Abstract:
Method and device for implementing the thrust reversers of an aircraft. According to the invention, the following successive steps are carried out automatically: • deployment (E 3 ) of the previously armed thrust reversers of the aircraft; • application (E 5 ) of a predetermined engine speed; reduction (E 6 ) of the engine speed; —re-furling (E 7 ) of the thrust reversers of the aircraft.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a §371 national stage entry of International Application No. PCT/FR2009/000516, filed Apr. 30, 2009, which claims priority to French patent application Ser. No. 08/02511, filed May 6, 2008, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     This invention relates to a method and a device for operating the thrust reversers of an aircraft, as well as an aircraft provided with such a device. 
     BACKGROUND OF THE INVENTION 
     It is known that civil aircrafts equipped with turbojets are provided with thrust reversers being able to improve their braking, more specifically while reducing the running distance on the ground, upon a landing or a takeoff interruption. The thrust reversers are associated with aircraft engines and can be controlled for being able to switch from an inactive folded position to an active deployed position and, reversely, from said active deployed position to said inactive folded position. After having adapted the speed of the engines, the pilot can trigger manually the deployment of the thrust reversers associated with such engines through control members of the lever type. 
     However, the thrust reversers are likely to untimely deploy, for example, as a result of an accidental action of the pilot on one of the control members. Moreover, a bad positioning of the throttle lever of one of the engines, when the thrust reversers of the set of engines are deployed, or an erroneous control of the thrust of the engines, when the thrust reverser of one of the engines is defective, could generate a dissymmetry of the overall thrust of the engines and result in difficulties for controlling the aircraft on the ground. Moreover, a significant decision time interval between the aircraft wheels touching the ground and the deployment of the thrust reversers by the pilot reduces the contribution of the thrust reversers to the aircraft braking and can lead to runway excursions. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to remedy these drawbacks. 
     To this end, the method for implementing thrust reversers, upon a landing or a takeoff, of an aircraft provided with at least two turboengines, the speeds of which are individually controlled, between the idling speed and the full speed, by throttle levers respectively associated with said engines, said thrust reversers being controlled by at least one control member for being able to switch from an inactive folded position to an active deployed position and, reversely, from said active deployed position to said inactive folded position, is remarkable in that the following successive steps are automatically performed: 
     a) a deployment of said beforehand armed thrust reversers when:
         the speed of said engines is at the most equal to a predetermined low speed threshold;   the speed of the aircraft is higher than a first predetermined speed threshold; and   the aircraft is considered being in contact with the ground;       

     b) an application to said engines of a predetermined speed at least equal to said low speed threshold as long as the speed of the aircraft is higher than said first speed threshold; 
     c) as soon as the speed of said aircraft is at the most equal to said first speed threshold, a reduction of the speed of said engines so that they reach a speed at the most equal to said low speed threshold; 
     d) then, a folding of said thrust reversers. 
     Thus, thanks to this invention, the thrust reversers are automatically implemented, enabling to limit, or even to cancel the interventions of the pilot(s) upon the implementation of the reversers. The risk of human errors is then considerably reduced (untimely deployment/folding of the thrust reversers, unadapted thrust of the engines, etc.) upon such an implementation. 
     Moreover, the time interval between the wheels touching and the thrust reversers being deployed is nil or nearly nil, resulting in the braking distance being significantly reduced and therefore, the risk of the aircraft leaving the runway. 
     Preferably, said thrust reversers are folded when the speed of said aircraft is at the most equal to a second predetermined speed threshold, said second speed threshold being lower than said first threshold. 
     Additionally, said thrust reversers are armed if the following conditions are met:
         the pilot has selected a reverse thrust corresponding to said predetermined speed to be applied to the engines at step b);   the pilot has put the control member of said thrust reversers in a predefined position, referred to as the automatic position;   the aircraft is in one of the two following configurations:
           an approach configuration before a landing;   a takeoff configuration.   
               

     Advantageously, in the case of a breakdown of at least one of said thrust reversers, a new speed to be applied at step b) is determined for each one of said engines. 
     Thus, the reverse thrust dissymmetry generated by the defective thrust reverser is controlled and the controllability of the aircraft is improved. 
     Alternatively, in the case of a landing, the thrust reversers are armed if the following conditions are met:
         the pilot has recorded landing parameters;   the pilot has put the control member of said thrust reversers in a predefined position, referred to as the automatic position;   the aircraft is in an approach configuration;
 
and said speed to be applied to the engines at step b) is determined as a function of said recorded parameters and of the actual landing conditions so as to be optimal.
       

     Thus, when the pilot has for example programmed the desired runway exit bypass, the speed to be applied to the engines at step b) is determined automatically as a function of the wheels touching the runway with respect to the programmed exit bypass so as to adjust the braking of the aircraft. 
     Advantageously, before step b) is performed, the correct deployment of said thrust reversers is checked. 
     Furthermore, as a result of the pilot&#39;s voluntary action on at least one of the following means:
         the control member of said thrust reversers;   a throttle lever associated with one of said engines; at least one of the steps a), b), c), d) is interrupted.       

     Thus, the pilot has the possibility to stop the automatic implementation of the thrust reversers and to manually continue the thrust reversal. 
     Advantageously, said low predetermined speed threshold is at least approximately equal to the idle speed. 
     For implementing the method according to this invention, a control device is advantageously provided, comprising:
         a deployment logic device for controlling said deployment of the thrust reversers;   speed application logic devices each allowing said application of the predetermined speed to one of said engines to be controlled;   speed reduction logic devices each allowing said reduction of the speed of one of said engines to be controlled; and   folding logic devices each allowing said folding of the thrust reverser of one of said engines to be controlled.       

     Moreover, the control device comprises a position return logic device allowing said check of the correct deployment of said thrust reversers to be performed. 
     In addition, the control device is connected, via a link, to at least one of the following means of said aircraft:
         the flight controls;   the controls of the landing gear;   the flight data devices;   the throttle lever device;   the control member of said thrust reversers;
 
so as to receive signals representative of information able to be used by said logic devices for deployment, speed application, speed reduction, folding and position return.
       

     Preferably, the control device is connected, via a link, to a control interface connected to an electronic control for said engines and to a control unit for said thrust reversers, so as to receive from said control interface information signals being able to be used by said logic devices for speed application, speed reduction, folding and position return and to transmit to it control signals respectively from said engines and said thrust reversers. 
     Furthermore, the present invention relates to an aircraft provided with a control device such as specified herein above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The figures of the appended drawing will better explain how this invention can be implemented. On these figures, like reference numerals relate to like components 
         FIG. 1  illustrates the main steps of the method for automatically implementing the thrust reversers according to this invention upon an aircraft landing. 
         FIG. 2  schematically shows the simplified architecture of the system for automatically implementing the thrust reversers according to the invention. 
         FIG. 3A  shows, in the form of a block diagram, a deployment logic device integrated into the control device of the invention. 
         FIGS. 3B to 3E  are similar to  FIG. 3A  and respectively show the logic devices for position return, speed application, speed reduction and folding for the control device of this invention. 
         FIG. 4A  schematically illustrates, in a cross-sectional view, the control member implemented by this invention, when it is in a retracted position. 
         FIGS. 4B ,  4 C and  4 D are figures analogous to  FIG. 4A  when the control member is respectively occupying the automatic, full stroke and half-stroke positions. 
     
    
    
     DETAILED DESCRIPTION 
     Although in the embodiment in accordance with the invention, as herein after described, the aircraft is a two engine aircraft provided with thrust reversers, it will be easily understood that the system of the invention could also be arranged on a thrust reverser provided with a nozzle section varying device of the engine. 
     The speed of each one of the engines is individually controlled, between the idling speed and the full speed, by throttle levers respectively associated with said engines and actuated by the pilot(s). 
     In a preferred embodiment, the thrust reversers are controlled by means of a single control member  1 , an embodiment of which is schematically shown in different positions on  FIGS. 4A to 4D  to be subsequently described. 
     As shown on  FIG. 1 , the automatic implementation of the thrust reversers, referred to as the automatic mode, in accordance with the invention is as follows. 
     It is initially assumed that the aircraft is in an approach phase of a runway and in an approach configuration. The air brakes and the automatic brakes thereof are armed and the thrust reversers thereof are in an inactive folded position. The control member  1  occupies a predefined position ( FIG. 4A ), referred to as the retracted position. The automatic mode is not armed. 
     First of all, upon such an approach phase, the pilot selects (step E 1 ), via the flight management system known in the aeronautic art under the abbreviation FMS (for Flight Management System), the thrust he wants to obtain in outlet of the thrust reversers when they are n the active deployed position. In the embodiment, the pilot can select a level of reverse thrust amongst three levels (for example minimum, intermediary, maximum) each corresponding to a predetermined speed (for example idling speed, intermediary speed, authorized maximum speed). In order to select the reverse thrust, the pilot can, for example, take into consideration the weather conditions and the characteristics of the runway (for example, the programmed exit bypass of the runway). 
     When the reverse thrust has been selected (step E 1 ), the pilot activates the automatic mode (step E 2 ) while bringing the control member  1  in an automatic position ( FIG. 4B ). The thrust reversers are then armed. For deactivating the automatic mode before the wheels touch the ground, the pilot can, for example, put the control member  1  into the retracted position. 
     Upon the wheels touching the ground, when the speed of the aircraft Va is preferably higher than a first predetermined speed threshold Vs 1  (for example set at 70 kts) and the engines are at the idling speed (that is when the speed thereof is at the most equal to a low predetermined speed threshold), the deployment of the thrust reversers is controlled (step E 3 ). 
     A check of the incident free deployment of the thrust reversers is subsequently performed (step E 4 ). A deployment confirmation signal of the thrust reversers, in the case of a correct deployment thereof, can then be transmitted to the pilot, for example, in the form of a visual and/or a sound signal. On the other hand, in the case of an abnormal deployment of at least one of the thrust reversers of the aircraft, an incorrect deployment signal can be transmitted to the pilot. 
     When the deployment of the thrust reversers occurs correctly, the application of the predetermined speed to the engines is controlled (step E 5 ), said predetermined speed corresponding to the level of reverse thrust selected by the pilot at step E 1 . At step E 5 , the speed of the engines is maintained substantially equal to the predetermined speed as long as the speed of the aircraft remains for example higher than the first speed threshold. 
     It should be appreciated that, when the deployment of at least one of the reversers has not occurred correctly, a new speed to be applied at step E 5  is for example determined for each engine (including the engine with a defective thrust reverser), so as to check the reverse thrust dissymmetry generated by the defect of the reverser and to improve the controllability of the aircraft. The new speeds associated with each of the engines could be applied, as in the case of a correct deployment of the thrust reversers, as long as the speed of the aircraft remains higher than the first speed threshold. 
     As soon as the speed of the aircraft is at the most equal to said first speed threshold, the idling speed of the engines is controlled (step E 6 ). 
     When the engines reach the idling speed (the speed of the engines is then at the most equal to the low threshold speed) and the speed of the aircraft is at the most equal to a second predetermined speed threshold Vs 2  (for example, the second speed threshold is taken equal to 20 kts), folding of the thrust reversers of the aircraft is controlled (step E 7 ). 
     The automatic implementation of the thrust reversers according to the invention is completed when the thrust reversers of the engines are in an inactive folded position. 
     Upon a takeoff being interrupted, the aircraft being initially in a takeoff configuration, the automatic implementation of the thrust reversers comprises, like that upon a landing, the above mentioned steps E 1  to E 7 . It is however to be noticed that the steps wherein a reverse thrust E 1  is selected and the automatic mode E 2  is activated are performed preferably before the takeoff phase of the aircraft is initiated and step E 3  of deployment of the thrust reversers can be triggered by the pilot abruptly idling the engines. 
     Moreover, upon a landing or a takeoff interruption of the aircraft, after a voluntary action of the pilot on the control member  1  (for example, the control member is put in a predefined position, referred to as the half-stroke position, to be subsequently described with reference to  FIG. 4D ) or on one of the throttle levers, one of the steps E 3  to E 7  can be interrupted for switching back to a manual implementation of the thrust reversers. The automatic mode is then de-activated and the pilot can for example control maintaining a reverse thrust in outlet of the reversers under the first speed threshold. 
     As an alternative of the embodiment in accordance with the invention, the pilot could program, at step E 1 , the desired exit bypass of the runway so that a selection of the optimum reverse thrust level is automatically performed at step E 3  as a function of the actual landing conditions (for example, the position of the wheels touching the runway with respect to the programmed exit bypass, the weather conditions, etc.) and so that the corresponding speed is applied as long as the speed of the aircraft remains for example higher than the first speed threshold. 
     In the preferred embodiment of the invention, the pilot can also manually control, by means of the control member  1 , the deployment and the folding of the thrust reversers as well as the speed of the engines when the thrust reversers are in an active deployed position. 
     According to the invention, such a manual implementation of the thrust reversers, referred to as the manual mode, is as follows. 
     First of all, it is assumed that the aircraft is in an approach phase of a runway and is in an approach configuration. The air brakes and the automatic brakes thereof are armed and the thrust reversers thereof are in an inactive folded position (the control member  1  is in the retracted position). 
     When the wheels touch the ground, the engines of the aircraft preferably being at the idling speed, the pilot can actuate the deployment of the thrust reversers while bringing the control member  1  in the half-stroke position ( FIG. 4D ). 
     As soon as the thrust reversers are in an active deployed position, the pilot can control the speed of the engines, by means of the control member  1 , between the idling speed (the control member  1  is in the half-stroke position) and the authorized maximum speed when the thrust reversers are in an active deployed position (the control member  1  is occupying a full stroke position, to be further described referring to  FIG. 4C ) so as to check the braking of the aircraft. 
     When the speed of the aircraft is at the most equal to the first speed threshold, the pilot can control the folding of the thrust reversers. To this end, he first of all brings the control member  1  in the half-stroke position ( FIG. 4D ) so that the engines are at the idling speed. He then puts the control member  1  in the retracted position ( FIG. 4A ) so that the thrust reversers switch from the active deployed position to the inactive folded position. 
     It should be appreciated that, in the manual mode, the implementation of the thrust reversers upon a takeoff being interrupted is similar to the abovementioned one upon a landing. 
     As shown on  FIG. 2 , the control member  1  is able to generate electric signals being transmitted to a control device  2  implementing the method of the invention, via the link  10 . The control device  2  is preferably integrated into the flight management system FMS of the aircraft. 
     The control device  2  can also, but not exclusively receive the electric signals transmitted by the flight controls  3  of the aircraft, the landing gear controls  4 , the flight data devices  5  and the throttle lever device  6 , via the link  11  as illustrated on  FIG. 2 . It can further emit and receive electric signals from a control interface  7 , via the link  12 . 
     The control interface  7  can transmit and receive electric signals from an electronic control of the engines  8 , via the link  13 , and from a control unit of the thrust reversers  9 , via the link  14 . 
     In the embodiment, the control device  2  more specifically comprises the following logic devices, shown by the respective  FIGS. 3A to 3E  as block diagrams:
         a deployment logic device  15  ( FIG. 3A ) allowing the deployment (step E 3 ) of the thrust reversers to be controlled;   a position return logic device  20  ( FIG. 3B ) allowing (step E 4 ) the deployment of the thrust reversers to be checked;   a speed application logic device  22  ( FIG. 3C ) associated with each engine allowing (step E 5 ) the speed of said engine to be controlled while applying to it the predetermined speed corresponding to the reverse thrust being selected at step E 1 ;   a speed reduction logic device  24  ( FIG. 3D ) associated with each engine allowing the idling speed of said engine (step E 6 ) to be controlled; and   a folding logic device  26  ( FIG. 3E ) associated with each engine allowing the folding of the thrust reverser of said engine (step E 7 ) to be controlled.       

     As shown on  FIG. 3A , the deployment logic device  15  comprises a first AND logic gate  16  with five inputs and one output. The AND logic gate  16  can deliver a signal S 1  on the output thereof when a signal is received by each of its five inputs. In such a case, the signal S 1  is a control signal for the deployment of the thrust reversers being transmitted to a control interface  7  via the link  12 . 
     As an example, the first AND logic gate  16  can receive:
         a first signal S 2 , representative of the idling speed position of the throttle levers of the engines of the aircraft, on its first input. When at least one of the throttle levers is not occupying the idling speed, no signal reaches this first input;   a second signal S 3 , representative of the speed of the aircraft when it is higher than the first speed threshold, on its second input. No signal reaches the second input when the speed is at the most equal to the first speed threshold;   a third signal S 4 , representative of the armed condition of the air brakes and of the automatic brakes of the aircraft, on its third input being connected to the output of a second two input AND logic gate  17 . The signal S 4  is delivered in the output of the second AND logic gate  17  when a signal S 7  representative of the armed condition of the air brakes, and a signal S 8 , representative of the armed condition of the automatic brakes, are respectively received by the first and the second input of the AND logic gate  17 . In the absence of at least one of the signals S 7  or S 8 , no signal is delivered;   a fourth signal S 5 , representative of the contact of the aircraft with the ground, on its fourth input being connected to the output of a third three input AND logic gate  18 . The signal S 5  is delivered in the output of the third AND logic gate  18  when no signal S 9 , representative of the altitude of the aircraft when it is at the most equal to a predetermined altitude threshold (for example 5 feet), a signal S 10 , representative of the speed of the wheels of the main gear when it is higher than a third predetermined speed threshold (for example 72 kts), and a signal  511 , representative of the pressed condition of the main landing gear, are received respectively by its three inputs;   a fifth signal S 6 , representative of the armed condition of the thrust reversers of the aircraft, on its fifth input being connected to the output of a fourth three input AND logic gate  19 . The signal S 6  is delivered in the output of the fourth AND logic gate  19  when a signal  512 , representative of the automatic position occupied by the control member  1 , a signal S 13 , representative of the approach configuration of the aircraft, and a signal S 14 , representative of the selection by the pilot of a level of reverse thrust, are respectively received by its three inputs.       

     As shown on  FIG. 3B , the position return logic device  20  comprises a two input AND logic gate  21  delivering in the output a signal S 15  for confirming the deployment of the thrust reversers when two signals S 17  and S 18 , each representative of the deployed condition of the thrust reverser of an engine, respectively reach its two inputs. On the other hand, when at least one thrust reverser is not correctly deployed, an abnormal deployment signal S 16  of the thrust reversers is transmitted in the output of the AND logic gate  21 . 
     Moreover, as illustrated on  FIG. 3C , each speed application logic device  22  comprises a three input AND logic gate  23 . It can deliver on its output a signal S 19  when the signals S 15 , S 17  or S 18  (according to the associated engine of the logic device  22 ) and the signal S 12  are received by its three inputs. In such a case, the signal S 19  is a control signal for the speed to be applied to the engine associated with the logic device  22  for obtaining, in the output of the corresponding thrust reverser, the reverse thrust (step E 1 ) preselected by the pilot. 
     The signal S 19  is transmitted to the control interface  7  via the link  12 . 
     Moreover, as illustrated on  FIG. 3D , each speed reduction logic device  24  comprises a three input AND logic gate  25 . It can deliver in the output a signal S 20  when the signal S 17  or S 18  (according to the engine associated with the logic device  24 ), a signal S 21 , representative of the speed of the aircraft when it is at the most equal to the first speed threshold, and a signal S 22 , representative of the speed of the aircraft when it is higher than a fourth predetermined speed threshold (for example 3 kts), are received by its three inputs. In such a case, the signal S 20  is a control signal for reducing the speed of the engine associated with the logic device  24  so that such speed reaches the idling speed. The signal S 20  is transmitted to the control interface  7  via the link  12 . 
     Furthermore, as shown on  FIG. 3E , each folding logic device  26  comprises a four input AND logic gate  27 . It can deliver in its output a signal S 23  when:
         the signal S 17  or S 18  (according to the engine associated with the logic device  26 );   a signal S 24 , representative of the speed of the aircraft when it is at the most equal to the second speed threshold;   the signal S 22 ;   a signal S 25  or S 26  (according to the engine associated with the logic device  26 ), each representative of the speed of an engine when it is at the idling speed;
 
are respectively received by its four inputs. In such a case, the signal S 23  is a control signal for the folding of the thrust reverser of the engine associated with the logic device  26 . The signal S 23  is transmitted to the control interface  7 , via the link  12 , afterwards transferring such a folding control toward the control unit  9  of the thrust reversers, via the link  14 .
       

     As shown on  FIGS. 4A to 4D , the control member  1  comprises preferably a lever  28  being able to slide in a mobile guide  29  able to rotate around the axis orthogonal to the sectional plane crossing A. The lever  28  comprises, at the lower end thereof, a tenon  30  able to shift in a guiding opening  31  arranged in the structure of the control member  1 . The guiding opening  31  comprises a circular portion  31 A with a centre A and, at its left end, a radial notch  31 B wherein the tenon  30  could be housed. Thus, the lever  28  can have a rotation motion of a centre A, the tenon  30  then shifts in the circular portion  31 A of the guiding opening  31 , and a translation motion, the tenon  30  becoming housed in the radial notch  31 B. 
     In the preferred embodiment, the control member  1  can occupy the following positions:
         the retracted position ( FIG. 4A ), wherein the lever  28  is fully tilted to the right, the tenon  30  is in abutment against the left end of the circular portion  31 A of the guiding opening  31 . In the retracted position, the thrust reversers are in an inactive folded position;   the automatic position ( FIG. 4B ), wherein the lever  28  has been slightly drawn upwards by the pilot from the retracted position. The tenon  30  then becomes housed into the radial notch  31 B. The above-mentioned automatic mode is activated;   the full stroke position ( FIG. 4C ), wherein the lever  28  is fully tilted to the left. The tenon  30  is then in abutment against the right end of the circular portion  31 A of the guiding opening  31 . In the full stroke position, the thrust reversers are in an active deployed position and the speed of the engines reaches the authorized maximum when the reversers are deployed;   the half-stroke position, wherein the lever  28  occupies an intermediary position between the retracted position and the full stroke position. The tenon  30  is then for example at an equidistance from the two ends of the circular portion  31 A. In the half-stroke position, the engines are at the idling speed and the thrust reversers are in an active deployed position.