WO2006021815A1

WO2006021815A1 - Navigation display system

Info

Publication number: WO2006021815A1
Application number: PCT/GB2005/050109
Authority: WO
Inventors: Andrew Douglas Munro; Jeffrey David Westbourne; Lincoln Scott Taylor
Original assignee: Bae Systems Plc
Priority date: 2004-07-14
Filing date: 2005-07-12
Publication date: 2006-03-02

Abstract

A navigation display system for a vehicle comprising processing means for storing a route plan, the route plan having a predetermined position and time at each point along its length, means for displaying the route plan, means for determining the current speed and position of the vehicle, means for calculating an intercept position such that, at the current vehicle speed from the current vehicle position, the vehicle regains the predetermined time and position of the route plan, and means for displaying one or both of the intercept position and an intercept path from the current vehicle position to the intercept position.

Description

NAVIGATION DISPLAY SYSTEM

This invention relates to the field of display systems, particularly to a navigation display system.

Many modern aircraft operations, or flights, are rigid choreographed operations, requiring precise arrival at a specified location. A delay due to, for example, a diversion can lead to an aircraft missing its timed arrival slot at that location. More aircraft are diverted to another destination or return to base having failed to accomplish their operation due to missing their timed slot than for other reasons such as failing to locate the destination. Each operation has a route plan comprising a route with position and time information at all points along the route. Hereinafter, the term 'route plan' should be understood to mean a predetermined path in position and time.

Modern aircraft particularly give rise to the need for pilot workload to be reduced. There are various activities required of a pilot whilst flying a complex aircraft and the pilot should be aware of all situations around him whilst flying the aircraft. Anything which shifts the attention of the pilot from these activities significantly increases the risk of the operation.

A number of factors in a normal flight, such as unfavourable weather conditions, can cause an aircraft to deviate from the route plan. It is then an attention-demanding task to calculate a new heading and speed in order to rejoin the route plan without missing the timed slot for arrival at the destination and without running out of fuel. In complicated aircraft the cockpit crew are often fully employed with other tasks; in less complicated, single-crew aircraft the pilot is occupied with all the tasks necessary to fly the aircraft, having to carry out the tasks of navigator as well as pilot.

Errors in computing remaining time and fuel parameters may result in serious consequences. During a flight the pilot needs to know whether the current speed will give rise to an early or late arrival at a specified location, and whether fuel is being consumed faster than had been anticipated. The calculations of time and fuel parameters must accommodate changes in speed due to weather, for example, and therefore must be constantly adjusted. On a typical operation the pilot periodically checks the current values of these parameters. Discrepancies between actual and planned time and fuel values can be compensated for either by altering the aircraft speed (within limits such as maximum aircraft speed, stall speed or fuel consumption rate) or by changing the course or arrival time to accommodate the actual values. Errors in arrival timing can result, for example, in a missed fuel rendezvous. Air traffic control, for example, requires precise timing and location of aircraft routes, particularly in busy corridors over certain areas to avoid collisions. The late arrival of an aircraft at an airport, for example, can cause the aircraft to miss its timed landing slot and require a holding pattern to be set up. This is becoming more of a concern as the number of civil aircraft in use increases.

Not only is there a risk of error in performing calculations, such calculations requiring a high degree of mental effort divert the attention of the pilot away from higher priority tasks such as terrain or aircraft avoidance. Accordingly, the present invention provides a navigation display system for a vehicle comprising processing means for storing a route plan, the route plan having a predetermined position and time at each point along its length, means for displaying the route plan, means for determining the current speed and position of the vehicle, means for calculating an intercept position such that, at the current vehicle speed from the current vehicle position, the vehicle regains the predetermined time and position of the route plan, and means for displaying one or both of the intercept position and an intercept path from the current vehicle position to the intercept position.

Such a navigation display system reduces the operator workload and provides a simple visual indication of the route plan and intercept position and path which does not require great mental capacity to view. The system allows an operator to maintain awareness of the current position in relation to the route plan and to view easily the course required to regain the route plan without effecting a change in speed. Use of the current speed enables the operator to visualise whether the vehicle speed needs to be altered in order to regain the predetermined route plan at an earlier or later point. The navigation display system could be easily built into existing vehicle systems. Preferably, the calculating means is adapted to establish two equations in velocity, distance and time, one for a leg of the route plan and one from a current position to the said leg, and to solve the equations simultaneously to identify at least one intercept position so that at the current speed the vehicle regains the route plan at the predetermined time and position according to the route plan.

Calculating means adapted to identify an intercept position in this way require little processing power and are easy and inexpensive to build.

If no solution is found, the calculating means should be adapted to repeat the process, establishing an equation in velocity, distance and time for a subsequent leg of the route and attempting to solve the equation simultaneously with that for a path from the current position to the subsequent leg.

In the event two or more intercept positions are identified, the calculating means is advantageously adapted to choose the intercept position closest to the current vehicle position.

Such an arrangement ensures that, when the vehicle deviates from the predetermined route plan, the vehicle returns to the route plan as soon as possible.

The display system preferably displays the predetermined time at at least one selected position on the route plan and may be adapted to calculate and display the amount of fuel consumed at least one selected position on the route plan.

There may be a requirement during an operation to visit waypoints before the final destination. It is beneficial for the predetermined time and/or fuel consumption at least one selected position on the route plan to be displayed in the same vicinity as the route plan as this enables the operator to view the information easily, with reduced time spent in the 'heads down' attitude. The operator/pilot can also compare easily the predetermined time or fuel consumption with the actual time or fuel consumption. The information allows the operator to compare current position and time coordinates and fuel levels with the predetermined values of these parameters. The operator can - A - then alter the vehicle course or speed if required in order to regain the route plan at the required point or to ensure there is enough fuel remaining to reach the destination. Additionally or alternatively, in the event that the vehicle proceeds at the current vehicle speed directly from the current position to the closest position on the route plan, ignoring the predetermined time of the route plan, the system is adapted to calculate and display the time of arrival or the expected amount of fuel consumed at at least one selected position on the route plan.

Advantageously, the navigation display system is adapted to calculate and display the amount of fuel consumed, at at least one selected position on the route plan, in the event that the vehicle proceeds from the current position to the intercept position and then resumes travel along the route plan.

The operator needs to bear in mind the consequences of deviations from the route plan, and particularly the implications such deviations have on fuel consumption. It is often more important to reach the destination on time than it is to visit each position on the route plan. It is therefore useful for an operator to have a clear indication of the expected fuel consumption if the route plan has to be abandoned in favour of proceeding directly to the destination.

The calculating means may take into account limiting vehicle and/or route plan characteristics and, in use, be adapted to discard any intercept positions which do not comply with these characteristics.

Vehicles are limited in possible manoeuvres by their ability to sustain sharp turns or their rate of fuel consumption, for example. The route plan may be such that topology restricts the intercept paths possible. It is therefore advantageous for the calculating means to take these limitations into account and only provide an intercept position which is suitable and/or practicable.

The navigation display system preferably comprises a visual and/or audible prompt actuated when the intercept position coincides with the destination of the route plan. Once the route plan has been deviated from, there is a point at which the course will need to be altered to proceed directly towards the destination, in order to reach the destination during the planned time slot. If the intercept position lies beyond the destination then the prompt should also be actuated, and the prompt would preferably continue in actuation as the intercept position moves along the route plan beyond the destination. Such a warning is particularly beneficial when, for example, an operator is distracted by a situation requiring diversionary steps.

Preferably, the navigation display system is integrated with an automatic steering device and/or autothrottle.

This enables the automatic steering device and/or autothrottle to act on information provided by the navigation display system without requiring operator input, allowing the operator to attend to other flight activities.

The invention will now be described by way of example and with reference to the accompanying drawings in which:

Figure 1 is a schematic view of an embodiment of a navigation display system in accordance with the invention.

Figure 1 shows a navigation display system 2 in accordance with the invention for use in an aircraft of other vehicle. Display means 4, such as a CRT or LCD screen, is connected to a computer 6 and displays a map 8 illustrating the path of a route plan 10 including waypoints 12 and a destination 14. The predetermined time of arrival of the aircraft at the waypoints 12 and destination 14, the expected fuel consumed during travel to the waypoints 12 and destination 14, the planned amount of fuel remaining at the end of the operation, and any other pertinent flight information is either inputted and stored in or computed by the computer 6. A navigation system 16, such as a global positioning system, provides information indicative of the navigational position of the aircraft. The aircraft position is provided to the computer 6 and a symbol 18 is used to indicate the position of the aircraft on the map 8. An information window 20 is displayed on the display means 4, with further information for the pilot such as the planned time of arrival 26a at the destination 14.

A fuel control system 22 provides information indicative of the amount of fuel remaining or the amount of fuel consumed which is displayed in the information window 20. A clock 24 provides the current or operation elapsed time.

When an aircraft deviates from its route plan 10 due to, for example, bad weather, the pilot must decide when and how to return to the route plan 10. Returning to the route plan 10 by the most direct path may take the aircraft away from the destination 14 and thereby delay the aircraft further within the timed arrival slot. Increasing speed to make up time increases fuel consumption and therefore may not be an option. Further factors may delay the pilot returning to the route plan 10. The information window 20 displays the predetermined time of arrival

26a at the destination 14, the time of arrival 28a if the aircraft travelled directly to the destination 14 at its current speed and the time of arrival 30a if the aircraft rejoined the route plan 10 directly and followed the route plan 10 to the destination 14 at its current speed. Additional information, for example the expected amount of fuel remaining 28b, 30b and the length of time 28c, 30c by which the aircraft is early or late in each case, is also displayed.

The provision of a navigation display system with route, time and fuel information in a concise, expedient manner enables the pilot to maintain situation awareness without sacrificing safety. The navigation display system 2 provides the pilot with a clear indication of the current position 18 in relation to the route plan 10. Having been diverted from the route plan 10, the pilot needs to return to the predetermined route path at the correct point in position-time space to regain the route plan 10. The navigation display system 2 calculates the point at which the route plan 10 would be intercepted if the aircraft headed to the route plan 10 whilst maintaining the current speed. It is preferable to return to the route plan 10 as soon as possible in order to avoid missing planned rendezvouses at waypoints 12. The navigation display system 2 therefore establishes equations in velocity, distance and time, one for a leg of the route plan following the point of the predetermined route path closest to the current position and one for a path from the current position to that leg of the route plan. The navigation display system 2 then attempts to solve the equations simultaneously. If a solution cannot be found, the process is repeated with an equation established for the following leg of the route plan.

Once a solution has been found, an intercept marking 32 is displayed on the route plan at the point of intersection. The intercept marking 32 is joined to the current position symbol 18 by an intercept line 34, making it easier for the pilot to spot the point at which the route plan 10 will be intersected.

The pilot may decide, on viewing the position of the intercept marking 32 along the route plan 10, that it would be preferable to regain the predetermined path of the route plan at an earlier or later point. The navigation display system 2 aids the pilot in visualising the route and deciding whether it is necessary to alter the speed of the aircraft to regain the predetermined path at an earlier or later point or to ensure, for example, that the destination 14 is reached within the timed arrival slot or that the amount of fuel consumed is not too great. An aircraft failing to reach the destination at the timed arrival slot may, for example, have to be diverted. The system gives the pilot a continuous and up-to-date visual indication of time and fuel consumption, providing a display indicative of the difference between the planned and actual consumption of fuel. The system therefore enables a pilot to be aware of deviations from the route plan throughout a flight, so that alterations can be made to the course and speed of the aircraft to ensure the object of the flight is accomplished.

Vehicle or flight characteristics such as maximum or minimum speed, maximum sustainable G-turn, fuel consumption or altitude range can be taken into account by the system when calculating a path from the current position to rejoin the route plan. Unsuitable intercept paths are thereby rejected by the system, which then displays an intercept path realisable by the aircraft. Having deviated from the route plan, there will at some point be a time when it is necessary for the pilot to fly directly to the destination 14 in order to arrive within the timed arrival slot. The navigation display system 2 gives the pilot a go-to-destination prompt, such as a flashing light, indicating the necessity to fly directly to the destination 14. A pilot engrossed in taking diversionary steps is unable to spend time in a heads-down attitude and is therefore unlikely to spot a visual indication on the display window. The navigation display system 2 therefore also provides an audible go-to-destination prompt. The go- to-destination prompt may additionally or alternatively comprise any other indicator means which can be sensed by the pilot.

Having now described various embodiments of the invention, numerous modifications will become apparent to the skilled person. For instance, the display means may comprise any type of display unit for displaying information to a pilot. Further, the system may be used with any type of vehicle wherein information indicative of actual time of arrival and/or fuel consumption compared to the planned time of arrival and/or fuel consumption is desired.

It will be understood that rather than displaying the planned fuel consumed at a selected point along the route the planned amount of fuel remaining may be displayed if this information would be more useful. The difference between the planned fuel consumption and the actual fuel consumption may also be displayed. If the amount of fuel remaining falls below a certain level the system may give warnings indicative that the vehicle has only just sufficient fuel to return to a particular point, or that the vehicle has sufficient fuel with a predetermined margin to return to the point. The go-to-destination prompt may alternatively or additionally be coupled to the fuel control system to give a prompt when, for example, it is necessary to go to the destination in order to complete the mission with enough fuel.

The system may change the colour of the intercept line 34 to indicate if the destination will not be reached within the timed arrival slot. While the route plan 10 may show the predetermined route path as consisting of straight legs, the navigation display system 2 may take into account that the aircraft will not perform a turn in such a manner. This may be done, for example, by assuming that the first part of a leg is flown at a different speed.

When the aircraft is pointing away from the destination, the navigation display system may also model the turn required given a suitable rate of turn for the aircraft and may take into account factors such as wind direction and speed.

The navigation display system may take into account the turn required at the intercept point for the aircraft to regain the route plan in order to calculate a smoother intercept. The route plan may be in two or three spatial dimensions. Topographical information may also be incorporated to ensure the path taken to regain the route plan avoids hazards, for example mountains.

Claims

1. A navigation display system for a vehicle comprising:

- processing means for storing a route plan, the route plan having a predetermined position and time at each point along its length; - means for displaying the route plan;

- means for determining the current speed and position of the vehicle;

- means for calculating an intercept position such that, at the current vehicle speed from the current vehicle position, the vehicle regains the predetermined time and position of the route plan, and - means for displaying one or both of the intercept position and an intercept path from the current vehicle position to the intercept position.

2. A navigation display system according to Claim 1 wherein the calculating means is adapted to: - establish two equations in velocity, distance and time, one for a leg of the route plan and one from a current position to the said leg, and

- solve the equations simultaneously to identify at least one intercept position so that at the current speed the vehicle regains the route plan at the predetermined time and position according to the route plan.

3. A navigation display system according to Claim 2 wherein, in the event two or more intercept positions are identified, the calculating means is adapted to choose the intercept position closest to the current vehicle position.

4. A navigation display system according to any preceding claim adapted to display the predetermined time at at least one selected position on the route plan.

5. A navigation display system according to any preceding claim adapted to calculate and display the amount of fuel consumed at at least one selected position on the route plan.

6. A navigation display system according to any preceding claim adapted to calculate and display the amount of fuel consumed at at least one selected position on the route plan, in the event that the vehicle proceeds from the current position to the intercept position and then resumes travel along the route plan.

7. A navigation display system according to any preceding claim wherein the calculating means takes into account limiting vehicle and/or route plan characteristics and, in use, is adapted to discard any intercept positions which do not comply with these characteristics.

8. A navigation display system according to any preceding claim wherein the route plan has a destination at a predetermined position and time, the system further comprising a visual and/or audible prompt actuated when the intercept position coincides with the destination.

9. A navigation display system according to any preceding claim integrated with an automatic steering device and/or autothrottle.