AID AND DEVICE FOR CONTROLLING AN AIRCRAFT IN FLIGHT

Description

[0001] The present invention is in the field of piloting aids for aircraft and rotorcraft in particular.

[0002] The present invention relates to a method for assisting in piloting an aircraft in flight and to a system for assisting in piloting an aircraft in flight.

[0003] The aircraft may be a rotorcraft comprising at least one rotating wing, for example at least one lifting rotor, enabling it in particular to perform stationary flights as well as forward flights at low speeds. An aircraft may also perform takeoffs and landings on landing areas of reduced dimensions.

[0004] An aircraft can land on prepared landing pads. A prepared landing pad can be located on the ground, on the roof of a building, as well as on a boat or a platform located at sea.

[0005] An aircraft may also land on unprepared landing areas located in an urban environment, and therefore potentially surrounded by buildings and / or street furniture in particular. An aircraft may also land on unprepared landing areas located in a natural environment and in this case potentially surrounded by vegetation and likely not to be perfectly flat, or even to contain rocks.

[0006] Therefore, in order to assist a pilot during the landing and takeoff phases, the cockpit of an aircraft may include a transparent area, for example a glazed area, at the pilot's feet so as to allow him to see the ground. However, the view of the ground remains partial and the observable area has dimensions which reduce as the aircraft approaches the ground. Near the landing area, the pilot may not be able to see the possible contact points for at least some of the aircraft's landing gear.

[0007] An aircraft may also include a landing point indication system as described in document EP 2708853. This system includes at least one camera and a screen displaying a view of the area below the aircraft. This system also includes a device for measuring an attitude of the aircraft. The screen displays an indication of the projected position of the aircraft on the ground, in particular as a function of its attitude.

[0008] Furthermore, document US 2012 / 0154178 describes a method for presenting attitude and heading information of an aircraft on a display, consisting of using data provided by an inertial unit to represent three-dimensional graphic elements on a two-dimensional display, and presenting the attitude (roll, pitch, or even yaw) and heading information on the two-dimensional display by associating them with at least one spatial attitude graphic element indicating the attitude of the aircraft. For example, a transparent fixed sphere represents an inertial reference frame, with two upper and lower half-spheres representing the sky and the ground respectively.

[0009] In this context, the present invention aims to overcome the limitations mentioned by proposing assistance in piloting an aircraft by allowing the pilot to visualize, substantially in real time or quasi-real time, the area located under the aircraft as well as the position of the aircraft.

[0010] The present invention then relates to a method for assisting in piloting an aircraft in flight according to claim 1, as well as a system for assisting in piloting an aircraft in flight according to claim 15.

[0011] The aircraft structure includes, for example, an airframe, or even a tail boom and / or wings. A pilot and possibly other occupants are installed in the airframe during the aircraft's flight.

[0012] The horizon circle represents the projection of the horizon line around the aircraft. The diameter of the horizon circle is constant, i.e. independent of the height and attitude of the aircraft. The value of the diameter of the horizon circle is predetermined, in particular depending on the dimensions of the display device as well as the dimensions of the representation and / or the optical characteristics of the capture device.

[0013] The first position and the second position which respectively correspond to vertical projections on the area flown over of a first reference point of the aircraft and of a second reference point of the image capture device move on the representation during changes in attitude of the aircraft.

[0014] In fact, the symbol illustrating the aircraft's footprint on the area flown over moves on the representation when the aircraft's attitude changes.

[0015] The second position can advantageously be calculated without using the height of the aircraft, although this position is a function of this height. This second position is the position of a vertical projection onto the overflown area of ​​a second reference point of the image capture device. Therefore, this second position can be determined relative to the center of the image captured by the image capture device as a function of a parameter of the image capture device and the attitude of the aircraft. This parameter is for example the focal length of the lens of the image capture device, this focal length being fixed in this case. This parameter can also be an equivalent focal length when the representation of the overflown area is formed from several images.

[0016] Alternatively, this second position can be calculated based on the aircraft's attitude and height.

[0017] Similarly, the horizon circle, which is always centered on the second position, also moves on the representation when the aircraft's attitude changes. As a result, and depending on the aircraft's attitude, the horizon circle may only be partially displayed on the representation, for example when the aircraft has a significant pitch-up angle and / or roll angle. The horizon circle thus allows the aircraft pilot to visualize on the representation the aircraft's attitude changes as well as obstacles located high above, in particular above the horizon circle.

[0018] By displaying the projected position of the aircraft on the area flown over and the horizon circle on the display device superimposed on the representation of the area flown over, the pilot can locate the aircraft in relation to the area flown over, and in particular in relation to the landing area and any obstacles or objects located on or near the landing area.

[0019] The pilot can then safely land on any type of landing area, whether prepared or not.

[0020] The image capture device is directed towards the ground and allows images to be captured of the area overflown by the aircraft while the aircraft is in flight. The image capture device can be attached to the airframe or tail boom, or even to a wing.

[0021] The area flown over can be, for example, the ground, the roof of a building, a boat or even a platform located at sea.

[0022] The height of the aircraft relative to the overflown area is equal to the shortest distance between the aircraft and the overflown area, this height being defined parallel to the direction of Earth's gravity. The height of the aircraft can be defined, for example, relative to a predetermined point on the aircraft.

[0023] The attitude of the aircraft characterizes the attitude of the aircraft, namely its roll angle and its pitch angle around a roll axis and a pitch axis of the aircraft respectively. The aircraft has a zero attitude when its roll angle and its pitch angle are simultaneously equal to zero. The roll and pitch axes of the aircraft are then parallel to a horizontal plane defined perpendicular to the direction of Earth's gravity.

[0024] The method according to the invention may further comprise one or more of the following characteristics, taken alone or in combination.

[0025] According to one example, the representation of the overflown area covers an angular field of 360° in a horizontal plane and at least 180° in a vertical plane when the attitude of the aircraft is zero, the vertical plane being parallel to a direction of Earth's gravity and the horizontal plane being perpendicular to the direction of Earth's gravity. In this way, the pilot has an overview of the overflown area in order to understand all the obstacles likely to be in the overflown area, in particular the high obstacles exceeding the horizon circle. Preferably, the representation of the overflown area covers an angular field of 360° in a horizontal plane and at least 220° in a vertical plane when the attitude of the aircraft is zero.

[0026] This representation of the overflown area is sufficient to allow the pilot of the aircraft to become aware of the environment of the landing area and then to carry out a landing maneuver in complete safety. Furthermore, in this case, the representation of the overflown area allows the pilot to have an idea of ​​the attitude of the aircraft, in particular thanks to the relative movements of the sky on the representation of the overflown area and the position of the horizon circle which may be off-center on the representation of the overflown area.

[0027] According to another example compatible with the preceding ones, the image capture device may comprise at least one single camera or one single photographic device.

[0028] According to a first variant, the image capture device may comprise a single camera or a single photographic device fixed relative to the structure of the aircraft and provided with a lens covering an angular field of 360° in a plane perpendicular to an optical axis of the camera or photographic device and a field of at least 180° in a plane parallel to this optical axis. This optical axis is for example parallel to a direction of Earth's gravity when the aircraft has a zero attitude. The second reference point of the image capture device is then the center of this lens. The representation of the area flown over then corresponds exactly to the image captured by the image capture device.

[0029] For this purpose, the camera or photographic device may include a "fish-eye" type lens. Such a lens, by its construction, causes a deformation of the captured image according to an equidistant or equisolid projection, for example.

[0030] According to a second variant, the image capture device may comprise a single camera or a single photographic device movable relative to the structure of the aircraft in order to cover an angular field of 360° in a horizontal plane and a field of at least 180° in a vertical plane.

[0031] According to a third variant, the image capture device may comprise several cameras or several photographic devices fixed relative to the structure of the aircraft and jointly covering an angular field of 360° in a horizontal plane and a field of at least 180° in a vertical plane.

[0032] For the second and third variants, the representation of the area flown over is then constructed by the calculator from the images provided by the image capture device. The representation of the area flown over can have an equidistant or equisolid projection for example.

[0033] According to another example compatible with the preceding ones, the symbol can be represented on the display device with dimensions that vary depending on the height. In this way, the dimensions of the symbol can be representative of the dimensions of the vertical projection of the aircraft on the area flown over, being variable depending on the height of the aircraft.

[0034] The method may in this case include an additional step of calculation by the calculator of the dimensions of the symbol at least as a function of the height of the aircraft. This additional calculation step possibly uses the dimensions of the aircraft and the height of the aircraft to calculate the dimensions of the symbol.

[0035] The symbol may also be represented on the display device with constant dimensions when the height is greater than a first predetermined threshold and the symbol may be represented on the display device with variable dimensions, possibly representative of the dimensions of the vertical projection of the aircraft on the area flown over, at least as a function of the height when the height is less than or equal to the first threshold. The dimensions of the symbol allow the pilot to assess the height of the aircraft. The first threshold is for example equal to 150 feet (150fts), one foot being equal to 0.3048 meters.

[0036] In this case, the method may also include the additional step of calculating the dimensions of the symbol, this step being applied when the dimensions of the symbol are variable depending on the height.

[0037] In addition, to avoid an untimely change in the management of the symbol dimensions around a height equal to the first threshold, a hysteresis threshold can be used. The first threshold then includes a first high threshold and a first low threshold. The symbol is represented with constant dimensions when the height is greater than the first high threshold and the symbol is represented with variable dimensions when the height is less than or equal to the first low threshold. When the height decreases from a value greater than the first high threshold and remains greater than the first low threshold, the symbol is represented with constant dimensions. Conversely, when the height increases from a value less than the first low threshold and remains less than the first high threshold, the symbol is represented with variable dimensions.

[0038] A first threshold hysteresis value is equal to the difference between the first high threshold and the first low threshold, and is for example equal to 20 feet.

[0039] According to another example compatible with the preceding ones, the symbol can be represented on the display device with different shapes when said height is greater than a first predetermined threshold and when said height is less than or equal to said first threshold. In this way, such a change in shape of the symbol can indicate to the rotorcraft pilot that the aircraft is at a height less than or equal to the first threshold and is therefore approaching the area overflown. In this case, a first threshold can also be a hysteresis threshold as previously mentioned.

[0040] The method may also simultaneously associate a change in the shape of the symbol and a variation in the dimensions of the symbol with the passage of the first threshold. A first symbol may thus be represented on the display device with constant dimensions when the height is greater than the first predetermined threshold and a second symbol, different from the first symbol, may be represented on the display device with variable dimensions depending on the height of the aircraft when the height is less than or equal to the first threshold.

[0041] Furthermore, the symbol can be displayed on the display device with constant dimensions regardless of the height of the aircraft. In this way, regardless of the height of the aircraft, the aircraft symbol is displayed with the same dimensions.

[0042] According to another example compatible with the previous ones, the aircraft may comprise at least one lift rotor, arranged for example above the structure, and the symbol then comprises a shape representing the structure and at least one rotor circle corresponding to the lift rotor. The method then comprises the additional step of calculating the dimensions of the symbol and during this additional calculation step, the dimensional characteristics of said at least one rotor circle and the dimensional characteristics of the shape representing the structure are calculated as a function respectively of the diameter of said at least one lift rotor and the dimensions of the structure as well as the height of the aircraft. This additional calculation step makes it possible in particular to transfer said at least one rotor circle and the shape representing the structure from a reference frame linked to the aircraft to a reference frame linked to the image capture device.

[0043] According to another example compatible with the previous ones, the aircraft comprising at least one lift rotor, the first reference point of the aircraft can be a center of rotation of a lift rotor among said at least one lift rotor.

[0044] According to another example compatible with the previous ones, the first measuring device may comprise for example at least one inertial unit or a device known by the acronym AHRS for the English designation "Attitude and Heading Reference System", at least one inclinometer or other, in order to determine or measure the attitude of the aircraft, namely its roll and pitch angles.

[0045] According to another example compatible with the previous ones, the second measuring device can make it possible to directly measure the height of the aircraft relative to the area flown over and can include for this purpose a radiosonde for example. The step of determining a height of the aircraft relative to the area flown over thus includes a measurement of this height by the second measuring device.

[0046] The second measuring device may alternatively comprise a barometric altimeter for measuring a current atmospheric pressure, which is then compared with an atmospheric pressure at the altitude of the area flown over in order to calculate the height of the aircraft relative to the area flown over.

[0047] The second measuring device may alternatively comprise at least one receiver of a satellite positioning system. The receiver provides a position of the aircraft in a terrestrial reference frame, for example in the form of coordinates in latitude, longitude and altitude relative to a reference level, generally sea level. This position of the aircraft in the terrestrial reference frame is then combined with a stored three-dimensional terrain model or with information from a stored terrain database in order to determine the height of the aircraft relative to the area flown over.

[0048] Three-dimensional terrain modeling can be derived from a terrain database stored in memory.

[0049] The step of determining a height of the aircraft relative to the area flown over can alternatively use the focal length of a lens of the image capture device, thanks to adapted processing of the focal length value.

[0050] According to another example compatible with the previous ones, the method may comprise a step of displaying on the display device a safety circle around the symbol. This safety circle represents a safety bubble around the aircraft which must be respected, for example during a landing, no obstacle must interfere with the safety bubble and therefore interfere with the safety circle on the representation of the area flown over.

[0051] The safety circle may be centered on an intersection of the diagonals of a rectangle in which the symbol is inscribed.

[0052] The safety circle can have a variable diameter depending on the height. In this way, the diameter of the safety circle displayed on the representation can be representative of the actual diameter of the safety bubble to be respected around the aircraft.

[0053] The step of displaying the safety circle may in this case include a sub-step of calculation by the computer to calculate the diameter of the safety circle as a function of the height of the aircraft and a diameter of a lifting rotor of the aircraft.

[0054] The diameter of the safety bubble is, for example, equal to twice the diameter of the aircraft's lift rotor. When the symbol includes a shape representing the aircraft structure and at least one rotor circle, and the dimensions of the symbol also vary depending on the height of the aircraft, the diameter of the safety circle is then equal to twice the diameter of the rotor circle.

[0055] The safety circle can be displayed on the display device only when the height is less than or equal to the second threshold. In this way, when the safety circle is displayed, the pilot knows that the aircraft is approaching the overflown area and sees the information on the dimensions of the vertical projection of the safety bubble on the overflown area. The second threshold is, for example, equal to 300 feet (300fts).

[0056] According to another example compatible with the previous ones, the method may comprise a step of displaying on the viewing device markers of the cardinal points, namely the directions of North, South, East and West. These markers are for example displayed near the horizon circle.

[0057] According to another example compatible with the previous ones, the method may comprise a step of displaying on the display device a heading indicator of the aircraft. The heading of the aircraft is aligned with the direction of the roll axis of the aircraft and represented on the representation of the area flown over in front of the aircraft. The heading indicator of the aircraft is for example displayed near the horizon circle.

[0058] According to another example compatible with the previous ones, the method may comprise a step of displaying on the display device an indicator of the wind experienced by the aircraft. This wind indicator carries information on speed and / or wind direction, for example provided by an anemometer or a wind vane of the aircraft.

[0059] The present invention also relates to a system for assisting in piloting an aircraft in flight. The aircraft comprises a structure provided for example with a cell and possibly a tail boom and / or wings, and at least one lift rotor arranged for example above the cell.

[0060] The pilot assistance system for an aircraft in flight includes: an image capture device, a first measuring device for determining an attitude of the aircraft, a second measuring device for determining a height of the aircraft relative to the area flown over, a display device, and a computer.

[0061] This system according to the invention is thus configured for implementing the method for assisting in piloting an aircraft in flight described above. This system can be installed on an aircraft at the time of its manufacture or can be added to an aircraft already in service in order to improve its safety and allow the pilot to easily and completely view a landing area and its environment.

[0062] The image capture device may comprise at least one camera or at least one photographic apparatus. For example, the image capture device may comprise a single camera or at least one photographic apparatus provided with a lens covering an angular field of 360° in a plane perpendicular to an optical axis of the camera or photographic apparatus and at least 180° in a vertical plane parallel to this optical axis. The second reference point of the image capture device is the center of the lens.

[0063] The invention and its advantages will appear in more detail in the context of the description which follows with examples of embodiment given for illustrative purposes with reference to the appended figures which represent: there figure 1 , an aircraft equipped with an aircraft piloting assistance system according to the invention, the figure 2 , a block diagram of a method for assisting in piloting an aircraft according to the invention, the figure 3 , a view of the aircraft and the area flown over, the figure 4 , images of the representation of the area flown over on an aircraft display device, the Figure 5 , images of the representation of the area flown over on a display device of the aircraft, and the figure 6 , images of the representation of the area flown over on an aircraft display device.

[0064] Elements present in several distinct figures are assigned a single reference.

[0065] There figure 1 represents a rotary-wing aircraft 1 equipped with a system 10 for assisting in piloting the aircraft 1 in flight. The aircraft 1 comprises, for example, a structure 2. The structure 2 may be equipped with a cell 4 and a tail boom 5 as well as at least one lift rotor 3 arranged, for example, above the cell 4. Other configurations of aircraft 1 are conceivable within the scope of the present invention, the structure 2 being able, for example, to comprise wings.

[0066] The system 10 comprises an image capture device 11 carried by the structure 2 and directed towards the ground, a first measuring device 16 for determining an attitude of the aircraft 1, a second measuring device 17 for determining a height of the aircraft 1 relative to the area flown over, a display device 15 and a computer 13.

[0067] According to the example of the figure 1, the image capture device 11 is positioned vertically above a center of rotation 35 of the lift rotor 3 when the aircraft 1 has a zero attitude, a vertical direction being parallel to the direction of Earth's gravity. But the capture device 11 can alternatively be positioned at another position under, or even in, the cell 4, or under or in the tail boom 5, or even under or in wings of the structure 2. The viewing device 15 is positioned in the cell 4 in a location visible to a pilot of the aircraft 1.

[0068] The display device 15 may comprise a screen. The display device 15 may alternatively comprise a portion of the windshield of the aircraft 1 or a digital tablet on board the aircraft 1, or any other display means.

[0069] The aircraft 1 may also include an anemometer 18 or a wind vane in order to determine a direction and / or a speed of the wind experienced by the aircraft 1.

[0070] The computer 13 may comprise one or more processing units each having, for example, at least one processor and at least one memory 12, 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. The computer 13 communicates, by a wired link or a wireless link, with the first and second measuring devices 16, 17, the image capture device 11, the memory 12 and the display device 15 as well as possibly with the anemometer 18 or the wind vane.

[0071] The system 10 for assisting with piloting the aircraft 1 in flight may also include a memory 19, communicating with the computer 13.

[0072] The system 10 for assisting the piloting of the aircraft 1 in flight is configured to implement a method for assisting the piloting of the aircraft 1 in flight, a block diagram of which is shown in the figure 2 . A memory 12, 19 may comprise a code or a code segment applied by the computer 13 for carrying out this method. This method comprises the following steps.

[0073] First, a determination step 110 for determining an attitude of the aircraft 1 is carried out using the first measuring device 16. For this purpose, the first measuring device 16 may comprise at least one inertial unit or a device AHRS.The first measuring device 16 then transmits a signal, for example analog or digital, electrical or optical, to the computer 13, this signal carrying information relating to the attitude of the aircraft 1.

[0074] The attitude of aircraft 1 is defined by a roll angle and a pitch angle of aircraft 1 around a roll axis and a pitch axis of aircraft 1 respectively.

[0075] The method comprises a determination step 120 for determining a height of the aircraft 1 relative to the overflown area is carried out using the second measuring device 17, this height being equal to the distance between the aircraft 1 and the overflown area defined parallel to the direction of Earth's gravity. The second measuring device 17 then transmits a signal, for example analog or digital, electrical or optical, to the computer 13, this signal carrying information relating to the height of the aircraft 1.

[0076] For this purpose, the second measuring device 17 may for example comprise a radiosonde directly measuring this height of the aircraft 1 relative to the area flown over, in a vertical direction, parallel to the direction of Earth's gravity.

[0077] According to another example, the second measuring device 17 may comprise a barometric altimeter making it possible to measure a current atmospheric pressure. The determination step 120 may then comprise a sub-step 123 of measuring a current atmospheric pressure around the aircraft 1 carried out using the barometric altimeter. Then, a calculation sub-step 124 is carried out by the computer 13 or a processing unit of the second measuring device 17 in order to determine the height of the aircraft 1 by comparing the current atmospheric pressure with an atmospheric pressure at the altitude of the area flown over, this atmospheric pressure at the altitude of the area flown over having been previously stored in a memory of the aircraft 1, for example following a parameter setting using an interface of the aircraft 1.

[0078] According to another example, the second measuring device 17 may comprise a receiver of a satellite positioning system. The determination step 120 may then comprise a determination sub-step 125 for determining a position of the aircraft 1 in a terrestrial reference frame carried out using the receiver of the satellite positioning system. Then, a calculation sub-step 126 for calculating the height of the aircraft 1 relative to the area flown over is carried out by the computer 13 or another processing unit using the position of the aircraft 1 in the terrestrial reference frame and a three-dimensional terrain model or a stored terrain database.

[0079] The three-dimensional terrain modeling or terrain database may be stored in the memory 12, 19 or in an additional memory integrated for example in the system 10 or in the second measuring device 17.

[0080] According to another example, the determination step 120 can use the focal length of a lens of the camera or photographic apparatus of the image capture device 11 to determine the height of the aircraft 1 relative to the area flown over, using for example an adapted processing of this focal length.

[0081] The method comprises a capture step 130 for capturing at least one image of the area flown over, also using the image capture device 11. The image capture device 11 then transmits a signal, for example analog or digital, electrical or optical, to the computer 13, this signal carrying information relating to at least one captured image of the area flown over.

[0082] For this purpose, the image capture device 11 may comprise a single camera or a single photographic apparatus fixed relative to the structure 2, as shown in the figure 1For example, the image capture device 11 covers an angular field of 360° in a horizontal plane and an angular field of at least 180° in a vertical plane.

[0083] The image capture device 11 may alternatively comprise a single camera or a single photographic device movable relative to the structure 2. The camera or photographic device then moves in a rotational movement relative to a support secured to the structure 2, for example in order to cover an angular field of 360° in a horizontal plane and an angular field of at least 180° in a vertical plane.

[0084] The image capture device 11 may alternatively comprise several cameras or several photographic devices fixed relative to the structure 2 and jointly covering, for example, an angular field of 360° in a horizontal plane and an angular field of at least 180° in a vertical plane.

[0085] The determination steps 110, 120 and 130 can be carried out sequentially as shown or in parallel, i.e. substantially simultaneously.

[0086] The method comprises a display step 140 for displaying on the display device 15 a representation 20, as illustrated in figures 4 to 6 of the area flown over. The computer 13 then transmits a signal, for example analog or digital, electrical or optical, to the display device 15 to display the representation 20, this signal carrying information relating to the representation 20.

[0087] The representation 20 of the area flown over covers for example an angular field of 360° in a horizontal plane and at least 180° in a vertical plane when the attitude of the aircraft 1 is zero, the vertical plane being parallel to a direction of Earth's gravity and the horizontal plane being perpendicular to the direction of Earth's gravity. According to the examples represented on the figures 4 to 6 , the representation 20 covers an angular field of 360° in a horizontal plane and at least 220° in a vertical plane when the attitude of the aircraft 1 is zero.

[0088] The representation 20 is formed by each image captured successively by the image capture device 11 when it comprises a single camera or a single photographic device fixed relative to the structure 2.

[0089] When the image capture device 11 comprises either a single camera or a single photographic device that is mobile relative to the structure 2, or several cameras or several photographic devices that are fixed relative to the structure 2, the computer 13 then constructs the representation 20 from the images captured by the camera(s) or the photographic device(s) and transmitted to the computer 13, so as to form a single image of the area flown over covering the required angular field. The display step 140 then comprises a complementary step 145 of constructing the representation 20 from the images captured by the camera(s) or the photographic device(s), this complementary step 145 of constructing the representation 20 from the images captured by the camera(s) or the photographic device(s), this complementary step 145 of constructing being carried out for example by the computer 13 or another processing unit.

[0090] This representation 20 allows a pilot of the aircraft 1 to have a complete view of the area flown over located below the aircraft 1.

[0091] The method comprises a calculation step 150 for calculating a first position 33 on the representation 20 of a vertical projection onto the overflown area of ​​a first reference point 31 of the aircraft 1 produced using the computer 13, as a function of the attitude of the aircraft 1 and the height of the aircraft 1 relative to the overflown area. The vertical projection of the first reference point 31 onto the overflown area is carried out parallel to the direction of Earth's gravity. For this purpose, after having received the information relating to the attitude and the height of the aircraft 1, and knowing the relative positions of the first and second reference points 31, 111, the computer 13 determines the first position 33 on the representation 20 using a stored law, a table of values ​​or others. Optionally, the computer 13 stores this first position 33 in a memory 12, 19.The computer 13 can thus determine and store the first successive positions 33 during a flight of the aircraft 1.

[0092] The method comprises a calculation step 160 for calculating a second position 113 on the representation 20 of a vertical projection onto the overflown area of ​​a second reference point 111 of the image capture device 11 produced using the computer 13, as a function of the attitude of the aircraft 1. The vertical projection of the second reference point 111 onto the overflown area is carried out parallel to the direction of Earth's gravity. For this purpose, after having received the information relating to the attitude, the computer 13 determines, using a stored law, a table of values ​​or others, the second position 113 on the representation 20, and optionally stores this second position 113 in a memory 12, 19. The computer 13 can thus determine and store the successive second positions 113 during a flight of the aircraft 1.

[0093] The stored law or the table of values ​​may for example involve a parameter of the image capture device 11 such as the focal length of the lens of the image capture device. The distance between the second position and the center of an image captured by the image capture device 11 is for example equal to the product of a coefficient depending on this parameter of the image capture device multiplied by the attitude angle of the aircraft in the case of an equidistant projection. This distance is for example equal to the product of a coefficient depending on this parameter of the image capture device multiplied by the sine of the attitude angle of the aircraft in the case of an equisolid projection.

[0094] The first reference point 31 and the second reference point 111 are specific points respectively of the aircraft 1 and of the image capture device 11. The reference point 31 is for example a center of rotation 35 of the lift rotor 3 of the aircraft 1 and the second reference point 111 is for example the center of the lens of the camera or of the photographic apparatus of the image capture device 11 as shown in the figure 3 ,.

[0095] There figure 3 represents the first and second positions 33,113 defined by vertical projection of the first and second reference points 31,111 onto the representation 20.

[0096] Then, a display step 170 for displaying on the display device 15 a symbol 21 representing the aircraft 1 is carried out, a point of origin of the symbol 21 being positioned on the first position 31. The computer 13 then transmits a signal, for example analog or digital, electrical or optical, to the display device 15 to display the symbol 21, this signal carrying information relating to the symbol 21 and to the first position 33. figures 4 to 6 represent the display of the symbol 21 positioned in the first position 33 on the display device 15 superimposed on the representation 20 of the area flown over.

[0097] Thus, the pilot of the aircraft 1 can view the symbol 21 on the representation 20 and, consequently, on the area flown over in order in particular to anticipate and prepare for a landing by having a vision of the aircraft in relation to the area flown over, to a potential landing area and to possible obstacles.

[0098] The symbol 21 can be represented on the display device 15 with constant dimensions regardless of the height of the aircraft 1.

[0099] The symbol 21 can alternatively be represented on the display device 15 with variable dimensions depending on this height of the aircraft 1. The method then comprises an additional calculation step 165 to calculate, using the calculator 13 and a stored law, a table of values ​​or others, the dimensions of the symbol 21 depending on the height of the aircraft 1. The dimensions of the symbol 21 can for example correspond, on the representation 20 to the dimensions of the vertical projection of the aircraft 1 on the area flown over. The calculator 13 then transmits to the display device 15 a signal, for example analog or digital, electrical or optical, carrying information relating to the dimensions of the symbol 21.

[0100] In this case, the additional calculation step 165 takes into account the scale used for displaying the area flown over on the representation 20. This scale may for example be a function of a focal length of the camera(s) or photographic apparatus of the image capture device 11 and possibly of a coefficient applied by the calculator 13 for displaying the representation 20 on the viewing device 15.

[0101] The symbol 21 can take various forms, such as a cross, a circle. The point of origin of the symbol 21 can for example be the center of the symbol 21.

[0102] The symbol 21 can alternatively take the form of an aircraft seen from above and include in particular a rotor circle 213 representing the lift rotor 3 and a shape 212 representing the structure 2 as shown in the figures 5 And 6 . The point of origin of symbol 21 can in this case be the center of rotor circle 213.

[0103] During the additional calculation step 165, the computer 13 determines the dimensions of the symbol 21, for example the dimensional characteristics of the rotor circle 213 and of the shape 212 using a stored law, a table of values ​​or others as a function respectively of a diameter of the lift rotor 3 and the dimensions of the structure 2 as well as the height of the aircraft 1. The computer 13 then transmits to the display device 15 a signal, for example analog or digital, electrical or optical, carrying information relating to the dimensions of the symbol 21.

[0104] The symbol 21 can alternatively be represented on the display device 15 with constant dimensions when the height of the aircraft 1 is greater than this first threshold and the symbol 21 can be represented on the display device 15 with variable dimensions depending on this height, as previously mentioned, when the height is less than or equal to the first threshold. For this purpose, the computer 13 compares the height to the first threshold.Therefore, if the height is greater than this first threshold, the computer 13 transmits to the display device 15 a signal carrying information relating to constant dimensions of the symbol 21 and to the first position 31 and if when the height is less than or equal to the first threshold, the computer 13 calculates the dimensions of the symbol 21 in particular as a function of this height and transmits to the display device 15 a signal carrying information relating to these dimensions of the symbol 21 and to the first position 31.

[0105] The additional calculation step 165 is therefore carried out as a function of the height of the aircraft 1 and the first threshold, namely when the height is less than or equal to the first threshold. Consequently, the symbol 21 representing the dimensions of the vertical projection of the aircraft 1 on the area flown over when the aircraft 1 is displayed when the aircraft 1 is located close to the area flown over, namely at a height less than or equal to the first threshold, in order to assist the pilot during these maneuvers.

[0106] In addition, the first threshold may be a hysteresis threshold and as such include a first low threshold and a first high threshold. The symbol 21 is then represented with constant dimensions when the height is greater than the first high threshold and the symbol 21 is represented with variable dimensions when the height is less than or equal to the first low threshold. In addition, when the height is between the first high threshold and the first low threshold, the way of displaying the symbol, namely with constant or variable dimensions, is not modified.

[0107] Furthermore, the method comprises a display step 180 for displaying on the viewing device 15 a horizon circle 25 representing a horizon line. The horizon circle 25 represents the projection of the horizon line around the aircraft 1. The horizon circle 25 is displayed with a constant diameter value, independently of the height and attitude of the aircraft 1. The horizon circle 25 is always centered on the second position 113. The second position 113 may therefore move on the representation 20 when the attitude of the aircraft 1 varies and the horizon circle 25 may then not appear entirely on the representation 20, in particular when the roll angle and / or the pitch angle of the aircraft 1 is large.For this purpose, the computer 13 transmits to the display device 15 a signal, for example analog or digital, electrical or optical, carrying information relating to the dimensions of the horizon circle 25 and to the second position 113.

[0108] According to the aircraft example 1 shown in the figure 1, the image capture device 11 comprises a single camera positioned vertically above the center of rotation 35 of the lift rotor 3 when the aircraft 1 has a zero attitude, its roll and pitch angles being equal to zero. An optical axis 117 of the image capture device 11 is vertical when the aircraft 1 has a zero attitude. The first reference point 31 and the second reference point 111 are in fact located on this optical axis 117. Consequently, the first position 33 and the second position 113 are displayed together and positioned at the center of the representation 20 when the aircraft 1 has a zero attitude as shown in the figures 3 And 4 . In this case, the horizon circle 25 and the symbol 21 are at the first position 33 and the second position 113 and therefore positioned at the center of the representation 20.

[0109] On the figure 6, the first position 33 and the second position 113 are distinct and the horizon circle 25 is eccentric relative to the representation 20. Such a configuration may be the consequence of the use of an image capture device 11 comprising for example a single camera offset longitudinally from the vertical of the center of rotation 35 of the lift rotor 3. Such a camera may for example be positioned under the tail boom 5 according to the aircraft example 1 represented on the figure 3 .

[0110] This can alternatively be the consequence of a non-zero attitude of aircraft 1. In the case of the figure 6 , these two possible reasons are combined. We note in fact that aircraft 1 has a non-zero attitude, the distribution of the sky around the ground on representation 20 not being uniform.

[0111] Thanks to the method according to the invention, the pilot of the aircraft 1 can visualize on the representation 20 the projection of the horizon line around the aircraft 1 in order to facilitate his vision of the zone flown over and of the potential landing area as well as of the obstacles, in particular the obstacles in height situated above the horizon circle 25. The pilot of the aircraft 1 can also, thanks to the position of the horizon circle 25 and to his possible movements on the representation 20, have a vision of the changes in attitude of the aircraft 1.

[0112] For a representation 20 covering an angular field of 220° in a vertical plane and produced with an equidistant projection, the horizon circle 25 is for example displayed on a viewing device 15 having dimensions of 150mm x 150mm with a diameter equal to 123mm.

[0113] Furthermore, the method may comprise a display step 190 for displaying on the display device 15 a safety circle 26 around the symbol 21. The safety circle 26 is for example centered on an intersection 263 of the diagonals of a rectangle 265 in which the symbol 21 is inscribed. The computer 13 then transmits to the display device 15 a signal carrying information, for example analog or digital, electrical or optical, relating to the dimensions of the safety circle 26 and its position around the symbol 21.

[0114] This safety circle 26 allows the pilot to visualize a safety bubble around the aircraft 1 in which no obstacle in the area flown over must be located in order to carry out, for example, a safe landing.

[0115] The safety circle 26 can be displayed on the representation 20 only when the height of the aircraft 1 is less than or equal to a second threshold. The pilot thus knows when the safety circle 26 is displayed that he has reached a height less than or equal to the second threshold. For this purpose, the computer 13 compares the height to the second threshold. Therefore, if the height is greater than this second threshold, the computer 13 does not transmit to the display device 15 any signal relating to the safety circle 26 and if the height is less than or equal to the second threshold, the computer 13 transmits to the display device 15 a signal carrying information relating to the safety circle 26 and its position.

[0116] The diameter of the safety circle 26 can also be variable as a function of this height. The display step 190 of the safety circle 26 then comprises a calculation sub-step 195 for calculating, using the computer 13, the diameter of the safety circle 26 as a function of the height of the aircraft 1 and a diameter of a lift rotor 3. The computer 13 then calculates the dimensions of the safety circle 26 as a function in particular of this height and the diameter of a lift rotor 3, then transmits to the display device 15 a signal carrying information relating to these dimensions of the safety circle 26 and its position.

[0117] The method may also comprise a display step 200 for displaying on the viewing device 15 markers 27 of the cardinal points. These markers 27 are for example lines attached to the horizon circle 25 respectively indicating the directions of North, South, East and West as indicated on the figures 4 to 6 .

[0118] The positions of these markers are for example determined using the first measuring device 16 comprising for example at least one inertial unit or a device AHRS. The computer 13 receives from the first or second measuring device 16, 17 a signal carrying information relating to the directions of the cardinal points, then transmits to the display device 15 a signal carrying information relating to the positions of the markers 27 on the representation 20.

[0119] The positions of these markers can also be determined according to another example using another measuring device, such as a compass or a compass determining the direction of magnetic North. The computer 13 receives a signal carrying information relating to this direction of magnetic North and adds to it the magnetic declination relating to the position of the aircraft 1 in order to determine the direction of geographic North and to deduce therefrom the positions of the other cardinal points.

[0120] The values ​​of the magnetic declinations relating to the different positions of the aircraft 1 are for example stored in a memory 12, 19. The computer 13 can then transmit to the display device 15 a signal carrying information relating to the positions of the markers 27 on the representation 20. The magnetic declination relating to the position of the aircraft 1 can also be determined using the second measuring device 17 comprising for example a receiver of a satellite location system which determines an absolute position of the aircraft 1 from which the magnetic declination can be deduced.

[0121] The method may also comprise a display step 210 for displaying on the display device 15 a heading indicator 28 of the aircraft 1. The heading indicator 28 is for example a line attached to the horizon circle 25, towards the front of the aircraft 1 and aligned with the direction of the roll axis of the aircraft 1. Additional indicators 29 may also be attached to the horizon circle 25 respectively on the sides and the rear of the aircraft 1, as shown in the figures 4 to 6 , in order to indicate to the pilot the directions to the right, left and rear of the aircraft 1. The computer 13 transmits to the display device 15 a signal carrying information relating to the heading indicator 28 and the additional indicators 29.

[0122] The method may also comprise a display step 220 for displaying on the display device 15 a wind indicator 24 experienced by the aircraft 1. This display step 210 uses information provided by the anemometer 18 or the wind vane to display on the display device 15 a wind indicator 24 indicating the direction of the wind experienced by the aircraft 1 as shown in the Figure 5 and / or a value of the wind speed. The computer 13 receives from the anemometer 18 or the wind vane a signal carrying information relating to the direction and / or speed of the wind, then transmits to the display device 15 a signal carrying information relating to the wind indicator 24.

Claims

1. Method to assist with piloting an aircraft (1) in flight, said aircraft (1) comprising: - a structure (2), - an image capture device (11), - a first measuring device (16) for determining an attitude of said aircraft (1), - a second measuring device (17) for determining a height of said aircraft (1) with respect to an area overflown by said aircraft (1), - a display device (15), and - a computer (13), said method comprising the following steps: - determining (110) an attitude of said aircraft (1) with said first measuring device (16), - determining (120) a height of said aircraft (1) with respect to said overflown area with said second measuring device (17), - capturing (130) at least one image of said overflown area with said image capture device (11), - displaying (140) on the display device (15) a representation (20) of said overflown area, said representation (20) comprising said at least one image, - calculating (150), by means of said computer (13), a first position (33) on said representation (20) of a vertical projection on said overflown area of a first reference point (31) of said aircraft (1) as a function of said attitude and said height, displaying (170) on said display device (15) a symbol (21) representing said aircraft (1), a point of origin of said symbol (21) being positioned at said first position (33), characterised in that said method further comprises the following steps: - calculating (160), by means of said computer (13), a second position (113) on said representation (20) of a vertical projection on said overflown area of a second reference point (111) of said image capture device (11) as a function of said attitude, - displaying (180) on said display device (15) a horizon circle (25) representing a horizon line, said horizon circle (25) being centred on said second position (113), said diameter of said horizon circle (25) being constant.

2. Method according to claim 1, characterised in that said symbol (21) is represented on said display device (15) with different shapes when said height is greater than a first threshold and when said height is less than or equal to said first threshold.

3. Method according to any one of claims 1 to 2, characterised in that said symbol (21) is represented on said display device (15) with dimensions that vary as a function of said height.

4. Method according to any one of claims 1 to 2, characterised in that said symbol (21) is represented on said display device (15) with constant dimensions when said height is greater than a first threshold and said symbol (21) is represented on said display device (15) with dimensions that vary as a function of said height when said height is less than or equal to said first threshold.

5. Method according to any one of claims 3 to 4, characterised in that said method comprises an additional step of calculating (165), by means of said computer, said dimensions of said symbol (21) at least as a function of said height.

6. Method according to claim 5, characterised in that said aircraft (1) comprising at least one lift rotor (3), said symbol (21) comprises a shape (212) representing said structure (2) and at least one rotor circle (213) corresponding to said at least one lift rotor (3) and said dimensions of said symbol (21) comprises dimensional characteristics of said shape (212) and of said at least one rotor circle (213), and during said additional step of calculating (165), said computer (13) calculates said dimensional characteristics of said shape (212) and of said at least one rotor circle (213) as a function respectively of a diameter of said at least one lift rotor (3) and of the dimensional characteristics of said structure (4) as well as of said height.

7. Method according to any one of claims 1 to 6, characterised in that said aircraft (1) comprising at least one lift rotor (3), said first reference point (31) is a centre of rotation of a lift rotor (3) among said at least one lift rotor (3).

8. Method according to any one of claims 1 to 7, characterised in that said method comprises a step of displaying (190) on said display device (15) a safety circle (26) around said symbol (21) when said height is less than or equal to a second threshold, a diameter of said safety circle (26) being variable as a function of said height.

9. Method according to claim 8, characterised in that said safety circle (26) is centred on an intersection of the diagonals of a rectangle (265) in which said symbol (21) is depicted.

10. Method according to any one of claims 8 to 9, characterised in that said step of displaying (190) said safety circle (26) comprises a substep of calculating (195) said diameter of said safety circle (26) as a function of said height and of a diameter of a lift rotor (3) of said aircraft (1).

11. Method according to any one of claims 1 to 10, characterised in that said method comprises a step of displaying (200) on said display device (15) markings (27) of the cardinal points and a step of displaying (210) on said display device (15) a heading indicator (28) indicating the heading of said aircraft (1).

12. Method according to any one of claims 1 to 11, characterised in that said method comprises a step of displaying (220) on said display device (15) a wind indicator (24) indicating the wind encountered by said aircraft (1).

13. Method according to any one of claims 1 to 12, characterised in that said representation (20) of the said overflown area covers an angular field of 360° in a horizontal plane and of at least 180° in a vertical plane when said attitude of said aircraft (1) is zero, said vertical plane being parallel to a direction of Earth's gravity and said horizontal plane being perpendicular to said direction of Earth's gravity.

14. Method according to any one of claims 1 to 13, characterised in that said image capture device (11) comprises a single camera or a single photographic device equipped with a lens covering an angular field of 360° in a plane perpendicular to an optical axis (117) of said camera or said photographic device and of at least 180° in a vertical plane parallel to said optical axis (117), said second reference point (111) being the centre of said lens, said optical axis (117) being parallel to a direction of Earth's gravity when said aircraft (1) has a zero attitude.

15. System (10) to assist with piloting an aircraft (1) in flight, said aircraft (1) comprising a structure (2), said system (10) comprising: - an image capture device (11), - a first measuring device (16) for measuring an attitude of said aircraft (1), - a second measuring device (17) for measuring a height of said aircraft (1) with respect to an overflown area, - a display device (15), and - a computer (13), characterised in that said system (10) is configured to implement the method according to any one of claims 1 to 14.

16. System (10) according to claim 15, characterised in that said image capture device (11) comprises a single camera or a single photographic device equipped with a lens covering an angular field of 360° in a plane perpendicular to an optical axis (117) of said camera or said photographic device and of at least 180° in a vertical plane parallel to said optical axis (117), said second reference point (111) of said image capture device (11) being the centre of said lens.