Abstract: The actuation system of the present invention is based upon sensing relatively small delta errors over relative short strokes as opposed to absolute travel error.

Abstract: A method and apparatus for managing the trim of an airplane stabilizer whose elevator is controlled by a highly augmented elevator control law is disclosed. The augmented portion of the elevator command ##EQU1## is evaluated(13) to determine if it is above or below a variable threshold whose magnitude is dependent on airspeed. Portions above or below the threshold are integrated (15) to determine if the augmented portion of the elevator command is rapidly or slowly diverging. A stabilizer trim command is rapidly produced if the augmented portion of the elevator command is rapidly diverging and produced more slowly if the augmented portion is slowly diverging. The stabilizer trim command causes the production of a trim up or trim down command (25/27) depending upon whether the stabilizer needs to be moved up or down.

Abstract: A velocity command system is provided with a velocity stabilization mode wherein aircraft flight path referenced velocities are determined with respect to an inertial frame of reference, the flight path referenced velocities are held constant during pilot commanded yaw maneuvers so that the aircraft maintains a fixed inertial referenced flight path regardless of the pointing direction of the aircraft. Velocity control with respect to an inertial frame of reference is accomplished by controlling the aircraft flight path based on aircraft body referenced commanded lateral and longitudinal acceleration and based on aircraft body referenced lateral and longitudinal centrifugal acceleration. Operation in the velocity stabilization mode is provided in response to the manual activation of the velocity stabilization mode by the pilot, provided that the aircraft is already operating in the ground speed mode and the aircraft is not in a coordinated turn.

Abstract: Automatic trim control for a position stick. Strain gauges are mounted with respect to the position stick so as to generate signals proportional to the force manually exerted upon the control stick. The signals from the strain gauges are used to control trim motors which adjust force exerted by springs on the position stick in opposition to the manual force. The signals from the strain gauges are used to control the trim motors so as to reduce the force of the trim springs opposing the manual force. The trim springs are adjusted to reduce the opposition force to a minimum.

Abstract: An automatic piloting device for aerodynes uses at least one digital computer receiving information from a set of sensors, and controlling actuators acting on the flight control surfaces, the computer comprising at least one autonomous computing module having hardware and software resources capable of piloting according to any one of the three piloting axes, the module having a means for becoming specific to a given axis from among the piloting axes, and a connection means for connection to the sensors and actuators corresponding to said given axis. It applies notably to the automatic piloting of a helicopter.

Abstract: An integrated fire and flight control (IFFC) system determines a ballistic firing solution based on the position of targets relative to a helicopter and also based on the type of weapons to be fired. An elevation command is determined based on the required change in helicopter attitude to achieve the ballistic firing solution that, combined with the estimated time required to perform the aim and release of weapons, provides an estimate of deceleration and velocity loss that will occur. A forward acceleration and velocity profile is determined based on the desire to make a symmetrical maneuver sequence involving a nose down acceleration to achieve the acceleration and velocity profile that will be canceled by the subsequent deceleration and velocity loss during the pitch up maneuver to the ballistic firing solution.

Abstract: A control system is provided which prevents a powerful, propeller driven, jet training aircraft from requiring corrective action to throttling and gyroscopic effects when the student wishes to fly the aircraft in coordinated flight. The control system includes a digital memory having stored therein flight test generated data representative of the relationship between the amount of rudder trim required to maintain the aircraft in coordinated flight as a function of aircraft engine torque and airspeed. Sensors are provided to measure aircraft engine torque aircraft altitude aircraft speed, and pitch rate. The measured parameters are coupled to the digital computer. The digital computer combines the parameters provided by the sensors and data read from the memory to produce a composite rudder trim signal which automatically reduces rudder forces induced by throttling and gyroscopic effects produced in response to pilot commanded maneuvers to thereby maintain the aircraft in coordinated flight.

Abstract: An aircraft control system for an unique-trim, model-following system includes a feedforward shaping function that provides quickening of pilot input, and an automatic trim function that accommodates return of the cockpit controller to an unique, centered position during trimmed flight. The basic control law is reconfigured in response to the changing state of landing gear contact to support transitions between ground state and fly state conditions. The state of the landing gear is monitored continually to recognize the occurrence of initial ground contact and whether the aircraft is constrained about a rotational axis due to ground contact. The control is altered progressively as the transition proceeds so that command of the control surface is consistent with the degree of constraint imposed by ground contact.

Abstract: A transient free synchronizer stores an input trim signal value on command, and provides an output signal value which transitions in a smooth, continuous manner, when the synchronizer is commanded to the store the input signal. Synchronizers are typically used to capture desired aircraft attitude, position, or velocity trim points for use in aircraft autopilot and automatic flight control systems.

Abstract: The present invention features a simulator apparatus and method for realistically simulating actual forces at the horizontal stabilizer trim controls of an aircraft. The invention features a closed-loop, microprocessor-based programmable system with reduced mechanical, electromechanical, and/or hydraulic components. The microprocessor computes the required reaction forces using a softward model of the horizontal stabilizer trim system.

Abstract: According to the invention each of the pitch and thrust commands is a linear combination, inter alia, of the trim setting and of the speed setting, and the control provided by the aircraft joystick is pitch rate control. Protection may be provided with respect to trim, angle of incidence, and vertical load factor.

Abstract: There is provided a controller for aiding a pilot to control an airplane's track over the ground. While the airplane is in the air, a lateral control subsystem is provided for automatically holding the aircraft aligned with a desired track angle. Control is initiated when the pilot places the airplane in a wings level condition and centers his roll axis controller (e.g., wheel or stick). An in-air track rate control subsystem is also provided. While the airplane is on the ground, a directional control subsystem is provided which enables the pilot to command track rate or heading rate with rudder pedal inputs. The track/heading rate commands are integrated to generate track/heading angle commands. Feedback control is used to position the rudder and nosewheel steering as required to make the airplane's actual track/heading follow the track/heading commands. Provisions are made to initialize the in-air lateral and on-ground directional control subsystems to provide smooth transitions during takeoff and landing.

Abstract: A controller for apportioning high amplitude and low amplitude control signals between two aircraft control surfaces, such as for example, between an elevator and an associated movable horizontal stabilizer. The signals are separated along a first path and a second path. Signals along the first path are fed to a low pass filter where the low frequency signals are separated and an elevator position error signal is generated. Those signals exceeding a predetermined elevator position error are fed in the form of stabilizer rate signals to a stabilizer position module where a stabilizer positioning signal is generated and then fed to a stabilizer servo system to reposition the horizontal stabilizer. The stabilizer positioning signal is also fed to a multiplier where it is multiplied by a predetermined pitch effectiveness ratio representing the amount of elevator deflection required to achieve the same pitch moment as one degree of stabilizer deflection.

Abstract: This invention relates to a system for controlling an aerodynamic surface mounted mobile on an aircraft so as to be able to pivot freely about a fixed axis and provided with a tab itself articulated on the trailing edge of the aerodynamic surface, the system being such that elastic connecting devices are provided between the tab and the aerodynamic surface and the tab can be directly actuated by the pilot, via a voluntary actuating member and a mechanical linkage. According to the invention, this system comprises: an actuator interposed between the elastic connecting device and the aerodynamic surface; a device for controlling the actuator; and a clutch connecting the structure of the aircraft to the mechanical linkage; and the device for controlling the actuator also controls the clutch, so that the latter is in disengaged position when the actuator is active and in engaged position when the actuator is inactive.

Abstract: An aircraft, such as a helicopter, is trimmed into a desired position by ducing a trimming control signal during the maneuver for the desired positive and adjusting control forces in response to the trimming control signal. The trimming control signal (.delta..sub.T) is produced by comparing a rated or reference signal (R) representing the desired displacement from the force free position of the stick, with a measured signal (.theta.) representing the rotational speed of an aircraft about a given axis. In addition to the trimming operation a stabilization of the position of the aircraft is performed at the moment when the pilot does not touch the control stick. The measured signals thus include information regarding the deviation of the aircraft from the desired position. Thus, a trimming motor automatically maintains the aircraft into the desired attitude.

Abstract: An aircraft automatic trim system is operable during autopilot control to transfer trim from the elevators to the stabilizers. The thresholds for trim transfer are based on the ratio of elevator demand to available elevator control. Trim commands are produced responsive to this ratio exceeding an amplitude and time dependent limit.

Abstract: The control system includes a schedule (54) which plots airspeed versus stabilizer angle for a trim condition. Following a pilot adjustment of the stabilizer angle to establish trim, the schedule (54) plots the trim airspeed to obtain a stabilizer angle value. A change in airspeed from trim is sensed by a sensor (52) and the schedule (54) plots the new airspeed on the same graph to obtain a new stabilizer angle value. The schedule (54) determines a change in stabilizer angle signal in the form of increments of movement of the stabilizer control actuator (28) to return the stabilizer (18) to a trim condition. A schedule (40) in the system also senses any change in the rate of change of altitude from trim and computes from this change a second signal in the form of increments of actuator movement. There is an algebraic summation of these two signals and a stabilizer angle feedback signal to produce a command signal.

Abstract: The steering or control force for operating a steering column in an aircraft, especially in a rotary wing aircraft, is stabilized. The steering column influences through an articulated steering or control linkage the elevator assembly or the rotor blade adjustment, whereby a signal is employed which is dependent on the measured flight speed. It is necessary to signal to the pilot at all times how the steering column must be moved. Such signalling must be definite and free of any disturbing influences and the pilot must receive such signalling through the steering column manual force which is a force reacting to the operation of the steering column. For this purpose a speed dependent signal is supplied to a servomotor. This signal rises with the flight speed at least above a preselectable threshold value. The servomotor in turn controls the tensioning state of a spring which is pivoted at one end to the steering column and at the other end to the displacement member of the servomotor.

Abstract: A heading trim reference system provides beep commands indicative of a desired heading/attitude change to the roll channel of an AFCS as roll commands at slow speed in a conventional manner, and to the yaw channel as yaw commands at cruise speed. At cruise speed, the yaw synchronizing integrator responds to the beep commands and provides an error signal to existing turn coordination logic to turn the aircraft.

Abstract: A fixed-wing aircraft with tandem lifting surfaces has monoplane main wings secured in an intermediate area of the fuselage and a horizontal tail surface with at least one stabilizer plane mounted at the tail of the fuselage. A third supporting surface on the fuselage is in tandem arrangement with the other supporting surfaces. The third supporting surface is a canard surface positioned ahead of the center of gravity of the aircraft.

Abstract: Aircraft attitude along the pitch axis is controlled by inputting a velocity command to a pitch control subsystem that includes a velocity side channel and a gain side channel of a pitch servo amplifier. An output from each channel of the pitch servo amplifier is applied to a pitch servo motor for positioning a primary control surface. The velocity of the pitch servo motor is detected by a velocity detector that generates a velocity feedback signal and control signals for each channel of the pitch servo amplifier. Also responsive to the velocity signal of the detector is a pre-flight test circuit for pre-flight checkout of the pitch control subsystem. In each line from the output of the channels of the pitch servo amplifier is a current detector that is part of a pitch trim control subsystem that responds to the current through the pitch servo motor to generate a trim velocity command signal. This velocity command signal is input to a velocity side channel and a gain side channel of a trim servo amplifier.

Abstract: An automatic flight control system, for an aircraft having a roll attitude retention outer loop actuator (29), a roll stability inner loop actuator (25) and a control stick (26) for positioning control surfaces of the aircraft to control its roll attitude, includes means (54, 55) to provide a roll error signal (56) indicative of the deviation in roll attitude from a desired roll attitude. The roll attitude retention outer loop actuator (29) is controlled by a proportional (61) and integral (62) function of the roll error when force is not applied to the stick, but only as a proportional function when force is applied to the stick (48, 49, 51, 62). The roll stability inner loop actuator is controlled by a washed out (72) proportional (64) function of the roll error signal to provide short-term roll retention at roll attitudes established by the control stick during turns against trim. Sensing force on the stick (51, 95, FIG.

Abstract: An improvement to an aircraft control stick is disclosed. Movement of an aircraft may generate a force which undesirably causes the aircraft pilot to deflect the aircraft's control stick, which thereby results in the aircraft deviating from the desired flight path. The present invention includes a processor-based system which employs an algorithm that generates a signal for causing the control stick to resist such forces. The invention includes a spring and damper connected to the control stick so that the spring constant and damping ratio may be varied.

Abstract: In an aircraft automatic flight control system having a reference parameter synchronizing system (70) operable in response to a trim release switch (44), an initial trim release period (139), on the order of a large fraction of a second (137) causes (217, 218) a relatively slow effect trim reference integrator (208, 211) time constant, for smooth transitions of any error signal, followed by a relatively fast (216) effective reference integrator time constant for close, rapid tracking of the reference signal with the actual aircraft parameter.

Abstract: In an automatic flight control system of the type having automatic stabilizer trim control, the long term, constant altitude cruise trim threshold limits which alter the maximum and minimum pull-in/drop-out deflection of the elevator relative to the stabilizer minimize the steady-state downward deflection of the elevator, thereby reducing unnecessary aerodynamic drag and realizing significant savings in fuel costs.

Abstract: A helicopter pitch axis autopilot system, including airspeed hold at cruise speeds and pitch attitude hold below cruise speeds, includes integrated longitudinal acceleration drift corrected by heavily filtered Pitot static airspeed as a filtered airspeed reference, use of a beeper to nudge the airspeed reference above cruise speeds or the pitch attitude reference below cruise speeds, resynchronizing of airspeed reference, pitch attitude reference, pitch autopilot integrator and stick trim position reference, momentarily in response to airspeed transitions between cruise and sub-cruise speeds or in response to initiation of beeping, and continuously during trim release.

Abstract: A helicopter elevator (12, 13) is driven by an electrical actuator (20) to position the elevator (12, 13) to an optimum angle of incidence for given flight conditions. The actuator (20) is included within a servo loop which responds to a command signal derived from an electronics module (69). Transducers which measure longitudinal cyclic position (40), collective pitch position (41) and air speed (42) generate signals which are summed in a summation unit (43). The output of the summation unit (43) is passed through a signal multiplier (45) which has the gain thereof set inversely proportional to air speed. A trigger unit (56) activates the signal multiplier (45) at an air speed above a preset threshold. An integrator (54) integrates the sum of the outputs of the longitudinal cyclic position transducer (40) and air speed transducer (42) to compensate for different center of gravity aircraft loadings.

Abstract: An automatic pitch trim system responds to the output of a torque detector (34) to provide an input signal to a gain normalization circuit (36). A limiter (38) responds to the gain normalization circuit (36) to produce a limited authority trim signal to a summing amplifier (48). Also connected to the normalization circuit (36) is a window generator (42) that responds to the input signal to activate a time delay (46). The time delay (46) generates a control signal to a signal gate (40) having an input connected to the normalization circuit (36). Under the control of the time delay (46), the output of the mormalization circuit (36) is gated through to the summing amplifier (48) to be combined with the output of the limiter (38) into a signal that is applied to a trim servo amplifier (50). The servo amplifier (50) generates an energizing voltage for driving a trim servo motor (44) coupled to trim tabs (52).

Abstract: A helicopter having an automatic flight control system including an inner, stability loop is rendered less sensitive to short-term, inadvertent pilot inputs by applying a washed-out derivative of a stick position signal to the inner stability loop in a sense to countermand the pilot action. Using a washed-out signal countermands only short-term rapid stick motions, which may be induced by the pilot actively, but inadvertently, or inactively due to coupling between the pilot or the stick and motion of the fuselage, while permitting purposeful, long-term stick positions to have the full, intended effect.

Abstract: The present steering mechanism, especially for an aircraft includes a manly operable steering member and an automatic steering system. A difference signal formed from a pilot input and trim signal and from a gyro feedback signal is supplied to a force control and damping circuit twice, once directly and once through an authority limit circuit. The output of the authority limit circuit is also supplied to the motors forming part of the automatic steering system. The force control and damping circuit also receives further input signal or signals representing steering information. The output of the force control and damping circuit is connected to the feel unit of the steering system, whereby an immediate manual control by the pilot is effective, however limited against an excessive control or so-called manual over control.

Abstract: An engine auto throttle control system is disclosed wherein the stability of the high gain control loop is provided by means of complemented EPR feedback. Furthermore, the multi-engine auto throttle control system of this invention generates a stable engine thrust trim command by means of a voter mechanism coupled to the respective engines EPR signals for providing a unique commanded EPR signal and by means of EPR error feedback means coupled to the commanded EPR signal for providing respective actuator signals for each of the respective engine throttle controls for trimming the engines to the same EPR value. In addition, engine overboost protection is provided to each engine individually such that all engines are controlled to a reference maximum limit.

Abstract: The yaw channel of a helicopter, which includes a yaw servo having a yaw trim valve operable to automatically hold heading, and at cruise speeds alternatively operable to provide controlled yaw for coordinated turns, which is normally disengaged by switches located on the pedals, is selectively allowed to remain engaged at cruise speeds so that if the pilot induces commands in yaw by means of the pedals, the pedal linkage must be forced against the position of the trim piston established by the heading hold or coordinated turn input commands to the yaw trim valve, thereby giving the pilot pedal force feel as a consequence of the resilient connection to the trim piston, which provides an indication to the pilot of the amount of side slip he is creating, thereby to avoid destructive overloading of the tail rotor.

Abstract: A control augmentation system for stabilization and control of flight vehes, wherein control of vehicle angular velocities in proportion to control input is effected, and where stabilization of the corresponding vehicle attitude is also effected. The system consists of both feedforward and feedback signal paths. The feedback paths provide augmentation of the vehicle's inherent stability. The feedforward paths augment the controllability factors available to the pilot. The control augmentation system is a solution to hingeless rotor control problems.

Abstract: An aircraft flap sensing and control circuit for sensing and controlling the position of the flaps and for sensing and comparing the instantaneous movement and position of the flaps mounted on opposite wings of the aircraft.

Abstract: A bias actuator, such as an extensible link, in the longitudinal cyclic pitch channel of a helicopter is provided with inputs as a function of airspeed multiplied inversely with collective pitch, and as a function of the rate of change of collective pitch stick position, so as to enforce positive angle of attack and speed stability and positive static pitch trim gradient and to decouple collective pitch from the longitudinal cyclic pitch channel at cruise airspeeds, the invention compensates, inter alia, adverse control effects of tail stabilizer surfaces at cruise speeds. A pair of indicators display bias commands and actual bias responses.

Abstract: A flight control system utilizing a limited authority stability augmentation system having a long term attitude and/or path control input to enhance the automatic flight capability of the stability augmentation system. A position sensor coupled with the limited authority stability augmentation actuator provides an indication to the human pilot via a suitable indicator when the actuator is near or at the limit of its authority thereby permitting the human pilot to effect manual trim, thus recentering the actuator.

Abstract: In a hydraulic actuator such as those used in multiple degree freedom motion bases for aircraft simulators, a secondary force sensitive hydraulic servo loop is added in parallel to the primary position feedback servo loop with the secondary loop having a servo valve possessing substantially greater band pass and less capacity than the main valve used in the first servo loop. Force feedback from the control actuator is applied degeneratively to the smaller servo valve, thereby reducing noise and jitter caused by responses of the system outside the response of the primary servo loop. The response of the main servo loop which control the position of the actuator is low pass and restricts response to the full desired band pass of operational frequencies. The secondary loop is high pass and is shaped to prevent degeneration of operational frequencies while providing optimum gain and phase for the degeneration of the unwanted high frequency portion of the band wherein noise and jitter reside.

Abstract: In the cyclic pitch stick controls of a helicopter of the type in which feel is provided to the pilot by inducing a force which is proportional but opposite to the motion of the cyclic stick from an adjustable trim position, null offset errors which may be due, inter alia, to temperature variation of the hydraulic fluid in the system, are periodically overcome by means of sensing the pressure differential across the force augmentation hydraulic servo actuator at times when the differential pressure thereacross should be nearly zero, during trim release with small stick motion, and providing a countermanding bias in response thereto; the pressure differential is measured by a differential pressure transducer having a full scale which is only sufficient to measure the expected null errors, which may be about an order of magnitude lower than the full scale, operative pressure differentials which may occur.

Abstract: A take-off and landing control device for automatic retraction of flaps upon stowing landing gear and upon attaining a predetermined airspeed and of indicating distance from brake release during take-off, and for an automatic decelerating approach with flaps extending as a function of distance from touchdown with automatic throttle cutback and automatic stabilizer trim in response to flap location maintaining an essentially constant angle of attack.

Abstract: The gain of a stability augmentation system for an aircraft, particularly a helicopter, is automatically varied in accordance with the gross weight and deviations of the center of gravity of the aircraft. Gross weight and center of gravity are identified from in-flight measurements of collective and cyclic pitch stick position and airspeed. The gain of the stability augmentation system will not be changed during periods when the aircraft is being maneuvered.

Abstract: A system for generating an optimum vertical speed command and controlling the aircraft to this command by allowing the aircraft to assume an optimum trimmed condition for the thrust energy available which system utilizes the aircraft autopilot system.

Abstract: A flap compensation system is provided which reduces the pilot applied force required to hold the pitch attitude of an aircraft within specified limits upon pilot operation of the aircraft flaps by automatically displacing the horizontal stabilizer of the craft as a function of flap displacement.

Abstract: The automatic heading retention mode of operation of an automatic flight control system for a rotary wing aircraft is discontinued and reestablished through the use of a logic circuitry responsive to the yaw rate, bank angle and airspeed of the aircraft and to the force applied to the cyclic pitch control member by the pilot. The logic circuitry provides for the isolation of information commensurate with left and right turns and summation of the yaw rate and bank angle in each direction to determine if automatic disengagement of the heading hold is warranted.