Aircraft display with potential thrust indicator

[0002] This application is a continuation of U.S. patent application Ser. No. 09/637,262, filed Aug. 10, 2000, now U.S. Pat. No. 6,262,674 which is hereby incorporated by reference.

[0003] The present invention relates generally to electronic displays for aircraft and more specifically to potential thrust indicator symbology in an aircraft cockpit display for displaying aircraft engine thrust (or engine power) in terms of actual and potential aircraft flight path.

[0004] Experienced aircraft pilots are familiar with aircraft handling qualities under normal flight conditions. Thrust, weight, lift, and drag are the forces that act upon an aircraft. Maneuvering is accomplished by variations of these forces and is controlled by the throttles and flight controls. The power produced by the engines determines the angle that an aircraft can fly and still maintain airspeed (e.g. neither accelerate nor decelerate). Similarly, the drag on the airplane determines the descent angle that the airplane can fly and not accelerate. Aircraft drag and engine thrust models are used to indicate engine thrust as a climb or descent angle on the display where the greatest climb and the greatest descent angle represents the maximum and minimum power parameters.

[0005] Electronic displays such as Primary Flight Displays (PFD's), Head-Up Displays (HUD's), Head-Down Displays (HDD's) and the like are well known and widely used to display information in aircraft. FIG. 1 illustrates a conventional flight path vector group 10 presented to an aircraft pilot on an attitude display. The display shows a horizontal line 50, which indicates the axis of flight parallel to the horizon. Pitch ladder 60 indicates the pitch or potential pitch of the plane. A flight path vector (FPV) indicator 20 represents the sum of all forces acting on the aircraft and indicates the direction of aircraft translation through space. A speed error indicator 30 emanates from the FPV indicator 20 and represents the difference between the selected airspeed and the current airspeed. The potential flight path vector (PFPV) indicator 40 is displayed in reference to the FPV indicator 20. PFPV indicator 40 is an indication of the aircraft's instantaneous acceleration along the flight path. The angle at which the PFPV indicator 40 is displayed relative to the pitch ladder represents the acceleration scaled by the acceleration due to gravity. The FPV indicator 20 and the PFPV indicator 40 may be obtained from onboard inertial reference systems, Global Positioning System (GPS) aided attitude sensors, or the like. In FIG. 1, the display indicates that the aircraft is accelerating (the PFPV indicator 40 is above FPV indicator 20). Further, PFPV indicator 40 indicates that the flight path may be increased to approximately a 6-degree climb with no acceleration along the flight path.

[0006] However, with the prior art displays as described above, the pilot is given no direct indication of thrust. Rather, the pilot must utilize some internal model (usually gained through experience) based on the existing engine displays. Thus, there exists a need for an aircraft display which not only provides the pilot with a means for directly setting engine power to achieve desired performance, but also enables precise aircraft speed control with a reduction in pilot workload and provides control symbology in the pilot's primary field of view.

[0007] Various aspects of the present invention provide an aircraft display apparatus which combines a flight path vector group with a potential thrust indicator to reduce pilot workload. The display apparatus includes a display screen, a pitch ladder symbol displayed on the screen, a horizontal line (representing level flight) displayed on the screen and a flight path vector group displayed on the screen. The flight path vector group includes a flight path vector symbol, a potential flight path vector symbol, a potential thrust symbol, and a speed error indicator. The flight path vector group is oriented on the display screen in relation to the pitch ladder and the horizontal line. The position of the potential thrust symbol is relative to the pitch ladder and represents current engine power and power limits of the aircraft.

[0008] In accordance with another embodiment of the present invention, the potential thrust symbol further comprises a thrust and drag limit symbol and at least one throttle symbol.

[0009] In accordance with yet another embodiment of the present invention, the potential thrust symbol indicates the aircraft's climb capability with a failed engine.

[0010] In accordance with a further embodiment of the present invention, the potential thrust symbol indicates the potential aircraft descent angle when drag devices such as speed brakes, flaps and landing gear are activated.

[0011] These and other aspects of the present invention are described in the following description, attached drawings and claims.

[0012] A detailed description of embodiments of the invention will be made with reference to the accompanying drawings, wherein like numerals designate corresponding parts in the several figures, and wherein:

[0013] FIG. 1 illustrates the display format of a flight path vector group without the present invention.

[0014] FIG. 2 illustrates a display format of the present invent

[0015] FIG. 3 illustrates forces that act on an aircraft in flight.

[0016] FIGS. 4A-E illustrates displays of the present invention in five different operational situations.

[0017] FIG. 5 illustrates a display format of the present invention indicating failure of an engine.

[0018] FIG. 6 illustrates a display format of the potential thrust indicator of the present invention with drag device symbology.

[0019] FIG. 7 illustrates components of an embodiment of the present invention.

[0020] FIG. 8 illustrates the invention embodied in an aircraft.

[0021] The following descriptions are of exemplary embodiments only, and are not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the invention. Various changes to the described embodiments may be made in the function and arrangement of the elements described without departing from the scope of the invention as set forth in the appended claims.

[0022] Referring now to FIG. 2, a display of an exemplary embodiment of the present invention suitably includes a flight path vector group 100 which includes a FPV indicator 110, a speed error indicator 120, and a PFPV indicator 130. In addition, flight path vector group 100 of the present invention comprises a potential thrust indicator 160. Potential thrust indicator 160 provides the pilot with a means for setting engine power to achieve a desired aircraft flight path and acceleration. Potential thrust indicator 160 further includes thrust/drag limit indicators 170 and first and second throttle indicators 180 and 190. FIG. 2 further shows a pitch ladder 140, which corresponds to the pitch of the aircraft, and a horizontal line 150, which corresponds to the axis of flight parallel to the horizon. The entire flight path vector group moves with respect to pitch ladder 140. The numeric values associated with the above symbology elements of the flight path vector group may be determined from inertial data or other GPS aided attitude sensors.

[0023] As in the prior art, the FPV indicator 110 represents where the aircraft is moving through space. The PFPV indicator 130 represents the angle that the aircraft may climb or descend while maintaining current airspeed, e.g., the pilot may “fly” the FPV indicator 110 to the PFPV indicator 130 changing the aircraft's path through space while maintaining airspeed. However, using the potential thrust indicator 160 in relation to the flight path vector group display, the pilot now may directly move the throttles to set engine power to achieve a desired PFPV indicator setting. As described below, the PFPV is an expression of the aircraft's longitudinal acceleration scaled by the acceleration due to gravity (≈32.1 feet/sec*sec). Advancing the throttles while keeping all else constant will add energy to the airplane and cause it to accelerate. The pilot controls this acceleration referencing the changes in the placement of the PFPV. The power produced by the engines determines the angle that the aircraft may fly and still maintain airspeed (e.g., neither accelerate nor decelerate). Similarly, the drag on the airplane determines the descent angle that the airplane may fly and not accelerate. The thrust/drag limit indicators 170 indicate to the pilot the maximum climb angle achievable at maximum power without acceleration and the maximum descent angle possible at maximum drag without acceleration. The throttle indicators 180 and 190 display the engine thrust contribution to the inertial indications.

[0024] The potential thrust available to an aircraft may be represented by a mathematical equation. Referring now to FIG. 3, the forces acting on an aircraft in flight include thrust, lift, drag and weight. The current power of the aircraft engines and current vertical speed determines the potential flight path angle Ø_PFPA. A flight path angle Ø_FPVis the direction of flight with respect to the earth. The “specific excess power,” P_s(e.g., the excess power per unit weight), available from the engines is calculated using the following equation: $\begin{array}{cc}{P}_s=\frac{\mathrm{TV}-\mathrm{DV}}{W}=\frac{dh}{dt}+\frac{V}{g}\frac{dV}{dt}& \left(1\right)\end{array}$

[0025] where T is the thrust, V is the velocity, D is drag, W is weight, g is gravity, dh/dt is the climb rate, dv/dt is the acceleration of the aircraft and flight is at one “g.” By dividing the equation by V, the equation becomes one of “excess thrust” per unit weight and has no. units of dimension: $\begin{array}{cc}\frac{T-D}{W}=\frac{1}{V}\frac{dh}{dt}+\frac{1}{g}\frac{dV}{dt}& \left(2\right)\end{array}$

[0026] The term on the left represents the net power being applied to the aircraft by the engines minus the drag. The position of throttle indicators 180 and 190 is scaled to this value by an air data computer. The maximum position of thrust/drag limit indicator 170 may be determined by the value of this term when throttles are at a maximum and drag is at a minimum. The minimum position of thrust/drag limit indicator 170 may be determined by the value of the same term when drag is at a maximum and thrust is at a minimum. As is evident from this equation, when a pilot wishes to maintain current aircraft speed, dv/dt is zero. Consequently, an increase in thrust will result in aircraft climb. Similarly, when a pilot wishes to maintain current altitude, dh/dt is zero. Accordingly, any increase in thrust will result in acceleration.

[0027] Referring again to FIG. 3, each term in Equation 2 can be expressed as an angle:

[0028] Ø_TA=Ø_FPA+Ø_PFPA

[0029] where Ø_TAis the excess thrust angle, Ø_FPAis the flight path angle and Ø_PFPAis the potential flight path angle. Modifications to the excess thrust calculation may be applied to account for flight in other than one “g” situations.

[0030] FIGS. 4A-4E illustrates the displays of exemplary embodiments for five different operational situations. In FIG. 4A, the pilot has selected maximum power, as is evident by the fact that throttle indicators 180 and 190 and PFPV indicator 130 are at the maximum thrust/drag limit indicator 170. In FIG. 4B, the pilot has selected a power setting less than maximum and the aircraft is accelerating (PFPV indicator 130 is above FPV indicator 110). In FIG. 4C, the throttles are split (i.e., not at the same power setting) and below maximum power and the aircraft is accelerating. In FIG. 4D, the power is set below maximum power and the aircraft is decelerating. In FIG. 4E, the power is set near maximum power and the aircraft is maintaining current airspeed.

[0031] The present invention may also inform the pilot of available power when an engine has failed. By way of example, FIG. 5 shows a potential thrust indicator 160 with throttle indicator 190 represented by an “x”, indicating that the right engine has failed. The left engine is at full power. By using potential thrust indicator 160, the pilot may determine the aircraft's climb capability with a failed engine.

[0032] FIG. 6 shows a further optional embodiment of potential thrust indicator 160 of the present invention with symbology representing performance effects of drag devices. Ø_TAmaxrepresents the power available when thrust is at a maximum, Ø_DAmaxrepresents the power available when drag is at a maximum and throttle indicators 180 and 190 are shown at idle. When the pilot extends the aircraft speed brakes, a speed brake indicator 200 appears on the display. Speed brakes indicator 200 represents the descent angle possible with speed brakes of the aircraft extended. When the pilot extends aircraft wing flaps, a flaps indicator 210 appears on the display. Flaps indicator 210 represents the descent angle possible with the aircraft flaps extended. While FIG. 5 shows the descent angle possible with flaps one (F1) extended, it will be recognized that a plurality of flap indicators may be shown (e.g., F2, F3, . . . ) relative to the number of flaps on an aircraft. When the pilot extends the aircraft landing gear, a landing gear indicator 220 may appear on the display. Landing gear indicator 220 represents the descent angle possible with the aircraft's landing gear extended.

[0033] FIG. 7 illustrates the components of an exemplary embodiment. The embodiment is implemented on a head-up display (HUD). HUD 230 includes a combiner 230A, an overhead unit 230B, and a display computer 230C. Display computer 230C communicates display data to overhead unit 230B which projects the display onto a display screen 230D of combiner 230A. The technology of these components is well known in the art and need not be described in further detail.

[0034] The invention is not limited to HUD's and may be implemented on any type of display including, but not limit to, CRT's, LCD's and HMD's (helmet-mounted displays). These displays are generically referred to as electronic displays and are interchangeable with HUD 230 for the purposes of the invention.

[0035] Electronic display (or HUD) 230 may obtain information from many aircraft systems depending on the specific implementation. These aircraft systems may include display controllers 231, air data computers (ADC) 232, inertial reference systems (IRS) 233, performance computers 234, flight guidance computers 235, flight management computers 236, and the like.

[0036] In an exemplary embodiment as shown in FIG. 7, various components may communicate information to electronic display 230. For example, a display controller 231 communicates commands (e.g., on/off, mode, brightness, etc.) to electronic display 230. An air data computer 232 communicates airspeeds, mach numbers, altitudes, vertical speeds, and the like. An inertial reference system 233 communicates acceleration data, attitude data, heading and position data, etc. A performance computer 234 communicates optimal flight path and cost information. A flight guidance computer 235 communicates guidance parameters. A flight management computer 236 communicates information including flight path information and waypoints. Of course, other embodiments may include various other components.

[0037] FIG. 8 illustrates the invention embodied in an aircraft. An aircraft 240 includes a frame 240A, engines 240B, a cockpit 240C and electronic display 230 (shown external to the aircraft 240).

[0038] Thus, an aircraft display with a potential thrust indicator according to various aspects of the present invention provides an engine display that is physically located in the pilot's instrument scan area (on the attitude display or HUED, for example). Further, the aircraft display with potential thrust indicator provides to the pilot a means to determine engine power and engine throttle to set climb or descent angles of the aircraft. The aircraft display includes numerous other features and advantages that are not specifically identified herein. While the present invention has been described with reference to specific preferred embodiments thereof, various changes may be made without departing from the scope of the invention as claimed. In addition, many modifications may be made to adapt the present embodiments to a given situation without departing from it essential teachings.