System for guiding an aircraft and associated guiding method

Abstract

The present invention relates to a system (10) for guiding an aircraft, comprising: - an imaging chain (14) configured to reconstruct an image of the external environment; - a monitoring chain (16) configured to detect obstacles in the path of the aircraft; - a radar module (12); - a management module (31) configured to control the radar module (12) between a monitoring operation mode and a hybrid operation mode; - a post-processing module (32) configured to process reflected waves in order to transmit signals corresponding to the imaging waves to the imaging chain (14) and / or transmit signals corresponding to the monitoring waves to the monitoring chain (16).

Description

Technical Field

[0001] This invention relates to a system for guiding an aircraft. The invention also relates to a guidance method associated with the guidance system.

[0002] The field of this invention is avionics system architecture, particularly for approach and landing assistance operations. Background Technology

[0003] The descent of an aircraft as it approaches the runway is a critical phase of flight, especially in low-visibility conditions such as fog or rain. The main challenge here is ensuring sufficient runway visibility to allow the descent to continue and then initiate the landing.

[0004] In addition to runway visibility issues, reduced visibility also poses a risk of collisions with non-cooperative obstacles such as drones, large birds, cranes, towers, etc. This risk is increasing with the proliferation of drones.

[0005] Therefore, the challenge lies in providing enhanced visibility of the runway and its surroundings under reduced visibility conditions, while also providing detection of potential collisions with obstacles during descent.

[0006] To address this issue, enhanced flight vision systems (EFVS) based on sensors mounted on the aircraft (typically infrared or multispectral sensors) are known in the prior art. These sensors enable the provision of better runway images to the flight crew than what natural vision would provide under certain adverse weather conditions.

[0007] Therefore, the system enables aircraft to continue landing in adverse conditions such as fog, and thus reduces clearance and turning in adverse weather conditions.

[0008] During the approach, the crew therefore decides at a decision altitude whether to continue the landing. Specifically, if a visual reference (corresponding to runway lights or runway markings) is present in the sensor imagery and not present in natural vision, the crew is authorized to continue the approach below that altitude. Depending on the capabilities of the vision system, the approach can continue down to 100 feet above ground, corresponding to the altitude at which the crew must see a runway reference in natural vision to complete the landing. Some vision systems also allow the aircraft to be guided down to the ground without a runway reference in natural vision. In this case, it is not EFVS.

[0009] According to existing technology, some instruments also allow aircraft to separate from surrounding traffic during approach. These instruments can be implemented by air traffic control or crew members in uncontrolled areas. Furthermore, in the case of cooperative traffic, avoidance is possible through onboard TCAS (Traffic Collision Avoidance System) systems based on deterministic algorithms or dialogue between the devices of two aircraft.

[0010] In any situation, crew members must apply the basic rule of "detection and avoidance" as much as possible in order to protect themselves from collisions with non-cooperative traffic.

[0011] Typically, the process of detecting and identifying cooperative or non-cooperative traffic is kept in a delicate phase. Once a threat is detected, the crew must assess trajectory convergence and decide whether evasive maneuvers are necessary.

[0012] This maneuver must rely primarily on the rules of the field (that aircraft coming from the right and below have priority on the final approach) and will assume that the other aircraft will follow the same rules, i.e., its trajectory will remain unchanged.

[0013] However, these assumptions no longer hold true in the case of non-cooperative transportation (especially drones).

[0014] There is also the issue of ground collisions with parked or taxiing vehicles or aircraft. The detection of obstacles on runways or taxiways currently remains the responsibility of the flight crew. In low-visibility conditions, this can rely solely on the assurance that other airport users are properly adhering to procedures and that air traffic control can detect intruders in a timely manner.

[0015] The problem of detecting potential collisions with non-cooperative traffic is currently being addressed through research into detection and avoidance applications using X-band or Ku-band radar sensors to detect non-cooperative traffic under all weather conditions. However, these radars are not designed to provide accurate imagery of landing runways due to their low angular resolution. The lack of space and the high cost of radar sensors have deprived many aircraft of these additional capabilities.

[0016] Therefore, there is currently no solution that allows for the simultaneous provision of emergency collision detection and avoidance functions with all-weather landing assistance. Consequently, these two functions are implemented by different instruments independently, making it impossible to coordinate their actions. Therefore, the need to monitor individual instruments increases the cognitive load on the crew during landing or during any other critical phase of flight. Summary of the Invention

[0017] The purpose of this invention is to address these problems, and in particular to propose a system for guiding aircraft that reduces the cognitive load required by the crew during landing or during any other critical phase of flight. Specifically, this guidance system combines the enhanced visibility of the landing runway with the ability to detect cooperative or non-cooperative obstacles during this phase.

[0018] Therefore, the present invention relates to a system for guiding an aircraft, comprising:

[0019] - An imaging chain, which is configured to reconstruct an image of the external environment;

[0020] - A monitoring chain, configured to detect obstacles in the flight path;

[0021] - A radar module that can transmit millimeter waves and receive reflected waves;

[0022] - A management module configured to control the radar module between a monitoring operation mode and a hybrid operation mode, wherein the monitoring operation mode includes transmitting only monitoring waves, and the hybrid operation mode includes transmitting a hybrid wave combining monitoring waves and imaging waves;

[0023] - A post-processing module configured to process the reflected wave in order to transmit the signal corresponding to the imaging wave to the imaging chain and / or transmit the signal corresponding to the monitoring wave to the monitoring chain.

[0024] According to other advantageous aspects of the invention, the guiding system includes one or more of the following features, either individually or in all technically possible combinations:

[0025] - The management module is configured to determine the imaging space covered by the imaging wave and the monitoring space covered by the monitoring wave;

[0026] The monitoring space is defined by an aperture angle that is wider than the imaging space or equal to the aperture angle of the imaging space;

[0027] A public space, defined by the intersection of the monitoring space and the imaging space;

[0028] Advantageously, the imaging space is defined by a longer range than the monitoring space;

[0029] - The monitoring space is determined based on the aircraft's speed, its altitude, and assumptions about potential obstacles along its path;

[0030] - The imaging space is determined based on the aircraft's altitude and its trajectory relative to the landing runway;

[0031] - The monitoring wave includes a surveillance wave and a confirmation wave. The surveillance wave is periodically sent into the monitoring space to detect possible obstacles on the aircraft's path, and the confirmation wave is sent toward the possible obstacle detected by the surveillance wave to confirm or eliminate the obstacle.

[0032] -The management module is configured to switch the radar module to the hybrid operation mode when the confirmation wave detects terrain and / or landing runway;

[0033] - The management module is configured to periodically send the confirmation wave to the terrain;

[0034] - The management module is configured to switch the radar module to the hybrid operation mode or the monitoring operation mode by comparing the altitude of the aircraft with a predetermined threshold;

[0035] - The predetermined threshold is between 400 feet and 600 feet, and advantageously, it is essentially equal to 500 feet;

[0036] The monitoring chain includes a processing module configured to determine a collision trajectory with a potential obstacle detected by the monitoring wave.

[0037] The present invention also relates to a method for guiding an aircraft, the method being implemented by the system as defined above and comprising the following steps:

[0038] - Only monitoring waves are emitted in the monitoring operation mode;

[0039] -Emit hybrid waves in the hybrid operation mode;

[0040] - Receive and process the reflected wave in order to transmit a signal corresponding to the imaging wave to the imaging chain or a signal corresponding to the monitoring wave to the monitoring chain. Attached Figure Description

[0041] The invention will become clearer after reading the following description, which is given by way of non-limiting example only and with reference to the accompanying drawings, wherein:

[0042] -[ Figure 1 ] Figure 1 This is a schematic diagram of the guiding system according to the present invention;

[0043] -[ Figure 2 ] Figure 2 This is a flowchart of a booting method according to the present invention, which is composed of... Figure 1 The implementation of the guidance system;

[0044] -[ Figure 3 ] [ Figure 4 ] [ Figure 5 ] [ Figure 6 ] Figures 3 to 6 yes Figure 2 Different illustrations of the implementation methods of the guidance method. Detailed Implementation

[0045] Figure 1 A boot system 10 according to the present invention is shown.

[0046] The guidance system 10 can be used to guide aircraft, especially during their landing phase (or approach phase).

[0047] According to other embodiments and depending on the nature of the aircraft, the guidance system 10 according to the invention can be used in any other phase of flight involving the use of enhanced vision, particularly terrain.

[0048] In the remainder of the instruction manual, aircraft is understood to mean any flying machine that can be at least partially manually operated by an operator or pilot or that can be autonomously operated.

[0049] The aircraft may specifically correspond to an airplane, specifically a passenger plane, or to a helicopter capable of being piloted by one or more pilots from their cockpit. According to other embodiments, the aircraft is a drone, for example, capable of being remotely piloted by an operator from a remote cockpit. According to yet another embodiment, the aircraft is a drone capable of at least partial autonomous flight.

[0050] According to various examples, the guidance system 10 according to the invention may be at least partially mounted on an aircraft, or at least partially disposed on the ground or in another aircraft.

[0051] exist Figure 1 In the example, the guidance system 10 is fully installed on the aircraft that performs the guidance function.

[0052] refer to Figure 1 The guidance system 10 includes a radar module 12, an imaging chain 14, and a monitoring chain 16.

[0053] Radar module 12 specifically includes millimeter radars configured to transmit millimeter waves and receive reflected waves in response to these millimeter waves. For example, radar module 12 includes a single millimeter radar. Alternatively, the radar module includes multiple millimeter radars configured to transmit and receive waves in groups.

[0054] One or each radar of radar module 12 is advantageously arranged on the fuselage of the aircraft, for example oriented toward its direction of flight. In the case of an aircraft, the radar may be arranged, for example, in a fixed manner. In the case of, for example, a helicopter, the radar may be arranged in a rotating manner.

[0055] As will be explained in more detail below, imaging chain 14 enables enhanced terrain vision to be provided to the aircraft crew, particularly, for example, vision of the aircraft's landing runway.

[0056] For this purpose, imaging chain 14 can be connected to database 22, for example, to provide symbols representing different objects on the terrain, such as landing runways.

[0057] Imaging chain 14 specifically includes an enhanced vision display 21, which allows the crew to view the terrain. This display 21 can be a conventional screen or any other display, such as a head-up display or even a helmet worn by the pilot.

[0058] The monitoring chain 16 enables the monitoring of the area around the aircraft to detect potential obstacles and, advantageously, propose an avoidance trajectory or calculate a predicted trajectory for the detected obstacles.

[0059] For this purpose, monitoring chain 16 can be connected to various avionics systems, such as TAWS (Terrain Awareness and Warning System), TCAS (Traffic Collision Avoidance System), and FW (Flight Warning) system. Monitoring chain 14 can be connected to one or more displays, and in addition, to display potential obstacles and / or alerts to the crew.

[0060] According to the present invention, the two chains 14, 16 enable the use of reflected waves received by the radar module 12 to simultaneously achieve imaging and monitoring functions during different phases of flight.

[0061] For this purpose, the guidance system 10 includes a management module 31, which is shared between the two chains 14 and 16 and is configured to control the radar module 12 between a monitoring operation mode and a hybrid operation mode.

[0062] Specifically, in monitoring operation mode, radar module 12 is configured to emit only monitoring waves, the purpose of which is to monitor the area around the aircraft and may detect obstacles and confirm their presence in the area.

[0063] In other words, the monitoring wave is only used to monitor chain 16.

[0064] Specifically, a "monitoring wave" refers to a wave whose illumination duration in one and the same direction is set to achieve a relatively high detection probability and a relatively moderate false alarm probability. Advantageously, the recurrence frequency of these waves is set to explicitly cover the monitoring field in the range, rather than, or only slightly explicitly cover the monitoring field in terms of Doppler velocity. Furthermore, the Doppler velocity measurement has moderate resolution.

[0065] In hybrid operation mode, radar module 12 is configured to transmit hybrid waves. These hybrid waves combine monitoring waves and imaging waves as described above.

[0066] Specifically, the imaging wave is intended for imaging chain 14 and enables the generation of enhanced views of the terrain, as previously described.

[0067] "Imaging wave" refers to a wave whose illumination duration in a given direction is designed to obtain a specific contrast in the resulting image relative to the thermal noise in the coverage area corresponding to the image to be produced on the ground. Advantageously, the recurrence frequency of these waves is set so as to explicitly cover the imaging area within a range.

[0068] Therefore, each hybrid wave has an interleaving of monitoring and imaging waves. In the common domain (angle / range), this interleaving is performed to obtain waveforms that can be used for both monitoring and imaging. For dedicated domains (e.g., for upward monitoring or for left / right directions not used in imaging), this interleaving is performed so that only the waveform dedicated to monitoring is used. Thus, the overall scan mode interleaves different waveforms in time to cover all needs while considering as much of the common domain as possible.

[0069] In addition, the management module 31 is connected to the device 35, enabling it to provide the aircraft altitude and connect to the crew-operable control element 36.

[0070] The guidance system 10 also includes a post-processing module 32, which is configured to receive and process all reflected waves received by the radar module 12.

[0071] Specifically, the post-processing module 32 enables the conversion of reflected waves into digital signals and the transmission of these signals to the monitoring chain 16 and / or the imaging chain 14.

[0072] Therefore, the signal corresponding to the imaging wave is transmitted to the imaging chain 14 by the post-processing module 32, and the signal corresponding to the monitoring wave is transmitted to the monitoring chain 16.

[0073] The guidance system 10 also includes a processing module 38 integrated into the monitoring chain 16, which enables the determination of collision trajectories with potential obstacles detected by monitoring waves. The module 38 also enables the transmission of information about potential obstacles to connected systems (TAWS, FW, TCAS) and / or displays 23.

[0074] Modules 31, 32, and 38 are implemented using programmable logic circuits, such as FPGAs (Field Programmable Gate Arrays), or at least partially implemented in software. In the latter case, these modules are stored in, for example, a suitable memory and can be executed by one or more processors.

[0075] The guide system 10 according to the invention enables the implementation of what will now be referred to Figure 2 (Show its flowchart) and Figures 3 to 6 The bootstrapping method is explained by showing some of the steps of its implementation.

[0076] It is initially assumed that radar module 12 operates in a monitoring mode. For example, this operating mode of radar module 12 is activated by management module 31 when the aircraft's altitude exceeds a certain threshold. For example, the aircraft's altitude is provided by device 35.

[0077] For example, the threshold is between 400 feet and 600 feet. This threshold is advantageously equal to 500 feet.

[0078] As will be explained in more detail below, in some implementations, the monitoring operation mode remains activated by the management module 31 until the processing module 38 detects the terrain.

[0079] When the guidance system 10 is used during the approach phase of the aircraft, the monitoring operation mode is operational while the aircraft is still relatively far from the landing runway. This distance is precisely determined by an altitude threshold; above this altitude threshold, the management module 31 switches the radar module 12 to a hybrid operation mode.

[0080] In particular, Figure 3 This situation is illustrated in the upper part, where the aircraft's altitude is approximately 5,000 feet, meaning that only the monitoring operation mode is activated.

[0081] During step 110 of the monitoring operation mode MS, the management module 31 commands the radar module 12 to periodically transmit monitoring waves.

[0082] Specifically, the management module 31 determines the monitoring waveform to be transmitted in order to cover... Figure 3 Visible surveillance space V S .

[0083] The monitoring space V S It features a cone-shaped structure oriented toward the direction of the aircraft's movement and extending above and below the horizontal plane containing the aircraft.

[0084] Advantageous and as Figure 3 As can be seen, the cone has a larger angle below the horizontal plane containing the aircraft than above that plane. This is particularly advantageous during the aircraft's approach phase.

[0085] For example, determining the monitoring space V based on known technologies. S .

[0086] Specifically, monitoring space V SThe decision is made by the management module 31 based on the aircraft's speed, its altitude, and assumptions about potential obstacles along the aircraft's path.

[0087] Specifically, these assumptions about obstacles include the vertical and horizontal velocity envelopes of potential obstacles and the minimum RCS (radar cross-section) value. The RCS value corresponds to the "size" of the object seen by the radar. Given the sensitivity of a radar in monitoring operation mode, it will be able to detect an object with a given RCS value at a given distance with a specific probability.

[0088] During the next step 120, the post-processing module 32 receives the reflected waves corresponding to the monitoring waves and converts them into digital signals to send to the processing module 38.

[0089] Then, the processing module 38 analyzes the received signal, and when no obstacle is detected, the processing module 38 commands the management module 31 to continue transmitting the monitoring wave during step 110.

[0090] Conversely, when the processing module 38 detects a possible obstacle by analyzing the signal corresponding to the monitoring wave, it commands the management module 31 to transmit a confirmation wave during the subsequent step 130.

[0091] In particular, the confirmation wave is focused in the direction of a potentially detectable obstacle, which allows power to be concentrated in the target angular sector before confirming or ruling out the presence of such an obstacle.

[0092] Confirmation waves also have a greater detection range than surveillance waves.

[0093] During the subsequent step 140, the post-processing module 32 then receives the reflected waves corresponding to the confirmation waves sent by the radar module 12 and converts these reflected waves into corresponding digital signals. It then sends these signals to the processing module 38, which analyzes them.

[0094] If the presence of an obstacle is not confirmed, the doubt is removed, and then the management module 31 continues to command the radar module 12 to transmit surveillance waves during step 110.

[0095] Conversely, when an obstacle is confirmed, the processing module 38 issues an alarm during step 150.

[0096] Depending on the implementation, the alert can be transmitted to the flight crew and various avionics systems, such as the TCAS system.

[0097] Advantageously, during this step, the processing module 38 determines the collision trajectory with the detected obstacle.

[0098] For this purpose, the processing module 38 can analyze, for example, the speed of the obstacle, the direction of the obstacle's movement, and a number of assumptions.

[0099] The collision trajectory can then be transmitted to the crew and / or avionics systems, such as the TCAS system.

[0100] The operation of MS in monitoring operation mode is also Figure 5 It is shown schematically in the middle.

[0101] Specifically, referring to this figure, radar module 12 transmits surveillance wave S. V Until the processing module 38 detects a possible obstacle B. When this obstacle B is monitored by wave S V Upon detection, radar module 12 is commanded to transmit a confirmation wave S toward obstacle B. C In this case, processing module 38 then analyzes the signal corresponding to the confirmation wave and confirms or rules out the presence of such obstacle B. As previously explained, when such an obstacle is confirmed, processing module 38 can perform specific processes, such as determining a collision trajectory, for example.

[0102] As previously stated, in the opposite case, the processing module 38 continues to analyze the signal corresponding to the monitoring wave SV.

[0103] In some embodiments of the invention, the management module 31 is also configured to periodically send acknowledgment waves S to the terrain. C The surveillance wave did not detect any possible obstacles. This also... Figure 5 As shown in the figure, wave S is confirmed. C It is sent to runway P, which is not detected in advance by the corresponding surveillance wave.

[0104] Then, for example, the confirmation wave S is sent periodically at a predetermined period. C .

[0105] The monitoring operation mode MS is implemented by the guidance system 10 until, during step 160, the management module 31 determines that the aircraft's altitude is below a predetermined threshold, or when the processing module 38 detects the terrain by periodically sending confirmation waves.

[0106] During step 160, management module 31 then switches radar module 12 to hybrid operation mode MM.

[0107] During the initial step 210 of this hybrid operation mode, the management module 31 determines the hybrid waveform, which then optimally combines the monitoring wave and the imaging wave.

[0108] In this hybrid operation mode, the management module 31 not only determines the monitoring space V as described above, S And it is certain Figure 3 Visible imaging space V I .

[0109] like Figure 4 As can be seen, the imaging space V I It also has a cone that extends from the aircraft in its direction of movement.

[0110] With monitoring space V S Different, imaging space V I The aperture angle is smaller than the monitoring space V S However, it is preferably larger than the monitoring space V. S The range.

[0111] In addition, such as in Figure 3 As can be seen, the imaging space V I It can preferably extend only below the horizontal plane including the aircraft, advantageously extending in the direction of the landing runway P. This imaging space V I It can also have a margin in the angular subtraction angle so as to account for the pitch movement of the aircraft without losing the image.

[0112] Imaging space V I It can also be determined based on known technologies, particularly the aircraft's altitude and trajectory relative to the landing runway.

[0113] Imaging space V I and monitoring space V S Having with Figure 3 and Figure 4 Visible public space V C Corresponding intersections.

[0114] In the public space V C In this process, the surveillance wave acts as the imaging wave, which can then be used to enhance vision.

[0115] In public space V C In addition, the wave transmitted by radar module 12 is only a monitoring wave (for the monitoring space V). S ) or simply the imaging wave (in the imaging space V) I middle).

[0116] Following step 210, the boot system 10 then performs steps 220 to 250, which are similar to steps 120 to 150 of the previously described monitoring operation mode MS. Therefore, these steps 220 to 250 will not be described in detail below.

[0117] In parallel, the guidance system 10 also implements step 270, during which the post-processing module 32 transmits the signal corresponding to the imaging wave to the imaging chain 14, and specifically to the display 21.

[0118] These signals are then used, using techniques known to them, to reconstruct an enhanced vision of the aircraft's external environment.

[0119] In particular, for public space V C When the reflected wave corresponds to both the imaging wave and the monitoring wave, steps 220 and 270 are implemented in parallel by the post-processing module 32.

[0120] Similar to Figure 5 , Figure 6 The implementation of the hybrid operation mode (MM) of the boot system 10 is shown.

[0121] In particular, as in the previous case, the Figure 6 The radar module 12 is shown transmitting surveillance wave S. V And confirm wave S C To identify or remove obstacles B or to periodically inspect the terrain and / or runway P.

[0122] Unlike before, monitoring wave S V 1 and S V 4 Sent to public space V C In this case, these waves are then used by both the processing module 38 and the imaging chain 14, and specifically by the display 21.

[0123] In contrast, monitoring wave S V 2 S V 3 S V 5 and S V 6 Sent to monitoring space V S In its exclusive part, and therefore used only by the processing module 38 and not by the imaging chain 14.

[0124] Therefore, it should be understood that the present invention offers a number of advantages.

[0125] In particular, the guidance system according to the invention combines monitoring and imaging functions into the same system.

[0126] Therefore, crew members can interact with such a system in a centralized manner, which makes it possible to reduce their cognitive load during certain phases of flight, especially during approach or any other critical phase.

[0127] Furthermore, the guidance system according to the invention uses the same millimeter radar for multiple functions and employs the same management module to determine the waveform of the millimeter radar, and uses the same post-processing module to process the reflected waves. Therefore, this reduces the size and complexity of the system.

[0128] Of course, other implementation schemes are also possible.

Claims

1. A system (10) for guiding an aircraft, comprising: An imaging chain (14) is configured to reconstruct an image of the external environment; A monitoring chain (16) is configured to detect obstacles in the flight path of the aircraft; Radar module (12), which is capable of emitting millimeter waves and receiving reflected waves; The management module (31) is configured to control the radar module (12) between a monitoring operation mode that includes transmitting only monitoring waves and a hybrid operation mode that includes transmitting a hybrid wave that combines monitoring waves and imaging waves. The post-processing module (32) is configured to process the reflected wave in order to transmit the signal corresponding to the imaging wave to the imaging chain (14) and / or transmit the signal corresponding to the monitoring wave to the monitoring chain (16).

2. The system (10) according to claim 1, wherein, The management module (31) is configured to determine the imaging space (V) covered by the imaging wave. I ) and the monitoring space (V) covered by the monitoring wave. S ); The monitoring space (V) S The imaging space (V) is compared to the imaging space. I Wider or with the imaging space (V) I The aperture is defined by the aperture angle that is equal to the aperture angle of the aperture. Public Space (V) C ) by the monitoring space (V S ) and the imaging space (V I Limited by the intersection of ) ; Advantageously, the imaging space (V I The monitoring space (V) is compared to the aforementioned space. S (Limited by longer range) 3. The system (10) according to claim 2, wherein, The monitoring space (V) is determined based on the aircraft's speed, its altitude, and assumptions about potential obstacles along its path. S ).

4. The system (10) according to claim 2 or 3, wherein, The imaging space (V) I The altitude of the aircraft and its trajectory relative to the landing runway are determined based on the aircraft's altitude and its trajectory relative to the landing runway.

5. The system (10) according to any one of the preceding claims in conjunction with claim 2, wherein, The monitoring wave includes: waves periodically transmitted to the monitoring space (V S The monitoring wave is used to detect possible obstacles on the route of the aircraft, and the confirmation wave is sent toward the possible obstacle detected by the monitoring wave to confirm or eliminate the obstacle.

6. The system (10) according to claim 5, wherein, The management module (31) is configured to switch the radar module (12) to a hybrid operation mode when the confirmation wave detects terrain and / or landing runway.

7. The system (10) according to claim 6, wherein, The management module (31) is configured to periodically send the confirmation wave to the terrain.

8. The system (10) according to any one of the preceding claims, wherein, The management module (31) is configured to switch the radar module (12) to a hybrid operation mode or a surveillance operation mode by comparing the altitude of the aircraft with a predetermined threshold.

9. The system (10) according to claim 8, wherein, The predetermined threshold is between 400 feet and 600 feet, and advantageously substantially equal to 500 feet.

10. The system (10) according to any one of the preceding claims, wherein, The monitoring chain (16) includes a processing module (38) configured to determine the collision trajectory with a potential obstacle detected by the monitoring wave.

11. A method for guiding an aircraft, said method being implemented by a system (10) according to any one of the preceding claims and comprising the following steps: In the monitoring operation mode, only (110) monitoring waves are emitted; Transmit (210) hybrid wave in the hybrid operation mode; The reflected waves (120, 220, 270) are received and processed so that the signal corresponding to the imaging wave is transmitted to the imaging chain (14) or the signal corresponding to the monitoring wave is transmitted to the monitoring chain (16).

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