Abstract:
A display system of an aircraft, including a flare guiding cue and related method are provided. The display system includes a display unit; and an assembly for generating a display on the display unit, configured to dynamically display, on the display unit, at least one horizon line, a slope scale of the aircraft relative to the horizon line, and a speed vector symbol, representative of the slope of the aircraft relative to the horizon line. The display generator is configured to display, upon approaching a landing strip, a flare guidance symbol, the position of the flare guidance symbol on the display unit depending on the topographical slope of the approached landing strip.

Description:
[0001]    This claims the benefit of French Patent Application FR 15 01309, filed Jun. 24, 2015 and hereby incorporated by reference herein. 
         [0002]    The present invention relates to a display system of an aircraft, comprising:
       a display unit;   an assembly for generating a display on the display unit, able to dynamically display, on the display unit, at least one horizon line, a slope scale of the scope of the aircraft relative to the horizon line, and a speed vector symbol, representative of the slope of the aircraft relative to the horizon line.       
 
         [0005]    Such a system is designed to be installed in the cockpit of an aircraft to be associated with a display unit of the cockpit. The display unit is for example an at least partially transparent display unit, such as a semitransparent screen placed in front of a windshield of the cockpit, a system for projecting images on the windshield of the cockpit, a semitransparent sunshade, a helmet visor, or a semitransparent glass close to the eye. 
         [0006]    The display system is intended to facilitate piloting during landing of an aircraft on non-horizontal terrain. 
       BACKGROUND 
       [0007]    Known display systems simultaneously display a horizon line, and a speed vector symbol that allow the pilot to view the slope of the aircraft easily. 
         [0008]    During the landing of aircraft, the pilot uses the displayed horizon line to position the slope of the aircraft relative to the runway. He gradually raises the speed vector symbol relative to the horizon line, during the flare phase, above the runway, so as to place the speed vector symbol below the horizon line, at a predetermined distance therefrom corresponding to a target slope, for example approximately 1° below the horizon line, before touching down with the wheels. Such a maneuver generally smooths the touch down of the aircraft on the runway, which is favorable to the safety and comfort of the passengers. 
         [0009]    To guide the pilot in the start and the follow-up of the flare manoeuver, it is usual to display, in the final phase of the approach, a flare guide symbol which for example is placed under the speed vector symbol. 
         [0010]    When the flare has to be started, the flare guide symbol changes position and/or appearance, indicating the pilot that it would be adequate to lift the speed vector relative to the horizontal line to smooth the touch-down. 
       SUMMARY OF THE INVENTION 
       [0011]    Such a maneuver works well on a flat landing strip. However, in some cases, the landing strip has a slope that may reach up to 10°. 
         [0012]    In the case where the slope of the runway is positive at the runway threshold, the start of the flare manoeuver by the pilot may be too late to compensate for the greater angle formed between the speed vector of the aircraft and the axis of the runway. Consequently, the touchdown of the aircraft may be relatively hard, which is detrimental to passenger comfort. 
         [0013]    Conversely, when the slope of the runway is negative, the flare maneuver done by the pilot may be too premature. The aircraft therefore touches down further on the runway, which creates a risk of go around, or even going off the runway. 
         [0014]    One aim of the invention is therefore to provide an aircraft display system that makes it possible to carry out a flare ensuring a comfortable touch down for passengers, at the desired point, irrespective of the topographical configuration of the landing strip. 
         [0015]    To that end, the invention provides a system of the aforementioned type, characterized in that the display-generating assembly is able to display, upon approaching a landing strip, a flare guidance symbol, the position of the flare guidance symbol on the display unit depending on the topographical slope of the approached landing strip. 
         [0016]    The system according to the invention may comprise one or more of the following features, considered alone or according to any technically possible combination:
       the flare guidance symbol is able to notify the crew that a beginning of flare maneuver position has been reached, preferably a start height of the flare maneuver, the beginning of flare maneuver position being determined taking into account the topographical slope of the landing strip;   the display-generating assembly includes an application for calculating the start position of the flare maneuver, as a function of a topographical slope determined from at least one piece of topographical information from a database characteristic of the landing strip;   the calculating application is able to query a database of landing strips, the database comprising at least one piece of topographical information corresponding to each landing strip;   the database includes a first piece of topographical information for the runway threshold altitude, a second piece of topographical information for the end-of-runway altitude, and a third piece of topographical information for the runway length, the topographical slope being calculated as a function of the first piece of topographical information, the second piece of topographical information, and the third piece of topographical information;   the display-generating assembly is able to signal reaching the beginning of flare maneuver position by placing the flare guidance symbol to coincide with the speed vector symbol;   before the beginning of flare maneuver position, the display-generating assembly is able to display the flare guidance symbol below the speed vector symbol and to bring it vertically closer to the speed vector symbol until the beginning of flare position;   the display-generating assembly is able to bring the flare guidance symbol closer to the horizon line, according to a control law representative of a vertical speed increase profile during the flare, the control law taking into account the topographical slope of the landing strip;   the control law is able to make it possible to reach a target vertical speed for the end of flare, calculated as a function of the topographical slope of the landing strip;   the display-generating assembly comprises a module for recovering data from a sensor measuring a height of the aircraft relative to the landing strip, the display-generating assembly being able to determine the topographical slope of the landing strip from data from the sensor measuring the height of the aircraft;   the actual slope of the aircraft corresponds to a target slope of the aircraft according to the control law when the flare guidance symbol coincides with the speed vector symbol;   it comprises an automatic pilot module, able to actuate the controls of the aircraft to enslave the position of the speed vector symbol to the position of the flare guidance symbol to cause the aircraft to follow an increasing vertical speed profile according to the control law;   the display unit is an at least partially transparent display unit, such as a semitransparent screen placed in front of a windshield of the cockpit, a system for projecting images on the windshield of the cockpit, a semitransparent sunshade, a helmet visor or a semitransparent glass close to the eye;   the display-generating assembly is able to dynamically display, on the display unit, at least one horizon line and a slope scale of the slope relative to the horizon line, and upon approaching a landing strip, the display-generating assembly is able to create, on the horizon line, a region that is deformed as a function of the topographical slope of the landing strip approached by the aircraft;   the display-generating assembly includes an application for calculating a local deformation of the horizon line in the deformed region, as a function of a topographical slope determined from at least one piece of topographical information characteristic of the landing strip, the topographical information coming from a database or being measured;   in a first movement phase of the aircraft at a distance from the landing strip, the display-generating assembly is able to calculate the local deformation of the horizon line in the deformed region as a function of a topographical slope determined from at least one piece of topographical information from a database, in a second movement phase of the aircraft above the landing strip, the display-generating assembly is able to calculate the local deformation of the horizon line in the deformed region as a function of a topographical slope determined from a measured piece of topographical information;   the database includes a topographical slope profile along the landing strip, the topographical slope being determined along the landing strip from the topographical slope profile;   the calculating application is able to recover data from a sensor measuring the slope of the airplane and a sensor measuring a height of the aircraft relative to the ground, and to calculate a topographical slope, based on data received from the sensor measuring the airplane slope and the sensor measuring the height of the aircraft relative to the ground;   the display-generating assembly is able to display, on the display unit, a speed vector symbol, indicating the slope of the aircraft on the slope scale, the width of the deformed region on the horizon line able to be displayed by the display-generating assembly being greater than the width of the speed vector symbol;   the deformed region on the horizon line, able to be displayed by the display-generating assembly, is horizontally centered on the speed vector symbol;   the deformed region on the horizon line able to be displayed by the display-generating assembly is in the form of an indentation, having a height, considered relative to the horizon line, depending on the topographical slope of the landing strip;   the deformed region on the horizon line able to be displayed by the display-generating assembly has a curved shape, in particular a bump shape, the curved shape having an apex at a height, considered relative to the horizon line, depending on the topographical slope of the landing strip;   the display-generating assembly is able to display a flare guidance symbol horizontally across from the deformed region;   when the topographical slope of the landing strip is non-null and positive, the deformed region of the horizon line created by the display generating assembly extends upward, and wherein when the topographical slope of the landing strip is non-null and negative, the deformed region of the horizon line created by the display-generating assembly extends downward.       
 
         [0040]    The invention also provides a display method in an aircraft comprising the following steps:
       providing a system as described above;   dynamically displaying, on the display unit via the display-generating assembly, a horizon line and a speed vector symbol;   upon approaching a given landing strip, dynamically displaying, on the display unit via the display-generating assembly, a flare guidance symbol, the position of the flare guidance symbol depending on the slope of the approached landing strip.       
 
         [0044]    The method according to the invention may comprise one or more of the following features, considered alone or according to any technically possible combination:
       the flare guidance symbol is able to notify the crew that a beginning of flare maneuver position has been reached, preferably a start height of the flare maneuver,   the beginning of flare maneuver position being determined by the display-generating assembly while taking into account the topographical slope of the landing strip;   it comprises the following steps:   upon approaching a given landing strip, dynamically displaying, on the display unit, via the display-generating assembly, a flare guidance symbol, the position of the flare guidance symbol depending on the slope of the approached landing strip;   the generating step comprises calculating a local deformation of the horizon line in the deformed region, as a function of at least one piece of topographical information characteristic of the landing strip from the database or that is measured.       
 
     
    
     
       BRIEF SUMMARY OF THE DRAWINGS 
         [0050]    The invention will be better understood upon reading the following description, provided solely as an example, and done in reference to the appended drawings, in which: 
           [0051]      FIG. 1  is a diagrammatic view of a first display system of an aircraft according to an embodiment of the invention; 
           [0052]      FIG. 2  diagrammatically illustrates the cockpit of an aircraft comprising the first display system; 
           [0053]      FIGS. 3 to 7  illustrate the display created by the display system when the aircraft is approaching a landing strip; 
           [0054]      FIG. 8  is a diagrammatic side view, illustrating the apparent slope of the aircraft relative to the runway, for a runway having a positive slope; 
           [0055]      FIG. 9  is a view similar to  FIG. 8 , for a runway with a negative slope; 
           [0056]      FIG. 10  is a diagrammatic side view, illustrating two successive points of the trajectory of the aircraft relative to a runway with a positive slope; 
           [0057]      FIG. 11  is a view similar to  FIG. 4 , during movement with a cross-wind; 
           [0058]      FIG. 12  is a view similar to  FIG. 4 , illustrating the display by a system according to an alternative embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0059]    A first display system  10  of an aircraft  12  according to an embodiment of the invention is diagrammatically illustrated by  FIGS. 1 and 2 . 
         [0060]    The system  10  is intended to be installed in an aircraft  12 , diagrammatically shown in  FIG. 8 , to allow the display of information on a display unit present in the cockpit  14  of the aircraft shown diagrammatically in  FIG. 2 . 
         [0061]    The system  10  is intended to assist the pilot of the aircraft during an approach phase, near a runway  13 , shown diagrammatically in  FIG. 8 . 
         [0062]    In reference to  FIG. 2 , the cockpit  14  is provided with a primary display system  22  connected to a central avionics unit  20 . 
         [0063]    The primary system  22  allows the crew to pilot the aircraft, manage its navigation, and monitor and control the various functional systems present in the aircraft. The system  22  includes a dashboard provided with a plurality of base monitors  24 A to  24 D forming head down monitors. 
         [0064]    In this example, the cockpit  14  is also advantageously provided with at least one head up semitransparent monitor  26 , placed across from the windshield, or even two semitransparent head up monitors  26 . 
         [0065]    The cockpit  14  is further provided with a control member  28  for the piloting of the aircraft, such as a lever or a control stick. 
         [0066]    It advantageously includes an automatic pilot system  29  able to be activated by the crew. 
         [0067]    In a known manner, the base monitors  24 A and  24 C are for example primary display monitors intended to display flight parameters of the aircraft. The base monitors  24 B and  24 D are for example multifunctional navigation and/or monitoring and control monitors for avionics systems. 
         [0068]    The primary display system  22  is provided with a display management assembly able to display the different windows present on these monitors  24 A to  24 D. 
         [0069]    The central avionics unit  20  is connected to a system  30  of measuring sensors for measuring airplane parameters of the aircraft  12 . 
         [0070]    The measuring sensor system  30  for example includes sensors for measuring parameters outside the aircraft such as the temperature, pressure or speed, sensors for measuring parameters internal to the aircraft and its various functional systems, and position sensors, such as geographical position sensors  31 , in particular a GPS sensor, sensors  32  for determining the slope of the aircraft, in particular at least one inertial unit, and a sensor  33  for determining a height relative to the ground, in particular a radio altimeter. 
         [0071]    The sensors of the system  30  are able to provide information on the geographical position of the aircraft  12 , its speed, its heading and its altitude (pitch attitude, roll angle). 
         [0072]    In reference to  FIG. 1 , the display system  10  is connected to the measuring sensor system  30 . 
         [0073]    The display system  10  includes at least one display unit  36 , and a display generator in the form of a display-generating assembly  38  on the display unit  36 , connected to the display unit  36  and to the system of measuring sensors  30 . The system  10  further includes a man/machine interface  40 . 
         [0074]    The display unit  36  is for example one of the monitors  24 A to  24 B and/or is the head up semitransparent monitor  26  of the cockpit  14 . In other alternatives, the display unit  36  is for example a projector or system for projecting images on the windshield of the cockpit, a semitransparent sunshade, a helmet visor or a semitransparent glass close to the eye. 
         [0075]    In a first embodiment, which will be described below, the display unit  36  of the display system  10  is the head up semitransparent monitor  26  of the cockpit  14 . 
         [0076]    The display-generating assembly  38  includes at least one processor  42  and at least one memory  44  containing a plurality of software modules able to be executed by the processor  42 . It includes a database  46  of landing strip characteristics, for example stored in the memory  44 . 
         [0077]    The display-generating a simply  38  includes a data recoverer in the form of a module  48  for recovering data from the measuring sensors of the system  30 , in particular a sensor  32  for measuring the slope of the aircraft  12 , and the sensor  33  for measuring the height of the aircraft  12  relative to the ground. 
         [0078]    The display-generating assembly  38  further includes a module  47  for generating a model symbol  49  of the aircraft, a module  50  generating an artificial horizon line  52 , and an associated module  54  for generating a slope scale  56 . 
         [0079]    The display-generating assembly  39  also comprises a module  58  for generating a speed vector symbol  60 , and a module  62  for generating a flare guidance symbol  64 , shown in  FIGS. 5 to 7 . 
         [0080]    The display-generating assembly  38  further includes modules for generating other symbols representative of flight parameters, for example in altitude indicator, an airspeed indicator, a vertical speed indicator, a ground speed indicator, an engine information indicator, and a suspension configuration indicator of the aircraft. 
         [0081]    The generating module  47  is able to create the display of an airplane model symbol  49  that embodies an infinite projection of the longitudinal axis of the aircraft  12 , from data received from the sensors of the measuring sensor system  30 . 
         [0082]    The generating module  50  is able to determine, from data received from the sensors of the measuring sensor system  30 , the position of an artificial horizon line  52  relative to the current attitude of the aircraft. This horizon line  52  is straight when the aircraft  12  moves with wings level, and tilts as a function of the tilt angle of the aircraft  12 . 
         [0083]    In at least one approach phase of the aircraft  12  toward the landing strip  13 , the module  50  is able to create, on the horizon line  52 , a deformed region  70  as a function of the topographical slope of the landing strip  13 . 
         [0084]    In the example illustrated in  FIG. 4 , the deformed region  70  is a region of the horizon line  52  centered on the speed vector symbol  60 . It has an indentation shape with a segment  71  parallel to the rest  75  of the horizon line  52 , and two connecting segments  73  that are inclined or perpendicular relative to the rest  75  of the horizon line  52 . 
         [0085]    In an alternative illustrated by  FIG. 11 , the deformed region  70  has a curved shape, for example a bump shape. The curved shape has an apex at a height, considered relative to the rest  75  of the horizon line  52 , depending on the topographical slope of the landing strip  13 . 
         [0086]    The deformed region  70  extends upward when the topographical slope of the landing strip  13  is positive. It extends downward when the topographical slope of the landing strip  13  is negative. 
         [0087]    In reference to  FIG. 1 , the generating module  50  includes a calculator in the form of a software application  72  for calculating a local deformation of the horizon line  52  in the deformed region  70 , as a function of the topographical slope of the landing strip  13 . 
         [0088]    “Topographical slope” refers to the actual slope of the landing strip  13  on the terrain. 
         [0089]    The deformation of the deformed region  70  is characterized here by its maximum height, considered vertically relative to the rest of the horizon line  52 . 
         [0090]    The calculating application  72  is able to recover at least one piece of topographical information characteristic of the runway  13 , from a database or that is measured, and to calculate the deformation of the deformed region  70  as a function of the piece(s) of characteristic topographical information. 
         [0091]    Advantageously, in the first movement phase of the aircraft  12  axially at a distance from the landing strip  13 , the calculating software application  72  is able to recover at least one piece of topographical information from the database of landing strips  46 , then to calculate the local deformation of the horizon line  52  in the deformed region  70  as a function of the or each piece of topographical information from a database. 
         [0092]    The piece of topographical information from a database is for example the altitude at a given point of the runway and/or the length of the runway. The database  46  for example includes, for each runway  13 , the altitude of the runway threshold, the altitude of the end of the runway and the length of the runway. 
         [0093]    The calculating software application  72  is then able to calculate an estimated slope of the runway  13  based on the altitude of the runway threshold, the altitude of the end of the runway and the length of the runway. 
         [0094]    In one alternative, topographical information from a database contained in the database  46  is directly the topographical slope in the touchdown zone around the target touchdown point. 
         [0095]    In a second movement phase of the aircraft  12  above the landing strip  13 , the calculating software application  72  is able to continuously calculate a piece of measured characteristic topographical information of the runway  13 , as a function of the data from the sensors  31 ,  33  for measuring the airplane slope and the height of the aircraft relative to the ground recovered by the data recovery module  48 . 
         [0096]    In reference to  FIG. 10 , this piece of topographical information is a calculated slope I and is determined to be delivered from measurements collected at two successive points P 1 , P 2  of the aircraft&#39;s trajectory  12  at successive passage times t 1 , t 2 , and in particular heights h 1 , h 2  measured at the points P 1 , P 2 , of the airplane slope measured between the points P 1  and P 2 , and the horizontal speed VH of the aircraft  12 . 
         [0097]    The local topographical slope I of the runway is for example estimated by the following equations: 
         [0000]      Δ=arctan [( h 2− h 1)/( VH ×( t 2− t 1)]  (1)
 
         [0000]        I=γ−Δ   (2).
 
         [0098]    The maximum height of the deformed region  70  is then calculated by the calculating application  72  to correspond to the value of the topographical slope, from a database or measured, of the landing strip  13 , taken on the slope scale  56  created by the module  54 . 
         [0099]    For example, if the topographical slope, from a database or measured, is N degrees, the maximum height of the deformed region  70  relative to the rest  75  of the horizon line  52  is N degrees on the slope scale  56  created by the module  54 . 
         [0100]    In the first movement phase of the aircraft  12  at a distance from the landing strip  13 , the height of the deformed region  70  remains constant. In a second movement phase of the aircraft  12 , above the landing strip  13 , the height of the deformed region  70  evolves continuously as a function of the local topographical slope of the runway  13  below the aircraft  12  measured using sensors of the system  30 . 
         [0101]    In this example, the deformed region  70  created by the module  50  is centered relative to the slope scale  56 , and relative to the speed vector symbol  60 . 
         [0102]    The deformed region  70  here has a width larger than that of the speed vector symbol  60 , and preferably, larger than that of the end of the landing strip  13 . 
         [0103]    The width of the deformed region  70  nevertheless preferably remains smaller than 80%, advantageously smaller than 50% of the total width of the horizon line  52 . 
         [0104]    The width of the deformed region  70  is for example greater than that of the speed vector symbol  60 , and less than two times the width of the speed vector symbol  60 . 
         [0105]    The width of the landing strip  13  is obtained from the database  46 . 
         [0106]    The deformed region  70  is therefore localized. It follows the lateral movement of the speed vector symbol  60  as illustrated by  FIG. 11 , during a crosswind movement. 
         [0107]    The generating module  54  is able to create a slope scale  56  centered horizontally on the rest  75  of the horizon line  52 , away from the deformed region  70 . The slope scale  56  is for example graduated in slope degrees relative to the artificial horizon line  52 , taken at a distance from the deformed region  70 . 
         [0108]    The generating module  58  is able to create the display of a speed vector symbol  60  indicating the direction of the speed vector of the aircraft  12 , based on data received from the sensors of the system  30 . The vertical separation between the artificial horizon line  52 , at a distance from the deformed region  70 , represents the ground slope γ of the aircraft, as illustrated in  FIG. 8 , considered relative to a non-inclined ground. 
         [0109]    The vertical separation between the deformed region  70  and the speed vector symbol  60  then represents the visible ground slope γ R  of the aircraft  12  relative to the landing strip  13 , taking into account the topographical slope I of the landing strip  13  (see  FIG. 8 or 9 ). 
         [0110]    The generating module  62  is able to create the display of the flare guidance symbol  64 , at the end of approach toward the landing strip  13 . 
         [0111]    It is able to display the flare guidance symbol  64  to notify the crew that a beginning of flare maneuver position has been reached, preferably of a flare maneuver beginning height. The beginning position of the flare maneuver is determined taking into account the topographical slope I of the landing strip  13 . 
         [0112]    The beginning of flare maneuver position is determined by the generating module  62  as a function of a piece of topographical slope information coming from a database for the landing strip  13 , determined using the database of landing strips  46 , via a calculating application  72  as described above, either using the threshold and end of runway altitudes and the runway length contained in the database  46 , or directly using a slope contained in the database  46 . 
         [0113]    The beginning of flare maneuver position is determined also taking into account the measured airplane slope γ. 
         [0114]    Advantageously, the generating module  62  includes a database of beginning of flare maneuver heights, as a function of the airplane slope γ measured by the sensor  32  and the topographical slope I of the landing strip  13 , as determined by the calculating application  72 , in particular as a function of the apparent slope γ R  calculated from the airplane slope γ and the topographical slope I. 
         [0115]    The generating module  62  is able to signal that the beginning of flare maneuver height has been reached by placing the flare guidance symbol  64  in register with the speed vector symbol  60 . Preferably, to indicate that the aircraft  12  has reached the beginning of flare height, the flare guidance symbol  64  is positioned at the same horizontal level as the speed vector symbol  60 , horizontally coinciding with the latter, preferably in a receiving zone  110  of the speed vector symbol  60  embodied here by a circle defining the desired slope of the aircraft. 
         [0116]    To allow the pilot to anticipate reaching the beginning of flare maneuver position, the generating module  62  is advantageously able to display the flare guidance symbol  64  below the speed vector symbol  60  before reaching the beginning of flare maneuver position and to bring it vertically closer to the speed vector symbol  60  so as to reach the speed vector symbol  60  at the beginning of flare maneuver position. 
         [0117]    Once the beginning of flare maneuver position has been reached, the generating module  62  is able to bring the flare guidance symbol  64  closer to the horizon line  52  according to a control law representative of an increase profile for the vertical speed during flare. 
         [0118]    The control law for example connects, for each apparent slope γ R  of the aircraft  12  relative to the landing strip  13 , a height relative to the landing strip  13  with a target vertical speed. The control law makes it possible to go from a first beginning of flare vertical speed, when the aircraft  12  reaches the beginning of flare maneuver height, to a second target end of flare vertical speed greater than the first vertical speed when the aircraft reaches the end of flare before the wheels touch down. It accounts for the topographical slope of the landing strip  13 . 
         [0119]    Preferably, the second target end of flare vertical speed, which applies to the end of flare, is calculated as a function of the topographical slope of the landing strip  13 . 
         [0120]    The generating module  62  is able to determine, at each moment, the second target vertical speed as a function of the topographical slope of the landing strip  13 . The topographical slope is initially estimated using topographical information from a database as described above, then is obtained by calculation using height data and slope data respectively measured using sensors  33  and  32 , as indicated above. 
         [0121]    According to the control law, the flare guidance symbol  64  is moved relative to the horizon line  52 , while translating, in the form of a slope on the airplane slope scale  56 , the target vertical speed, obtained at the measured height at each moment, by the sensor  32 . 
         [0122]    Then, once the end of flare is reached, the generating module  62  is able to keep the flare guidance symbol  64  at a constant distance from the horizon line  52 , corresponding to the desired target vertical speed value at the end of flare, allowing an appropriate touch down of the aircraft  12  on the landing strip  13 . 
         [0123]    The operation of the display system  10  according to an embodiment of the invention, upon the approach toward a landing strip  13 , will now be described in reference to  FIGS. 3 to 7 . 
         [0124]    Initially, the aircraft  12  descends toward the landing strip  13 . As illustrated by  FIG. 3 , the generating module  50  keeps the horizon line  52  in a non-deformed configuration, with no deformed region  70 . 
         [0125]    The generating module  54  creates the display of a slope scale  56  and the generating module  58  creates the display of speed vector symbol  60  whereof the vertical distance from the horizon line  52  reflects the airplane slope, on the slope scale  56 . 
         [0126]    Then, at a given distance from the landing strip  13 , the crew selects the targeted landing strip  13 . The calculating application  72  recovers topographical information in the runway database  46 . 
         [0127]    The topographical information recovered from a database for example includes the altitude at the runway threshold, the altitude at the end of the runway and the length of the runway. 
         [0128]    Based on topographical information recovered from the database  46 , the calculating software application  72  calculates a topographical slope from a database of the landing strip  13 . 
         [0129]    Based on the topographical slope from a database, the calculating application  72  determines the maximum height of the deformed region  70  relative to the rest  75  of the horizon line  52  and displays the deformed region  70  as illustrated in  FIG. 4 . 
         [0130]    During this first evolution phase, the height of the deformed region  70  relative to the rest of the horizon line  52  is constant. 
         [0131]    The height of the deformed region  70  is representative of the topographical slope from a database of the landing strip  13 . The deformed region  70  extends upward if the topographical slope is positive, and downward if the topographical slope is negative. 
         [0132]    The width of the deformed region  70  is slightly larger than that of the speed vector symbol  60 , as indicated above. The deformed region  70  remains centered on the speed vector symbol  60 . 
         [0133]    When the aircraft  12  reaches the landing strip  13 , or from a given altitude above the landing strip  13 , the sensor  33  measures, at each moment, the height of the aircraft  12  relative to the landing strip  13 . The airplane slope is also measured continuously by the sensor  32 . 
         [0134]    Based on this measured height and the airplane slope, the local topographical slope I of the runway visible in  FIG. 8  is then estimated by the calculating software application  72  using equations (1) and (2) above. 
         [0135]    The maximum height of the deformed region  70  is then calculated at each moment by the calculating module  72  to correspond to the value of the measured topographical slope of the landing strip on the slope scale  56  created by the generating module  54 . 
         [0136]    Thus, by viewing the deformed region, the pilot simply anticipates that the landing strip  13  is not horizontal and attempts his flare as a function of the actual topographical slope of the landing strip  13 , the value of which comes from tables in the first movement phase, and the value of which is measured in the second movement phase. 
         [0137]    In the case of the landing strip  13  having a positive topographical slope, this prevents the pilot from not increasing the vertical speed enough, which could lead to a hard landing. 
         [0138]    On the contrary, the pilot can stay at a given distance from the deformed region  70  of the horizon line  52  that corresponds to the apparent slope YR of the aircraft  12  relative to the landing strip  13 . 
         [0139]    In the case of a negative topographical slope of the landing strip  13 , this prevents the pilot from increasing the vertical speed excessively, which would cause a long landing and risk go around the runway. The safety of the landing is therefore increased. 
         [0140]    The display of a deformed region  70  on the artificial horizon line  52  does not modify the visual references of the pilot, unlike a shift of the entire artificial horizon line  52  based on the slope of the runway. 
         [0141]    For the pilot to perform the flare, he guides his speed vector relative to the deformed region  70  as he does for a non-deformed horizon line on a flat runway. In particular, the pilot advantageously places the speed vector symbol  60  below the deformed region  70  and gradually raises the speed vector symbol  60  relative to the deformed region  70  in order to place the symbol  60  at a predetermined distance from the deformed region corresponding to an end of flare target slope (for example approximately 1° below the deformed region  70  of the horizon line). 
         [0142]    The pilot can therefore anticipate the maneuver as on a flat runway, without losing references, whether he pilots directly or monitors the actions of an automatic pilot system. 
         [0143]    Furthermore, as illustrated by  FIG. 5 , to allow the pilot to anticipate reaching the beginning of flare maneuver position, the generating module  62  is advantageously able to display the flare guidance symbol  64 , here in the form of a cross, below the speed vector symbol  60  before the beginning of flare maneuver position and bring it vertically closer to the speed vector symbol  60  until the beginning of flare maneuver position. 
         [0144]    The beginning of flare position is then determined by the generating module  62  as a function of a piece of topographical slope information from a database of the landing strip  13 , determined using the database of landing strips  46 , by the calculating application  72  as described above. 
         [0145]    The beginning of flare maneuver position is further determined taking into account the airplane slope γ measured by the sensor  32 . 
         [0146]    In reference to  FIG. 6 , the generating module  62  next signals that the beginning of flare maneuver position has been reached by placing the flare guidance symbol  64  horizontally in register with the speed vector symbol  60 . 
         [0147]    At the beginning of flare maneuver height, the flare guidance symbol  64  is positioned at the same horizontal level as the speed vector symbol  60 , horizontally coinciding with the speed vector symbol  64 , preferably in the receiving zone  110  of the speed vector symbol embodied here by a circle defining the desired slope of the aircraft. 
         [0148]    Next, the generating module  62  commands the approach of the flare guidance symbol  64  toward the horizon line  52 . 
         [0149]    The approach follows the predetermined control law, corresponding to a vertical speed variation as a function of the measured height relative to the landing strip  13 , to go from a first target vertical speed at the beginning of flare maneuver position to a second target vertical speed greater than the first target vertical speed at the end of flare. 
         [0150]    The generating module  62  determines, at each moment, the second target vertical speed as a function of the topographical slope of the landing strip  13 . The topographical slope is initially estimated using topographical information from a database, then is measured from data received from the sensors  32  and  33 , as indicated above. 
         [0151]    At each moment, the generating module  64  receives a height datum measured using the sensor  33 , and determines the vertical distance separating the flare guidance symbol  64  from the horizon line  52  based on the control law. 
         [0152]    The flare guidance symbol  64  therefore comes gradually closer to the horizon line  52 , clearly indicating to the pilot that the flare must be done, and proposing a flare strategy to the pilot on which he must match the speed vector symbol  60 . 
         [0153]    The pilot or the automatic pilot system  29  may then adopt the proposed flare strategy by horizontally aligning the speed vector symbol  60  with the flare guidance symbol  64 . 
         [0154]    Once the end of flare is achieved, the generating module  62  keeps a flare guidance symbol  64  at a second constant distance from the horizon line  52 . 
         [0155]    The presence of a flare guidance symbol  64  helps the pilot determine the appropriate moment to initiate flare, which simplifies this task at the end of landing. 
         [0156]    This moment is not only determined as a function of the measured airplane slope, but also as a function of a topographical slope of the landing strip  13 , to account for the apparent slope between the aircraft  12  and the landing strip  13 . 
         [0157]    The vertical movement of this symbol  64  is also useful to determine a desired vertical speed profile during flare. 
         [0158]    In one alternative, the flare guidance symbol  64  is displayed only when the data from the sensors of the system  30  is used to determine the measured slope of the runway  13 . 
         [0159]    The flare guidance symbol  64  is then moved at each moment as a function of the control law, as described above. 
         [0160]    In embodiments of the invention described above, the topographical slope of the landing strip being taken into account as of the beginning of flare, this makes it possible to implement a flare maneuver with dynamic continuity and avoids a sharp increase in the command to pull up in case of a positive slope. 
         [0161]    In one alternative, the database  46  contains a topographical slope profile along the landing strip  13 , defining, for each point of the runway, a piece of topographical slope information from a database. 
         [0162]    The generating module  50  is able to calculate the height of the deformed region as a function of the topographical slope information from a database corresponding to each point of the landing strip  13 , when the aircraft  12  moves above the landing strip  13 . In one alternative, the generating module  50  is able to keep the horizon line  52  without a deformed region  70  as long as measured topographical slope information is not obtained reliably from the system of measuring sensors  30 . 
         [0163]    In an alternative, the generating module  50  is able to display on the horizon line  52  without deformation. The display of a flare guidance symbol  64  remains identical.