-piece construction.