Abstract: Systems and methods for tracing aircraft vortices. One method includes directing a tracer from a first aircraft into a vortical flow generated by the first aircraft. The method can further include detecting a characteristic corresponding to the presence of the tracer directed into the vortical flow. Based at least in part on the detected characteristic, the method can include directing the flight of the first aircraft, or a second aircraft following the first aircraft, or both.

Abstract: The present disclosure relates to methods of calculating and flying continuous descent approaches to an airport or the like, and to aircraft navigation systems for implementing these methods. The present disclosure resides in the recognition that greater predictability in arrival times may be achieved by flying continuous descent approaches by maintaining a constant aerodynamic flight path angle.

Abstract: The invention relates to a method of automatic navigation assistance for an aircraft. A capture zone being a zone in which the aircraft can capture a predetermined vertical profile segment by applying a transition between the guidance submode which the aircraft is in and the guidance submode adapted to the following of the vertical profile segment to be captured, it comprises the step consisting in determining the width of the capture zone as a function of the height h of the vertical profile to be captured and of the speed v which the aircraft has when plumb with this height when the aircraft is not on the profile or at this height when the aircraft is on the profile.

Abstract: An aircraft piloting method and device for picking up a vertical profile of a flight plan. The device (1) combines a piloting means (7) enabling a pilot to control the start of the picking-up of a vertical profile, and an automatic piloting means (3) for automatically ending this picking-up, and for following the vertical profile.

Abstract: An aircraft cabin pressure control system implements control logic that significantly reduces potentially uncomfortable pressure bumps that can occur during aircraft take-off rotation both with and without cabin pressuring fluid flowing into the aircraft cabin. The control logic implemented by the cabin pressure control system, among other things, determines whether the cabin pressurizing fluid is flowing into the aircraft cabin. If the cabin pressurizing fluid is flowing into the aircraft cabin, aircraft cabin altitude is controlled to at least a first predetermined minimum altitude value below the take-off altitude. If the cabin pressurizing fluid is not flowing into the aircraft cabin, aircraft cabin altitude is controlled to at least a second predetermined minimum altitude value above the take-off altitude.

Abstract: A method and computer program product for determining the roll rate gyro bias of an attitude and heading reference system from true air speed, heading rate and body accelerations using centripetal force equations.

Abstract: A low-altitude flight guidance system for an aircraft including a warning generator that generates a warning based upon a predicted position. The system further including a first sensor system having a terrain database and a calculation module that determines a current position of the aircraft with respect to terrain stored in the terrain database and that determines a reference altitude hDB of the terrain at the current position. The system further includes a second sensor system and a module that determines a predetermined flight altitude difference ?hF at the predicted position and terrain data in a region U of the predicted position. Moreover, the system includes an altitude prediction module that predicts an altitude and forwards the predicted altitude to the warning generator. The warning is based upon the aircraft reaching, approaching, or exceeding a warning altitude limit, and the altitude prediction module determination for the predicted position is based upon a prediction set point.

Abstract: A spatial data search method, system and apparatus for identifying particular data of significance around a reference vector through the spatial data. The method involves determining a reference vector within a spatial region for which spatial data exists, loading a portion of the spatial data including the data around the reference vector into a memory buffer, and searching the spatial data in a prioritized order. The method, system and apparatus have particular utility in searching geographic data for a terrain awareness and warning system (“TAWS”) and display in an aircraft. Embodiments of the present invention provide advantages over existing sequential and radial search methods, significantly reducing the processing and calculations required and providing faster alerts to pilots.

Abstract: An unmanned helicopter includes an altitude control device for giving a command of a collective pitch blade angle based on an altitude change rate command, etc., and performing altitude control of an airframe and takeoff device, upon reception of a takeoff start command from the ground, for causing the airframe to take off and climbing the airframe to a first altitude while increasing the collective pitch blade angle without performing the altitude control of the altitude control device and then causing the altitude control device to start the altitude control. The unmanned helicopter further includes descending device for causing the airframe to descend to a second altitude while changing descent rate command of the altitude control device and giving a descent rate command smaller than the descent rate command to the second altitude to the altitude control device for causing the airframe to descend from the second altitude to the ground.

Abstract: An aircraft system for reducing the airspeed of an aircraft as it passes through a preselected altitude includes an automatic throttle system including a computer, a device for inputting a preselected altitude and a preselected airspeed into the computer. An altimeter provides the current altitude of the aircraft and an aircraft instrument provides the current air speed and the vertical speed of the aircraft. The computer in response to the current altitude and vertical speed of the aircraft generates a signal to retard the throttles when the current altitude, the current air speed of the aircraft is equal to 2 times the vertical speed plus a preselected altitude.

Abstract: A method for automating a landing maneuver for an aircraft, comprising the steps of generating an approach profile comprising an initial approach fix (IAF), a flight path, a landing decision point, a balked landing route, a pre-landing point, and a landing point, engaging an automated approach system to access the approach profile, receiving periodic position data of the aircraft, comparing the position data to the approach profile to compute a plurality of deviations each time the position data is received, outputting the plurality of deviations to a display, converting the plurality of deviations into a plurality of control commands, and maneuvering the aircraft in response to the control commands along the flight path.

Abstract: An airborne glide slope tracking system includes a radio altimeter for producing a signal indicative of the instantaneous altitude of the aircraft and a glide slope error indicator for producing a signal indicative of the angular deviation from glide slope. The two signals are multiplied to produce a glide slope error signal in feet and fed to a summing device directly and through a lead filter to generate a signal for a throttle servo to increase or decrease the thrust of the aircraft. A longitudinal accelerometer signal is then added to a signal indicative of a difference between an aircraft's reference angle of attack and actual angle of attack to produce a signal to a pitch command to provide an angle which will be sustained by the power of the aircraft.

Abstract: An emergency control system permits an aircraft to recover from a catastrophic loss of cabin pressure even if the pilot becomes incapacitated before he is able to activate an emergency oxygen system. An autopilot system is programmed for rapid descent, in response to a cabin depressurization condition detected by an air pressure sensor, to a flight level where there is sufficient oxygen in the atmosphere to sustain full consciousness. When in the rapid descent mode, the autopilot cuts engine power to idle, reduces the angle of attack, maximizes parasitic drag, and initiates a maximum descent rate without exceeding the aircraft's design limitations. As the aircraft approaches a lower altitude capable of sustaining full human consciousness, the autopilot system increases the angle of attack, reduces parasitic drag, and increases engine power, thereby causing the aircraft to fly level at the lower altitude until the pilot reasserts control of the aircraft.

Abstract: A ground proximity warning system, method and computer program product are provided that controllably alter the base width of the alert envelope in order to accommodate uncertainties associated with the current position of the aircraft. In one embodiment, the ground proximity warning system, method and computer program product controllably alter the base width of the alert envelope depending upon an error value, i.e., an uncertainty, associated with the current position of the aircraft. Since the error value associated with the current position of the aircraft is largely dependent upon the type of navigation equipment onboard the aircraft, the ground proximity warning system, method and computer program product of another embodiment controllably alter the base width of the alert envelope depending upon the type of navigation equipment that provides the current position of the aircraft.

Abstract: A method, an apparatus and a computer program product are provided for accurately determining the vertical speed of an aircraft in a manner independent of signals provided by an air data computer, an inertial reference system and an inertial navigation system. Initially, a first vertical velocity of the aircraft is determined based upon a pressure altitude value associated with the aircraft. A second vertical velocity of the aircraft is also obtained from a GPS receiver carried by the aircraft. The first and second vertical velocities are then combined to determine the vertical speed of the aircraft. In this regard, the first and second vertical velocities are combined by complimentarily filtering the first and second vertical velocities. More particularly, the first vertical velocity is typically low pass filtered to remove high frequency noise that is attributable to the relatively low resolution of the first vertical velocity value.

Abstract: A method of changing a preselect altitude value includes receiving an input from a pilot. In response, the preselect altitude value is changed by a first amount from a current preselect altitude value toward a minimum altitude value. The first amount that the preselect altitude value is changed by is dependent upon a proximity of the current preselect altitude value to the minimum altitude value such that if a difference between the current preselect altitude value and the minimum altitude value is greater than a first predetermined interval, the first amount is equal to the first predetermined interval. If the difference between the current preselect altitude value and the minimum altitude value is less than the first predetermined interval, then the first amount is less than the first interval, for example resulting in the preselect altitude value being set directly to the minimum altitude value.

Abstract: An arithmetic processing method and system in a wide velocity range flight velocity vector measurement system using a square truncated pyramid-shape five-hole Pitot probe. Approximation equations that determine attack angle &agr; and sideslip angle &bgr; in the form of third-order equations concerning attack angle pressure coefficient C&agr; and sideslip angle pressure coefficient C&bgr;, which are known numbers, are expressed in the form of a polynomial equation concerning Mach number M, where the coefficients are obtained from a lookup table.

Abstract: A method, an apparatus and a computer program product are provided for accurately determining the vertical speed of an aircraft in a manner independent of signals provided by an air data computer, an inertial reference system and an inertial navigation system. Initially, a first vertical velocity of the aircraft is determined based upon a pressure altitude value associated with the aircraft. A second vertical velocity of the aircraft is also obtained from a GPS receiver carried by the aircraft. The first and second vertical velocities are then combined to determine the vertical speed of the aircraft. In this regard, the first and second vertical velocities are combined by complimentarily filtering the first and second vertical velocities. More particularly, the first vertical velocity is typically low pass filtered to remove high frequency noise that is attributable to the relatively low resolution of the first vertical velocity value.

Abstract: An aircraft guidance system uses radar imaging to verify airport and runway location and provide navigation updates. The system is applicable to flight operations in low visibility conditions.

Abstract: An improvement to a method of automatic flight using a flight management system is provided. The flight management system includes a lateral navigation (LNAV) control mode in which the flight management system provides roll commands via a flight director system to the pilot during manual flight or to an autopilot during autoflight to effectuate lateral flight guidance. The improvement includes evaluating the energy state of the airplane during the LNAV control mode, calculating a Thrust Based Roll Limit (TBRL), and providing an appropriately limited bank angle command signal via the flight director system for use by the pilot during manual flight or to the autopilot during autoflight while flying in a thrust-limited condition. The TBRL is calculated as a function of the energy state of the airplane. The use of the TBRL to limit the bank angle command signal avoids an uncommanded change in altitude and/or airspeed.

Abstract: A flight warning system comprises an outside temperature probe for sensing outside temperature, a gyroscope for sensing aircraft bank angle, a static transducer for sensing static pressure, and a dynamic pressure sensor for receiving total pressure from a pitot tube. A computer is responsive to the gyroscope, static transducer, outside temperature probe and dynamic pressure sensor calculates whether the aircraft is entering a stall condition by comparing the aircraft's bank angle with the stall bank angle. The computer can also calculate whether sufficient altitude exists for the aircraft to safely return to a field after a power failure. An output device can also be provided for indicating the existence of said sufficient altitude, and a stall indicator can be provided for indicating whether the aircraft is entering a stall condition. A method for determining the existence of a stall condition with the aircraft is also disclosed.

Abstract: The invention relates to processes for aiding aerial navigation. According to the invention, there is proposed a process for aiding aerial navigation, using a flight management system (FMS) which carriers out a dialogue with the pilot by means of several interfaces which include at least one display screen. The flight management system displays on the screen a time-graduated abscissa axis, an altitude-graduated ordinate axis, and, in this system of axes, a plot representing a theoretical path of an aircraft. The flight management system scrolls the time axis and optionally the altitude axis in such a way that the origin of the axes at the instant of display represents, along the abscissa, the time at the instant of display and along the ordinate the altitude of the aircraft at this instant. The pilot thus obtains a better assessment of the time management of the flight.

Abstract: A method of automatically controlling an aircraft to avoid a vertical zone includes several steps. The aircraft first acquires limits of the zone to be avoided. The zone is modeled by a cylindrical volume which is limited by a horizontal contour with upper and lower altitudes of the zone. The cylindrical volume associated with a scheduled route of the aircraft is located and points of entry and exit in the cylindrical volume are determined. A new flight altitude is calculated in order to avoid the zone. A point of change of altitude is calculated to reach an avoidance altitude. The new flight altitude is updated and the point of change of altitude is input into an automatic pilot.

Abstract: A positioning and ground proximity warning method for vehicle includes the steps of outputting global positioning system signals to an integrated positioning/ground proximity warning system processor; outputting an inertial navigation solution to an integrated positioning/ground proximity warning processor; measuring air pressure, and computing barometric measurements which is output to the integrated positioning/ground proximity warning processor; measuring time delay between transmission and reception a radio signal from a terrain surface, and computing radio altitude measurement which is output to the integrated positioning/ground proximity warning processor; accessing a terrain database for obtaining current vehicle position and surrounding terrain height data which is output to the integrated positioning/ground proximity warning processor; and receiving the position, velocity and time information or said pseudorange and delta range measurements of said global positioning system, the inertial navigation s

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: The present invention relates to a method and a device for guiding an aircraft (A) according to a prescribed vertical flight path (T).According to the invention:the vertical distance he between said aircraft (A) and said flight path (T) is determined;the difference ve between the actual vertical velocity (Vz) of the aircraft (A) and the vertical velocity (Vzth) which it would have on the flight path (T) is determined;a vertical acceleration variation Anz is calculated:.DELTA.nz=((k1.(he-hc))+(ve-vc)).k2k1 and k2 being characteristic coefficients, hc and vc being precontrol terms, and k1.(he-hc) being restricted; andsaid restricted variation Anz is applied to the aircraft.

Abstract: Method and apparatus for measuring the alertness level of the flight crew of an aircraft and raising it when necessary. The system also detects departures from the planned flight profile and provides aural warning.

Abstract: An automatic device for maintaining an aircraft at an authorized speed compatible with the technical capabilities of the aircraft includes:a system for comparing the effective speed of the aircraft with reference speeds defined in accordance with the technical capabilities of the aircraft,a system for calculating, on the basis of such comparison, modified control values to align the effective speed with these reference speeds, anda system for imposing one of these calculated values on the aircraft, if this is necessary to maintain the aircraft at an authorized speed.

Abstract: A vertical performance limit compensator is provided for a rotary wing aircraft. The compensator modifies a vertical velocity command signal for the aircraft's autopilot. The vertical velocity command signal represents a desired vertical velocity for the aircraft, and results in an associated engine power demand. Existing engine power remaining beyond that required for level flight is excess engine power. An engine performance signal is provided as an indication of an engine power demand that exceeds the excess engine power. A compensated vertical velocity command signal having a magnitude lower than the vertical velocity command signal is provided in response to the vertical velocity command signal and the presence of the engine performance signal.

Abstract: A synchrophaser for a multi-engine, propeller-driven aircraft including a filter that automatically compensates for misalignment of blade position sensor tabs through derivation and application of a correlation coefficient. The correlation coefficient is calculated in a self-adjustment derivation, utilizing a dynamic tolerance band, providing increased accuracy in propeller speed determination. The correlation coefficient brings about an apparent uniform distribution of blade position sensors, as seen by the synchrophaser, thus eliminating a primary source of cyclic propeller speed disturbances. The correlative filer accomplishes its task without the phase shifting normally encountered in other digital filtering technique.

Abstract: Aircraft input signals of selected altitude (h.sub.s), selected vertical speed (h.sub.s), current altitude (h), current vertical speed (h), current pitch attitude (.theta.), current normal acceleration (N.sub.z) and current pitch rate (Q) are processed to produce an elevator command (.delta..sub.e) that will result in a smooth vertical transition of the aircraft for various autopilot vertical maneuvers, including altitude capture and hold, glideslope capture and hold, and flare control.

Abstract: A torque loop decoupler decouples a torque loop from a speed loop to allow only the speed loop to react to small, rapid changes in engine speed. The torque loop decoupler calculates a compensation signal and adds the compensation signal to a control signal of the torque control loop. The compensation signal keeps the control signal constant during small, rapid changes in engine speed. The compensation signal is calculated as the partial derivative of turbine torque with respect to changes in engine speed multiplied by a signal indicative of small, rapid changes in engine speed.

Abstract: An aircraft landing information system is disclosed which provides to the aircraft pilot information regarding the actual and preferred sink rate of the aircraft, the distance between the landing gear wheels and the runway, and deviation of the actual sink rate from the preferred sink rate. An altitude determining sensor is provided on the aircraft and the information transmitted therefrom is fed into a microprocessor or like system which then presents the relevant data to the pilot in an audio and/or visual format to allow the pilot to touch down at the preferred sink rate.

Abstract: Method and apparatus for measuring the alertness level of the flight crew of an aircraft and raising it when necessary. The system also detects departures from the planned flight profile and provides aural warning.

Abstract: Aircraft/engine performance is determined by the method of the present invention, wherein the performance characteristics are defined by learned performance parameters. The method includes the steps of learning the performance parameters of the aircraft/engine combination, for a given flight, using previously learned performance parameters and current observations. Then, based on the performance parameters learned from the learning step, a prediction is made of the performance of the aircraft/engine combination for subsequent flights.

Abstract: Apparatus and an associated method are described for an aircraft for providing an auto-changeover procedure from a calibrated airspeed control parameter to a Mach number control parameter when the aircraft is ascending; and, from a Mach number control parameter to a calibrated airspeed parameter when the aircraft is descending. The auto-changeover procedure is responsive to application of preselected calibrated airspeed and Mach number parameters. The data processing unit of the aircraft provides a continually updated prediction of the target parameter that would result should the aircraft execute the auto-changeover under the currently existing conditions. When the predicted value and the preselected value are equal, the changeover procedure is invoked, reducing the transients resulting from overshoot of the target parameter value. Provision is made for the circumstance wherein the changeover is determined by an altitude rather than a target parameter.

Abstract: A warning system for aircraft compares the rate of descent of the aircraft with its altitude above ground after take-off, and generates warning if the aircraft is experiencing an excessive descent condition for the radio altitude at which the aircraft is flying. The position of the landing gear, the speed of the aircraft and the engine power are mointored to enable the system only during the take-off or missed approach phases of operation in order to minimize false warnings during other phases. The relationship between radio altitude and descent rate required to generate a warning is optimized for small, high performance aircraft such as fighter or attack aircraft.

Abstract: Altitude rate commands are generated and fed to an aircraft autopilot to cause the aircraft to transition to a non-level flight path which corresponds to a portion of a calculated flight path profile stored in a flight management computer. When capture of the non-level path is initiated, altitude rate commands are generated in accordance with the equation h.sub.cmd =h.sub.path +k.sub.h .DELTA.h where h.sub.path is the altitude rate of the non-level segment, .DELTA.h is an altitude difference between current aircraft altitude and an altitude point on the non-level segment, and k.sub.h is an altitude error gain which is a nonlinear inverse function of altitude rate error, .DELTA.h, and which is calcuated in accordance with the equation k.sub.h =k.sub.1 -k.sub.2 .vertline..DELTA.h.vertline. where k.sub.1 and k.sub.2 are predetermined constants.

Abstract: A flight control system combines airspeed with normal acceleration to produce a feedback signal and combines the feedback signal with a feedforward signal consisting of a pilot command signal to produce a differential acceleration signal which is used to control elevator control surface of an aircraft to provide enhanced pitch stability.

Abstract: A warning system for rotary wing aircraft compares the accumulated altitude loss after take-off of the aircraft with its altitude above ground, and generates a warning if the altitude loss is excessive for the altitude above ground at which the aircraft is flying. The position of the landing gear, the speed of the aircraft and its altitude enable the system only during the take-off and missed approach phases of operation in order to minimize nuisance warnings during other phases. The relationship between radio altitude and altitude loss required to generate a warning is optimized for rotary wing aircaft such as helicopters.

Abstract: A method and device are provided for assisting in height holding in air navigation, consisting, for any point (M) of the image of the landscape flown over by the aircraft (A), located by its angle of elevation (.theta.-p) with respect to the speed vector V of the aircraft, and situated in a zone between a lower elevational limit (.theta..sub.1 -p) and an upper elevational limit (.theta..sub.2 -p), in the trajectory of the aircraft, in detecting a possible deviation between the angular speed .OMEGA. of movement of this point with respect to the aircraft, depending on the height (h,H) of subsequent crossing of this point by the aircraft, for identical piloting conditions, and an angular reference speed of movement (.OMEGA..sub.o) corresponding to a reference height (h.sub.o,H.sub.o) of subsequent crossing by the aircraft of a point having the same elevation (.theta.

Abstract: There is disclosed a system and technique which enables an aircraft (helicopter or VTOL) to be more easily controlled for maintaining precise position or velocity in a hover condition. The system includes operational logic and decision making circuitry which reduces pilot workload by sensing pilot intent based upon the control stick movement and mode selection of the aircraft. The system will automatically hold a given hover position, automatically hold a given hover velocity (ground speed), or allow the aircraft to be manually maneuvered to a new desired hover position or velocity. The system also enables the aircraft to either hold a new velocity or return to a previous velocity. This is all controlled through the automatic flight control system and by sensing the force or displacement of a pilot's control stick in the aircraft.

Abstract: An apparatus for providing asymmetrical torque-switching for an aircraft autopilot. The invention provides an increased amount of available pitch servo torque at high altitude. The direction of pitch of the aircraft is sensed. An increased amount of torque is provided for the pitch-up direction thereby providing more positive control of the aircraft.

Abstract: Deceleration control apparatus for an aircraft having an automatic altitude capture and hold system and an airspeed hold system, both systems controlled by controlling pitch attitude wherein during a descent from a higher altitude under airspeed-on-pitch control with throttle set at idle thrust, and at some existing negative altitude rate, a slower speed is commanded, a synthetic altitude based on the existing descent rate is computed and the attitude capture and hold system operation is switched into control in place of the airspeed on pitch control to cause the aircraft to flare toward the synthetic altitude. The resultant loss of airspeed, i.e., craft deceleration, during the altitude capture flare is monitored and when the commanded airspeed reduction is achieved, the airspeed-on-pitch control is resumed to thereby hold the commanded lower airspeed.

Abstract: An improved flight control system for initiating and thereafter controlling the automatic capture of a preselected altitude is described. At any point in the flight and in any autopilot pitch submode, the remaining time before an altitude capture is to commence is computed and used as a limiting signal such that the aircraft is precisely aligned with the commanded capture flight path when the capture maneuver commences thereby obviating mode to mode transients. The aircraft's altitude rate is continuously monitored during the capture maneuver and the flight path command is automatically altered between asymptotic and circular paths to assure that the acceleration normal to the flight path will not exceed a predetermined value while at the same time allowing a timely altitude capture.

Abstract: During a transition of a VTOL aircraft such as a helicopter, from one altitude held without its ground effect zone to another to be held within its ground effect zone, or vice versa, a collective stick position synchronizer which can memorize the proper trim condition at the previous altitude in conjunction with the stick force sensor out-of-detent logic and a low vertical speed sensor, together constituting a ground effect zone detector, is used to drive the collective stick trim actuator in a direction which relieves any force being exerted by the pilot in order to maintain the new commanded altitude.

Abstract: An aircraft speed control system for use with an automatic throttle position control system and automatic flight control system permits capturing and maintaining a commanded airspeed during the capturing of a desired altitude from either climbing or descending flight. The system manipulates the throttles at a variable rate dependent on the difference between the actual thrust of the aircraft and the desired cruising thrust at the selected airspeed and inversely proportional to the actual altitude rate. A signal derived from thrust error and altitude rate signals is utilized to generate a limiter control signal which is combined with an engine pressure ratio signal to generate a drive signal for urging the aircraft to capture precisely the commanded airspeed.

Abstract: A torque limiting altitude hold system for a helicopter engages torque limiting (56, 203) when excessive torque is anticipated (138, 202) as determined by the summation of present torque and torque rate times a reference value (126, 194) exceeds maximum torque with torque limiting engaged, altitude commands are faded out (42, 189) and torque commands are faded in (44, 190) and the collective command integrator is switched from altitude to torque (48, 54; 181, 185), torque limiting is ended in response to negative altitude commands or anticipated desired altitude signal (96, 150, 152; 205, 206); the anticipated desired altitude is determined by subtracting from the altitude error a time function of the altitude rate (84, 90; 193), torque limiting is not allowed to reengage for two seconds after disengaging (144, 204) nor within three seconds after reaching desired altitude during an automatic descent (146, 207), the system provides smooth transitions from altitude control to torque control, without oscillation

Abstract: A leading edge estimator for a vehicle terrain navigation system is described, the system having a radar terrain sensor which generates a position signal. The leading edge estimator includes a storage circuit for storing a time of arrival signal estimate. A delay circuit receives the position signal from the radar terrain sensor and produces a delayed version thereof. The position signal and the delayed version thereof are differenced and applied to a sample & hold circuit, which generates a sample of the differenced signal after a predetermined time period. The output of the sample & hold circuit is then applied to a one bit analog-to-digital convertor which determines the sign of the sampled difference signal. The output of the analog-to-digital convertor is then used as a control signal to effect the gating of one of two predetermined weighting factors.

Abstract: An altitude preselect apparatus for use with or incorporation into an automatic flight control system combines the incremental altitude signal from a pneumatic encoding altimeter with a vertical speed computation to generate a smooth, continuous instantaneous altitude signal. A vertical speed reference signal is generated to control the vertical flight path of the aircraft when the instantaneous altitude reaches a prescribed proximity to a desired flying altitude which is manually selected by the pilot. The apparatus initiates a capture sequence to hold the aircraft at the desired altitude once it is reached.