Data Processing System for Pre-Planning the Flight of an Aircraft

This invention relates to data processing systems for pre-planning the flight of an aircraft from information on a chart and known parameters relating to the aircraft.

The planning of routes, for aircraft is commonly done to ensure that the aircraft follows a preset path to take advantage of, or to avoid, certain specified features. For example, an aircraft may be required to follow specified airways, turning at identified points. The route planning may be done whilst the aircraft is in flight, or, preferably, it may be preplanned to reduce the workload in the crew during the flight.

It is an object of the invention to provide a data processing system operable to provide an aircraft flight plan prior to the start of the flight.

According to the present invention there is provided a data processing system for planning routes from information carried on a chart, which system includes plotting board such as a coordinate digitizer tablet for determining relative position coordinates (e.g. X and Y coordinates) of each selected point on a chart and for outputting signals indicating the position coordinates of each of a number of selected points on a route; an input device for deriving further signals defining known parameters such as speed, fuel consumption, fuel load and bank angle relating to an aircraft intended to traverse the route; a calculating device responsive to said position signals and to said further signals defining known parameters to calculate predetermined variable factors, such as the bearing between two points, fuel consumption, and time of flight relating to the route between the selected points; and a recording device for providing a record of said variable factors for use when the aircraft follows said route.

Preferably the plotting board for determining relative position coordinates comprises a plotting table having a surface to which the chart is secured. The calculating device may be operable to accept charts of different scales or projections.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 shows a block schematic diagram of a data processing system in accordance with the invention; and

FIG. 2 illustrates a modification to the system of FIG. 1.

Referring now to FIG. 1, the system is based on a plotting board PB and its associated circuitry, indicated generally by the reference 10. The plotting board consists of a surface to which a map or chart may be secured and under which are two sets of conductors. Each set comprises a large number of parallel conductors arranged as two inter-leaved arrays, one set being parallel to the X axis and the other set parallel to the Y axis of the board. A cursor C is movable over the surface of the board and carries a coil energisable by a sinusoidal waveform of constant amplitude so as to produce a symmetrical magnetic field. The cursor also carries a cross-wire which is accurately positioned in the centre of this field. The alternating current supply for the cursor is derived from a clock generator CK through a counter CTR, which for this purpose acts as a frequency divider. The square-wave output from the counter is converted to a sine wave, and a power amplifier PA produces the drive current for the cursor coil. The outputs from the two sets of X conductors and the two sets of Y conductors on the plotting board are fed through circuitry which produces signals representing the X and Y outputs. These signals are applied to a phase detector PD which compares the phases of the X and Y signals with the original square-wave used to drive the cursor, and produces pulses for each increment of movement of the cursor. These increments are used to increase or decrease the contents of separate X and Y counters CTX and CTY respectively to obtain the X and Y coordinates of the cursor at any instant.

The circuitry described above is well known and frequently used with plotting boards for digitising drawings and the like. U.S. Pat. Nos. 3,647,963 and 3,801,733 disclose arrangements of this type.

The X and Y counter outputs are multiplexed when required by a multiplexer MX, and applied as a 16-bit number to a processor CPU having an associated store ST. An interface IF interconnects the processor and a printer PR which may have an associated keyboard to act as an input device. Switching logic SL converts signals from a number of push buttons B carried on the cursor C to signals for controlling the printer and the processor, the latter via the interface IF. A keyboard K is connected to the interface IF.

The final elements of the system are optional peripheral output devices such as a portable, that is removable, store PS, a visual display unit VDU or a cassette recorder CR. The details of these various system elements and the manner in which they are interconnected are conventional.

In operation, for initilization and calibration, first a chart or map is placed on the plotting board and the cursor is set to a known datum position. The coordinates of this datum are typed in via the keyboard of the printer, either in map grid form or in terms of latitude and longitude. A second known datum, having different X and Y coordinates, is fed in similarly. The distance between points each defined in terms of X and Y coordinates can be calculated by the processor using Pythagorus' theorem. With this information, the processor is able to determine the scale of the map or chart in use. In addition, the processor is able to allow for any misalignment between the plotting board grid and that of the map or chart. In the general operation of the system, an aircraft may be assumed to travel in straight lines between selected points, and to travel at a more or less constant speed.

Considering the case of a route for an aircraft, it is a simple matter for the processor, having been supplied through the keyboard with known parameters such as speed, fuel consumption, fuel load and bank angle (or radius of turn), to determine variable factors such as the bearing between two points, fuel consumption (or fuel reserve), and time of flight. Such items as these are of great value to the pilot of the aircraft.

For example, by employing Pythagorus' theorem and conventional trigonometric identities, from the Cartesian map coordinate of two selected points along the route the equivalent polar coordinates representing the variable factor track heading may readily be calculated, as well as the distance between the points. Further, and as is set forth in the Katz et al U.S. Pat. No. 3,979,057, the basic equations relating time, distance, fuel consumption rate, and actual fuel consumption are well known. For example, Time=(Distance)/(Speed). (Fuel Consumption)=(Fuel Consumption Rate).times.(Time). For more sophisticated calculations, the bank angle and ground speed may be combined to provide radius of turn, using the formula; (Radius of Turn)=(Ground speed).sup.2 /(g tan .theta.); where g is the gravitational constant and .theta. is the bank angle.

In operation, once the two datum points have been defined as above, the known parameters are identified and applied to the processor via the keyboard K of the printer. After this it is simply a case of defining each selected point along the route, when the processor will calculate and cause the printer to provide a record of the various variable factors relating to each leg of the route.

Provision may be made for changing the chart or map, two new datum points being defined each time this is done.

The drawing shows several optional output peripheral devices driven by the processor. The portable store PS is a store in which the calculated information may be stored so that it may subsequently be transferred to the aircraft's own data processing system. This relieves the crew of the necessity to feed all the parameters into the aircraft system themselves. Similarly a tape cassette may be used in the same way, the tape being obtained from a cassette recorder CR. The visual display unit VDU is an alternative to the printer for providing a visual output, though the printer provides a permanent record. It is, of course, possible to arrange for the display to appear only on the VDU, providing a printed record only when any corrections have been effected using the VDU display. The portable store PS and tape cassette may also be used as input devices to program the processor.

FIG. 2 illustrates one possible modification to the system described above. It may be that the various turning points along a route are in fact preselected and their coordinates stored in part of the store ST. It is desirable to use these preselected points rather than arbitrary points selected by the operator, if the two are sufficiently close together. The block diagram shows detail within the processor and store blocks of FIG. 1. A temporary store TS and a fixed-point store FPS are both connected to a comparator CMP. Both of these stores have separate inputs. The temporary store TS is also connected to a store reader SR which operates on the fixed point store FPS. The output of the comparator controls a selector S which passes data from either the temporary store or the fixed-point store to a further store WS containing the points to be used by the processor in the necessary calculation.

The comparator CMP operates to compare the coordinates of points presented to it from the two stores TS and FPS. If the two points are close enough, that is within a predetermined distance of one another, the preselected point from store FPS will be used; otherwise the point from the temporary store will take preference.

In operation, therefore, each point fed into the processor by the operator causes the store reader SR to read out one at a time from store FPS the coordinates of all points in that store. The comparator then checks each one to see if it is close enough to the point fed in by the operator. The output of the comparator controls the selector S to apply the appropriate coordinates to store WS to enable the subsequent calculations to be performed.

As already mentioned the processor may be arranged to cater for chart scale changing or misalignment, and is able if necessary to convert coordinates between map grid and latitude/longitude values. The plotting board need not use the free cursor and inductive field system described above. Other plotting boards use transducers to measure movement along the two perpendicular axes of the board. Similarly, scanning techniques could be used with the aid of a light pen, as described in our U.S. Pat. No. 4,022,969.