Showing papers on "Blade pitch published in 1987"

Aircraft cabin noise control apparatus

Abstract: In propeller of fan driven aircraft, cabin noise levels may be reduced by adjustment of the phase relationship between a reference propeller or fan and some or all of the other propellers or fans. An aircraft cabin (1) contains four microphones and two loudspeakers which form the active elements of a noise control system. The microphone outputs are fed via amplifiers to a digital signal processor (11) having an adaptation algorithm in a memory store. The processor generates an error signal which is used to adjust the synchrophase angle between the reference propeller and a synchrophased propeller, controlled by a synchrophaser. Thus the synchrophase angle is varied dynamically during flight to minimize propeller noise in the cabin over a range of flying conditions.

Propeller and coupling member

Abstract: Disclosed is a marine propeller for inboard, outboard, or inboard/outboard motors. The propeller is made from a non-metallic composite material that will not deform or deflect even at very high horsepower or RPMs. At the same time, the propeller is substantially less expensive than traditional metallic propellers. An especially unique feature of the propeller is that, unlike metallic propellers, it will shatter when it strikes a solid object in the water, thereby avoiding the engine and drive line damage that occurs when rigid metallic propellers strike a solid object. Also disclosed is a coupling member that permits the propeller to be adapted for use with most inboard/outboard motor configurations.

Wind-tunnel evaluation of an advanced main-rotor blade design for a utility-class helicopter

Abstract: An investigation was conducted in the Langley Transonic Dynamics Tunnel to evaluate differences between an existing utility-class main-rotor blade and an advanced-design main-rotor blade. The two rotor blade designs were compared with regard to rotor performance oscillatory pitch-link loads, and 4-per-rev vertical fixed-system loads. Tests were conducted in hover and over a range of simulated full-scale gross weights and density altitude conditions at advance ratios from 0.15 to 0.40. Results indicate that the advanced blade design offers performance improvements over the baseline blade in both hover and forward flight. Pitch-link oscillatory loads for the baseline rotor were more sensitive to the test conditions than those of the advanced rotor. The 4-per-rev vertical fixed-system load produced by the advanced blade was larger than that produced by the baseline blade at all test conditions.

Collective control system for a helicopter

Abstract: Pilot workload is reduced in a helicopter having a force-type, multi-axis sidearm control stick by providing a displacement-type control stick for collective blade pitch control. Either stick may be used by the pilot. When the force-type stick is employed, a trim system causes the displacement-stick to track a collective position command signal which is provided to the blade actuators. Changeover of control to the displacement-type control stick is accomplished either with a switch, or by moving the collective-type control stick. The signals associated with each control stick are alternately faded in and out to assure a smooth transition when collective control is switched over from one to the other.

Control system for synchrophasing aircraft propellers

Abstract: Control system for synchrophasing the propellers of an aircraft, each propeller provided with a blade pitch controller for controlling the blade angle of the propeller, the systen containing for each propeller a control loop, comprising: a revolution rate controller, means for determining the blade passing frequency, an adjustable propeller revolution rate reference source supplying a revolution rate setpoint control signal, comparator means for comparing the blade passing frequency with said setpoint to generate an error signal for the revolution rate controller. The control system comprises furthermore for each propeller: means for determining the position of the propeller blades, a reference signal source, adjustable means changing the phase reference signal a comparator to compare the sensed position of the propeller blades with said phase reference signal, providing a control signal to be combined with the output signal of the revolution controller, and that the system furthermore comprises means to adjust said propeller revolution rate reference source and said phase reference signal deriving means such that for each revolution rate setpoint a predetermined mutual phase relationship between the propellers are maintained.

Helicopter rotor control systems

Abstract: A helicopter rotor control system includes a plurality of control rods (31) extending downwardly from pitch control means (24) through a hollow rotor drive shaft (12) and gearbox (14) for connection directly to individual actuators (36) located generally symmetrically about an axis of rotation (15).

Self-feathering rotary wing

Abstract: A controllable lifting rotary wing for an aircraft wherein each rotor blade is mounted in such a manner that it has freedom to oscillate in pitch about its feathering axis. The aerodynamic center on each rotor blade is displaced forward of this feathering axis over at least a portion of the span. Cyclic aerodynamic forces on this spanwise portion cause the blade to change pitch sinusoidally once-per-revolution of the rotor whenever the rotary wing aircraft experiences a change in flight attitude or velocity. The result is that the rotor blades automatically and continuously change pitch to cancel out cyclic lateral flapping moments which are normally produced on a helicopter rotor blade by such a flight disturbance. This rotary wing has greatly improved stability by virtue of this self-feathering action. Cyclic pitch control moments are applied to the rotor blades by indirect means which do not interfere with automatic blade feathering. Means for control of collective pitch of the blades are also provided.

Analytical and experimental investigation of mistuning in propfan flutter

Abstract: An analytical and experimental investigation of the effects of mistuning on propfan subsonic flutter was performed. The analytical model is based on the normal modes of a rotating composite blade and a three-dimensinal subsonic unsteady lifting surface aerodynamic theory. Theoretical and experimental results are compared for selected cases at different blade pitch angles, rotational speeds, and free-stream Mach numbers. The comparison shows a reasonably good agreement between theory and experiment. Both theory and experiment showed that combined mode shape, frequency, and aerodynamic mistuning can have a beneficial or adverse effect on blade damping depending on Mach number. Additional parametric results showed that alternative blade frequency mistuning does not have enough potential for it to be used as a passive flutter control in propfans similar to the one studied. It can be inferred from the results that a laminated composite propfan blade can be tailored to optimize its flutter speed by selecting the proper ply angles.

Collective pitch change system for teter-bar type gyroplane rotary wing aircraft

Abstract: A collective pitch change system for gyroplane rotary wing aircraft is provided. The system is particularly adapted for teter-bar rotors and is simple and direct. The system can change the blade pitch while the rotor is rotating to permit jump take-offs.

Double reverse revolution propeller apparatus

Abstract: A double reverse revolution propeller apparatus includes front and rear propeller wherein the rear propeller is rotated at higher speeds than the front propeller. When seizure occurs, an inner shaft is disconnected from an engine at an inner shaft connection unit and is connected to an outer shaft at an inner and outer shaft connection unit to be driven in the same direction as the outer shaft. The ratio of absorption horsepower of the front propeller to the rear propeller can to be substantially equal to the ratio of rotational speed of the front propeller to that of the rear propeller. One or both of the front and rear propeller can include a variable pitch propeller. The front propeller can have more blades than the rear propeller.

Air borne craft, for example helicopter, and related devices

Abstract: In a vehicle or device a fluid motor is employed to drive rotary members, such as wheels, propellers, tracks. The motor is provided with an arrangement which includes a control means and an axially moveable member. By utilizing the control means, for example, by a flow of fluid, the axially moveable member is used to apply an action, which is not common to the usual operation of fluid motors. The arrangement may be used to arrest the rotor of the motor from rotation when no pressure is in the driving fluid line. It may also be used to control the pitch of propellers with variable pitch arrangements. Also possible is to use the arrangement to automatically obtain an auto-rotation of rotor blades on vertical axes of vertically take off and landing vehicles, when the pressure in the fluid line to the motors for driving the motors drops below a predetermined minimum of pressure. The speciality of the preferred embodiment which is shown in FIGS. 18, 19, 24 to 26 and 34 to 37 consists in the provision of a tail propeller, a main lift propeller and a rate of power varying means in the transmission between the power plant and the mentioned propellers. Thereby the tail propeller acts as forward driving propeller, while the main lift propeller may act with vertical or slightly inclined axis or it may be stopped to rest. The vehicle can thereby fly as a helicpoter or selectively as a gyrocopter and as an aircraft flying on wings if the wing assembly is assembled to the vehicle.

Revolution control for wind power generator

Abstract: PURPOSE: To effectively utilize the power without discharging the power by connecting a flywheel onto the input shaft of a power generator turned by a wind power through a continuously variable transmission means and storing the power in the flywheel and supplying the accumulated power into the power generator. CONSTITUTION: The rotary shaft 2 of a propeller 1 turned by a wind power is connected with the input shaft 6 of a power generator 5 through the speed increasing gears 3 and 4. A blade pitch controller 8 is connected with the propeller 1, and the pitch angle of the propeller 1 is set to the pitch angle having the highest efficiency for outputting the average power according to the average wind speed calculated from the output of a wind speedometer 9. Further, a flywheel 14 is connected with the input shaft 6 through a continuously variable transmission means 13 in which a hydraulic pump 10 and a hydraulic motor 11 are connected through a hydraulic pipe 12. When the wind power exceeds the average wind speed, the excessive power is accumulated in the flywheel 14, and when the wind speed lowers below the average wind speed, the accumulated power is outputted. COPYRIGHT: (C)1988,JPO&Japio

Variable pitch marine propeller system

Abstract: A variable pitch marine propeller comprising two removable symmetrical propeller blades with cylindrical bases each having a drive lug attached proximate the driving edge of the point of attachment of each blade. A coupling are associated with the drive lugs of the bases and structured to hold the blades by the bases to align and simultaneously rotate the pitch of the blades in equal and opposite directions in response to movement of the coupling. A hub sub-assembly encases the coupling and bases of the blades to allow the blades to pivot and assume a forward or rearward pitch. The hub sub-assembly has a front end, and a rear end capable of mounting onto a drive shaft. A spring is associated with the coupling to initially position said coupling in a position which holds the blades in a rear pitch configuration. A hydraulic piston system is associated with the coupling means to provide a predetermined fixed pressure on said coupling to alter the spacing pressure and move the coupling to a position which causes the blades to assume the desired forward or rearward blade pitch.

Determination of Propeller-Ice Milling Loads

Abstract: In designing ice transiting ships, a major concern is the design of the propeller to provide adequate strength to resist ice loads due to propeller ice milling while still providing good propeller efficiency for open water observations as well as high icebreaking thrust at slow advance speeds. As a result, propeller design is a compromise between strength and efficiency. This is especially true for ice transiting ships that must transit long distances on ice-free routes and then perform difficult ice-breaking operations. The geometric properties of a propeller blade that provide good strength are blade width and thickness. Unfortunately, increasing these properties does not provide the best efficiency. Propeller design for ice transiting ships in general has tended to favor strength and reliability over efficiency in design compromises. The purpose of this paper is to outline a methodology for determining propeller ice milling loads as a function of propeller characteristics, propeller speed, ship speed, ice conditions and depth of ice milling to help in the propeller design process.

The effect of front-to-rear propeller spacing on the interaction noise of a model counterrotation propeller at cruise conditions

Abstract: The effect of front-to-rear propeller spacing on the interaction noise of a counterrotation propeller model was measured at cruise conditions. The data taken at an axial Mach number of 0.80 behaved as expected: interaction noise was reduced with increased spacing. The data taken at M=0.76 and M=0.72 did not behave as expected. At some of the test conditions the noise was unchanged; others even showed noise increases with increased spacing. A possible explanation, involving the amount of downstream blade area impacted by the tip vortex, is presented.

A method of controlling the propulsion machinery in a ship having a variable-pitch propeller

Abstract: not available for EP0089960Abstract of corresponding document: WO8203831In a method for controlling the propulsion machinery in a ship having a variable-pitch propeller, the ship's speed is first adjusted to a value within a predetermined interval containing a desired value of the speed. This adjustment is effected by changing the number of revolutions of the propulsion machinery and the propeller pitch, whereupon the number of revolutions and the pitch are changed, while maintaining the speed within the said interval. For each change in the number of revolutions and the pitch, it is checked whether the change has resulted in an increase or a cutdown in fuel consumption. These changes are effected until a combination of the number of revolutions and the pitch is attained, which provides for minimum fuel consumption in the propulsion machinery.

Vertical wind energy converter which is mechanically controlled in dependence on wind speed

Abstract: Vertical rotor (wind energy converter) having two or more vertical blades, on the outside of which there are mounted folding blades which are in the shape of a half-shell and which, when all opened out, produce an upright, circular rotor body which is closed on the outside. Being rotatably mounted on one side, the folding blades mounted on the blades of the rotor automatically open on the side of the rotor receiving the wind and automatically close on the other side of the rotor, facing away from the wind. The folding blades, which are situated approximately opposite one another in pairs, are connected to one another by means of cable bracings, the length of cable determining the possible opening-out angle of the other folding blade. The cable bracings, which in each case connect two folding blades, are horizontally guided through the axial region of the rotor on deflection rollers, and, when raised here, can bring about a horizontally effective shortening of the cable leading to the open folding blade in each case, ie. leading to a reduction in the opening-out angle of the said folding blade. As a result of the fact that the folding blades are opened by the wind on the side of the rotor which receives the wind and are closed by it on the side of the rotor facing away from the wind, excellent wind resistance values which are compatible with rotation are yielded by a concave, wind-receiving side of the rotor and a convex side of the rotor facing away from the wind. The rotary energy delivered by the rotor can be set to predetermined ranges of wind speed by means of a wind flap control system ... Original abstract incomplete.

Helicopter main-rotor speed effects on far-field acoustic levels

Abstract: The design of a helicopter is based on an understanding of many parameters and their interactions For example, in the design stage of a helicopter, the weight, engine, and rotor speed must be considered along with the rotor geometry when considering helicopter operations However, the relationship between the noise radiated from the helicopter and these parameters is not well understood, with only limited model and full-scale test data to study In general, these data have shown that reduced rotor speeds result in reduced far-field noise levels This paper reviews the status of a recent helicopter noise research project designed to provide experimental flight data to be used to better understand helicopter rotor-speed effects on far-field acoustic levels Preliminary results are presented relative to tests conducted with a McDonnell Douglas model 500E helicopter operating with the rotor speed as the control variable over the range of 103% of the main-rotor speed (NR) to 75% NR, and with the forward speed maintained at a constant value of 80 knots

Wind tunnel tests on a one-foot diameter SR-7L propfan model

Abstract: Wind tunnel tests have been conducted on a one-foot diameter model of the SR-7L propfan in the Langley 16-Foot and 4 x 7 Meter Wind Tunnels as part of the Propfan Test Assessment (PTA) Program. The model propfan was sized to be used on a 1/9-scale model of the PTA testbed aircraft. The model propeller was tested in isolation and wing-mounted on the aircraft configuration at various Mach numbers and blade pitch angles. Agreement between data obtained from these tests and data from Hamilton Standard validate that the 1/9-scale propeller accurately simulates the aerodynamics of the SR-7L propfan. Predictions from an analytical computer program are presented and show good agreement with the experimental data.

Obstacle in front of a propeller

Abstract: In combination with a propeller disposed in an aircraft, aft from the nose portion of the craft, an improvement is provided for reducing noise, as well as mechanical load on the propeller blade, and includes a construction part situated upstream from the propeller and being exposed to the oncoming air flow prior to reaching the propeller, thus being an obstacle that has a particular contour in a plane transversely to an axis of rotation of the propeller, so that at least the rear edge, as seen in peripheral direction of rotation of the propeller, forms an angle that is not zero in relation to a leading edge of the propeller, when the propeller as a whole is in a horizontal disposition.

Counter-rotating propellers

Abstract: A double reverse revolution propeller apparatus having a front (6) and a rear (7) propeller is disclosed, in which the rear propeller is rotated at higher speeds than the front propeller. In another aspect, when seizure occurs, an inner shaft (8) is disconnected from an engine at an inner shaft connection unit (10) and connected to an outer shaft at an inner and outer shaft connection unit to be driven in the same direction as the outer shaft. In still another aspect, the ratio in absorption horsepower of the front propeller to the rear propeller is set to be substantially equal to the ratio in rotational speed of the front propeller to the rear propeller. In a further aspect, one or both of the front and rear propellers include a variable pitch propeller. In a still further aspect, the front propeller has more blades than the rear propeller.

Controlling propulsor driven by gas turbine engine

Abstract: An integrated control system for coaxial counterrotating aircraft propulsors driven by a common gas turbine engine. The system establishes an engine pressure ratio by control of fuel flow and uses the established pressure ratio to set propulsor speed. Propulsor speed is set by adjustment of blade pitch.

Bladed rotor assemblies and control means therefor

Abstract: A bladed rotor assembly and a control means therefor, which comprises a bladed rotor, a fluid-pressure-operable actuator for effecting a change of blade pitch, a first valve member connect to, and movable with the actuator and a second valve member co-operable with the first valve member, both valve mebmers having fluid passageways therein for supplying fluid to the actuator, and override means being provided to control the position of the second valve member relative to the first valve member, wherein safety means are provided to cause, in the event of failure of the over-ride means, the actuator to effect increased blade pitch

Variable-pitch propellor for water-borne vessels

Abstract: The variable pitch propeller (5) is connected at one, about an axis (9) mounted pivotable guide body (2) and can be lifted by pivoting of the same on the water surface. As a result, one at the propeller hub (11) of the variable pitch propeller (5) arranged with the propeller hub (11) co-rotating adjusting device by means of a handle (15) easily adjustable, whereby a Noticeable fuel saving is achieved by adjusting the pitch of the propeller blades according to the intended procedure.

Large-scale Advanced Prop-fan (LAP) static rotor test report

Abstract: Discussed is Static Rotor Testing of the SR-7L Large Scale Advanced Prop-Fan (LAP). The LAP is an advanced 9 foot diameter, 8 bladed propeller designed and built by Hamilton Standard under contract to the NASA Lewis Research Center. The Prop-Fan employs thin swept blades to provide efficient propulsion at flight speeds up to Mach .85. Static Testing was conducted on a 10,000 HP whirl rig at Wright Patterson Air Force Base. The test objectives were to investigate the Prop-Fan static aerodynamic and structural dynamic performance, determine the blade steady state stressers and deflections and to measure steady and unsteady pressures on the SR-7L blade surface. The measured performance of the LAP correlated well with analytical predictions at blade pitch angles below 30 deg. A stall buffet phenomenon was observed at blade pitch angles above 30 deg. This phenomenon manifested itself by elevated blade vibratory stress levels and lower than expected thrust produced and power absorbed by the Prop-Fan for a given speed and blade angle.

Correlation of helicopter impulsive noise from blade-vortex interaction with rotor mean inflow

Abstract: Data from a test made in the Langley 4 x 7 Meter Tunnel were parametrically studied with respect to the occurrence of blade-vortex interaction (BVI) as a function of tunnel speed and rotor angle of attack Three microphones on the tunnel centerline forward of the model and one microphone forward and 45 degrees to the right provided the data The rotor model was tested with a set of high-twist blades (-10 degrees) and a set of low-twist blades (-5 degrees) over the midspeed range (50 to 80 knots) at angles of attack ranging from -6 degrees (shallow climb) to 10 degrees (steep descent) The data from all four microphones indicated that the most probable time of occurrence of BVI is when the rotor descent is approximately equal to the rotor mean inflow velocity However, some of the data showed no conclusive relationship to the mean inflow velocity

Reversible and self-adjusting propeller device

Abstract: A self-adjusting propeller device having a control blade and a thrust blade connected together in nondiametrical relation and pivotally mounted on a hub for rotation about a hub axis. In response to a change in load on the device, the control blade pivots in relation to the hub axis at generally constant pitch, and, by virtue of the manner in which the pitch and thrust blades are interconnected and disposed on the hub, the thrust blade pivots at a changing pitch so that the device applies a substantially constant torque. Structure is provided for chaning the pitch of the control blade independently of the load from a remote location during operation of the device. The selection of control blade pitch positions provides for transmission of forces in either axial direction and at selected magnitudes including a neutral or non-force-transmitting mode.