METHOD AND DEVICE FOR ASSISTING THE CREW OF AN AIRCRAFT IN LEADING THE AIRCRAFT OUT OF A STEREOTYPE

Description

TECHNICAL FIELD

[0001] The present invention relates to a method and a pilot assistance device, for helping the crew of an aircraft to get the aircraft out of a stall situation. STATE OF THE ART

[0002] It is known that the command and control system of an aircraft, particularly a transport aircraft, may, under certain conditions, be brought into a degraded mode in which various flight envelope protections may be lost, such as angle of attack protection.

[0003] In such conditions, the aircraft may approach a stall situation, and without an appropriate reaction from the crew, the aircraft may actually experience a stall, namely a sudden reduction in its lift, caused by too great an angle of attack, which causes a considerable loss of altitude, a stall generally occurring at low speed.

[0004] The usual strategies for dealing with stall events or risks are based solely on issuing an alert signaling a stall situation and on the application, in this case, by the aircraft crew of the recommended procedure.

[0005] In a process of continuous improvement, aircraft manufacturers are considering improvements to this strategy.

[0006] Furthermore, document US 2014 / 371957 A1 discloses a method for diagnosing a loss of control of an aircraft. This method consists of detecting characteristic loss of control thresholds from raw data and aircraft data, then identifying at least one type of priority loss of control and communicating it to the crew.

[0007] We also know, from the document entitled "Stall (flight)" from the internet page https: / / simple.wikipedia.org / wiki / Stall (flight) , a concise list of generic steps to recover an aircraft from a stall situation. STATEMENT OF THE INVENTION

[0008] The present invention aims to meet this need. To do this, it relates to a method for assisting the piloting of an aircraft, to help the crew of the aircraft to get the aircraft out of a stall situation according to claim 1.

[0009] According to the invention, said method comprises at least the following steps: an angle of incidence reduction step, implemented by a first angle of incidence reduction unit at a predetermined duration after a stall alert has been issued in the event of no reaction from the crew, the angle of incidence reduction step comprising a calculation sub-step consisting of generating a first target angle of incidence to pitch down and converting this first target angle of incidence into a first pitch order, and a display sub-step consisting of displaying on at least one vertical display system of the aircraft at least one first indicator representative of said first pitch order;a stabilization step, implemented by a stabilization unit after the angle of incidence reduction step, said stabilization step comprising a calculation sub-step consisting of generating a second target angle of incidence to pitch up and converting this second target angle of incidence into a second pitch order, and a second display sub-step consisting of displaying on the vertical display system of the aircraft at least one second indicator representative of said second pitch order.;

[0010] Thus, thanks to the invention, pilot assistance indicators are determined and displayed on at least one display system of the aircraft when the aircraft approaches a stall situation, i.e. after a stall warning has been issued followed by an absence of (appropriate) reaction from the crew. These indicators will help the crew to remove the aircraft from the stall situation in terms of angle of incidence, load factor and speed.

[0011] In the context of the present invention, the term "stall situation" means one or other of the following two situations: a situation of risk of stalling or a situation of proven stalling, as specified below.

[0012] According to the invention, said method further comprises a roll control step implemented by a roll control unit, this roll control step comprising a calculation sub-step consisting of converting a target roll angle into a roll order and a display sub-step consisting of displaying on at least one lateral display system of the aircraft at least one indicator representative of said roll order, the roll control step being implemented from the moment when the lateral bank angle of the aircraft is greater than a predetermined value and the pitch angle of the aircraft is negative, and this until the end of the stabilization step. Preferably, the target roll angle is substantially equal to 0°.

[0013] Further, advantageously, the calculating sub-step of the angle of attack reduction step generates the first target angle of attack so as to obtain a predetermined margin with respect to a stall warning angle of attack.

[0014] Furthermore, advantageously, the calculation sub-step of the stabilization step generates the second target angle of attack so as to obtain a flight path angle substantially equal to a total flight path angle.

[0015] Furthermore, advantageously, the stabilization step: is implemented as soon as the current angle of attack of the aircraft is less than a predetermined margin of a stall alert angle of attack; and / or is terminated (or stopped) when the stall alert is deactivated and the flight path angle of the aircraft is equal to the total flight path angle for a predetermined duration.

[0016] Furthermore, according to the invention, if, during the implementation of the stabilization step, the current angle of incidence of the aircraft approaches a predetermined auxiliary margin of a stall warning angle of incidence, the angle of incidence reduction step is again implemented instead of said stabilization step.

[0017] The present invention also relates to a device for assisting the piloting of an aircraft, to help the crew of the aircraft to get the aircraft out of a stall situation.

[0018] According to the invention, said device comprises at least: an angle of incidence reduction unit comprising a calculation unit configured to generate, at a predetermined time after a stall alert has been issued in the event of no reaction from the crew, a first target angle of incidence to pitch down and to convert this first target angle of incidence into a first pitch order, and a display unit configured to display on at least one vertical display system of the aircraft at least one first indicator representative of said first pitch order; a stabilization unit comprising a calculation unit configured to generate a second target angle of incidence to pitch up and to convert this second target angle of incidence into a second pitch order, and a second display unit configured to display on the vertical display system of the aircraft at least one second indicator representative of said second pitch order.

[0019] Furthermore, advantageously, said device further comprises a roll control unit comprising a calculation unit configured to convert a target roll angle into a roll order and a display unit configured to display on at least one lateral display system of the aircraft at least one indicator representative of said roll order. BRIEF DESCRIPTION OF THE FIGURES

[0020] The attached figures will make it clear how the invention can be implemented. In these figures, identical references designate similar elements. There figure 1 is the block diagram of an aircraft pilot assistance device intended to help the aircraft recover from a stall situation. figure 2 is a schematic view of an aircraft flying along a flight path, on which the steps of a pilot assistance method implemented by the pilot assistance device of the figure 1. THE Figures 3A to 3D illustrate the display produced on a vertical display system during the implementation of the piloting assistance method, respectively at successive moments of a step of reducing the angle of incidence of said piloting assistance method. Figures 3E to 3G illustrate the display produced on the vertical display system during the implementation of the piloting assistance method, respectively at successive moments of a stabilization step of said piloting assistance method. DETAILED DESCRIPTION

[0021] Device 1, shown in the figure 1 and illustrating the invention is a device for assisting in piloting an AC aircraft, in particular a transport aircraft, shown as an example in the figure 2 .

[0022] This device 1 is intended to assist the aircraft crew in recovering the AC aircraft from a stall situation. The crew of the AC aircraft means the pilot(s) of the AC aircraft and any other person involved in the flight management of the AC aircraft.

[0023] This device 1 may be part of a more general system 2 for presenting data and / or assisting in the control and management of the flight of the aircraft AC.

[0024] This system 2 includes in particular, as shown in the figure 1 : an alert device 3 configured to trigger, in the usual manner, a stall alert, visually and / or audibly, when the conditions for such triggering are met; a set 4 of usual information sources, comprising sensors and / or various elements or devices capable of determining the current values ​​of parameters of the aircraft AC, such as its speed, its angle of incidence, its load factor, etc.; at least one vertical display system 5. This vertical display system 5 comprises one or more screens 6 capable of displaying the current parameter values ​​of the aircraft along the vertical axis, as specified below with reference to the screen 6 shown in the Figures 3A to 3G ; and at least one lateral display system 7. This lateral display system 7 is configured to be able to display the current values ​​of parameters of the aircraft along the lateral axis.

[0025] Device 1 is activated after the triggering of the stall alert (generated by alert device 3), taking into account a predetermined delay time (for example three seconds) allowing the crew to react appropriately and so as not to disturb the crew when it reacts correctly (according to the appropriate procedure) to this stall alert.

[0026] In the context of the present invention, it is considered that one is in a "stall situation" when one or other of the following two situations occurs: a situation of risk of stall or a situation of proven stall. Indeed, if the crew has not carried out an appropriate maneuver within the time allowed after the stall alert has been issued (or triggered), the aircraft may find itself in a situation in which it is flying beyond the stall alert angle of attack or a situation in which it has dynamics that will take it beyond the stall angle of attack.

[0027] The stall alert is triggered, in the usual way, by alert device 3, taking into account the current values ​​of the following aircraft parameters: the angle of attack (AOA), namely the angle formed by the longitudinal axis of the aircraft and by the projection of its speed vector onto a reference plane passing through this longitudinal axis; the load factor: and the speed.

[0028] The device 1 which is connected via links 8 and 9 respectively to the alert device 3 and to the assembly 4 comprises, as shown in the figure 1 : an angle of incidence reduction unit 10 comprising a calculation unit 11 and a display unit 12. The calculation unit 11 is configured to generate, at a predetermined time after the emission of a stall alert (by the alert device 3) in the event of no reaction from the crew, a target angle of incidence α1c to pitch down (specified below) and to convert this target angle of incidence α1c into a pitch order OT1. The display unit 12 is configured to display on the screen 6 of the vertical display system 5 (as illustrated by a link 14) at least one indicator 32 ( Figures 3B to 3D) representative of said pitch order OT1 (received from the calculation unit 11 via a link 13); a roll control unit 15 comprising a calculation unit 16 and a display unit 17. The calculation unit 16 is configured to convert a predetermined target roll angle φc into a roll order OR. The display unit 17 is configured to display on at least one screen (not shown) of the lateral display system 7 (as illustrated by a link 19) at least one indicator (not shown) representative of said roll order OR (received from the calculation unit 16 via a link 18); and a stabilization unit 20 comprising a calculation unit 21 and a display unit 22. The calculation unit 21 is configured to generate a target angle of incidence α2c to pitch up (specified below) and to convert this target angle of incidence α2c into a pitch command OT2.The display unit 22 is configured to display on the screen 6 of the vertical display system 5 (as illustrated by a link 24) at least one indicator 32 (. Figures 3F and 3G ) representative of the pitch order OT2 (received from the computing unit 21 via a link 23).

[0029] The device 1, as described above, is capable of implementing a pilot assistance method P. This pilot assistance method P is intended to help the crew of the aircraft AC to remove (if necessary) the aircraft AC from a stall situation.

[0030] Said method P is illustrated in the figure 2 . This figure 2 shows different positions of the aircraft AC (equipped with device 1) flying along a flight path TV during the implementation of said method P. This figure 2 shows in particular the periods of implementation of the different stages E1, E2 and E3 (specified below) of this process P during the flight of the aircraft AC.

[0031] The P method is described below, with reference to the Figures 3A to 3G which illustrate a particular embodiment of a screen 6 of the vertical display system 5. This screen 6 comprises, in the usual manner, a display window 25 relating to a flight director which displays, in real time, a symbol 26 indicating the current value of the pitch angle of the aircraft AC. In addition, the screen 6 also comprises usual display windows 27 and 28 which display, respectively, speed and altitude information of the aircraft AC.

[0032] Said method P comprises, first of all, a step E1 of reducing the angle of incidence. The step E1 is implemented by the angle of incidence reduction unit 10 ( figure 1), in the event of a stall alert being issued by the alert device 3 and the absence of an appropriate reaction from the crew after a predetermined period (after this issue). This alert is signaled on the screen 6 by several displays, preferably in red, of the English term “STALL” (meaning “stall”) as shown by an arrow 29 on the Figure 3A The alert is also signaled by an auxiliary indicator 31 on the speed window 27 next to the speed scale 30. This auxiliary indicator 31 comprises, for example, red squares which are arranged at all speeds on the speed scale 30, likely to generate a stall.

[0033] Step E1 comprises a calculation sub-step (implemented by the calculation unit 11) consisting of generating the target angle of incidence α1c to pitch down, as well as converting this target angle of incidence α1c to obtain the pitch order OT1, and a display sub-step (implemented by the display unit 12) consisting of displaying on the screen 6 of the vertical display system 5 at least the indicator 32 representative of said pitch order OT1, as shown in the Figure 3B .

[0034] The calculation unit 11 calculates, in the calculation sub-step of the angle of incidence reduction step E1, the target angle of incidence α1c so as to obtain a sufficient (predetermined) margin with respect to a stall warning angle of incidence, that is to say with respect to the angle of incidence for which the stall warning is generated by the warning device 3.

[0035] Step E1 (and thus process P) is therefore triggered after the triggering of the stall alert, with a delay to avoid disturbing a crew that has reacted correctly to the stall alert.

[0036] After the alert is issued, as shown in the Figure 3A , triggering the implementation of the method P, the indicator 32 is therefore displayed on the window 25, as shown in the Figure 3B , From this moment, the crew pilots the aircraft AC, preferably manually, to bring the current pitch of the aircraft AC to the pitch value indicated by the indicator 32, by making the symbol 26 coincide with this indicator 32, as shown in the Figure 3C .

[0037] In the following situation, shown in the 3D figure , the AC aircraft has recovered the desired angle of attack margin.

[0038] The purpose of this step E1 is to allow the crew to manually pilot the AC aircraft in order to apply the OT1 pitch order so that the AC aircraft returns to an appropriate angle of incidence for which there is no longer any risk of stalling.

[0039] The method P also comprises a roll control step E2, implemented by the roll control unit 15. The roll control step E2 comprises a calculation sub-step (implemented by the calculation unit 16) consisting of converting the target roll angle φc (of predetermined value) to obtain the roll order OR and a display sub-step (implemented by the display unit 17) consisting of displaying on the lateral display system 7 ( figure 1) at least one indicator (not shown) representative of said roll order OR. This roll control step E2 is implemented, after the triggering of step E1, when the aircraft crew has achieved a significant reduction in the angle of incidence during the implementation of step E1. More precisely, this step E2 begins from the moment when the lateral bank angle of the aircraft AC is greater than a predetermined value and the pitch angle of the aircraft AC is negative.

[0040] During step E2, the crew pilots the aircraft AC, preferably manually, to bring the current roll of the aircraft AC to the roll value indicated by the indicator (not shown) representative of said roll order OR.

[0041] This roll control step E2 is implemented until the end of stabilization step E3 specified below.

[0042] Preferably, the target roll angle φc is substantially equal to 0°. The purpose of step E2 is thus to cancel any roll of the aircraft AC and to maintain the roll at zero during the implementation of the method P to stabilize it laterally.

[0043] The method P also comprises this (vertical) stabilization step E3. Step E3 is implemented by the stabilization unit 20, after the angle of incidence reduction step E1. The stabilization step E3 comprises a calculation sub-step (implemented by the calculation unit 21) consisting of generating the target angle of incidence α2c to pitch up and converting this target angle of incidence α2c to obtain the pitching order OT2, and a display sub-step (implemented by the display unit 22) consisting of displaying on the screen 6 of the vertical display system 5 at least the indicator 32 representative of this pitching order OT2, as shown in the Figure 3F .

[0044] In the example shown on the Figures 3B to 3G , the same indicator 32 is provided to display the pitching order OT1 at step E1 and to display the pitching order OT2 at step E3. It could also be envisaged to display two different indicators (for example of different shapes, sizes and / or colors) respectively for these two pitching orders OT1 and OT2.

[0045] The calculation unit 21 calculates, in the calculation sub-step of the stabilization step E3, the target angle of attack α2c so as to obtain a flight path angle (FPA) of the aircraft AC substantially equal to a total flight path angle.

[0046] Furthermore, the stabilization step E3 (i.e. the transition from step E1 to step E3) is implemented as soon as the current angle of attack of the aircraft AC is lower (by a predetermined margin) than the stall alert angle of attack. This transition is shown in the Figure 3E .

[0047] As step E3 is implemented after phase E1 (angle of incidence reduction), this step E3 aims to generate a pitch order OT2 to nose up in order to reduce the loss of altitude of the aircraft AC and to stabilize its aerodynamic speed (with the current thrust of the engines of the aircraft AC).

[0048] During step E3, the crew pilots the aircraft AC, preferably manually, to bring the current pitch of the aircraft AC to the pitch value indicated by the indicator 32, by making the symbol 26 coincide with this indicator 32, as shown in the Figure 3F .

[0049] Stabilization step E3 (and thus process P) is completed, as shown in the Figure 3G , when the following two conditions are met simultaneously: the stall alert is deactivated; and the aircraft's flight path angle is equal to the total flight path angle for a predetermined duration.

[0050] Furthermore, if, during the implementation of the stabilization step E3, the current angle of incidence of the aircraft AC approaches again (by a predetermined auxiliary margin) the stall alert angle of incidence, the angle of incidence reduction step E1 is again implemented instead of said stabilization step E3. This makes it possible to obtain an inversion of these steps E1 and E3, and the method P is again implemented in the manner described above from this step E1.

[0051] The transition between steps E1 and E3 is therefore reversible. The reverse transition from step E3 to step E1 is implemented when the current angle of incidence approaches too close to the stall warning angle of incidence, by providing hysteresis with respect to the initial transition between steps E1 and E3.

[0052] Thus, thanks to this method P implemented by the device 1, pilot assistance indicators are determined and displayed on the display systems 5 and 7 of the aircraft when the aircraft approaches a stall situation (after the stall warning has been triggered). These indicators will help the crew to quickly and efficiently exit this situation and return to a nominal flight situation in terms of angle of incidence, load factor and speed, with the aircraft stabilized at the end of the process.

[0053] Device 1, as described above, thus has many advantages. First of all, it increases the crew's awareness of the stall situation.

[0054] In addition, by following the indicators intended to enable an exit from the stall situation, the crew: prevents the aircraft from actually stalling (and entering a "deep stall" situation); avoids triggering a second stall situation alert during the recovery phase from the stall situation; avoids an excessive reaction which could generate a significant overspeed; and allows the aircraft to reach a stable situation upon recovery from the stall situation.

Claims

1. A piloting assistance method for an aircraft, for assisting the aircraft crew in recovering the aircraft from a stall condition, said method comprising at least the following steps: - an angle of attack reduction step (E1), implemented by a first angle of attack reduction unit (10) at a predetermined time after a stall warning has been transmitted in the event of a lack of response from the crew, the angle of attack reduction step (E1) comprising a computation sub-step involving generating a first nose down target angle of attack and converting this first target angle of attack into a first pitch command, and a display sub-step involving displaying, on at least one vertical display system (5) of the aircraft (AC), at least one first indicator (32) representing said first pitch command; - a stabilization step (E3), implemented by a stabilization unit (20) after the angle of attack reduction step (E1), said stabilization step (E3) comprising a computation sub-step involving generating a second nose up target angle of attack and converting this second target angle of attack into a second pitch command, and a second display sub-step involving displaying, on the vertical display system (5) of the aircraft (AC), at least one second indicator (32) representing said second pitch command; - a roll control step (E2), implemented by a roll control unit (15), comprising a computation sub-step involving converting a target roll angle into a roll command and a display sub-step involving displaying, on at least one lateral display system (7) of the aircraft (AC), at least one indicator representing said roll command, the roll control step (E2) being implemented from the moment when the lateral bank angle of the aircraft (AC) is greater than a predetermined value and the pitch angle of the aircraft (AC) is negative, until the end of the stabilization step (E3), the method being characterized in that if, when the stabilization step (E3) is implemented, the current angle of attack of the aircraft (AC) approaches a predetermined additional margin of a stall warning angle of attack, the angle of attack reduction step (E1) is implemented again instead of said stabilization step (E3).

2. The method as claimed in claim 1, characterized in that the target roll angle is substantially equal to 0°.

3. The method as claimed in any one of the preceding claims, characterized in that the computation sub-step of the angle of attack reduction step (E1) generates the first target angle of attack so as to obtain a predetermined margin in relation to a stall warning angle of attack.

4. The method as claimed in any one of the preceding claims, characterized in that the computation sub-step of the stabilization step (E3) generates the second target angle of attack so as to obtain a flight path angle that is substantially equal to a total flight path angle.

5. The method as claimed in any one of the preceding claims, characterized in that the stabilization step (E3) is implemented as soon as the current angle of attack of the aircraft (AC) is lower than a stall warning angle of attack by a predetermined margin.

6. The method as claimed in any one of the preceding claims, characterized in that the stabilization step (E3) is completed when the stall warning is deactivated and the flight path angle of the aircraft (AC) is equal to the total flight path angle for a predetermined duration.

7. A piloting assistance device for an aircraft, for assisting the aircraft crew in recovering the aircraft from a stall condition, said device (1) comprising at least: - an angle of attack reduction unit (10) comprising a computation unit (11) configured to generate, at a predetermined time after a stall warning has been transmitted in the event of a lack of response from the crew, a first nose down target angle of attack and to convert this first target angle of attack into a first pitch command, and a display unit (12) configured to display, on at least one vertical display system (5) of the aircraft (AC), at least one first indicator (32) representing said first pitch command; - a stabilization unit (20) comprising a computation unit (21) configured to generate a second nose up target angle of attack and to convert this second target angle of attack into a second pitch command, and a second display unit (22) configured to display, on the vertical display system (5) of the aircraft (AC), at least one second indicator (32) representing said second pitch command; - a roll control unit (15) comprising a computation unit (16) configured to convert a target roll angle into a roll command and a display unit (17) configured to display, on at least one lateral display system (7) of the aircraft (AC), at least one indicator representing said roll command, the device (1) being configured such that if, when the stabilization step (E3) is implemented by the stabilization unit (20), the current angle of attack of the aircraft (AC) approaches a predetermined additional margin of a stall warning angle of attack, an angle of attack reduction step (E1) is implemented again by the angle of attack reduction unit (10) instead of said stabilization step (E3).