Abstract: Automatically reconfiguring an electronic landing display that includes a flight path vector (FPV) symbol and a rising runway symbol combined with a digital altitude value that merge at low aircraft altitudes is disclosed. During approach, when the aircraft descends below a predetermined minimum altitude, e.g., 200 feet, the FPV symbol is removed. When the aircraft is on the ground and during takeoff, the rising runway symbol is removed. Removing one or the other of the merging symbols prevents the symbols from overlapping. Thus, the potential for pilot error due to one of the merging symbols occluding the other is avoided.

Abstract: A proximity to terrain warning system for aircraft utilizes a first set of warning criteria to generate a warning in the event of insufficient terrain clearance after take off. A different set of criteria are employed to generate warnings when the aircraft in in a cruise or approach phase of flight or on a tactical mission. Mode switching is provided to select the appropriate criteria and to select an excessive descent after take-off set of warning criteria in addition to the first set of criteria when appropriate.

Abstract: A take-off performance monitor uses a sensor to produce a movement signal proportional to the movement of an aircraft during a take-off roll and, for each take-off, historical data is generated and stored based on the movement signal. An analyzing unit of the monitor uses the historical data and current conditions to calculate a reference take-off distance, reference acceleration data and reference velocity data. This information is output to the pilor to facilitate his judgment as to the adequacy to take-off performance. In the preferred embodiment, the analyzing unit utilizes five samples of acceleration and velocity during a take-off roll to solve an equation for five constants that are indicative of take-off performance. The five constants relate to static thrust, a linear relationship between thrust and velocity, a non-linear relationship between thrust and velocity, air drag and rolling drag, and these five constants constitute at least part of the historical data.

Abstract: This invention relates to a speed reference system for piloting an aircraft, delivering information on piloting in pitch, particularly during the phases of take-off and of go-round, wherein this system comprises a first voter receiving a first difference between a displayed speed and the real aerodynamic speed, a second difference between the real pitch attitude and a reference attitude and a third difference between the real vertical speed and a vertical speed limit; a second voter receiving the output signal of said first voter and said third difference and delivering the smaller of these two signals; and a third voter receiving the output signal of said second voter and a fourth difference between an aerodynamic speed limit and said real aerodynamic speed, and delivering the greater of these two signals.

Abstract: A method for producing a warning of the existence of low-level wind shear and an aircraftborne system for performing the method utilizes measured values of airspeed and temperature, to determine a temperature based hazard factor relating to the existence of a wind shear threat to the aircraft and to issue a warning whenever the hazard factor exceeds a predetermined threshold level based upon the performance characteristics of the aircraft. Temperatures may be sensed locally, such as by a resistive temperature sensor or, remotely, such as by an infrarred temperature detector. Furthermore, in accordance with preferred embodiments, an inertial reactive wind shear detector is utilized as an integrated safety measure. Moreover, the threshold level may be varied depending on such factors as aircraft altitude.

Abstract: A system for elaborating, on board an aircraft, an alarm signal in the event of a mini-tornado, wherebyan alarm threshold (.alpha.+.alpha.w) for mini-tornado is defined which is a function of the present incidence (.alpha.) of the aircraft, incremented or decremented by incidence equivalents (.alpha.w) corresponding to present and past winds and to present and past wind variations; andthe mini-tornado alarm is triggered off when the compensated present incidence (.alpha.+.alpha.w) exceeds a critical threshold, taking the aircraft configuration into account.

Abstract: A piloting aid system for landing an aircraft in either normal or adverse weather conditions is disclosed. The system applies a laser scanning process for determining and correcting the aircraft's position with respect to the commanded landing trajectory and for determining the aircraft's speed, altitude, and distance from the runway. The system provides the possibility to direct the aircraft exactly towards the runway longitudinal axis and to level the aircraft exactly parallel to the runway plane all along the landing trajectory and, consequently, to effect a safe landing under visibility conditions which would otherwise prevent landing.

Abstract: The rate-of-climb indicator of this invention can indicate the existence of wind shear.

Abstract: An apparatus and method for compensating for asymmetrically produced total engine thrust caused by an engine failure in a multiengine aircraft. The presence of asymmetric total thrust is detected by monitoring aircraft performance parameters, including engine manifold pressures, airspeed, roll angle and yaw. When an engine failure resulting in the production of asymmetric thrust is detected at air speeds below a minimum controllable air speed for the aircraft, and during large aircraft bank angles, the power output from an operating engine is reduced to regain and maintain controllable flight conditions. Limiting the adverse yaw produced by an engine failure by reducing power output from operative engines reduces the tendency of the aircraft to roll into the inoperative engine, hence the aircraft is halted.

Abstract: An alarm means including a digital microcomputer having a memory programmed for storing a look-up table defining an alarm envlope which, above a predetermined altitude, is based on a relationship between altitude and ground-closure rate which is independent of ground velocity, and below said predetermined altitude, is based on a relationship between altitude and ground-closure rate which is dependent on ground velocity.

Abstract: An improved windshear warning apparatus for aircraft, responsive to both the magnitude of the wind shear and the allowable time the windshear can be tolerated at a given magnitude. The sensed magnitude is used to compute the allowable time before providing a windshear alarm. For large windshear rates, the allowable time is short; conversely for small windshear rates which exceed a threshold level, a longer time period is computed before an alarm occurs. Since a windshear rate must persist for the computed allowable time before activating the alarm, windshear rates that are above the threshold level for elapsed time less than the computed allowable time will not result in an enunciation, while high magnitude windshear rates of short duration will not cause false alarms since they do not exceed the computed allowable time.

Abstract: An aircraft ground proximity warning system having an excessive descent rate warning mode which generates a warning signal when the descent rate of the aircraft exceeds a predetermined limit for the particular altitude of the aircraft above ground. The warning system provides for three separate warnings. A SINK RATE advisory warning is generated for combinations of lesser descent rates and greater altitudes. A PULL UP warning is generated for higher descent rates at lower radio altitudes. After a predetermined time after the SINK RATE warning is generated a TERRAIN warning is provided to indicate to the pilot of the aircraft that an excessive sink rate condition exists and the aircraft is flying over undulating or mountainous terrain. Also disclosed is logic circuitry for detecting that the aircraft is flying over undulating terrain.

Abstract: An aircraft ground proximity warning system is disclosed having an inadequate terrain clearance warning mode, wherein the criteria required to generate the warning is modified when the aircraft is flying over undulating or mountainous terrain. The system is responsive to signals representative of the radio altitude, the barometric altitude, the speed of the aircraft, the flap position and the landing gear position to provide warnings when the aircraft is operating below a predetermined altitude with either or both of the landing gear of the flaps not in a landing configuration. The warning system also provides a warning when the aircraft is traveling above a predetermined speed and below a predetermined altitude irrespective of the configuration of the landing gear or the flaps. Also disclosed is logic circuitry for detecting that the aircraft is flying over undulating or mountainous terrain and modifying the warning envelope during such condition to provide longer warning times.

Abstract: The invention is a real-time takeoff and landing performance monitoring system which provides the pilot with graphic and metric information to assist in decisions related to achieving rotation speed (V.sub.R) within the safe zone of the runway or stopping the aircraft on the runway after landing or take off - abort. The system processes information in two segments: a pretakeoff segment and a real-time segment. One-time inputs of ambient conditions and airplane configuration information are used in the pretakeoff segment to generate scheduled performance data. The real-time segment uses the scheduled performance data, runway length data and transducer measured parameters to monitor the performance of the airplane throughout the takeoff roll. A novel and important feature of this segment is that it updates the estimated runway rolling friction coefficient. Airplane performance predictions also reflect changes in headwind occuring as the takeoff roll progresses.

Abstract: The present invention constitutes a system for generating an elevator command signal for directing a pilot in guiding his aircraft along a path effective for recovering from hazardous windshear conditions. The system includes a descending mode guidance subsystem (10), an ascending mode guidance subsystem (12) and a switching mechanism (14) for shifting between the two subsystems. The descending mode subsystem includes an acceleration generator (20), a flight path command generator (22), a flight path error generator (24), a descending mode pitch error generator (26), an airspeed control device (28) and a descending mode signal controller (30). These components are connected serially together and operate to form an elevator command signal corresponding to the acceleration required to halt the descent of the aircraft by a fixed altitude level.

Abstract: A method and device are provided for guiding an aerodyne on the runway, picularly during the taxiing phase preceding take off, the device including an inertial unit adapted for delivering signals representative of the North speed, of the East speed, of the azimuth and of the ground speed of the aerodyne. From these signals, a computer elaborates a parameter defining the axis of the runway, during an apprenticeship step during which the aerodyne, guided on site by the pilot, taxies along the axis of the runway, and stores this parameter at the end of the step. The computer then delivers to the means piloting the aerodyne a synthetic runway aberration signal between the axis of the runway thus stored and the position of the aerodyne delivered by the inertial unit.

Abstract: A method for predicting and monitoring the takeoff performance of an aircraft uses information from one or more previous takeoffs of the aircraft to generate a prediction of the takeoff performance for the current takeoff. In the preferred embodiment, a takeoff profile for the current takeoff is generated and includes information about predetermined characteristics of the aircraft and information about ambient conditions at an airport from which the takeoff is being monitored. Expected performance data for the current takeoff is then generated from the takeoff profile and used to select a set of actual performance data previously stored from the one or more previous takeoffs. A selected "best fit" actual performance data set is then displayed in an appropriate fashion. Upon takeoff, a set of monitored performance data is generated as a function of one or more of sensed takeoff parameters.

Abstract: An aircraft navigational system includes a digital computer, a first visual output for displaying to an aircrew a geometrical representation of an optimum descent guideslope relative to a symbol representing the location of the aircraft, and a second visual output for displaying optimum descent guideslope information, such as altitude and distance, alphanumerically. The visual display provides guidance information to the aircrew to control the descent of the aircraft along an optimum descent guideslope which is referenced to a selected end of descent waypoint such as a destination airport or to an instrument approach marker. The guideslope is calculated in accordance with predetermined airspeed and altitude requirements with define a descent profile which is fuel efficient and which complies with aviation regulations regarding maximum airspeed limitations.

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: Windshear indicator system comprised of a plurality of individual windshear detection and indication devices (10) disposed to one side of and parallel to the landing approach and takeoff areas of an airport runway. Each device (10) has a wind velocity sensor (24) and a wind direction indicator (22). Wind speed information is visually displayed in an array of vertical lights (30-40) of one color. A circular pattern of second colored lights (50-64) is provided so that the upper half of the pattern shows head winds and the lower half indicates or displays tailwinds to warn of a windshear condition. A green "go" light (74) flashes with the upper half of the circular lights (50-64). A red "no go" light (76) flashes with the lower half of the circular array of lights to warn of tailwinds and a windshear condition.

Abstract: Method and apparatus for commanding an optimal flight path for an aircraft encountering a windshear condition. An airspeed rate signal equal in magnitude and opposite in sense to the windshear is applied to derive a variable rate of change of airspeed command for application to a flight director indicator. Limits are placed on the derived command such that the minimum allowable speed command is stick shaker speed and the maximum allowable speed command is the nominal speed in the absence of the windshear. The resultant command signal represents a true airspeed rate that yields an optimal flight path for the aircraft to exit the windshear condition.

Abstract: A computerized flight inspection system is disclosed. The system of the present invention may be utilized to generate an accurate reference location with respect to an airport runway for an aircraft having an inertial navigation system. A selected geometric pattern having a highly unambiguous autocorrelation function is placed on at least one end of the runway. A video line scanning camera mounted to the aircraft is then utilized to scan the geometric pattern in a line generally perpendicular to the line of flight. The output of the video line scanning camera is then correlated with a stored reference pattern to generate a signal indicative of the detection of the geometric pattern on the runway. A laser altimeter is mounted to the aircraft and utilized to generate an accurate signal indicative of the aircraft altitude with respect to the runway pattern. The outputs of the correlation circuit and the laser altimeter are then utilized to correct data from the inertial navigation system.

Abstract: An aircraft performance instrument which provides a first indicator which represents the line of level flight of the aircraft and a second indicator representative of the maximum permissible angle of attack of the aircraft.

Abstract: An aircraft takeoff monitor having distance traveled sensors for measuring the distance traveled after the initiation of the takeoff roll. These sensors are interfaced with an onboard computer to provide the computer with information on the actual distance traveled by the aircraft since the takeoff run was initiated. The computer is programmable to receive predetermined input signals, including runway length, real-time inputs, and the initiation time, with the computer constantly generating a predicted ground distance that should be traveled since the initiation of the takeoff run. The computer is further programmed to compare the actual ground distance traveled to the predicted ground distance which should have been traveled and provide a display signal representative of this comparison on an onboard display instrument.

Abstract: A system for warning the pilot of a rotary wing aircraft such as a helicopter of a flight condition that, if left uncorrected, would result in the tail of the aircraft striking the ground monitors the altitude above ground, descent rate, pitch and pitch rate of the aircraft and provides a warning if the relationship between the aforementioned parameters is such that a tail strike is imminent.

Abstract: A system particularly adapted for guiding aircraft through wind shear conditions includes: a thrust command control (10) for maintaining airspeed and groundspeed within a defined range; a detection system (12) for detecting and annunciating the presence of moderate and severe wind shear; and a pitch command system (14) which provides pitch command signals for optimum climb out from a wind shear condition.

Abstract: Energy compensation means (64) for an onboard aircraft flight management system (12). The energy compensation means may be used to eliminate unwanted throttle activity during unscheduled level segments (80) in a descent path. The flight management system includes means for enabling selection of various flight modes including a descent mode, means for determining a descent path, including target speed and target altitude (70) profiles as a function of aircraft position, and means for providing information regarding the aircraft current altitude, current position, current calibrated airspeed (CAS) and current true airspeed (TAS). The flight management system also includes means operative in descent mode for providing a target signal (V.sub.TGT) representing the target speed for the descent path for the current aircraft position, and display means (16) responsive to the target signal for displaying the target speed.

Abstract: The invention provides for rapid response and reliable detection of vertical windshear during the takeoff and approach phases of flight. Standard instrumentation available on many aircraft is used to calculate the down-draft acceleration and its effect on the aircraft's performance capability. The invention utilizes inputs from vertical acceleration, true airspeed, pitch angle, and angle of attack sensors. The rate of change of vertical wind is derived from the sensed signals and used to determine the margin between the aircraft's present performance capability and the predicted performance capability at stick shaker speed.

Abstract: A wind shear detection and alerting system (30) compares inertially derived accelerations with air speed rate to provide a wind shear warning signal. Inertially derived accelerations are used instead of purely inertial accelerations because purely inertial systems generally require a vertical gyro. By utilizing angle of attack (.alpha.) and flight path angle (.gamma.) instead of pitch angle (.theta.) in the calculation, no vertical gyro signal is required and the system will be responsive to vertical as well as horizontal shear conditions. An enhanced version of the system is also compensated for roll angle (.phi.), with the roll angle being derived from the rate of change of heading (.PSI.) to avoid the need for a vertical gyro. The alerting system is capable of providing visual and aural warnings for a variety of wind shear conditions, such as, head shear, tail shear, head shear followed by tail shear and wind shear trend.

Abstract: An improved glide slope indicator system for facilitating aircraft landings under adverse lighting conditions on remote or austere landing sites is provided which comprises a pair of indicators deployable near ground level on each side of a runway, each indicator including a housing having an optical window and a pair of light sources mounted in predetermined spaced relationship to each other and to the optical window and connected to a power source and related circuitry to project a well defined first blinking and second steady light beam of predetermined angular divergence and overlap, one indicator disposed to project beams with an overlap elevated at a first angle relative to horizontal and the other indicator disposed to project beams with an overlap elevated at a second angle relative to horizontal different from the first, with a preselected glide path lying between the two overlaps.

Abstract: An active, electro-optical display system for use on fixed-wing, land-based airport runways, is disclosed for remotely guiding a pilot during visual approach and landing of an aircraft. Conventional Microwave Landing System (MLS) ground-transmitted data is air-derived on board the aircraft and data-linked to a ground receiver to produce a continuous digital data signal indicative of aircraft slant range, elevation and azimuth relative to the desired landing position. The resulting data signal is electrically coupled to a signal processor governed in accordance with control guidance laws to produce three discrete signals indicative of the magnitude and direction of the descent rate error, the flight path acceleration, and the lateral drift rate of the aircraft relative to the intended landing area.

Abstract: A system for warning the pilot of an aircraft flying at low level, particularly over rising terrain, of an excessive closure condition that could result in controlled flight into terrain if left uncorrected. Specifically a warning system is disclosed that monitors the terrain closure rate of an aircraft under certain conditions. These conditions relate to the weapons not being armed, the aircraft flying between 100 and 1800 feet and the air speed exceeding 200 knots. When these conditions are met a warning is provided to the pilot that the terrain closure rate exceeds a predetermined safe limit for the radio altitude at which the aircraft is flying.

Abstract: An aircraft performance margin indicator including a display (21) that, during takeoff and landing, informs the pilot of the ability of the aircraft to either stop safely or achieve a safe flying speed before reaching the end of the runway is disclosed. A plurality of dedicated microprocessors (41, 43, 45, and 47), each of which receives pertinent data about the aircraft, the runway and the existing environmental conditions, produce one or more symbol control signals. The symbol control signals control the position of symbols that form part of the display (21). The display scale is a normalized runway and the display includes an airplane symbol (23) that shows the location of the aircraft as the aircraft moves down the runway. The microprocessor controlled symbols include GO and STOP bugs (25 and 31) and a ROTATE bar (27). The ROTATE bar indicates the last point at which the aircraft can be safely rotated under present FFA regulations.

Abstract: This Takeoff and Abort Instrument system, mounted on the pilot's instrument panel, will indicate to the pilot, as soon as the throttles are advance to the takeoff position and brakes are released if all engines are producing the designed takeoff thrust. During the takeoff run an ABORT indication will be visible to the pilot anytime the net aircraft linear acceleration degrades below that amount required to make a safe takeoff. This instrument assembly is comprised of two major components: A. A flexible transparent tube formed into a right triangle with the shortest leg being mounted vertically on the instrument face; this leg becomes a sight gauge up which a colored non-freezing liquid rises directly in proportion to the aircraft's linear acceleration. The longest leg connects the base of the sight gauge to a reservoir located forward of and level with the base of the sight gauge.

Abstract: A system which provides an increased minimum aircraft pitch attitude during take-off or go-around operations in the event that an unsafe wind shear condition is encountered. A control signal from a wind shear warning system, indicative of a dangerous wind shear condition, is fed to a switching device which controls the velocity command signal to the flight director pitch control. This switching device, in response to the wind shear signal, changes the velocity command to a lower predetermined value, such that the attitude of the aircraft is automatically increased to handle the wind shear encounter.

Abstract: A device for indicating that an airplane has reached a safe speed for take-off rotation. The device indicates when both the airspeed equals or exceeds a preselected minimum airspeed and the ground speed equals or exceeds the preselected minimum airspeed less a preselected margin.

Abstract: A windshear warning apparatus which separately compares a plurality of signals derived from horizontal and vertical inertial acceleration and air mass acceleration components to indicate incipient windshear. The compared signals are substantially equal under normal wind conditions but are significantly different under windshear conditions. A signal proportional to the product of the magnitude and rate of change of the total or resultant inertial acceleration of the aircraft is used to provide a warning of a significant windshear condition.

Abstract: An aircraft stall avoidance system uses flight measurements such as accelerations, aircraft configuration, engine power, atmospheric conditions, and other related characteristics in computing the speed at which a specific aircraft is likely to stall in real time. The indicator provides continuous stall avoidance information to the pilot along with positive warning signals when critical safety margins are broached.

Abstract: An aircraft is provided with wind velocity measuring equipment which measures the wind velocity both (1) close to the aircraft and (2) at a considerable distance such as one-half mile or a mile away from the aircraft; and a large difference in these two measured velocities indicates dangerous windshear conditions. Either a warning signal is given to the pilot, or automatic control apparatus is actuated, to avoid crash conditions. A single pulsed carbon dioxide (CO.sub.2) laser velocimeter may be mounted in the aircraft for measuring both the close-in and the distant wind speeds. The laser optic focus is shifted between the near and far measurements, and the return signal is time gated to increase signal-to-noise ratio.

Abstract: A display for aiding the pilot of an aircraft in anomalous wind environments. Wind velocity components are measured by an instrument 11, processed by a computer 12 and a vector generator 17 and then displayed as a vector 34 on the display shown in FIG. 3. A signal F indicative of flap position selects a flight validated lift curve which is displayed as a lift curve channel 42. During normal wind conditions the cursor 35 marking the termination of vector 34 is in the channel of curve 42. However, during wind anomalies cursor 35 moves outside the channel. It then becomes the task of the pilot to control the aircraft such that cursor 35 will move back into the channel.

Abstract: An improved flight director go-around mode adjusts the collective stick position in a closed loop to increase lift to a desired value. If the engagement airspeed is below the maximum rate of climb airspeed, the airspeed is increased towards the maximum rate of climb airspeed at a moderate rate. When the maximum rate of climb airspeed is attained, or if the engagement airspeed is at least the maximum rate of climb airspeed, and the rate of climb is satisfactory, the airspeed is maintained. If the engagement airspeed is greater than the maximum rate of climb airspeed and the desired rate of climb is not achieved within ten seconds, the airspeed is decreased towards the maximum rate of climb airspeed. Heading or course is automatically maintained when go-around is engaged.

Abstract: In order to reduce nuisance warnings and to increase the effectiveness of real warnings produced by a ground proximity warning system, the criteria for generating a warning is varied for certain airport areas to take into account the terrain in those areas. Along with position data, certain flight parameters such as heading, altitude, glideslope and localizer deviation are checked by the system in order to ensure that the aircraft is located in the desired warning modification area. In addition, the ground proximity warning system includes a mechanism for ensuring that the corrected barometric altitude of the aircraft is within acceptable limits.

Abstract: A glide slope indicator system in which light from an incoming aircraft's landing light is shaped by spherical/cylindrical lens combination into a line image which strikes a linear photodiode array. By determining which photodiode in the array the center of the line image strikes, the glide slope angle can be determined. An appropriate signal is communicated to the pilot via a pair of indicator lights mounted on the runway depending upon whether the aircraft is above, below or on the desired glide slope angle.

Abstract: A computerized system for examining single engine performance capabilities and developing alternate routes/routings for two-engine aircraft in compliance with FAR 121.19 (driftdown, one engine inoperative) such that an attendant loss of altitude will not result in the aircraft dropping below a net flight path altitude and clearance distance with respect to the earth's surface along a given route between a flight originating point and a destination. Included as a part of the computation are the radius of action fuel capabilities which takes into consideration the "maximum continuous thrust", the power demands on the remaining engine, air density-temperature change attendant with altitude loss, and real time wind conditions.

Abstract: A warning device, for a helicopter with a tail rotor and a mechanical protection device (15) therefor, for giving warning if the helicopter tail approaches too closely the ground or an obstruction. The warning device comprises a height-finder (11) with a transmitting/receiving antenna (26) mounted at the helicopter tail to produce a height-finding beam backwards and obliquely downwards. Height signals are processed by computing means (12) to determine the sink rate of the tail and in dependence upon this sink rate and the instantaneous height, a warning signal is initiated if this corresponds to a predetermined relative relationship. The higher the sink rate the greater is the height at which the warning signal is initiated and vice versa.In the preferred arrangement the beam is directed substantially along or parallel to the axis of the mechanical protection device (15).

Abstract: An apparatus is provided for an amphibious aircraft which also has retractable landing gear. The apparatus senses changes in aircraft speed indicative of an imminent landing or a takeoff and prompts the pilot to verify that the landing gear is in a position compatible with the type of surface, land or water, chosen for landing.

Abstract: An apparatus for determining various operational conditions of an aircraft such as acceleration, deceleration, angle of attack and wind shear.

Abstract: To increase the effectivity of warnings and to decrease nuisance warnings in a ground proximity warning system having several modes of operation, the switching from one mode to another is done as a function of time. In addition, in a ground proximity warning system where a warning signal is generated in accordance with a predetermined relationship between flight parameters, one or more of these parameters can be varied as a function of time in order to, for example, increase the altitude above ground as a function of time from take-off that a terrain clearance warning may be generated or to decrease as a function of time, the radio altitude below which a negative take-off after a climb warning may be generated.

Abstract: An evacuation aid for a high rise building comprising a wind cone lighting device which can be operated for a substantial period of time under emergency power conditions such as from a battery supply. The wind cone is lighted by a single light rotating with the wind cone and powered through slip ring assemblies.

Abstract: A glide path instrument for an aircraft to display to a pilot that the aircraft is descending on a predetermined inclined glide path. The instrument includes a rectangular casing mountable in stationary position in the aircraft and carrying a freely pivotable frame which has sighting elements at opposite ends spaced different vertical distances from the plane of the frame. The frame carries a pendulum-like structure including depending legs supporting free swinging weights. The sighting elements align in a single sight plane with a runway reference point when the aircraft is at the predetermined glide angle. A lamp in the casing illuminates the sighting elements.