Method and an aircraft for minimizing the risks of the aircraft toppling on the ground

Abstract

A method of assisting a pilot in order to minimize the risks of an aircraft rolling over on the ground, the aircraft having a main rotor and a yaw movement control rotor (4), together with lateral cyclic pitch control means for the main rotor and yaw movement control means for the yaw movement control rotor. At least one measurement is taken relating to left forces exerted on a left side undercarriage and to right forces exerted on a right side undercarriage in order to evaluate asymmetry, if any, between the left and right forces, and then a recommended position (26) is determined for at least one of the yaw and lateral cyclic pitch control means in order to make the left and right forces more symmetrical. Each recommended position is displayed on a display unit.

Claims

1. A method of assisting a pilot to minimize the risk of an aircraft rolling over on the ground, the aircraft having a main rotor and a yaw movement control rotor, the aircraft having controls including a lateral cyclic pitch control to control the main rotor and a yaw movement control to control the yaw movement control rotor, the aircraft having landing gear provided with at least one left side undercarriage and at least one right side undercarriage that are arranged on either side of an anteroposterior longitudinal plane of the aircraft, wherein during a utilization stage the following steps are performed: taking at least one measurement relating to the left forces exerted on the left side undercarriage and to the right forces exerted on the right side undercarriage in order to evaluate asymmetry, if any, between the left and right forces; when the at least one measurement reveals asymmetry between the left and right forces, determining a recommended position for at least one of the yaw movement control and lateral cyclic pitch control in order to make the left and right forces more symmetrical; and using a display unit to display each recommended position to inform the pilot of the position to be reached by at least one of the yaw movement control and the lateral cyclic pitch control in order to keep the aircraft within a domain of roll stability on the ground.

2. A method according to claim 1, wherein during an initialization stage the influence of the yaw movement control and lateral cyclic pitch control on the asymmetry of the left and right forces is determined in order to establish at least one database providing the at least one recommended position for making the left and right forces more symmetrical, the database being used to determine each recommended position during the utilization stage.

3. A method according to claim 2, wherein: during the initialization stage, the influence of the yaw movement control and lateral cyclic pitch control on the asymmetry of the left and right forces is determined as a function of the speed of rotation of the main rotor and/or of the yaw movement control rotor; and during the utilization stage, at least one measurement is taken relating to the left forces exerted on the left side undercarriage and to the right forces exerted on the right side undercarriage, and at least one measurement is taken relating to each speed of rotation taken into consideration during the initialization stage.

4. A method according to claim 1, wherein with a recommended position for at least one of the controls being determined and displayed, a current position is determined of each controls for which a position is recommended, and the current position is displayed on the display unit.

5. A method according to claim 1, wherein, in order to display a recommended position for the lateral cyclic pitch control and for the yaw movement control, a single symbol is displayed in a two-dimensional representation in which the dimensions relate respectively to the position of the lateral cyclic pitch control and to the position of the yaw movement control.

6. A method according to claim 1, wherein priority is given to a single flight control for keeping the aircraft in the stable domain by displaying a recommended position on a scale either for the lateral cyclic pitch control or for the yaw movement control depending on the movement of the aircraft relative to the ground.

7. A method according to claim 6, that is determined whether the aircraft is taxiing on the ground, and if the aircraft is taxiing, a recommended position is displayed solely for the lateral cyclic pitch control.

8. A method according to claim 6, that is determined whether the aircraft is taxiing on the ground, and if the aircraft is not taxiing, a recommended position is then displayed solely for the yaw movement control.

9. A method according to claim 1, wherein the at least one measurement relating to the left forces exerted on the left side undercarriage and to the right forces exerted on the right side undercarriage is performed indirectly by determining a roll angle of the aircraft.

10. A method according to claim 9, wherein the following steps are performed: determining an initial roll angle before starting the rotors of the aircraft; determining a current roll angle of the aircraft over time; and determining a recommended position for at least one of the yaw movement control and lateral cyclic pitch control and displaying it on the display unit so that the current roll angle tends towards the initial roll angle.

11. A method according to claim 10, wherein the following steps are performed: determining an initial roll angle before starting the rotors of the aircraft over a given period of time in order to determine a maximum initial roll angle and a minimum initial roll angle reached during the period; and inhibiting the display of each recommended position when the difference between the maximum initial roll angle and the minimum initial roll angle exceeds a threshold difference.

12. A method according to claim 1, wherein at least one measurement relating to the left forces exerted on the left side undercarriage and to the right forces exerted on the right side undercarriage is performed directly in order to evaluate said asymmetry by determining the forces exerted on the left undercarriage and on the right undercarriage by using measurement means arranged on each undercarriage.

13. A method according to claim 12, wherein said at least one measurement relating to the left forces exerted on the left side undercarriage and to the right forces exerted on the right side undercarriage is performed directly in order to determine whether asymmetry exists by applying at least one of the following methods: the left and right forces are determined by means for measuring forces proper; the left and right forces are determined by devices for measuring pressure by measuring the pressure within a shock absorber in each undercarriage; and the left and right forces are determined by devices for measuring position by measuring the position of at least one movable member of each undercarriage.

14. A method according to claim 1, wherein potential asymmetry of loading is evaluated by taking a single measurement relating to the left forces exerted on the left side undercarriage and to the right forces exerted on the right side undercarriage, by applying at least one of the following methods: measuring a pressure difference between a pressure existing within a shock absorber of a right undercarriage and a pressure existing within a shock absorber in a left undercarriage; and measuring a position difference between a position of at least one movable member of a right undercarriage and a position of at least one movable member of a left undercarriage.

15. A method according to claim 1, wherein an alert is triggered when the at least one measurement relating to the left forces exerted on the left side undercarriage and to the right forces exerted on the right side undercarriage reveal asymmetry between the left and right forces that exceeds a certain threshold.

16. An aircraft having a main rotor and a yaw movement control rotor, the aircraft having controls including a lateral cyclic pitch control to control the main rotor and a yaw movement control to control the yaw movement control rotor, the aircraft including landing gear having at least one left side undercarriage and at least one right side undercarriage that are arranged on either side of an anteroposterior longitudinal plane of the aircraft, wherein the aircraft includes an assistance device performing the method according to claim 1, the assistance device having: a measurement system for determining asymmetry, if any, of the left and right forces exerted respectively on the left side undercarriage and on the right side undercarriage by taking at least one measurement relating to the left forces exerted on the left side undercarriage and to the right forces exerted on the right side undercarriage; a processor for determining a recommended position for at least one of the yaw movement control and lateral cyclic pitch control in order to make the left forces and the right forces more symmetrical; and a display unit for displaying at least one item of information relating to the recommended position in order to inform a pilot of the position to be reached by at least one of the yaw movement control and the lateral cyclic pitch control in order to keep the aircraft in a domain of roll stability.

17. An aircraft according to claim 16, wherein the assistance device includes at least one of the following members: means for measuring a roll angle of the aircraft; and means for measuring the forces exerted on two distinct undercarriages.

18. A method of assisting a pilot of an aircraft in reestablishing symmetrical loading on undercarriages to reduce the risk of the aircraft rolling over on a ground surface, the aircraft having a main rotor controlled by a lateral cyclic pitch control, a yaw movement control rotor controlled by a yaw movement control, and a display for displaying information to the pilot, the method comprising: taking at least one measurement relating to a left force exerted on a left side undercarriage of the aircraft and a right force exerted on a right side undercarriage of the aircraft; evaluating the at least one measurement to determine asymmetry between the left and right forces; in response to determining asymmetry, determining a first recommended position for the yaw movement control to control the yaw movement control rotor of the aircraft, and a second recommended position for the lateral cyclic pitch control to control the main rotor of the aircraft; and displaying a graphical representation of the first and second recommended positions on the display to inform the pilot of the position to be reached by at least one of the yaw movement control and the lateral cyclic pitch control in order to keep the aircraft within a domain of roll stability on the ground.

19. A system for assisting a pilot of an aircraft in reestablishing symmetrical loading on undercarriages to reduce the risk of the aircraft rolling over on a ground surface, the aircraft having a main rotor controlled by a lateral cyclic pitch control, a yaw movement control rotor controlled by a yaw movement control, the system comprising: a processor adapted to: receive at least one measurement relating to a left force exerted on a left side undercarriage of the aircraft and a right force exerted on a right side undercarriage of the aircraft; evaluate the at least one measurement to determine asymmetry between the left and right forces; and in response to determining asymmetry, determine a first recommended position for the yaw movement control to control the yaw movement control rotor and a second recommended position for the lateral cyclic pitch control to control the main rotor; and a display unit adapted to display a graphical representation of the first and second recommended positions, the graphical representation including a first axis corresponding to the first recommended position for the yaw movement control to control the yaw movement control rotor, and a second axis corresponding to the second recommended position for the lateral cyclic pitch control to control the main rotor.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The invention and its advantages appear in greater detail from the context of the following description of embodiments given by way of illustration and with reference to the accompanying figures, in which:

(2) FIG. 1 is a diagrammatic view of an aircraft of the invention;

(3) FIG. 2 is a diagram showing an assistance device;

(4) FIG. 3 is a diagram showing the stages of a method of the invention;

(5) FIGS. 4 to 6 are diagrams showing the information displayed depending on the state of the aircraft; and

(6) FIG. 7 is a graph explaining how to determine the recommended positions for presenting during the first operating state of the aircraft.

(7) Elements present in more than one of the figures are given the same references in each of them.

DETAILED DESCRIPTION OF THE INVENTION

(8) FIG. 1 shows an aircraft 1 having an airframe 2.

(9) The airframe 2 carries a rotary wing. The rotary wing is constituted by a main rotor 3 having a plurality of blades 3′. The main rotor 3 thus provides the aircraft with at least some of its lift, and, by way of example, if the aircraft is a helicopter, it also provides it with propulsion.

(10) The airframe 2 also carries a yaw movement control rotor 4, conventionally referred to as a “tail” rotor.

(11) The aircraft also has landing gear on which the airframe 2 rests. The landing gear comprises three wheeled undercarriages. Under such circumstances, the landing gear has a left side undercarriage 70 and a right side undercarriage 75 that are arranged symmetrically on either side of the anteroposterior plane of symmetry of the aircraft. In FIG. 1, the right side undercarriage 75 is hidden by the left side undercarriage 70.

(12) In addition, the aircraft 1 has control means 5 for controlling the main rotor 3 and for controlling the yaw movement control rotor 4.

(13) Such control means 5 include yaw movement control means 8, e.g. of the type comprising pedals. The yaw movement control means 8 co-operate with the yaw movement control rotor 4.

(14) The control means 5 include also a cyclic stick for modifying the pitch of the blades 3′ of the main rotor 3 cyclically. The cyclic stick then includes lateral cyclic pitch control means 6 on being manipulated in a lateral direction represented by double-headed arrow F1, and longitudinal cyclic pitch control means 7 on being manipulated in a longitudinal direction represented by double-headed arrow F2. Naturally, the cyclic stick may be manipulated in any direction, and is suitable for acting simultaneously on the lateral cyclic pitch and on the longitudinal cyclic pitch.

(15) The control means 5 also include collective pitch control means 9 for modifying the pitch of the blades 3′ of the main rotor 3 collectively. The collective pitch control means 9 are conventionally referred to as the “collective pitch lever” or indeed as the “collective stick”.

(16) The aircraft is also provided with an assistance device 10 that applies the method of the invention in order to facilitate the work of a pilot on the ground.

(17) With reference to FIG. 2, the assistance device 10 includes a processor unit 15. The processor unit 15 may comprise calculation means 16 and storage means 17, the calculation means executing instructions stored in the storage means 17 in order to perform said method. Such calculation means may comprise at least one processor.

(18) The processor unit 15 is then connected to a display unit 20. The display unit 20 may comprise a display screen 21 suitable for presenting symbols in order to assist a pilot.

(19) It can be understood that the processor unit 15 and the display unit 20 may form a single piece of equipment.

(20) The processor unit is also connected in particular to a measurement system 30 seeking to collect data making it possible to determine whether the left side undercarriage and the right side undercarriage are being subjected to asymmetrical loads when the aircraft is on the ground.

(21) By way of example, such a measurement system 30 may comprise measurement means 55 for measuring a roll angle of the aircraft, such as an inclinometer or an inertial unit, for example.

(22) The measurement system 30 may also be provided with a measurement device 60 for measuring the forces proper exerted on the left side undercarriage 70 and on the right undercarriage 75. The measurement device 60 may include devices for measuring forces proper, devices for measuring pressures, or indeed devices for measuring position, in order to determine said forces proper.

(23) Furthermore, the measurement system 30 may include a first device 35 for measuring the speed of rotation of the main rotor 3, and a second device 40 for measuring the speed of rotation of the yaw movement control rotor 4.

(24) The first device 35 and the second device 40 may be embodied as a single device. The main rotor 3 and the yaw movement control rotor 4 are usually dynamically connected together. Their speeds of rotation are thus at a constant ratio. Under such circumstances, a single measurement device suffices.

(25) Likewise, a third device 45 is used to determine whether the aircraft is taxiing.

(26) It should be observed that the devices delivering data to the processor unit are members that are usually present on aircraft.

(27) FIG. 3 explains the method applied by the assistance device.

(28) During a first stage STP1, it is determined whether the left side undercarriage 70 and the right side undercarriage 75 are loaded symmetrically.

(29) The measurement system 30 then acts directly or indirectly to take at least one measurement relating to the left forces acting on the left side undercarriage and the right forces acting on the right side undercarriage.

(30) The measurement system 30 may process these measurements in order to evaluate whether any asymmetry of the forces is present, or in order to transmit the measurements to the processor unit for this purpose.

(31) During a second stage STP2, if the landing gear is subjected to loading that is judged to be asymmetrical, the processor unit determines a recommended position for least one of the control means comprising the lateral cyclic pitch control means 6 and the yaw movement control means 8, with this being determined in particular as a function of the observed asymmetry.

(32) For this purpose, during an initialization stage, the manufacturer determines the influence of the lateral cyclic pitch control means 6 and of the yaw movement control means 8 on the asymmetry of the left and right forces. The manufacturer then determines the recommended positions to be applied in order to counter such asymmetry, e.g. by testing or by simulation.

(33) The results of this initialization stage are stored in the processor unit.

(34) During the initialization stage, the manufacturer may take into consideration the speed of rotation of the main rotor 3 and/or the speed of rotation of the yaw movement control rotor 4 when determining the influence of the yaw and lateral cyclic pitch control means 8 and 6 on the asymmetry of the left and right forces.

(35) Under such circumstances, if asymmetry is observed in the forces exerted on the left and right side undercarriages, the processor unit establishes the appropriate recommended positions for re-establishing symmetrical loading.

(36) It should be observed that the second stage may also be performed when the loading of the undercarriages is symmetrical. If the loading is symmetrical, the method then leads to at least one recommended position that is close to the current position of the controls.

(37) During a third stage STP3, the processor unit causes each determined recommended position to be displayed on the display unit 20. The pilot can then discover the positions to be reached by the control means in question for the purpose of keeping the aircraft within a domain of stability in terms of rolling on the ground.

(38) The calculation means 16 then execute instructions in order to determine the required recommended positions over time. The calculation means 16 then send orders to the display unit 20 to cause it to display symbols on the display screen 21, the symbols representing each of the recommended positions that are to be displayed.

(39) It should be observed that it is also possible to determine, and to display on the display unit 20, the current position of each control means for which a recommended position is being displayed.

(40) Consequently, if necessary, the processor unit may co-operate with dedicated sensors 65 for determining the current position of the lateral cyclic pitch control means 6. Likewise, if necessary, the processor unit may co-operate with sensors 80 for determining the current position of the yaw movement control means 8.

(41) The processor unit may also trigger an alert when asymmetrical loading is identified.

(42) With reference to FIGS. 4 to 7, the processor unit may determine and cause to be displayed a first recommended position 23 for the lateral cyclic pitch control means 6 and a second recommended position 25 for the yaw movement control means 8.

(43) With reference to FIG. 4, the display unit may comprise a strip 27 together with each recommended position.

(44) Consequently, the display unit displays a first symbol representing the first recommended position 23 and a second symbol representing the second recommended position 25. The first and second symbols move between the ends of the strip. These ends represent extreme values POS11, POS12, POS21, and POS22 of the lateral cyclic pitch control means 6 and of the yaw movement control means 8.

(45) Likewise, on request from the processor unit, the display unit may display a symbol representing the first current position 22 and a symbol representing the second current position 24.

(46) It can be understood that the term “position” is used herein to mean a position as such, or the value of a parameter representative of the position.

(47) In the variant of FIG. 7, the processor unit gives a two-dimensional representation in the form of a rectangle or a square.

(48) This representation has a horizontal first axis AX1 showing the position of the lateral cyclic pitch control means 6, and a vertical second axis AX2 showing the position of the yaw movement control means 8. By way of example, each control means may be capable of varying between a respective first extreme position POS11, POS21 and a respective second extreme position POS12, POS22.

(49) A symbol may represent the current position of the lateral cyclic pitch control means 6, and of the yaw movement control means 8. Crosshairs 100 may be used for this purpose.

(50) In addition, a single symbol 200 can be used to display the recommended position for the lateral cyclic pitch control means 6 and for the yaw movement control means 8. This single symbol optionally marks an area in order to cover all possible solutions.

(51) For the purpose of keeping the aircraft in a stable domain, the manufacturer may also give priority to a single one of the flight controls by displaying a recommended position on a scale, either for the lateral cyclic pitch control means or else for the yaw movement control means, as a function of whether the aircraft is moving relative to the ground.

(52) For example, in FIG. 5, the processor unit displays information relating only to the lateral cyclic pitch control means.

(53) For example, the processor unit determines whether the aircraft 1 is taxiing along the ground. The processor unit then causes only the recommended position for the lateral cyclic pitch control means to be displayed while the aircraft is taxiing, and possibly also the current position of the lateral cyclic control means.

(54) For this purpose, the processor unit may co-operate with members of the aircraft, such as means for determining the position of the aircraft, for example.

(55) The processor unit may also cause only the recommended position of the yaw movement control means to be displayed when the aircraft is not taxiing.

(56) In the variant of FIG. 6, the display unit may present a strip presenting various zones such as a high-risk zone Z3, an intermediate zone Z2, and a safe zone Z1 representing the recommended position for the lateral cyclic pitch control means.

(57) When the current position of the lateral cyclic pitch control means lies outside the safe zone Z1, it is possible to trigger a visible and/or audible alarm.

(58) With reference to FIG. 2, in an embodiment, the measurement system 30 co-operates with the measurement device 60 in order to take at least one measurement directly relating to the left forces exerted on the left side undercarriage and to the right forces exerted on the right side undercarriage.

(59) The measurement system may process the measurements in order to evaluate the presence of asymmetry in loading that needs to be corrected, or indeed to deliver the measurements taken to the processor unit 15.

(60) In another embodiment, the measurement system performs said at least one measurement concerning the left forces exerted on the left side undercarriage and the right forces exerted on the right side undercarriage indirectly by determining a roll angle of the aircraft.

(61) Furthermore, the processor unit 15 may make use of the data from the measurement means 55 in order to determine the initial roll angle of the aircraft prior to starting the main rotor.

(62) In a variant, the processor unit 15 requests the measurement means 55 to determine an initial maximum roll angle and an initial minimum roll angle reached during this period. The processor unit 15 can then inhibit the display of the recommended position for the yaw movement control means when the difference between the maximum initial roll angle and the minimum initial roll angle exceeds a threshold difference.

(63) Furthermore, after the main rotor has been started, the processor unit 15 uses the data from the measurement means 55 to determine the current roll angle of the aircraft.

(64) The manufacturer may also act during an initialization stage to determine the position that is to be reached by the yaw movement control means in order to generate a given roll angle.

(65) Thereafter, the processor unit determines and displays on the display unit 15 a recommended position 23, 25 for at least one of the yaw movement control and lateral cyclic pitch control means 8 and 6 so that the current roll angle tends towards said initial roll angle with the help of information that was stored during the initialization stage.

(66) When the roll angle has been measured over a given period on starting, it is possible for the initial roll angle to be the maximum initial roll angle, for example, or else the minimum initial roll angle, or indeed a mean roll angle corresponding to the average of the maximum initial roll angle and the minimum initial roll angle.

(67) Naturally, the present invention may be subjected to numerous variations as to its implementation. Although several embodiments are described, it will readily be understood that it is not conceivable to identify exhaustively all possible embodiments. It is naturally possible to envisage replacing any of the means described by equivalent means without going beyond the ambit of the present invention.

(68) For example, the landing gear described has three undercarriages. Nevertheless, that number is not limiting.

(69) For example, the landing gear could have four undercarriages. It would then be possible to evaluate the undercarriages in pairs, or indeed to measure the forces on all four undercarriages and derive therefrom an asymmetry index.