NL2009978C2

NL2009978C2 - System and method for determining an instrument approach procedure for an aircraft.

Info

Publication number: NL2009978C2
Application number: NL2009978A
Authority: NL
Inventors: Hendrik Haverdings
Original assignee: Stichting Nationaal Lucht En Ruimtevaartlaboratorium
Priority date: 2012-12-13
Filing date: 2012-12-13
Publication date: 2014-06-16
Also published as: WO2014092563A1

Abstract

A system for determining an instrument approach procedure for an aircraft comprises a database system containing terrain data and obstacle data, an input device onboard the aircraft for selecting a target position, a display device onboard the aircraft for displaying information to the pilot, and a processor onboard the aircraft. The processor determines, on the basis of the selected target position,a final approach path segment and a missed approach path segment. The final approach path segment begins at a final approach waypoint and ends at a missed approach point for deciding whether the aircraft may continue to a landing position on the ground or a missed approach procedure is started. The missed approach path segment begins at the missed approach point and ends at a higher altitude. A memory contains obstacle clearance surface data, on the basis of which, for each of the final approach path segment and the missed approach path segment, an obstacle clearance surface is defined that extends at a pre-determined orientation and at a pre-determined distance below said path segment. The processor determines an obstacle clearance altitude (OCA) for the instrument approach procedure as the lowest altitude at which any obstacle identified by the terrain data and obstacle data in the database system does not penetrate the obstacle clearance surfaces in the final approach path segment and the missed approach path segment. The system is configured to display the obstacle clearance altitude (OCA) on the display device.

Description

Title: System and method for determining an instrument approach procedure for an aircraft

The invention relates to a system for determining an instrument approach procedure for an aircraft, the system comprising: 5 - a database system containing terrain data and obstacle data, - an input device onboard the aircraft for selecting a target position, - a display device onboard the aircraft for displaying information to a pilot of the aircraft, - a processor onboard the aircraft, 10 the processor being connected to the input device and to the display device, and the processor being configured to determine an instrument approach procedure for the aircraft on the basis of the selected target position and the terrain data and obstacle data from the database.

The aircraft may be a rotary-wing aircraft, for example a helicopter, or a fixed-wing 15 aircraft, such as an airplane.

EP 1198720 discloses a system that utilizes a global positioning system for creating an approach to a position on the ground from a location above the ground. When the pilot wants to land the aircraft, the pilot uses an input device to enter coordinates or to select a desired point on the ground displayed on a digital moving map as well as other information 20 such as desired landing direction. Thereafter, a processor onboard the aircraft creates a precision approach for the aircraft to that position on the ground from the in-flight position of the aircraft. The approach includes direction, elevation, and distance to the position on the ground. The approach may also include altitude penalties for obstacles and elevation changes in the terrain. The system includes a real-time mapping device, such as a Doppler 25 radar or a diode laser, that identifies obstacles in the approach. The identified obstacles are then compared to obstacle data in a database to verify the validity of the obstacle data in the database. This verification allows the system to modify the approach if necessary based upon the identified obstacles.

This known system can only be used when the aircraft is already in the vicinity of the 30 landing position on the ground. In addition, this system is not able to assist the pilot in case of a missed approach, for example, when the pilot loses visual contact with the runway at a late stage in the approach, e.g. when an unexpected patch of ground fog obstructs the pilot’s visibility.

It is an object of the invention to provide an improved system for determining an 35 approach procedure for an aircraft.

This object is achieved according to the invention by a system for determining an instrument approach procedure for an aircraft, the system comprising: 2 - a database system containing terrain data and obstacle data, - an input device onboard the aircraft for selecting a target position, - a display device onboard the aircraft for displaying information to a pilot of the aircraft, 5 - a processor onboard the aircraft, the processor being connected to the input device and to the display device, and the processor being configured to determine an instrument approach procedure for the aircraft on the basis of the selected target position and the terrain data and obstacle data from the database, 10 wherein the processor is configured to determine, on the basis of the selected target position, a final approach path segment and a missed approach path segment of the instrument approach procedure, the final approach path segment being defined by a flight path that begins at a final approach waypoint at a final approach waypoint altitude and ends at a 15 missed approach point, at a lower altitude than the final approach waypoint altitude, for deciding whether the aircraft may continue to a landing position on the ground or a missed approach procedure is started, and the missed approach path segment being defined by a flight path that begins at the missed approach point and ends at a higher altitude than the altitude of the missed approach point, which missed approach path segment is followed by 20 the aircraft when it is decided at the missed approach point that the missed approach procedure is started, wherein, for example, the missed approach path segment is a substantially straight flight path, and the system comprises a memory containing obstacle clearance surface data, on the basis of which, for each of the final approach path segment and the missed approach path 25 segment, at least one obstacle clearance surface is defined that extends at a pre-determined orientation and at a pre-determined distance below said path segment, and the processor is configured to determine an obstacle clearance altitude (OCA) for the instrument approach procedure as the lowest altitude at which any obstacle identified by the terrain data and obstacle data in the database system does not penetrate any of the obstacle 30 clearance surfaces in the final approach path segment and the missed approach path segment, and the system is configured to display the obstacle clearance altitude (OCA) on the display device.

According to the invention, the system determines the instrument approach procedure 35 onboard the aircraft. The final approach path segment and the missed approach path segment are determined by calculating the coordinates of the final approach waypoint and the coordinates of the missed approach point. Incidentally, the final approach waypoint is a 3 waypoint or “fix”, whereas the missed approach point may be a waypoint or “fix” or may not be a waypoint or “fix” depending on the type of approach procedure. However, the missed approach point is a point that is calculated by the system according to the invention in any type of approach procedure. In the process, the processor may also determine the course or 5 direction of the missed approach path segment. After the final approach path segment and the missed approach path segment have been determined, the obstacle clearance altitude (OCA) is calculated by analysing, for each of the final approach path segment and the missed approach path segment, if any obstacle identified by the terrain data and obstacle data in the database system penetrates the obstacle clearance surface below said approach 10 path segment. The dimensions, orientation and shape of the obstacle clearance surfaces may vary along the final approach path segment and the missed approach path segment.

For each of the final approach path segment and the missed approach path segment, the dimensions, orientation and shape of the obstacle clearance surfaces, including the minimum obstacle clearance (MOC) distance, i.e. the vertical distance between the obstacle clearance 15 surface and the final approach path segment or the missed approach path segment situated above it, are stored in the memory. The parameters defining the obstacle clearance surfaces depend on the type of instrument approach procedure. If any obstacle penetrates the obstacle clearance surface at any point along the final approach path segment or the missed approach path segment, the obstacle clearance altitude (OCA) is increased by the processor 20 in such a manner that the obstacle clearance surface is situated just above the obstacle or obstacles. Thus, the obstacle clearance altitude (OCA) is the lowest altitude at which the obstacle clearance surface is not penetrated by any obstacle anywhere along the final approach path segment and the missed approach path segment. The calculated obstacle clearance altitude (OCA) is displayed on the display device to the pilot. Of course, other 25 information from the calculated instrument approach procedure may also be displayed on the display device to the pilot, for example the coordinates of the final approach waypoint (final approach fix) and, optionally, coordinates of other waypoints or fixes.

The system according to the invention does not require any ground-based infrastructure. Also, the system according to the invention can be used to determine the 30 instrument approach procedure at any moment in time, for example, the pilot can enter the desired target position when the aircraft is in-flight at a considerable distance therefrom. It is even possible for the desired target position to be entered already before take-off. Furthermore, the instrument approach procedure determined by the system according to the invention provides for a missed approach path segment. The obstacle clearance altitude 35 (OCA) is determined by taking into consideration not only the final approach path segment but also the missed approach path segment, which increases safety.

4

The instrument approach procedure determined by the system according to the invention can be a standard procedure laid down by definitions and descriptions of the International Civil Aviation Organization (“ICAO”), for example a procedure referred to as “Point-in-Space” procedure (“PinS”) or a procedure referred to as “Localizer-Precision with 5 Vertical guidance” procedure (“LPV”), sometimes also referred to as “Approach Procedure with Vertical guidance” procedure (“APV”).

When the system according to the invention is configured to determine a PinS procedure, the target position is a position above the ground, and the missed approach point is a waypoint or “fix” that is defined by the target system, i.e. the same waypoint as the PinS. 10 Preferably, the system is configured to display the missed approach point on the display

device. In this latter case, the processor is not only configured to calculate the coordinates of the missed approach point in the procedure, but the missed approach point is also presented to the pilot as a waypoint or “fix” on the display device. After the aircraft has reached the missed approach point, the pilot either continues to proceed visually to a suitable landing 15 position on the ground or the pilot starts the missed approach procedure. In the PinS

procedure, the missed approach path segment may be defined by a substantially straight line. The PinS procedure is only applicable to rotorcraft, such as helicopters.

According to the invention, with the PinS procedure, the obstacle clearance surface of the final approach segment may comprise a primary area and two secondary areas, wherein 20 the primary area of the final approach segment is oriented substantially horizontally and extends at a minimum obstacle clearance (MOC) distance below the final approach segment, and wherein each secondary area of the final approach segment slopes upwards from a longitudinal edge of the primary area of the final approach segment on either side of said primary area. Likewise, it is possible that the obstacle clearance surface of the missed 25 approach segment comprises a primary area and two secondary areas, wherein the primary area of the missed approach segment is oriented substantially horizontally and extends at a minimum obstacle clearance (MOC) distance below the missed approach segment, and wherein each secondary area of the missed approach segment slopes upwards from a longitudinal edge of the primary area of the missed approach segment on either side of said 30 primary area. Thus, with the system according to the invention, an instrument approach procedure in accordance with PinS can be calculated onboard the aircraft, and the obstacle clearance altitude (OCA) can be determined by taking into consideration both the final approach path segment and the missed approach path segment of said PinS procedure.

When the system according to the invention is configured to determine an LPV 35 procedure, the target position is the landing position on the ground, and the missed approach point is situated on a substantially straight line from the final approach waypoint to the landing position on the ground. Preferably, the system is configured to display the selected 5 target position, i.e. the landing position on the ground on the display device. In this case, the missed approach point is not a waypoint or “fix” that is presented on the display device to the pilot. The missed approach point is defined by a pre-determined decision altitude. At the decision altitude, the pilot decides either to continue and land on the selected landing 5 position on the ground or to start the missed approach procedure. The LPV procedure can be applied both to rotary-wing and fixed-wing aircraft.

With an LPV procedure, the obstacle clearance surfaces may be defined in a runway coordinate system. The landing position on the ground is situated on a runway having a centre line, and the runway coordinate system has an origin situated at a runway threshold of 10 the runway, and mutually perpendicular axes X, Y and Z extending from the origin, wherein the Z-axis extends vertically, wherein the X-axis extends parallel to the centre line of the runway, towards the final approach waypoint, and wherein the Y-axis extends transversely to the centre line of the runway according to the right-hand rule. In such a runway coordinate system, the final approach path segment extends in the X-Z plane.

15 According to the invention, with the LPV procedure, the obstacle clearance surface of the final approach path segment may comprise at least one central surface, which is referred to as W-surface, which has a centre line that extends in the X-Z plane, and which W-surface extends at right angles to the X-Z plane, and which W-surface is inclined with respect to the X-Y plane. As a result, the W-surface is also inclined with respect to the Y-Z plane. The W-20 surface is symmetrical with respect to the X-Z plane. In most cases, the W-surface is substantially rectangular. The W-surface slopes downwards as seen in the direction of the runway.

It is also possible according to the invention that the obstacle clearance surface of the final approach path segment comprises two central surfaces that each have a centre line that 25 extends in the X-Z plane, which are referred to as W-surface and W’-surface, respectively, wherein the W’-surface is a continuation of the w-surface as seen in the direction of the runway, and which W- and W’-surfaces each extend at right angles to the X-Z plane, and which surfaces are inclined with respect to the X-Y plane at different angles (and thus the W-and W’-surfaces are also inclined with respect to the Y-Z plane at different angles). The W-30 surface and the W’-surface are aligned with each other and each slope downward as seen in the direction of the runway. For example, the W’-surface that is situated closer to the runway extends at an angle with respect to the X-Y plane that is greater than the W-surface that is situated further away from the runway.

In an embodiment of the invention, the W-surface comprises two opposed longitudinal 35 edges on either side of said W-surface, wherein the obstacle clearance surface of the final approach segment comprises two side surfaces, which are each referred to as X-surface, and which X-surfaces each slope upward from the longitudinal edges of the W-surface at an 6 angle with respect to the X-Y plane, to the X-Z plane, and also to the Y-Z plane. The X-surfaces each slope downward as seen in the direction of the runway. At the same time, each X-surface slopes upward from the respective longitudinal edge of the W-surface. When the obstacle clearance surface of the final approach path segment also includes a W’-5 surface, each of the X-surfaces also slopes upward from the longitudinal edges of the W’-surface. As seen in a cross-section parallel to the Y-Z plane, the W-surface and the adjacent X-surfaces define the shape of a trough. The same applies to the W’-surface and the adjacent X-surfaces.

According to the invention, with the LPV procedure, the obstacle clearance surface of 10 the missed approach path segment may also comprise at least one central surface, which is referred to as Z-surface, which has a centre line that extends in the X-Z plane, and which Z-surface extends at right angles to the X-Z plane, and which Z-surface is inclined with respect to the X-Y plane (and thus also to the Y-Z plane). The Z-surface of the missed approach segment is symmetrical with respect to the X-Z plane, and preferably, the Z-surface has the 15 shape of a isosceles trapezium or a plurality of isosceles trapeziums that are aligned with each other. The Z-surface slopes upward as seen in the direction away from the runway.

Furthermore, the Z-surface comprises two opposed longitudinal edges on either side of said Z-surface, said longitudinal edges being non-parallel when the Z-surface has the shape of a isosceles trapezium, wherein the obstacle clearance surface of the missed 20 approach segment comprises two side surfaces, which are each referred to as Y-surface, and which Y-surfaces each slope upward from the longitudinal edges of the Z-surface at an angle with respect to the X-Y plane, to the X-Z plane, and also to the Y-Z plane. The Y-surfaces each slope upward as seen in the direction away from the runway. At the same time, each Y-surface slopes upward from the respective longitudinal edge of the Z-surface. 25 As seen in a cross-section parallel to the Y-Z plane, the Z-surface and the adjacent Y- surfaces also define the shape of a trough. The Y-surfaces may also extend along the final approach segment adjacent to the longitudinal edges of the X-surfaces.

In a preferred embodiment of the system according to the invention, the processor is configured to determine an initial approach path segment and/or an intermediate path 30 segment of the instrument approach procedure, the initial approach path segment being defined by a flight path that begins at an initial approach waypoint and ends at an intermediate waypoint, and the intermediate path segment being defined by a flight path that begins at the intermediate waypoint and ends at the final approach waypoint, wherein the initial approach waypoint and the intermediate waypoint are preferably at the same altitude 35 as the final approach waypoint altitude, and wherein, on the basis of the obstacle clearance surface data, for each of the initial approach path segment and/or the intermediate path segment, at least one obstacle clearance surface is defined that extends at a pre-determined 7 orientation and at a pre-determined distance below said path segment, and the processor is configured to determine the obstacle clearance altitude (OCA) for the instrument approach procedure as the lowest altitude at which any obstacle identified by the terrain data and obstacle data in the database system does not penetrate any of the obstacle clearance 5 surfaces in the final approach path segment and the missed approach path segment and the initial approach path segment and/or the intermediate path segment.

In this case, the system according to the invention not only determines the final approach path segment and the missed approach path segment, but also the intermediate path segment, and preferably also the initial approach path segment. In most instrument 10 approach procedures, the procedure includes at least one waypoint or “fix” ahead of the final approach waypoint. Usually, the instrument approach procedure includes two additional waypoints or “fixes” ahead of the final approach waypoint, i.e. the intermediate waypoint (intermediate fix) and the initial approach waypoint (initial approach fix). However, some instrument approach procedures do not determine the initial approach waypoint, i.e. they 15 only calculate one waypoint or “fix” ahead of the final approach waypoint. Furthermore, even if both the intermediate fix and the initial approach fix are determined, the pilot may decide to disregard the initial approach fix and fly directly to the intermediate fix.

The intermediate path segment is determined by calculating the coordinates of the intermediate fix. The initial approach path segment is determined by calculating the 20 coordinates of the initial approach fix. On the basis of the obstacle clearance data stored in the memory of the system, an obstacle clearance surface is defined for each of the intermediate path segment and/or the initial approach path segment. Thus, the processor calculates the obstacle clearance altitude (OCA) for the instrument approach procedure by taking into consideration obstacles in the intermediate path segment and/or initial approach 25 segment as well, which is advantageous for safety. In this case, the system may be configured to display on the display device not only the obstacle clearance altitude (OCA), but also, for example the final approach fix, the initial approach fix and/or the intermediate fix coordinates.

The system according to the invention takes into consideration any obstacles along 30 the initial approach path segment and/or along the intermediate path segment by assessing obstacle clearance surfaces associated with said path segments. Preferably, the obstacle clearance surface of the initial approach path segment comprises a primary area and two secondary areas, wherein the primary area of the initial approach path segment is oriented substantially horizontally and extends at a minimum obstacle clearance (MOC) distance 35 below the initial approach path segment, and wherein each secondary area of the initial approach path segment slopes upwards from a longitudinal edge of the primary area of the initial approach path segment on either side of said primary area. Likewise, it is preferred that 8 the obstacle clearance surface of the intermediate path segment comprises a primary area and two secondary areas, wherein the primary area of the intermediate path segment is oriented substantially horizontally and extends at a minimum obstacle clearance (MOC) distance below the intermediate path segment, and wherein each secondary area of the 5 intermediate path segment slopes upwards from a longitudinal edge of the primary area of the intermediate path segment on either side of said primary area. Obstacle clearance surfaces of this type result in high levels of safety.

Such obstacle clearance surfaces may be configured to comply with ICAO regulations. For example, the minimum obstacle clearance (MOC) distance is 246 ft in the 10 final approach path segment (with the PinS procedure), 500 ft in the intermediate path segment and 1000 ft in the initial approach path segment. The width of the primary area may be, for example, between 2-4 nm. The width of the primary area may vary along the path segments. The two secondary areas are situated on either side of the primary area.

In an embodiment according to the invention, the database system contains 15 instrument approach procedure data of a plurality of different instrument approach procedures, such as the PinS procedure and/or the LPV procedure, wherein the input device is configured to select an instrument approach procedure from said plurality of instrument approach procedures, i.e. to allow a pilot to select a desired procedure from the plurality of different instrument approach procedures, and wherein the system is configured to determine 20 the selected instrument approach procedure. In this case, the pilot may select the type of instrument approach procedure, for example Pins or LPV. On the basis of the selected instrument approach procedure, the system according to the invention calculates the coordinates of the final approach waypoint and the missed approach point as well as the obstacle clearance altitude (OCA) and displays the relevant parameters to the pilot. For 25 example, with the PinS procedure, the coordinates of the final approach waypoint, the coordinates of the missed approach point (i.e. the PinS waypoint) and the obstacle clearance altitude (OCA), and optionally other data, may be depicted on the display device.

In an embodiment according to the invention, the input device is configured to select an approach glide slope and/or an approach course or direction, at least for the final 30 approach path segment, and/or an initial altitude, wherein the processor is configured to calculate the final approach waypoint and the missed approach point on the basis of the selected approach glide slope and/or the selected approach course and/or the selected initial altitude. For example, the system according to the invention asks the pilot not only to enter the target position, but also the desired approach glide slope, the desired approach course 35 and the desired initial altitude. Usually, the initial altitude defines the final approach waypoint altitude. On the basis of the selected target position, the selected approach glide slope, the selected approach course and the selected initial altitude , the system according to the 9 invention calculates the coordinates of the final approach waypoint and the coordinates of the missed approach point. Thus, the final approach path segment can be determined using the input from the pilot. The missed approach path segment starts from the missed approach point and is also determined by the system, for example by autonomously selecting a course 5 or direction for the missed approach path and specifying an altitude to which the aircraft has to climb. Instead, the system may select a missed approach holding waypoint to which the aircraft should be directed during the missed approach procedure. It should be noted that the system may also autonomously select a desired approach glide slope and/or a desired approach course and/or a desired initial altitude, wherein the autonomously selected values 10 are used to calculate the coordinates of the final approach waypoint and the coordinates of the missed approach point.

In a preferred embodiment according to the invention, the input device is configured to select an optimization function for determining, after an obstacle clearance altitude (OCA) of a first instrument approach procedure has been determined by the processor, a second, 15 alternative instrument approach procedure, wherein the processor is configured to modify the selected approach glide slope and/or the selected initial altitude and/or the selected approach course, after the optimization function has been selected, and to determine a modified final approach path segment and a modified missed approach path segment, and, optionally, a modified initial approach path segment and/or a modified intermediate path 20 segment, on the basis of the selected target position and the modified approach glide slope and/or the modified initial altitude and/or the modified approach course, and wherein, on the basis of the obstacle clearance surface data, for each of said modified path segments, at least one obstacle clearance surface is defined that extends at a pre-determined orientation and at a pre-determined distance below said modified path segments, and the processor is 25 configured to determine a modified obstacle clearance altitude (modified OCA) for the second, alternative instrument approach procedure as the lowest altitude at which any obstacle identified by the terrain data and obstacle data in the database system does not penetrate any of the obstacle clearance surfaces in said modified path segments, and wherein the processor is configured to compare the modified obstacle clearance altitude 30 (modified OCA) with the obstacle clearance altitude (OCA) of the first instrument approach procedure. The modified obstacle clearance altitude (modified OCA) may be displayed on the display device.

Thus, the system determines the obstacle clearance altitude (OCA) of a first instrument approach procedure, which is displayed on the display device. The obstacle 35 clearance altitude (OCA) of the first instrument approach procedure calculated by the system may be considered too high, for example a cloud base is situated below the obstacle clearance altitude (OCA). When the pilot selects the optimization function, the system 10 analyses if the calculated obstacle clearance altitude (OCA) can be decreased by changing the glide scope for the final approach path segment and/or the initial altitude and/or the approach course that have been selected by the pilot. The modified glide slope and/or the modified initial altitude lie within a predetermined operational range. As a result, an obstacle 5 that penetrated one of the obstacle clearance surfaces associated with the calculated first instrument approach procedure may no longer penetrate. Thus, when the optimization function is selected, an attempt is made by the system to generate a second, alternative instrument approach procedure to the selected target position having a lower obstacle clearance altitude (OCA). If the system arrives at a second, alternative instrument approach 10 procedure having a lower obstacle clearance altitude (modified OCA), the latter is displayed on the display device, preferably together with the coordinates of the modified final approach waypoint, and preferably also together with the coordinates of the modified intermediate waypoint and/or the modified initial approach waypoint. If the modified obstacle clearance altitude (modified OCA) of the second, alternative instrument approach procedure is still not 15 satisfactory to the pilot, he may then decide to select another target position or another approach procedure.

In an embodiment according to the invention, the processor is configured to determine the obstacle clearance altitude (OCA) by: - defining an estimated obstacle clearance altitude that is equal to the minimum 20 obstacle clearance (MOC) distance at the missed approach point, - determining if any obstacle identified by the terrain data and obstacle data in the database system penetrates any of the obstacle clearance surfaces, and, if it is determined that no obstacles penetrate the obstacle clearance surfaces, determine that the estimated obstacle clearance altitude is the minimum 25 obstacle clearance altitude (OCA), and if it is determined that one or more obstacles penetrate the obstacle clearance surfaces, increase the estimated obstacle clearance altitude so that said obstacles no longer penetrate any of the obstacle clearance surfaces, and determine that the increased estimated obstacle clearance altitude is the 30 obstacle clearance altitude (OCA).

Thus, the system is configured to determine a first estimate of the obstacle clearance altitude by ignoring any obstacles. Then, said first estimate is checked against the obstacles identified by the terrain data and obstacle data in the database system. If one or more obstacles penetrate the obstacle clearance surfaces, said first estimate is increased so that 35 said obstacles no longer penetrate the obstacle clearance surfaces. This results in the obstacle clearance altitude (OCA) that is displayed on the display device.

11

In this case, it is possible that the processor is configured to determine, if it is determined that one or more obstacles penetrate the obstacle clearance surface in the missed approach segment, a height by which said obstacles project into the obstacle clearance surface of the missed approach segment, and wherein the processor is configured 5 to increase the estimated obstacle clearance altitude by said height so that said obstacles no longer penetrate the obstacle clearance surface in the missed approach segment. Thus, obstacles in the missed approach path segment are avoided by increasing the obstacle clearance altitude by the height by which said obstacles penetrate into the obstacle clearance surface. Thus, said obstacle clearance altitude (OCA) defines a safe altitude for 10 the missed approach path segment.

The invention also relates to a method for determining an instrument approach procedure for an aircraft, wherein use is made of a system comprising: - a database system containing terrain data and obstacle data, - an input device onboard the aircraft for selecting a target position, 15 - a display device onboard the aircraft for displaying information to a pilot of the aircraft, - a processor onboard the aircraft, the processor being connected to the input device and to the display device, and the method comprises: 20 - determining by the processor an instrument approach procedure for the aircraft on the basis of the selected target position and the terrain data and obstacle data from the database system, wherein the processor determines, on the basis of the selected target position, a final 25 approach path segment and a missed approach path segment of the instrument approach procedure, the final approach path segment being defined by a flight path that begins at a final approach waypoint at a final approach waypoint altitude and ends at a missed approach point, at a lower altitude than the final approach waypoint altitude, for deciding whether the aircraft may continue to a landing position on the ground or a missed approach procedure is 30 started, and the missed approach path segment being defined by a flight path that begins at the missed approach point and ends at a higher altitude than the altitude of the missed approach point, which missed approach path segment is followed by the aircraft when it is decided at the missed approach point that the missed approach procedure is started, and the system comprises a memory containing obstacle clearance surface data, on the 35 basis of which, for each of the final approach path segment and the missed approach path segment, at least one obstacle clearance surface is defined that extends at a pre-determined orientation and at a pre-determined distance below said path segment, and 12 the processor determines an obstacle clearance altitude (OCA) for the instrument approach procedure as the lowest altitude at which any obstacle identified by the terrain data and obstacle data in the database system does not penetrate any of the obstacle clearance surfaces in the final approach path segment and the missed approach path segment, and 5 the obstacle clearance altitude (OCA) is displayed on the display device.

The method according to the invention has the same advantages as the system according to the invention as described above. In addition, one or more of the features of the system according to the invention as described above, and also one or more of the features of the system claims, individually or in any combination of features, may be applied to the 10 method according to the invention.

The invention will now be explained in more detail, only by way of example, with reference to the figures.

Figure 1 is a schematic illustration of a first instrument approach procedure for an aircraft that is determined by the system according to the invention.

15 Figure 2 is a schematic illustration of a second instrument approach procedure for an aircraft that is calculated by the system according to the invention.

Figure 3 is a block diagram of a system for determining an instrument approach procedure for an aircraft according to an exemplary embodiment of the invention, wherein the system is integrated in the flight management system (FMS) of an aircraft.

20 Figure 4 is a cross-section according to IV-IV in figure 1.

Figure 5 is a schematic top view of obstacle clearance surfaces in the final approach segment and the missed approach segment in the instrument approach procedure shown in figure 2.

Figure 6 is a schematic side view of the obstacle clearance surfaces shown in figure 25 5.

Figure 7 is a schematic top view of a third instrument approach procedure for an aircraft that is calculated by the system according to the invention.

Figure 8 is a cross-section according to VIII-VIII in figure 7.

The system for determining an instrument approach procedure is installed onboard an 30 aircraft. The aircraft can be a rotary-wing aircraft, for example a helicopter, or a fixed-wing aircraft. The system may constitute a module of a flight management system (FMS) onboard the aircraft or the system may be a dedicated module onboard the aircraft.

The instrument approach procedure shown in figure 1 is a so-called “Point-in-Space” (“PinS”) procedure. The PinS procedure applies only to rotorcraft. The PinS procedure 35 comprises an initial approach waypoint or initial approach fix (IAF) 8, an intermediate waypoint or intermediate fix (IF) 9, a final approach waypoint or final approach fix (FAF) 10 13 and a missed approach point 11. In the PinS procedure, the missed approach point 11 is also a waypoint or “fix”, which is referred to as the “Point-in-Space”.

The PinS procedure comprises an initial approach path segment 3 between the IAF 8 and the IF 9, an intermediate path segment 4 between the IF 9 and the FAF 10, and a final 5 approach path segment 5 between the FAF 10 and the missed approach point or Point-in-Space 11. The initial approach path segment 3, the intermediate path segment 4 and the final approach path segment 5 each have a length that is defined by the length of said flight path when projected onto the surface of the earth, as shown by xFAs, Xis and Xias in figure 1. The approach glide slope for the final approach path segment is indicated by Θ.

10 Thus, the PinS procedure brings the aircraft to the Point-in-Space 11 with the pilot flying by reference to instruments. Normally, the pilot proceeds visually from the Point-in-Space 11 to find a suitable landing spot 12, as schematically indicated by visual flight path 14. However, if the pilot, for some reason, has not gained visual ground contact by the time the Point-in-Space 11 is reached, or the pilot considers that the weather is not good enough 15 for the visual path segment, for example an unexpected patch of ground fog may obstruct the pilot’s visibility, the pilot will start a missed approach procedure. During the missed approach procedure, the aircraft flies from the missed approach point, i.e. the Point-in-Space 11, to a higher altitude according to a straight flight path. The straight flight path that is followed by the aircraft in the missed approach procedure defines a missed approach segment 6.

20 Alternatively, the missed approach segment 6 may comprise a missed approach holding waypoint (not shown), to which the aircraft is directed in the missed approach procedure.

The instrument landing procedure shown in figure 2 is a so-called “Localizer-Precision with Vertical guidance” (“LPV”) procedure, sometimes also named “Approach Procedure with Vertical guidance” (“APV”) procedure. The LPV procedure can be used by both rotary-wing 25 and fixed-wing aircraft. The LPV procedure falls in the class of “precision approach” (it is sometimes referred to as “precise approach” rather than “precision approach”). Like the PinS procedure, the LPV procedure comprises an initial approach waypoint or initial approach fix (IAF) 8, an intermediate waypoint or intermediate fix (IF) 9, a final approach waypoint or final approach fix (FAF) 10 and a missed approach point 11. In the LPV procedure, the missed 30 approach point 11 is not a waypoint that is displayed to the pilot. The missed approach point 11 is a calculated point in the procedure which lies at a decision altitude (DA) that is predetermined in the procedure.

The LPV procedure also comprises an initial approach path segment 3 between the IAF 8 and the IF 9, an intermediate path segment 4 between the IF 9 and the FAF 10, and a 35 final approach path segment 5 between the FAF 10 and the missed approach point 11. The initial approach path segment 3, the intermediate path segment 4 and the final approach path segment 5 each have a length that is defined by the length of said flight path when projected 14 onto the surface of the earth, as shown by xFAs, Xis and Xias in figure 2. The approach glide slope for the final approach path segment is indicated by Θ.

With the LPV procedure, the pilot decides at the decision altitude either to continue and land on the landing position on the ground 12 ahead or to start the missed approach 5 procedure. During the missed approach procedure, the aircraft flies from the missed approach point, i.e. from the decision altitude (DA) to a higher altitude according to a straight flight path. The straight flight path that is followed by the aircraft in the missed approach procedure defines a missed approach segment 6. Alternatively, the missed approach segment 6 may comprise a missed approach holding waypoint (not shown), to which the 10 aircraft is directed in the missed approach procedure.

Although the PinS procedure and the LPV procedure are shown in figures 1 and 2 with straight path segments 3, 4, 5, said path segments 3, 4, 5 may be curved or at an angle with respect to each other, in particular the initial approach path segment 3, and also the intermediate path segment 4. This is also shown in the instrument approach procedure 15 according to figure 7.

Figure 3 schematically shows a system 1 for determining the instrument approach procedure shown in figure 1 or 2 onboard the aircraft. The system 1 shown in figure 3 is integrated in the flight management system (FMS) 20 of the aircraft. In operation, the pilot may call a list of procedures in the FMS 20, for example arrival procedures and approach 20 procedures. With the system 1 according to the invention integrated into the FMS 20, the pilot can select that, for example, the PinS or LPV procedure illustrated in figures 1 and 2 or another type of procedure is to be calculated by the system 1.

The system 1 comprises an input device 23 onboard the aircraft for selecting a target position. With the PinS procedure, the target position is the Point-in-Space 11, i.e. the Point-25 in-Space 11 is directly entered by the pilot into the input device 23. For the LPV procedure, the target position is a landing position on the ground. The pilot may also select a desired approach glide slope, a desired approach course or approach direction for the final approach path segment 5 and a desired initial altitude by means of the input device 23. Incidentally, the pilot may also be asked by the system to enter additional data into the input device 23 of the 30 system. If the landing position on the ground is in an urban area with many obstacles around, the pilot might consider finding a clear landing area. When arriving at the Point-in-Space 11 in the PinS procedure, the flight will proceed visually until a suitable landing spot is found. With the LPV procedure, the aircraft will land straight ahead onto a runway or onto a Final Approach and Take-Off (FATO) area.

35 The system 1 comprises a processor which calculates the lengths of the path segments xFAs, Xis and X|AS and the coordinates of the IAF 8, the IF 9, the FAF 10 and the missed approach point 11 on the basis of the selected target position, the selected approach 15 glide slope, the selected approach course and the selected initial altitude. The processor also determines the course or direction of the missed approach path segment 6. Thus, the initial approach path segment 3, the intermediate path segment 4 and the final approach path segment 5 can be determined using the input from the pilot. Alternatively, the system 1 may 5 autonomously select an approach glide slope and/or an approach course and/or an initial altitude, wherein the autonomously selected values are used to calculate the coordinates of the IAF 8, the IF 9, the FAF 10 and the missed approach point 11.

The system 1 comprises a database system 22 which is connected to the FMS 20. The database system 22 may comprise one or more databases. The database system 22 10 contains terrain data and obstacle data. Furthermore, the system comprises a memory (not shown) which contains obstacle clearance surface data, on the basis of which, for each of the initial approach path segment 3, the intermediate path segment 4, the final approach path segment 5 and the missed approach path segment 6, an obstacle clearance surface 30 is defined that extends at a pre-determined orientation and at a pre-determined distance below 15 said path segment 3, 4, 5, 6.

As shown in figures 1 and 4, which illustrate the PinS procedure, the obstacle clearance surface 30 for the initial approach path segment 3 comprises a primary area 31 and two secondary areas 32. The primary area 31 is oriented substantially horizontally and extends at a minimum obstacle clearance distance (MOCias) below the initial approach path 20 segment 3, as shown in figure 8. The minimum obstacle clearance (MOC) distance is given for any type of procedure. For example, with the PinS procedure, the minimum obstacle clearance (MOCias) distance is 1000 ft in the initial approach path segment 3. The width w of the primary area in the initial approach path segment 3 may be, for example, between 2-4 nm. The secondary areas 32 are situated on either side of the primary area 31. The 25 secondary areas 32 slope upwards from the longitudinal edges of the primary area 31. The obstacle clearance surface 30 for the intermediate path segment 4 also comprises a primary area 31 and two secondary areas 32, similar to the initial approach path segment 3. The primary area 31 lies at a minimum obstacle clearance (MOC|S) distance below the intermediate path segment 4 (500 ft with the PinS procedure). The obstacle clearance 30 surface 30 for the final approach path segment 5 also has a primary area 31 and adjacent secondary areas 32. The primary area 31 of the final approach path segment 3 is situated at a minimum obstacle clearance (MOCFa) below the altitude of the Point-in-Space 11. With this PinS procedure, MOCfa is 246 ft (see figures 7 and 8).

With the LPV procedure, the obstacle clearance surface 30 for the initial approach 35 path segment 3 and the intermediate path segment 4 is similar to the PinS procedure, i.e. the obstacle clearance surface 30 comprises a primary area 31 and two adjacent secondary areas 32. Of course, the minimum obstacle clearance (MOC) distance may be different for 16 the LPV procedure. The obstacle clearance surfaces 30 for the final approach segment 5 and the missed approach segment 6 are shown in figures 5 and 6.

With the LPV procedure illustrated in figures 2, 5 and 6, the obstacle clearance surfaces 30 may be defined in a runway coordinate system. The landing position on the 5 ground is situated on a runway having a centre line. The runway coordinate system has an origin situated at a runway threshold of the runway, and mutually perpendicular axes X, Y and Z extending from the origin. The Z-axis extends vertically, the X-axis extends parallel to the centre line of the runway, towards the final approach waypoint 10, and the Y-axis extends transversely to the centre line of the runway according to the right-hand rule. In such a 10 runway coordinate system, the final approach path segment 5 extends in the X-Z plane.

With the LPV procedure shown in figures 5 and 6, the obstacle clearance surface 30 of the final approach path segment 5 comprises a central surface, which is referred to as W-surface, which has a centre line that extends in the X-Z plane. The W-surface extends at right angles to the X-Z plane, and is inclined with respect to the X-Y plane and with respect to 15 the Y-Z plane. The W-surface is symmetrical with respect to the X-Z plane. In this case, the W-surface is substantially rectangular. The W-surface slopes downwards as seen in the direction of the runway. In this example, the W-surface extends partially in the intermediate path segment 4.

As shown in figures 5 and 6, the obstacle clearance surface 30 of the final approach 20 path segment 5 also comprises a further central surface having a centre line that extends in the X-Z plane, which are referred to as W’-surface. The W’-surface is a continuation of the W-surface as seen in the direction of the runway, i.e. the W’-surface is situated closer to the runway. The W’-surface is also substantially rectangular, and also extends at right angles to the X-Z plane, and is inclined with respect to the X-Y plane and to the Y-Z plane, but at a 25 different angle than the W-surface. Thus, the W-surface and the W’-surface are aligned with each other and each slope downward as seen in the direction of the runway, whereas they are connected to each other by a discontinuity. As shown in figure 6, the W’-surface extends at an angle with respect to the X-Y plane that is greater than the W-surface that is situated further away from the runway.

30 The W-surface and W’-surface comprise two opposed longitudinal edges 34 on either side. The obstacle clearance surface 30 of the final approach segment 5 comprises two side surfaces, which are each referred to as X-surface, which X-surfaces each slope upward from the longitudinal edges 34 of the W-surface and W’-surface at an angle with respect to the X-Y plane, to the X-Z plane, and also to the Y-Z plane. Thus, on the one hand, the X-surfaces 35 each slope downward as seen in the direction of the runway, whereas on the other hand, the X-surfaces each slopes upward from the respective longitudinal edge 34 of the W-surface.

As seen in a cross-section parallel to the Y-Z plane, the W-surface and the adjacent portion 17 of the X-surfaces define the shape of a trough. The same applies to the W’-surface and the adjacent portion of the X-surfaces. Figures 5 and 6 also illustrate that the X-surfaces may extend partially in the intermediate path segment 4.

With the LPV procedure, the obstacle clearance surface 30 of the missed approach 5 path segment 6 also comprise at least one central surface, which is referred to as Z-surface, which has a centre line that extends in the X-Z plane. The Z-surface extends at right angles to the X-Z plane, and is inclined with respect to the X-Y plane and also to the Y-Z plane. The Z-surface of the missed approach segment is symmetrical with respect to the X-Z plane. As shown in figure 5, the Z-surface has the shape of a number of isosceles trapeziums that are 10 aligned with each other. The Z-surface slopes upward as seen in the direction away from the runway (see figure 6).

Furthermore, the Z-surface comprises two opposed longitudinal edges 35 on either side of said Z-surface. The longitudinal edges 35 are non-parallel as the Z-surface has the shape of a number of isosceles trapeziums. The obstacle clearance surface 30 of the missed 15 approach segment 6 comprises two side surfaces, which are each referred to as Y-surface. The Y-surfaces each slope upward from the longitudinal edges 35 of the Z-surface at an angle with respect to the X-Y plane, to the X-Z plane, and also to the Y-Z plane. In addition, the Y-surfaces each slope upward as seen in the direction away from the runway (see figure 6). As seen in a cross-section parallel to the Y-Z plane, the Z-surface and the adjacent 20 portions of the Y-surfaces also define the shape of a trough. As shown in figures 5 and 6, the Y-surfaces also extend partially along the final approach segment 5 adjacent to the longitudinal edges of the X-surfaces.

As explained above, the dimensions, shape and orientation of the obstacle clearance surfaces 30 depend on the type of procedure and also on the path segment. However, they 25 are given and pre-determined in the initial approach path segment 3, the intermediate path segment 4, the final approach path segment 5 and the missed approach path segment 6 for each specific type of procedure. Therefore, obstacle clearance surface data relating to the dimensions, shape and orientation of the obstacle clearance surfaces 30 are stored in a memory of the system for each of said path segments 3, 4, 5, 6 and for each type of 30 procedure. Once the initial approach path segment 3, the intermediate path segment 4, the final approach path segment 5 and the missed approach path segment 6 are determined by the system 1, the obstacle clearance surface 30 follows directly from the obstacle clearance surface data stored in the memory.

After calculating the coordinates of the IAF 8, the IF 9, the FAF 10 and the missed 35 approach point 11, i.e. after determining the initial approach path segment 3, the intermediate path segment 4, the final approach path segment 5 and the missed approach path segment 6, the processor determines an obstacle clearance altitude (OCA) for the 18 instrument approach procedure. The obstacle clearance altitude (OCA) is calculated by checking if any obstacles identified by the terrain data and obstacle data in the database system 22 penetrate any of the obstacle clearance surfaces 30. The obstacle clearance altitude (OCA) for the instrument approach procedure is the lowest altitude at which any 5 obstacle identified by the terrain data and obstacle data in the database system 22 does not penetrate the obstacle clearance surfaces 30 in any of said path segments 3, 4, 5, 6, i.e. at the obstacle clearance altitude (OCA) the aircraft is safeguarded from collision with any obstacles.

Next, the calculated obstacle clearance distance (OCA) and the coordinates of the 10 IAF 8, the IF 9, the FAF 10 are displayed on a display device 24 of the system 1, which may be the display of the FMS 20. With the PinS procedure shown in figure 1, the coordinates of the missed approach decision point 11, i.e. the Point-in-Space, are also displayed on the display device 24. With the LPV procedure shown in figure 2, instead of the missed approach point 11, the coordinates of the landing position 12 on the ground are displayed on the 15 display device 24.

The pilot is then asked to accept or optimize the instrument approach procedure calculated by the system 1. The pilot can select the optimization function when he considers that the calculated obstacle clearance altitude (OCA) is still too high, for example because of a cloud base below said altitude.

20 When the pilot selects the optimization function, the system 1 analyses if the calculated obstacle clearance altitude (OCA) that has been displayed on the display device 24 can be decreased by changing the parameters selected by the pilot, e.g. the glide scope Θ for the final approach path segment 5, the initial altitude and/or the approach course selected by the pilot. As a result, an obstacle that penetrated the obstacle clearance surface 30 25 associated with the calculated instrument approach procedure may no longer penetrate.

Thus, when the optimization function is selected, an attempt is made by the system 1 to generate a modified instrument approach procedure with a lower obstacle clearance altitude (modified OCA). If the system 1 arrives at such a modified instrument approach procedure, said lower obstacle clearance altitude (modified OCA) is displayed on the display device 24 30 together with the associated coordinates of the IAF 8, the IF 9, the FAF 10 and the Point-in-Space 11/landing position 12 on the ground. Next, the pilot is again asked to accept. If the modified obstacle clearance altitude (OCA) is still not acceptable, the pilot may decide to select another target position 12 or another approach procedure.

After the pilot has accepted the instrument approach procedure calculated by the 35 system 1 (optimized or not), the coordinates of the IAF 8, the IF 9, the FAF 10 and the Point-in-Space 11/landing position 12 on the ground can be loaded into the approach section of the current flight plan. If there is no current flight plan, it may become a dedicated “approach 19 flight plan”. When approaching the IAF 8, the pilot activates the calculated instrument approach procedure. The system 1 then computes flight path deviations from the desired approach flight path by means of the flight guidance module 25. The computed deviations are shown on the pilot’s flight display. The pilot may also select an automatic approach by 5 switching on the autopilot mode. In this mode, the autopilot accepts flight guidance data from the flight guidance module 25.

Thus, the system according to the invention can provide an instrument approach procedure even if there is no current flight plan or no approach procedures exist for the destination. Therefore, the system according to the invention can be used at airports and 10 landing sites that are not equipped with any ground-based infrastructure.

The system according to the invention is not limited to determining the instrument approach procedures shown in figures 1 and 2, i.e. the system according to the invention may also calculate other instrument approach procedures, for example an instrument approach procedure referred to as “SBAS Offshore Approach Procedure” (“SOAB”), wherein 15 SBAS is an abbreviation of “Satellite Based Augmentation System”.

Claims

1. Systeem voor het bepalen van een instrumentnaderingsprocedure voor een luchtvaartuig, waarbij het systeem is voorzien van: 5. een databasesysteem (22) met terreingegevens en obstakelgegevens, - een invoerinrichting (23) aan boord van het luchtvaartuig voor het selecteren van een doelpositie, - een afbeeldingsinrichting (24) aan boord van het luchtvaartuig voor het afbeelden van informatie voor een piloot van het luchtvaartuig, 10. een processor aan boord van het luchtvaartuig, waarbij de processor is verbonden met de invoerinrichting (23) en met de afbeeldingsinrichting (24), en waarbij de processor is uitgevoerd voor het bepalen van een instrumentnaderingsprocedure voor het luchtvaartuig op basis van de geselecteerde doelpositie (12) en de terreingegevens en obstakelgegevens uit het databasesysteem (22), 15 met het kenmerk, dat de processor is uitgevoerd voor het bepalen, op basis van de geselecteerde doelpositie, van een eindnaderingsbaansegment (5) en een gemiste-naderingsbaansegment (6) van de instrumentnaderingsprocedure, waarbij het eindnaderingsbaansegment (5) is bepaald door een vliegbaan die begint bij een eindnaderingsbaanpunt (10) op een hoogte 20 van het eindnaderingsbaanpunt en eindigt bij een gemiste-naderingspunt (11), op een lagere hoogte dan de hoogte van het eindnaderingsbaanpunt, voor het besluiten of het luchtvaartuig verder kan gaan naar een landingspositie (12) op de grond of een gemiste-naderingsprocedure wordt gestart, en waarbij het gemiste-naderingsbaansegment (6) is bepaald door een vliegbaan die begint bij het gemiste-naderingspunt (11) en eindigt op een 25 hogere hoogte dan de hoogte van het gemiste-naderingspunt, waarbij het gemiste-naderingsbaansegment (6) wordt gevolgd door het luchtvaartuig als op het gemiste-naderingspunt (11) wordt besloten dat de gemiste-naderingsprocedure wordt gestart, en het systeem is voorzien van een geheugen met obstakelvrij-vlakgegevens, op basis waarvan, voor elk van het eindnaderingsbaansegment (5) en het gemiste-30 naderingsbaansegment (6), ten minste een obstakelvrij vlak (30) is bepaald dat zich uitstrekt met een vooraf bepaalde oriëntatie en op een vooraf bepaalde afstand onder dat baansegment (5, 6), en de processor is uitgevoerd voor het bepalen van een obstakelvrije hoogte (Engels: “Obstacle Clearance Altitude” (OCA)) voor de instrumentnaderingsprocedure als de laagste 35 hoogte waarbij elk obstakel dat is geïdentificeerd door de terreingegevens en obstakelgegevens in het databasesysteem (22) geen van de obstakelvrije vlakken (30) in het eindnaderingsbaansegment (5) en het gemiste-naderingsbaansegment (6) penetreert, en -21 - het systeem (1) is uitgevoerd voor het afbeelden van de obstakelvrije hoogte (OCA) op de afbeeldingsinrichting (24).System for determining an instrument approach procedure for an aircraft, the system comprising: 5. a database system (22) with terrain data and obstacle data, - an input device (23) on board the aircraft for selecting a target position, - an on-board imaging device (24) for displaying information for an aircraft pilot, an on-board processor of the aircraft, the processor being connected to the input device (23) and to the imaging device (24) ), and wherein the processor is configured to determine an instrument approach procedure for the aircraft based on the selected target position (12) and the terrain data and obstacle data from the database system (22), characterized in that the processor is configured for the determine, based on the selected target position, a final approach track segment (5) and a missed approach track segment (6) of the instrument approach procedure, wherein the final approach path section (5) is defined by a flight path that starts at a final approach path point (10) at a height 20 of the final approach path point and ends at a missed approach point (11), at a height lower than that the height of the final runway point, for deciding whether the aircraft can proceed to a landing position (12) on the ground or a missed approach procedure is started, and where the missed approach track segment (6) is determined by a flight path starting at the missed approach point (11) and ends at a height higher than the height of the missed approach point, the missed approach track segment (6) being followed by the aircraft if it is decided at the missed approach point (11) that the missed approach point approach procedure is started, and the system is provided with a memory with obstacle-free area data, on the basis of which, for each of the final approach track segment (5) and the missed approach track segment (6), at least one obstacle-free surface (30) is defined which extends with a predetermined orientation and at a predetermined distance below that track segment (5, 6), and the processor is designed for determining of an obstacle-free height (English: “Obstacle Clearance Altitude” (OCA)) for the instrument approach procedure as the lowest altitude where any obstacle identified by the terrain data and obstacle data in the database system (22) does not include any of the obstacle-free surfaces (30) in the final approach track segment (5) and the missed approach track segment (6) penetrate, and the system (1) is designed to display the obstacle-free height (OCA) on the imaging device (24).

2. Systeem volgens een van de voorgaande conclusies, waarbij, in de 5 instrumentnaderingsprocedure, de doelpositie een positie boven de grond is, en het gemiste-naderingspunt (11) een baanpunt is, dat is bepaald door de doelpositie.2. System as claimed in any of the foregoing claims, wherein, in the instrument approach procedure, the target position is a position above ground, and the missed approach point (11) is a trajectory point determined by the target position.

3. Systeem volgens conclusie 2, waarbij het obstakelvrije vlak (30) van het eindnaderingsbaansegment (5) een primair oppervlak (31) en twee secundaire oppervlakken 10 (32) omvat, waarbij het primaire oppervlak (31) van het eindnaderingsbaansegment (5) in hoofdzaak horizontaal is georiënteerd en zich uitstrekt op een minimale obstakelvrije (Engels: “Minimum Obstacle Clearance” (MOC)) afstand onder het eindnaderingsbaansegment (5), en waarbij elk secundair oppervlak (32) van het eindnaderingsbaansegment (5) schuin oploopt vanaf een langsrand van het primaire 15 oppervlak (31) van het eindnaderingsbaansegment (5) aan weerszijden van dat primaire oppervlak (31).The system of claim 2, wherein the obstacle-free surface (30) of the final approach track segment (5) comprises a primary surface (31) and two secondary surfaces 10 (32), the primary surface (31) of the final approach track segment (5) is essentially horizontally oriented and extends at a minimum obstacle-free distance (English: “Minimum Obstacle Clearance” (MOC)) below the final approach track section (5), and where each secondary surface (32) of the final approach track section (5) slopes obliquely from a longitudinal edge of the primary surface (31) of the final approach track segment (5) on either side of that primary surface (31).

4. Systeem volgens conclusie 2 of 3, waarbij het obstakelvrije vlak (30) van het gemiste-naderingsbaansegment (6) een primair oppervlak (31) en twee secundaire oppervlakken (32) 20 omvat, waarbij het primaire oppervlak (31) van het gemiste-naderingsbaansegment (6) in hoofdzaak horizontaal is georiënteerd en zich uitstrekt op een minimale obstakelvrije (Engels: “Minimum Obstacle Clearance”(MOC)) afstand onder het gemiste-naderingsbaansegment (6), en waarbij elk secundair oppervlak (32) van het gemiste-naderingsbaansegment (6) schuin oploopt vanaf een langsrand van het primaire oppervlak 25 (31) van het gemiste-naderingsbaansegment (6) aan weerszijden van dat primaire oppervlak (31).A system according to claim 2 or 3, wherein the obstacle-free surface (30) of the missed approach track segment (6) comprises a primary surface (31) and two secondary surfaces (32), wherein the primary surface (31) of the missed approach track segment (6) is oriented substantially horizontally and extends at a minimum obstacle-free (English: "Minimum Obstacle Clearance" (MOC)) distance below the missed approach track segment (6), and where each secondary surface (32) of the missed approach track segment (6) rises obliquely from a longitudinal edge of the primary surface (31) of the missed approach track segment (6) on either side of that primary surface (31).

5. Systeem volgens een van de voorgaande conclusies, waarbij in de instrumentnaderingsprocedure, de doelpositie de landingspositie (12) op de grond is, en het 30 gemiste-naderingspunt (11) zich op een in hoofdzaak rechte lijn vanaf het eindnaderingsbaanpunt (5) naar de landingspositie (12) op de grond bevindt.5. System as claimed in any of the foregoing claims, wherein in the instrument approach procedure, the target position is the landing position (12) on the ground, and the missed approach point (11) is on a substantially straight line from the final approach path point (5) to the landing position (12) is on the ground.

6. Systeem volgens een van de voorgaande conclusies, waarbij de landingspositie (12) op de grond zich op een landingsbaan met een centrale hartlijn bevindt, en waarbij een 35 landingsbaancoördinaatstelsel is bepaald dat een oorsprong heeft die zich op een landingsbaandrempel van de landingsbaan bevindt, en loodrecht ten opzichte van elkaar verlopende assen X, Y en Z die zich vanaf de oorsprong uitstrekken, waarbij de Z-as zich -22- verticaal uitstrekt, waarbij de X-as zich evenwijdig aan de centrale hartlijn van de landingsbaan uitstrekt, naar het eindnaderingsbaanpunt (10), en waarbij de Y-as zich dwars ten opzichte van de centrale hartlijn van de landingsbaan uitstrekt volgens de rechterhandregel, en waarbij het eindnaderingsbaansegment (5) zich in het X-Z-vlak 5 uitstrekt.6. System as claimed in any of the foregoing claims, wherein the landing position (12) on the ground is on a landing strip with a central axis, and wherein a landing strip coordinate system is determined which has an origin which is located on a landing strip threshold of the landing strip, and axes X, Y and Z extending perpendicular to each other and extending from the origin, the Z-axis extending vertically, the X-axis extending parallel to the central axis of the runway, towards the final approach runway point (10), and wherein the Y-axis extends transversely to the central axis of the runway according to the right-hand rule, and wherein the final approach runway segment (5) extends in the XZ plane 5.

7. Systeem volgens conclusie 6, waarbij het obstakelvrije vlak (30) van het eindnaderingsbaansegment (3) is voorzien van ten minste een centraal vlak (W) met een centrale hartlijn die zich in het X-Z-vlak uitstrekt, en welk centraal vlak (W) zich loodrecht ten 10 opzichte van het X-Z-vlak uitstrekt, en welk centraal vlak (W) schuin ten opzichte van het X-Y-vlak verloopt.The system according to claim 6, wherein the obstacle-free surface (30) of the final approach track segment (3) is provided with at least one central surface (W) with a central axis extending in the XZ plane, and which central surface (W ) extends perpendicular to the XZ plane, and which central plane (W) extends obliquely to the XY plane.

8. Systeem volgens conclusie 7, waarbij het centrale vlak (W) is voorzien van twee tegenoverliggende langsranden aan weerszijden van dat centrale vlak (W), en waarbij het 15 obstakelvrije vlak (30) van het eindnaderingsbaansegment (3) is voorzien van twee zijvlakken (X) die schuin oplopen vanaf de langsranden van het centrale vlak (W) onder een hoek ten opzichte van het X-Y-vlak, het X-Z-vlak, en het Y-Z-vlak.8. System as claimed in claim 7, wherein the central plane (W) is provided with two opposite longitudinal edges on either side of said central plane (W), and wherein the obstacle-free surface (30) of the end-of-run track segment (3) is provided with two side surfaces (X) inclined from the longitudinal edges of the central plane (W) at an angle with respect to the XY plane, the XZ plane, and the YZ plane.

9. Systeem volgens een van de conclusies 6-8, waarbij het obstakelvrije vlak (30) van 20 het gemiste-naderingsbaansegment (6) is voorzien van ten minste een centraal vlak (Z) met een centrale hartlijn die zich in het X-Z-vlak uitstrekt, en welk centraal vlak (Z) zich loodrecht ten opzichte van het X-Z-vlak uitstrekt, en welk centraal vlak (Z) schuin ten opzichte van het X-Y-vlak verloopt.9. System as claimed in any of the claims 6-8, wherein the obstacle-free surface (30) of the missed approach track segment (6) is provided with at least one central surface (Z) with a central axis located in the XZ-plane and which central plane (Z) extends perpendicularly to the XZ plane, and which central plane (Z) extends obliquely to the XY plane.

10. Systeem volgens een van de voorgaande conclusies, waarbij de processor is uitgevoerd voor het bepalen van een beginnaderingsbaansegment (3) en/of een tussenbaansegment (4) van de instrumentnaderingsprocedure, waarbij het beginnaderingsbaansegment (3) is bepaald door een vliegbaan die begint bij een beginnaderingsbaanpunt (8) en eindigt bij een tussenbaanpunt (9), en waarbij het 30 tussenbaansegment (4) is bepaald door een vliegbaan die begint bij het tussenbaanpunt (9) en eindigt bij het eindnaderingsbaanpunt (10), waarbij het beginnaderingsbaanpunt (8) en het tussenbaanpunt (9) bij voorkeur op dezelfde hoogte als de hoogte van het eindnaderingsbaanpunt liggen, en waarbij, op basis van de obstakelvrij-vlakgegevens, voor elk van het beginnaderingsbaansegment (3) en/of het tussenbaansegment (4), ten minste 35 een obstakelvrij vlak (30) is bepaald dat zich uitstrekt met een vooraf bepaalde oriëntatie en op een vooraf bepaalde afstand onder dat baansegment (3, 4), en waarbij de processor is uitgevoerd voor het bepalen van de obstakelvrije hoogte (OCA) voor de -23- instrumentnaderingsprocedure als de laagste hoogte waarbij elk obstakel dat is geïdentificeerd door de terreingegevens en obstakelgegevens in het databasesysteem (22) geen van de obstakelvrije vlakken (30) in het eindnaderingsbaansegment (5) en het gemiste-naderingsbaansegment (6) en het beginnaderingsbaansegment (3) en/of het 5 tussenbaansegment (4) penetreert.The system according to any of the preceding claims, wherein the processor is configured to determine a start approach track segment (3) and / or an intermediate track section (4) of the instrument approach procedure, the start approach track section (3) being determined by a flight path starting at a runway runway point (8) and terminate at an runway runway point (9), and wherein the runway segment (4) is defined by a flight path that starts at the runway runway point (9) and ends at the final runway runway point (10), the runway runway run point (8) and the intermediate track point (9) are preferably at the same height as the height of the final approach track point, and wherein, on the basis of the obstacle clearance data, at least 35 for each of the starting approach track segment (3) and / or the intermediate track segment (4) an obstacle-free surface (30) is defined which extends with a predetermined orientation and at a predetermined distance below that track segment (3, 4), and wherein the process is designed to determine the obstacle-free height (OCA) for the instrument approach procedure as the lowest height at which any obstacle identified by the terrain data and obstacle data in the database system (22) does not include any of the obstacle-free surfaces (30) in the final approach track section (5) and the missed approach track section (6) and the start approach track section (3) and / or the intermediate track section (4) penetrates.

11. Systeem volgens conclusie 10, waarbij het obstakelvrije vlak (30) van het beginnaderingsbaansegment (3) en/of van het tussenbaansegment (4) respectievelijk een primair oppervlak (31) en twee secundaire oppervlakken (32) omvatten, en waarbij het 10 primaire oppervlak (31) van het beginnaderingsbaansegment (3) en/of van het tussenbaansegment (4) in hoofdzaak horizontaal is georiënteerd en zich op een minimale obstakelvrije (MOC) afstand onder dat baansegment (3,4) uitstrekt, en waarbij elk secundair oppervlak (32) van dat baansegment (3,4) schuin oploopt vanaf een langsrand van het primaire oppervlak (31) van dat baansegment (3,4) aan weerszijden van dat primaire 15 oppervlak (31).11. System as claimed in claim 10, wherein the obstacle-free surface (30) of the starting approach track segment (3) and / or of the intermediate track segment (4) comprise a primary surface (31) and two secondary surfaces (32) respectively, and wherein the primary surface (31) of the starting approach track segment (3) and / or of the intermediate track segment (4) is oriented substantially horizontally and extends at a minimum obstacle-free (MOC) distance below that track segment (3,4), and wherein each secondary surface ( 32) of that web segment (3,4) rises obliquely from a longitudinal edge of the primary surface (31) of that web segment (3,4) on either side of that primary surface (31).

12. Systeem volgens een van de voorgaande conclusies, waarbij het geheugen is voorzien van instrumentnaderingsproceduregegevens van meerdere verschillende instrumentnaderingsprocedures, bij voorkeur daarbij inbegrepen de 20 instrumentnaderingsprocedure volgens conclusie 2 en de instrumentnaderingsprocedure volgens conclusie 5, en waarbij de invoerinrichting (23) is uitgevoerd voor het selecteren van een instrumentnaderingsprocedure uit de meerdere instrumentnaderingsprocedures, en waarbij het systeem (1) is uitgevoerd voor het bepalen van de geselecteerde instrumentnaderingsprocedure. 2512. System as claimed in any of the foregoing claims, wherein the memory is provided with instrument approach procedure data from a plurality of different instrument approach procedures, preferably including the instrument approach procedure according to claim 2 and the instrument approach procedure according to claim 5, and wherein the input device (23) is designed for selecting an instrument approach procedure from the multiple instrument approach procedures, and wherein the system (1) is configured to determine the selected instrument approach procedure. 25

13. Systeem volgens een van de voorgaande conclusies, waarbij de invoerinrichting (23) is uitgevoerd voor het selecteren van een naderingsglijhoek voor het eindnaderingsbaansegment (5), en waarbij de processor is uitgevoerd voor het berekenen van het eindnaderingsbaanpunt (10) en het gemiste-naderingspunt (11) op basis van de 30 geselecteerde naderingsglijhoek.A system according to any one of the preceding claims, wherein the input device (23) is configured to select an approach sliding angle for the final approach track segment (5), and wherein the processor is configured to calculate the final approach path point (10) and the missed track approach point (11) based on the selected approach glide angle.

14. Systeem volgens een van de voorgaande conclusies, waarbij de invoerinrichting (23) is uitgevoerd voor het selecteren van een beginhoogte, en waarbij de processor is uitgevoerd voor het berekenen van het eindnaderingsbaanpunt (10) en het gemiste-naderingspunt (11) 35 op basis van de geselecteerde beginhoogte. -24-14. System as claimed in any of the foregoing claims, wherein the input device (23) is designed for selecting a starting height, and wherein the processor is designed for calculating the final approach path point (10) and the missed approach point (11) on based on the selected starting height. -24-

15. Systeem volgens een van de voorgaande conclusies, waarbij de invoerinrichting (23) is uitgevoerd voor het selecteren van een naderingskoers voor het eindnaderingsbaansegment (5), en waarbij de processor is uitgevoerd voor het berekenen van het eindnaderingsbaanpunt (10) en het gemiste-naderingspunt (11) op basis van de 5 geselecteerde naderingskoers.The system according to any of the preceding claims, wherein the input device (23) is configured to select an approach rate for the final approach path segment (5), and wherein the processor is configured to calculate the final approach path point (10) and the missed point. approach point (11) based on the 5 selected approach rate.

16. Systeem volgens een van de conclusies 13-15, waarbij de invoerinrichting (23) is uitgevoerd voor het selecteren van een optimalisatiefunctie voor het bepalen, nadat een obstakelvrije hoogte (OCA) van een eerste instrumentnaderingsprocedure is bepaald door 10 de processor, van een tweede, alternatieve instrumentnaderingsprocedure, en waarbij de processor is uitgevoerd voor het aanpassen van de geselecteerde naderingsglijhoek en/of de geselecteerde beginhoogte en/of de geselecteerde naderingskoers, nadat de optimalisatiefunctie is geselecteerd, en voor het bepalen van een aangepast eindnaderingsbaansegment (5) en een aangepast gemiste-naderingsbaansegment (6), en, 15 optioneel, een aangepast beginnaderingsbaansegment (3) en/of een aangepast tussenbaansegment (4), op basis van de geselecteerde doelpositie en de aangepaste naderingsglijhoek en/of de aangepaste beginhoogte en/of de aangepaste naderingskoers, en waarbij, op basis van de obstakelvrij-vlakgegevens, voor elk van die aangepaste baansegmenten (3, 4, 5, 6), ten minste een obstakelvrij vlak (30) is bepaald dat zich met een 20 vooraf bepaalde oriëntatie en op een vooraf bepaalde afstand onder die aangepaste baansegmenten (3, 4, 5, 6) uitstrekt, en de processor is uitgevoerd voor he bepalen van een aangepaste obstakelvrije hoogte (aangepaste OCA) voor de tweede, alternatieve instrumentnaderingsprocedure als de laagste hoogte waarbij elk obstakel dat is geïdentificeerd door de terreingegevens en obstakelgegevens in het databasesysteem (22) 25 geen van de obstakelvrije vlakken (30) in die aangepaste baansegmenten (3, 4, 5, 6) penetreert, en waarbij de processor is uitgevoerd voor het vergelijken van de aangepaste obstakelvrije hoogte (aangepaste OCA) met de obstakelvrije hoogte (OCA) van de eerste instrumentnaderingsprocedure.16. System as claimed in any of the claims 13-15, wherein the input device (23) is designed for selecting an optimization function for determining, after an obstacle-free height (OCA) of a first instrument approach procedure has been determined by the processor, of a second, alternative instrument approach procedure, and wherein the processor is configured to adjust the selected approach glide angle and / or the selected start height and / or the selected approach course after the optimization function is selected, and to determine an adjusted end approach track section (5) and a adjusted missed approach track segment (6), and, optionally, a modified start approach track segment (3) and / or an adjusted intermediate track segment (4), based on the selected target position and the adjusted approach sliding angle and / or the adjusted starting height and / or the adjusted starting height approach rate, and wherein, based on the obstacle-free area data, for each of those adjusted first track segments (3, 4, 5, 6), at least one obstacle-free surface (30) is defined which extends below said adjusted track segments (3, 4, 5, 6) with a predetermined orientation and at a predetermined distance , and the processor is configured to determine an adjusted obstacle-free height (adjusted OCA) for the second, alternative instrument approach procedure as the lowest altitude at which any obstacle identified by the terrain data and obstacle data in the database system (22) does not have any of the obstacle-free penetrates faces (30) into said adjusted web segments (3, 4, 5, 6), and wherein the processor is configured to compare the adjusted obstacle-free height (adjusted OCA) with the obstacle-free height (OCA) of the first instrument approach procedure.

17. Systeem volgens een van de voorgaande conclusies, waarbij het systeem is geïntegreerd met een vluchtmanagementsysteem (Engels: “Flight Management System” (FMS)) (20) van het luchtvaartuig.A system according to any of the preceding claims, wherein the system is integrated with an aircraft flight management system (FMS) (20).

18. Werkwijze voor het bepalen van een instrumentnaderingsprocedure voor een 35 luchtvaartuig, waarbij gebruik wordt gemaakt van een systeem (1) dat is voorzien van: - een databasesysteem (22) met terreingegevens en obstakelgegevens, -25- - een invoerinrichting (23) aan boord van het luchtvaartuig voor het selecteren van een doelpositie (12), - een afbeeldingsinrichting (24) aan boord van het luchtvaartuig voor het afbeelden van informatie voor een piloot van het luchtvaartuig, 5. een processor aan boord van het luchtvaartuig, waarbij de processor is verbonden met de invoerinrichting (23) en met de afbeeldingsinrichting (24), en waarbij de werkwijze omvat: - het door de processor bepalen van een instrumentnaderingsprocedure voor het 10 luchtvaartuig op basis van de geselecteerde doelpositie (12) en de terreingegevens en obstakelgegevens uit het databasesysteem (22), met het kenmerk, dat de processor, op basis van de geselecteerde doelpositie, een eindnaderingsbaansegment (5) en een gemiste-naderingsbaansegment (6) van de 15 instrumentnaderingsprocedure bepaalt, waarbij het eindnaderingsbaansegment (5) is bepaald door een vliegbaan die begint bij een eindnaderingsbaanpunt (10) op een hoogte van het eindnaderingsbaanpunt en eindigt bij een gemiste-naderingspunt (11), op een lagere hoogte dan de hoogte van het eindnaderingsbaanpunt, voor het besluiten of het luchtvaartuig verder kan gaan naar een landingspositie (12) op de grond of een gemiste-20 naderingsprocedure wordt gestart, en waarbij het gemiste-naderingsbaansegment (6) is bepaald door een vliegbaan die begint bij het gemiste-naderingspunt (11) en eindigt op een hogere hoogte dan de hoogte van het gemiste-naderingspunt (11), waarbij het gemiste-naderingsbaansegment (6) wordt gevolgd door het luchtvaartuig als op het gemiste-naderingspunt (11) wordt besloten dat de gemiste-naderingsprocedure wordt gestart, en 25 het systeem is voorzien van een geheugen met obstakelvrij-vlakgegevens, op basis waarvan, voor elk van het eindnaderingsbaansegment (5) en het gemiste-naderingsbaansegment (6), ten minste een obstakelvrij vlak (30) is bepaald dat zich uitstrekt met een vooraf bepaalde oriëntatie en op een vooraf bepaalde afstand onder dat baansegment (5, 6), en 30 de processor een obstakelvrije hoogte (OCA) voor de instrumentnaderingsprocedure bepaalt als de laagste hoogte waarbij elk obstakel dat is geïdentificeerd door de terreingegevens en obstakelgegevens in het databasesysteem (22) geen van de obstakelvrije vlakken (30) in het eindnaderingsbaansegment (5) en het gemiste-naderingsbaansegment (6) penetreert, en 35 de obstakelvrije hoogte (OCA) wordt afgebeeld op de afbeeldingsinrichting (24).18. Method for determining an instrument approach procedure for an aircraft, using a system (1) which is provided with: - a database system (22) with terrain data and obstacle data, -25- - an input device (23) on aboard the aircraft for selecting a target position (12), - an imaging device (24) aboard the aircraft for displaying information for an aircraft pilot, 5. a processor on board the aircraft, the processor is connected to the input device (23) and to the imaging device (24), and wherein the method comprises: - the processor determining an instrument approach procedure for the aircraft based on the selected target position (12) and the terrain data and obstacle data from the database system (22), characterized in that the processor, based on the selected target position, a final approach track segment (5) and a mean defines the approach track section (6) of the instrument approach procedure, wherein the final approach track section (5) is defined by a flight path that starts at a final approach track point (10) at a height of the final approach track point and ends at a missed approach track point (11), at a lower than the height of the final runway point, for deciding whether the aircraft can proceed to a landing position (12) on the ground or a missed approach procedure is started, and where the missed approach track segment (6) is determined by a flight path starting at the missed approach point (11) and ending at a height higher than the height of the missed approach point (11), the missed approach track segment (6) being followed by the aircraft as at the missed approach point (11) it is decided that the missed approach procedure is started, and the system is provided with a memory with obstacle-free area data, on the basis of which, for each of the final approach track section (5) and the missed approach track section (6), at least one obstacle-free surface (30) is defined which extends with a predetermined orientation and at a predetermined distance below that track section (5, 6), and the processor determines an obstacle-free height (OCA) for the instrument approach procedure as the lowest height at which any obstacle identified by the terrain data and obstacle data in the database system (22) does not include any of the obstacle-free surfaces (30) in the final approach track (5) and missed approach path section (6) penetrates, and the obstacle-free height (OCA) is imaged on the imaging device (24).