Method and device for assisting the control of an aircraft with a head-up display

Description

[0001] The present invention relates to a method and a device for assisting in piloting an aircraft with a head-up display.

[0002] An aircraft may be provided with various displays to display information useful to an operator. In addition, an aircraft may include an autopilot system capable of piloting the aircraft so that at least one flight parameter tends toward a setpoint value.

[0003] The term "operator" can refer to a pilot, a co-pilot, or even any person operating in a cockpit.

[0004] The term “information” may refer to symbols which include; for example; geometric shapes, numbers, letters, these symbols being able to vary over time and being able to represent physical quantities or objects in particular.

[0005] Among this information, the skilled person distinguishes between so-called "primary" information and so-called "secondary" information. Primary information relates to short-term piloting information, or even essential piloting information. Secondary information includes all other displayable information, for example, weather data, route planning data, etc.

[0006] To present this information to an operator, an aircraft may include one or more displays referred to as "head-down displays." A head-down display is visible to an operator when the operator looks downwards and toward the inside of the cockpit. A head-down display may, for example, be carried by a dashboard or even a console.

[0007] As a reminder, when the operator directs his gaze upwards and towards the outside of the aircraft, and therefore in particular towards the environment located above a dashboard and a console, the person skilled in the art considers that this operator is in a “head-up” position. Conversely, when the operator looks at the inside of the aircraft, and in particular the dashboard or the console, the person skilled in the art considers that this operator is in a “head-down” position.

[0008] A head-down display may, for example, include a "screen." In particular, a multifunction display may display various pages that may contain various information. Thus, a multifunction display may display one or more pages containing primary information and / or secondary information. An operator may select which page to display.

[0009] To view the information on such a head-down display, an operator must therefore regularly look inside the cockpit. However, when the aircraft is close to terrain or an obstacle, for example during a winching or rescue operation, a pilot frequently looks outside the cockpit to detect possible danger. Therefore, frequently consulting a head-down display in such a situation increases the pilot's workload and even the risk of an accident.

[0010] Documents EP 3454016 and EP 3869158 disclose head-down displays.

[0011] To address this issue, an aircraft may also include a head-up display to present important information to an operator when that operator is in the head-up position.

[0012] For example, a head-up display may include a screen of a helmet worn by a pilot, a retinal projection means, a windshield projection means, or a device known by the English expression "Head Up display" or its acronym HUD. A head-up display may include, for example, a system called "head mounted display" in English, a system called "head worn display" in English, a system called "near eye display" in English or even a system called "Helmet Mounted Display" when the system is mounted on a helmet, or even a system called for example "Helmet Mounted Sight & Display".

[0013] Regardless of how a head-up display is implemented, this head-up display can reduce a pilot's workload by avoiding the need to consult the head-down displays. The information displayed on the head-up display is superimposed on the external view, where the pilot takes the visual references essential for piloting his aircraft visually. To illustrate this aspect, during a winching operation, a pilot can view the head-up information by observing the scene being flown over through a windshield. The pilot then does not need to look inside the cockpit.

[0014] In addition, the head-up display can collimate the displayed images to infinity or at least to a distance much greater than the distance separating the driver or co-driver from the dashboard. The driver or co-driver therefore does not have to focus their eyes in order to switch from the outside view to reading the information displayed on the head-up display. This feature helps limit user fatigue and reduces the time required to access the displayed information.

[0015] The head-up display also allows information to be displayed overlaid on the external environment: The person skilled in the art then speaks of compliant information. For example, a symbol can be positioned at the precise location of the predetermined landing point.

[0016] A head-up display is therefore interesting. However, the information displayed must be limited. Indeed, displaying a large amount of information on the head-up display can ultimately prevent the user from correctly distinguishing the external environment, which would be contrary to the purpose of the head-up display. Thus, the information displayed on a conventional head-up display is generally limited to essential piloting information, and often does not include useful information relating to an autopilot system.

[0017] Indeed, a pilot may, for example, have an autopilot mode engaged for level flight. The pilot can maneuver the aircraft's controls to change flight level, for example to avoid an obstacle. When the pilot releases the controls, the autopilot system becomes active again. The pilot may have forgotten that the autopilot system is engaged and may be surprised by the aircraft's behavior resulting from the resumption of autopilot.

[0018] For example, a head-down display may present an image comprising a speed indicator, a heading rose, a barometric altitude indicator, an artificial horizon. In addition, this image may contain symbols relating to an active autopilot system, such as a set speed value, a set heading value and a set altitude value, an index pointing to the set speed on the speed indicator, an index pointing to the set heading on the heading rose, an index pointing to the set altitude on the barometric altitude indicator.

[0019] Conversely, the head-up display simply presents an image comprising a speed indicator, a heading scale, a barometric altitude indicator, and a symbol displayed in a compliant manner and bearing the aircraft's air flight direction vector.

[0020] In another aspect, a head-up display may be monochrome, which limits the ability to convey information visually. In addition, a head-up display may include a restricted display area, typically circular / elliptical or potato-shaped, as opposed to a rectangular screen of a head-down display.

[0021] The website www.code450.com / heads-up-display reveals a monochrome head-up display. This display presents a wealth of information, including a strip indicating the active autopilot modes. The field of vision is relatively cluttered.

[0022] The report "Head-up display symbology - Pre-regulatory study for SFACT" dated 2002 and visible on the internet page www.headupflight.net / documents / hudf.pdf presents a head-up display presenting various information during an approach.

[0023] Document FR 3038380 describes a display presenting in particular a slope symbol, a slope scale, constraint symbols and a guidance instruction according to the slope scale.

[0024] These documents are interesting but show displays presenting symbols dedicated to instructions which in fact load the field of vision of an operator.

[0025] The following documents are also known: “EuroFighter C.16 FLIGHT MANUAL”, March 31, 2005 (2005-03-31), XP055179064; retrieved from the Internet: URL: http: / / air.felisnox.com / view.php?name=euroa.pdf, and “FlyRealHUDs Very Brief User's Manual”, December 31, 2012 (2012-12-31), XP093095948; retrieved from the Internet: URL: http: / / flyrealhuds.com / wp-content / uploads / 2020 / 01 / FlyRealHUDs-AirTransport-Users-Manual.pdf.

[0026] The present invention therefore aims to propose an innovative method for optimizing the workload of an aircraft operator, and in particular of a pilot.

[0027] The present invention thus relates to a method for assisting in piloting an aircraft comprising a head-up display and an automatic piloting system, the automatic piloting system comprising a human-machine selection interface for choosing an operating mode from among several predetermined operating modes comprising a disengaged mode and an engaged mode in order to require automatic piloting of at least one parameter, the automatic piloting system being configured in the engaged mode to control at least one actuator of the aircraft in order to make a current value of said parameter tend towards a setpoint value.

[0028] This process involves the following steps: detection with a control system of a current mode applied among said several predetermined operating modes, control of the head-up display with the control system and display on the head-up display of a symbol carrying said current value according to a graphic charter specific to the current mode to visualize the current mode, a first graphic charter applied during the disengaged mode being different from a second graphic charter applied during the engaged mode.

[0029] This method can be implemented for one or more parameters that can be controlled by the autopilot system, and for example for an altitude of the aircraft, a heading of the aircraft, an indicated airspeed of the aircraft, a flight direction vector of the aircraft, and / or holding a stationary position. The flight direction vector can be called in English "Flight Path Vector" and can be illustrated by a compliant symbol.

[0030] The term "graphic charter" refers to the way in which the symbol is displayed, for example, by covering the shape of an object of the symbol and / or the thickness of one or more lines of the symbol and / or the presence or absence of a frame or underline of an object of the symbol. The symbol illustrating a current value of a parameter may include an object presenting at least one number, at least one letter, a scale associated with at least one number and / or a cursor, this object being able to be framed or underlined.

[0031] This method thus proposes to display a single symbol carrying both the current value of the parameter concerned and the state of the operating mode of the autopilot system concerning this parameter. When the symbol has a first appearance defined by the first graphic charter, then an operator deduces that the associated operating mode is the disengaged mode, the autopilot system not controlling this parameter. On the other hand, when the symbol has a second appearance different from the first appearance and defined by the second graphic charter, then an operator deduces that the associated operating mode is the engaged mode, the autopilot system controlling this parameter.

[0032] From a "Human" point of view, updating the visual appearance of a symbol, for example via a change in shape or the appearance of a frame or underline or even the thickening of a line, is sufficient to update the mental representation that an operator constructs with regard to the current operating modes of the automatic pilot system.

[0033] As a result, the method allows an operator to easily know, even on a monochrome head-up display, and by significantly limiting the obscuring of part of the external environment, what the current operating mode of the autopilot system is with regard to one or more parameters. The method does not require the display of a symbol dedicated to autopilot, such as a usual autopilot information banner, or the display of one or more instructions as such, to know what the current operating mode is.

[0034] The process thus has a limited impact on an operator's field of vision by not necessarily adding symbols when the autopilot system is active. A pilot's workload, for example, is thus simplified since the pilot does not need to consult a head-down display or a head-up display overloaded with information. Flight safety can thus be increased.

[0035] The method may further include one or more of the following features.

[0036] According to one possibility, for the same current value, the symbol can be in the same position on the head-up display regardless of the current mode.

[0037] The same symbol takes on different appearances when the operating mode of the autopilot system changes, but does not move on the head-up display. The invention provides a single symbol that changes appearance, unlike systems having two separate and independent symbols carrying respectively a current value of a parameter and a setpoint.

[0038] According to a possibility compatible with the previous ones, said symbol may comprise an object according to the first graphic charter, said symbol comprising said object and a frame at least partially surrounding the object according to the second graphic charter.

[0039] Such an object can take the form, for example, of a number, or a scale associated with a cursor and / or a number. The presence of a frame can be easily identified by an operator in order to determine the current operating mode with regard to the parameter under examination.

[0040] According to another possibility, said symbol may comprise a first object according to the first graphic charter, said symbol comprising according to the second graphic charter a second object visually different from the first object.

[0041] The first and second objects may take the form of, for example, a number, a particular geometric shape, or a scale associated with a cursor and / or a number. Depending on the object displayed to present the current value of a parameter, an operator can easily deduce what the current operating mode is with respect to this parameter.

[0042] For example, the first object may comprise a first geometric shape, the second object comprising a second geometric shape, the second shape being visually different from the first shape.

[0043] For illustrative purposes, a symbol compliantly illustrating an aircraft flight direction vector may typically comprise a circle and two aligned segments on either side of the circle when the flight direction vector autopilot is disengaged. In the engaged mode, the circle may be replaced by a diamond, for example. An operator can thus easily determine whether the flight direction vector hold mode is engaged or not.

[0044] In a complementary or alternative manner, the first object and the second object may comprise at least one of the same lines, the line having a first thickness in the first object, the line having in the second object a second thickness greater than the first thickness.

[0045] According to the preceding example, a symbol compliantly illustrating a flight direction vector of the aircraft may usually comprise a circle and two segments aligned on either side of the circle when the automatic piloting of the flight direction vector is disengaged. In the engaged mode, the segments may be made with thicker lines, the circle or where appropriate the diamond replacing it also being made with such thick lines. An operator can thus easily know whether the flight direction vector holding mode is engaged or not.

[0046] According to a possibility compatible with the previous ones, said several operating modes can include an armed mode during which said setpoint value is configured, provided that the current mode is the armed mode then said method can include a control of the head-up display with the control system and a display on the head-up display of said symbol according to a third graphic charter different from the first graphic charter and the second graphic charter.

[0047] Thus, an operator can know if an autopilot mode is disengaged, armed or engaged with the symbol carrying the current value of the parameter concerned.

[0048] According to a possibility compatible with the previous ones, during a change of mode to go from an old mode to a new mode chosen from among said several operating modes, said method can comprise a control of the head-up display with the control system and a display on the head-up display of said symbol, for a predetermined transient duration, alternately according to the graphic charter of the old mode and the graphic charter of the new mode.

[0049] This feature allows an operator's attention to be drawn to indicate that the autopilot system is changing operating mode for the relevant parameter, again without adding a dedicated symbol.

[0050] According to a possibility compatible with the previous ones, the method may include a detection that the current value is different from the set value, and provided that the current value is different from the set value, the method may include a control of the head-up display with the control system and a display on the head-up display of the set value opposite said symbol.

[0051] The setpoint can be in close proximity to the associated symbol. Optionally, a segment can connect the setpoint and the symbol so that an operator can immediately make the connection between the setpoint and the relevant parameter.

[0052] Optionally, this feature allows an operator to additionally know whether the autopilot system's setpoint has been reached.

[0053] Optionally, the setpoint value can be displayed to an operator above the symbol when the setpoint value is greater than the current value and below the symbol when the setpoint value is less than the current value.

[0054] This feature allows an operator to also know whether the setpoint is greater or less than the current value of the parameter.

[0055] Optionally, a segment extends from the setpoint to the associated symbol

[0056] Optionally, a distance separating the setpoint value and the associated symbol varies according to a gap separating the setpoint value from the current value of the parameter concerned. This distance can be obtained using a law giving the distance only as a function of the aforementioned gap.

[0057] Thus, this setpoint value gradually translates by approaching (respectively: moving away from) the current value as the aircraft approaches (respectively: moves away from) said setpoint. If necessary, the possible segment shortens (respectively: lengthens) in line with the translation.

[0058] Thus, the positioning of the setpoint value in relation to the associated symbol carries the numerical difference between this setpoint value and the current value carried by this symbol.

[0059] In addition to a method, the invention relates to an aircraft implementing this method.

[0060] Such an aircraft comprises a head-up display and an autopilot system, the autopilot system comprising a human-machine selection interface for choosing an operating mode from several predetermined modes comprising a disengaged mode and an engaged mode in order to require automatic piloting of at least one parameter, the autopilot system being configured in the engaged mode to control at least one actuator of the aircraft in order to cause a current value of a piloted parameter to tend towards a setpoint value, said aircraft comprising a control system for controlling said head-up display.

[0061] The control system and the head-up display are then configured to apply the method of the invention. In particular, the head-up display may be monochrome.

[0062] The invention and its advantages will appear in more detail in the context of the description which follows with examples given for illustrative purposes with reference to the appended figures which represent: there figure 1 , a diagram illustrating an aircraft according to the invention, the figure 2 , a diagram showing a head-down display of the aircraft, the figure 3 , a diagram illustrating the method of the invention, the figure 4 , a diagram showing a head-up display of an aircraft according to the invention to illustrate the method of the invention, and the figure 5 , a diagram showing a head-up display of an aircraft according to the invention to illustrate the method of the invention.

[0063] Elements present in several distinct figures are assigned a single reference.

[0064] There figure 1 shows an aircraft 1 of the type of the invention, such as an airplane or a rotorcraft. Only the parts of the aircraft 1 having a direct link with the invention are illustrated so as not to unnecessarily burden the figure 1 .

[0065] This aircraft 1 has a cockpit 5 in which there is at least one operator 6.

[0066] This aircraft 1 comprises an automatic pilot system 20. Such an automatic pilot system 20 is sometimes called AFCS, the acronym AFCS corresponding to the English expression “Automatic Flight Control System”.

[0067] The autopilot system 20 comprises at least one actuator 25 for piloting the aircraft 1 to cause the current value of a PAR parameter to tend towards a set value. For example, on a rotorcraft equipped with a rotary wing, an actuator can be extended or retracted or rotated to modify the pitch of the blades of the rotary wing. This example is simply given to illustrate the invention.

[0068] The actuator(s) may be controlled by an automatic piloting computer 21 connected by wired or wireless links to the actuator(s) 25. The automatic piloting computer 21 may comprise, for example, at least one processor and at least one memory, at least one integrated circuit, at least one programmable system, at least one logic circuit, these examples not limiting the scope given to the expression “computer”. The term processor may also designate a central processing unit known by the acronym CPU, a graphics processing unit GPU, a digital unit known by the acronym DSP, a microcontroller, etc.

[0069] Furthermore, this automatic piloting system 20 can be equipped with a human-machine adjustment interface connected by a wired or wireless link to the automatic piloting computer 21 in order to configure the value(s) of the setpoint(s).

[0070] Furthermore, the autopilot system 20 is connected to one or more sensors directly or via at least one avionics computer by a communication network connection. The sensor(s) make it possible to estimate the current value(s) of the parameter(s) that can be controlled by the autopilot system 20. Each sensor generates a signal, for example digital or analog, electrical or optical, relating to at least one parameter. Each sensor may comprise a sensor capable of directly measuring the parameter in question but also a system that may comprise one or more physical sensors as well as signal processing means making it possible to provide an estimate of the parameter from the measurements provided by this or these sensors.

[0071] As an illustrative example, the aircraft 1 may comprise a speed sensor 46 for measuring a PAR parameter of the indicated airspeed IAS type. Such a speed sensor 46 may comprise, for example, an anemometer.

[0072] The aircraft 1 may comprise an altitude sensor 47 for measuring a PAR parameter of altitude ALT type. Such an altitude sensor 47 may comprise, for example, a radio altimeter.

[0073] The aircraft 1 may comprise a heading sensor 48 for measuring a PAR parameter of the heading CP type. Such a heading sensor 48 may comprise, for example, a compass.

[0074] The aircraft 1 may comprise a flight direction vector sensor 49 for measuring a PAR parameter of the flight direction vector type VVIT. Such a flight direction vector sensor 49 may comprise, for example, an inertial unit.

[0075] Furthermore, the autopilot system 20 is provided with a human-machine selection interface 22 allowing the operator 6 to choose for one or more PAR parameters an autopilot mode more simply called operating mode. This operating mode can be either a disengaged mode, an engaged mode, or even an armed mode. When the disengaged mode is activated for a parameter, the autopilot system does not perform any action for this parameter. When the armed mode is activated for a parameter, a setpoint value can be configured. When the engaged mode is activated to maintain a PAR parameter, the autopilot system 20, and in particular the autopilot computer 21, is configured to control at least one actuator 25 in order to make the value of the PAR parameter, evaluated with the required sensor(s), tend towards a setpoint value.

[0076] Furthermore, the aircraft 1 is equipped with displays to present various information to the eyes 7 of the operator 6.

[0077] In particular, the aircraft 1 may comprise a head-down display 10 visible to the operator 6 when his gaze follows a head-down line of vision VSTB. The head-down display 10 is possibly carried by a console or an instrument panel 11. Such a head-down display 10 may comprise a screen, and for example a multifunction screen known by the acronym MFD and the English expression “Multi Functions Display”.

[0078] In reference to the figure 2 , such a head-down display 10 can present an image comprising numerous pieces of information, and for example a speed indicator 101 presenting where appropriate a speed setpoint 102, a heading rose 103 presenting where appropriate a heading setpoint 104, a barometric altitude indicator 105 presenting where appropriate an altitude setpoint 106, an artificial horizon 108, and an automatic piloting strip 110 presenting the automatic piloting modes engaged and the associated setpoint values.

[0079] Furthermore, the aircraft 1 comprises a head-up display 30 and a control system 40 for controlling this head-up display 30. The control system 40 is configured to transmit a signal to the head-up display 30, the head-up display 30 displaying one or more symbols following the reception of this signal. Optionally, the head-up display 30 is monochrome. The head-up display 30 then displays symbols in a single color, usually green.

[0080] The head-up display 30 may be fixed, for example of the HUD type, or may be worn. The head-up display 30 may be of a conventional type, and for example may be a system called a “head-mounted display”, a system called a “head-worn display”, a system called a “near-eye display”, a system called a “Helmet Mounted Display” when mounted on a helmet or for example a “Helmet Mounted Sight & Display”.

[0081] The head-up display 30, or even the head-down display 10, can be controlled by a computer called for convenience “display computer 45”. A display computer 45 is thus connected by a wired or wireless connection to the head-up display 30 or even to the head-down display 10. Optionally, the display computer 45 and the automatic pilot computer 21 can form a single computer.

[0082] The display computer 45 may comprise one or more symbol generating computers. For example, the display computer 45 may comprise a head-up symbol generating computer and a head-down symbol generating computer. According to another example, the display computer 45 may comprise a single symbol generating computer. Each symbol generating computer may comprise, for example, at least one processor and at least one memory, at least one integrated circuit, at least one programmable system, at least one logic circuit, these examples not limiting the scope given to the expression “symbol generating computer”. The term processor may also designate a central processing unit known by the acronym CPU, a graphics processing unit GPU, a digital unit known by the acronym DSP, a microcontroller, etc.

[0083] The display computer 45 can be connected directly or indirectly to the various sensors of the aircraft 1, and in particular to the aforementioned sensors 46-49.

[0084] Furthermore, the display computer 45 can be connected to a positioning device 44 determining information relating to the position or even the orientation of the head-up display 30, in the case of a worn head-up display 30.

[0085] The positioning device 44 is connected to the display computer 45 by a wired or wireless connection in order to transmit to it a signal, for example analog or digital. This signal allows the display computer 45 to determine, using a known technique, where to position certain symbols. According to the example illustrated, the positioning device 44 thus comprises at least one camera.

[0086] The examples given are provided for illustrative purposes. The control system 40 and the automatic pilot system 20 may in fact be of another known type without departing from the scope of the claims.

[0087] Regardless of the embodiment of the head-up display 30 as well as the control system 40 and the autopilot system 20, the control system 40 and the head-up display 30 are configured to apply the method illustrated schematically in the figure 3 This process involves one or more of the following steps performed in a loop.

[0088] This method comprises, for at least one PAR parameter, an STP0 detection with a control system 40 of a current mode applied by the automatic piloting system 20. The current mode is in fact chosen by an operator 6 from among the predetermined operating modes of the automatic piloting system 20. For example, the human-machine selection interface 22 transmits a signal carrying the current mode to be applied to the control system 40, possibly to the display computer 45, directly or via the automatic piloting computer 21.

[0089] The method then comprises the control STP1, STP2, STP3 of the head-up display 30 with the control system 40, and in particular with the display computer 45. The control system 40 then transmits a control signal to the head-up display 30 which varies according to the current mode applied for each PAR parameter. The control signal may comprise the symbols to be displayed. Following reception of the control signal, the method then comprises, for each PAR parameter, a display STP11, STP21 STP31 on the head-up display 30 of a symbol 50 carrying the current value of the PAR parameter according to a graphic charter specific to the current mode.

[0090] Thus, when the operating mode of the autopilot system 20 is the disengaged mode for a PAR parameter, the display computer 45 performs the STP1 command of the head-up display 30 by transmitting a control signal to it. Following the reception of this control signal, the head-up display 30 performs a STP11 display of a symbol carrying the current value of this PAR parameter according to a first graphic charter. The first graphic charter defines the appearance to be given to this symbol.

[0091] This symbol can include an object. This object can be a number equal to the current value, a scale and a cursor pointing on the scale a value equal to the current value for example, a geometric shape. Therefore, the graphic charter can define for example the thickness of at least one line of an object, the addition or not of a frame at least partially around the object, what shape the object must have...

[0092] When the operating mode of the autopilot system 20 is the mode engaged for a PAR parameter, the display computer 45 performs the STP2 command of the head-up display 30 by transmitting a control signal to it. Following the reception of this control signal, the head-up display 30 performs a STP21 display of a symbol carrying the current value of this PAR parameter according to a second graphic charter. The appearance of the symbol is different with the second graphic charter from the appearance obtained with the first graphic charter for the same value of the PAR parameter.

[0093] When the operating mode of the autopilot system 20 is the armed mode for a PAR parameter, the display computer 45 performs the STP32 command of the head-up display 30 by transmitting a control signal to it. Following the reception of this control signal, the head-up display 30 performs an STP31 display of a symbol carrying the current value of this PAR parameter according to a third graphic charter. The third graphic charter defines the appearance to be given to this symbol, the appearance of the symbol being different from the appearance obtained with the first graphic charter and the second graphic charter for the same value of the PAR parameter.

[0094] THE figures 4 And 5 illustrate the method of the invention with examples.

[0095] There figure 4 illustrates the display of symbols 50 associated with PAR parameters for which the autopilot system 20 is not engaged. The figure 5 illustrates the display of symbols 50 associated with these same PAR parameters but for which the autopilot system 20 is engaged. Reference 50 designates any symbol, references 51 to 54 designating particular symbols.

[0096] According to the example illustrated on the figure 4 , the head-up display 30 may present a symbol 51 carrying the current value of the indicated airspeed measured with the speed sensor 46, a symbol 52 carrying the current value of the altitude measured with the altitude sensor 47, a symbol 54 carrying the current heading value measured with the heading sensor 48 and a symbol 53 carrying the current flight direction vector displayed in a compliant manner and measured with the flight direction vector sensor 49.

[0097] According to a first variant, a symbol 50 may comprise an object 60 according to the first graphic charter, and this same object 60 and a frame 61 surrounding it at least partially according to the second graphic charter.

[0098] According to the figure 4 , this object 60 may comprise a number equal to the current value of the associated PAR parameter, or even letters forming the unit used, as illustrated on the symbol 51 carrying the current value of the indicated airspeed and on the symbol 52 carrying the current value of the altitude. An object 60 may alternatively comprise a scale 541 and a pointer 542, as illustrated with the symbol 54 carrying the current heading value.

[0099] Optionally, object 60 may be underlined when applying the third graphic charter to indicate that the autopilot mode associated with the associated PAR parameter is the armed mode. Symbol 51 bearing the current value of the indicated airspeed thus includes broken lines under the corresponding object to illustrate this possibility.

[0100] In reference to the figure 5 , when the autopilot system is engaged to pilot the aforementioned PAR parameters, a symbol 50 comprises a frame 61 which at least partially surrounds the object 60. Thus, the symbol 51 and the symbol 52 both comprise an object 60 completely framed by a rectangular frame 61 according to the example given, while the symbol 54 comprises a frame 61 which partially surrounds its object. The frame 61 may however have a completely different shape and for example a hexagonal shape.

[0101] According to a second variant and with reference to the figure 4 , said symbol 53 may comprise a first object 63 according to the first graphic charter. Thus, the symbol 53 carrying the flight direction vector comprises a first geometric shape comprising two segments 65, 66 on either side of a circle 67, the two segments 65, 66 being aligned.

[0102] On the other hand and as illustrated on the figure 5 , this same symbol 53 may comprise, according to the second graphic charter, a second object 64 visually different from the first object 63.

[0103] For example, the first object 63 comprises a first geometric shape, the second object 64 comprises a second different geometric shape. Thus, the symbol 53 carrying the flight direction vector now comprises a second geometric shape comprising two segments 65, 66 on either side no longer of a circle 67 but of a diamond 68, the two segments 65, 66 being aligned.

[0104] For example, the first object 63 and the second object 64 may comprise at least one of the same lines. Thus, the first object 63 and the second object 64 both comprise the segments 65, 66 according to the example of the symbol 53. However, the lines 65, 66 have a first thickness ep1 in the first object 63 visible on the figure 4 and a second thickness ep2 greater than the first thickness ep1 within the second object 64 visible on the figure 5 .

[0105] Whatever the variant, the graphic charter applied does not influence the position of the symbol 50 on the head-up display 30. For the same current value of a PAR parameter, the associated symbol 50 is in the same position, namely in the same restricted zone of the head-up display 30, whatever the graphic charter applied.

[0106] Furthermore, during a transient phase of transition from an old mode to a new mode chosen from said possible operating modes of the automatic piloting system 20, for example to illustrate a transition from the disengaged mode to the engaged mode, the control system 40 can control the head-up display 30, to display on the head-up display 30 the symbol 50 concerned, for a predetermined transient duration, alternately according to the graphic charter of the old mode and the graphic charter of the new mode.

[0107] According to another aspect of the invention and with reference to the figure 5, the control system 40 may be configured to perform an STP4 detection that the current value of a parameter is different from its setpoint value transmitted by the automatic pilot system 20. In this case, the method of the invention may comprise an STP41 command transmitted from the control system 40 to the head-up display 30 to request an STP42 display on the head-up display 30 of the setpoint value 85 opposite the symbol 50 concerned. A segment 86 may optionally extend from the setpoint value to the symbol 50. Optionally, the setpoint value is placed in the eyes 7 of the operator 6 above the symbol 50 when the setpoint value 85 is greater than the current value and below the symbol 50 when the setpoint value 85 is less than the current value.According to the illustrated example, a set value 851 for the indicated air speed is thus arranged above the symbol 51 and a set value 852 for the altitude is arranged below the symbol 52.

[0108] Optionally, a distance D1, D2 separating the setpoint value and the associated symbol varies according to the result of a subtraction between the setpoint value and the current value of the parameter concerned. The same applies to the length of the segment possibly displayed. Although several embodiments have been described, it is understood that it is not conceivable to exhaustively identify all the modes

Claims

1. A method for assisting the piloting of an aircraft (1) comprising a head-up display (30) and an automatic flight control system (20), the automatic flight control system (20) comprising a human-machine selection interface (20) for choosing an operating mode from among several predetermined operating modes comprising a disengaged mode and an engaged mode in order to request an automatic control of at least one parameter, the automatic flight control system (20) being configured, in the engaged mode, to control at least one actuator (25) of the aircraft (1) in order to bring a current value of said parameter (PAR) towards a setpoint value, the method comprising the following steps: - detecting (STP0), with a control system (40), an applied current mode from among said several predetermined operating modes, - controlling (STP1, STP2, STP3) the head-up display (30) with the control system (40), and displaying (STP11, STP21, STP31) a symbol (50) carrying said current value on the head-up display (30), characterised in that a symbol (50) carrying said current value is displayed (STP11, STP21, STP31) on the head-up display (30) according to a graphic charter specific to the current mode in order to display the current mode, a first graphic charter applied during the disengaged mode being different from a second graphic charter applied during the engaged mode.

2. The method according to claim 1, characterised in that, for a given current value, the symbol (50) is in the same position on the head-up display (30), irrespective of the current mode.

3. The method according to any one of claims 1 to 2, characterised in that said symbol (50) comprises an object (60) according to the first graphic charter, said symbol (50) comprising said object (60) and a frame (61) at least partially surrounding the object (60) according to the second graphic charter.

4. The method according to any one of claims 1 to 3, characterised in that said symbol (50) comprises a first object (63) according to the first graphic charter, said symbol (50) comprising, according to the second graphic charter, a second object (64) which is visually different from the first object (63).

5. The method according to claim 4, characterised in that said first object (63) comprises a first geometric shape, the second object (64) comprising a second geometric shape, the second shape being visually different from the first shape.

6. The method according to any one of claims 4 to 5, characterised in that the first object (63) and the second object (64) comprise at least one common line (65, 66), the line (65, 66) being a first thickness (ep1) in the first object (63), the line (65, 66) being a second thickness (ep2) greater than the first thickness (ep1) in the second object (64).

7. The method according to any one of claims 1 to 6, characterised in that said several operating modes comprise an armed mode, during which said setpoint value is parameterised; provided that the current mode is the armed mode then said method comprises controlling (STP3) the head-up display (30) with the control system (40) and displaying (STP31) said symbol (50) on the head-up display (30) according to a third graphic charter different from the first graphic charter and the second graphic charter.

8. The method according to any one of claims 1 to 7, characterised in that, during a change in mode to switch from an old mode to a new mode chosen from said several operating modes, said method comprises controlling the head-up display with the control system (40) and displaying said symbol on the head-up display (30) for a predetermined transitional period, alternately according to the graphic charter of the old mode and the graphic charter of the new mode.

9. The method according to any one of claims 1 to 8, characterised in that said method comprises detecting (STP4) that the current value is different from the setpoint value and, provided that the current value is different from the setpoint value, the method comprises controlling (STP41) the head-up display (30) with the control system (40) and displaying (STP42) the setpoint value opposite said symbol on the head-up display (30).

10. The method according to claim 9, characterised in that, in relation to the eyes of an operator, the setpoint value is arranged above the symbol when the setpoint value is greater than the current value, and below the symbol when the setpoint value is less than the current value.

11. The method according to any one of claims 9 to 10, characterised in that a distance separating the setpoint value and the associated symbol varies as a function of a difference separating the setpoint value from the current value of the parameter in question.

12. An aircraft (1) comprising a head-up display (30) and an automatic flight control system (20), the automatic flight control system (20) comprising a human-machine selection interface (20) for choosing an operating mode from among several predetermined modes comprising a disengaged mode and an engaged mode in order to request the automatic control of at least one parameter, the automatic flight control system (20) being configured, in the engaged mode, to control at least one actuator (25) of the aircraft (1) in order to bring a current value of the controlled parameter towards a setpoint value, said aircraft (1) comprising a control system (40) for controlling said head-up display (30), characterised in that the control system (40) and the head-up display (30) are configured to apply the method according to any one of claims 1 to 10.

13. The aircraft according to claim 11, characterised in that said head-up display (30) is monochromatic.