Abstract:
According to the invention, as a function of the altitude, the vertical speed and the heading of the aircraft, as well as of the deviation of the actual trajectory of the aircraft with respect to the automatic trajectory, a time interval (T) is determined, during which it is tolerable for said aircraft to be able to fly without any control command, both on the part of the stick ( 1 ) and on that of said automatic pilot ( 2 ) and an alert is emitted for the attention of the crew in the case where it is noted that the absences of manual piloting and of automatic piloting extend simultaneously over a duration at least equal to said tune interval (T).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a §371 national stage entry of International Application PCT/FR2009/000307, filed Mar. 23, 2009, which claims priority to French Patent Application 08/01637, filed Mar. 26, 2008, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     This invention relates to a method and device for detecting absences of manual piloting and automatic piloting of an aircraft, and to an aircraft provided with such a device. 
     BACKGROUND OF THE INVENTION 
     It is known that most of the aircrafts, in particular civil transport airplanes, are equipped with an automatic pilot for controlling the trajectory according to set points being preset by the crew. Such an automatic pilot has the major advantage of decreasing the work load on the crew by relieving them from a part of the navigation task, during most of the flight phases. It is further known that connecting and disconnecting the automatic pilot are carried out by a voluntary action of the crew. 
     However, under some particular circumstances (breakdown, disturbances, etc.), the automatic pilot is caused to be disconnected by itself. 
     Regardless of the cause of the automatic pilot disconnection, the crew is informed about it through one or more audible alarms, as well as through visual changes on the piloting interfaces. 
     But, in spite of such visual and audible alerting systems, many cases are reported where the crews do not become aware of the automatic pilot disconnection, so either:
         the crew must face high or particular stressing work load situations which may alter their attention abilities and cause them to neglect alarms, such as those of automatic pilot disconnection;   or a lack of comprehension within the crew in distributing the piloting task occurs;   or the alarm for the automatic pilot disconnection is masked by a simultaneous alarm of higher priority (for example an alarm indicating that the aircraft is coming out of its flight envelope).       

     Besides, the existence of flight control laws, which stabilise the aircraft trajectory, can contribute to give the illusion that the automatic pilot is still operating and not cause the crew to check the condition of the automatic pilot. 
     Of course, it is particularly dangerous for the aircraft not to be piloted either by the crew, or by the automatic pilot. 
     Thus, the object of the present invention is to specifically detect such a situation and to inform the crew about it. 
     SUMMARY OF THE -INVENTION 
     For that purpose, according to the invention, the method for detecting absences of manual piloting and automatic piloting in an aircraft provided with at least a stick for manually controlling roll and pitch and with an automatic pilot in which an automatic trajectory is programmed, is remarkable in that:
         depending on the altitude, the vertical speed and the heading of said aircraft, as well as the deviation of the actual trajectory of the aircraft with respect to the automatic trajectory, a time interval is determined, during which it is tolerable for said aircraft to be able to fly without any control command, both on the part of the stick and on that of said automatic pilot;   the absence of manual piloting by said stick is detected;   the absence of automatic piloting by said automatic pilot is detected; and   an alert is emitted for the attention of the crew of said aircraft in the case where it is noticed that said absences of manual piloting and automatic piloting last simultaneously over a period at least equal to said time interval.       

     For implementing this method, a device mounted on board said aircraft can include:
         calculating means, receiving information regarding at least the altitude, the vertical speed and the heading of said aircraft, as well as information regarding said automatic trajectory, said calculating means calculating a time interval during which it is tolerable for said aircraft to be able to fly without any control command, both on the part of the stick and on that of said automatic pilot;   first means for detecting the absence of manual piloting by said stick;   second means for detecting the absence of automatic piloting by said automatic pilot; and   means for emitting an alert for the attention of the crew in the case where said first and second detection means simultaneously detect the absence of manual piloting and the absence of automatic piloting for a period at least equal to said time interval calculated by said calculating means.       

     The presence and absence of manual piloting can be detected respectively by the presence and absence of a pilot hand on said stick. In this case, contactors or pressure sensors mounted to said piloting sticks can be used. 
     Alternatively, or in addition, the presence and absence of manual piloting respectively can be detected by the presence and absence of roll and pitch control commands from said stick. In this case, means for detecting said control commands are provided. 
     When detecting the presence and absence of manual piloting, both by the presence and absence of the pilot hand on the stick and by means detecting the roll and pitch control commands, it is advantageous to emit said alert when, although detecting the presence of the pilot hand on said stick, the absence of said roll and pitch control commands from said stick and the existence of a deviation between the aircraft trajectory and the trajectory being programmed in said automatic pilot are noted simultaneously. 
     Said means for emitting said alert for the attention of the crew can include an alerting device and a controlling device of said alerting device and said controlling device can be a counter which receives, to count it, said time interval calculated by said calculating means and which is initialised by logic means receiving, directly or indirectly, signals generated by said first and second means for detecting the manual piloting and automatic piloting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The figures of the appended drawing will help better understand how the invention can be implemented. In these figures, identical references designate similar elements. 
         FIG. 1  schematically illustrates, in a block diagram, a first embodiment of the present invention. 
         FIG. 2  is a block diagram of a second embodiment of the present invention. 
         FIGS. 3 and 4  illustrate two examples for implementing the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     On  FIG. 1 , there is schematically represented the piloting sticks  1  of the pilot and the co-pilot of an aircraft (not represented), as well as the automatic pilot  2  of the latter. The sticks  1  are connected to transducers  3  converting movements  4  of said sticks  1  into roll and pitch piloting commands  5  for said aircraft. The automatic pilot  2  is able to generate piloting commands  6  for the latter, based on a trajectory desired by the pilots they have programmed in said automatic pilot  2  as speed, altitude, heading data, etc. 
     Moreover,  FIG. 1  shows a block diagram of one exemplary device  10  implementing the invention. 
     Such device  10  includes:
         sensors  11 , such as contactors or pressure sensors, mounted to said sticks  1  and able to detect permanently the presence or absence of the pilots&#39; hands on the sticks respectively;   a detector  12 , connected to the sticks  1  and able to generate, at the output  13  thereof, a signal S 13  indicating that at least one of these sensors  11  detects the presence of a pilot&#39;s hand and, at the output  14  thereof, a signal S 14  indicative of the fact that none of the contactors  11  is detecting the presence of such a hand;   a detector  15 , connected to the automatic pilot  2  and able, on the one hand, to detect the enabled condition (presence of commands  6 ) or the disabled condition (absence of commands  6 ) of the latter and, on the other hand, to generate, at the output  16  thereof, a signal S 16  indicating that the automatic pilot  2  is enabled and, at the output  17  thereof, a signal S 17  indicating that the automatic pilot  2  is disabled;   a logic gate  18  of the AND type directly receiving at the inputs thereof said signals S 14  and S 17  and able to deliver, at the output  19  thereof, a signal S 19  indicating that no pilot&#39;s hand is located on a stick  1  (namely said sticks are disabled) and the automatic pilot  2  is disabled itself;   a counter  20 , the countering start of which is controlled by said signal S 19  and the reset of which is controlled by any of the signals S 13  (coming from the detector  12 ) and S 16  (coming from the detector  15 ), said counter  20  being able to generate, at the output  21  thereof, a countering end signal S 21 ;   a calculator  22 , receiving several pieces of information  23  about the current condition of the aircraft, such as altitude, speed, vertical speed, heading, etc. as well as information  24  regarding the trajectory TR 2  programmed by the pilots in the automatic pilot  2 . For the latter purpose, the automatic pilot  2  and the calculator  22  are connected through a line  25 . From the information  23  and  24 , the calculator  22  can thus calculate the current deviation e (see  FIG. 4 ) of the current trajectory TRa with respect to said trajectory TR 2 , programmed in the automatic pilot  2 . Depending on the information  23  and said current deviation e, the calculator  22  calculates a counting time T which it addresses to said counter  20 ; and   an alerting device  26 , controlled by said signal  521  of the counter  20 .       

     Thus, when the signal S 19  appears at the output  19  of the gate  18  (which indicates that the sticks  1  and the automatic pilot  2  are simultaneously disabled), the counter  20  starts counting time T, calculated by the calculator  22 . Therefore, there are two options:
         if during the counting of the time T by the counter  20 , at least one of said signals S 13  and S 16  appears (which respectively means that one the sticks  1  is enabled again or that the automatic pilot  2  has become enabled again), the counter  20  stops counting the time T and is reset;   on the contrary, if during said counting, none of said signals S 13  or S 16  appears, the counter  20  counts time T until the end and, at the end of said counting, it addresses the signal S 21  to the alerting device  26 , which generates a suitable alert for the attention of the pilots.       

     Thus, said alert is emitted when:
         the automatic pilot has been disabled (disconnected) since the time interval T; and   none of the pilots on board has been manually acting on his/her stick  1  since this time interval T.   In the alternative embodiment  30  of the device in accordance with the present invention, represented on  FIG. 2 , the elements  1 - 6  and  11 - 26  described with reference to  FIG. 1  are present again. However, this device  30  further includes:   a detector  31 , connected to the transducers  3  and able to detect the roll and pitch commands  5  generated by the sticks  1  and to generate, at the output  32  thereof, a signal S 32  indicating that the detector  31  detects the presence of commands  5  and, at the output  33  thereof, a signal S 33  indicating that no command is detected;   a logic gate  34  of the AND type receiving the signals S 13  and S 32  and delivering, at the output  35  thereof, a signal S 35  indicating that at least one of the sticks  1  is held in hand by a pilot and that the result is a command  5  appearing. The signal S 35  is addressed to the counter  20 , in place of the signal S 13  as shown on  FIG. 1 ;   a logic gate  36  of the AND type receiving the signals S 14  and S 33  and delivering, at the output  37  thereof, a signal S 37  indicating that no stick  1  is held in hand by a pilot and no command  5  is generated by the transducers  3 ;   a logic gate  38  of the AND type receiving the signals S 13  and S 33 , as well as, through line  39 , the trajectory deviation e calculated by the calculator  22 , and delivering, at the output  40  thereof, a signal S 40  indicating that, even though at least one stick  1  is held in hand by a pilot, there is no command  5  at the output of the transducers  3  and a trajectory deviation occurs; and   a logic gate  41  of the OR type receiving said signals S 37  and S 40  and applying either of these signals to one of the inputs of the gate  18  (in place of the signal S 14  as shown on  FIG. 1 ) the other output of which receives (as previously set out), the signal S 17 .       

     Thus, the gate  18  is directly connected to the detector  15 , but indirectly (through the gates  36 ,  38 ,  41 ) to the detectors  12  and  21 , and the signal S 19 , appearing at the output  19  of said gate  18  and triggering counting by the counter  20  indicates:
         either that, simultaneously, no stick  1  is held in hand by a pilot and no roll or pitch command  5  appears at the output of the detector  31 ;   or that, even though at least one of the sticks  1  is held in hand by a pilot, no roll or pitch command  5  appears at the output of the detector  31 , while a trajectory deviation e occurs.       

     Thus, unless the counting carried out by the counter  20  is stopped due to at least one pilot holding again a stick  1  in hand (signal S 35 ) or unless the automatic pilot  2  becomes enabled again, the device  26  emits an alert when the following conditions are met:
         the automatic pilot  2  is disconnected since the time interval T, calculated by the calculator  22 ;   none of the pilots manually acts on the stick  1  during this time interval T:   either because the sensors  11  detect the absence of a pilot&#39;s hand on a stick  1  and the detector  31  detects the absence of a pitch and roll command  5 ;   or because, even though the sensors  11  detect the presence of at least one pilot&#39;s hand on a stick  1 , the detector  31  detects no pitch and roll command  5 , while the calculator  22  notes a deviation e of the current trajectory TRa from the trajectory TR 2  programmed in the automatic pilot  2 .       

       FIGS. 3 and 4  illustrate two situations (among others but not shown) wherein the present invention contributes to improving flight safety. 
     On  FIG. 3 , there is shown an aircraft AC, on board of which is mounted one of the devices  10  or  30  described above. The aircraft AC is about to land onto a runaway R. The automatic pilot  2  thereof is connected and the landing gear thereof is extended. At the time to, the automatic pilot  2  is disconnected and the crew does not become aware of it for at least one of the reasons recited above. The device  10  or  30  detects this abnormal situation and estimates a time interval T at the end of which (time t 1 ) an alert is emitted by the device  26  if the crew has still not taken control  1  again or reconnected the automatic pilot  2 . In this precise case, it is needless to say that the time interval T assessed by the calculator  22  is short because the altitude of the aircraft AC is low and its rate of descent is high. 
     In the example of  FIG. 4 , the aircraft AC is in a cruise phase, the automatic pilot  2  is connected for controlling the trajectory TR 2 . For at least one of the reasons recited above, at the time t 0 , the automatic pilot  2  is disconnected and the crew does not become aware of it. 
     The aircraft AC gradually deviates from the trajectory TR 2  programmed in the automatic pilot  2  to continue on a rectilinear trajectory TRa: the device  10  or  30  detects this abnormal situation and assesses a time interval T at the end of which (time t 1 ) an alert is emitted by the device  26  if the crew has still not taken the control  1  again or reconnected the automatic pilot  2 . In this precise case, the time interval T assessed by the calculator  22  is even shorter given that the deviation e from the trajectory TR 2  intended by the automatic pilot  2  is larger.