Showing papers on "Blade pitch published in 1972"

Anti-torque, propulsion, and directional control system

Abstract: A helicopter devoid of a conventional exteriorly mounted antitorque rotor and having at the rear end of its aft fuselage a system utilized for auxiliary propulsion and anti-torque and directional control. This combination includes an axial-flow variable-pitch fan, a diffuser, an enlarged duct immediately contiguous to the diffuser, and sets of controllable variablegeometry, series-related, articulatable vanes mounted in a boattail configuration at the rear or egress end of the aft fuselage. The fan is located immediately forward of the diffuser, with the duct extending from the diffuser to the vanes, and an air inlet through which the flow of air is induced by the fan is disposed immediately forward of the fan. The vanes operate to dually provide auxiliary thrust and anti-torque control. In operating as an anti-torque control, the flowing air in the enlarged duct is made to converge and accelerate as such air is turned by positioned articulated vanes to achieve maximum efficiency in the production of the required anti-torque force. A pair of spaced elongated slots, with automatically closing lips, extend longitudinally of the fuselage skin, along the enlarged duct and below the sweep of the main rotor, to augment the performance of the basic anti-torque system by inducing a circulation of air around the fuselage which, with the downwash from the main rotor, produces an additional anti-torque force. By varying the pitch of the fan, a large power drain from the main rotor system during critical power-off auto-rotation descents is prevented. The blade pitch also controls auxiliary propulsion thrust, independently of yaw control, while skin friction losses of air flowing in the enlarged duct are minimized.

An Analytical Evaluation of the Controllable Twist Rotor Performance and Dynamic Behavior

Abstract: : A detailed analytical evaluation is made of a new rotor system with torsionally elastic blades and dual controls-the controllable twist rotor (CTR). The controls consist of conventional pitch horn linkages at the inboard end and an aerodynamic control flap at the outboard end. The analysis involves an aerolastic loads digital computer program which was developed to account for the blade response modes and blade control modes on either single or dual control rotors. Six response modes are included: blade flapping, blade feathering, blade lagging, blade flapwise bending, blade torsion, and control flap feathering. The two control modes are included separately and incorporate control system stiffness so that control loads are calculated. The aeroelastic analysis includes nonlinear inertia distributions, nonlinear airfoil characteristics, and inertial and mechanical coupling among the modes. The analysis outputs transient responses for stability evaluation and steady-state blade load and angle-of-attack distributions, blade dynamics, and rotor performance for each trimmed flight condition.

Measurements of Velocity Components in the Wake of a Full-Scale Helicopter Rotor in Hover

Abstract: : The report presents three-component wake velocity measurements made with a split-film total vector anemometer. The measurements were made in the wake of a full-scale OH-13E helicopter rotor which was mounted on a 60-foot rotor test tower at Mississippi State University. Time-averaged velocity distributions along wake radii at various distances below the rotor disk were measured for two conditions of disk loading and three combinations of blade pitch and rotor speed. Instantaneous velocity measurements were made across the helical vortex trails to investigate the effects of blade pitch and rotor speed on vortex structure, core size, transport velocity, and distribution of axial and tangential velocity components within the vortices.

Tail rotor mounting for coning relief

Abstract: Helicopter tail rotors provide anti-torque forces to maintain stabilized flight and further provide aircraft heading control. Aerodynamic forces generated on the rotor blade cause the tip thereof to move out of line with the pitch change axis of the blade, an effect known as ''''coning,'''' which produces undesirable forces on the rotor blade, the hub and the tail rotor control system. Each tail rotor blade is attached to a blade grip which is coupled to a yoke through laminated elastomeric bearings that provide in-plane stiffness while permitting blade coning in such a manner as to relieve the undesired coning effect forces.

Compound bearing for connecting a helicopter blade to a helicopter rotor

Abstract: A compound bearing for connecting a helicopter blade to a helicopter rotor, such as connecting the blade end-shaft to the rotor connected lead-lag damper so as to accommodate a large degree of blade pitch change motion and part misalignment due to other blade motions, which bearing is maintained within a minimum space envelope. The compound bearing includes a slip-type journal bearing enveloping the blade end-shaft and a spherical, laminated elastomeric bearing enveloping the journal bearing and connected to the rotor connected part, such as the lead-lag damper.

An Approximate Analysis of the Unsteady Lift on Airfoils in Cascade

Abstract: An approximate analysis is presented for determining the unsteady lift on airfoils in moving cascades, subject to disturbances in the inlet axial flow. The equations of motion are averaged across the pitch, and the mean pressure in each channel and the pressure difference across it are obtained. The lift on a reference blade dividing two blade channels is then estimated. The analysis is limited to flows in which the frequency parameter based on blade pitch is small, and to blading of low lift coefficient. Comparisons are given with earlier analyses, for flow past isolated airfoils (Sears), for quasi-steady flows through cascades (Gearhart, et al.), and for flow through an actuator disk of small blade chord and flow through cascades of flat blades (Whitehead).

Articulated helicopter rotor

Abstract: One or more helicopter blades are supported from a helicopter rotor in articulated fashion by a spherical elastomeric bearing which permits blade motion about the blade lead-lag axis and which includes a piston-cylinder type lead-lag damper. Lead and lag stops positioned selected distances from the blade shaft so that during rotor start-up operation, the uncentered blade will increase in lead angle to eventually be supported by the lag stop and the bottomed-out damper piston and so that, during rotor braking operation, the uncentered blade will increase in lead angle and eventually be supported by the lead stop and the bottomed-out lead-lag damper. This construction does not include a centering bearing.

Elastomeric helicopter rotor head with dynamic and static blade coning and droop stops

Abstract: An elastomeric helicopter rotor having a blade mounted for universal motion about the intersection of the blade pitch change, flapping and lead-lag axes and including blade coning and droop stops, including a ring member rotatably mounted about the pitch change axis on the blade and coning and droop stops constituting segments of circular members whose centers lie on the blade lead-lag axes and with the ring member and coning stop and droop stop members presenting mating surfaces to one another so that as the blade moves in lead-lag motion while the blade ring member is in line or surface mating contact with either the coning stop surface or the static or dynamic droop stop surfaces, a relative rotation will be established therebetween for full support of the blade throughout the lead-lag motion, without affecting blade pitch angle or flapping angle, without preventing independent blade pitch change, and without scuffing of parts.

Control devices of rotorcrafts

Abstract: In a rotor control system of rotorcraft having variable pitch rotor blades and swash plate system which is controlled by the pilot''s control stick and through which the cyclic pitch control and collective pitch control are effected, a link mechanism supported at a fulcrum is provided at least in the cyclic pitch control system and the position of said fulcrum is changed according to the forward flight speed of the rotorcraft, whereby the amount of longitudinal cyclic pitch change induced by the longitudinal control stick operation is decreased as the forward flight speed increases and concurrently the lateral cyclic pitch change is automatically imparted in the direction to compensate rolling motion of the rotorcraft, with the concomitant increase of said latter change as a function of the flight speed.

Quiet shrouded circulation control propeller

Abstract: The purpose of this invention is a propeller capable of generating high tst at reduced noise levels, weight and drag The propeller blades employ a tangential slot along the trailing edge of each propeller blade and circulation control blowing from the tangential slot over the trailing edge Lift is generated by the coanda blowing The lift is proportional to the momentum flow of the air out of the slot and is substantially independent of the rotational velocity Additionally a circulation control shroud expands the thrusting slipstream of the propeller so that the shroud diffusion angle is increased and the average exit velocity is reduced, thereby increasing efficiency and reducing noise

Engine load control

Abstract: This disclosure pertains to an engine load control which combines mechanical and fluid control devices whereby continuously to monitor and modify an engine load in conformance with an engine speed governor setting and fuel demand A valve actuating bridge is suspended in a frame by cam following means riding on separate speed and fuel cams At least one of the cams comprises adjustable segments whereby the response of the bridge may be matched with an engine speed-fuel relationship The bridge actuates a two-stage spool-valve which permits sequentially a large flow of fluid followed by a relatively small flow of fluid into a linear actuator; this two-stage valving permits rapid response to sudden load changes followed by a slow stabilization or return to equilibrium without hunting The linear actuator operates a pressure varying control valve in a pneumatic control circuit The speed cam is actuated by a pneumatic positioning linear actuator and the fuel cam is actuated by the fuel rack of an engine speed control governor An illustrated application of my invention is variation of blade pitch in a reversible controllable pitch propeller Blade pitch is changed by a hydraulic servo-mechanism; the servo-mechanism is controlled by a pneumatic circuit having a single lever control, a pair of pressure regulating relay valves, and a double-acting selfcentering positioning linear actuator Blade pitch is operatively determined by the lesser of the pressures established by the single lever control and the pressure varying control valves actuated by the engine load control

Variable pitch propeller

Abstract: This disclosure pertains to novel means whereby the blade pitch in a propeller may be varied by employing uni-directional rotation of a propeller shaft, a portion of the power driving the propeller, and a pair of braking means. A propeller hub having a plurality of pivotally mounted blades is mounted on the propeller shaft. A blade pitch actuator member having a hub-end and a brake-end extends through the propeller shaft into the propeller hub. An eccentric slider block secured to the hub-end of the actuator member is interconnected to each of the propeller blades. An actuator gear is screw-mounted on the brake-end of the actuator member. Three pairs of planetary each pair secured to a common shaft, are mounted on the propeller shaft in substantially parallel spaced relation to the axis of rotation of the propeller shaft. One of each pair of planetary pinions is meshed with the actuator gear and further meshed with an outer sun gear secured to a first brake actuated member. The other of each pair of planetary pinions is meshed with an inner sun gear secured to a second brake actuated member. Each brake actuated member has a brake actuator means. Application of the first brake means causes the actuator gear to rotate in one direction and application of the second brake means causes the actuator gear to rotate in the other direction. Rotation of the screw-mounted actuator gear causes movement of the actuator member and eccentric slider block, thus altering the propeller blade pitch.

Impact-damage-resistant, propeller-driven toy

Abstract: An impact-damage-resistant nose construction for use with propeller driven flying toy aircraft, the nose construction including an energy absorber connected to the fuselage and including a portion which is positioned between the propeller and the power plant with a movable coupling connecting a propeller shaft to the power plant so that the propeller may move axially relative to the power plant when the energy absorber is deformed by an impact.

Variable pitch propeller with emergency control

Abstract: A variable-pitch propeller has a pair of fixed pistons in the hub thereof, and a cylinder hydraulically movable on these fixed pistons and connected to the blades to vary the pitch of the blades. One of the fixed pistons is hollow and contains an auxiliary piston movable under the influence of a separate hydraulic system into engagement with the cylinder so that if the first hydraulic system fails, the auxiliary system can at least get the ship to port. The auxiliary hydraulic system can include a separate passage through the propeller shaft, or a branch from the lubricant passage through the propeller shaft.

Pitch varying mechanism for variable pitch fan

Abstract: The blades of a variable pitch fan of a gas turbine engine are rotated about their longitudinal axes as well as about the axis of the engine by a gear system which comprises a stationary actuator which initiates the pitch varying movement by producing a rotary output corresponding to the degree of pitch change required, an epicyclic differential gear driven by this output and the engine main shaft, and arranged to produce an output corresponding to the sum of the rotary output and the shaft rotational speed, and a pitch changing gear adapted to be driven by the output of the differential gear and to produce relative rotation of two annulus gears connected to rotate the fan blades about their own axes.

Ducted propeller systems suitable for tugs and pushboats

Abstract: For the application behind ships two different types of ducted propellers are considered; the ducted propeller where the nozzle accelerates the flow at the propeller and the ducted propeller where the nozzle decelerates the flow at the propeller. The first type of ducted propeller is now extensively used in cases where the ship screw is heavily loaded or where the screw is restricted in diameter. The accelerating nozzle offers a means to increase the efficiency of heavily loaded propellers. The second type of ducted propeller is used to increase the static pressure at the impeller. This nozzle may be used if retardation of propeller cavitation is desired. This paper deals with the first type of nozzle. The open-water test results of ducted propeller systems suitable for application on pushboats and tugs are given. In addition the results with a nozzle specially suited for astern operation are supplied. The effect of the appendages (rudders, struts etc.) on the characteristics of ducted propeller configurations suitable for pushboats and single-screw tugs has been studied. The optimum value of the flanking rudder angle has been determined. Finally, the results of open-water tests with ringpropellers, ringpropellers in nozzles and a multiple nozzle-ringpropeller system are discussed.

Stresses in the Blades of a Cargo Ship Propeller

Abstract: The problems of propeller-blade failures on a single-screw ship of the "Lichtenfels" class is solved by full-scale measurements, model tests and a calculation with elementary theory. The results show that the failures are caused by wake-induced forced oscillations of the blades. The agreement of the results of the three investigations is acceptable. It is further shown by model tests in regular and irregular waves that the stresses in a seaway can be much higher than those in smooth water.

Helicopter blade pitch lock

Abstract: A helicopter blade pitch lock in which the movable and stationary portions of the pitch change servos carry over-lapping concentric sleeve members with aligned apertures therein to receive pitch lock pins equidistant on opposite sides of the servo-axis. There is a sequencing arrangement wherein the unlocked pitch lock pins are locked out of pitch lock position, and wherein the pins can sequentially be freed for pitch locking when desired, actuated to their pitch lock position, and locked in their pitch locked position when pitch locking is desired, and wherein the pins can sequentially be freed in their pitch lock position, withdrawn from their pitch lock position, and locked out of their pitch lock position when pitch lock is not desired.

Pump, fan or turbine with variable blade rake

Abstract: 1278825 Mixed-flow pumps and fans; turbines NATIONAL RESEARCH DEVELOPMENT CORP 8 April 1970 [10 April 1969] 18503 /69 Heading F1C and FIT In a pump, fan or turbine in which blades mounted on a rotor boss within a part-spherical housing may be varied in rake angle so as to vary the flow between predominently axial and predominantly radial, blade supports mounted in the boss are each rotatable about a blade support axis intersecting the rotor axis and at an angle to the rotor axis which lies between two extreme limits of adjustment of the rake angle, each blade support defining a blade pivot axis intersecting the rotor axis and at an angle to the blade support axis, means operable externally of the machine for rotating the blade support relative to the boss about the blade support axis, planetary gear means comprising a gear fast with the blade and concentric with the blade pivot axis and a gear centered upon the blade support axis and means for making the latter gear fast with the boss, whereby, on rotation of the blade support about the blade support axis, the pitch angle of the blade bears a predetermined relationship to its rake angle Each rotor blade 6, Fig2, of a pump is pivotally mounted on a blade support 14 which in turn is pivotally mounted on a rotor hub 25, the blade axis 36 and the blade support axis 17 intersecting the rotor axis at a common point 37 Adjustment of each blade 6 between the full-line position in which the flow is predominantly axial and the dotted position 19, see also Fig 3, in which the flow is predominantly radial can be effected while the pump is running by a hand wheel 58 which causes longitudinal displacement of a non-rotating pushrod 55 passing through the hollow shaft 5 of the rotor The push-rod 55 engages a cam block 50 through flanges 66, 67 to displace the cam block along guide bars 51, 52 carried by the rotor hub The cam block 50 is engaged by cam followers 48, one for each rotor blade, which effect rotation of the blade supports 14 about their axes 17 through gearing 44, 42 A hollow bush 29 forming a bearing for the spindle 32 of each blade support 14 is formed with a pinion 40 which meshes with an idler pinion 34 carried by the blade support, the idler pinion in turn meshing with a pinion 38 fast with the blade spindle 35, the pinions forming a planetary gearing which, as the blade support is turned to adjust the blade rake angle, causes the blade to turn in the opposite direction relative to the blade support so that the blade pitch angle remains unaltered The tooth ratio of the pinions 38, 40 may differ from unity to cause the pitch angle to increase or decrease instead of remaining unaltered In another arrangement, Fig7, the gear 44 is carried by a central shaft 81 Gearwheels 82, 83 on the rotor shaft 5 and shaft 81 are connected via respective pinions 84, 85 to a ring gear 86 A normally stationary ring 89 carrying the pinion 85 can be rotated to effect the blade adjustment In a further embodiment, Fig6 (not shown) the gear (44) is driven, for adjustment of the blades, by an electric, hydraulic or pneumatic motor carried by the rotor hub

A method for calculating the hydrodynamic characteristics of marine propellers

Abstract: This paper deals with the third problem of the propeller lifting surface theory in which the circulation distribution is obtained in relation to the geometry and the working condition of a propeller. In the problem, a two-dimensional integral equation has to be solved. In order to carry out the numerical solution reasonably, collocation method which is popular in the wing theory was applied to the propeller theory. In addition, the simplified nonlinear theory with a constant pitch and the circulation reduction due to the viscosity were taken into consideration. A practical method for calculating the hydrodynamics of marine propellers was completed and programmed for the computer. By using the circulation distribution of the propeller, the corresponding two-dimensional wing which has the same hydrodynamic characteristics as a propeller section can be derived. The pressure distribution over the propeller blade is obtained by applying Moriya's method to the wing.

A perturbation solution of rotor flapping stability

Abstract: : The stability of the flapping motion of a single blade of a helicopter rotor is examined using the techniques of perturbation theory. The equation of motion studied is linear, with periodic aerodynamic coefficients due to the forward speed of the rotor. Blade pitch feedback proportional to both flapping displacement and flapping rate is included. Four cases are CONSIDERED: small and large advance ratio, and small and large Lock number. The solution of this problem demonstrates the information which may be obtained using perturbation techniques.

Tendencies of marine propeller shaft excitations

Abstract: From two-dimensional considerations a relation has been derived between the dynamic propeller shaft forces and the speed of ship and propeller. A factor, defined as the index of unsteadiness, enables the prediction of propeller vibratory force, for conditions different from a test condition. Considerations have been made concerning the level of the vibratory output of multiple propeller arrangements, as compared to regular single propeller arrangements.

Ducted propeller systems for marine vessels

Abstract: In a ducted propeller system for ship propulsion, comprising a propeller working in a fixed propulsion nozzle and rudder blades or shutters disposed at the nozzle entry on either side of the central vertical fore-and-aft plane of the nozzle, the rudder blades are toed out and the angle of the toeing is varied up the height of each blade to correspond to the different nozzle flow entry conditions that obtain at different regions of the nozzle entry due to the effect of propeller rotation.

Theory/test correlation of helicopter rotor blade element airloads in the blade stall regime

Abstract: The effects of stall on a rotor blade element in a three-dimensional rotating environment was investigated. The model rotor test provided blade element airloads and local boundary layer flow characteristics at the three-quarter blade radius position for a wide range of rotor operating conditions. A description of the test program and the test results are presented.

Lifting Surface Theory for Statically Operating Propellers.

Abstract: : A method was derived and a computer program formulated which utilizes a vortex-lattice lifting surface representation to model a statically operating propeller and to compute its performance. The computer program has been written to yield propeller performance characteristics for a prescribed blade geometry (the direct problem) or to yield blade camber distribution (the indirect problem). All of the results described were obtained for the direct problem. Performance characteristics, including propeller thrust and torque coefficients, were computed for three propeller configurations and were compared with test data and with results computed using lifting line theory. (Author Modified Abstract)