Showing papers on "Blade pitch published in 1970"

Reverse velocity rotor and rotorcraft

Abstract: A rotary wing aircraft and rotor control system for such aircraft, which uses the reverse velocity airflow produced by high airspeeds of the aircraft across the retreating blade to generate positive lift on the retreating blade. Blade pitch control means and method for such aircraft providing a two/revolution, cam or higher order cyclic pitch input to generate more uniform lift in the advancing and retreating blade sectors of rotor motion. A main rotor for such aircraft having a new airfoil shape adapted to more efficiently generate positive lift from the reverse velocity airflow, and also having slotted flaps or other auxiliary lift devices for increasing lift at low aircraft airspeeds. A twistably-mounted tail rotor for such aircraft adapted for counter-torque operation at low aircraft airspeeds and for forward propulsion at high airspeeds.

The response and airloading of helicopter rotor blades due to dynamic stall

Abstract: : An aerodynamic model is constructed for the application of the properties of dynamic stall of airfoils to the calculation of the airloads and blade motion of helicopter rotor blades. Dynamic stall occurs on an airfoil undergoing pitching motion at high angle of attack, and is characterized by peak section lift and moment much larger than the corresponding static stall loads. A method is developed for the solution of the equations of motion of a rotor blade by means of harmonic analysis. The effect of dynamic stall on the blade torsional motion at high advance ratio is examined, and comparison is made with the limited experimental data available. An increase in the dynamic stall angle is shown to significantly decrease the amplitude of the pitch motions.

Coaxial helicopter rotor system and transmission therefor

Abstract: DISCLOSED IS A HELICOPTER CONTROL SYSTEM HAVING A UNITIZED ROTOR AND TRANSMISSION ASSEMBLY FOR A CRAFT USING COAXIAL COUNTER-ROTATING ROTORS. THE ASSEMBLY IS GIMBAL MOUNTED SO THAT THE TRANSMISSION ACHIEVES DIRECTIONAL CONTROL WITHOUT ALTERING BLADE PITCH AND THE ROTOR HEAD IS OF SIMPLIFIED CONSTRUCTION TO ACHIEVE COLLECTIVE CONTROL OF THE BLADES.

Apparatus for testing the blade anchorage of turbine blades

Abstract: An improved testing apparatus for determining tightness, deformations and weak points of the blade anchorage of a turbine blade. The apparatus operates by applying forces to a blade or portion thereof which includes a blade base, attached in the normal fashion to a simulated portion of a turbine rotor. A force in a direction corresponding to the radial direction in a turbine rotor and hence to the centrifugal force in a rotating rotor is applied by attaching the blade and rotor portion to respective first and second yokes and drawing the blade and rotor portions apart. A force corresponding to the damping forces in the axial and/or tangential directions of a turbine rotor is applied by an additional device while the blade and rotor portions are held in the yokes. At least one end of the blade is mounted on its respective yoke by means of fluid pressure bearing system whereby the various forces can be applied to the blade in a substantially frictionless manner.

Rotary wing aircraft lift and propulsion method and systems

Abstract: A rotary wing aircraft lift and propulsion method and system in which burner thruster units mounted on the lift-producing rotor at a position spaced radially from the axis of the rotor generate moments to turn the rotor about its axis. An air compressor is driven by the rotor through a speed increasing drive and pumps air at a pressure exceeding atmospheric through ducts in the rotor extending out to the respective burner thruster units while fuel is shock in them to produce jets reflecting combustion gases generating thrust to turn the rotor about its axis. In addition to the lift-producing rotor, a propeller serves to drive the aircraft forward or backward, and the power for driving this propeller is derived from the rotation of the rotor itself. To control forward or backward motion of the craft, the propeller pitch is varied, and also it may be disengaged by use of a clutch. There is a forward-motion steering rudder and a downwash deflector rudder which are both operable by the same control for counteracting the moderate rotor torque exerted on the aircraft body and for steering the craft.

Tilt linkage for bulldozer blade mounting assemblies

Abstract: A mounting assembly providing for tilt adjustment of a bulldozer blade. The blade is pivotally supported by a pair of push arms. Motor means are pivotally interconnected between the respective push arms and the blade for adjusting blade pitch with one of the motor means being connected with the blade by means of a pivotal link. The blade is tilted by additional motor means interconnected between the blade and the link.

Vibration control for rotors

Abstract: A helicopter rotor has weights, one for each blade, mounted on arms which are pivoted remote from the axis of rotation of the rotor. The weights are connected through adjustable linkage mechanism with their respective blade horns in such manner that the system including all moving parts involved in the blade pitch motion can be turned to a desired frequency which is equal to the basic frequency of the blade vibration due to forward flight of the helicopter. When the tuned system is excited by aerodynamic vibratory forces at the tuned frequency, a pitch vibration of the blade results which leads to the generation of additional aerodynamic forces tending to cancel the original vibrational forces.

Belt-driven pi-pitch cycloidal propeller

Abstract: A cycloidal propelling device for use on submersibles which operates in a flooded sea water environment and thereby eliminates the need for a protective sealing housing containing oil. While the propeller blades of the device are being driven in an orbital path, if a change in blade pitch is desired, a control shaft is rotated. Rotation of the blade pitch control shaft rotates a central pinion gear which drives a timing belt. Movement of the timing belt simultaneously and in synchronization rotates propeller blade gears and changes the pitch of the propeller blades which are mounted thereon with water-lubricated plastic bearings. Plug-in, pullout type plastic breakway propeller blades are used for easy repair and replacement.

Method of correcting a number of revolution of a screw propeller

Abstract: A method of adjusting the number of revolutions of a screw propeller having the steps of cutting the trailing edge of each blade of the propeller from and along the trailing edge, and working and shaping the face of the blade to a curvature to provide a proper setback.

Ship propulsion system having separate propulsion units for cruise and low speeds

Abstract: A ship is provided with a propulsion unit for cruising speed and a cycloidal propeller as a second propulsion unit used for slow speeds. The cycloidal propeller has a propeller housing and a propeller runner with the propeller blades being equi-distantly spaced on a blade orbit and pivotally mounted so that the blades may be pivoted in directions parallel to the direction of travel of the ship. The cylinder propeller may be used as a non-rotating passive rudder when the ship is cruising and may also be used for steering. Structures are disclosed for pivoting of the blades into various positions.

Helicopter rotor blade

Abstract: A HELICOPER BLADE COMPRISING A PLURALITY OF BONDED COMPONENTS FORMING A UNITARY STRUCTURE HAVING A LONGITUDINALLY EXTENDING PORTION, A GRADUAL TRANSITIONAL PORTION AND A HOLLOW TUBE-LIKE PORTION. THE HOLLOW ROOT PORTION OF THE BLADE IS SECURED TO A ROTOR.

Cycloidal Propulsion of Submersibles

Abstract: The concepts of 1) true advance ratio and 2) normalized blade pitch ratio are introduced and discussed in terms of pertinent cycloidal propulsion criteria. The equations of motion pertaining to the blade dynamics of cycloidal propulsion are presented. Numerical results from a computer study are discussed. Kramer's effect and hydrodynamic hysteresis are included in the determination of propeller torque and force coefficients.

Real-time simulation of a helicopter rotor on an analog computer

Abstract: An accurate real-time simulation of a helicopter rotor can be achieved on a high-speed analog computer. By using repetitive operation and integrating along each blade every 2.5 milliseconds, the double integration required to determine rotor torque, thrust, moment, and rearward and sideward rotor forces is accomplished. The lift and drag coefficients are continuously calculated at all points along the blade. The same analog equipment used to calculate quantities for one blade is used for other blades by chang ing appropriate initial conditions. This analysis provides a transient rotor solution in which integration out the blade is accomplished every five rotor azimuth degrees. One console of a Hybrid Systems, Inc., SS-100 Analog/Hybrid Computer is used for the rotor solution.

Improvements in or relating to reversible pitch propellers

Abstract: 1,189,444. Controlling reversible pitch propellers. HAWKER SIDDELEY DYNAMICS Ltd. 18 Sept., 1967 [26 July, 1966], No. 33662/66. Heading B7V. In a reversible pitch propeller, twisting moments on the propeller blades such as blade 1 due to rotation of the propeller are employed to bring about an increase in blade pitch angle automatically with increase in engine power, irrespective of whether the blades are in forward or reverse pitch, and forward or reverse pitch is selected by movement of a pilot's throttle or power control lever from an idling or neutral setting into a forward throttle range or a reverse throttle range, respectively. Pins 5 and 6 on each blade root are both out of engagement with spring-loaded piston 7 at zero pitch and one or the other comes into engagement with the piston according to whether the angular direction of the propeller is forward or reverse. In the embodiment shown, shaft 11 is coupled to each blade by a radial pin 16 which moves axially with the shaft and is engaged in a cam slot 17 in the blade root.

Improvements in or Relating to Rotor and Propeller Blades.

Abstract: 1,188,946 Variable length propeller blade WESTLAND AIRCRAFT Ltd 6 Oct, 1967 [24 Oct, 1966], No 47724/66 Headings B7V and B7W A blade of a variable diameter propeller or rotor, eg for a convertiplane, comprises a spar 11 along which the blade 10 is retractable and extendable, the twist of the blade being varied during the final stages of retraction The blade 10 may be retracted by the rotation of the spar 11 engaging a recirculating ball nut 15 formed integral with an outer spar 14 which is prevented from turning by splines 16 which engage splines 18 on the end of a rod 17 rotation of which varies the blade pitch The blade pitch may additionally be varied during retraction of the blade by making the splines 16, 18 helical The blade 10 may comprise ribs 13 each with keyways to engage helical splines 19 on the outside of spar 14 The blade is usually held against stops 25 due to the centrifugal acceleration The blade has at its inboard end a boss 21 containing racks 22 which engage pinions 23 which move with the spar 14 During the final stages of retraction, the pinions 23 are forced to turn as further racks 24 engage thrust bearings 28, thereby causing the ribs 13 to slide along the splines 19 causing the blade to twist

Rotor Head for a Mechanically Driven Helicopter

Abstract: 1,189,136. Helicopter rotor. COSTRUZIONI AERONAUTICHE GIOVANNI AGUSTA S.p.A. 17 Oct., 1969, No. 23363/67. Heading B7W. [Also in Division F2] A hub for a mechanically driven helicopter rotor comprises laminated ties 4 connected at their outboard ends to blade attachment members 1 and at their inboard ends to parallel sleeves 3 normal to the axes both of the ties and of rotation, the sleeves 3 comprising part of a central frame transmitting drive to the blades. Blade pitch is variable as members 2 are rotatable about axes radial of the rotor.

Helicopter Application Studies of the Variable Deflection Thruster Jet Flap.

Abstract: : The results of an analytical study to determine the application of a blown flap device called the Variable Deflection Thruster (VDT) to a helicopter rotor are presented and analyzed. The study is part of a longer-range program to investigate and develop control techniques for stabilization of the higher harmonic modes of helicopter rotor blades. A high-speed digital computer program was used to calculate the aerodynamic characteristics and performance of a Sikorsky CH-34 rotor system as though equipped with a blown two-dimensional section. The study was made over a range of rotor flight profiles and operating parameters including advance ratio, shaft angle of attack, blade pitch, tip Mach number, jet deflection angle and blowing rate. Performance of the blown rotor is compared to the conventional CH-34 rotor to illustrate VDT application effectiveness. Results show that the operating lift capability and propulsive force of the CH-34 rotor are increased when the rotor is equipped with a blown device. A preliminary analysis of the attenuation of rotor hub-shear variation by programmed blowing is also shown. In all cases, improved performance through application of blown control requires additional power. (Author)

Isolated Cyclic Pitch Propeller: Results of Wind Tunnel Test

Abstract: : The report presents the results of wind tunnel test BVWT 057 performed in the Boeing Vertol V/STOL wind tunnel on an isolated 3-bladed cyclic pitch propeller with a total activity factor of 480. The primary objectives of the test were to determine: the pitching moment capability from the propeller over a wide shaft angle range from 0 up to 120 deg through the transition flight regime of a tilt wing aircraft and, the effect of cyclic pitch on power. The effects of cyclic pitch on propeller thrust, normal force, yawing moment, and side force were also measured.

On a Method of Measurement of Propeller Bearing Force Exciting Hull Vibrations

Abstract: For analyzing the propeller vibratory bearing force and moment of a self-propelled model, it is necessary to obtain the thrust and torque force variations of a blade of the multi-bladed propeller which rotating in ship wake. This paper presents a method of direct measurement of these force variations by the use of two strain gauges applied at the surface of the root of the blade. The.hydrodynamic force induced by the propeller blade is separated from total force included centrifugal force of the blade by attempting the strain measurement of the rotating propeller in air. The thrust and torque forces are obtained from the two strain components produced by the above hydrodynamic force measured by the two strain gauges. The so-called wake bearing force and moment are easily calculated from the Fourier components of the thrust and torque variations of one blade of the multibladed propeller obtained by the method mentioned above. As an example of the present experiment, the wake bearing forces and moments of four, five and six bladed propellers of a container model are illustrated. It is of interest that considerable discrepancies appear in the phase lags of the peak of force variations between the results of the quasi-steady method using the wake distribution curve and the present unsteady force measurements of the thrust and torque variations.

Improvements in or relating to Lift Rotors and Propellers.

Abstract: 1,188,947. Variable twist propeller blades. WESTLAND AIRCRAFT Ltd. 6 Oct., 1967 [24 Oct., 1966], No. 47725/66. Heading B7W. A variable twist rotor or propeller blade comprises a substantially hollow blade 10 having a twistable envelope 11 enclosing a series of rib members 12 each engaging helical keys 14 on a spar 13, having at its inboard end a chamber 16 movable (e.g. along splines) within an end fitting 17 which has means (e.g. a piston 19 and a passage 25 to admit hydraulic fluid to the cylinder 20) to move the spar lengthwise of the blade moving the ribs along the keys 14 to warp the blade. The end fitting 17 may have an arm 24 to effect blade pitch change.

An Improved Blade Root Design for Axial Flow Compressors (and Turbines)

Abstract: To save weight, designers of aircraft gas turbines aim to produce axial compressors with fewer rows of blades and greater mass flows per unit of frontal area. These improvements often consist of increases in blade tip speeds and reductions in the ratio of the hub to tip diameters. As the efficiency of transonic blading is partly dependent upon a low value of blade pitch/chord it is now frequently necessary to design a blade with a greater actual chord at the tip than at the hub.

Four Prop Tilt Wing with Cyclic Pitch Propellers: Results of Full Span Wind Tunnel Test/Phase 1

Abstract: : The report presents the results of wind tunnel test BVWT 061 (Phase I test of two phase test program) performed in the Boeing-Vertol V/STOL wind tunnel on a powered four prop tilt wing full span model equipped with cyclic pitch propellers for longitudinal control. Items evaluated include cyclic pitch control in hover (in and out of ground effect), yaw control in performance, plus basic longitudinal stability and control throughout transition with a high horizontal tail. Propeller hub pitching moment and normal force were also measured during this test so that in conjunction with a previous isolated propeller test,the influence of the wing/flaps/fuselage on the propeller forces and moments could be determined.