Abstract: A static longitudinal stability (SLS) system provides an unobtrusive airspeed hold function that reacts to the pilot control inputs into the flight control system and the measured states of the aircraft to engage and disengage smoothly without any explicit mode selection by the pilot. The SLS engages airspeed hold when the aircraft is close to trimmed, non-accelerating state. This logic allows the pilot to either fly close to a desired airspeed and let SLS engage, or trim the aircraft in an accelerating/decelerating maneuver and just wait for the SLS to capture a speed when longitudinal acceleration is small. The SLS is not dependant on the pilot specifically selecting this mode, but rather engages and disengages in response to flight control system status and how the aircraft is being maneuvered.

Abstract: An integrated fire and flight control system of the type which controls aircraft flight dynamics to referenced values defined by a weapon launch solution to provide optimum aircraft to target orientation, further optimizes the aircraft's angle of attack (AOA) to the target by controlling the aircraft's vertical speed to modify the aircraft's rate of climb or descent as necessary to produce an actual pitch attitude that is within a range of AOA values corresponding to the range of permissive weapon launch vertical speeds recommended by the weapons manufacturer.

Abstract: An integrated fire and flight control (IFFC) system senses the actual engine torque of a rotary wing aircraft in successive real time intervals and compares the sensed interval values with one or more reference maximum torque limits for each of one or more prescribed maximum time intervals and, in the presence of an above limit actual torque for an above limit prescribed time interval, the IFFC automatically reduces the collective axis command.

Abstract: A control system for small unmanned rotorcraft compensates for vehicle pitch control saturation caused by the need for sudden vehicle pitch attitude correction, in turn often caused by wind gusts. The rotorcraft has a pitch-variable rotor system responsive to a vehicle pitch servo command for cyclically controlling rotor pitch and responsive to a collective servo command for collectively controlling rotor pitch. A compensating signal derived from the unlimited vehicle pitch servo command signal is cross-connected to the unlimited collective servo command signal to compensate for pitch control saturation, typically by reducing the magnitude of the resulting collective servo command signal. The compensating signal is derived by passing the unlimited vehicle pitch servo command signal through a dead band which responds as the signal approaches saturation and by preferably also then providing high and low frequency shaping to that signal.

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: A turn coordination inhibit system (150) inhibits a rotary winged aircraft control system from operating in an automatic turn coordination mode when a pilot desired to perform a sideslip maneuver, e.g., a flat turn. When automatic turn coordination is not engaged (132,212,215), e.g., the aircraft is not in a coordinated turn, and either aircraft bank angle (119) exceeds an inhibit threshold magnitude (210) or a pilot yaw command provided by a pilot sidearm controller (155) exceeds a minimum threshold value (243), e.g., the sidearm controller is out of detent in the yaw axis, automatic turn coordination is inhibited (152). Automatic turn coordination remains inhibited until both aircraft bank angle falls below a reset threshold magnitude (230) and the sidearm controller is back in the detent position for the yaw axis (243).

Abstract: A vertical control system for a rotary winged aircraft receives inputs from a displacement collective stick and a sidearm controller. The system provides a set point for the vertical rate of change of the helicopter as a function of a vertical lift command signal from the sidearm controller. The set point is used as a reference for an altitude rate of change feedback path, and an integrated value of the set point is used for an altitude feedback path. The set point is also input to a feedforward control path having an inverse vehicle model to provide a command signal indicative of the command for aircraft collective pitch necessary to achieve the desired set point. Signals from all three paths (i.e., the altitude rate of change feedback path, the altitude feedback path, and the feedforward path) are summed to provide a signal to backdrive the displacement collective which controls main rotor collective pitch.

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: A helicopter flight control system (21) includes a model following control system architecture which automatically provides a coordinating yaw command signal to the helicopter tail rotor to coordinate helicopter flight during a banked turn. The control system processes information from a variety of helicopter sensors (31) in order to provide the coordinating yaw command signal on an output line (72) to the tail rotor (20) of the helicopter.

Abstract: A helicopter flight control system includes an automatic turn coordination system which provides a coordinating yaw command signal to the tail rotor of the helicopter. The system stores on command a trim attitude (e.g., signals indicative of bank angle, lateral ground speed, and lateral acceleration) about which automatic turn coordination is provided, thus providing the pilot with automatic turn coordination about attitudes other than wings level.

Abstract: A helicopter flight control system (21) includes a model following control system architecture which automatically provides a coordinating yaw command signal to the helicopter tail rotor to coordinate helicopter flight during a low speed banked turn. The control system processes information from a variety of helicopter sensors (31) in order to provide the coordinating yaw command signal on an output line (72) to the tail rotor (20) of the helicopter.

Abstract: A helicopter fly-by-wire flight control system (21) includes a model following control system architecture which provides the pilot with maneuvering feel. Maneuvering feel is generated by varying the gain of a rate model (52) in the control system to schedule a constant sidearm controller force per g of load factor currently on the helicopter main rotor. This gain variation works in conjunction with control logic which requires the pilot to apply a nose up pitch command during steep banked turns in order to offset a control system induced downward (pitch) bias of the aircraft nose. The control system induced bias is generated only during steep banked turns, thus allowing the pilot to fly shallow banked coordinated turns without having to apply a nose up pitch command.

Abstract: A helicopter flight control system (21) includes a model following control system architecture which operates in a velocity command mode at low ground speeds. The control system processes information from a variety of helicopter sensors (31) in order to provide a command signal to the main rotor (11) of the helicopter which results in a ground speed which is proportional to the input provided via a sidearm controller (29).

Abstract: A ground-plane-referenced, acceleration signal 2 and Doppler velocity signal 56 are utilized by a complementary filter 6 to provide a complementary velocity signal 8 which is transformed 60 to an inertial coordinate referenced velocity signal 62 utilized in combination with a GPS position signal 56 by a complementary filter 68 to provide a complementary, position error signal 130 that is transformed to a ground-plane-referenced, position error signal 168 and summed with a wind speed signal 196 calculated from the difference between air speed 200 and the aforementioned complementary velocity signal 8 to provide a pitch command signal 202. A similar system is utilized to provide a roll command signal. The system is gated by signals 100, 176 which are determinative of the aircraft meeting predetermined flight conditions 250-262.

Abstract: A helicopter flight control system includes a model following control system architecture to control helicopter response about the yaw axis. The control system processes information from a variety of helicopter sensors in order to provide an output command signal to the tail rotor. Yaw control is accomplished by applying a force on a sidearm controller which provides a yaw axis command signal that is used to schedule a desired yaw rate of change. The lateral acceleration and airspeed signals are used to compute a synthesized yaw rate signal which is compared against the desired yaw rate of change, thus allowing the pilot to control lateral acceleration when he applies force on the sidearm controller.

Abstract: A helicopter flight control system includes a model following control system architecture having provisions to compensate for Euler singularities which occur when the pitch attitude of the helicopter starts to approach ninety degrees. The control system processes information from a variety of helicopter sensors in order to provide the control commands to the helicopter main and tail rotors. The present invention synchronizes a sensed attitude signal, and a desired attitude signal as the pitch attitude of the helicopter approaches ninety degrees to compensate for the Euler singularities.

Abstract: Control law system for the collective axis, as well as pitch and roll axes, of an X-Wing aircraft and for the pneumatic valving controlling circulation control blowing for the rotor. As to the collective axis, the system gives the pilot single-lever direct lift control and insures that maximum cyclic blowing control power is available in transition. Angle-of-attach de-coupling is provided in rotary wing flight, and mechanical collective is used to augment pneumatic roll control when appropriate. Automatic gain variations with airspeed and rotor speed are provided, so a unitary set of control laws works in all three X-Wing flight modes. As to pitch and roll axes, the system produces essentially the same aircraft response regardless of flight mode or condition. Undesirable cross-couplings are compensated for in a manner unnoticeable to the pilot without requiring pilot action, as flight mode or condition is changed.