DEVICE AND METHOD FOR AIDING AIRCRAFT CONTROL

Description

Domaine de l'invention

[0001] The invention relates to the field of flight management systems, and more particularly to that of assisting in guiding aircraft along a predefined trajectory. Etat de la Technique

[0002] One of the functions of a Flight Management System (FMS) is to calculate a trajectory (lateral and vertical) in order to guide an aircraft on it during a flight. As far as possible, the trajectory, and in particular the lateral trajectory, is calculated to be consistent with the technical capabilities that the aircraft can follow. Among the technical capabilities of an aircraft, there is a maximum roll criterion that it must be able to respect.

[0003] Also, an aircraft guidance system on a trajectory consists in particular of guiding it on a lateral axis by controlling its roll to control it on this trajectory, while respecting a threshold roll value ("maximum roll") which is predefined for the type of aircraft concerned. Indeed, either for reasons related to flight mechanics, or to guarantee the safety or comfort of passengers, an aircraft cannot exceed a given maximum roll.

[0004] In onboard systems such as FMS, the trajectory that is calculated must allow the aircraft to fly this trajectory while respecting the maximum roll criterion. This type of calculator makes it possible to predict the speed of the aircraft at the different waypoints (WPT) of a turn and adjust the turn radii as needed. figure 1 illustrates a trajectory to be flown for an aircraft on a curved segment, where the radius of the turn is calculated according to the following equation (1): Rayon = V 2 g . tan Roulis with V the predicted speed.

[0005] In order to avoid turns with too little roll and the associated operational disadvantages such as increased distance and therefore flight time, the trajectory is calculated with a target roll that is close to the maximum roll. Generally, a slight margin (nominally 5°) is nevertheless taken into account in the construction of the trajectory to absorb guidance corrections during the flight of the curved segment.

[0006] However, in certain situations, the maximum roll criterion cannot be respected and the aircraft then finds itself deviating from the calculated trajectory.

[0007] A first case where the maximum roll may not be respected is along a curved trajectory segment where the aircraft speed is not always constant. A solution to avoid exceeding the maximum roll consists of predicting the aircraft acceleration and taking it into account in the calculation of the turn radius, in order to guarantee a maximum roll value. However, this calculation can be erroneous due to poor consideration of the real wind and / or poor modeling of aircraft performance, for example, resulting in a radius calculation that cannot be followed by the aircraft.

[0008] A second real case where the maximum roll is not respected can occur during the acceleration of an aircraft in a turn. Indeed, a major disadvantage of calculating a turn ensuring not to exceed a maximum roll value is to construct large turns which are not always compatible for their practical implementation by aircraft. Such large turns can lead to a small roll at the beginning of the turn, an extension of the flight distance, but also to overflight of prohibited areas such as inhabited areas. One effect of these consequences is that, voluntarily due to these operational constraints, the radius of the turn is sometimes underestimated in the calculation, and the aircraft is then slaved on this trajectory until reaching the maximum roll, then it deviates from the trajectory.

[0009] A third other case presenting the risk of non-compliance with a maximum roll is linked to the fact that a trajectory which is calculated is also constructed in coherence with the expectations of the charts, that is to say with a theoretical speed imposed by the procedures, independently of the real speed. The calculated trajectory thus becomes the reference, and consequently the radius of a turn can sometimes be underestimated in view of the effective speed, and the aircraft is then controlled on this trajectory until reaching the maximum roll, then it deviates from the trajectory.

[0010] When an aircraft has deviated from a trajectory, known solutions are based on a system that alerts once the aircraft is deviating from this trajectory. The alert can be made to the crew by displaying the value of the lateral deviation between the aircraft and this trajectory (also known in English as "crosstrack error" or XTK), or by updating the trajectory in real time during the flight of the turn to indicate the actual trajectory of the aircraft, or by displaying the flight trajectory based on the current roll. The crew must then manage the situation at the time and during the problem, either by letting the aircraft drift off the trajectory if the situation allows it, or by applying corrections such as reducing speed or manually taking control of the aircraft.

[0011] The disadvantage of these solutions, and more generally of solutions based on alerts triggered after the fact, is that these alerts are too late in relation to the occurrence of a problematic situation, because these systems provide information once an error has been detected.

[0012] Known warning systems do not allow a situation to be anticipated and a crew to be warned in advance so that they can take corrective action in advance, such as reducing the aircraft's speed, to avoid a future error.

[0013] One aim of the invention is to overcome the drawbacks of known alert solutions, and to propose a predictive trajectory tracking alert device.

[0014] An overview of techniques in this field can be found in "The avionics handbook" edited by Cary R. Spitzer. Résumé de l'invention

[0015] An object of the present invention is to propose a method making it possible to predict an actual trajectory of an aircraft and to be able to warn a crew or a guidance system in advance of the impossibility of flying a reference trajectory under normal conditions.

[0016] Another object of the invention is to provide a device which comprises means for implementing the claimed method.

[0017] Advantageously, the device and method of the invention make it possible to provide information to a crew or to a guidance system at a time prior to the occurrence of a problematic situation, in particular one where an aircraft is going to deviate from a predefined trajectory.

[0018] To obtain the desired results, methods, devices and computer program products are described.

[0019] In general, the invention consists of calculating for an upcoming change of direction of an aircraft (i.e. a turn), a predicted real trajectory, and which, depending on whether or not it conforms to a reference trajectory, will make it possible to trigger an alert to a crew and / or to a guidance system.

[0020] In particular, an aircraft guidance assistance method, operated by an aircraft computing platform, comprises at least: a step of acquiring state variables characterizing an aircraft in flight, environmental variables characterizing the environment of the aircraft and trajectory variables characterizing a reference trajectory of the aircraft, a step of calculating a predicted actual trajectory for a next change of direction of the aircraft, from said state variables, said environmental variables and said reference trajectory variables, a step of determining conformity to determine whether the predicted actual trajectory that is calculated is consistent or not with the reference trajectory; and a step of configuring a trajectory deviation alert, when the predicted actual trajectory is not consistent with the reference trajectory.

[0021] According to alternative embodiments, the calculation of the predicted actual trajectory can be done according to two distinct variants. In a first implementation, the method will make it possible to predict the actual roll of the aircraft for the next turn. In another implementation of the method, it is a calculation of the prediction of the actual position of the aircraft for the next turn.

[0022] According to alternative or combined embodiments: the step of calculating the predicted actual trajectory consists of calculating prediction variables characterizing the prediction of a roll of the aircraft and / or the prediction of a position of the aircraft, for a next change of direction of the aircraft; the step of determining conformity consists of comparing the values ​​of said prediction variables with predefined threshold values ​​for the reference trajectory of the aircraft; the step of determining conformity consists of verifying whether the predicted roll value is greater than a predefined maximum roll value and / or verifying whether the predicted position of the aircraft corresponds to a lateral deviation value greater than a predefined maximum lateral deviation value;the step of calculating the predicted actual trajectory comprises an initial step of determining the position of the aircraft relative to a next change of direction, making it possible to determine whether the aircraft is located before the next change of direction or whether the aircraft is already engaged in the turn corresponding to the change of direction; the step of calculating the predicted actual trajectory consists of implementing a simulation function to predict a real trajectory of the aircraft, either from the start of the turn for the turn to be flown, or from the current position of the aircraft in the turn for the remaining segment of the turn to be flown.;

[0023] The invention also relates to a device for assisting aircraft guidance which comprises means for: acquiring state variables characterizing an aircraft in flight, environmental variables characterizing the environment of the aircraft and trajectory variables characterizing a reference trajectory of the aircraft, calculating a predicted actual trajectory of the aircraft for a next change of direction of the aircraft, from said state variables, said environmental variables and said reference trajectory variables, determining whether the calculated predicted actual trajectory is consistent or not with the reference trajectory; and configuring a trajectory deviation alert, when the predicted actual trajectory is not consistent with the reference trajectory.

[0024] The device further comprises means configured to operate the steps of the claimed method.

[0025] The invention also covers a flight management system (FMS) or an on-board computing system of the EFB type which comprises an aircraft guidance assistance device as claimed.

[0026] The invention also relates to a computer program product which comprises code instructions for carrying out the steps of the claimed method, when the program is executed on a computer. Description des figures

[0027] Various aspects and advantages of the invention will appear in support of the description of a preferred but non-limiting mode of implementation of the invention, with reference to the figures below: There figure 1 illustrates a trajectory to be flown for an aircraft on a curved segment; The figure 2 illustrates the general steps of the method of the invention in one embodiment; The figures 3a et 3b illustrate two variants of displaying a predicted real trajectory for a curved segment according to the calculation of a predicted real roll; The figures 4a et 4b illustrate two variants of displaying a predicted real trajectory for a curved segment according to the calculation of a predicted real position; The figure 5 illustrates the steps of an alternative embodiment of the method of the invention; The figure 6 and the figure 7 are representations of the parameters used for the real roll prediction calculation; The figure 8 and the figure 9 are representations of the parameters used for the actual position prediction calculation; and The figure 10 illustrates a structure of a flight management system (FMS) for implementing the device and method of the invention. Description détaillée de l'invention

[0028] When an aircraft travels between two airports, a flight plan (FPLN) is filed to inform the air navigation services. This contains all the specified information about the planned flight or part of the flight, including: the type of aircraft; the departure time; the first flight level requested for the cruise; the on-board equipment; the planned route.

[0029] The flight plan between a starting point and a destination point contains a set of waypoints (WPTs) ordered in a predetermined manner, where at each waypoint, a change of heading or altitude or speed must take place. A waypoint is defined by a geographical position, latitude and longitude coordinates. All these points can be chosen from predefined points in a navigation database, and can correspond to airports, radio navigation beacons, etc.

[0030] To follow its flight plan, an aircraft uses a Flight Management System (FMS). The FMS is an onboard navigation aid system that integrates information about the aircraft's performance and position, from navigation sensors, the stored flight plan, and manual input. Its purpose is to assist pilots by providing piloting instructions via a suitable human-machine interface, or to enable automatic guidance of the aircraft along the trajectory when coupled with the autopilot. In order to guide the aircraft to follow its flight plan, the FMS uses various sensors to determine the aircraft's current position (PPOS) and the accuracy of this position. Accuracy is defined as the degree of conformity between the estimated, measured, or desired position and the actual position of the aircraft at a given time.The FMS also allows the pilot to modify the flight plan during the flight for various reasons such as a delay caused by adverse weather conditions to be avoided, or by requests imposed by air traffic control (ATM). On a regular basis, from the points in the flight plan, the FMS calculates a lateral trajectory. From the cruising level and altitude constraints, the FMS also calculates a vertical profile. From the speed constraints and optimized speeds for each flight phase and based on a cost index chosen by the airline, the FMS calculates a speed profile. Taking into account the flight plan and the aircraft's position, the FMS calculates the reference trajectory to follow, which is a succession of straight and curved segments. The points connecting the segments of the reference trajectory may correspond to waypoints in the flight plan or be different.

[0031] There figure 10 illustrates a structure of a flight management system for implementing the method of the invention. For example, the system may be a flight management system of the FMS type (1000), comprising the components adapted to carry out the known functionalities and further integrating an alert calculation module (1040) configured to implement the method of the invention.

[0032] A known FMS type system has a human-machine interface (1020) comprising for example a keyboard and a display screen, or simply a touch display screen, as well as modules making it possible to perform at least the following functions: Navigation (LOCNAV) (1001), to perform the optimal location of the aircraft based on geolocation means (1030) such as satellite geopositioning or GPS, GALILEO, VHF radio navigation beacons, inertial units. This module communicates with the geolocation devices; Flight Plan (FPLN) (1002), to enter the geographical elements constituting the skeleton of the route to be followed, such as the points imposed by the departure and arrival procedures, the waypoints, the air routes or "airways" according to the Anglo-Saxon term; Navigation Database (NAVDB) (1003), to construct geographical routes and procedures from data included in the databases relating to points, beacons, interception or altitude legs...; Performance Database, (PERFDB) (1004), containing aerodynamic and engine performance parameters of the aircraft; Trajectory (TRAJ) (1005), to construct an optimized and continuous 4D trajectory, from the points of the flight plan and the associated constraints, respecting the aircraft performance and the confinement constraints (RNP); Predictions (PRED) (1006), to provide predictions (Altitude, time, fuel) on all points of the flight plan; Guidance (GUID) (1007), to provide commands to guide the aircraft along the lateral plane, the vertical profile and the speed profile; Digital Data Link (DATALINK) (1008) to communicate with control centers and other aircraft (1009).

[0033] According to one embodiment, the claimed method is carried by a specific partition of a hardware platform specific to avionics but different from that of the FMS, such as for example an “Electronic Flight Bag” (EFB) type device. According to another preferred embodiment, this calculation is carried out on the execution platform of the FMS, by components (1040) adapted to the calculations. Indeed, the advent of integrated modular avionics on recent aircraft has enabled the definition of execution platforms and digital communication between the functions. This development has, however, led to an increase in complexity - in particular the internal complexity of the functions but also the complexity of the configuration process of the avionics system - and growing performance and resource optimization needs.In this context, new hardware platforms are equipped with management capabilities (operations, security and maintenance), energy optimization and localization, which go beyond the standard functions of known platforms.

[0034] According to another aspect, the invention relates to a computer program product comprising code instructions for carrying out the steps of the method according to the invention. The method can be implemented from hardware and / or software elements. The method can be available as a computer program product on a computer-readable medium. The method can be implemented on a system which can use one or more dedicated electronic circuits or a general-purpose circuit. The technique of the method according to the invention can be carried out on a reprogrammable computing machine (a processor or a microcontroller for example) executing a program comprising a sequence of non-transitory instructions, or on a dedicated computing machine (for example a set of logic gates such as an FPGA or an ASIC, or any other hardware module).The various modules of the system according to the invention may be implemented on a single processor or circuit, or distributed across multiple processors or circuits. The modules of the system according to the invention consist of computing means including a processor. Reference to a computer program that, when executed, performs any of the functions described above, is not limited to an application program running on a single host computer. Rather, the terms computer program and software are used herein in a general sense to refer to any type of computer code (e.g., application software, firmware, microcode, or any other form of computer instruction) that can be used to program one or more processors to implement aspects of the techniques described herein.

[0035] There figure 2 illustrates the general steps of the method of the invention in one embodiment. Generally, the method consists of performing a real trajectory prediction calculation (called “predicted real trajectory”) for an upcoming change of direction of an aircraft, then generating an alert if the predicted real trajectory does not respect a reference trajectory or predefined trajectory.

[0036] The method 200 begins with a step 202 of acquiring several types of variables relating to an aircraft, and in particular: state variables including at least: the current situation of the aircraft such as its position, roll, speed, altitude. environmental variables including at least: the current or forecast weather around the aircraft. reference trajectory variables including at least: the curved segment allowing the next change of direction to be made, the maximum roll of the aircraft and, if necessary, the planned vertical evolutions in terms of speed or altitude.

[0037] In a following step 204, the method makes it possible to use the current values ​​of the different variables to make a prediction calculation of the actual trajectory of the aircraft for a next change of direction of the aircraft. In the context of the invention, a change of direction corresponds to a turn or curved segment characterized by different parameters, in particular: a start of a turn; an end of a turn; a radius R of the turn.

[0038] The calculation of the predicted actual trajectory is done for a curved segment defined by start, end and radius parameters of the turn. In one embodiment, the step of calculating the predicted actual trajectory consists of calculating prediction variables characterizing the prediction of an actual roll of the aircraft along the curved segment. In another embodiment, the step of calculating the predicted actual trajectory consists of calculating prediction variables characterizing the prediction of an actual position of the aircraft during the turn.

[0039] In a following step 206, the method makes it possible to determine the conformity of the predicted actual trajectory to the reference trajectory of the aircraft for the turn concerned. The conformity determination step may consist of comparing the values ​​of the actual roll prediction variables or comparing the values ​​of the actual position prediction variables of the aircraft to predefined threshold values ​​for the reference trajectory of the aircraft.

[0040] In one embodiment, the comparison comprises checking whether the predicted actual roll value is greater than a predefined maximum roll value. In another embodiment, the comparison comprises checking whether the lateral deviation of the predicted actual position of the aircraft is greater than a predefined maximum lateral deviation value.

[0041] After the compliance determination step, the method makes it possible to configure a trajectory deviation alert (step 208) according to the result of the previous step.

[0042] In an embodiment of predicting the actual roll of the aircraft, the method makes it possible to generate information alerting the crew and / or information communicated to an onboard system, if the predicted actual roll of the aircraft exceeds the maximum roll predicted (considering a margin if necessary), reflecting a trajectory non-conformity. In one embodiment, an alert may consist of a modification of the display of the trajectory on a screen of the aircraft, for example by modifying the color of the portion of the trajectory displayed in the event of prediction of exceeding the maximum roll. Thus, in an embodiment illustrated in the figure 3a , the actual predicted trajectory for the next curved segment can be displayed to the crew in a specific color (e.g. amber) dedicated to trajectory deviation alert, and different from the current color (e.g. green), if the actual predicted roll exceeds a predefined threshold for the next turn. In another embodiment illustrated in the figure 3b , the actual trajectory predicted for the next curved segment can be displayed to the crew with a specific color dedicated to the trajectory deviation alert, and different from the current color (for example green), and whose intensity varies along the curved segment according to the actual roll value predicted with respect to the predefined maximum roll.

[0043] In an embodiment of prediction of the actual position of the aircraft, the method makes it possible to generate information alerting the crew and / or information communicated to an on-board system, as to the actual predicted trajectory of the aircraft, i.e. the trajectory that the aircraft will actually fly, and therefore inform the crew about the lateral deviation that the aircraft will have in relation to the predefined trajectory. In an embodiment illustrated in the figure 4a , the actual trajectory predicted for a next curved segment according to the calculation of a predicted actual position, can be displayed in a different color (for example white) superimposed on the predefined trajectory (displayed for example in green). In another embodiment illustrated in the figure 4b , a display of the predicted actual trajectory can be made in relation to a corridor to be respected around the predefined trajectory (known in RNP procedures as “Required Navigation Performance”), and reflect along the curved segment the maximum lateral deviation observed (XTK max) between the predicted actual trajectory and the predefined trajectory.

[0044] In other alternative embodiments or combined with the previous described embodiments, the configuration of an alert may consist of generating one or more alert messages (visual, audio). Those skilled in the art will be able to implement other forms of alert adapted to the context of application of the invention.

[0045] There figure 5 illustrates steps of an alternative embodiment of the method of the invention. In a first step 502, the method 500 of the figure 5 allows to determine where the aircraft is in relation to an upcoming change of direction in the flight plan, i.e. either the aircraft is located before the turn, or the aircraft is already engaged in the turn.

[0046] If the aircraft is located upstream of the turn, the method in a following step 504, makes it possible to acquire in addition to all the general state, environment and reference trajectory variables (step 202 of the figure 2 ), starting parameters defining: a turn as a curved segment of radius R, with a starting point P 0 characterized by its latitude and longitude, and a starting course crs 0 of this curved segment; a starting speed TAS 0 of the aircraft at the start of the turn. In one embodiment, the starting speed is based on a predicted speed profile. Indeed, the trajectory calculation systems of the FMS make it possible to know speed predictions along the trajectories. Also, the starting speed parameter TAS 0 of the aircraft at the start of the turn can be derived from the FMS data as a prediction of true airspeed (TAS for "True Air Speed") of the aircraft along this curved segment.In other embodiments, the departure speed parameter is obtained by data on the calibrated airspeed prediction (CAS for "Calibrated Air Speed" and the altitude; a departure roll Φ 0 of the aircraft, equal to the roll of the aircraft at the position at the departure point P 0 , and which can be defined by the following equation: Φ 0 = Atan(TAS 0 2 < / gR) if an anticipation of the turn is considered. In one embodiment, another departure roll value can be taken into account depending on the type of guidance used. For example, a zero departure roll value can be used if no anticipation of the turn is considered; a predicted wind in the turn, characterized by two values: Wind crs for the course from which the wind comes, and Wind mag for the magnitude or speed of the wind.

[0047] If the aircraft is already flying the turn, the method in a following step 506, allows, in addition to the set of general state, environment and reference trajectory variables (step 202 of the figure 2 ), and starting parameters (step 504), to acquire current parameters for the aircraft, defining: the current position of the aircraft P i ; the current speed of the aircraft TAS i ; and the current roll of the aircraft Φ i .

[0048] In a following step 508, the method makes it possible to implement a simulation function, to predict a real trajectory of the aircraft, either from the start of the turn for the curved segment to be flown, or from the current position of the aircraft in the turn for the curved segment remaining to be flown. The prediction calculation can, depending on the embodiments, be done either by a prediction of the real roll of the aircraft, or by a prediction of the real position of the aircraft.

[0049] In the actual roll prediction embodiment, a simulation module is configured to calculate the predicted actual roll of the aircraft, from the following equations: CRS n = CRS 0 + n × dx R for rightward curved segments, or CRS n = CRS 0 − n × dx R for curved segments to the left, with dx a parameter that defines the step value allowing the discretization of the calculation; and V n = TAS n + Vent mag × cos Vent crs + 180 ° − Crs n .

[0050] The predicted actual roll is then obtained by the following equation: Φ n = tan − 1 V n 2 g . R where 'g' is the gravitational constant.

[0051] There figure 6 and the figure 7 are representations of the parameters used for the actual roll prediction calculation. The simulation module allows to calculate the actual roll predicted for 'n' positions X n of the aircraft along the curved segment, between a start position (X 0 or X i ) and an end position X end (iteration of step 510).

[0052] The simulation module is further configured to check the prediction value obtained at each position (step 206 of the figure 2 ), and to generate, if necessary, a trajectory deviation alert (step 512) according to a predefined alert configuration.

[0053] Thus, in the embodiment applied to the prediction of the actual roll of the aircraft, if for at least one of the 'n' positions, the predicted actual roll is greater in absolute value than the predefined maximum roll, which can be fixed in advance or defined as the trajectory roll plus a predefined margin, then the curved segment is considered unflyable and an alert can be raised ( figures 3a ; figure 3b ; message).

[0054] In the real position prediction embodiment, a simulation module is configured to calculate with a predefined time step dt, a theoretical position of the aircraft associated with a roll (P n+1 , Φ n+1 ) which is a function of its previous position (P n , Φ n ). The person skilled in the art can adapt the simulation function in a more or less complex manner depending on the expected calculation accuracy, or even according to technical implementation constraints, such as for example a required calculation execution time.

[0055] So in a particular implementation, the simulation function can be based on the usual equations of flight mechanics: V n = TAS n + Vent mag . cos Vent crs + 180 ° − crs n ; And crs n + 1 = crs n + g . tan Φ n V n . dt .

[0056] The predicted actual position of the aircraft is then obtained by the following equation: P n + 1 = PBD P n , crs n + crs n + 1 2 , V n . dt , where 'PBD' is a commonly known function for calculating a geographic position from a starting position, a direction and a distance.

[0057] If P n+1 corresponds to a position where the aircraft will be inside a right turn or outside a left turn, the roll is calculated according to the following equation: Φ n + 1 = Max − Φ max , Min Φ max , Φ n − TauxDeRoulis . dt .

[0058] If P n+1 corresponds to a position where the aircraft will not be either inside a right turn or outside a left turn, the roll is calculated according to the following equation: Φ n + 1 = Max − Φ max , Min Φ max , Φ n + TauxDeRoulis . dt .

[0059] The simulation function operates until an end condition is reached (step 510). Depending on different options, a simulation end condition can be defined by: reaching a certain change of course, by verifying the condition: | crs fin - crs 0 | > Seuil ; the flight of a certain distance; the flight of a certain time; or even the joining of a predefined trajectory.

[0060] From the simulation results, the method allows to calculate a sequence of segments allowing to trace a predicted real trajectory of the aircraft. This sequence of segments can be optionally a sequence of straight segments defined by positions [ P n , P n +1 ], or a sequence of circular arcs defined by a starting position P n , a starting roll Φ n , a ray R = V n 2 g . tan Φ n and an end position P n +1 .

[0061] THE figures 8 et 9 are representations of the parameters used for the calculation of real position prediction, on a sequence of straight segments ( figure 8 ) and on a sequence of circular arcs ( figure 9 ).

[0062] The simulation module is further configured to verify the conformity of the predicted actual trajectory to a predefined trajectory, and to generate, if necessary, a trajectory deviation alert (step 512) according to a predefined alert configuration.

[0063] Thus, in the embodiment applied to the prediction of the actual position of the aircraft, an alert can be generated ( figure 4a ; figure 4b ; message), if the value of the maximum lateral deviation observed (XTK max) between the predicted actual trajectory and the predefined trajectory does not comply with a maximum value defined in relation to a corridor (RNP) to be respected around the predefined trajectory.

[0064] Thus, the described solution makes it possible to inform the crew of an aircraft or another system (an on-board system or an air traffic control system) in advance of a trajectory tracking problem. Advantageously, the a priori announcement and alert makes it possible to anticipate a resolution of a trajectory tracking problem, and thus both reduce the pilot's workload and improve flight safety.

[0065] Indeed, at certain airports, the procedure must be followed precisely in order to guarantee the separation of the aircraft from the terrain (known procedure of RNP-AR). However, to date, safety is only ensured by prior training of pilots in order to guarantee that the trajectory will be correctly followed. The contribution of the method of the invention allows monitoring to be carried out, by the pilot or by a system, in order to alert on non-compliance with this procedure.

[0066] Furthermore, in some FMS configurations, it is desirable to calculate the trajectory with the planned speed instead of the predicted speed, in order to have a trajectory as close as possible to the official procedure. With this invention it is possible to inform the crew on whether or not this trajectory is being respected by the guidance system and to take the necessary measures to ensure the smooth running of the flight.

[0067] In summary, the invention provides particular advantages on: workload, by allowing anticipation of the resolution of a trajectory tracking problem; and safety, by providing an early warning of a failure to respect a turn.

[0068] This description illustrates a preferred implementation of the invention, but is not limiting. Examples have been chosen to allow a good understanding of the principles of the invention, and a concrete application, but they are not exhaustive and must allow those skilled in the art to make modifications and implementation variants while keeping the same principles.

Claims

1. A method for assisting aircraft guidance, the method being operated by a computation platform for aircraft and comprising at least: - a step of acquisition of state variables characterising an aircraft in flight, of environment variables characterising the environment of the aircraft and of trajectory variables characterising a reference trajectory of the aircraft; characterised in that the method further comprises: - a step of calculation of a predicted real trajectory consisting in calculating prediction variables from said state variables, environment variables and reference trajectory variables, the prediction variables characterising the prediction of a real roll and / or of a real position of the aircraft for an upcoming change of direction of the aircraft; - a step of determination of conformity to determine whether the predicted real trajectory which is calculated conforms to the reference trajectory; and - if the predicted real trajectory does not conform to the reference trajectory, a step of configuration of a trajectory deviation alert informing of the roll and / or of the lateral deviation of the aircraft with respect to the reference trajectory on the upcoming change of direction.

2. The method according to claim 1, wherein the step of determination of conformity consists in comparing the values of said prediction variables to predefined threshold values for the reference trajectory of the aircraft.

3. The method according to claim 2, wherein the step of determination of conformity consists in verifying if the predicted real roll value is greater than a predefined maximum roll value and / or in verifying if the predicted real position of the aircraft corresponds to a lateral deviation value greater than a predefined maximum lateral deviation value.

4. The method according to any one of claims 1 to 3, wherein the step of calculation of a predicted real trajectory comprises an initial step of determination of the position of the aircraft with respect to an upcoming change of direction, for determining if the aircraft is located before the upcoming change of direction or if the aircraft has already engaged in the turn corresponding to the change of direction.

5. The method according to claim 4, wherein the step of calculation of a predicted real trajectory consists in implementing a simulation function to predict a real trajectory of the aircraft, either from the start of the turn for the turn that is to be flown, or from the current position of the aircraft in the turn for the turn segment that remains to be flown.

6. A device for assisting aircraft guidance comprising means for: - acquiring state variables characterising an aircraft in flight, environment variables characterising the environment of the aircraft and trajectory variables characterising a reference trajectory of the aircraft; characterised in that the device further comprises means for: - calculating a predicted real trajectory of the aircraft from said state variables, environment variables and reference trajectory variables, by calculating prediction variables characterising the prediction of a real roll and / or of a real position of the aircraft for an upcoming change of direction of the aircraft; - determining whether the calculated predicted real trajectory conforms to the reference trajectory; and - configuring a trajectory deviation alert if the predicted real trajectory does not conform to the reference trajectory, the alert being configured to inform of the roll and / or of the lateral deviation of the aircraft with respect to the reference trajectory, on the upcoming change of direction.

7. The device according to claim 6, further comprising means configured to operate the steps of the method according to any one of claims 2 to 5.

8. A flight management system (FMS) comprising a device for assisting aircraft guidance according to claim 6 or claim 7.

9. A computer program product, said computer program comprising code instructions for performing the steps of the method for assisting aircraft guidance according to any one of claims 1 to 5, when said program is run on a computer.