Method for locating a vertical take-off and landing (VTOL) aircraft relative to a landing area, and associated method and devices

Abstract

The present invention relates to a method for locating an aircraft (2) relative to a VTOL landing area (4) comprising at least one element (20A, 20B, 22A, 22B) that is reflective to a radio signal, the method comprising the following steps: - transmitting a radio signal from the aircraft (2) to the landing area (4), - receiving a signal reflected by the landing area (4) in response to the signal, - extracting a pattern from the received reflected signal, each pattern being the variation over time in the radio signal reflected by one reflective element (20A, 20B, 22A, 22B), - calculating a vertical distance (D y ) from the pattern, and - determining a vertical location of the aircraft (2) in relation to the landing area (4) depending on the vertical distance (D y ).

Description

[0001] Method for locating a vertical landing aircraft relative to a runway, method and associated devices

[0002] The present invention relates to a method for locating an aircraft relative to a runway. The present invention also relates to a control method and associated devices, namely a locating device and a runway.

[0003] The invention relates to the field of aircraft, in particular autonomous vertical landing aircraft, more particularly the field of localization of the latter during takeoff and landing.

[0004] It is essential to be able to locate an aircraft in relation to the runway on which it can land or take off in order to guarantee a satisfactory level of safety during takeoff and landing phases.

[0005] The so-called "vertical" landing of certain aircraft involves specific landing procedures and the use of runways adapted to these procedures commonly called heliport or vertiport.

[0006] Typically, the tracks are circular in shape and have a diameter of around 25 meters (m).

[0007] The approach speed of an aircraft seeking to land on such a runway implies rapid localization of the aircraft.

[0008] For this purpose, there is known in ILS technology (from the English, "Instrument Landing System") a reference system with regard to the location of an aircraft in relation to a runway during the landing phase.

[0009] This technology uses transmitting antennas located at the end of the runway, the sum of the signals received by the aircraft being characterized by a carrier and a modulation, themselves a function of the lateral and longitudinal shifts of the aircraft relative to the reference approach axis in the vertical and horizontal plane.

[0010] However, this technology is expensive and therefore not widely deployed, and it does not allow for the detection of any obstacles on the track.

[0011] Furthermore, this technology is not used during takeoff and is not necessarily suitable for a vertical landing.

[0012] Therefore, there is a need for a method of locating a vertical landing aircraft relative to a runway that is easy to implement.

[0013] To this end, the description describes a method for locating an aircraft relative to a runway on which aircraft can land or take off, the runway having a shape suitable for vertical landing and comprising at least one reflective element for a radio signal, the method comprising the following steps: - transmission of a radio signal from the aircraft towards the runway,

[0014] - reception of a signal reflected by the track in response to the emitted radio signal,

[0015] - extraction of at least one pattern in the received reflected signal, each pattern being the evolution over time of the radio signal reflected by at least one reflective element composing a group of reflective elements, called the tracking group,

[0016] - calculation of a vertical distance from at least one pattern, the vertical distance being the distance between the aircraft and a runway center along a first direction normal to the runway, and

[0017] - determination of a vertical location of the aircraft relative to the runway as a function of the vertical distance.

[0018] Depending on other advantageous aspects, the localization process includes one or more of the following characteristics, taken individually or in all technically possible combinations:

[0019] - The vertical distance calculation step includes the following sub-steps:

[0020] - estimation of a phase shift between two patterns, and

[0021] - calculation of the vertical distance by applying a function to the estimated phase shift, the function associating a vertical distance with a phase shift between two patterns,

[0022] - The vertical distance calculation step includes the following sub-steps:

[0023] - estimation of the frequency of at least one pattern, and

[0024] - calculation of the vertical distance by applying a function to the estimated frequency, the function associating a vertical distance as a function of the estimated frequency.

[0025] - each reflective element comprises at least two reflectors, the at least two reflectors being aligned or offset from each other along a second direction transverse to the track and along the first direction.

[0026] - the process also includes the following steps:

[0027] - estimation of two distances: a first distance between the aircraft and a first reflective element and a second distance between the aircraft and a second reflective element;

[0028] - calculation by multilateration of a lateral distance and a longitudinal distance from the first distance, the second distance and the vertical distance, the lateral longitudinal distance being the distance between the aircraft and the center of the runway along a third direction perpendicular to the second direction, and the longitudinal distance being the distance between the aircraft and the center of the runway along the second direction;

[0029] - determination of the aircraft's location based on vertical distance, longitudinal distance, and lateral distance.

[0030] - the radio signal belongs to a frequency band chosen from the X, K, Ka, Ku and W bands.

[0031] The description also relates to a method for controlling an aircraft comprising the following steps:

[0032] - localization of the aircraft by implementing a localization method according to the invention,

[0033] - Estimating the percentage risk of an obstacle being present on the runway based on a ground pattern, the ground pattern being the radio signal reflected by the runway surface, and

[0034] - implementation of an action to interrupt the landing or takeoff of the aircraft based on the determined location and the estimated percentage of risk.

[0035] The description also relates to an electronic device for locating an aircraft relative to a runway on which aircraft can land or take off, the runway having a shape suitable for vertical landing and comprising at least one reflective element for a radio signal, the locating device being configured to:

[0036] - to transmit a radio signal from the aircraft towards the runway,

[0037] - to receive a signal reflected by the track in response to the emitted radio signal,

[0038] - extract at least one pattern from the received reflected signal, each pattern being the evolution over time of the radio signal reflected by at least one reflective element composing a group of reflective elements, called the tracking group,

[0039] - calculate a vertical distance from at least one pattern, the vertical distance being the distance between the aircraft and a runway center along a first direction normal to the runway, and

[0040] - determine a vertical location of the aircraft relative to the runway as a function of the vertical distance.

[0041] The description also relates to a device for controlling an aircraft in relation to a runway on which aircraft can land or take off, the runway having a shape suitable for vertical landing and comprising at least one reflective element for a radio signal, the control device comprising:

[0042] - an aircraft location device according to the invention, - a controller configured for:

[0043] - to estimate the percentage risk of an obstacle being present on the runway based on a ground pattern, the ground pattern being the radio signal reflected by the runway surface, and

[0044] - to carry out an automatic interruption of the landing or takeoff of the aircraft based on the location determined by the location device and the estimated risk percentage.

[0045] The description also describes a runway with a shape suitable for vertical landing and featuring two groups of radio signal reflectors arranged on one edge of the runway.

[0046] Depending on other advantageous aspects, the track includes one or more of the following characteristics, taken individually or in all technically possible combinations:

[0047] - a reflective element comprises at least two trihedral reflectors;

[0048] - the at least two trihedral reflectors of one of the two groups of reflective elements are offset from each other along a first direction normal to the track and along a second direction transverse to the track.

[0049] In the following description, a quantity is substantially equal to a value when the quantity is greater than or equal to 90% of the value and the quantity is less than or equal to 110% of the value.

[0050] The invention will become more apparent upon reading the following description, given solely by way of non-limiting example and made with reference to the drawings in which: Figure 1 is a schematic representation of an aircraft comprising a localization device and landing on a runway, Figure 2 is a flowchart illustrating an example of the implementation of a method for localizing an aircraft relative to a runway, Figure 3 is a schematic representation in two planes of an architecture of a reflective element, and Figure 4 is a flowchart illustrating an example of the implementation of a method for controlling an aircraft.

[0051] An aircraft 2 and a runway 4 are schematically represented in Figure 1.

[0052] An aircraft is a means of transport capable of rising and moving at altitude within the Earth's atmosphere. For example, an aircraft is a plane, a helicopter, or a drone. More specifically, here, aircraft 2 is a vertical takeoff and landing (VTOL) aircraft attempting to land on runway 3.

[0053] For example, a known vertical landing protocol on such a runway is described in the EASA document (PTS-VPT-DSN, available at the following address "https: / / www.easa.europa.eu / en / document-library / general-publications / prototype-technical-design-specifications-vertiports") and consists of the following sequence of steps: approach of aircraft 2 towards runway 4 with an angle relative to the ground of runway 4 of between 3° and 30°, this angle is commonly called the slope, arrival of aircraft 2 at a decision point LDP (from the English "Landing Decision Point") located at a longitudinal distance from runway 4 usually of between 10 meters and 250 meters, and landing or go-around of aircraft 2 as appropriate.

[0054] Alternatively, runway 4 can also be used for the takeoff of aircraft 2.

[0055] Runway 4 has a shape suitable for a vertical landing.

[0056] For example, runway 4 has a disc shape and is reserved for the takeoff and landing of aircraft.

[0057] In the following description, the location of an object is defined by three coordinates in a given frame of reference.

[0058] Thus, in the remainder of this description, the location of an object relative to track 4 is defined as the projection of three coordinates of said object into a coordinate system of track 4.

[0059] The reference frame of track 4 is the frame formed by three directions orthogonal to each other, the reference frame of track 4 having as its origin the point O with coordinates (0,0,0) in said frame.

[0060] A first direction Y is normal to track 4, a second direction X is transverse to track 4 and a third direction Z is perpendicular to the second direction X.

[0061] In the rest of the description, the origin O of the track 4 reference frame also represents the center of the disk formed by track 4.

[0062] In the example in Figure 1, track 3 has a first group of reflective elements 10 and a second group of reflective elements 12.

[0063] In the example in Figure 1, only two groups of reflective elements 10 and 12 are represented, but this number is not limiting; the number of groups of reflective elements can vary according to the needs, the minimum being one group of reflective elements.

[0064] The first group of reflective elements 10 comprises one or more reflective elements for a radio signal.

[0065] The second group of reflective elements 12 also includes one or more reflective elements for a radio signal.

[0066] For example, the first group of reflective elements 10 includes a first reflective element 20A and a second reflective element 20B.

[0067] In such an example, the second group of reflective elements 12 comprises a first reflective element 22A and a second reflective element 22B.

[0068] Each reflective element 20A, 20B, 22A and 22B is placed on the edge of runway 4. The term "edge of runway" includes the perimeter of runway 4 but also a nearby area which may vary from 10 to 100 meters around said runway 4.

[0069] In the example described, each group of reflective elements 10 and 12 comprises, respectively, two reflective elements 20A, 20B, 22A and 22B, but this number is not limiting, the number of reflective elements can vary according to needs.

[0070] For example, each reflective element 20A, 20B, 22A and 22B is located 25 meters from a point in the main area of ​​runway 4 along the Z direction.

[0071] As an optional addition, the first reflective elements 20A and 22A are respectively spaced at least 3 meters apart from the second reflective elements 20B and 22B.

[0072] Typically, each reflective element 20A, 20B, 22A and 22B has at least two reflectors.

[0073] A reflector is a device that reflects an incident electromagnetic wave, and especially a radar signal.

[0074] For example, each reflector is a trihedral reflector. A trihedral reflector is well suited for radar waves because it has the property of generating radar echoes of relatively high amplitude.

[0075] However, any form of reflector is conceivable here, including parabolic, planar or elliptical reflectors, as well as reflectors using passive, active electronic components, or those with frequency-selective properties.

[0076] For example, such reflectors include Van Atta grating reflectors or Luneberg lenses.

[0077] A plurality of reflectors composing a single reflective element (20A, 20B, 22A, or 22B) allows said reflective element to generate interference specific to the reflectors that compose it upon receiving an incident signal. Thus, for a given incident signal, the reflected signal constitutes a unique signature of the reflective element.

[0078] A longitudinal spacing distance D is defined. esp longfor each reflective element 20A, 20B, 22A and 22B as the distance between the nearest point of a reflective element 20A, 20B, 22A and 22B and a point in the main area of ​​runway 4 along the X direction.

[0079] Typically, the longitudinal spacing distance D esp iong is between 10 meters and 100 meters.

[0080] Advantageously, the longitudinal spacing distance D esp long is equal to 15 meters.

[0081] Aircraft 2 includes a location device 30 configured to transmit a radio signal towards runway 4 and receive a signal reflected by runway 4 (and more specifically from at least one reflective element 20A, 20B, 22A or 22B) in order to deduce a location of aircraft 2 in the reference frame of runway 4.

[0082] The location device 30 includes a radio transceiver 40 and a computer 50.

[0083] The radio transceiver 40 is configured to transmit a radio signal from aircraft 2 to runway 4 and receive a signal reflected by runway 4.

[0084] For example, the radio transceiver 40 is a radar.

[0085] According to a preferred embodiment, the radio transceiver 40 is a continuous wave radar.

[0086] Such a radar is more often referred to as FMCW radar, which refers to the corresponding English term "Frequency Modulated Continuous Wave".

[0087] Such a radar operates here with millimeter or centimeter waves.

[0088] Preferably, the radio transceiver 40 is suitable for transmitting or receiving signals with a frequency selected from the bands: X, K, Ka, Ku and W.

[0089] For such a radar, transmission and reception are almost simultaneous.

[0090] Advantageously, the signals emitted or received by the radio transceiver 40 have a frequency substantially equal to 15GHz, 24 GHz, 77GHz or 95 GHz.

[0091] In the example in Figure 1, the calculator 50 includes, for example, a processor 52 and a memory 54 associated with the processor 52.

[0092] The computer 50 is configured to process signals from the radio transceiver 40.

[0093] Calculator 50 is an electronic circuit designed to manipulate and / or transform data represented by electronic or physical quantities in registers of the calculator and / or memories into other similar data corresponding to physical data in register memories or other types of display devices, transmission devices or storage devices.

[0094] As specific examples, the calculator 50 is implemented as a programmable logic component, such as an FPGA (Field Program Gate Array), or as an integrated circuit, such as an ASIC (Application Specific Integrated Circuit).

[0095] Alternatively, when the process is implemented as one or more software programs, that is, as a computer program, also called a computer program product, it is also capable of being stored on a computer-readable medium, not shown here. A computer-readable medium is, for example, a medium capable of storing electronic instructions and being connected to a bus of a computer system. Examples of such a readable medium include an optical disc, a magneto-optical disc, ROM, RAM, any type of non-volatile memory (e.g., FLASH or NVRAM), or a magnetic card. A computer program containing software instructions is then stored on this readable medium.

[0096] The operation of the localization device 30 is now described with reference to Figure 2, which illustrates an example of the implementation of a localization process.

[0097] The localization process includes an emission step 100, a reception step 200, an extraction step 300, a calculation step 400 and a determination step 500.

[0098] During the first transmission stage 100, the radio transceiver 40 transmits a radio signal from aircraft 2 to runway 4.

[0099] The radio signal thus emitted interacts with the reflective elements 20A, 20B, 22A and 22B, each sending back a reflected signal towards aircraft 2 and more specifically towards the radio transceiver 40.

[0100] During the reception stage 200, the radio transceiver 40 receives a signal reflected by track 3.

[0101] The reflected signal is then one of the signals reflected by the reflective elements 20A, 20B, 22A or 22B or a sum of one or more of said signals.

[0102] Advantageously, in the embodiment in which the radio transceiver 40 is an FMCW radar, the receiving stage 200 is implemented in parallel with the transmitting stage 100.

[0103] During extraction step 300, the computer 40 extracts at least one pattern from the received reflected signal. A pattern is the evolution over time, within a fixed time window, of a radio signal reflected by at least one reflective element.

[0104] Typically, the pattern of the received signal is a waveform of part or all of the received signal, a waveform being a digital vector whose elements are amplitudes of the received signal acquired at different times.

[0105] Furthermore, the reflective element(s) from which at least one pattern originates then form a group of reflective elements called a spotting group in the rest of this description.

[0106] For example, the calculator 40 extracts two patterns from the first reflective element 20A and the second reflective element 20B composing the first group of reflective elements 10 thus forming the identification group.

[0107] Thus, thereafter, the terms "group of reflective elements" and "spotting group" refer to the same group.

[0108] However, the spotting group may change during landing or takeoff depending on the changing distance between aircraft 2 and runway 4 (for example, the group of reflective elements 12 may become the spotting group).

[0109] Each of the patterns is characteristic of the reflective element 20A or 20B and takes, for example, the form of an oscillation of the power received over time when the reflective element 20A or 20B is composed of two identical reflectors positioned side by side.

[0110] For example, the localization device 30 includes a memory capable of storing a plurality of reference patterns corresponding to a reflected radio signal characteristic of a reflective element.

[0111] In particular, the localization device 30 includes a plurality of reference patterns corresponding to specific localization conditions of aircraft 2 relative to the reflective element in the runway 4 reference frame.

[0112] Thus, the calculator 50 can recognize a pattern in a received signal by comparing it to the plurality of reference patterns.

[0113] During calculation step 400, calculator 50 obtains a vertical distance D y .

[0114] The vertical distance D y is defined as the distance between aircraft 2 and runway 4 along the first direction Y. Generally, the vertical distance D ycorresponds to the height of aircraft 2 relative to runway 4.

[0115] Calculator 50 calculates the vertical distance D y based on at least one extracted pattern. Calculation step 400 includes an estimation substep 410 and a calculation substep 420.

[0116] During estimation substep 410, calculator 34 estimates a phase shift between a first reflected pattern and a second reflected pattern.

[0117] Typically, the first reflected pattern corresponds to the signal reflected by the first reflective element 20A and the second reflected pattern corresponds to the signal reflected by the second reflective element 20B.

[0118] As a reminder, reflective elements 20A and 20B form the identification group.

[0119] For example, calculator 50 looks for a sequence of the first reflected pattern in the second reflected pattern, with the first reflected pattern being extracted before the second reflected pattern.

[0120] During calculation substep 420, calculator 50 calculates the vertical distance D y by applying a function f to the estimated phase shift.

[0121] The function f is a function associating a vertical distance D y to a phase shift between two reflected patterns.

[0122] For example, the associated distance values ​​are contained in a table stored by a memory contained in the location device 30.

[0123] During the determination step 500, the calculator 50 determines the location y A of aircraft 2 as a function of the vertical distance D y .

[0124] To do this, calculator 50 determines the location y Aof aircraft 2 in the runway 4 marker.

[0125] Calculator 50 obtains the location y A like the difference between the vertical distance D y and a distance y 10 between the spotting group and the center O of runway 4 along the first direction Y.

[0126] For example, the distance y 10 is equal to the distance between the first reflective element 20A and the center O of track 4.

[0127] Alternatively, the distance y 10 is equal to the distance between the second reflective element 20B and the center O of track 4.

[0128] As a further variation, the distance y 10 is equal to the distance between an average of the locations of the reflective elements 20A, 20B in the reference frame of track 4 and the center O of track 4.

[0129] The calculation of y A mathematically, it can be written as follows:

[0130] VA = D y - y10

[0131] Typically, the calculator 50 considers the height of the tracking group in the track 4 coordinate system to be zero, which simplifies the calculation of y A Xi ~ D y

[0132] Thus, the described process makes it possible to obtain the location of aircraft 2 in relation to runway 4.

[0133] Advantageously, the localization process described is simple to implement and involves few constraints for runway 4 because only the characteristics of the reflectors composing the reflective elements 20A, 20B, 22A and 22B need to be determined.

[0134] Figure 3 represents an embodiment in which the reflective element 20A comprises at least two trihedral reflectors 60A and 60B and their characteristics to be determined: a: length of the sides of the reflectors,

[0135] E x : longitudinal difference between reflectors 60A and 60B along the X, E direction y: vertical gap E y between reflectors 60A and 60B along the Y and E directions z : lateral deviation E z between reflectors 60A and 60B along the Z direction.

[0136] First, to determine the lengths of the sides of reflectors 60A and 60B, it is possible to use the radar cross-sectional area (RCS).

[0137] The SER is an inherent physical property of objects indicating the relative importance of the reflecting surface of an electromagnetic beam they produce.

[0138] For a given reflector, its RCS is defined by the following equation:

[0139] Where: a denotes the length of the sides of the reflector,

[0140] - A denotes the wavelength of the signal emitted by the radar.

[0141] Thus, for a pair of reflectors 60A and 60B, the amplitude of the oscillation of the signal reflected by the reflecting element 20A depends on the RCF of each of the reflectors 60A and 60B.

[0142] Therefore, the sum of the SER of the two reflectors 60A and 60B must satisfy the following two equations:

[0143] SER + SER2 = 10\SER1- SER2\

[0144] Or :

[0145] SER refers to the SER of the first 60A reflector,

[0146] SER2 denotes the SER of the second reflector 60B, radarmin amp max dist denotes the minimum detectable SER by the radio transceiver 40 at the greatest envisaged operating distance (for example, 1 kilometer).

[0147] By choosing a side length a that allows these two equations to be satisfied, the signal reflected by the reflecting element 20A remains detectable.

[0148] Furthermore, the total SER showing a 10dB difference between its minimum and maximum values ​​allows for a sufficient measurement range to be maintained.

[0149] Typically, a 60A reflector with 360 millimeter sides and a 6B reflector with 380 millimeter sides may be suitable.

[0150] The longitudinal gap E x must be less than 3 meters for the radial resolution of the radio transceiver 40 to allow the interference to be observed.

[0151] Indeed, the radial resolution of such a radio transceiver 40 is on the order of 3 meters and a longitudinal deviation E x greater than 3 meters would imply that the location device 30 would receive a reflected signal for each reflector and not for each reflective element 20A, 20B, 22A and 22B.

[0152] Furthermore, the angular resolution of such a radio transceiver 40 is on the order of 2° and explains the lateral spacing distance D esp lat greater than 3 meters without which two signals from two reflective elements could be confused.

[0153] Next, the lateral gap E z allows increasing sensitivity for a lateral location of aircraft 2 relative to runway 4, said lateral location will be described later.

[0154] Finally, the vertical gap E y allows easy observation of the oscillations of the reflected signal while remaining sensitive to vertical shifts.

[0155] However, for distances between aircraft 2 and runway 4 of less than 350 meters, the oscillations are more observable for reflectors offset by a vertical gap E y of the order of 15 centimeters while a vertical gap E yA gap of around 1 meter is preferable for distances greater than 350 meters.

[0156] Thus, for example, the first group of reflective elements 10 has reflectors offset by a vertical gap E y approximately equal to 15 centimeters.

[0157] In this example, the second group of reflective elements 12 has reflectors offset by a vertical gap E v approximately equal to 1 meter.

[0158] As explained previously, the spotting group can change depending on the distance between aircraft 2 and the center O of runway 4. Thus, for example, the first group of reflective elements 10 can serve as the spotting group up to a distance of 350 meters between aircraft 2 and the center O of runway 4 along the X direction. In such an example, the second group of reflective elements 12 will then be the spotting group if the distance between aircraft 2 and the center O of runway 4 along the X direction is less than 350 meters.

[0159] Such dimensions are easily achievable in practice.

[0160] Modifying an existing runway thus represents a moderate cost for an airport wishing to equip itself with it and is easy to implement.

[0161] Similarly, the installation cost of the 30 location device is also moderate and the modifications required are minor, most often amounting to a simple reprogramming of an existing computer.

[0162] In addition, the process has a hybrid character since it allows for precise localization of aircraft 2 during landing and takeoff phases.

[0163] Other ways of implementing the process just described are conceivable.

[0164] For example, the steps can be implemented in a different order or in parallel when technically possible.

[0165] According to another example, calculation step 400 is performed differently.

[0166] In such an example, calculation step 400 includes an estimation substep and a calculation substep.

[0167] During the first estimation substep, the calculator 50 estimates an oscillation frequency of at least one extracted pattern.

[0168] If several patterns have been extracted, calculator 50 estimates that the oscillation frequency is an average or a weighted average of all the oscillation frequencies of the different patterns.

[0169] During the calculation substep, calculator 50 calculates the vertical distance D y by applying a function h to the oscillation frequency.

[0170] The function h is a function associating a vertical distance D y at an oscillation frequency.

[0171] For example, the associated distance values ​​are contained in a table stored by a memory contained in the location device 30.

[0172] In yet another example, calculation step 400 is performed in a different way.

[0173] In such an example, calculation step 400 includes a determination substep and a calculation substep.

[0174] During the determination substep, the calculator 50 determines a sub-motif extracted from one of the reflected patterns for which the correlation with a theoretical pattern is maximal. During the calculation substep, the calculator 50 calculates the vertical distance D y by applying a function w to the sub-motif extracted from one of the reflected motifs.

[0175] The function w is a function associating a vertical distance D y to an extracted sub-motif.

[0176] The localization process may also include additional steps.

[0177] For example, the localization process also includes a step of determining a lateral distance D z and a longitudinal distance D x of aircraft 2 in relation to runway 4.

[0178] During the determination stage, the calculator 50 estimates two distances: a first distance d between aircraft 2 and the first reflective element 20A and a second distance d2 between aircraft 2 and the second reflective element 22B.

[0179] The distances d and d2 are determined by the FMCW radar, from the received radio signal and using classical radar range measurement algorithms.

[0180] Thus, during the determination step 500, the calculator 50 calculates the longitudinal distance D x and the lateral distance D z of aircraft 2.

[0181] For example, the lateral distance D z and the longitudinal distance D x are calculated by multilateration from the distances d1 and d2 and the vertical distance D y , the longitudinal distance D zbeing the distance between aircraft 2 and the center O of runway 4 along a third direction Z perpendicular to the second direction (X) and the longitudinal distance D x being the distance between aircraft 2 and the center O of runway 4 along the second direction X.

[0182] In this example, the location (x A ,y A ,z A ) of aircraft 2 is the location (D x ,D y ,D z ).

[0183] The localization process can also be used in other processes, including a control process.

[0184] In such a case, aircraft 2 is equipped with additional elements. For example, aircraft 2 also includes a control device comprising the location device 30 of Figure 1 and a controller.

[0185] The controller is configured to process signals from the location device 30.

[0186] From a hardware perspective, the controller is similar to the calculator 50 of the locating device 30, so the remarks made for calculator 50 also apply here.

[0187] Thus, in particular, as with calculator 50, the controller comprises a processor and memory associated with the processor. The control device is configured to implement a control method now described with reference to Figure 4.

[0188] The control procedure aims to control aircraft 2, that is to say, to ensure its proper progress during a landing or takeoff phase.

[0189] The control procedure includes a step of locating the aircraft relative to the runway during which the steps of the localization procedure in Figure 2 are implemented.

[0190] The process also includes an estimation step 600 of a percentage risk of the presence of an obstacle on the track and an alert step 700.

[0191] During the estimation step 600 of a percentage risk of presence of an obstacle on the runway, a ground pattern is received by the radio transceiver 40, the ground pattern being the radio signal reflected by the ground of runway 4.

[0192] For example, the received floor pattern is compared to a reference floor pattern stored in memory and the percentage of risk is determined based on the differences in amplitude and / or shape of the two patterns.

[0193] During alert stage 700, the control device issues an alert to an operator based on the estimated percentage and location of aircraft 2 relative to runway 4.

[0194] Typically, for the same ground pattern received, the percentage of risk will be higher if the location of aircraft 2 is close to runway 4.

[0195] For example, the alert takes the form of a notification on a screen for the operator. The operator here is a pilot, a co-pilot or a member of the flight crew.

[0196] In another example, the operator is the air traffic control (ATC) service and can authorize or prohibit takeoff or landing depending on the alert received.

[0197] In another example, the system automatically interrupts the landing or takeoff when the percentage of risk exceeds a certain threshold.

[0198] The control process thus makes it possible to guarantee the safety of the aircraft in the conditions of landing and takeoff while preventing the risks of collision with possible obstacles on runway 4.

[0199] The control process remains easy to implement.

Claims

DEMANDS 1. A method for locating an aircraft (2) relative to a runway (4) on which aircraft (2) can land or take off, the runway (4) having a shape suitable for vertical landing and comprising at least one reflective element (20A, 20B, 22A, 22B) for a radio signal, the method comprising the following steps: - transmission (100) of a radio signal from the aircraft (2) towards the runway (4), - reception (200) of a signal reflected by track (4) in response to the emitted radio signal, - extraction (300) of at least one pattern in the received reflected signal, each pattern being the evolution over time of the radio signal reflected by at least one reflective element (20A, 20B, 22A, 22B) composing a group of reflective elements, called the tracking group (10), - calculation (400) of a vertical distance (D y) from at least one pattern, the vertical distance (D y ) being the distance between the aircraft (2) and a center (O) of the runway (4) along a first direction (Y) normal to the runway (4), and - determination (500) of a vertical location y A ) of the aircraft (2) relative to the runway (4) as a function of the vertical distance (D y ).

2. A localization method according to claim 1, wherein the calculation step (400) of the vertical distance (D y ) includes the following sub-steps: - estimation of a phase shift between two patterns, and - calculation of the vertical distance (D y ) by applying a function to the estimated phase shift, the function associating a vertical distance (D y ) to a phase shift between two patterns.

3. A localization method according to claim 1, wherein the calculation step (400) of the vertical distance (D y) includes the following sub-steps: - estimation of the frequency of at least one pattern, and - calculation of the vertical distance (D y ) by applying a function to the estimated frequency, the function associating a vertical distance (D y ) depending on the estimated frequency.

4. A localization method according to any one of claims 1 to 3, wherein each reflective element (20A, 20B, 22A, 22B) comprises at least two reflectors (60A, 60B), the at least two reflectors (60A, 60B) being aligned or offset from each other along a second direction (X) transverse to the track (4) and along the first direction (Y).

5. A localization method according to any one of claims 1 to 4, the method further comprising the following steps: - estimation of two distances: a first distance (d1) between the aircraft (2) and a first reflective element (20A, 20B, 22A, 22B) and a second distance (d2) between the aircraft (2) and a second reflective element (20A, 20B, 22A, 22B) - calculation by multilateration of a lateral distance (Z) z ) and a longitudinal distance (Z) x ) from the first distance (d1), the second distance (d2) and the vertical distance (D y ), the lateral distance (Z) z ) being the distance between the aircraft (2) and the center (O) of the runway (4) along a third direction (Z) perpendicular to the second direction (X), and the longitudinal distance (Z) x ) being the distance between the aircraft (2) and the center (O) of the runway (4) along the second direction (X), - determination of a location (x A ,y A ,z A ) of the aircraft (2) as a function of the vertical distance (D y), of the longitudinal distance (Z) x ) and the lateral distance (^z).

6. Localization method according to any one of claims 1 to 5, wherein the radio signal belongs to a frequency band selected from the X, K, Ka, Ku and W bands.

7. Aircraft control procedure (2), the control procedure comprising the following steps: - localization of the aircraft by implementing a localization method according to any one of claims 1 to 6, - estimation (600) of a percentage risk of the presence of an obstacle on the runway (4) based on a ground pattern, the ground pattern being the radio signal reflected by the runway ground (4), and - implementation (700) of an action to interrupt the landing or takeoff of the aircraft (2) according to the determined location and the estimated percentage of risk.

8. Electronic device for locating an aircraft (2) relative to a runway (4) on which aircraft (2) can land or take off, the runway (4) having 18. A shape adapted for vertical landing and comprising at least one reflective element (20A, 20B, 22A, 22B) for a radio signal, the location device (30) being configured to: transmit a radio signal from the aircraft (2) to the runway (4), receive a signal reflected by the runway (4) in response to the transmitted radio signal, extract at least one pattern from the received reflected signal, each pattern being the evolution over time of the radio signal reflected by at least one reflective element (20A, 20B, 22A, 22B) forming a group of reflective elements, called the tracking group (10), calculate a vertical distance (D y ) from at least one pattern, the vertical distance (D y) being the distance between the aircraft (2) and a center (O) of the runway (4) along a first direction (Y) normal to the runway (4), and determine a vertical location (y A ) of the aircraft (2) relative to the runway (4) as a function of the vertical distance (D y ).

9. A control device for an aircraft (2), relative to a runway (4) on which aircraft (2) can land or take off, the runway and comprising at least one reflective element (20A, 20B, 22A, 22B) for a radio signal, said device comprising: an aircraft location device (30) according to claim 8, and a controller configured to: o estimate a percentage risk of the presence of an obstacle on the runway (4) from a ground pattern, the ground pattern being the radio signal reflected by the ground of the runway (4); and o perform an automatic interruption action of the landing or takeoff of the aircraft (2) according to the location determined by the location device (30) and the estimated percentage risk.

10. Runway (4) on which aircraft (2) can land or take off, the runway (4) having a shape suitable for vertical landing and comprising two groups of reflective elements (10, 12) for a radio signal arranged on one edge of the runway (4).

11. Track (4) according to claim 10, wherein a reflective element (20A, 20B, 22A, 22B) comprises at least two trihedral reflectors (60A, 60B). 19 12. Track (4) according to claim 11, wherein the at least two trihedral reflectors (60A, 60B) of one of the two groups of reflective elements (10, 12) are offset from each other along a first direction (Y) normal to the track (4) and along a second direction (X) transverse to the track (4).

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