PROCEDURE FOR LOCATION OF AN AIRCRAFT IN FLIGHT

Description

[0001] The present invention relates to a method for locating an aircraft in flight. The present invention also relates to an associated locating device. The present invention also relates to an aircraft comprising such a locating device.

[0002] Aircraft are typically equipped with on-board equipment to assist in piloting the aircraft. In particular, when visibility conditions are reduced (fog, snow, heavy rain), the crew or pilot of the aircraft refers to such equipment, for example, for the approach and landing phases.

[0003] To enable the proper functioning of this equipment, the aircraft includes aircraft location devices generally based on inertial sensors and / or radio navigation sensors.

[0004] However, such location devices have operational limitations. In particular, the locations obtained by inertial sensors are not sufficiently precise. Radio navigation sensors, on the other hand, are highly dependent on the environment and are therefore susceptible to interference or failure.

[0005] Documents US 10,705,201 B and EP 3,179,275 A describe examples of localization methods.

[0006] There is therefore a need for a method for consolidating conventional aircraft location solutions.

[0007] To this end, the present invention relates to a location method according to claim 1.

[0008] According to other advantageous aspects of the invention, the method comprises one or more of the features of claims 2 to 9.

[0009] The present invention further relates to a locating device according to claim 10.

[0010] The invention also relates to an aircraft according to claim 11.

[0011] Other features and advantages of the invention will become apparent upon reading the following description of embodiments of the invention, given by way of example only, and with reference to the drawings which are: [ Fig 1] figure 1 , a schematic representation of an aircraft in flight, the area flown over by the aircraft being a landing site for the aircraft comprising a landing strip, [ Fig 2] figure 2 , a schematic representation seen from above of an example of a landing strip and the horizontal projection of an aircraft radar in the horizontal plane of the landing strip, [ Fig 3] figure 3 , a schematic representation of an example of the location device calculator, [ Fig 4] figure 4 , a flowchart of an example of a localization method, and [ Fig 5] figure 5 , a flowchart of an example of the second phase of determining a position of the localization process of the figure 4 .

[0012] An area of ​​space 9 and an aircraft 12 in flight above the area of ​​space 9 are illustrated by the figure 1 .

[0013] In this particular example, the area of ​​space 9 is a landing site, more precisely a runway 10, and the aircraft 12 is an airplane. In this example, the aircraft 12 is approaching the runway 10 for a landing on this runway 10.

[0014] As illustrated by the figure 2 , the landing runway 10 is a rectangular surface intended for the landing and takeoff of aircraft. The landing runway 10 comprises longitudinal edges (two) and transverse ends (two) delimiting the landing runway 10.

[0015] The length of runway 10 is, for example, between 3 kilometers (km) and 4 km. The width of runway 10 is, for example, between 25 m and 45 m.

[0016] In the example illustrated by the figure 2 , the landing runway 10 has a longitudinal axis in the longitudinal direction of the runway 10 and at an equal distance from the longitudinal edges of the runway 10. This longitudinal axis is called the axis of the runway Y. An axis perpendicular to the axis of the runway Y is also shown on the figure 2 , by the reference “X”.

[0017] The landing runway 10 comprises a set of characteristic elements 16. For the sake of clarity, only certain characteristic elements 16 are numbered on the figure 2 . The characteristic elements 16 are, for example, lamps, also called light beacons. Alternatively, the characteristic elements 16 are radar reflectors (trihedral type or Luneberg lenses). As a further variant, the characteristic elements 16 are other elements existing on a landing strip.

[0018] In this example, the characteristic elements 16 are distributed on the landing strip 10 in at least two longitudinal rows 18A, 18B and at least one transverse row 20.

[0019] The longitudinal rows 18A, 18B are substantially parallel to the axis of the runway Y. Two of the longitudinal rows 18A, 18B are each arranged along a distinct longitudinal edge of the runway 10. By the term “arranged along”, it is understood that the rows are arranged less than three meters from the corresponding longitudinal edge.

[0020] The or each transverse row 20 is substantially perpendicular to the axis of the track Y. In the example illustrated by the figure 2 , the landing runway 10 comprises three transverse rows 20A, 20B, 20C of characteristic elements 16. The last transverse row 20A in the direction of landing of the aircraft on the runway 10 is called the runway threshold (row 20A in the example of the figure 2 ).

[0021] Alternatively, the landing runway 10 comprises at least three longitudinal rows: the two longitudinal rows 18A, 18B and a third longitudinal row 18C (not shown) arranged along the axis of the runway Y and downstream of the runway threshold.

[0022] Those skilled in the art will understand that this example is given for illustrative purposes. The area of ​​space 9 is more generally an overflown area comprising on the ground on a relief or a known surface predetermined characteristic elements 16 (reflectors) arranged in at least one row. The area of ​​space 9 is therefore, for example, a landing site not comprising a landing strip or a control zone not allowing the aircraft 12 to land. Furthermore, the aircraft 12 is, as a variant, a helicopter or a drone.

[0023] The aircraft 12 comprises an electronic location device 24. The location device 24 is carried by the aircraft 12.

[0024] An example of a 24 location device is illustrated by the figure 1 In this example, the location device 24 comprises a first location unit 26, a second location unit 28 and a computer 29.

[0025] The first location unit 26 implements a location solution, called conventional, chosen from an inertial location solution, a radio navigation location solution and a solution resulting from the combination of the inertial and radio navigation solutions.

[0026] The first location unit 26 comprises at least one sensor chosen from an inertial sensor and a radio navigation sensor. The inertial sensor is, for example, an accelerometer, a gyrometer or a gyroscope. The radio navigation sensor is, for example, a GPS (acronym for “Global Positioning System”).

[0027] More specifically, in the case of a radio navigation solution, the first location unit 26 comprises, for example, a VOR system (abbreviation for "VHF Omnidirectional Range"), a DME system (abbreviation for "distance measuring equipment"), a GPS system, an SBAS system, a GBAS system or an ILS system. Such systems meet, for example, the requirements of various types of landing approaches (NPA, LNAV, VNAV, LPV, ILS, etc.).

[0028] The second location unit 28 implements a radar location solution.

[0029] The second location unit 28 comprises at least one radar 32 in communication with a computer, such as the computer 29 of the location device 24. In a variant, the second location unit 28 comprises a computer of its own to directly process the measurements carried out by the radar 32.

[0030] Radar 32 defines a reference mark shown on the figure 1 by a Cartesian reference frame with center OR, abscissa XR, ordinate YR and elevation ZR. The ordinate axis YR is the longitudinal axis of detection and is called the radar axis. When the radar 32 is correctly positioned on the aircraft 12, the radar axis YR substantially coincides with the trajectory of the aircraft 12.

[0031] The radar 32 is advantageously a millimeter wave radar. Preferably, the distance resolution of the radar is of the order of a few meters, and the angular resolution of the radar is fine, that is to say of the order of a few tenths of a degree.

[0032] The radar 32 preferably comprises at least three reception channels making it possible to measure, for each detection, the radial distance of the detection, the circular angle in the reference frame of the radar 32 of the detection and the elevation angle in the reference frame of the radar 32 of the detection. The radial distance of any point M is its distance from the origin OR of the reference frame. The circular angle, or the circular, is the angle of the projection onto the plane (ORXRYR ) of the angle carried by the axis (ORYR ) and the straight line (ORC) passing through the target point C. The elevation angle is the angle formed between the plane (ORXRYR ) of the radar 32 and the straight line going from the radar 32 to the target point C.

[0033] Calculator 29 is, for example, a computer.

[0034] In the example illustrated by the figure 3 , the computer 29 comprises a processor 40 comprising a data processing unit 42, memories 44, an information medium reader 46 and, optionally, a human-machine interface 48 comprising a keyboard 50 and a display 52.

[0035] The processing unit 42 interacts with a computer program product. The computer program product comprises an information medium. The information medium is a medium readable by the processing unit 42. The readable information medium is a medium suitable for storing electronic instructions and capable of being coupled to a bus of a computer system.

[0036] For example, the information medium is a USB key, a floppy disk or a flexible disk (from the English term " Floppy disc "), an optical disc, a CD-ROM, a magneto-optical disc, a ROM memory, a RAM memory, an EPROM memory, an EEPROM memory, a magnetic card or an optical card.

[0037] The computer program, including program instructions, is stored on the information medium.

[0038] The computer program is loadable onto the data processing unit 42 and is adapted to cause the implementation of a location method which will be described in the remainder of the description.

[0039] In another example, the computer 29 is implemented in the form of one or more programmable logic components, such as FPGAs (from the English Field Programmable Gate Array ), or in the form of one or more dedicated integrated circuits, such as ASICs (from the English Application Specific Integrated Circuit ). The calculator 29 is in this case configured to implement a location method as will be described in the remainder of the description.

[0040] The operation of the locating device 24 will now be described with reference to the figure 4 which schematically illustrates an example of implementation of a localization process.

[0041] The localization method is intended to be implemented during an overflight of an area comprising characteristic elements 16 on the ground. In particular, the localization method is particularly suitable for the phases of approach by the aircraft 12 to a landing site with a view to the landing of the aircraft 12.

[0042] The localization process is advantageously implemented in real time, that is to say at every moment.

[0043] The localization method comprises a first phase 100 of determining a position of the aircraft 12, called the first position, by the first localization unit 26 as a function of a signal provided by the or at least one sensor of the first unit 26.

[0044] The first position is thus obtained by a conventional inertial and / or radio navigation method. The first position gives rise to first coordinates.

[0045] Advantageously, at the end of the first determination phase 100, the speed of the aircraft 12 is also obtained.

[0046] The location method comprises a second phase 110 of determining a position of the aircraft 12, called the second position, by the second location unit 28.

[0047] The second determination phase 110 is implemented simultaneously with the first determination phase 100, the aim being to evaluate the position of the aircraft 12 at the same time. An example of implementation of the second determination phase 110 is illustrated by the figure 5 .

[0048] The second determination phase 110 comprises a step 200 of detection, by the radar 32, of characteristic elements 16 of the area flown over, in particular of the landing runway 10 in the example of figures 1 And 2 .

[0049] Each detection is associated with coordinates. In particular, each detection is defined by a radial distance, a circular angle in the radar reference frame 32 and an elevation angle in the radar reference frame 32. At the end of the detection step, a radar image is thus obtained on which the detections are represented.

[0050] Equivalently, after changing the reference frame, each detection can be defined by a radial distance D, a site angle S, defined relative to the local horizontal of the aircraft 12 and a bearing angle G, defined relative to the longitudinal axis of the aircraft 12.

[0051] For example, to go from coordinates (elevation, circular) = (E,C) to (site, bearing) = (S,G), we start by calculating the direction vector in Cartesian ux = cosE.cosC, uy = cosE.sinC and uz = sinE. We then apply to this vector the rotation matrix corresponding to the opposite of the radar setting angle in elevation, then the rotation matrix corresponding to the opposite of the aircraft roll, then the rotation matrix corresponding to the opposite of the aircraft pitch. The vector obtained is in Cartesian coordinates in the horizontal reference frame local to the aircraft and the values ​​of the site and bearing are obtained by performing the transformation from Cartesian to polar. Such an operation requires knowing the elevation setting angle of the radar (linked to the mechanical installation of the radar on the aircraft), the roll and pitch of the aircraft, generally provided by the aircraft's inertial unit.

[0052] Advantageously, the radar 32 applies a constant false alarm rate (CFAR) type processing to the obtained radar image, which allows for better detection of the characteristic elements 16. Thus, temporally, a “radar image” is first formed from the signals backscattered by the ground and received by the radar. CFAR processing is applied to this image, which makes it possible to provide a list of detections with their coordinates.

[0053] The second determination phase 110 comprises a step 210 of determining, as a function of the coordinates of the characteristic elements 16 detected, the angular offset T between the axis of the radar YR and a straight line parallel or perpendicular to the or at least one of the rows of elements, called the reference straight line. The reference straight line is a straight line predetermined as a function of the area flown over and the geometry of the characteristic elements 16 on the area flown over. In the example illustrated by the figures 1 And 2 , the reference line is the axis of the track Y. The determination step 210 is implemented by the calculator 29.

[0054] The step of determining the angular offset T includes for example: the conversion of the coordinates of each detection into Cartesian coordinates, for each angular offset value T test included in a range of predetermined values, the determination, for each detection, of a Cartesian coordinate along the abscissa axis, corrected by the value of said angular offset T test, for each angular offset value T test included in the range of predetermined values, the determination of the number of detections corresponding to each Cartesian coordinate corrected along the abscissa axis, the angular offset value T test associated with the greatest number of detections being the angular offset T between the radar axis YR and the reference line.

[0055] A more specific example of determining the angular offset T is given when the reference line is the Y axis of the landing runway 10 ( figures 1 And 2). In this example, the fact that the characteristic elements 16 are aligned in rows parallel to the axis of the track Y is exploited.

[0056] In this example, the step of determining the angular offset T includes converting the coordinates of the detected elements into Cartesian coordinates. The Cartesian coordinates are given by the following formulas: x = D . cos S . sin G y = D . cos S . cos G

[0057] Or : x denotes a Cartesian coordinate along the abscissa axis, y denotes a Cartesian coordinate along the ordinate axis, D denotes the radial distance, S denotes the elevation angle, and G denotes the bearing angle.

[0058] Then, the determination step 210 comprises, for angular offset test values ​​T test , the determination, for each detection, of a Cartesian coordinate along the abscissa axis, corrected by the value of said angular offset T test . The angular offset test values ​​T test are the values ​​included in a predetermined range of values ​​with a predetermined step. The range of values ​​is, for example, between -10 degrees (°) and 10 ° and the predetermined step equal to one tenth of a degree. Thus, for each angular offset test value T test , the Cartesian coordinates along the abscissa axis of the detections are obtained by the following formula: x = D . cos S . sin G + T test

[0059] Then, for each angular offset test value T test , the determination step 210 comprises determining the number of detections corresponding to each Cartesian coordinate corrected along the abscissa axis. The angular offset value T test associated with the largest number of detections is the angular offset T between the radar axis YR and the track axis Y. This amounts to producing, for each angular offset test value T test , a histogram of the positions along the abscissa axis (in x) and counting, for each interval along the x axis, the number of detections whose position in x gives the highest peak (whatever the value of x), which reflects the fact that the detections have been aligned as best as possible with respect to the track axis Y.

[0060] Optionally, the angular shift T is refined by searching for the position of the maximum of the second-order regression around this peak.

[0061] In a second example, the angular offset T is obtained by performing a principal component analysis (PCA) of the list of detections. In this case, the covariance matrix of the pairs (x,y) is first calculated, which allows the eigenvectors and finally the angular offset T to be deduced.

[0062] In a third example, the angular offset T is obtained by applying a Hough transform to the list of detections, and the accumulation point gives the angular offset T

[0063] The second and third examples, however, give less robust results than the first example, because each characteristic element does not always correspond to a detection (probability of detection < 1), or some detections may not be characteristic elements 16 (other objects near the track which could lead to a detection, or false alarm).

[0064] At the end of the determination step 210, the coordinates of the Cartesian detections corrected for the angular offset T, called optimal Cartesian coordinates, are given by the following formulas: x = D . cos S . sin G + T y = D . cos S . cos G + T

[0065] The second determination phase 110 comprises a step 220 of determining the relative position of the aircraft 12 with respect to the area flown over as a function of the determined angular offset T and the coordinates of the detected characteristic elements 16. The determination step 220 is implemented by the computer 29.

[0066] To do this, the distance of the orthogonal projection on the line passing through the or at least one of the rows of elements of the horizontal projection PH of the radar, called the first distance D1, is determined. The horizontal projection PH of the radar is the orthogonal projection of the position of the radar on the ground.

[0067] The distance of the orthogonal projection on a straight line, perpendicular to the or at least one of the rows of elements, of the horizontal projection PH of the radar, called the second distance D2, is also determined.

[0068] The second position of the aircraft 12 is then obtained as a function of the first distance D1 and the second distance D2 determined.

[0069] In the case where the area flown over is a landing strip (example of figures 1 And 2), the first distance D1 is the distance of the orthogonal projection on the axis of the runway Y of the horizontal projection PH of the radar 32, called axial offset DA . The horizontal projection PH of the radar 32 is the orthogonal projection of the position of the radar 32 in the horizontal plane of the runway 10. The second distance D2 is the distance of the orthogonal projection on the line passing through the runway threshold of the horizontal projection PH of the radar 32, called distance to the runway threshold D SHT .

[0070] A more specific example of determining the axial offset DA and the distance to the runway threshold D SHT is given in the following.

[0071] For example, the axial offset DA is obtained by determining a histogram of the positions along the abscissa axis of each detection as a function of the optimal Cartesian coordinates of each detection. The histogram obtained has as many peaks as there are longitudinal rows of characteristic elements 16 on the runway 10. Consequently, the histogram comprises at least two lateral peaks corresponding to the two longitudinal rows 18A, 18B extending along the longitudinal edges of the landing runway 10. The axial offset DA corresponds, for example, to the average of the coordinates along the abscissa axis (in x) of the two lateral peaks.

[0072] Alternatively, when the track 10 further has a longitudinal row of characteristic elements 16 extending along the axis of the track Y, the histogram obtained also has a central peak between the two lateral peaks. In this case, the axial offset DA is, for example, the x-position of the central peak.

[0073] For example, the distance to the runway threshold D SHT is obtained by determining a histogram of the positions along the y-axis of each detection as a function of the optimal Cartesian coordinates of each detection. The histogram obtained has as many peaks as there are transverse rows of characteristic elements 16 on the runway 10. The distance to the runway threshold D SHT is in this case the coordinate along the y-axis (in y) of the most distant peak, that is to say the peak having the largest y-coordinate.

[0074] Optionally, the second determination phase 110 also comprises a step 230 of determining the horizontal speed of the aircraft 12 relative to the reference line (axis of the runway Y in the case of figures 1 And 2 ) expressed according to two components Vx, Vy as a function of the variation over time of the first distance D1 and the variation over time of the second distance D2. The Vx component is the component of the velocity projected onto the abscissa axis. The Vy component is the component of the velocity projected onto the ordinate axis. The determination step 140 is implemented by the computer 29.

[0075] An example of the implementation of this step is given in the case of figures 1 And 2 (runway 10).

[0076] In particular, the variation over time of the distance to the runway threshold D SHT gives the Vy component of the speed, and the variation over time of the axial offset DA gives the Vx component of the speed. For example, such variations over time are calculated using a Kalman filter.

[0077] The location method comprises a phase 120 of comparing data associated with the first position determined during phase 100 and data associated with the second position determined during phase 110. At the end of this comparison phase 120, the first position is validated or invalidated. For example, when the first position is invalidated, an alert is triggered. The comparison phase 120 is implemented by the computer 29.

[0078] In a first embodiment of the comparison phase 120, the first position is compared to the second position with a view to validating or not validating the first position. In particular, the first position is associated with a first standard deviation and the second position is associated with a second standard deviation. The uncertainty in the first position is represented by a first ellipsoid whose center is the first position and the radius is a function of the first standard deviation. The uncertainty in the second position is represented by a second ellipsoid whose center is the second position and the radius is a function of the second standard deviation. The comparison phase comprises invalidating the first position when the first ellipsoid and the second ellipsoid are disjoint, in particular when the second ellipsoid is not included in the first ellipsoid. In this case, an alert is, for example, triggered.

[0079] An example of implementing this comparison is given in the following. For each of the location data ( d = noted position p , or noted speed v ) of the aircraft (noted A ) from the 2 sources ( s = primary source (inertial and / or radio navigation sensor, phase 100) noted in capital letters P Or V, or secondary source (radar, phase 110) noted in lowercase p Or v ), let us name σ d_s_e its standard deviation along the direction of the axis e (X, Y, Z) of a spatial Cartesian reference frame linked to the track (ReperePiste): σ d_s_e is the square root of the diagonal term of row e of the covariance matrix MatCov_d_s A [ReperePiste] and MatCov_P A [ReperePiste] represents the covariance matrix of the position ( P ) of the aircraft ( A ) from the primary source ( P in capital letters) and expressed in the reference ReperePiste.

[0080] So, σ d_s_X , σ d_s_Y And σ d_s_Z represent respectively the lateral, longitudinal and vertical standard deviations of the location data of the aircraft to be guided.

[0081] The distance between the location data from the two sources is calculated in the ReperePiste reference frame by the Euclidean norm: Δ Position = P A p A → et Δ Vitesse = V A → − v A →

[0082] Let's call it Δ d_e the projection of the distance between the location data (d = position, speed), from the two sources, on the axes (e = X, Y and Z) of the ReperePiste.

[0083] Let's call Max d_e the maximum permissible uncertainty of the location data d on the e axis. This maximum uncertainty is, for example, known.

[0084] Let's rename P SensorError ( i ) = ProbaErr d_s the acceptable probability of error in the location data d from the source s.

[0085] Let's name k d_s the coefficient applied to the standard deviation of the location data d from the source s to ensure a protection radius consistent with the integrity objective of this source: k d _ s = norminv 1 − ProbaErr d s 2 Or k d_s · σ d_s _ e represents the uncertainty of the data d from the source s and following the axis e.

[0086] An integrity alert is raised on the location data d if the following relation is satisfied on any (at least) of the three axes e ( s1 = primary source and s2 = secondary source of location data d ) : Δ d _ e + k d _ s 1 ⋅ σ d _ s 1 _ e > Max d _ e Or Δ d _ e + k d _ s 2 ⋅ σ d _ s 2 _ e > k d _ s 1 ⋅ σ d _ s 1 _ e

[0087] By applying this algorithm and under the assumption of independence of the sources s1 And s2 , the error probability resulting from the location data d : P SystemError _ d = ProbaErr d _ s 1 ⋅ ProbaErr d _ s 2 .

[0088] This comparison phase makes it possible to contain the resulting localization error within limits and with a level of integrity consistent with the safety objectives set for the flight phase. This is made possible in particular by the fact that the radar localization solution described above is independent of conventional solutions (inertial and radio navigation).

[0089] The person skilled in the art will understand that this comparison phase 120 comprises a prior step of changing the reference frame of the coordinates of the first position and the second position obtained to place them in the same geometric reference frame. Indeed, the second position is, for example, expressed in the reference frame linked to the ground (landing runway for example), whereas the first position is, for example, expressed in the terrestrial geographical reference frame WGS-84. For example, given that the approach and landing constraints are expressed relative to the landing runway, the first position and the second position are preferably brought back into the reference frame of the landing runway.

[0090] In a second embodiment, the comparison phase 120 comprises the display, on a display of the location device 24, of an image of the area flown over determined from a set of images in a database as a function of the first position. The image is in fact chosen as a function of the first position so as to display the current area flown over by the aircraft 12. The displayed image therefore comprises the characteristic elements of the area flown over by the aircraft 12. The database is, for example, stored in a memory of the computer 29.

[0091] Such a display is, for example, of the SVGS type (in English "Synthetic Vision Guidance Systems"). SVGS is an instrument approach procedure with vertical guidance that reduces the decision height to 150 feet compared to the standard height of 200 feet for a Category I approach. Such an approach is notably defined in the RTCA DO-359, AC 20-167A and AC 20-185 standards. In SVGS, the location of the aircraft 12 is the basis of both the guidance system and the synthetic display system.

[0092] The display phase further comprises the superposition on the displayed image of a representation of the characteristic elements 16 of the area flown over, these represented elements having been detected by the radar 32 during the determination of the second position. The representations of the characteristic elements 16 are for example symbols, such as crosses or circles. These representations aim to represent the characteristic elements 16 by their position.

[0093] The first position is then validated when the representations of the characteristic elements 16 superimposed on the image have substantially the same position on the image as the corresponding characteristic elements 16 already present on the image. The first position is invalidated otherwise. This also makes it possible to give more information to the pilot and to reassure him about the viability of the location carried out.

[0094] Thus, in this embodiment, the data associated with the first position comprises the image determined in the database as a function of the first position. The data associated with the second position comprises the representations of the characteristic elements 16 detected by the radar and from which the second position was obtained.

[0095] It should be noted that the first mode of implementation and the second mode of implementation of the comparison phase 120 are suitable for being combined.

[0096] Optionally, the localization method comprises a phase 130 of modifying the trajectory of the aircraft 12 when the first position is invalidated, for example when an alert is triggered. The modification phase 130 is implemented by the computer 29. Optionally, this phase is implemented automatically (autopilot). Alternatively, it is implemented by the pilot or by the crew.

[0097] Typically, the trajectory modification consists of the aircraft 12 regaining altitude when the conditions for a landing are not met, i.e. an alert has been triggered.

[0098] Optionally, when the first position has been validated, the localization method comprises a phase 140 of merging the first and second positions to obtain an optimized position. This makes it possible to increase the precision of the localization obtained.

[0099] In an exemplary implementation, the fusion phase 140 comprises the fusion of the locations obtained during the first determination phase 100 and the second determination phase 110 by means of a Kalman filter.

[0100] Thus, the present method makes it possible to consolidate a location carried out by a conventional location method (inertial, radio navigation) via radar location. In particular, when the safety objectives of air navigation cannot be achieved using conventional location methods (for example during approach and landing phases without visibility), radar location makes it possible to validate the conventional location.

[0101] In this way, the process allows to increase the level of integrity and / or continuity and / or precision of one or more conventional localization solutions. Localization is thus more reliable and secure.

[0102] The automatic guidance of an aircraft (autopilot) is based on the deviation of its position from the ideal approach trajectory (in English "final approach segment"). The lateral and vertical deviations are, for example, expressed in metric or angular form (standard DO-253). In approach and landing of category higher than I, the standard AC 120-118 requires a localization solution integrity better than 1 - 10 -7< and an angular accuracy better than 0.2° in vertical and better than 0.4° in lateral. The present method makes it possible to achieve such levels of integrity by consolidating a conventional localization method with the described radar method.

[0103] For example, the method is suitable for use during a descent phase of an aircraft below 200 feet in height and landing on a runway with no visibility using a conventional location solution of the ILS (Instrument Landing System) category I and / or LPV (precision approach with satellite vertical navigation) type augmented by the radar location solution described previously.

[0104] For example, in the approach and landing phase, below a decision altitude or height, the crew or pilot must have acquired the visual references necessary for landing (approach light ramps, threshold and edge of runway, touchdown zone). The location device 24 makes it possible to lower the decision threshold below the usual values ​​since they are determined by conventional location solutions. Thus, when this is not possible, and an alert is triggered, the approach for landing is interrupted and the aircraft regains altitude.

[0105] The radar localization implemented does not require an image database and can therefore be used on all types of overflown areas, even when it is not referenced. The radar solution implemented is also simpler to install on an aircraft, unlike a solution based on a database occupying a large memory volume. In addition, the described process does not require any modifications or additions to the infrastructure of the landing site (airports).

[0106] Those skilled in the art will understand that the embodiments described above are capable of being combined with each other when such a combination is compatible.

[0107] For example, one of the application examples concerns the landing of the aircraft on a runway. However, the present method also applies to other landing locations, such as heliports in the case of helicopters, or landings outside a conventional landing location. Similarly, the present method applies to other flight phases, such as taxiing, takeoff, cruising or descent.

Claims

1. Method for locating an aircraft (12) in-flight, the aircraft (12) overflying a zone of space (9) comprising on the ground, characteristic elements (16) arranged in at least one row (18A, 18B, 20A, 20B, 20C), the locating method being implemented by a locating device (24) borne by the aircraft (12), the locating device (24) comprising a first locating unit (26) and a second locating unit (28), the first locating unit (26) comprising at least one sensor selected from an inertial sensor and a radionavigation sensor, the second locating unit (28) comprising a radar (32), the overflown zone being a landing site of the aircraft (12) and the characteristic elements (16) being characteristic elements of the landing site, such as beacons, the landing site comprising a runway (10) having a longitudinal axis equidistant from the longitudinal edges of the runway, called runway centerline (Y), the characteristic elements (16) being distributed over the runway (10) in at least two longitudinal rows (18A, 18B) and at least one transverse row (20A, 20B, 20C), the longitudinal rows (18A, 18B) being substantially parallel to the runway centerline (Y), two of the longitudinal rows (18A, 18B) being each arranged along a distinct longitudinal edge of the runway (10), the or each transverse row (20A, 20B, 20C) being substantially perpendicular to the runway centerline (Y), the last transverse row (20A) along the direction of aircraft landing on the runway (10) being called the runway threshold, the method comprising: a. a first phase of determining a position of the aircraft (12), called first position, by the first locating unit (26) as a function of a signal supplied by the or at least one sensor, b. simultaneously with the first determination phase, a second determination phase of a position of the aircraft (12), called second position, by the second locating unit (28), the second determination phase comprising: i. the detection, by the radar (32), of the characteristic elements (16) of the zone overflown, each detection being associated with coordinates, ii. the determination, according to the coordinates of the detected elements, of:

1. the distance of the orthogonal projection on the straight line passing through the or at least one of the rows (18A, 18B, 20A, 20B, 20C) of elements of the horizontal projection (PH) of the radar (32), called the first distance (D1), the horizontal projection (PH) radar (32) being the orthogonal projection of the position of radar (32) on the ground, the first distance (D1) being the distance from the orthogonal projection on the runway centerline (Y) of the horizontal projection (PH) of the radar (32), called axial offset (DA), 2. the distance of the orthogonal projection on a line perpendicular to the or at least one of the rows (18A, 18B, 20A, 20B, 20C) of elements, the horizontal projection (PH) of the radar (32), called the second distance (D2), the second distance (D2) being the distance from the orthogonal projection on the straight line passing through the runway threshold of the horizontal projection (PH) of the radar (32), called the distance to the runway threshold (DSHT), iii. determining the second position according to the determined first and second distances (D1, D2). c. a phase of comparing data associated with the first position and data associated with the second position after which the first position is either validated or invalidated.

2. The method according to claim 1, wherein the comparison step comprises triggering an alert when the first position is invalidated, the method comprising a phase of modifying the trajectory of the aircraft (12) when an alert is triggered.

3. The method according to claim 1 or 2, wherein the first position is associated with a first standard deviation and the second position is associated with a second standard deviation, the uncertainty on the first position showing as a first ellipsoid, the center of which is the first position and the radius of which depends on the first standard deviation, the uncertainty on the second position showing as a second ellipsoid, the center of which is the second position and the radius depends on the second standard deviation, the first position being invalidated during the comparison phase when the second ellipsoid and the first ellipsoid are disjoint.

4. The method according to claim 3, wherein when the first position has been validated, the method comprises a step of merging the first and second positions so as to obtain an optimized position of the aircraft (12).

5. The method according to any of claims 1 to 4, wherein the comparison phase comprises the display, on a display of the locating device (24), of an image of the zone overflown which was determined, according to the first position, from a set of images in a database, the displayed image comprising the characteristic elements of the zone overflown by the aircraft (12), the comparison phase further comprising the superposition over the displayed image of a representation of the characteristic elements (16) of the zone overflown which were detected by the radar (32) during the determination of the second position, the first position being validated when the characteristic elements superimposed over the image have substantially the same position on the displayed image as the corresponding characteristic elements already present on the displayed image, and being invalidated otherwise;6. The method according to any of claims 1 to 5, wherein the step of determining the second position comprises the determination of the angular offset (T) between the radar axis (YR) and a line parallel or perpendicular to the or at least one of the rows (18A, 18B, 20A, 20B, 20C) of elements, called the reference line, the first distance (D1) and the second distance (D2) being determined according to the determined angular offset.

7. The method according to claim 6, wherein in the step of determining the second position, the determination the angular offset (T) comprises: a. the conversion of the coordinates of each detection into Cartesian coordinates, b. for each value of angular offset (Ttest) comprised within a range of predetermined values, the determination, for each detection, of a Cartesian coordinate along the abscissa axis, corrected for the value of said angular offset (Ttest), c. for each angular offset value (Ttest) within the range of predetermined values, the determination of the number of detections corresponding to each Cartesian coordinate corrected along the abscissa axis, the angular offset value (Ttest) associated with the greatest number of detections being the angular offset (T) between the radar axis (YR) and the reference line.

8. The method according to claim 6 or 7, wherein the reference line is the runway centerline (Y), during the phase of determining the second position, the distance determination comprises: a. the calculation of the Cartesian coordinates of each detection, corrected for the angular offset (T) determined in the determination step, called optimal Cartesian coordinates, b. the determination of a histogram of the positions along the x-axis of each detection as a function of the optimal Cartesian coordinates of each detection, the histogram having at least two peaks, and c. the determination of the axial offset (DA) according to the Cartesian coordinates along the abscissa axis of at least the two peaks of the histogram.

9. The method according to any of claims 6 to 8, wherein the reference line is the runway centerline (Y), during the phase of determining the second position, the distance determination comprises: a. the calculation of the Cartesian coordinates of each detection, corrected for the angular offset (T) determined in the determination step, called optimal Cartesian coordinates, b. the determination of a histogram of the y-axis positions of each detection according to the optimal Cartesian coordinates of each detection, the histogram having at least one peak, and c. the determination of the distance to the runway threshold (DSHT) according to the Cartesian coordinates along the y-axis of the peak(s) of the histogram.

10. A device (24) for locating an aircraft (12) in-flight, the aircraft (12) overflying a zone of space (9) comprising on the ground, characteristic elements (16) arranged in at least one row (18A, 18B, 20A, 20B, 20C), the electronic locating device (24) being borne by the aircraft (12), the locating device (24) comprising a first locating unit (26) and a second locating unit (28), the first locating unit (26) comprising at least one sensor selected from an inertial sensor and a radionavigation sensor, the second locating unit (28) comprising a radar (32), the locating device being configured for implementing a method according to any of claims 1 to 9.

11. An aircraft comprising a locating device (24) according to claim 10.