Abstract: Embodiments are directed to systems and methods for deploying an outboard rotor blade of proprotor pylon to act as an extended lifting surface. Blade control actuators may provide primary rotor flight control as well as providing fold linkage actuation when fold locks are disengaged. During cruise flight, the blade control actuator may provide feathering inputs to the extended rotor blade, wherein the amplitude and frequency of feathering inputs are tuned to mitigate undesirable wing and fuselage dynamic modes thereby enhancing aircraft stability. The deployed rotor blades also improve the total lifting area of the aircraft, which may increase aircraft range and efficiency.

Abstract: A method of fuel tank inerting includes separating process air into nitrogen-enriched air and oxygen-enriched air with an air separation membrane. A vacuum is applied to the air separation membrane to produce a pressure differential across the air separation membrane. The vacuum is manipulated to vary the pressure differential and vary purity of the nitrogen-enriched air.

Abstract: A method for measuring a windspeed vector is described. A true airspeed vector of a flying machine is measured while the machine is in flight using one or more nanowires on the flying machine. Each nanowire is configured to measure a value of local air velocity relative to the flying machine. A velocity of the flying machine relative to the ground is measured while the machine is in flight, and then (a) the true airspeed vector is subtracted from (b) the velocity of the flying machine relative to the ground. Other applications are also described.

Abstract: An upper casing with a hollow shell made of composite materials. The shell was a side wall that extends in elevation from a housing flange to a housing collar, the side wall including at least one cutout. The upper casing includes an internal liner that is inserted inside the shell and that is fastened to an inside face of the shell, the liner comprising a base and a top, together with at least two legs extending in elevation from the base to the top, the liner further comprising at least one equipment support in register with a cutout, each equipment support being for carrying a removable piece of equipment of the upper casing.

Abstract: A wind/water turbine has a basic configuration in which both ends of blades which are in rotational symmetry are fixed to support plates, the blades have vanes, one of the vertical sides of the vanes is attached to a vane rotating shaft, and the free opposite sides each rotate freely in a sector extending as far as the adjacent vane rotating shafts on either side. The vanes are arranged such that when the blades of the wind/water turbine are convex, moving against the water flow/airflow, the vanes are pressed by the water flow/airflow and are opened, thereby reducing the rotational resistance, and when the blades have pivoted further and are concave, the spaces between the vane rotating shafts are closed, the water/air pressure is received over the entire surface of the blade, and thus a pivoting force that is increased corresponding to the reduction in rotation resistance is obtained.

Abstract: An active sensing system for wind turbines is described. The sensing system may include a plurality of ports, a local sensing device and a load mitigation device and may be operably coupled to a control system. The plurality of ports, local sensing device, and load mitigation device may be operably coupled and configured to monitor air pressure on wind turbine blades, determine if proper sensing operation is occurring, and eradicate an obstruction if proper sensing operation is being prevented by the obstruction. Associated methods performing the sensing and eradication of the obstruction including purging and deicing are disclosed. Wind turbines and wind turbine blades with the active sensing system are also described.

Abstract: A system and method for pressure based load measurement are provided. The system and method measure at least one pressure differential on an airfoil and determine at least one aerodynamic load associated with the at least one pressure differential. The determined at least one load is used to modify characteristics of the airfoil to increase efficiency and/or avoid damage. The determined at least one aerodynamic load may be further utilized to balance and/or optimize loads at the airfoil, estimate a load distribution along the airfoil used to derive other metrics about the airfoil, and/or used in a distributed control system to increase efficiency and/or reduce damage to, e.g., one or more wind turbines.

Abstract: A system and method for pressure based load measurement are provided. The system and method measure at least one pressure differential on an airfoil and determine at least one aerodynamic load associated with the at least one pressure differential. The determined at least one load is used to modify characteristics of the airfoil to increase efficiency and/or avoid damage. The determined at least one aerodynamic load may be further utilized to balance and/or optimize loads at the airfoil, estimate a load distribution along the airfoil used to derive other metrics about the airfoil, and/or used in a distributed control system to increase efficiency and/or reduce damage to, e.g., one or more wind turbines.

Abstract: Described embodiments include a wind turbine system. In this embodiment, the system includes a wind turbine including a rotor blade having a controllable feature and attached to a rotor hub drivingly coupled to an electric generator. The controllable feature is configured if activated to decrease a noise generated by the rotor blade and correspondingly to decrease electric power generated by the electric generator. The wind turbine system includes a sensor configured to detect a parameter indicative of present or possible future noise generation state of the rotor blade. The wind turbine system includes a noise manager circuit configured to select a noise mitigation measure responsive to the detected parameter and in compliance with a minimum electric power generation requirement assigned to the wind turbine. The wind turbine system includes a control circuit configured to activate the controllable feature in response to the selected noise mitigation measure.

Abstract: A pitch change apparatus comprises a hydraulic actuator for angular displacement of propellers of the propeller assembly. The hydraulic actuator has a piston and cylinder arrangement which defines fine and coarse fluid chambers. Increasing the volume of the fine chamber at the expense of the coarse chamber results in angular displacement of the propellers to a finer pitch. Increasing the volume of the coarse chamber at the expense of the fine chamber results in angular displacement of the propellers to a coarser pitch. The pitch change apparatus further comprises one or more fine hydraulic lines carrying hydraulic fluid to and from the fine chamber, and a coarse hydraulic line carrying hydraulic fluid to and from the coarse chamber. The apparatus further comprises a pressure-sensing check valve which fluidly isolates the coarse chamber from the coarse hydraulic line if the pressure in the coarse hydraulic line falls below a threshold pressure.

Abstract: With a simple and low-cost structure, it is possible to introduce a sufficient amount of external wind while suppressing power consumption, and thereby, inside a nacelle and a tower are satisfactorily cooled. A wind turbine generator, in which a rotor head generates power by driving a generator installed inside a nacelle and in which the nacelle is installed at a top end of a tower, wherein an introducing vent that takes the external wind into an internal space in the wind turbine generator is provided at a portion of an outer circumference surface of the tower or the nacelle that receives positive pressure due to the external wind; and an exhaust vent that externally exhausts cooling air in the internal space is provided at a portion of an outer circumference surface of the tower or the nacelle that receives the negative pressure due to the external wind.

Abstract: A engine such as a gas turbine engine has a bladed rotor 24 having variable pitch blades 8. In normal operation, the pitch angle of the blades 8 is controlled by a primary pitch control system. A back-up system is provided for controlling the blades 8, for example to displace them to a feathered condition, in the event of failure of the primary pitch control system. The back-up system comprises a pump 32 mounted on the rotor 24, and driven by relative rotation between the rotor 24 and a contra-rotating rotor 23. In response to a failure signal on a conduit 48, the pump delivers hydraulic fluid under pressure to a secondary actuator 30, which acts on the blade 8.

Abstract: The invention provides a wind turbine comprising a rotatable drive train including at least one bearing (3) and a pump (4) for supply of a lubricant to the bearing (3). The wind turbine further comprises a controller for performing closed loop control of the pump (4) to provide an amount of lubricant which varies depending on an actual state of operation.

Abstract: The lengths and/or chords and/or pitches of wind turbine or propeller blades are individually established, so that a first blade can have a length/chord/pitch that is different at a given time to the length/chord/pitch of a second blade to optimize performance and/or to equalize stresses on the system.

Abstract: A pitch driving unit according to the present invention is equipped with hydraulic actuators that change the pitch angles of wind turbine blades; a hydraulic pump that supplies oil to the hydraulic actuators; a high-pressure oil line that guides the oil discharged from the hydraulic pump to the hydraulic actuators; a low-pressure oil line that returns the oil discharged from the hydraulic actuators to the hydraulic pump; and a pressure control unit that stores a surplus amount of the oil and that refills the low-pressure oil line with the oil so as not to generate negative pressure at an oil intake portion of the hydraulic pump, wherein the hydraulic actuators 15, the hydraulic pump, the high-pressure oil line, the low-pressure oil line, and the pressure control unit constitute a closed hydraulic circuit that does not open to the atmosphere, the closed hydraulic circuit being filled with the oil.

Abstract: A measurement system is provided for a wind turbine having a plurality of rotor blades mounted to a spinner at the front of a nacelle and arranged to rotate in a rotor plane. The measurement system includes a measuring device for determining a pressure at a number of pressure measurement points. The pressure measurement points are arranged in front of the rotor plane, an analysis module for generating a control signal on the basis of the pressure measurements, and output means for issuing the control signal to a controller of the wind turbine.

Abstract: The present invention discloses a fan control device for controlling a fan. The fan control device includes a barometer, for measuring an atmospheric pressure of an operating environment of the fan, and a maximum rotating speed setting unit, for setting a maximum operable rotating speed of the fan according to the atmospheric pressure.

Abstract: An upwind wind turbine comprising a tower and a rotor is described. The wind turbine additionally includes a pressure-sensing device supported by the tower at a location within the wake of the rotor. The pressure-sensing device is configured to sense air pressure and provide a signal indicative of the sensed air pressure to a wind turbine controller for use in controlling the rotor of the wind turbine.

Abstract: A hydraulic cylinder is coupled to blades of a wind turbine generator and actuated to change a pitch angle of the blade. A variable displacement hydraulic pump supplies hydraulic oil to the hydraulic cylinder, and a discharge pressure of the pump does not follow a load pressure. When the discharge pressure of the hydraulic pump becomes a set pressure, a pressure control valve is opened to change a discharge amount of the hydraulic pump, and to make the discharge pressure of the hydraulic pump to be a pressure smaller than a cut off pressure. Further, a setting control unit sets the set pressure based on the hydraulic pressure that the hydraulic cylinder requires such that the set pressure becomes a minimum pressure required to change the pitch angle to a predetermined angle by the hydraulic cylinder.

Abstract: A rotor blade of a wind energy installation has a wall forming an outer shell, and at least one pressure measurement device arranged inside the rotor blade. The pressure measurement device includes a hollow body that is closed in a gastight fashion and has at least one pressure-dependent deformable diaphragm. At least one optical strain sensor is non-positively connected to each diaphragm. In a method using the pressure measurement device, the wind force is determined at wind energy installations by an evaluation unit which determines a comparison value indicating the difference between the pressure at the side of the outer shell facing the wind and the pressure at the side of the outer shell averted from the wind. A measured value for the wind force acting on the rotor blade is determined from the comparison value. The method can be used for optimized operation and/or protection of wind energy installations.

Abstract: The present invention includes a rotor blade (20) having a blade body (30) with a leading edge (26) and a trailing edge (28) and opposed first and second surfaces (34, 36) extending there between defining an airfoil shape (32) in cross-section. A passageway (42) extends through the blade body (30) between the first and second surfaces (34, 36). A flexible member (60) is sealed over one end (50) of the passageway (42). Advantageously, the flexible member (60) is passively responsive to changes in a differential pressure between the first and second surfaces (34, 36) to move between a deactivated position (62) and an activated position (64) where the flexible member (60) extends away from the airfoil shape (32) to function as a load mitigation device (40) for the wind turbine rotor blade (20).

Abstract: A system and method for a pressure based load measurement system are provided. The system includes two pressure orifices arranged on a top surface and a bottom surface of an airfoil. The pressure differential between these two points is determined and an estimate of the aerodynamic load generated by the airfoil is determined from a linear correlation between pressure differential and load. The location of the orifices may be optimized using analytical or experimental techniques and a least squares empirical curve fit may be used to fit the data collected.

Abstract: The invention provides a system for capturing moving air and extracting energy from the moving air, the system comprising. A rotor cone is provided having an outer surface, the rotor cone being rotatable about its central axis and having a plurality of veins affixed upon the outer surface of the rotor cone, for receiving a force from the moving air in order to rotate the rotor cone. A shroud surrounds the rotor cone and extends past the narrow end of the cone, opening to an open end having a diameter substantially equal to that of the cone. When moving air enters the shroud at the open end, the moving air compresses within the shroud until it reaches the cone, passes between the cone and the shroud, and impacts the plurality of veins, rotating the cone. A generator within the cone generates electrical energy. In an embodiment, a system is provided for opening the gap between the cone and the shroud under heavy wind to bypass a portion of the moving air.

Abstract: A sensor system monitors deflection of turbine blades of a wind turbine. The system includes a first component configured on the turbine blades. A second component is configured on the tower at a height so as to detect the presence of the first component as the blades rotate past the tower. The second component generates a corresponding measurable parameter or value that is indicative of distance between the blades and tower. The second component is disposed substantially completely around the circumference of the tower so as to detect the first components at any rotational position of the turbine nacelle relative to the tower.

Abstract: A method and system for increasing power production of a wind turbine including a rotor, at least one rotor blade coupled to the rotor, at least one sensor, and a controller communicatively coupled to the sensor. A flow parameter of the rotor blade is detected, and operation of the wind turbine is controlled to reduce a flow separation at the rotor blade based at least partially on the flow parameter of the rotor blade.

Abstract: Gas turbine engine systems involving mechanically alterable vane throat areas are provided. In this regard, a representative vane for a gas turbine engine includes: a leading edge; a trailing edge; a suction side surface extending between the leading edge and the trailing edge; a cavity having an aperture located in the suction side surface; and a barrel located within the cavity and being moveable therein such that movement of the barrel alters an extent to which the barrel protrudes through the aperture.

Abstract: A method of controlling a wind turbine that includes at least one rotor shaft and at least one blade operatively coupled to the rotor shaft includes measuring a first wind turbine operational condition that is representative of a blade deflection value and generating a first operational condition signal based on that first wind turbine operational condition. The wind turbine also includes a drive train including at least one rotor shaft and an electric generator. The method also includes measuring at least one second wind turbine operational condition and generating at least one second operational condition signal. The method further includes changing the blade deflection value by changing the second operational condition.

Abstract: A wind turbine blade assembly includes at least one local load sensor disposed on and/or within a surface of the wind turbine blade and at least one active flow modification device disposed on and/or within a surface of the wind turbine blade and configured to alter the aerodynamics of the wind turbine blade in response to real time local load sensor measurements such that a difference between a current angle of attack and an optimum angle of attack on the wind turbine blade is substantially minimized.

Abstract: An airborne mobile platform generally includes a plurality of rotating rotor blades operating in an airflow that forms a boundary layer on each of the rotor blades. At least one of the rotor blades includes a section that encounters the airflow that includes an unsteady subsonic airflow having at least a varying angle of attack. At least one of the rotor blades also includes one or more vortex generators on the at least one of the rotor blades that generate a vortex that interacts with the boundary layer to at least delay an onset of separation of the boundary layer, to increase a value of an unsteady maximum lift coefficient and to reduce a value of an unsteady pitching moment coefficient for the section.

Abstract: A new wind turbines system extracts dynamic energy from ambient sources and generates power with high efficiency. The less-fluctuated slower-speed turbines have a high-ratio gear reducer to increase the high-power DC generator's speed. An analog/digital voltage converting sampler, a digital signal processor, a power battery charging/discharging regulator, and a power output in steady and continuous states meet its power generation safety and security requirements, which may produce power at about 50% efficiency. A power regulator stabilizes the fluctuations of the incoming power and regularizes its power outputs in steady and continuous states. A high ratio gear reducer (1:100=1:10×10 in two stages) increases its generator's speed and meets power generation requirements.

Abstract: A method and an arrangement for adjusting a pitch of blades being used by a wind-turbine are described. Pressure is measured at a pressure-side and at a suction side of a blade. The measured pressures are used to determine an actual angle-of-attack of a wind acting on the blade. The angle-of-attack is used to adjust the pitch of the blade of the wind-turbine.

Abstract: A wind turbine including a control system and at least one wind turbine blade having a pressure measurement system is disclosed. The pressure measurement system includes a pressure probe that provides a measurement of inflow angle to the control system. The control system adjusts the blade pitch angle of the at least one turbine blade in response to the inflow angle measurement to improve energy capture. The pressure probe is mounted by a probe support structure at a predetermined position from the leading edge of the at least one wind turbine blade.

Abstract: A method and an apparatus for measuring an air flow at an airfoil surface are provided, wherein at least one pressure sensor adapted to detect an air flow associated with a rotor blade surface and a pressure transducer which converts the detected air flow into an electrical signal indicating the air flow are provided. The pressure sensor is arranged within the boundary layer of the air flow at the airfoil surface such that the boundary layer profile may be determined from the electrical signal. The air flow sensor is adapted for rotor blades of a wind turbine to assist in adjusting a pitch angle of the rotor blades.

Abstract: A wind turbine blade, includes a sensor, arranged upstream from a trailing edge of the blade for measuring an airflow characteristic near a surface of the blade; and an actuator, arranged downstream from the sensor, for adjusting the airflow in response to the measured characteristic.

Abstract: A wind turbine having at least a blade comprising a first component (11) having an aerodynamic profile with a leading edge, a trailing edge and suction and pressure sides between the leading edge and the trailing edge, and a second component (13), attached to the trailing edge and/or to the leading edge of the first component (11) in at least a part of the blade, comprising one or several upwards and/or downwards deflectable flaps (15, 15?) that allow changing the flow over the blade, in which the means for deflecting each of said flaps (15, 15?) comprise an actuating force or torque provided by scaling devices (21) connected to a predetermined location (17) in the outer surface of the blade, through a duct (19), so that the changes in the wind pressure at said location (17) can be scaled to said actuating force or torque.

Abstract: The present invention relates to a windmill device rotating by a wind power. More particularly, to efficiently obtain rotating energy irrespective of a wind direction, the present invention is firstly characterized in that assuming that an outermost radius as a distance between the remotest position of each blade from the center of a vertical shaft and the vertical shaft is r1, an innermost radius as a distance between the nearest position of each blade to the vertical shaft and the vertical shaft is r2, and the angle (rad) of an arbitrary position r in an inner peripheral surface of the cross-section of the blade by regarding a line segment for connecting the remotest position from the vertical shaft to the vertical shaft as a reference is t (in this case, 0<=t<=2?/3), the form of the inner peripheral surface in the cross-section of each of the three blades satisfies a following formula: r=(r1?r2)×((t?2?/3)×2)/(2?/3)×2+r2.

Abstract: A system and method for providing pressurised oil during non-feathered in-flight shutdown conditions in a variable-pitch aircraft propeller engine. A secondary pump provides pressurised oil substantially independent of an engine main oil circuit.

Abstract: A fan and a fan blade are provided for allowing airflow through the fan blade in a fan failure condition. The fan blade includes a peripheral member defining an opening. A flexible cover member is attached to the peripheral member for covering the fan blade opening during normal operation of the fan. The flexible cover member is hingeably attached to the peripheral member for movement away from the peripheral member enabling airflow through the fan blade opening in a fan failure condition.

Abstract: A control for changing direction of air flow through a cooling core in response to an external signal and a purge signal includes a logic circuit and a relay assembly. The logic circuit generates a fan control signal based on the external signal, which causes the fan to turn on and operate in a cooling mode and generate an air flow through the cooling core in a first direction, or operate in a neutral mode with reduced or no air flow through the cooling core. The logic circuit also includes at least one timer that internally generates the purge signal, which is then transmitted by the logic circuit to the relay assembly. The purge signal overrides the fan control signal and causes the fan to operate in a purge mode, which causes air flow through the cooling core in a second direction opposite to the first direction.

Abstract: An active control device is disclosed comprising an array of actively controlled oscillating air jets disposed on an aircraft structure. In a preferred embodiment, the device senses parameters associated with incipient unsteady aerodynamic excitation, such as free stream gusts, shed wakes in rotor and turbomachinery flows, or oscillatory motion of trailing edge control surfaces such as ailerons. These parameters are provided as input signals to a processor. Based on the input signals, the processor generates output signals that are used to operate the air jet array in a manner counteractive to the unsteady forcing. The air jet array can be used on numerous aircraft structures, including rotor blades, wings, engine inlets, engine exhausts, blunt surfaces and nozzles.

Abstract: An electronic control device for opening and closing valves in a valve assembly that actuates a variable pitch fan system capable of operating in a plurality of fan blade pitch positions including a temperature switch actuated in response to a temperature condition of the engine, a pressure switch in series with the temperature switch and actuated in response to a pressure condition of the variable pitch fan system, and a time delay relay control in parallel with the temperature switch and the pressure switch for transmitting a timed signal therefrom. The device also includes a first solenoid in series with the pressure switch, a second solenoid in series with the time delay relay control and connected to the first solenoid, and wherein transmission of at least one of the timed signal, the temperature condition signal, and the pressure condition signal opens or closes the valves of the valve assembly of the variable pitch fan system.

Abstract: An air moving apparatus for generating cooling airflow is provided that includes a noise reduction system for reducing noise generated by a fan. The air moving apparatus includes a fan having a rotatable hub and a plurality of blades mounted to the hub for rotating about an axis of rotation to provide pressurized airflow. A sensor is situated on a surface of at least one fan blade for sensing airflow characteristics of the air flowing over the fan blade. An actuator, also situated on the surface of the fan blade, changes the characteristic of the airflow over the fan blade in response to the sensed airflow characteristic.

Abstract: A porous surface on an aircraft structure driven with oscillating positive and negative pressures is used as an active control device for attenuating negative aerodynamic interactions. The porous surfaces can be driven with positive and negative pressures either continuously or when predetermined flight conditions are present. The porous surfaces can be used on rotor blades to reduce BVI noise in descent flight conditions. The porous surfaces can be configured on rotor blades for affecting blade variable twist in accordance with various flight conditions, and can further be incorporated for reducing rotor hub vibrations as well. Porous surfaces placed on aerodynamic surfaces below the rotor blades of a tiltrotor aircraft can attenuate or eliminate download and fountain flow conditions.

Abstract: An apparatus for monitoring the health of a compressor including at least one sensor operatively coupled to measure the dynamic pressure of gases flowing through the compressor, a processing system coupled to at least one sensor, the processor system recording and processing the measurements made by at least one sensor. The apparatus further includes a comparator that compares the sensor measurements with predetermined baseline values, and a real-time controller coupled to the comparator, the controller initiating corrective actions to prevent a compressor surge if the sensor measurements deviate from the predetermined baseline values.

Abstract: The present invention relates to a method for reducing the blade-vortex interaction noise of rotary wings. According to the invention: at least one value &PSgr;o of the azimuth of the blades (1) is determined, for which value said blades shed tip vortices giving rise to a peak intensity of noise; a trailing edge flap (2) is disposed on each blade (1), the former generating an auxiliary vortex (11), parallel to the tip vortex (10) and attached to a blade section (8) lying between the blade section (7) around which the speed circulation is a maximum and the tip section (3) of said blade; and a deflection is applied to each of said flaps (2) such that, for said value &PSgr;o, the speed circulation around said blade section (8) is a specified fraction of the maximum speed circulation.

Abstract: A controlled passive porosity system includes a lifting device for operation in a multi-phase liquid, the lifting device having a low pressure surface with a plurality of holes and a high pressure surface with a plurality of holes. A common plenum is disposed within the lifting device and allows fluid communication between liquid adjacent the high pressure surface and liquid adjacent the low pressure surface. When cavitation occurs adjacent to the low pressure surface, a series of valves associated with the holes allows selective and localized fluid communication between the surfaces. The fluid communication has the effect of raising the pressure of the liquid in the area of cavitation, thereby eliminating the cavitation. In an alternate embodiment, the lifting device includes a first plenum, a second plenum, and an intermediate fluid passage, the fluid passage fluidly connecting the first plenum and the second plenum.

Abstract: A pressure relief device for preventing over pressurization of a propeller hub is disclosed. The pressure relief device is designed to fit within a ball hole opening in the hub arm of the hub. The pressure relief device includes a housing which sealably interfaces with an inner wall of the ball loading hole opening and a diaphragm which sealably interfaces with the housing. The diaphragm is designed to rupture at a design pressure thus venting the hub cavity.

Abstract: Porous surfaces on an aerodynamic structure driven with positive and negative pressures are used in an active control system for attenuating shock waves responsible for high-speed impulsive (HSI) noise. The control system includes an array of apertures in the outer skin of the structure providing fluid communication between the exterior flow stream and an interior volume of the structure. A movable diaphragm within the structure pushes air out of and pulls air in through the apertures under the action of a drive mechanism within the structure, thus creating oscillating air jets. The drive mechanism may be actuated by a controller based on information supplied by a sensor in the leading edge of the aerodynamic structure. The array of apertures may be spaced apart along the outer skin of the aerodynamic structure so as to span a distance of about 15% of the chord length. The oscillating airjets may be provided on multiple surfaces of the aerodynamic structure, including the upper and lower surfaces.

Abstract: A technique for providing a signal representative of blade vortex interaction (BVI) noise for a multi-blade rotorcraft. The fluid (air) pressure at one, two, or more predetermined locations on a rotor blade is measured during at least one predetermined azimuthal segment of blade rotation during operation to provide respective pressure measurements. The pressure measurements are processed to provide a signal for use as a control variable in a control system for the active control of BVI noise. The pressure measurements are made within 10% blade chord length of the blade leading edge and preferably two or more are made between 65% and 95% of blade radial-length. The pressure measurements are filtered and the band of retained frequencies is between 20 and 48 times the rotor rotation frequency. An algorithm operative over a determined blade frequency range optimizes the signal for control use.

Abstract: An active control system for reducing blade-vortex-interaction (BVI) noise generated by a rotor blade. The active control system includes a pressure sensor assembly, a device for changing a lift generated by the rotor blade, and a controller for activating the device upon a detected change in air pressure by the sensor assembly. The sensor assembly is disposed in close proximity to the rotor blade, and is adapted to detect a change in air pressure on a surface of the rotor blade near a leading edge of the rotor blade. The device is adapted to be activated by the controller, to thereby change a lift of the rotor blade. The controller activates the device to change a lift of the rotor blade in order to introduce a compensating pressure onto the surface of the rotor blade. This compensating pressure attenuates the magnitude of the change of air pressure.